>>1734153First, work out if your crank arms could stand to be slightly closer before they hit the chainstay, or if they are very far away already. Then, see if your FD has the limit screws maxed in either direction. Or if the chainline is off. Ie, is it the correct bb, now.
This is only possible with the crank installed, and it's worth checking roughly, because you might not find the same length, and often it's ok or even good to change it.
remove it and measure the spindle length
That's the size you want (roughly)
122.5 mm etc
then measure your bottom bracket shell width
It will probably be 73 but maybe 68.
Those are the 2 important sizes.
It will be BSA/ENG not Iso.
Now you look for the shimano item. The high quality one has been discontinued, but try find one, it's the UN-55. If you can't find an UN55, UN300 is the new version, acceptable. If you want a fancy one look at IRD.
