DarKris

I recently upgraded my bike from shimano claris triple to shimano sora R3000 double. I was also running a triple hybrid crank but I switched to a double. I noticed that I has 1-2mm of clearance from the crank to the chainstay which wasn't much of an issue before, however since I added pedal extenders I found the crank clipping the chainstay when I pedal. I bought a chainstay protector which does a good job of also protecting the chainstay from the crank, however I noticed that it started ripping from repeat crank strikes.

IMG_20170305_172916.jpg

I have a 170mm crank which is as low as I can go and I was wondering if there are any 9-speed/threaded BB compatible 50-34 or 48-32 cranks that have more chainstay clearance than the shimano road cranks?

EDIT: So I took the pedal extenders off and no longer have issues with the crank flexing into my chainstay, however my foot is no longer able to be positioned 100% on the pedal. Right now I have 75% of my foot contacting the pedal. Is it possible to run a MTB crank which generally have wider crank arms for more chainstay clearance or am I just SOL?

Barrettscv 

Plan A) You might just try a different pedal without the extenders. What pedals are you using? Find a wider pedal like: https://store.velo-orange.com/index.p...ot-pedals.html


Plan B) If the crank arm is only touching on the drive side, and you have extra room on the non-drive side, you might try to reinstall the crank. It's been a while, but I had this issue on a bike and there was a spacer that I moved from the non-drive side of the Hollowtech II crank to the drive side. That gave me an extra millimeter or two.


Plan C) If that's not an option, the Shimano M590 triple will work with a 9-speed Tiagra or Sora road front derailleur. It comes in a 48, 36, 26 or a 44, 32, 22 chainring set. Just remove the inner chainring and use it as a double.


Shimano Deore M590 9Speed Crankset W/BB > Components > Drivetrain > Cranksets | Jenson USA


wiggle.com | Shimano - FC-M590 Deore 9-Speed 44/32/22T Triple Crankset | MTB Cranksets




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DarKris

Will removing the inner ring give me a 43.5 chainline? and can I set it up to run 48-32?

Barrettscv 

I have the 48, 36 & 26 on my monstercross bike, I use a 22 inner ring. I don't know the chainline data, it will be wider than any road crank, even your road triple. The bolt circle will allow you to replace the 36 middle ring with a 32, but I can't predict how well it will shift. As displayed below with the 48, 36 & 22 chainrings and Tiagra 9-speed front derailleur, it shifts perfectly and quickly. Set-up was tricky at first, you need to use 100% of the reach of the front derailleur. After I rode it and re-adjusted it and rode it, and re-adjusted it again it shifted to the big chainring without rubbing on the cage. I added a dogs fang chain guide and I never drop a chain or have any other issues.

DarKris

Thanks for the suggestion, however I really wanted something that would essentially be a road double with wider crank clearance. I ordered a 2x Shimano Metrea crank which apparently has an 8mm wider Q-factor to my Sora Crank (158 to 150). Hopefully with how much it cost me it'll work out.

Werkin

Yes. With a 68mm bottom bracket shell, 2.5mm spacers are needed.

DarKris

That would still alter the chainline correct?

Werkin

Yes, but that's not a major problem. It would be an asset in some gearing combos.

Another option would be to remove material from the offending edge of the crank arm.

Spoonrobot 

The Deore M590 crankset is not great set up as a double in the outer two positons. It shows and says (sounds) pretty severe cross-chaining on anything larger than the 3th/4th smallest cogs in the big ring and 5th/6th in the middle (or second) ring. I run it as a double with the first two positions but I'm okay with being limited to a 28 small ring.

It also doesn't like to play with all shifter/derailleur combos. I couldn't get mine to work as a triple with road shifters either. So YMMV.

What frame are you currently riding?

fietsbob

MTB crank, just dont install all 3 chainrings & it's a double..

Square taper BB, for my R'off chainline my M730 crank is on a 127.5 BB, its 1 chainring on the middle a toothless guard on the outside.



You can get a triple chainring length bolt set, they let you run 3 chainrings on the same bolt circle..

so whole arm can be further out then 2nd chain ring + a spacer then the middle chainring, the crank spider then a disc chainguard on the outside..


there are workarounds..




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DarKris

As much as I appreciate the versatility of square taper cranks, I will never go back to those as long as I can afford it. Waaaaay too flexible at my weight of ~350lbs and if I forget to re-torque my screws every few months I end up warping the crank interface.

Rant aside I took my bike to my LBS and the tech installed a spacer to the drive side which seemed to stop the crank rub, also pushing my chainline from 43.5 to 45. I was wondering if for added insurance I swap the spacer out for a 2mm, will it be ok or will it mess with my chainline even more to a less ideal extent?

Barrettscv 

Plan B.

I'd leave it with the existing spacer as installed by the bike shop. 0.5 mm is not worth the reassembly.

CliffordK

Are you using a square taper BB?

It may be possible to find a BB with a spindle a couple of mm longer than your current spindle, and it may work.

When I was doing my Litespeed build, I found that the vintage DA cranks I had planned to use had straight arms and hit the frame. I ended up using some more shaped like vintage MTB cranks. Hmmm, I guess they are 110bcd triples, although I almost never drop down to the small ring. I could probably pull it, but it doesn't hurt anything either (chain catcher?)

fietsbob

Low profile cranks come in to meet a shorter BB spindle (Square Taper) like M900 XTR was, vs M730 XT...






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