# 120mm bottom bracket for fatbikes with 190mm spacing



## Pritchett (May 18, 2005)

Paragon and Nova both sell 100mm bottom brackets for use on fatbike with offset rear hubs or 170mm symmetric rear spacing.

The cranksets designed for use with 190mm rear spacing usually have ~10mm of extra spacers on each side of the BB to deal with the extra spindle length. I know that some 170mm cranks can be used with flipped chainrings to get the right chainline, but chainstay clearance can suffer leading to heelstrike issues in some cases.

It would be very nice to have a 120mm Bottom Bracket option to eliminate the spacers and allow for wider chainstay positioning at the bottom bracket. 

Is this available somewhere? If not, is anyone out there willing to make a few?


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## adarn (Aug 11, 2009)

Have you asked Paragon? I know the newer Surly's are specing those. Might catch on...


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## Walt (Jan 23, 2004)

Would be nice to have - I will bug Mark about it next time I talk to him. That is a super easy one for them to run out 100 of. 

But to more directly answer the question: no, I don't know of an off-the-shelf solution other than adding spacers.

-Walt


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## Pritchett (May 18, 2005)

Thanks guys.

I hope a guy with some clout like Walt bringing this up to the paragon folks might take it somewhere.


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## G-reg (Jan 12, 2004)

This would be nice, don't know how many REEEEEEEALY nice new Fatties I've seen with Top 'O Tha Line cranks....and these goofy ass spacers on either side of the BB.


That said, think REALLY hard about if you NEED a 3x10 drivetrain and 5in tires on 100mm rims, because that Qfactor jump gets crazy. And THEN theres those stays/drops that are that much further outboard too.
The 190Drop/120BB stuff is to make it easier for big MFGs to make a single run of bikes that will keep any prospective fatty owners happy.


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## Pritchett (May 18, 2005)

I've built two non-fat bikes so far. The fatty will be my fourth frame and I guess I've convinced myself that I might want 5" tires sometimes, so I should just build for them from the start. 3x drivetrain is not in the cards, though a 2x might be nice. Bike will start as 1x10. In your expereince, should I be able to get away with a 170mm rear end with standard fatbike cranks and still squeeze a 5" tire?

I tempted myself into just going with what was common on the big bikes. I also think I might be able to get away with simply dimpling some super S-bendy chainstays if I use a 120mm bottom bracket. Haven't drawn things up, but I've got the chainstays and a 100mm BB in hand. Looks very close. I'm not set up for bending my won stuff yet, though I managed some great dimples on my last build with a trailer hitch ball, tube block and a vice.


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## Walt (Jan 23, 2004)

You can do 5" tires and 170mm a variety of ways and make it work, FWIW. 

I emailed Mark to see if he's interested in doing some. I'm guessing he'll say yes because in all honesty it's a dead-easy job for them given that they're already set up for 68/73/83/100 ones. Use a 20mm longer piece of 4130, change one variable on the program, and off you go...but they are always wicked busy with new work so who knows.

-Walt


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## Walt (Jan 23, 2004)

Mark sez:

"Walt,

Easy to do, I'll add them to the line up. Look for them in a month or so.

Thanks,

Mark."


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## Pritchett (May 18, 2005)

Woo Hoo. That was easy!

Thanks Walt!


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## Walt (Jan 23, 2004)

Now someone's going to be asking for a Pony...

-W


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## adarn (Aug 11, 2009)

nice!


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## J_K (Jan 18, 2010)

Any news from the PMW about the 120mm bottom bracket shell?
I don't see them listed yet.


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## Walt (Jan 23, 2004)

They have them. Call or email them. Not sure why they are not on the site yet.

-Walt


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## J_K (Jan 18, 2010)

Thanks for the info Walt!


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## ParagonMachineWorks (Oct 16, 2014)

After doing some market research we decided that we will not be producing threaded 120mm bottom brackets. We found that the larger companies that are pursuing the 120mm are using the PF30 system which allows for the wider shell (i.e. easier to get 5" tire clearance in your stays) without making a sacrifice to your q-factor (internal bearings so your cranks don't need to be spaced out as far). Additionally our research did not give rise to any promising leads on compatible 120mm threaded bottom brackets OR compatible cranksets, making it hard to follow through with implementation on the bike.

