# What size rotors for my disc touring bike???



## sc10pc (Dec 3, 2013)

Hey guys, I'm new to te bike packing/ touring scene and I am buying myself a new steel frame to build for the tour across America I will be venturing on next year. I want to put some avid bb7 brakes on the bike and I want to know what size rotors to get. The frame I will be building on Will either be a tout terrain grande route from Peter white cycles or a Gunnar grande disc. I'm thinking 160 on the front and 140 on the rear? What size rotors do you guys use in your disc touring rigs?
thanks, 
Chris


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## vikb (Sep 7, 2008)

This will be a road tour?

How much do you weigh?
How much is the weight of your gear?

Do you tend to brake lots to stay slow or let the bike run when face with a descent?


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## TitanofChaos (Jun 13, 2011)

I think it's going to depend on your weight and type of touring, based on the bikes listed I'm assuming road touring

If you're under clyde size 160/140 sounds fine, I run that size on my road/cross bike, I'm 240# so if you're close to that with the bike loaded there shouldn't be issues

I'd go 180/160 or 180/180 for myself, looking at 300#+ loaded up


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## sc10pc (Dec 3, 2013)

We'll I'd like to keep the weight of my gear at around 40-45 pounds via my ortlieb bags. I way 190# so total it would be around 240 give or take with some if the other misc gear.


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## vikb (Sep 7, 2008)

sc10pc said:


> We'll I'd like to keep the weight of my gear at around 40-45 pounds via my ortlieb bags. I way 190# so total it would be around 240 give or take with some if the other misc gear.


160/140mm would be fine. Just use good braking techniques [pulse braking vs. dragging your brakes] to manage heat build up.


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## big_papa_nuts (Mar 29, 2010)

160/160, because why not. And rotors will be easier to source if the need arises.


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## Welnic (Feb 6, 2013)

When you have 240 pounds on the bike I wouldn't worry about the weight difference between a 160mm rotor and a 140mm rotor. I have 160s front and rear on my cross bike with BB7s and I think that they work great. If I was going to be carrying extra weight I might want to have 180/160 because I like the front to have a little more power with the same pressure, but BB7s are really adjustable for how they feel at the lever so it can be done that way also.


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## bsieb (Aug 23, 2003)

160/160 so you could rotate rotors if you had too.


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## VO2 Lax (Jan 2, 2011)

180/160 for my off road rig. I'm sure you'll be fine with 160/140 but 160/160 makes more sense per bsieb rotating comment.


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## sc10pc (Dec 3, 2013)

VO2 Lax said:


> 180/160 for my off road rig. I'm sure you'll be fine with 160/140 but 160/160 makes more sense per bsieb rotating comment.


ok I think that I'm going to go with the 160 160 front and rear. Should I be looking at the bb7 road calipers or the mtb?? I mean everything I'm putting on it with the exception of the shifters bar and stem is for a mtb.


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## VO2 Lax (Jan 2, 2011)

Are you doing a flat bar or drop bars? I think that depends on the type of brake levers you're using? I had a set of BB5 road calipers for my buddy along with so Avid FR5 levers and they did not work as well as the BB7s MTB, I think it has something to do with the pull. I only deal with mountain bikes so maybe someone with a touring rig can help you with this question.


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## sc10pc (Dec 3, 2013)

VO2 Lax said:


> Are you doing a flat bar or drop bars? I think that depends on the type of brake levers you're using? I had a set of BB5 road calipers for my buddy along with so Avid FR5 levers and they did not work as well as the BB7s MTB, I think it has something to do with the pull. I only deal with mountain bikes so maybe someone with a touring rig can help you with this question.


i will be setting it up with salsa cowbell 2 drop bars and some trp retro levers or cane creek levers.


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## Welnic (Feb 6, 2013)

If you use road bike brake levers then you want road calipers. Road and mountain bike levers pull different amounts of cable, the road or mtb calipers match the amount of cable that is pulled.


