[ozbikebuddy]

Hi All,
I'm hoping to build up a Pompino 120mm rear end (I can no longer get the 135mm rear end version in an XL anywhere and I already have wheels for that! Bugga).

I need to know the chain line so that I can sort out a crank set. I was hoping that I would be able to run a MTB crank. I have a set so square taper Hollowtech Deores that will do nicely. And this will gove me a lot of chain ring options.

I just need to know the chain line number for a 120mm rear hub, so that I can work out the right BB axle length.

Cheers all

 

[Dave Hickey]

If you are using a 120mm single speed/track hub, you're chainline needs to me 42mm

 

[UrbanPrimitive]

Hickey knocked it out of the park.

A word of warning about running mountain cranks on a frame with 120mm rear - a lot of mountain cranks are built on the assumption that you're putting them on a bike with a wider axle. I learned the hard way trying to get a set of White Industries Eno cranks on my Fuji track frame. I did it eventually, but the saga was mind blowing (re-space/dish rear wheel, alter frame, non-spec torque, et cetera). Dave Hickey helped a lot and the folks at White Industries were great. But if I could go back and do it all over again I'd probably save time, money, and head aches by purchasing a different crankset instead.

 

[SilverStar]

I agree with both above posts...singlespeed/track hubs for 120mm rear ends usually have somewhere between 41-43mm chainline requirements, but a mountain crankset almost certainly will not. Look for a "compact" road crankset (110mm BCD), and you'll have a ton of choices for chainrings.

 

[FatTireFred]

his square taper mtn crank *might* work if he can find the proper spindle length to match chainline to whatever rear hub he is using AND that setup does not result in the crankarm or chosen chainring hitting the chainstay. a good reason not to mix track and mtn bits or be forced to do so by frame mfgers (a 120 spaced cx fame???)