My PX Tempest came with Fulcrum 900db wheels and broad gravel tyres. I swapped the Ultegra 11-34 cassette for an XT 11-40 to lower the bottom end. I used the same 1mm spacer and indexed the rear mech accordingly.
I've now fitted the spare Ultegra cassette and a 1mm spacer to a pair of Fulcrum 500db wheels with narrow road tyres. I think this is as it should be but the cassette spacing is visibly different from the XT on the 900s. So, pretty sure the XT will need re-spacing.
I want the cassette spacing on both wheels to be identical for easy wheel swaps.
Google makes various suggestions about fitting an 11sp MTB cassette to an 11sp road hub.
A) Use a 1.85mm spacer to compensate for the narrower XT cassette.
B) Use 1.85mm and 1mm spacers together, as the Ultegra is also using a 1mm spacer.
C) Use a 2.5mm spacer as there's 1.5mm difference between road (38.1mm) and mtb (36.6mm) cassette widths at the splines. I'm aware this doesn't take account of the increased indent of the large riveted sprocket on an mtb cassette. The mtb freehub mount may be narrower but the sprocket width is almost the same due to the longer mtb spider.
A, B, C or something else?
Thanks in advance.
Option A, as far as I'm aware mountain bike cassettes require a 1.85mm spacer to bring the spacing into alignment with a road cassette. I've never used a 1mm spacer with an 11 speed road cassette.
I have a similar question I’ve fitted an xt cassette 11 x40 to kinesis crosslight wheels. No spacer but the chainline is all to cock now do I need a spacer? I have another set of wheels with an ultegra cs cassette 11-34 MTB hubs No spacer and all fine. The road cassette I took of before the xt cassette went on was also fine.. confused now
I want the cassette spacing on both wheels to be identical for easy wheel swaps.
You might be unlucky even of you get the spacing sorted - there's a chance the hubs may be slightly different anyway, or enough to mean a small amount of adjuster twiddling between swaps.
Neila - Option A, just using the 1.85 spacer, might not match as I needed to use a 1mm spacer to tighten the Ultegra cassette on the other wheels. I tried fitting it without but it remained loose despite the lockring being tight. Most 11 speed road hubs don't seem to need spacers for 11 speed road cassettes, not sure why Fulcrum are different.
fenboy - You will need a spacer. How wide? dunno yet!
breatheeasy - I purposely chose Fulcrum 500s to match the 900s I already have. They are both current era 11 speed road hubs from the same manufacturer. I'll be a bit pee'd off if they don't match!
Most 11 speed road hubs don’t seem to need spacers for 11 speed road cassettes, not sure why Fulcrum are different.
But an Ultegra 11-34 cassette is not like other 11 speed road cassettes. It is designed to fit a 9 speed freehub body by dishing the 34T sprocket. If you fit it to an 11 speed road freehub body then you will use a 1.85mm spacer. If you wanted to fit an XT 11 speed cassette to an 11 speed road freehub body then you should also use the 1.85mm spacer.
IIRC all the 11-speed 11-34 road cassettes require the included spacer, if fitted to an 11-speed hub, no spacer on a 10-speed hub.
I currently have the 105 HG700 11-34 on my Fulcrum Racing Sport 77 DB and Hunt Aero Light Disc, both with the included spacer behind the 34T. They replaced an 11-32 on both, which didn't require a spacer.
Ah, so an 11 speed Ultegra 11-34 is essentially the same width as an 11 speed mtb cassette?
That's correct.
Seems it is...
Thanks folks, that should make life way easier. I'll just fit 1.85s to both rear wheels and drop the 1mm spacers. That will also allow fitment of a smaller, un-spaced, road cassette in future if required.
It's possible I had to tweak the rear mech because I'd also fitted a wider GRX chainset and front mech at the same time, slightly altering the chainline. Doesn't take much to confuse me...
Thanks again.
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thanks too, i checked my ultegra 11-34 cassette and it has a spacer (1mm) so will fit one to the xt cassette, then try 1.85s if it doesn't work!
like you also discovered the GRX chainset has an increased q factor and the ring is spaced 2.5mm further out whihc doesn't help either. thanks for info and for letting me piggyback on your post. cheers
No worries. Shimano don't like to keep things simple. All 10 speed road cassettes are the same width, except Tiagra 11-30 and all 11 speed road cassettes are the same width except Ultegra 11-34. You couldn't make it up.
11 speed road cassettes are the same width except Ultegra 11-34
And 105 11-34, which is the same as the Ultegra one.
LOL, so if it is a road cassette with an alloy spider it's actually an mtb cassette?
No.
Doh! I give up.