Install bigger crank chain wheel on mountain bike

[Joe Crean]

Hi,

I have a mountain bike thr has a 32 tooth chainwheel on the crank i would like to put a bigger 48 on to the crank axke i. Order to cycle the higher road speeds easier, if you install it in the exact place where you take off the old one it will not fit as it will touch the frame, because the crank is mounter in a indent of the spreader if the framer, is thete a such thing as a longer crank axle or a crank axle extender ?

Regards joe

[Painkiller]

Pictures would help here, but if you use a longer spindle it will affect chainline.

[Criminal]

(02-15-2021, 12:46 PM)Joe Crean Wrote:  Hi,

I have a mountain bike that has a 32 tooth chainwheel on the crank; i would like to put a bigger 48 on to the crank axle in order to make cycling at higher road speeds easier. If you install it in the exact place where you take off the old one it will not fit as it will touch the frame, because the crank is mounted in an indent on the chainstay of the frame. Is there a such thing as a longer crank axle or a crank axle extender ?

Regards joe

Hi Joe,
The previous comment applies. It would depend on how much farther out the chainring must be positioned. A millimeter or 2 should not be to bad. It might also depend on which gears (front and rear) that you primarily use; if you tend to ride your large chainring and smaller rear cogs you might find that your chainline is actually a little better, but otherwise the bike will be noisier and cause more wear to your chain and sprockets if the chainline is too far off when using gears that emphasize the misalignment. Have you checked about changing (getting smaller sizes) for any of the rear cogs? This will not affect the chainline as would a front modification. You might also be able to install spacers/shims between the chainring and the crank spider at the chainring bolt mounts, or between the crankarm and spindle (depending on mounting style), thus effectively providing more clearance with the frame. Is the 32 tooth ring your largest ring (I assume you have a double or triple chainwheel? Seems small for the large ring; if it is the middle or smallest ring I would recommend different shifting/gear selection to provide the resistance you desire.