Chainring position on a fixed?

BigSpecs

I am in the process of changing the frame on my "fixed wheel bike" (no americanism's here, fixie, pah!) I am changing from a 1960's(?) Raleigh lenton Sports to a more up to date 1980's Raleigh. I have fitted the same bottom bracket (Shimano 107mm) but when I went to fix the chainring it is really close to the frame and actually catching the chainstay.

How close can the chainring safely be to the frame?

I am using a modified road chainset, using only one ring with washers in between the screws. Is it possible to mount the chainring on the outside of the spider to prevent the frame touch?

Would a track specific crankset work better?

Do I need a longer BB?

Will all this upset the chainline?

Lots of questions, sorry.

andrewgturnbull

Hi there.

It all depends on your chainline - if you add in spacers and move your chainring further out, then you chainline might not be straight enough.

If this is the case, then you might need to simply fit a smaller chainring, then either pedal at 200rpm or fit an 11 on the back!

Cheers, Andy

croggy

When I built my single speed I used a 113mm BB and a double chainset with the chainring in the outer position.This gives 6mm clearance between teeth and chainstay.

Monty Dog

It depends on the angle of the chainstays from the BB shell and can be a problem when converting 130mm OLN road frames - it terms of closeness, as long as it's not touching and doesn't rub under load is good for me! Using the outer chainring position is OK as long as you can move the sprocket outboard too and keep the chainline as straight as possible - anything more than half-a-chain width can cause problems.