With that in mind, if anyone comes across information showing the move toward a 120mm threaded bottom bracket as opposed to a 120mm PF30 bottom bracket please let us know! It's not easy keeping a tab on all the new market trends and "standards" so we appreciate all the help we can get from our customers and fellow bicycle enthusiasts.


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## adarn (Aug 11, 2009)

I would definitely be super into these!
The RaceFace Cinch cranks are what I will put on every fat bike I build and they require 20mm of extra spacers. extra space on the shell would free up a lot of options for wider tires and stays.


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## Walt (Jan 23, 2004)

Cinch system with 190 spindle and BSA cups was my thought too. Mark, you should make these... they really do have a use!

-Walt


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## bikecycology (Apr 26, 2010)

Walt said:


> Cinch system with 190 spindle and BSA cups was my thought too. Mark, you should make these... they really do have a use!
> 
> -Walt


Walt and others,

I have some "on hand info" that Mark can tak away from this. A 120mm threaded she'll is perfect for the Race Face Cinch system for 190 cranks. I happen to have a Surly Ice Cream Truck with the Turbine Cinch cranks. They are using a 132mm bb shell for press fit bearings. This requires (3) 2.5mm spacers on each side.

I also have on hand, for a frame I am going to build, a BSA bb for the same Cinch cranks. They measure 10.5mm each. It comes with (3) 2.5mm spacers and you would generally put one on non drive side and two on the drive side.

There isn't a way, that I see, around from using the 3 spacers on each side but the wider threaded shell would eliminate the need for more. Here is how I see it:

Press fit shell : 132mm + 7.5mm (spacers) + 7.5mm (spacers) = 147mm

Standard Fat shell : 100mm + 10.5mm (bb cup) + 10.5mm (bb cup) + 7.5mm (spacers) = 128.5mm This leaves you 18.5mm short.

The ever so needed "new" fat shell : 120mm + 10.5mm (bb cup) + 10.5mm (bb cup) + 7.5mm (spacers) = 148.5mm This is just 1.5mm more than the proven press fit setup which I believe can be accounted for in the Cinch system.

I hope this helps.


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## smudge (Jan 12, 2004)

another vote for 120mm BSA shells for use with the RF system.

Mark, the Q factor for cranks that are paired with the 190/197 rear spacing is going to be the same regardless of the shell width. You have to consider proper chain line first and work backwards. As was noted, the RF cranks with a 100mm shell and a 190/197 rear end require the use of a lot of spacers and creates a challenge to make room for 5" tires when trying to get the stays attached to a 100mm shell. the 120mm shell has a place for sure.


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## ParagonMachineWorks (Oct 16, 2014)

Thank you all for your feedback! In addition to all of your input I reached out to our contact at RaceFace (who has been extremely helpful) and he reiterated everyone's comments regarding the use of their Cinch system with a 120mm threaded bottom bracket. As mentioned you will need to use a 1.5mm spacer on each side of your spindle instead of a 10mm spacer on each side. Additionally you would need to make use of their slightly longer 189mm or 190mm spindles.

With all this in mind, it turns out that we ran a small batch of these already and had them sitting on our shelf, but were waiting to make sure that they could actually be used before putting them up on our website. The part number for the 120mm BSA bottom bracket shell is BB2013 and is now available for purchase.

Again, thank you all for your understanding, patience and help with this. The fat bike market is still very much a free for all regarding "standards" and we appreciate all the help we can get keeping up to date on where things stand.

- Sam


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## TrailMaker (Sep 16, 2007)

From my perspective;

:crazy:

It appears to me that the Race Face Cinch system is going to be the way to go, to try and cut through all the "new standards" we seem to be getting thrown at us. Doesn't seem to matter what is the flavor of the moment, the Cinch seems ready to adapt. A 120 shell also seems to be a good thing to have available, and may largely supplant the 100 in the near future.

I might also suggest that the shells be threaded extra deep so that people trying to avoid the use of spacers altogether can cut the shell to whatever length they want and still have plenty of thread to work with. My designs so far have landed right on two spacers on the drive side, and so I would cut the shell to 105 and not need any spacers at all, which I find preferable.


