# Why U-brakes?



## bikerboy (Jan 13, 2004)

I never understood the reason bike manufacturers fitted mountain bikes with chainstay-mounted U-brakes back in the late 80s. I was never too impressed with one on my Diamondback Apex because it seems to have a lot of flex. Somebody please educate me on possible reason for thse brakes.


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## uphiller (Jan 13, 2004)

bikerboy said:


> I never understood the reason bike manufacturers fitted mountain bikes with chainstay-mounted U-brakes back in the late 80s. I was never too impressed with one on my Diamondback Apex because it seems to have a lot of flex. Somebody please educate me on possible reason for thse brakes.


-a couple of reasons. one, the u-brake stud is marginally farther away from the middle of the tube to which it is mounted, than a canti stud. this has the effect of (marginally) reducing brake stud flex.
-u-brakes also stick out less far from the frame than even the last generation of cantis, and indeed far, far less than the medium profile cantis of the late 80's, with whom they were contemporary. this allowed them to be mounted on the chainstay. the chainstays are generally stiffer than the seatstays, again, reducing flex.
-à propos low-profile, it's possible with most u-brakes to get a 90deg angle between the straddle cable and the calipers, and still not have the brake stick out one mm from the frame. this can't be done with cantis, which always stick out at least some from the frame. 
problems: 
-as the pads wear, the brake pads arc close and closer to the tire, rather than farther and farther from it like with cantilever stud-mounted brakes. this leads to sidewall cuts if you don't watch for pad wear enough.
-weight: an xt u-brake is significantly chunkier than a cantilever of similar construction. the figure of 90g a wheel sticks in my head for some reason.
having ridden a set of xt u-brakes with good pads and levers, setup with fresh, well-cut cables and quality rims, i can say they are as good or better as any cantilever out there. just heavy, that's all.


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## Tracerboy (Oct 13, 2002)

Same reason they gave us biopace: they were stoned.


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## bikerboy (Jan 13, 2004)

*What the?*



wooglin-at-home said:


> Same reason they gave us biopace: they were stoned.


Now what does everybody have against biopace, lol. I happen to love my biopace cranks.


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## Tracerboy (Oct 13, 2002)

bikerboy said:


> Now what does everybody have against biopace, lol. I happen to love my biopace cranks.


Oops. Figures I'd say that to the one person who likes them.


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## laffeaux (Jan 4, 2004)

bikerboy said:


> Now what does everybody have against biopace, lol. I happen to love my biopace cranks.


I'm pretty indifferent about them. I'd not go out of my way to buy bio-pace rings, but if they were on a bike I'd still ride it. I'm not sure that I can actually feel much (or any) difference compared to round rings.


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## DeeEight (Jan 13, 2004)

*blame richard cunningham...*

for the under chainstay position. He used that spot on one of his designs and every copycap big brand designer did the same.

Since chainstays are usually a larger diameter tube, and being close to the BB shell, widely supported and very laterally stiff at that point, the U-brake isn't going to flex the stays apart. Also since the U-brake arms are longer than cantilever arms, more leverage and more power.

Great in practice unless you also rely on normal tire clearance frames and ride where there's a lot of mud. RC's design was based around 2.5" tires with lots of space to spare as memory serves, and didn't have a mud issue. All the copycats were basing around 2.1" tires with barely any mud clearance to spare.


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## flyingsuperpetis (Jan 16, 2004)

*Cunninghams*

To clairfy:

Charlie Cunningham:
- One of the repack gang
- Major role in the development of the clunkers, including braking standards
- Developed some of the first mtb-specific gear, including rollercams for what became WTB
- Built some of the first successful aluminum bikes, under the name "Cunningham" (see related threads)

Richard Cunningham:
- The man behind Mantis bikes
- Developed Elevated Chainstays for more tire clearance & no chainsuck
- Developed the idea of stiff front end, forgiving rear by utilizing two different materials in one frame
- Built the first aluminum monocoque frames
- Sold company to work for Mountain Bike Action.

Charlie is your man.


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## colker1 (Jan 6, 2004)

[
- Sold company to work for Mountain Bike Action.

why trade such a brilliant career as an enginneer for mountain bike action? his bikes are far more enjoyable than any number of MBA... do they pay that well?


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## Fillet-brazed (Jan 13, 2004)

flyingsuperpetis said:


> To clairfy:
> 
> Charlie Cunningham:
> - One of the repack gang
> ...


Actually Charlie was never a "repack guy". He was never involved with that. Had nothing really to do with klunkers....


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## flyingsuperpetis (Jan 16, 2004)

That's a subject of much debate. Some say it was more of a hostile buyout, some say it was an act of desperation, and that he's still substantially less than pleased about the whole thing. Some say it was fulfilling a lifelong dream of being a writer & an amateur airplane enthusiast. I don't think anybody knows except Richard, who hasn't come straight out and said either way.


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## flyingsuperpetis (Jan 16, 2004)

Woah! I could be wrong on that one. I was pretty certain he was one of Kellys friends. Well, certain up till now, anyway...

