I’m in the process of Frankenbiking my 2009 Specialized Rockhopper Comp into a gravel grinder.
Because I’ll only be riding it on paved and gravel roads I’d like it geared a little higher then the normal triple
chainring mt bike setup.
Is it possible to put a compact road crank on this bike? For a drivetrain I’m running 9 speed Gripshifters which I
really like. I would not go the whole nine yards and switch to a road bar/shifter/brake setup.
Thanks,
Nah dude, I believe road BSA is 68mm (70mm Italian) and MTN BB standard is 73mm. Clearance is different.
Depends on the type of the crank. If it isn’t an external BB type, then you can do it, you’ll need to get a BB with the right spacing and probably a longer spindle. The q-factor on a lot of road cranks is narrower, and you ‘might’ have clearance issues on the drive side since MTB chainstays are flared more for the bigger tires.
I was curious too. While I was replacing the crankset and BB on my Spec. Epic… I tried to put in a road bike crankset with compatible BB30… besides the spacing… the crank arms hit the rear chainstay… but if I put spacers to make the arms not hit the chainstay… the q factor was way off and so I assumed that it isn’t meant to put a road crank in there.
you may be able to just get bigger chainrings onto your existing crank.
e.g. Shimao triple cranks like the XT or Saint have a 104 mm bolt circle, and they also make a 48 outer chainring.
that may be enough extra gearing for you.
is Rockhopper a 26" or a 29"
I have a 26" Scott Spark, and for use on the road & gravel road, I have a cheap set of 29" wheels which have a 25 mm road tyre on them as well as a tight road cassette 12-23. The outer diameter of a 26" wheel with 2.1" tyres is the same as a 29er rim with 25mm tyres which give me much better road gearing
a 26" wheel with a 25mm slick loses to much in the circumference and is then geared too low for road type riding.
I hope that makes sense…
I’ve only ever used the older style threaded BBs. My MTB was a 73mm shell, so I used a triple BB and an older splined shimano DA crankset. The clearance with a triple BB was ok, but another splined BB that was for a double crankset did not work right. Since I was only using it for commuting, I wasn’t too worried about the Q-factor. You can just lower your seat slightly with a wider q-factor.
I’m in the process of Frankenbiking my 2009 Specialized Rockhopper Comp into a gravel grinder.
Because I’ll only be riding it on paved and gravel roads I’d like it geared a little higher then the normal triple
chainring mt bike setup.
Is it possible to put a compact road crank on this bike? For a drivetrain I’m running 9 speed Gripshifters which I
really like. I would not go the whole nine yards and switch to a road bar/shifter/brake setup.
Thanks,
If you have the stock 104mm BCD crankset you can simply buy Shimano’s 9 speed “Trekking” chainrings. Both Deore LX and XT were available with 9 speed chainring set ups and teeth combo of 36t x 48t; close enough to your roadie 34t x 50t especially if you have an 11 x 34t cassette.
-SD
I’m in the process of Frankenbiking my 2009 Specialized Rockhopper Comp into a gravel grinder.
Because I’ll only be riding it on paved and gravel roads I’d like it geared a little higher then the normal triple
chainring mt bike setup.
Is it possible to put a compact road crank on this bike? For a drivetrain I’m running 9 speed Gripshifters which I
really like. I would not go the whole nine yards and switch to a road bar/shifter/brake setup.
Thanks,
If you have the stock 104mm BCD crankset you can simply buy Shimano’s 9 speed “Trekking” chainrings. Both Deore LX and XT were available with 9 speed chainring set ups and teeth combo of 36t x 48t; close enough to your roadie 34t x 50t especially if you have an 11 x 34t cassette.
-SD
Thanks, Right now I’m running the biggest chainring that Rotor Q Rings offer for a mountain bike (46). I’d sort of like to stick with Rotor Q Rings but it’s not that big of deal so I may give the “Trekking” chainrings a try.