Quick BB question

[seanr68]

Hey all.

I've got a 94 Kilauea with standard(worn)un51 bb. Its a 68mm x 110mm, with a Standard Sugino Impel crank. I'd like to know if its possible to fit a slightly different length bb? Just a mil or two either longer or shorter. Will it have a huge impact on gearchange/chainsuck/wear etc?
I've been seeing a lot of 107mm and 113mm bb's. There are 110mms out there, but I was wanting to upgrade to a un90/91.
I frame/forks are currently at Bob Jacksons for a respray so I can't check to see how much distance I have between crank rings and chainstay, etc.

Thanks for any info.

 

[hamster]

Apart from the obvious one of the chain rings hitting the frame, if you fit one too short you might find that the chain scrapes the outer ring when on the top sprocket and middle ring.

Frankly, you will probably get away with 3mm each way. I'd change up to a UN72 which has the hollow axle and so most of the weight saving of a UN91.

 

[seanr68]

Smashing!
Thank you very much for the info.

 

[wookiee]

Yeah I think you would get away with a 3 mm difference...I'd go larger rather than smaller tho...

 

[FluffyChicken]

107 will bring the non-drive side crank in ~3 mm towards the frame.

113 will place the drive side ~3mm further from the frame.

That is assuming you stick to Shimano bottom brackets.

 

[The History Man]

Don't want to hijack the thread but how do I know what size BB I would need for my MF R&R?

 

[wookiee]

Don't want to hijack the thread but how do I know what size BB I would need for my MF R&R?

Depends on what crankset you are running...

 

[The History Man]

A sugino that's started clicking! What do I need to know? Last one I stripped had cotter pins.....old school.

 

[wookiee]

A sugino that's started clicking! What do I need to know? Last one I stripped had cotter pins.....old school.

Try Sheldon Brown....google him he is the bike guru!...Personally I have replaced all the BB's on my bikes for sealed ones...un54 or 55

 

[The History Man]

Thanks fellow Marin lover.