I'll have to check to see where I got that idea. I think it was an interview with Joe Breeze...


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> for the under chainstay position. He used that spot on one of his designs and every copycap big brand designer did the same.
> 
> Since chainstays are usually a larger diameter tube, and being close to the BB shell, widely supported and very laterally stiff at that point, the U-brake isn't going to flex the stays apart. Also since the U-brake arms are longer than cantilever arms, more leverage and more power.
> 
> Great in practice unless you also rely on normal tire clearance frames and ride where there's a lot of mud. RC's design was based around 2.5" tires with lots of space to spare as memory serves, and didn't have a mud issue. All the copycats were basing around 2.1" tires with barely any mud clearance to spare.


I think the leverage of a canti and a U brake are quite similar. Yes, the u brakes have longer arms but with the arm being "L" shaped only a portion of that arm gets used for leverage. They use canti brake levers and have about the same pad clearance as a standard canti. No more leverage as far as I can tell........ The main advantage is just a stiffer mounting location. I have some Ritcheys with under the chain stay brakes and its amazing how small the seatstay tubing gets when there are no cantilevers up there. So, some or maybe all of that weight gained by the U brake can be recovered by wimpy seatstays.... That said, Id take a cantilever anyday.


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## halaburt (Jan 13, 2004)

*Huge variations in brand/setup also impact reputation..*

I find that most who don't like/understand U-Brakes and Rollercams have only experienced them in their worst (usually Shimano) incarnations and/or on cheaper bikes where the setup wasn't particularly good.

Conversely, most who have experienced them in their very best incarnations (WTB Toggle/Roller-Cams and the IRD Progressive/Rotary) swear they are the best braking they've ever had.

I'm in the latter camp 

-Geoff


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## Fillet-brazed (Jan 13, 2004)

flyingsuperpetis said:


> To clairfy:
> 
> Charlie Cunningham:
> - One of the repack gang
> ...


Its funny, if you read the old magazines, in the late 80s anyway, aluminum is almost always billed as being the softer riding material over steel. Which I think should be true as it is much less dense than steel. Quite the opposite of what is written nowadays.

Personally, in vertical compliance, I think the differences are indetectible in two standard double triangle frames. Especially on a MTB. The tires, dirt, long seatpost, saddle, etc, will make a much more "feelable" difference in sharp hits. A standard rear triangle is such a stout structure that it doesnt give hardly at all no matter if its ti, al, or steel.

Torsion and lateral stiffness are completely different though. Big tubes (which are almost always aluminum) are stiff.

Market hype has really shaped a lot of opinions....

Then again, thats just my opinion!


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> I think the leverage of a canti and a U brake are quite similar. Yes, the u brakes have longer arms but with the arm being "L" shaped only a portion of that arm gets used for leverage.


The shape of the arm doesn't make a difference. The leverage is being applied to one end of the lever arm, pivots around a pivot point, and brings the pad to contact the rim. The distance
between pulling point of the lever arm and pivot is greater with U-brakes than with cantilevers. This is also why basically NOBODY (at least no major brand concerned with lawsuits - remember the era, we got lawyer tabs on forks at the same time, and safety tabs to catch straddle cables in case the brake lever cable snapped in usage) used U-brakes as front brakes, as combined with high-leverage canti-brake levers, 1-finger endo's would be a common occurence.


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> Its funny, if you read the old magazines, in the late 80s anyway, aluminum is almost always billed as being the softer riding material over steel. Which I think should be true as it is much less dense than steel. Quite the opposite of what is written nowadays.


That's because Al frames of the late 80s DIDN'T use the super large diameter tubing that Al frames did by the mid to late 90s.

Case in point, 1991 Rocky Mountain Experience frame, 35mm diameter TT, 40mm DT, 32mm ST, 22mm CS and the seatstays taper from 26mm by the welded monostay end to 20mm at the dropouts (they're about 24mm where the brake studs are).

My 1996 Eclipse hardtail frame (eclipse is a canadian brand, the early frames like this one made by Devinci under contract), has a 39mm TT, 45mm DT, 32mm ST (in fact, both frames use the same 27.0mm seatpost size), ovalized S-bend CS which are 29mm high and 16mm wide, S-bend ST 22mm.

The Stratos is straight gauge 7005T6, the Eclipse is butted 6061T6. A 16" Stratos frame
is about 4.5 pounds. A 16" eclipse (which adds a replaceable dropout, and an adjustable anti chainsuck plate on the right CS, two features the stratos lacks) is 3.4 pounds. The eclipse is also the harsher riding frame.


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> The shape of the arm doesn't make a difference. The leverage is being applied to one end of the lever arm, pivots around a pivot point, and brings the pad to contact the rim. The distance
> between pulling point of the lever arm and pivot is greater with U-brakes than with cantilevers. This is also why basically NOBODY (at least no major brand concerned with lawsuits - remember the era, we got lawyer tabs on forks at the same time, and safety tabs to catch straddle cables in case the brake lever cable snapped in usage) used U-brakes as front brakes, as combined with high-leverage canti-brake levers, 1-finger endo's would be a common occurence.


