Bottom Bracket question ????

[supercooper88]

I'm getting confused here my bike at the moment as standard has a square taper bottom bracket 68x103 could I change this to a hollowtech bottom bracket if I was to change the crankset etc and also if this was done would the chain run tru.

I've noticed the square taper bottom bracket in my size are difficult to find and the closest I can see is a 68x102 and 68x107 and I am led to believe this wouldn't fit my original crankset

Any help would be greatly appreciated

Cheers

 

[Tim Hall]

68 x 102 will be fine. You'll be moving each crank 0.5mm closer to the bike.

 

[NormanD]

I'm not sure if you can fit a Hollowtech to the Boardman frame, but the TOKEN BB that is a direct fit for your frame has good reviews for longevity, so worth just considering buying that

 

[ayceejay]

This is the size and type of BB used on Sugino messenger (RD 2) crank set which is a common set up on 'fixies'

 

[RecordAceFromNew]

Since you have square tapered currently you must have a threaded bb shell. If you have a threaded bb shell then it is nearly certain that you will be able to use Hollowtech 2 chainset/bb. However outboard bb's have higher demands on bb shell facing, shell rigidity and L-R thread alignment than cartridge bb's, so your frame might need preparation and even so the bb might not last as long all else being equal. YMMV.

102mm bb's are probably iso, not JIS which your 103mm bb is most likely. You wouldn't want to mix up the two taper standards because they will give you different chainlines. Also to be sure you might want to check you have a 68mm bb shell (rather than e,g, 73mm bsa or 70mm Italian e.g.).

A 107mm JIS is 2mm longer than the 103mm on each side. However don't assume you can always scale bb spindles this way because many are asymmetric.