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Swapping some cranks on a gravel bike - current BB has MTB cranks, with 2 spacers 1 side and 1 on the other - is it one spacer for road cranks, or none?
None, road bikes don't have 73mm shells or e-type front mechs.
None
Do you need 1 spacer if using an MTB BB though?
Genuine question as I need to replace an old FSA one and was just going to bung a cheap uberbike/gusset one in there.
I misread, didn't realise you were still going to use the mtb bb. As far as I can remember, Shimano mtb bb cups are 1mm narrower than the road ones which would suggest you'll need a 1mm spacer each side when running road cranks.
Are you sure that the cranks will FIT? Q factor will be different to a mtb crank.
monkeyboyjc
Member
Are you sure that the cranks will FIT? Q factor will be different to a mtb crank.
Yes, hence the change, the chainline is a bit crap with the MTB cranks.
A lot of MTBs have 68mm BB shells - but the narrower Q-factor and bigger chainring means it might hit the chain stay - try it?
Just to add to my post above, a BB52 (mtb) cup is ~10.3mm wide, a RS500 (road) cup is ~11.3mm wide
A lot of MTBs have 68mm BB shells – but the narrower Q-factor and bigger chainring means it might hit the chain stay – try it?
The OP has a gravel bike
simondbarnes
As far as I can remember, Shimano mtb bb cups are 1mm narrower than the road ones which would suggest you’ll need a 1mm spacer each side when running road cranks.
Thanks Simon, managed to find the same info, you're right. Hopefully have 2 x 1mm in the spares pile somewhere.
depends on the fame, shirley?
Fingers crossed my Inbound 44t ring from China That will fit Old 2016 slx crank and will be a good replacement for my current POS rival cranks
YES POS RIVAL CRANKS