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Changing old square taper BB on aging Marin. The drive side has the plastic cup on it. Shouldn't it be on Non-drive side? Could the shell have been welded on back to front?
I tried removing it the usual way, ie drive side LH thread, but seems too stiff to be right. Don't want to force it and break the plastic cup.
What's on the drive side? Steel cup? And what's the frame made out of? Aluminium or steel?
Some super-cheap OEM BBs had drive side cups made of plastic. If it's steel and really won't budge, you could try heating the BB to soften the plastic, and then pushing it out. Haven't done this myself, I should point out, but might be the safest way of preserving the threads.
Mebes find a good bike shop if you're nervous about it (I'm assuming this is not the case)
The Non-drive side is a metal cup (steel alloy of some sort), Non Drive is plastic, and it's a steel frame.
And just to confirm - drive side should be a LH thread shouldn't it? At least that's the way I've always found it on Aluminium frames.
Drive side is a LH thread. Of course it's possible that someone put the BB in backwards - I did that when I was young and foolish. With a long spanner, it'll happily go all the way in 🙂
With a long spanner, it'll happily go all the way in
*like*
😀
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A long spanner, yesterday. 😉
Well, all's not yet lost, I'd say. If the thread is nailed, you can get threadless BBs that screw into themselves.
At a guess, Marin use the standard English (rather than Italian) thread. English or BSA threads are lefty loosey righty tighty on the drive side, and the opposite on the non drive side. Basically, the BB screws in on each side in the same direction as pedaling forwards. Italian threads are lefty loosey righty tighty on both sides - so there was a slight tendency for the Non Drive side to come loose from time to time if not properly maintained.
Maybe speak to a long term Marin dealer, or to ATB Sales, the distributor of Marin over here. Then get a nice long spanner and unscrew it.
One last thing - have you cleaned the outside of the cups thoroughly? Some BBs have the direction or side marked, either in the outside of the cup, or on the spindle.
an old marin will have an english thread bb with a 68mm shell.
easy* way to remember which way to turn it is: if the bearings seized and you ride the bike, pedalling it will loosen the bb on both sides.
same goes for pedal threads too, if the bearings are seized pedalling the bike will unscrew the pedals.
*when i say easy, i mean this is how i remember.
I had the exact same issue last week on a '94 Muirwoods of my mates. Plastic drive side cup had me stumped but I just ripped it out the normal way. so no the bb shell isn't welded on wrong but I'd be pretty sure it's rusted as hell if its causing you a problem
haggis1978 - MemberI had the exact same issue last week on a '94 Muirwoods of my mates.
Yep this one is a 94(ish) Muirwoods too! Small World.
The bike is still going strong and in fantastic nick. Gradually has morphed so much that just the original frame and seatpost remain!
I have seen cartridge BB's that way round, not often but confused the hell out of me too.
Removal of BB, clockwise drive side, anticlockwise non drive. line the tool up with the seatpost and rotate in a forward direction.