Need some help figuring out mountain bike crank set

[ctmustache]

I thought I had this figured out, but tonight I realized I screwed up, and I could use some help figuring this out.

I needed to replace the crank set on my old Cannondale M500 as I had several damaged teeth and occasionally the chain would lock up. The bike had a shimano crank set, not sure of the exact model but Shimano Hyperdrive something or other, 48/38/28. I bought Shimano FC-TY501, 175mm with chain guard, also 48/38/28. I also picked up a Shimano U26 68mm x 110mm bottom bracket as the existing one was gritty.

Tonight I installed the bottom bracket, but realized the new crank set is rubbing against the bike frame, DOH! I am pretty sure the BB is an exact replacement size wise for the former BB, so not sure what I could have done wrong. Do the crank sets stick out a different amount from the frame, and if so how can I figure out what I need to make this work? Or, maybe the BB is wrong after all.

Any and all help in getting this back on the road is MUCH appreciated. Thank you!

[Wintergreen78]

Shimano has an awesome compatibility chart that may help.
https://productinfo.shimano.com/#/com/?cid=C-432&acid=C-449

Also, some of their bottom brackets come with spacers to allow them to be used with a couple different frames. Your bb may need a spacer installed to give you the correct chain line. If that was the case it should have come with one or two.

Shimano’s web site is a little annoying to navigate, but their installation and maintenance manuals are really good, and if their stuff is installed per specs it works great.

Edit: just noticed that is a square taper bb, not one of their splined ones. In that case the chain line would be set by the bb spindle length. You can get bb’s with different spindle lengths. I also looked at that chart I shared and noticed that particular model has an option for a 47.5 mm chainline, whereas 50 mm was pretty standard for mountain bikes for a long time.

[Wintergreen78]

Now I went down a rabbit hole and found what you are looking for.

https://productinfo.shimano.com/#/spec/MTB/Front%20Chainwheel


You have to scroll down a ways to get to it, but this says your cranks take a UN-26 D-NL bb for a 47.5mm chain line and a UN-26 D-EL for a 50 mm chain line.

[Clean Shaven]

Spacers won't fix this. You have the wrong bottom bracket - you need one with a longer spindle. When you removed the old BB, there should have been a part number on it - Google that and get a new new BB to match that length.

[GuitarStv]

Yeah, that's the wrong BB.  You need a wider one.

[ctmustache]

Thank you everybody! The compatibilities chart was really helpful, as was the suggestion that I need a longer BB. I've ordered one and crossed my fingers!