Well the leverage would be measured by the distance from the pivot to the cable attachment point. I guess depeding on what direction the straddle cable was pulling this could vary slightly with the 90 degree bend there... Usually they seemed to pull pretty straight. Also if they were higher leverage than a canti wouldnt they ride real close to the rim and be mushy? They always seemed to be pretty firm at the brake lever and have really good pad clearance which would tend to imply lower leverage.

I never found the brake power of a U brake to be overwhelming. I thought it was purely invented as a brake to be slim enough to fit under the chainstays like a roller cam, not as a way to increase braking power over the canti. Ive always felt that a U brake can feel pretty good, but my cantis were always tuneable to a much more powerful state.

Roller cams are a different story, I have yet to get one of these at full power yet. I have no verdict yet on them.

Why did the roller cam and U brake die? If they are so great, it seems like they should have taken over and the cantilever would be put to rest. But instead it was the other way around. Any theories as to why this happened?

The canti ruled the market all the way until 96 I think.....


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> That's because Al frames of the late 80s DIDN'T use the super large diameter tubing that Al frames did by the mid to late 90s.
> 
> Case in point, 1991 Rocky Mountain Experience frame, 35mm diameter TT, 40mm DT, 32mm ST, 22mm CS and the seatstays taper from 26mm by the welded monostay end to 20mm at the dropouts (they're about 24mm where the brake studs are).
> 
> ...


That makes sense. What about Cannondale, Klein, etc. Are they alot smaller in the early years?


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> Well the leverage would be measured by the distance from the pivot to the cable attachment point. I guess depeding on what direction the straddle cable was pulling this could vary slightly with the 90 degree bend there... Usually they seemed to pull pretty straight. Also if they were higher leverage than a canti wouldnt they ride real close to the rim and be mushy? They always seemed to be pretty firm at the brake lever and have really good pad clearance which would tend to imply lower leverage.


They died (rollers and U's) because of the weight, and the need for a cable housing stop same as cantilevers. With space at a premium on long travel suspension designs and goofy cable routing neccessary, anything requiring a cablestop 2-4" above the center of the brake arms was an inconvenience to bike designers.

As to why they had firm lever feels. Bare in mind that the original shimano SLR 2-finger brake levers (and these were most often spec'ed with U-brakes during their height of popularity) pulled 22mm of brake cable. Shimano recommended (when they brought out v-brakes) cable pull of 23 to 26mm for a firm lever feel. Most cantilever brake levers ran from 13 to 18mm of cable pull. DiaCompe's MX-99 levers, which are a 2-finger lever mainly used by BMX bikers (which also used rollercams and U-brakes), pulled 20mm of cable. A Diacompe SS-5 lever pulls only 16mm in comparison. Shimano's servowave levers with their cam action that increased leverage/reduced cable pull thru the lever travel, netted 17mm total cable pull, but initially move the same amount of cable as SLR levers (to get the pads to contact the rim). Avid Ultimate levers with the speed-dial leverage adjustment
was an early 90s product, again, aimed at adjusting the brake power to a user's liking. They adjusted from about 12-18mm of cable pull.

I still own SLR levers, Servowave levers (including the ones with the windows), SS-5 Mk2s, MX-99s, Suntour XC-Pro levers, and many others from the canti/u/servo era.

Then for other goofy brakes, there were the Scott-Pedersen/Suntour Self-Energizing cantilever brakes and powercam brakes.


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> They died (rollers and U's) because of the weight, and the need for a cable housing stop same as cantilevers. With space at a premium on long travel suspension designs and goofy cable routing neccessary, anything requiring a cablestop 2-4" above the center of the brake arms was an inconvenience to bike designers.
> 
> As to why they had firm lever feels. Bare in mind that the original shimano SLR 2-finger brake levers (and these were most often spec'ed with U-brakes during their height of popularity) pulled 22mm of brake cable. Shimano recommended (when they brought out v-brakes) cable pull of 23 to 26mm for a firm lever feel. Most cantilever brake levers ran from 13 to 18mm of cable pull. DiaCompe's MX-99 levers, which are a 2-finger lever mainly used by BMX bikers (which also used rollercams and U-brakes), pulled 20mm of cable. A Diacompe SS-5 lever pulls only 16mm in comparison. Shimano's servowave levers with their cam action that increased leverage/reduced cable pull thru the lever travel, netted 17mm total cable pull, but initially move the same amount of cable as SLR levers (to get the pads to contact the rim). Avid Ultimate levers with the speed-dial leverage adjustment
> was an early 90s product, again, aimed at adjusting the brake power to a user's liking. They adjusted from about 12-18mm of cable pull.
> ...


Also, it was generally a stouter place to mount a brake adding to its firmer feel.

Ok, but how is the big pad clearance explained? It seemed to have more than standard Shimano cantis......


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> Also, it was generally a stouter place to mount a brake adding to its firmer feel.
> 
> Ok, but how is the big pad clearance explained? It seemed to have more than standard Shimano cantis......