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## Meriwether (Jul 26, 2007)

Thank you PMW! I'm happy to hear about and see these shells too. The Q on the 190 is silly wide but it is useful for allowing more range in CS length with an adequate chainline. I do feel that 120 will take over 100.

And now i won't have to do this anymore to get 5" tires to fit with short chainstays! Luckily the cinch BB cups allow going this close to the edge...


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## coiler_guy (Dec 20, 2005)

I ordered a bunch of tubes to start my first home fatty but for some reason forgot the 100mm bb. Also have a Next SL 190mm sitting in my bedroom for this build. If this isn't fate, I don't know what is!


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## coiler_guy (Dec 20, 2005)

Just ordered up the 120mm BB!!! Thanks for all the info here guys!


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## bikecycology (Apr 26, 2010)

*Limits pushed*



Meriwether said:


> Thank you PMW! I'm happy to hear about and see these shells too. The Q on the 190 is silly wide but it is useful for allowing more range in CS length with an adequate chainline. I do feel that 120 will take over 100.
> 
> And now i won't have to do this anymore to get 5" tires to fit with short chainstays! Luckily the cinch BB cups allow going this close to the edge...
> View attachment 959788


Dang Whit, what did you have to run for a ring, 22t. That's out there!


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## Meriwether (Jul 26, 2007)

bikecycology said:


> Dang Whit, what did you have to run for a ring, 22t. That's out there!


You'd think right? But with the Race Face cinch 190 you can fit at least a 30t. I only tried a 28t since that's the biggest I'll recommend and put on there myself. With a flipped ring 170 cinch a 28 fits fine. Nova s-bend 29w chainstays make it possible for me down to 420 CS length. 
Did 5 fats this way this winter!


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## ParagonMachineWorks (Oct 16, 2014)

FYI:

"Fat bikes sure are fun times when it comes to BB's and chainlines. The answer to your question is that, yes, we make cranksets that will fit a 120mm threaded BB configuration. It simply requires using the longer 189 or 190mm spindles we offer, and the thinner spindle spacers from the 170mm kit. Here is a link to our compatibility chart. It is missing some of the newer crank models, but the basics are there: http://www.raceface.com/comp/pdf/FATBIKE-CRANK-CLEARANCES.pdf The section for the Next SL cinch applies to the Turbine cranks as well, though Turbine clearances and q-factors are wider.

The explanation of why a 120mm threaded BB would be of interest is that 100mm threaded BB's work best with a 170mm OLD rear end and a ~67mm chainline. When our 170mm OLD fatbike cranks are installed, they only need a small 1.5mm spacer per side to hit the chainline. So, the desire for a threaded 120mm BB shell comes from wanting to run a 190mm OLD rear end with a ~77mm chainline. Typically these are configured with a 100mm BSA BB using an extra wide spindle and an extra 20mm of spacers on the spindle. With the wider BB shell, you can forgo the extra spindle spacers and set it up the same as a 170mm BB with a single 1.5mm spacer per side.

The wider press fit bb's are usually BB92 (PF41) equivalents of 100mm BSA BB's, so BB124 is somewhat common. No real rules here, so there are wide PF30 or BB30 BB shells as well. The press fit equivalent of this type of BB would be 144mm wide.

I don't think we see many 120mm threaded, or 120mm equivalent press fit BB's on fatbikes, as I think it limits your crank choices to very wide cranksets. With a 100mm BB, it is possible to run a narrower 170mm crankset with an offset single ring, and still get a wide enough chainline for large tires."

- Race Face


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## Meriwether (Jul 26, 2007)

Thanks for that from Race Face. They've got the best options for fats imo. 
But the 190 Turbine is overkill on the Q. It'd be great to have more low-Q options of cranks with adjustable chainlines.

This is a picture of the BB shell I posted above with a Turbine cinch 190. Nova s-bend stays and a 4.8" Lou, 28t ring. I could use an extra 1cm to place the chainstays but I don't know how you'd ever need that much space on the crank arms. 

__
http://instagr.am/p/vm0CXcKV0Q/


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## Feldybikes (Feb 17, 2004)

Whit, there's a mile in there. Couldn't you have gone with a 170 crank with a BB30 ring for better Q and the same clearance? Am I missing something?

