Removing a BB from a GT

[AR-CoolC]

Logic says that's the wrong way, as in threory pedalling along is un-screwing the BB.

better than tightening it up :shock:

True! :shock: It was bad enough getting it out already. I had to put the splined tool in the vice and use the frame for leverage. The drive side plastic insert was completely destroyed.

Anyway, that's out, and clearly needs replacing, so the next question. What size is it. The markings on the cassette are rusted over. I've measured the frame and it's 73mm wide and the threaded opening is 37mm accross (approx)

Looking on various sellers web sites the 73mm bit looks right, but then the other size doesn't fit with quoted sizes.

So it's 73x??? what's the ??? ?

TIA

 

[cce]

depends on the cranks - what cranks are you using?

 

[perry]

if your reusing the cranks that came off measure the axle and get the same

from memory the shell will be 24tpi ( threads per inch ) so pretty much any normal cartridge/cup and cone bottom bracket will fit with the 73mm width

its only weird or old frames ( 50s raleighs ) that used different sizes and threads ( like italians )

if you can , give the inside of the frame a good clean with long brushes and give the shells threads a good going over

 

[Xesh]

So it's 73x??? what's the ??? ?

That's the axle length measured from the end of the taper one side to the same part on the other side.

Depending upon the crank that was fitted it will be anywhere from 107mm to 127.5mm. You don't have to worry about the diameter of the BB shell as that'll be standard. It's only the axle length and the shell width (73mm) that's important.

What length you need to buy will depend upon what crank you're fitting. If you're going to re-fit the old cranks then just measure the axle you have and get the same size. If you're changing cranks then you need to find out what length axle the new ones need.

 

[AR-CoolC]

Cheers all, thanks for the replies.

It never even occured to me to measure the axle length :roll: