Chainsets and Bottom Brackets?

[MacB]

A little follow up here, I've decided on 135mm rear hub, 9 speed setup, XTR rapid rise rear derailler and, possibly MTB triple chainset and Ultegra 9 speed STI's. I'm led to believe that MTB front deraillers don't work with road STI's, or at least not with Shimano. I've also got the impression that a lot of the road FD's don't work so well with a MTB chainset.

Any ideas?

 

[PpPete]

I've also got the impression that a lot of the road FD's don't work so well with a MTB chainset.

Any ideas?

Certainly not designed to go together - but IME it's not at all bad if you can get the cage of the FD at the right height and angle above the big ring without fouling anything else. Works OK on my hack even though I had to mount the FD higher than ideal above the big ring, otherwise it was hitting the chainstay at the bottom before it came inboard enough to shift to the little ring.
Mind you that's on thumbies & all low end componentry - not your STI's & Ultegra / XTR level

On best bike I'm thinking of replacing the rings on my Shimano road chainset with smaller ones in preparation for JoGLE this summer. Not down to MTB size, but certainly smaller than Shimano's 52-42-30 but still planning to run it with Ultegra FD (and you old SORA STI's) I'm thinking that should work OK, because SWMBO's Tiagra FD runs an Impact Triple chainset without fuss.

 

[MacB]

Thanks Pete, I had actually seen a recommendation that the tiagra would be the best FD for the job, from the Shimano road range. I was looking at the Impact triple as well, planning a call to Spa to see what combinations they can do. If I go MTB triple I'd run a close range, say 11-25, if a tour/road triple then a broader range.

It's all becoming a bit of a pain, I had the bright idea of standardising all our bikes around 135mm hubs and 9 speed gears, with a mix and match of road and MTB components. They certainly don't make it easy to do.

 

[NickM]

My experience of trying to mate road STIs with a MTB front mech is that it is not a goer. It might (just) work when perfectly adjusted and under minimal stress on the workstand, but it won't work satisfactorily in Real Life (tm).

Shimano triple road front mechs are designed these days to work with specific chainrings. E.g.:

Tiagra 4403 - 52/42/30, designed big/mid difference (the most important factor): 10T

You can find out which numbers apply to other Shimano mechs by looking at their corresponding chainsets (the ones with the same series number - watch out, because the designed big/mid difference changes from one model year to another).

There no reason why you shouldn't use the example above with (say) 48/38/26 rings (I have a similar setup on one of my bikes, which uses an Impact chainset). The derailleur will sit lower on the seat tube, but the all-important depth and shaping of its inner plate will line up with the rings as intended. The important thing is to maintain the big/mid difference, and not to exceed the overall range (or you risk having the chain drag on the bottom of the cage when in the small ring).

 

[MacB]

excellent Nick, that was pretty much what I understood, possibly need to lower the derailler slightly, or not? I think 26/38/48 looks to be the best option, if I can't get on with STI's then I'll switch to bar end shifters. Though I have managed to get some MTB shifter pods filed out, can now get them round the drops and onto the flats

I'm keeping learning, soon I'll know enough to make a real hash of things!

 

[gavintc]

My wife cracked a crank on here Campag Veloce chainset (do not know how it happened!). I found that getting a replacement chainset to fit her old BB at a reasonable price was a struggle, so ended up getting an outboard BB and a new chainset - it actually proved to be a cheaper option. Fitting it all was incredibly simple.