(says the guy who's never built a fat bike)


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## Meriwether (Jul 26, 2007)

Feldybikes said:


> Whit, there's a mile in there. Couldn't you have gone with a 170 crank with a BB30 ring for better Q and the same clearance? Am I missing something?
> 
> (says the guy who's never built a fat bike)


It's a good point Feldy, I just didn't have the 170 in-hand at the time. I just ASSUMED i'd need the 190 version for a proper chainline and tire/crank/cs clearance. The RF Crank clearance PDF is a great resource but it doesn't have the CL of a DM flipped on a 170 Turbine specifically. I think they put that "version" in bold as a 190 with the same spindle length as a 170 crank and the chainline is 3mm less than a regular DM 190? (75mm chainline vs 78) I erred on the side of more is better, but now I build around the 170 flipped for a better Q and chainline.


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## Feldybikes (Feb 17, 2004)

Roger


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## virtueminehonour (Jun 14, 2008)

Interesting thread. I'm not a framebuilder but I'm in the process of planning a custom Ti frame. 
190 rear end to allow short stays and the biggest tyres.

I'm going PF30 and RF cinch. I think PF is a great system, with standard sized bearings easily available anywhere. Coming from the ridiculous E13 fatbike BB with it's minuscule unserviceable bearings this is a good thing in my book.

I think a really wide BB shell makes sense, and do away with the spacers which not only look like a bit of an afterthought, but also put the bearings under a little more pressure.
With the RF Turbine and a Hope SRAM type BB, the shell could potentially be as wide as 148mm. (I've got 5mm of spacers in there to allow chainline tweaking.)

20150208_101653 by LOVATSTOVES, on Flickr

With the standard Hope PF30 where the bearings are outboard of the shell, the shell width could be 125mm wide

20150208_102750 by LOVATSTOVES, on Flickr

One thing I found on the RF chainline chart is that the published Q factor for the turbine is a bit out. I think someone measured from inside face of one crank to outside face of the other to get 122mm. Inside to inside face has 205mm clearance

20150208_102058 by LOVATSTOVES, on Flickr

Wide Q factor has never troubled my knees. I can go between different bikes and none of them feel 'wrong'. I think it's one of these things people have read so often, they believe wide Q is a bad thing. I've never actually read anything which proves why wide Q is less efficient, except being marginally less aero on a road bike.


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## TrailMaker (Sep 16, 2007)

And that's the key;

Misapplication. Who gives a flying f-bomb if your legs are aero on a fatbike? ANY bike for that matter. What is done in racing is ALWAYS misapplied to everything down the food chain, no matter what type of racing it is. If you can walk or run, then why can't you "stand" the q-factor of a fatbike? Do you walk/run with your feet closer together than your hip joints, and who has hip joints closer than a fatbike BB?

********. Same as people that "can't stand" a Lefty or a Thudbuster. They're full of it.


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## bikecycology (Apr 26, 2010)

TrailMaker said:


> And that's the key;
> 
> Misapplication. Who gives a flying f-bomb if your legs are aero on a fatbike? ANY bike for that matter. What is done in racing is ALWAYS misapplied to everything down the food chain, no matter what type of racing it is. If you can walk or run, then why can't you "stand" the q-factor of a fatbike? Do you walk/run with your feet closer together than your hip joints, and who has hip joints closer than a fatbike BB?
> 
> ********. Same as people that "can't stand" a Lefty or a Thudbuster. They're full of it.


Well said!


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## Walt (Jan 23, 2004)

Actually, you run with your feet much closer together than your hip width. Trying running down some arbitrary line on the road sometime and you'll see immediately. 

That said, it's all a matter of preference. For the riding I do, 83mm BB and narrower Q is worth trading off 5" tires for, because 5" tires are pointless for me on snowy postholed singletrack - Nates are better for me than anything else and they're only 95mm wide. For someone who wants the shortest possible stays, or the biggest possible tires, or both - different story. Options are great!

-Walt


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## bikecycology (Apr 26, 2010)

Walt said:


> Actually, you run with your feet much closer together than your hip width. Trying running down some arbitrary line on the road sometime and you'll see immediately.
> 
> That said, it's all a matter of preference. For the riding I do, 83mm BB and narrower Q is worth trading off 5" tires for, because 5" tires are pointless for me on snowy postholed singletrack - Nates are better for me than anything else and they're only 95mm wide. For someone who wants the shortest possible stays, or the biggest possible tires, or both - different story. Options are great!
> 
> -Walt


Well said too!

