Square Taper Bottom Bracket Fitting

sharding

Can anybody help me with this? I have purchased a new Shimano square taper BB to fit to my atrek. 1.5. I've removed the old one, but when trying to screw in the new one, the threads appear to cross and I can only screw in both ends, at most, half way in. I've re-tried several times, but no luck. The new BB is the same spec as the old one. What am I doing wrong?

Wooliferkins

Have you got it the right way round? L/H thread on R/H crank

craker

I doubt you'd get it in half way either cross threaded or the wrong way round.

Get your old bb and see if that screws back in and out nicely.

It might be that you need to give it some welly - however its your bike and stripping the thread is a costly mishap.

btw I've been using a £5 extra cheap bb on my fixie hack bike, only I found it was creaking and wouldn't tighten up. Thinking this might spell the end of my old fixie frame I parted company with £10 on a discounted Shimano (UN54??). Thankfully that went in - it was quite stiff but tightened up at the end of its travel. The lesson here is that really cheap bbs may work fine but have poorer quality threads / poorer quality material.

If you're still stuck, put the old bb back in and that'll keep your bike running, then try a different brand of bb to see if that screws in nicely.

sharding

Thanks both. I have put it in the right way round (ie the same way round as the old one), but the bb is obviously not going in straight, as you can tell that the spindle is not going centrally through the bb shell. I have since put my old bb in and it went in fine, so I'm still using that. The new one is a Shimano UN54, but it looks like I wasted my money. Shame, as it seemed it was going to be such a simple job.

Twostage

If you haven't tried it already screw in the collar on the non-drive side first this will act as a guide keeping the BB central as you screw it in from the drive side.

desweller

Is the old one also a cartridge unit?

The reason I ask is that I've just done a BB on my dad's bike. His old BB was a conventional (well, I think of them as conventional) cup-and-cone adjustable unit, but the new one was a cartridge BB; UN54 as it happens. It took me quite a long time to realise that the reason it wouldn't go in cleanly was because the cable guide screw into the BB shell was fouling the BB housing...