Depends on the user setting up the brake. I've set brakes up with little clearance and a lot of clearance with the same lever feel. Its easier to adjust U-brakes since you don't have to take the casing of the tire into consideration when setting the angle your pads arc thru as they get closer to the rim sidewall. Fat tires on skinny rims bulge out more, and present setup difficulties with cantilevers.

My front westpine scissors brake has loads of tire clearance and a firmer lever feel than my rear westpine t.a.c. brake (with same levers and pads), because I didn't have to make any compromises on the pad arc path, and the leverage advantage of the scissors cam.


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:



> Depends on the user setting up the brake. I've set brakes up with little clearance and a lot of clearance with the same lever feel. Its easier to adjust U-brakes since you don't have to take the casing of the tire into consideration when setting the angle your pads arc thru as they get closer to the rim sidewall. Fat tires on skinny rims bulge out more, and present setup difficulties with cantilevers.
> 
> My front westpine scissors brake has loads of tire clearance and a firmer lever feel than my rear westpine t.a.c. brake (with same levers and pads), because I didn't have to make any compromises on the pad arc path, and the leverage advantage of the scissors cam.


So the U brake has the same leverage ratio as a standard canti?

The same levers are used for either brake, and the same or more pad clearance with a U brake...... Based on that it should be equal or less leverage for a U brake. Did I miss something?


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## Shayne (Jan 14, 2004)

Fillet-brazed said:


> So the U brake has the same leverage ratio as a standard canti?
> 
> The same levers are used for either brake, and the same or more pad clearance with a U brake...... Based on that it should be equal or less leverage for a U brake. Did I miss something?


Well the way I see it if you have more pad clearance and use the same pull levers then less cable must be needed to be pulled to actuate the brake therefore it has more leverage than a standard canti.


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## flyingsuperpetis (Jan 16, 2004)

Hmm, that's a great post, FB! You bring up some really great points.

I think the big thing is, in the 80's "alt materials" like alum & even carbon & ti were essentially being used as substitute materials, within a refined structure engineered for steel. Alan & Vitus come to mind. Aluminum is indeed much softer, and weaker than steel. What RC & a few others picked up on (early) was that alum, for the same weight, can produce a much larger diameter tube & a more rigid frame.

While working for a certain local company some years ago, we happened to buy a well known and popular SantaCruz framebuilder. One of the brand-transitioning projects I was involved with, was testing & analysis of their old frames, as we'd soon be taking over their production. Among other results, we watched in amazement as the BB's deflected vertically almost an inch and three quarters before reaching yeild. Just over an inch under normal conditions, which approximated a 200lb rider on a railroadtrack at 15mph. That is one hell of a lot of give in a rear end, and was deemed unsafe. By contrast, our house tubesets built into the the same frame configuration eventually yeilded at an inch, and about 3/8 at normal. The Merlin, Spectrum & Litespeeds we tested at the time were like rubber bands, but could handle a seemingly infinite cycle duration. Alum's yeild stregth isn't far off from its ultimate strength, and it's elongation capacity being short as well means your best bet is to keep the structure as well away from yeild as possible, with large large od's & sections. What a pain, that aluminum. Still, it's the lightest, next to the fiendish quagmire of engineering out a carbon lam, plus, it's cheap, and looks cool, so marketing is generally pushing for it... Alum it is.

Really though, in the end, you're right. While all these materials have quite different mods of elasticity, and therefore will offer a different feel, everything else that separates an ass from a rock plays a proportional part. Notably, spoke count & tension, seatpost length & material, and so on.

Basic stuff, yeah, I know, but this is probably the most thought I'll put into a posting online. I have work to do too! Marketing has definitely sold a lot of rotten mackerel to a lot of people with aquariums, and especially to people with bicycles looking for a fish.

Books keep people from falling for newspapers & magazines.


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## flyingsuperpetis (Jan 16, 2004)

hmmm... suddenly I'm very off topic...


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## Fillet-brazed (Jan 13, 2004)

flyingsuperpetis said:


> Hmm, that's a great post, FB! You bring up some really great points.
> 
> I think the big thing is, in the 80's "alt materials" like alum & even carbon & ti were essentially being used as substitute materials, within a refined structure engineered for steel. Alan & Vitus come to mind. Aluminum is indeed much softer, and weaker than steel. What RC & a few others picked up on (early) was that alum, for the same weight, can produce a much larger diameter tube & a more rigid frame.
> 
> ...


Ya, the Vitus' and Alans are a different story, but even for Kleins they were saying it had a softer ride than a Salsa I think it was. Its been a while. I just found it interesting as its quite the opposite in magazines nowadays.

Anyway, about that deflection, thats a lot of movement. So, where was the force exerted? Did you pull down on the bb, or push down on the seat tube? Interesting. Youd think with that much movement your paint would start cracking off since just the slightest bend and it crackles right off. I guess its distributed thoughout the frame.

