Bottom Bracket Basics

cbriddon

Hi there,

I have 2 Boardman bikes. A Hybrid Comp with a BB10 bottom bracket and a Road Team with a BB30 bottom bracket.

The road bike is fine at the moment but the hybrid is 14 months old and done about 4000 miles and is currently on it's 3rd bottom bracket.

I was wondering, can I fit different bottom brackets if required? Is there a standard fit or a few standard fits so that I can choose from a range of BB's? I know there are internal and external fits but could I fit something a bit more 'up market' when I next need to replace it.

Essentially I don't get BB fittings in general and would like it explaining. :-)

Thanks in advance,

Christian

nicklouse

there is no BB10.

have a read of the info on Parktools to help ID what you have.

just about anything is possible with the right amount of money.

in general re Shledon Browns pages.

For specifics ask away.

cbriddon

Thanks for the info. I was sure that the Hybrid had a BB10 but I guess not. :-) Looking at the Boardman webpage it's an FSA cartridge BB.

I'll check those pages.

cheers,

Christian

cycleclinic

There many kinds of cartridge BB (square taper, OctalinkV1 and V2, ISIS, tune's hexangonal taper...) but being FSA it would be square taper or ISIS. If it is ISIS that is probably why you have gone through 3 BB's, they are shite. If you are determined to keep the crankset and it is an ISIS then the FSA platinium Pro might give you longer life but in my opinion cut your losses and bin the BB/crank and get a new crank and BB.

As you have a double chainset with a 34/50T chain rings then the cheapest solution would be a a Shimano 2350 double 50:34T with a UN 55 bottom bracket. RRP for both is £77 but they an be had for less. You can of course go for a Shimano sora, Tiagra, 105 or higher chainset if you want. Square tapers BB just work and are very durable.

cbriddon

Thanks!! I know what my BB looks like but didn't know what was compatible so what I could replace it with.

I'm not bothered about keeping the crankset so I'll take your advice and go for something Shimano based.

Cheers,

Christian

cycleclinic

All BSA threaded BB will fit.

Look on Sheldon's browns site for pics of the various axle type. Square taper BB still seem to be the most durable, Avoid ISIS like the plauge and SRAM GXP BB's. If you have a square taper BB then ust measure the axle length and the shell width (it's either 68mm or 73mm, probably 68mm though) and buy a cheap and chearful Shimano UN55 of the right axle length.

If you feel like a new crankset then most these days come with out borad cups. These screw into you BB shell as normal. Again you cannot go far wrong with a shimano crankset with one of their BB's. With the out board bearing BB you will need to have the BB shell faced first before fitting though unless you like replaing BB!