How do I work out which Bottom Bracket I need?

zimzum42

Have got my Bob Jackson frame, very nice indeed.

How do I work out which spindle length I need when setting it up.

I don't want to have to buy a selection of BBs to do it trial and error, is there a way of measuring it up?



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Tom753

Depends on the crank and BB doesn't it? The easiest is just to get a track chainset and the BB that goes with it.



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Tako

What colour scheme?!

Tako

Yep, depends on cranks.

Tako

http://sheldonbrown.com/bbsize.html

zimzum42

I ordered peppermint, but it's come out a bit bianchi. am starting to like it though......

I have stronglight cranks, will try and see what type, but not sure they have a name on them. it's a double crank running single on the inside bit with surly sprocket at the back.

would i be better off just buying a dedicated track chainset? would love to save the money though!!!!

cheers




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Unknown

Also depends on rear hub; some (Goldtech and, I think, Royce) have a chainline which seems to assume a standard road chainset set up with a single ring. Track standard is 42mm, but it's a standard in name only.

monty_dogcp

Fit a BB, measure the chainline and determine the difference from the ideal - add double the difference to the BB length you already have to get the right BB length. Worth remembering that Stronglight chainsets can be either ISO or more recently JIS tapers - so make sure your BB is right for the cranks. FWIW most taper crank BBs are going to be from 108-113mm. Consult the venerable Mr Sheldon Brown for the full ho-down.

Unknown

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Monty Dog</i>

Fit a BB, measure the chainline and determine the difference from the ideal - <b>add double the difference to the BB length you already have to get the right BB length.</b> Worth remembering that Stronglight chainsets can be either ISO or more recently JIS tapers - so make sure your BB is right for the cranks. FWIW most taper crank BBs are going to be from 108-113mm. Consult the venerable Mr Sheldon Brown for the full ho-down.
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Except... (there follow some notes I have collated over the aeons)

"Mountain bike" bottom brackets (whatever <i>they</i> might be) are symmetrical
Road bottom brackets are normally asymmetrical, with the RHS being longer

If you swap to a longer road b/b, the extra length is on the RHS, but a longer mountain bike b/b will split the extra length between sides, or may have it all on the left as compared with a shorter road b/b

<i>However...</i>
Shimano UNxx 110mm and 107mm BBs both have the same drive side overhang - the NON-DRIVE SIDE is 3mm shorter on the 107mm BB

Shimano don't make a BB with a shorter drive side than the 110 or 107mm UN52/53/72/73 BBs
So don't buy a 107mm Shimano BB in the belief that it will shift your chainline - it won't
All you can do is use a 110 (or 107, whichever gives symmetrical crank/chainstay clearance) and adjust the chainline at the hub

The next size up (Shimano) is a 113 - and just for kicks, the difference between a 110mm and a 113mm is 3mm on the DRIVE SIDE

And, FWIW, I have found that Stronglight cranks of all vintages and regardless of their taper work quite happily on Shimano UNxx bottom brackets. It's just that they won't fit on quite as far if they (the cranks) are ISO; and I wouldn't use ISO cranks on an ISO axle once they had been fitted to a JIS axle.

smiorgan

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by NickM</i>

So don't buy a 107mm Shimano BB in the belief that it will shift your chainline - it won't
All you can do is use a 110 (or 107, whichever gives symmetrical crank/chainstay clearance) and adjust the chainline at the hub

The next size up (Shimano) is a 113 - and just for kicks, the difference between a 110mm and a 113mm is 3mm on the DRIVE SIDE<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">

Not the OP, but that's really useful (if disappointing) info to me - cheers mate

graham_g

I've done two conversions with double crank set (with a 68mm bb shell) and both have used a 110mm BB with the ring on the inner mounting on the cranks.

This doesn't mean much but I thought it might help [:D]