Shimano Hollowtech BBs – is there any difference between road and MTB

I think I probably need a new BB desperately as I’ve reached a stage where I’m wondering if it’s gonna last the ride, and it’s constantly jumping gear, there’s that much movement.

So if I don’t want to lose riding time, that means LBS rather than the vast supply of internet goodies. Question is, if supply is limited, is there really any difference between MTB and road stuff. I mean, could I fit an XT BB to my road bike?

My understanding is that there less thread on the road BB’s, hense not recommended to use roadie version on a MTB.. Can’t see why a MTB one wouldn’t work on a road bike, if that ‘is’ the only difference

You would need to reuse the little plastic tube that fits between the cups (that is if road bikes need it?) as it is shorter on road (68mm bb shell) frames than on mtb (73mm bb shell), otherwise a mtb bb will be better sealed i think so probably a better option.

If I remember rightly the threads are a different length and the external cup bit is a different length too. I used an mtb on on a cx and I had to ditch the plastic inner and adjust the amount of spacers I needed. (again this is relying on memory :))

MTB cups are 1mm narrower than road cups, so will need extra spacers on a road bike, or vice-versa.

Hmmm. Not sure I fancy dealing with any potential chainline issues. Been there, done that (trying to get an FSA chainset to fit with a Shimano BB). Still not fixed 4 years later…

Might stick with a road one to be safe.

The XT will work fine just adjust the front mech to address any chainline issues. Alternatively drop into Halfords and see if they have a roadie HT2 BB and get it price matched to wiggle or CRC or something.

A chain line issue such as the chain running poorly in the middle ring while running on the bigger sprockets,cannot be addressed by front mech adjustment. If it’s gagging to derail, it’ll derail. No point in adding another problem.

If he has a MTB one lying around then as temp bodge it will get the man out on the road. If investing in a new one then get a roadie.

OK, so I ended up buying an Ultegra one. Excellent, I thought.

Can I just use this opportunity to say what a shower of shits Shimano are. Apparently they’ve started supplying their own tool/adapter, so that you can use the original tool on their now super slimline BBs (or maybe it’s just Ultegra and above?). Except the tool I have (which has fitted several Deore and Tiagra Hollowtech BBs in the past) will not fit their adapter. It very NEARLY fits. But no cigar.

Has anyone else had this?? Is it even the same tool?

As a result, my BB is only very slighter tighter than hand tight. Which is probably a good thing, as I’ve no idea how I’m going to remove it in 6 months time when it inevitably dies.

…

…and relax.

I’ve used the adaptor no problem. It’s supposed to be a neat/tight fit.

Never had an issue with the adapor , used them a few times till we got round to getting a new proper tool.
Our old workshop toll was a fsa one and the shimano adapor ring fitted that just fine.

The shimano adapor is only plastic just use a little tap from a mallet and seat it in place

I wonder if it’s a quality control thing. To be fair, I can’t remember what brand of tool I have, but it fits the BBs perfectly. Just not the adapter.

If the tool fits the old style BBs, it fits the adaptor.
It’s a proper tight fit. I had to stand on mine to get it to click on first time. That was a shimano tool/shimano adaptor.

I did try mole grips… I’ll try standing on it next time.

I’d make sure next time is before you ride the bike, if your BB isn’t fully tight then it’ll fret the threads away(both frame & BB), i’ve seen plenty of frames require expensive repairs due to loose BBs.

My took definitely doesn’t fit. Stood on it. Stood on it some more. Did a bit more standing. It finally went on a little bit, but only by shaving the plastic off. Managed to tighten the BB a bit before it slipped off again anyway.

I’ll look forward to the fun of removing it.