Anyway you might enjoy this German study on fatigue resistance on dif materials. The results are not what most would expect. http://sheldonbrown.com/rinard/EFBe/frame_fatigue_test.htm


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## Fillet-brazed (Jan 13, 2004)

Shayne said:


> Well the way I see it if you have more pad clearance and use the same pull levers then less cable must be needed to be pulled to actuate the brake therefore it has more leverage than a standard canti.


Well, think of it this way. Imagine V brakes with arms that are say 3 inches longer than standard with just a standard V brake lever. This would be very high leverage and you wouldnt get hardly any pad clearance. It would be mushy because you could literally squish the pads by squeezing the brake lever.

On the other hand, imagine V brakes with arms 3" shorter than standard. Of course now you'll have to have the tire off, but anyway, this would be low leverage with a very firm feel at the lever and if your levers pulled 24mm of cable you would have 12mm of clearance at the brake pad and rim on each side.

So, lots of pad clearance is usually an indicator of low amount of leverage. Did that make any sense?


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## Shayne (Jan 14, 2004)

Wow! I would never expect anyone to think that a Klein gave a softer ride that a Salsa. The 1990 Klein Attitude I had a while back was by far the harshest riding MTB I have ever been on. I had a Salsa of the same vintage and it was hands down a smoother ride. A 1987 Mountain Klein that I've ridden deffinately wasn't as harsh as current aluminum hardtails but still didn't have a ride nearly as nice as steel.


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## Fillet-brazed (Jan 13, 2004)

Shayne said:


> Wow! I would never expect anyone to think that a Klein gave a softer ride that a Salsa. The 1990 Klein Attitude I had a while back was by far the harshest riding MTB I have ever been on. I had a Salsa of the same vintage and it was hands down a smoother ride. A 1987 Mountain Klein that I've ridden deffinately wasn't as harsh as current aluminum hardtails but still didn't have a ride nearly as nice as steel.


If I ever come across the review I'll post it. It was a review of a few really nice bikes made of aluminum, steel, and ti, and I think they even had the CR-7 in there as well which was conceived by Mantis and half steel and alu. They were comparing the ride characteristics of the 4 materials at Moab. Interesting article. Ive seen similar stuff written as well back then. It was just thought of as a softer riding material then before market hype took over I guess. Of course these are all just human impressions and opinions. I heard some Germans did a study on vertical compliance and the dif between materials was very small. Thats just vertical, not lateral or torsional.

The 1990 Attitude, for me, felt very stout and rigid, but I felt (could be off) that at speed and when encountering hard hits that the fat but thin-walled fork actually felt softer than a steel rigid fork.... Again, its tough to really tell. Even while on the same bike some days it feels soft and some days harsh. I think a lot of it is mental, or maybe Im not very sensitive to that kind of thing........


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## Shayne (Jan 14, 2004)

*Sure that makes sense for "V brakes" but...*

On U brakes the pad is on the other side of the pivot than the rest of the arm. So everything is basically the opposite.


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## Fillet-brazed (Jan 13, 2004)

Shayne said:


> On U brakes the pad is on the other side of the pivot than the rest of the arm. So everything is basically the opposite.


That wouldnt change a thing. Its still the exact same principle.


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## Fillet-brazed (Jan 13, 2004)

Shayne said:


> On U brakes the pad is on the other side of the pivot than the rest of the arm. So everything is basically the opposite.


You just reminded me of something. On the U brakes arm, if you measure it from the pivot to the cable attachment point you get X. Ok now measure from the pivot to the pad you get Y. Because Y is on the other side of the pivot you have to subtract that amount from X to get the actual length of the arm. So Dee Eight was saying its a longer arm, well it is, but you have to subract out the other part to get the true amount of leverage.

I still say the leverage of a U brake is right in the same ballpark of a canti. Otherwise they would need a different brake lever to feel/work right....


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> So the U brake has the same leverage ratio as a standard canti?
> 
> The same levers are used for either brake, and the same or more pad clearance with a U brake...... Based on that it should be equal or less leverage for a U brake. Did I miss something?


The same levers are used because there's a straddle cable and yoke (which is acting as another lever in the equation). V-brakes don't have this extra lever and so required different brake levers. Powercam brakes have an actual steel cam (and they made different profile cams too) running between two pulley wheels on the brake arms to allow for different pad clearances and lever feels. The leverages are NOT the same between cantilever arms, u-brake arms, and powercam arms.

In fact, until about 1995, I can't recall ANY magazine or manufacturer ever testing how much cable pull different brake levers had.


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> If I ever come across the review I'll post it. It was a review of a few really nice bikes made of aluminum, steel, and ti, and I think they even had the CR-7 in there


Fisher had the Procaliber is oversized prestige steel, the supercaliber in oversized aluminium, and the CR-7 with a front end that was aluminium and a back end of prestige steel.

ALL in the same model year, using sales and consumers as R&D dummies. Its little wonder the company went bust and got bought out by Trek.


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> You just reminded me of something. On the U brakes arm, if you measure it from the pivot to the cable attachment point you get X. Ok now measure from the pivot to the pad you get Y. Because Y is on the other side of the pivot you have to subtract that amount from X to get the actual length of the arm. So Dee Eight was saying its a longer arm, well it is, but you have to subract out the other part to get the true amount of leverage. still say the leverage of a U brake is right in the same ballpark of a canti. Otherwise they would need a different brake lever to feel/work right....


