I'm trying to replace the bottom bracket on my old (I think the frame is from the 90s) Muddy Fox mountain bike, and I thought I had ordered the same one, but I didn't. I can't get the new one in without potential getting the pipe wrench out and forcing it in. My question is, is it supposed to be almost impossibly tight, or do I need to keep looking for the right part?
by Orchuntsman
9 Comments
Shimano discontinued the UN55 model a couple years or so ago. UN300 uses the same threading and shouldn’t require a pipe wrench to install. Have you thoroughly cleaned the shell’s threads and inspected them for any deformation?
It should NOT be that hard to get in. In my experience, I can’t quite get them in by hand but they turn very easily with the tool.
Looks like the right BB. Be super careful to not cross-thread it into your frame. Try cleaning the frame’s threads. Try turning it the wrong way a turn first to engage the threads. Do NOT force it or you’ll ruin the threads on your frame.
If that all fails, consider taking it to a bike shop to have the threads chased (repaired).
Using grease on cleaned threads? Threading the BB in the correct direction?
Shouldn’t a ’90s BB shell be 73mm? Measure the shell width before you go any further. But also, do you have a plastic bottom bracket cable guide? Based on the gouges on the label it looks like it could be binding on the bolt that holds it in. Back that little screw out while you install (make sure the threads are clean) and see if that makes a difference.
Its prolly the old paint I between the threads
Lefty tighty.
I assume both are BSA/English. Are you threading in the correct direction? Left tighten on the drive side. Clockwise to tighten on the non-drive side?
Did you clean the shell? Did you apply grease? Is it cross threaded? It sounds like it’s crossed threaded… in which case you may need someone with a proper tool to chase the threads.
It looks like your under-BB cable guide may be held on with a screw. It has left a small scratch on the old BB shell. The new BB might be running into it, so back it off or remove it while installing.
Other basic concerns: 1. are you installing the non-drive side cup first? That can help guide the cartridge in straight. 2. Are you installing the cartridge from the right (drive) side? It’s left hand threaded so it needs to go in counterclockwise (backwards). 3. Make sure your threads are clean and not cross threaded. If you start it crooked you may get it started but it will bind and start chewing new crooked threads into the shell. Bad. If they’re messed up get a shop to try chasing the treads for you. At that point you might as well ask the shop to install BB for you.
Judging by the scratches on that BB, I’m guessing the bolt that holds the cable guide under the bottom bracket is in too far and dragging against it as you’re trying to install it.
Back that bolt out, make sure everything is greased, and make sure you’re turning it the correct direction.