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## sc10pc (Dec 3, 2013)

Ok i will be getting the 160 rotors for the build!! And also I will be getting the bb7 road version. I just read up on the accidents people have when they try to use mtb disc brakes on the road.


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## cemorse (Mar 28, 2013)

You may also want to consider Retroshift levers for braking & shifting. I've got BB7 Mtn Calipers and get the appropriate amount of cable pull on Cowbell 2 bars on my bike and they work great.

http://www.retroshift.com/


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## fourfa (Mar 5, 2014)

My touring bike (Salsa Vaya) came with 160s front and rear, BB7 Road. I'm 190lbs, and I thought it sucked; barely enough braking power with zero luggage on the bike. Upsized to 185mm (just a rotor and mounting bracket change) and MUCH happier. I can do a stoppie now, that was plainly impossible before.

Fortunately, if you go with the 160 front, it's not hard to change. Just a bit of wasted money


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## pierre meux (Dec 1, 2008)

I run 203 front 180 rear on my dirt touring rig. I weigh 220 and tour where carrying lots of water is often required, so a heavy load. But in my experience with the 203 up front there's no harm in overkill when you don't need it; but when you do need it, like on a long, steep fully loaded downhill, you're damn glad you have it.


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## SimpleJon (Mar 28, 2011)

I would put on the biggest rotors you possibly can for the heat dissipation if you intend on doing a reasonable amount of road touring. Road descents tend to be a lot faster and in many cases a lot longer than off road / trail type stuff. My buddy completely glazed a set of 140 / 160 with BB7 roads and resin pads on one 15Km descent last year in Indonesia his entire set up was less than 250lb. He reckoned it was really sketchy; he was glad that there was no traffic and no sharp bends in the lower section of the mountain.
Sintered pads also help a lot in keeping the the heat off the rotors; you don't have to worry about heating the callipers and boiling the brake fluid with mechanicals.


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## vikb (Sep 7, 2008)

SimpleJon said:


> I would put on the biggest rotors you possibly can for the heat dissipation if you intend on doing a reasonable amount of road touring. Road descents tend to be a lot faster and in many cases a lot longer than off road / trail type stuff. My buddy completely glazed a set of 140 / 160 with BB7 roads and resin pads on one 15Km descent last year in Indonesia his entire set up was less than 250lb. He reckoned it was really sketchy; he was glad that there was no traffic and no sharp bends in the lower section of the mountain.
> Sintered pads also help a lot in keeping the the heat off the rotors; you don't have to worry about heating the callipers and boiling the brake fluid with mechanicals.


How you brake is as important as what equipment you use.

If you apply a bit of constant braking force over a long duration you generate much more heat relative to apply a higher braking force and then letting go of the brakes. Then applying them again. You can alternate front to back.

A German MTB magazine tested the heat capacity of various disc brakes and they were able to make every brake fail due to over heating. You can literally melt the plastic parts on your Avid mechanicals for example and warp the rotors.


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## SimpleJon (Mar 28, 2011)

I know what your saying and agree but my point was that even braking properly loads and long road descents are hard on disc brakes - they never get chance to cool down fully before you're back on them, especially when you are dealing with switchbacks at the top and the like and then in to fast sweeping corners(40 to 50 mph) then taking off 30mph to hit some bends - the brakes don't get the chance to cool down hence the heat is always building. 

Bigger rotors do help as they generate less heat (higher torque at the wheel so less friction required) and they have a bigger surface area to dissipate that heat. Keeping the system as cool as possible is a good thing
I was on canti's, tungsten carbide treated rims, Swissstop Blues and 50lb more; didn't have an issue. 

To be honest I am yet to be fully convinced whether any disc brakes has been proved for road touring or tandem use as yet - but am about to try on my new build.