In the end it's preference. Some people don't even have a need for a fatbike and want it anyways. I just built of a surly ice cream truck with turbine cinch cranks. It's wide everywhere. Visually it looks like you'd be just as well off riding a horse. For me, it's quite fine and I like it a lot.


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## TrailMaker (Sep 16, 2007)

Hey;

No argument, Walt, but the hype about it is way over blown. Granted, I'm LARGE, but I don't even notice it. Long stays are better for what fatties are "really for" anyway.


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## Meriwether (Jul 26, 2007)

TrailMaker said:


> Hey;
> 
> No argument, Walt, but the hype about it is way over blown. Granted, I'm LARGE, but I don't even notice it. Long stays are better for what fatties are "really for" anyway.


Thats a provocative statement TM, long chainstays are good for what fatties are *really* for...And what is that?


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## Meriwether (Jul 26, 2007)

> Wide Q factor has never troubled my knees. I can go between different bikes and none of them feel 'wrong'. I think it's one of these things people have read so often, they believe wide Q is a bad thing. I've never actually read anything which proves why wide Q is less efficient, except being marginally less aero on a road bike.


There is a bit of research on wider Q's being less efficient: 
Q Factor in cycling: kinematic and physiological effects - eTheses Repository
The effect of Q factor on gross mechani... - PubMed Mobile - NCBI

But more in the 150 vs 180 ranges for road bikes. One could extrapolate to the newest widest 222 of the RF Cinch Turbine. I know from riding the 222 it feels worse, and did hurt my knees and IT bands. I'm 6'1" tall so for shorter riders doing long rides it may be even worse. I bet it also depends on the age of the rider, older being more affected. In general, it's best to keep Q low as possible, not just for risk of injury and pedaling power and efficiency, but to keep pedal strikes to a minimum. I hate lower BB's, flat pedals, and wide-Q's on singletrack!! For snow it's less of an issue but still sucks in these types of places:


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## Walt (Jan 23, 2004)

Yeah, I have to say, having ridden my hand-me-down 45cm fatbike (built a new one for a friend and he gave me the one I built several years ago) versus another more recent one with 415mm stays - I much prefer the shorter stays for all around handling and traction.

But then again, my theory remains that whatever you like for XC/dry trail riding, you'll like for your fatbike. I have yet to encounter an exception to this rule.

-Walt


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## TrailMaker (Sep 16, 2007)

Meriwether said:


> Thats a provocative statement TM, long chainstays are good for what fatties are *really* for...And what is that?


Traction in snow.


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## Meriwether (Jul 26, 2007)

I'll respectfully disagree. You're a pretty tall guy I think? Maybe proportionally the longer stays work for you.
But in my side by side "tests" (467 to 430 to 450) point to shorter stays as giving more traction flotation and better handling in soft snow. The people I've built bikes for can't believe the difference. I thought longer would be better but not from my experience. I didn't believe it till I tried it after hearing Mike Curiak's claims.


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## Meriwether (Jul 26, 2007)

Walt said:


> Yeah, I have to say, having ridden my hand-me-down 45cm fatbike (built a new one for a friend and he gave me the one I built several years ago) versus another more recent one with 415mm stays - I much prefer the shorter stays for all around handling and traction.
> 
> But then again, my theory remains that whatever you like for XC/dry trail riding, you'll like for your fatbike. I have yet to encounter an exception to this rule.
> 
> -Walt


"Walt's Theorem", I like it.

We've totally derailed this thread.


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## TrailMaker (Sep 16, 2007)

Well;

If you want something to go straight under heavy power, you make it long. Drag bikes. Hill climbers. If you want to it to go round corners at high speed, you make it short. World Rallye. The physics is what it is. What works for you is also. They are not mutually inclusive, nor exclusive.

Train wreck.


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## Walt (Jan 23, 2004)

TM, build yourself a short stay bike and try it. Seriously. I have not found your traction theory to be true IRL on dirt or on snow. And I have an 82.5cm saddle height!

Again, though... theory says you like what you liked for XC which as I recall is a RIP9 or something, right? 45cm chainstays, sounds about right.

