bronthun

hey all, first post.
I usually work on my bike and do the mechanics of it solo, but I've hit a hurdle. I bought this vintage cannondale mtb and wanted to run a mullet drivetrain (1x in front, 7 speed rear). i went to just replace the cranks hoping it would fit, but, sadly the spider kept knocking the chainstay. i went to grab the BB the cranks belong to, and the axle is even more narrow. judging from when it was knocking on the chainstays, i can see that even if i had gotten the cranks on without knocking the stays, it would still be so far out that i wouldnt get past the highest few gears without causing too much chain tilt. im not sure what to do but id love these super record cranks on this bike.
Thanks all

alcjphil

What is the BCD of your crank? In general the wider chain stays of a mountain bike won't work with a road crank and chainring. Mountain bike cranks use smaller chainrings and have a smaller BCD to allow sufficient clearance

rumrunn6

I just avoided my Mother-in-Law ... sorry couldn't resist

cxwrench

'Mullet' refers to different wheel sizes front and rear. 1X refers to the drivetrain.

hokiefyd 

There is terminology that combines "mullet" with "drivetrain". These websites describe it as mixing road/gravel/MTB groups together:

https://nplus2cycles.com/2021/05/16/...w-to-grow-one/

https://youmecycling.com/equipment/t...ivetrain-1x12/

hokiefyd 

If you want to use that crankset on the bike, it sounds like you just need to space it out some with a longer (wider) BB spindle. Figure out your current BB spindle length. Figure out how much further you need your crank to sit from the frame centerline and multiply that by two and add to your current spindle length. That's approximately how long your replacement spindle should be. For example, if your current spindle is 120mm long, and you need your crank to sit another 4mm from the center of the frame, then you need a 120 + 4 + 4 = 128mm spindle. You may need to round up to find an available length. Note that you generally want to maintain a certain chainline, and using only a large ring may mean that you have to space your crank further out than optimal for the lower gears.

Hondo6

MTB BB shells of that era are often wider than the typical road frame of that era (73mm vs 68mm or 70mm). This also contributes to the need for a longer spindle.