bottom bracket question

indy335 said:

I have a cheap mountain bike (bought in the UK) that I have customised to suit me so I don't want to get rid of it and it does the job as far as I'm concerned.
The bottom bracket and cups and bearings are worn out and according to my local bike shop he can't find a replacement (the spindle measures 145mm, one cup is reverse thread the other isn't). The shell that houses the BB is 70MM and the threaded hole is 35MM in diameter. Can anyone tell me if I can use a sealed BB in a situation like this or is there any other solution to my problem?

thanks.

PS. the frame has OST Universal written on it. I assume that stands for oversize tubing - but I could be wrong.

Is that BB shell width correct? Are you sure it isn't 68mm or 73mm or even 71mm? A 70mm BB shell would normally suggest an ITALIAN THREADED BB shell, but the threading is 36x24 and BOTH sides would be right hand threaded.

With regard to the spindle length ... is that 145mm length correct?!?

We aren't talking about NASA level precsion, but measurements converted from English-to-Metric (if that is what has transpired) are unwise when dealing with some bicycle components.

Who made the bike & when was it made?

BTW. The odds are VERY HIGH that your bottom bracket could be rejuventated if you simply replace the ball bearings despite what the guy at your bike shop says -- the cost is about $0.10US each ... so, that's about £1.00 ... not much profit for your bike shop in that.

Does the current BB spindle have threaded BOLT-type ends? Are the "ends" square tapered?

If so to both, then you can probably (but, NO guarantees!) use a "sealed" cartridge type BB -- e.g., Shimano UN-xx ... where xx represents the model number ... if the bike's frame is steel, you can probably use a 113mm wide spindle ... for an aluminum frame, you will want a 118mm wide spindle (recommended, sight unseen).

The crank bolts which use an 8mm HEX should actually only cost about 50¢, but most shops seem to charge about $2.00US, each!

indy335 said:

I have a cheap mountain bike (bought in the UK) that I have customised to suit me so I don't want to get rid of it and it does the job as far as I'm concerned.
The bottom bracket and cups and bearings are worn out and according to my local bike shop he can't find a replacement (the spindle measures 145mm, one cup is reverse thread the other isn't). The shell that houses the BB is 70MM and the threaded hole is 35MM in diameter. Can anyone tell me if I can use a sealed BB in a situation like this or is there any other solution to my problem?

thanks.

PS. the frame has OST Universal written on it. I assume that stands for oversize tubing - but I could be wrong.

Does it have a one piece crankset or a three piece?

If a three piece, then you may be measuring the length including the threads. Just measure the length from the edges of the square drive.

Is it really possible that a mass market (cheap) maker has developed a proprietary BB such that our friend will not be able to find a replacement? No, especially if it is so similar to a standard english bb. (why would any company bother?)

Keep digging, although unless you measured your stated dimensions with a caliper or other high precision instrument, I would almost just assume it was a standard English 1.375X24TPI with a 68mm width, and you just need to find a BB with the correct type of pedal attachment and the right spacing for the chainrings.

garage sale GT said:

Is it really possible that a mass market (cheap) maker has developed a proprietary BB such that our friend will not be able to find a replacement? No, especially if it is so similar to a standard english bb. (why would any company bother?)

Keep digging, although unless you measured your stated dimensions with a caliper or other high precision instrument, I would almost just assume it was a standard English 1.375X24TPI with a 68mm width, and you just need to find a BB with the correct type of pedal attachment and the right spacing for the chainrings.

Thanks for replying! I did meaasure the shell with a digital calaper - I think it is a fairly acurate device. My local bike shop has tried to get one all over the place so it is presumably non standard.
I have, since my post managed to contact the manufacturers of my bike and they say they can supply me with a bottom bracket!

Thanks all you guys for your input. I'm waiting for the part to come from the manufacturers.

P.S. I'm not a bike expert but the measurments I gave were made with a digital caliper and I assume pretty acurate. The bike is made by the Universal company (who are supplying the BB), there are two cogs on the crank end and five cogs on the rear giving 10 gears. It is a poorly designed BB in that one cup is reverse threaded.

indy335 said:

It is a poorly designed BB in that one cup is reverse threaded.

Almost all BBs have a left hand thread on the right cup, to prevent the cup unscrewing with pedalling. Why is this poor design?