-Walt


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## smudge (Jan 12, 2004)

Walt said:


> TM, build yourself a short stay bike and try it. Seriously. I have not found your traction theory to be true IRL on dirt or on snow. And I have an 82.5cm saddle height!
> 
> Again, though... theory says you like what you liked for XC which as I recall is a RIP9 or something, right? 45cm chainstays, sounds about right.
> 
> -Walt


Agreed. And we're talking about a 3-4% change in the wheelbase of a bike for guy around 6'. Overall it's not significant enough to make a drastic difference in cornering. My own fatty has 410mm stays and I love it.


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## TrailMaker (Sep 16, 2007)

Indeed;

Theory does not always pan out in reality. You can't argue the physics, but in application it may not be in evidence to any discernible extent. I understand that full well from having built TONS of stuff for more extreme use than biking. I don't notice much of any of the stuff people blather on about anyways. Trailmaker #3 will have .86 shorter stays, 2* slacker HT, 1* forward on the ST, and 10mm more fork rake. I'm jazzed to experience it!


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## Daniel Thomas (Aug 1, 2015)

Hi everyone!

I have been reading about the chainline and the setup for 1x for 190/197mm. I like the idea of having 120mm BB shell instead of spacers because it would give me more space to connect the chainstays. But I am still confused about it, maybe someone can clear things up for me.

There is an Austrian (that's where I live) online shop where I could get 190mm Raceface Ride cranks. I am thinking about getting them because of the low price, considering that I am already spending a lot on all the stuff I need to make my carbon fiber frame. Perhaps it is just because I have never had a BB in my hands, but I am not quite sure how this fits a 120mm BB shell. Here is picture of the Ride:

https://fatbikes.at/media/image/thumbnail/Race-Face-Ride-Crankset-Fat-Bike_720x600.jpg

From the Raceface chainline pdf I figure that the dogbone BB disassembles into three parts. So the outer ones are called cups and they go into the threads off the BB shell, right? So what about the center part? If it is supposed to reach from one cup to the other, then won't it be 20mm short?

https://raceface.com/comp/pdf/FatBike-CrankSetup-Chainline.pdf

For some of my favourite trails, the uphill slopes are between 10% and 15%. On my AM bike, I am fine going up with 22t chainring and a 11-36 cassette. To get similar gears with a 11-42 1x11 setup, I need a 26t chainring. I read a thread here somewhere where it was explained that the chainline is 2mm different for 30t chainrings because they require a spacer due to their small diameter. Are there any additional issues with 26t?

Daniel


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## Daniel Thomas (Aug 1, 2015)

Oops, posted twice


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## bikecycology (Apr 26, 2010)

Daniel Thomas said:


> Hi everyone!
> 
> I have been reading about the chainline and the setup for 1x for 190/197mm. I like the idea of having 120mm BB shell instead of spacers because it would give me more space to connect the chainstays. But I am still confused about it, maybe someone can clear things up for me.
> 
> ...


Daniel,

The dog bone part is just a dust/cover plastic piece that pushes in with o rings. You just discard it and use the BB cups. I have a Surly Ice Cream Truck which has a 132mm shell therefore I couldn't use it either. Not a big deal.


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## Daniel Thomas (Aug 1, 2015)

Thank you for clearing this up! Unless I overlooked something that was the final missing piece. I can continue with the drawings.

Daniel


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## Meriwether (Jul 26, 2007)

I've not heard about the chainline spacer issue with the 26t direct mount ring. But you'll need to find 3-4 of the 1.5mm spindle spacers that usually come with the 170 spindle crankset (for 170 rear axle). Using these you can take up the leftover space on the spindle before using the cinch to adjust final bearing preload. This also allows a little bit of chainline and crank arm adjustment (to clear the chainstays)


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## Daniel Thomas (Aug 1, 2015)

Looking at the cinch system, I just realized that a regular 26t chainring won't work on 1x Ride cranks because they come with a 104 mm BCD. So far I only used 2x and 3x cranksets with four bolt chainrings. I could use 2x cranks with a bash guard instead of the larger chain ring. I am not familiar with the direct mount system(s), but it seems that if I were to use a direct mount ring I could use a 100mm BB and a 170 mm splindle with a flipped ring. I'll need to think this through, so thanks for making me aware of it!