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## vikb (Sep 7, 2008)

SimpleJon said:


> I know what your saying and agree but my point was that even braking properly loads and long road descents are hard on disc brakes - they never get chance to cool down fully before your back on them, especially when you are dealing with switchbacks at the top and the like and then in to fast sweeping corners(40 to 50 mph) then taking off 30mph to hit some bends - the brakes don't get the chance to cool down hence the heat is always building.
> Bigger rotors do help as they generate less heat (higher torque at the wheel so less friction required) and they have a bigger surface area to dissipate that heat. Keeping the system as cool as possible is a good thing
> I was on canti's, tungsten carbide treated rims, Swissstop Blues and 50lb more; didn't have an issue.
> To be honest I am yet to be fully convinced whether any disc brakes has been proved for road touring or tandem use as yet - but am about to try on my new build.


I agree. Just pointing out there are two important aspects to the equation - equipment and technique.

I have no issue with rim brakes for a road touring bike and I think if you are going to have to manage the heat in your brakes regardless of what type you run - rim or disc.


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## bsieb (Aug 23, 2003)

I have ridden down some grades that had me worried about melting a tube while running ceramic rims and v brakes, makes cooking a rotor seem trivial in comparison. I think smaller is better than bigger if it will do the job.


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## SimpleJon (Mar 28, 2011)

bsieb said:


> I have ridden down some grades that had me worried about melting a tube while running ceramic rims and v brakes, makes cooking a rotor seem trivial in comparison. I think smaller is better than bigger if it will do the job.


My point was that the TS is planning a big tour; if substantial portions of that are going to be on road then he should consider bigger rotors, not for the better mechanical advantage and absolute stopping power but for the better management of heat. I don't think that is bad advice. I completely agree that breaking technique is as important - interchange front and rear for general speed control but favour the rear more - your front brake is most important when you need to lose speed fast for a corner etc.

Did you ever melt a tube or damage a bead, rather than just be concerned about it? I've done quite a bit of road touring over the years and I have never had an issue with overheated rim brakes after a descent, I've had them feel pretty warm but not so hot as to concern me and if a 622 rim feels warm after a descent how hot would a 140mm - 200mm rotor be given all else the same? 
Purely anecdotal but I have come across several people in last few years who have had failures of disc brakes due to heat - I've never come across a tourer who has had a blow out due to overheating the rims except for 1 couple on a 500lb+ tandem who were busy getting a new rear wheel c/w third drum brake FedEx'd out.

Disc brakes do have many advantages over rim brakes especially when its wet and they do not trash the rims; they certainly are a better choice if you are planning a tour taking any off road riding. I wouldn't consider myself some sort of zealot at all but I can understand why failure due to overheating of disc systems is potentially more of an issue than the urban myth it appears to be with rim brakes. Of course it is completely possible to overheat a rim brake if you have no clue what you are doing and constantly brake all the way down a descent but just from the physics a disc brake is going to overheat much more rapidly and take longer to dissipate that heat so a lot more care is required.
I am building up an Rohloff Ogre adventure tourer / bike pack rig at the moment and will be using BB7 mtns as the braking system with 200mm rotors. I will be very interested to see how they hold up on long road descents.


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## bsieb (Aug 23, 2003)

^I have had my rims get hot enough to instantly sizzle flesh when touched. Fortunately my tire and tube didn't blow but I wasn't comfortable with that much heat. I actually run 160/180, mostly for interchangeability of my wheelsets.


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## big_papa_nuts (Mar 29, 2010)

SimpleJon said:


> I am building up an Rohloff Ogre adventure tourer / bike pack rig at the moment and will be using BB7 mtns as the braking system with 200mm rotors. I will be very interested to see how they hold up on long road descents.


Ogre will only accept a 160mm rotor out back.


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## SimpleJon (Mar 28, 2011)

big_papa_nuts said:


> Ogre will only accept a 160mm rotor out back.