Actually its not subtraction, its DIVISION.

You divide the distance of pivot to pad, into the distance of pivot to cable fixing point.

God, don't they teach basic physics of levers anymore in school ?!?


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## flyingsuperpetis (Jan 16, 2004)

*zing...*

These were the pics off the old wtb website. I have a pair of suntours rollercams on a 24"/26" cannondale. Love em to peices. The wtbs I've felt were much smoother & lighter. You have to do this weird cable trick and ditch the cam to get em mounted on a trimble, on account of the tight fore/aft clearance & then the actuation ratio winds up matching a v brake... so I tried like hell to find a set of togglecams starting in 2000. One year too late. Everybody had some in 1999, no one's had em since. Mountain Transport was a little offshoot between Rick Hunter, Paul Price, Eric Koski, and Someone else at WTB... they were trying to figure out a way to bring the rollercam back for a little short-run, but as far as I could tell it never happened, and I needed the bloody toggle anyway. Wound up going discs in the end... Here are the pics...

More on the testing bit of this thread when I have the time to write it all out... might be a bit, as there's no real quick & easy way to get into it all.


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> Actually its not subtraction, its DIVISION.
> 
> You divide the distance of pivot to pad, into the distance of pivot to cable fixing point.
> 
> God, don't they teach basic physics of levers anymore in school ?!?


No, you have to subtract to get the actual length of the leverage arm. And yes, its been a while since any school took place here.....


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> No, you have to subtract to get the actual length of the leverage arm. And yes, its been a while since any school took place here.....


No you don't have to subtract. Not with U-brakes lever arms or powercam brake lever arms and not with canti brake lever arms either if you know lever theory correctly (and it appears at this time, that you do not).


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## flyingsuperpetis (Jan 16, 2004)

*But I'm sure he's a swell guy.*



DeeEight said:


> Fisher had the Procaliber is oversized prestige steel, the supercaliber in oversized aluminium, and the CR-7 with a front end that was aluminium and a back end of prestige steel.
> 
> ALL in the same model year, using sales and consumers as R&D dummies. Its little wonder the company went bust and got bought out by Trek.


Yep, that's what happens when Gary tries to design a product line himself... The procaliber was originally a Ritchey (later taiwanesified), the CR-7 was a Mantis xcr copy (taiwanesified), and the SuperCaliber (which I have one of), was pretty much the standard OS alum frame everyone was having made in [you gessed it] at the time. All Fisher really had to do was make sure marketing didn't blow the budget, and accounting funnelled the money into the right places. Couldn't even do that right, almost lost the whole works twice, finally did lose it completely, and after some time, got EXTREMELY lucky and was picked up on the cheap. I could go on...

Mostly, I only care enough to wonder who built his Klunker...

flame away...


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## flyingsuperpetis (Jan 16, 2004)

*add/divide*

Ah, you guys are talking about two different things. You're both right within your own arguments.


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## DeeEight (Jan 13, 2004)

MBA a few years ago, posted a picture from I think it was the 1974 or 75 US Cyclocross championships in california, and there was two groups of riders. On one side there was 
tom ritchey, joe breeze, and gary fisher, ALL on cyclocross bikes. And they were looking back at these other riders all on klunkers with multi-gears, canti brakes and fat tires. 

So its pretty safe to say that Tom, joe and Gary DIDN''T invent mountain bikes in any way, shape, or form.


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## Fillet-brazed (Jan 13, 2004)

Heres a direct quote from you above: "Also since the U-brake arms are longer than cantilever arms, more leverage and more power."

You have to subtract. Im not talking about the theory of leverage. Im just talking about the length of the leverage arm, like you brought up and we were discussing. To get the effective/actual length you have to subtract it. 

Yes, to find the leverage ratio you would divide the aforemention X by Y. 

Just the leverage arm. Thats all I was getting at.....

Why dont you calculate the leverage ratio for us?


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## Fillet-brazed (Jan 13, 2004)

flyingsuperpetis said:


> Ah, you guys are talking about two different things. You're both right within your own arguments.


LOL. Im glad someone saw it!!!!!!!!!!!! Funny stuff indeed.


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> MBA a few years ago, posted a picture from I think it was the 1974 or 75 US Cyclocross championships in california, and there was two groups of riders. On one side there was
> tom ritchey, joe breeze, and gary fisher, ALL on cyclocross bikes. And they were looking back at these other riders all on klunkers with multi-gears, canti brakes and fat tires.
> 
> So its pretty safe to say that Tom, joe and Gary DIDN''T invent mountain bikes in any way, shape, or form.


It was a bunch of guys from Cupertino that showed Gary the light. They raced cross on their klunkers and Gary and friends were blown away.