Daniel


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## Meriwether (Jul 26, 2007)

Daniel Thomas said:


> Looking at the cinch system, I just realized that a regular 26t chainring won't work on 1x Ride cranks because they come with a 104 mm BCD. So far I only used 2x and 3x cranksets with four bolt chainrings. I could use 2x cranks with a bash guard instead of the larger chain ring. I am not familiar with the direct mount system(s), but it seems that if I were to use a direct mount ring I could use a 100mm BB and a 170 mm splindle with a flipped ring. I'll need to think this through, so thanks for making me aware of it!
> 
> Daniel


That's the best option in my opinion if you can get the crankarm clearance with the chainstays - flipped ring 170 Cinch just for Q-factor alone. I'm not sure what the smallest ring you can use with the 104BCD but unless you need 2x the DM is the way to go in my opinion.


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## Daniel Thomas (Aug 1, 2015)

I have continued making the plans and I don't think clearing the cranks will be a problem. I see that with metal tubes, bending and in some cases dimpling is necessary. The carbon fiber composite gives me an advantage in shaping because in the simplest approach I only need to shape a rigid foam core to clear the crank and the tire taking into account the thickness added by the laminate. On the dropout end, the SRAM frame fit specifications are puzzling me. The chainstay must not extend further than 13mm below the line connecting the BB and the rear axle for the first 66mm (page 24). But at the same time, according to page 29, there has to be a clearance of 15.5mm between the chain and the upper edge of the chainstay. That would not leave much thickness for the chainstay. I haven't figured out why these 15.5 are necessary when the chainstay is outside of the plane of the chain and thus not interfering with the chain this close to the dropout end.

https://sram-cdn-pull-zone-gsdesign...00000004911_rev_b_2016_mtb_drivetrain_ffs.pdf

Daniel


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## alshead (Oct 2, 2007)

Is there anywhere that publishes the Internal clearance of cranks- RF publishes the Q-factor, which is the measurement to the outside of the crank arms, but not a measurement to the inside? Am I missing something?


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## Feldybikes (Feb 17, 2004)

alshead said:


> Is there anywhere that publishes the Internal clearance of cranks- RF publishes the Q-factor, which is the measurement to the outside of the crank arms, but not a measurement to the inside? Am I missing something?


No that I know of. Do you know what cranks you're going to use? I can measure the thickness of my Aeaeaeaeffects if you want. Or better yet, is there a reason to not just buy the cranks now? (One I could think of is if you're still deciding on 170 vs 190 mm crank width.)


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## wind_dre (Apr 7, 2016)

Dear,

I'm trying to find BB120mm (because the frame has 120mm BB) but I'm not able to find any !!
Some of you know a webshop where I can find 120mm BB's ??

Thanks !!!


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## Feldybikes (Feb 17, 2004)

I think you can just use a raceface bottom bracket that's for a crank intended for a 190mm rear spacing and not use the extra 10mm spacers. I'm not sure if they have a longer plastic sleeve to go between the bearings than one for a 100mm bottom bracket or not.


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## Ozzie Puente (Jun 2, 2016)

I have a 120mm BB with a jis square taper spindle. i have 7 speed freewheel, going 10 speed cassette in the rear. can I keep the m361 crankset? if not, what BB / crankset combo is recommended. thx in advance


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## Feldybikes (Feb 17, 2004)

Ozzie, respectfully, wrong thread, wrong forum. Try Drivetrain. I'm guessing you searched by 120mm and found this thread. But this is about a 120mm BB shell width and you're talking about a 120mm spindle width.


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## Ozzie Puente (Jun 2, 2016)

I have a 120mm BB with 190mm rear spacing frame. I'm going 10sp.(maybe 9sp.) in the rear. I have a M361 crankset, if I cant keep the crankset, what BB/crankset combo is recommended?


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## Ozzie Puente (Jun 2, 2016)

"120mm bottom bracket for fatbikes with 190mm spacing" 
Isnt this the title of the thread?


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## life behind bars (May 24, 2014)

Ozzie Puente said:


> "120mm bottom bracket for fatbikes with 190mm spacing"
> Isnt this the title of the thread?


Yes, bottom bracket SHELL. The Drivetrain forum will net you what you seek.


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