Yep you are right, thanks for pointing that out - I had forgotten the calliper was inside the triangle unlike my KM - haven't fully decided on the frame yet.

bsieb - butyl rubber normal operating temperature range is up to 250'F higher for short periods. That's enough to sizzle flesh - off the top of my head thats a potential increase in pressure of something like 25~30% as the tire heats up. If tires are inflated to the max I would imagine overpressure is more of a concern than temperature in the context of a blowout.


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## lighty (Mar 26, 2016)

Which would be better? 160/160 rotors, or long armed cantilever brakes? I am looking at the soma saga series.


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## iggs (Oct 18, 2007)

lighty said:


> Which would be better? 160/160 rotors, or long armed cantilever brakes? I am looking at the soma saga series.


Bit of a thread revival but to answer your question:

My opinion is that disc brakes almost always out perform rim brakes so for me given the choice it's always disc
Why?
-better control (modulation is the correct term)
-better reliability
-with hydraulics they auto adjust most of the time 
-no rim wear (I regularly used to trash rims by wearing out the brake track before switching to discs on most of my bikes)
-better wet weather performance

Just reading through the thread something that no one has mentioned is to check what maximum size rotor on both forks and frame. Bigger rotors generate huge forces that need to be engineered into designs.

As to what size IMHO bigger is invariably better
Why?
-less effort required to generate the same braking force. This means less hand fatigue on long difficult descents plus better modulation (control of braking force)

Approx 70% of stopping force in braking comes from the front wheel so it makes sense to make the front disc bigger. Just have a look at any motorbike to see how they spec it.

180 front and 160 back is always a good option on any bike. 203 front makes a worthwhile difference if the fork will take it. Bigger rotors are heavier (but not a lot) and more prone to slight buckles

I run 203/160 on my moonlander, 180/160 on my commuter and 203/160 on my mountain bike. Where possible I run ice tech rotors to help with cooling.

I'm just looking to build up a bikepacking Mtb and that will have 180/160 because the fork I'm speccing is rated to 180mm max (x-fusion streat)


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## bakerjw (Oct 8, 2014)

I love the BB7. durable. Dependable.
As for rotors, keep them the same. In the event of a crash, let's say that you bend one. If you have a spare, you can swap it out easily enough. If you bend both, you can pull them both and use the spare on the wheel that you need the most.
I am under 200 with a bike weight running 50 to 60 loaded. I use 160s.


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## fotooutdoors (Jul 8, 2010)

bakerjw said:


> I love the BB7. durable. Dependable.
> As for rotors, keep them the same. In the event of a crash, let's say that you bend one. If you have a spare, you can swap it out easily enough. If you bend both, you can pull them both and use the spare on the wheel that you need the most.
> I am under 200 with a bike weight running 50 to 60 loaded. I use 160s.


This. I keep my rotors the same font and rear because, in the event that I injured a rotor, I can make sure that I have a front brake. That said, having done half of a cyclocross race with only a front brake (flatted, and neutral support's rims were narrower than mine), I can't say I would be thrilled with it, but it would certainly be better than only a rear brake.

Typed on my phone. Pardon the autocorrect.


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## bsieb (Aug 23, 2003)

^Just to keep things real, you can also adjust the caliper, or swap the caliper bracket/adapters, if necessary, to move either rotor to the other wheel. 

Carrying a spare is a slippery slope...


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## fotooutdoors (Jul 8, 2010)

I don't carry a spare rotor. Good point on the brackets, though you need to make sure they do indeed interchange since some do not. I would imagine that most bikes have enough play in the housing/cable length that you could adjust to a slightly longer run. As far as adjusting the calipers, there is a functional limit to where you still have brakes. I don't know that I would be able to true a significantly bent rotor within that tolerance using multi tool pliers, but I really don't know since I haven't tried.

Fwiw, I am in the East, so my need for a larger rotor is less than some of you may experience. That said, I like to maximize system resilience to damage, and equal sized rotors is an easy way to do that in my situation.

Typed on my phone. Pardon the autocorrect.


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