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> Heres a direct quote from you above: "Also since the U-brake arms are longer than cantilever arms, more leverage and more power."
> 
> You have to subtract. Im not talking about the theory of leverage. Im just talking about the length of the leverage arm, like you brought up and we were discussing. To get the effective/actual length you have to subtract it. THEN, you can proceed to calculate the leverage ratio with your division. Right?
> 
> ...


And you completely missread my reply...

What part of cable fixing point to pivot, divided by pivot to pad point can't you understand? Where is the subtraction needed there to calculate the leverage ratio for the u-brake/powercam arm? You have a set distance on either side of a pivot, no subtraction is needed, the fulcrum's in between the two ends.

And do you want the leverage ratio for a complete system? Gonna need to work out straddle cable/yoke angles for that. Brushed up on your sine and cosine math lately?


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## flyingsuperpetis (Jan 16, 2004)

That's pretty cool, I'd love to see that photo. I had an article where Joe B. talked about the day the canyonites showed up at a race with their ballooners, and caught the eye of Joe, Kelly, and Tom. In every tale of this history that I've heard (except Fishers), Gary usually comes in later, and is involved more as a roaming salesman than anything...

Did they invent em? Did anyone? Yes, lots of people did. What got used, though, and turned into all this, was what the screwballs on that mountain were riding, and Joe, Tom, and more notably a few others developed and improved upon, that GF imitated, and pawned off as his own innovation, before a company pulled him out of the dirt, and took over that job for him...


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> And you completely missread my reply...
> 
> What part of cable fixing point to pivot, divided by pivot to pad point can't you understand? Where is the subtraction needed there to calculate the leverage ratio for the u-brake/powercam arm? You have a set distance on either side of a pivot, no subtraction is needed, the fulcrum's in between the two ends.
> 
> And do you want the leverage ratio for a complete system? Gonna need to work out straddle cable/yoke angles for that. Brushed up on your sine and cosine math lately?


LOL! Reread my post. I was not trying to find the leverage ratio. Ever. I was trying to figure out the length of the leverage arm compared to the cantis arm. Thats all.

Yes, to figure out the whole system would be too involved for me with the straddle cable angles involved. Im no mathemetician. I guess my whole point is the U brake arm is not as long as we think. To get the true/effective/actual length, y has to be subtracted from x. Again, thats not to get the leverage ratio, just to get the length of the arm. Comprende?

LOL. This forum is not good for my production during the day!


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> subtracted from x. Again, thats not to get the leverage ratio, just to get the length of the arm. Comprende?
> 
> !


and the length of the U-brake lever arm is the cable fixing point to the pivot point !! What of this can't you understand?


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## flyingsuperpetis (Jan 16, 2004)

HAHAHA WOW! Now I'm confused! It's been a long day, I've got parts to pick up from the machinist! 

Waaaaaaaaaaaaaaaaaaaaaaaaaaaaahoo!!!!!!!!!!!!!!!!!!!!!!!!!!!!

have fun kiddos!


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> and the length of the U-brake lever arm is the cable fixing point to the pivot point !! What of this can't you understand?


Ok. Let me explain.

This might be all my fault. When you said the U brake has a longer leverage arm, I first was envisioning the whole arm from the brake pad to the cable fixing point. It did seem like quite a long arm that way. But that is incorrect because the pad is on the other side of the pivot unlike a cantilever. Did that make sense? My brain is starting to hurt now!

I need to draw it out. I need a white board.

At anyrate, I would bet that the leverage of a U brake is very similar to that of a Shimano canti. Thats my whole point.

You could test this by pulling 10mm of cable and comparing the distance the pads travel with that of a canti if you really wanted to find out.


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> Ok. Let me explain.
> 
> This might be all my fault. When you said the U brake has a longer leverage arm, I first was envisioning the whole arm from the brake pad to the cable fixing point. It did seem like quite a long arm that way. But that is incorrect because the pad is on the other side of the pivot unlike a cantilever. Did that make sense? My brain is starting to hurt now!
> 
> ...


Except that only works for identical straddle yoke geometries. Hard to achieve for a test between two. Much easier to measure the arms. I happen to have bikes with both 1991 Deore DX low-profile canti's and Deore XT U-brakes.

U-brake... 
Cable fixing bolt to pivot center 90mm (straight line), 115mm (actual arm length)
pivot center to pad center 40mm

So a leverage ratio depending on how you'd wanna measure it, 2.25 to 2.875 to 1.

Canti...
Cable fixing bolt to pivot center 56mm
pivot center to pad center 28mm

2:1 leverage ratio

Oh, and for comparison...
DX V-brake (that's the M600X series)...
Cable fixing bolt to pivot center 105mm
pivot center to pad center 33mm

3.18 to 1.

Now bare in mind, the V-brake levers have a lower leverage ratio and no additional leverage effect from straddle cable/yoke geometry. Also as others have mentioned, its far easier to adjust U-brake straddle/yoke angles for optimum 90 degree settings without having the brake arms kicked out at unusual angles (which affects heel clearance on most frames),, and the arms have more leverage to begin with. Also all the multiples of leverage are cummulative...

2.25x (for U-brake arm), 4x for a lever and 1.1x for a straddle angle (as an example) = 9.9 total.

