Hi
What spacers should you use on a road frame with Shimano hollowtech road bottom bracket?
My front mech currently hits the frame and rubs on small / big cogs so think I may need a spoacer in there (don't think I have any at the moment but only just thought of this in the mifddle of a boring meeting and haven't got bike here to check)
thanks
Arent they the same as MTBs?
Nope. NOT the same as MTB ones.
MTB:
73mm BB - One spacer drive side, nothing non drive
68mm BB - Two spacers drive side, one on the non drive
ROAD:
No spacers needed
Road and MTB BBs are not interchangeable.
What chainset is it? Doubles don't have spacers, triples do.
Is your front mech adjustment (height and angle) absolutely spot-on? Using the correct front mech (double/triple)? 130mm hub, I assume?
Doubles don't have spacers, triples do.
The crank has a spacer, not the BB
It sits on the axle outboard of the BB
Shimano Road BB cups are 1mm wider than MTB, normally on 68mm road frame they are used without spacers, you can use MTB cups but I'd put 1mm either side. Note MTB BB also comes with a wider tube between cups which you can't use on a road frame without deforming it, they are generally for 73mm BB.
If you have clearance issues with Road cups, another mm or so spacer on the drive side won't hurt.
Of course this all depends on your chainset.
Interesting one this.....
My bike came with a crappy sq taper crank, so I bought a cheap SORA crankset from Merlin to fit. Didn't even think about axle lengths etc. and sold the sq taper crankset on ebay.
The Sora crankset has never shifted as well as the previous one did. The chainring clearance is right, it is parallel to the rings etc. but it is like the rings are slightly further inboard than they were before so the mech is almost at it's inner limit of movement. It shifts, just not as well as it used to. This is when dropping from big ring to little ring....
To see if it was just me having issues with set-up or some kind of geometry/spacing issue I put a 2.5mm spacer on the DS BB shell. And once re-set the mech shifting was improved massively.
I haven't left it like that as it meant that the splines on the NDS crank weren't fully engaged, but it was a useful test.
I suspect the axles on the sq taper BB were a bit longer than the equivalent length on the SORA crankset, resulting in the rings sitting further outboard than they do now with the SORA crank.
But, all the literature says you don't need any spacers with a HT-II crank on a 68mm shell & I can't find the original spec of the sq taper BB to find the axle length and confirm or deny my suspicion.
I am 90% sure that my 75kg weight and distinct lack of power would mean that the cranks are OK with a bit less spline engagement on the NDS with the 2.5mm spacer in, but I am not sure I want to risk it.
errmmm
shimano compact double, with ultegra double front mech
messed around with mech height and angle for hours - can't get it any better
@ peterpoddy - so there should be a spaer between the bb and the chainrings?
@ peterpoddy - so there should be a spaer between the bb and the chainrings?
No, with that set up, there shouldn't be any spacers anywhere.
The crank has a spacer, not the BB
It sits on the axle outboard of the BB
Er, yeah, I know 🙂
okay - it shouldn't have a spacer but any harm in putting a spacer in? that would be enough to stop the chain rubbing. any danger of the non drive side crank falling off???
thanks