square taper BB's

[young Ed]

so i rebuilt my 'traditional' or old style BB today and saw that one of the cups is messed up and i need a new BB
it needs to be:
Square taper
English thread

had to replace crank/chainset recently and i have noticed however tight i tighten the axle nuts a fair bit of the axle still shows on the inside between the frame and the crank, could it be that is have mixed JIS square taper and that other one that i forget now!?

i was going to get a shimano un55 unit to replace it with but i measured up today but my current set up measures 68x137mm have i got this wrong or some thing as i can't find any un54/5 units 137mm long?

any other sealed square taper BB's i should look into other than the un54/5?
Cheers Ed

 

[smokeysmoo]

You just measure end to end like this, it may even have the size stamped in it around the centre area.

 

[young Ed]

You just measure end to end like this, it may even have the size stamped in it around the centre area.

View attachment 40036

thats what i did and i got 137mm does this sound unreasonable?
Cheers Ed

 

[PpPete]

137 sounds unusual.
Is it one of those old 'uns with the "bolt" as part of the spindle and the cranks held on by nuts?

a fair bit of the axle still shows on the inside between the frame and the crank

Always does - this isn't anything like HT2

one of the cups is messed up

Left or right cup ? I might have a spare one

 

[compo]

Has you existing spindle got a hole in each end so the cranks are secured by a bolt or does it have a threaded portion to allow the cranks to be secured by nuts. If a threaded portion only measure the unthreaded length of spindle ignoring the threaded parts.

 

[Sharky]

This a job for your LBS. Even if you have all the tools, It's just less stressful if you let the LBS do it. They will have a store room full of different lengths and they can try several to make sure it's the right size. I did this a few weeks ago and it only cost around £30 (inc a new BB) to have it fitted and the gears adjusted correctly. much less stressful.

Cheer Keith

 

[young Ed]

thanks all!
it is the type with a threaded portion and a nut so that is where i went wrong in measuring the threaded sections as well! will pull cranks off when i get a chance and get the digital vernier callipers out again to measure with out threaded parts

@PpPete
very kind of you with the offer of the cup but i have a spare one that i forgot about when re-assembling it and to find out which one is damaged i would have to dis-assemble and then check and then re-assemble wasting more grease that i am running out of in any case so not really worth it!
Cheers Ed

 

[kloeshuman]

I have a 127mm I just changed out on my bike(that seemed real long). Had to go a little shorter to get the adjustments right. Ended up with a 122.5 on it now and things work great, I like to do these things myself though