2.0x (for canti arm), 4x for same lever and 1.1x for same straddle angle = 8.8 total. So the U's have a slight but measurable edge. The biggest reason for them going away will always be the weight, and being cursed with run on the chainstays by most designers (GT sensibly put them on the seatstays for most models, as did Rocky Mountain).


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## bikerboy (Jan 13, 2004)

Wow, look what I started. Can somebody tell me what kinda pads I need for a U-brake?


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## Fillet-brazed (Jan 13, 2004)

bikerboy said:


> Wow, look what I started. Can somebody tell me what kinda pads I need for a U-brake?


Aztecs work well on U brakes. Is that what youre asking?? U brakes use a threaded post unlike a cantilever pad.


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## Fillet-brazed (Jan 13, 2004)

DeeEight said:


> Except that only works for identical straddle yoke geometries. Hard to achieve for a test between two. Much easier to measure the arms. I happen to have bikes with both 1991 Deore DX low-profile canti's and Deore XT U-brakes.
> 
> U-brake...
> Cable fixing bolt to pivot center 90mm (straight line), 115mm (actual arm length)
> ...


Ok, but you better check your math on the cantilever. Its actually 2.43. The canti has MORE leverage than a U brake.


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## DeeEight (Jan 13, 2004)

Fillet-brazed said:


> Ok, but you better check your math on the cantilever. Its actually 2.43. The canti has MORE leverage than a U brake.


typo, pad to pivot, 28mm.


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## erkan (Jan 18, 2004)

Black XT u-brakes are fine. Felt way better than oldstyle XT cantis or Pederersen cantis IMHO. Because they had a brakebooster already mounted braking was very solid. Of course you could run it without the brake booster but the solid feel was then gone.

In the 80'ies I saw some bikes with a u-brake on the fork to. They where heavy, but I could run dual u-brakes today (front and rear) just for the cool looks.


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## bikerboy (Jan 13, 2004)

*Are you sure?*



Fillet-brazed said:


> Aztecs work well on U brakes. Is that what youre asking?? U brakes use a threaded post unlike a cantilever pad.


I thought canti brakes had a smooth post that is held in place with a 10mm bolt on the back side of the brake. V-brakes use a threaded post right?


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## bikerboy (Jan 13, 2004)

Fillet-brazed said:


> Aztecs work well on U brakes. Is that what youre asking?? U brakes use a threaded post unlike a cantilever pad.


I though canti brakes used a smooth post and V-brakes use a threaded post, right?


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## Fillet-brazed (Jan 13, 2004)

bikerboy said:


> I though canti brakes used a smooth post and V-brakes use a threaded post, right?


Is that not what I said? Its too early.


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## bikerboy (Jan 13, 2004)

Sorry, I read "unlike" and "like" completely changing the meaning of what you said, sorry.


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## bikerboy (Jan 13, 2004)

*Thank you*



Fillet-brazed said:


> Aztecs work well on U brakes. Is that what youre asking?? U brakes use a threaded post unlike a cantilever pad.


I appreciate your help on this subject. I thought the U-brake used a threaded post like you said, just couldn't remember and I didn't have the bike at my apartment as I store it at the parent's house for safe keeping.

A few years ago when I acquired this bike, it had old dried out brake pads on the back. This was right when V-brakes had started making their entrance into the market place, but I had not seen them yet and wasn't sure about what pads to use on my U-brake. I was familiar with Koolstops and knew them for their power, but I guess I didn't figure to ask about a threaded post brake pad (hey I was not the sharpest tack on the wall when I was 16). Anyway, I managed to find some el cheap pads at Walmart which are for the same el cheapo bikes they sell with the sidepull caliper brakes. I managed to jerry rig them in my brake, which meant releasing a lot of cable to make room for the monster thick pads. It worked, but not nearly as great as what I was used to even on my crappy huffy.

So, thanks to you, I started thinking in the right direction on these brakes. What I thought was brake flex or chainstay flex was really the pads squishing down too much. Thanks for all the great discussion (even the stuff just between you and Dee8) that showed me these U-brakes arent worthless. I happened to have a set of Koolstop V-pads I had picked up for a couple bucks and threw them on the back, and wow, 80% of the flex is gone!

Oh yeah, by the way, I was lookin at the U-brake and I definately think it gives a bike a lot cleaner look not having anything on the chainstays. Anyway, thanks again.


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## chruby99 (Dec 11, 2004)

*Levers*

What kind of levers should be used on a U-brake setup. V brake levers


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## Shayne (Jan 14, 2004)

*Older Canti Levers*

V-Brake levers will work them.
However U-Brakes are ideally suited to the shorter pull cantilever levers or road levers.


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## DeeEight (Jan 13, 2004)

V-levers that can be adjusted for more leverage/less cable pull (such as the 1996 Shimano XT and XTR ones) down around 22mm (which is what Shimano DX and XT SLR levers that were often spec'ed on bikes with their U-brakes pulled) will do the job adequately. Many however can't be adjusted this low.


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