BNB

I recently bought a Trek 520 Grando 10sp to use bikepacking and bike touring. It was a budget bike and the tiagra shifting is lousy. I've gotten very used to electronic shifting over the last 5+ years. I just took my 11sp sram etap off my gravel bike so have this spare groupset ready to use ... somewhere. My main questions are:

Is there an 11sp freehub body available for the Shimano M475 ( currently 10sp) hub?
Will an 11sp chain work on 10sp chainrings? guessing not.
Will the etap front derailleur work with 42/28 chainrings?

Iride01 

A FH-M475 shows as a 8 and 9 speed freehub. Be certain that is what you have if it's currently 10 speed.
Never mind, I found this......
https://bike.shimano.com/en-EU/produ...o/FH-M475.html

You guessed wrong. My son's bike has a 10 speed Tiagra crank and front DR with everything else being Shimano 105 5800. Just use a chain appropriate to your rear number of speeds. If you need race performance shifting, then you might be a tad slower completing front shifts. But so far, neither of us can tell if it suffers.

Don't know, but usually that's a matter of whether you can get the front DR lower to make up for the smaller diameter of the rings. I've never been good at finding tech docs on SRAMS site. Since I don't have SRAM stuff, I'll let you look for that info. I'm sure it's there somewhere. Shimano makes all that info available to any at their technical document site.

sch

FWIW the Shimano 11 spd 11-34 cassette in the 700-800 series were specifically designed to be used on 8-10spd free hubs
as well as 11 spd hubs with a spacer. It is my understanding that a number of the ATB oriented shimano 11 spd cassettes
were also usable on 10spd hubs and cover larger ranges than the 11-34. Problem might be chain wrap with larger than
11-34 even with smaller chain rings and clearing the larger cassette cogs with your SRAM etap RD, though hanger extender
would probably fix that.

BNB

--First, I also find Sram tech docs difficult to find - if the one you're looking for exists at all. I'm pretty sure they would not support using the FD on 42/28 chainrings. My next idea is to go 1x; keep the 28 that's on there for low gearing. I can happily? coast downhill.

--Interesting about the Shimano 11 spd cassettes designed to work on 10sp hubs. I was hoping to use my 11-36 sram cassette (which exceeded the chain capacity and was less than ideal on my gravel bike, for sure) rather than buy a new one. I used a roadlink to get to the 36 but the chain was too long and I had to be careful to stay out of small/small. I don't mind this setup on this particular bike.

--I realize the spec on the current hub - I was hoping someone might know if I can replace the current freehub body with an 11spd freehub body.

--I am definitely not looking for race performance. I'm doing a tour with this heavy bike plus panniers.

zacster

My understanding is that 11sp road spacing is 131, not 130. They kind of snuck that extra 1mm in there since it would barely be noticeable when inserting the wheel into the frame. What that means is that the hub may be a mm too narrow to take an 11sp as cassette tolerances are really tight and the dropout may be up against the freehub. You could probably make it work though with a spacer, but that may also require a re-dish. I also vaguely recall one of Shimano's groupsets not being compatible with the others, and it may have been Tiagra. Is it worth doing vs. just buying an 11sp wheel? I know, you are trying to keep the cost down and reuse what you have. I do it myself and then end up spending more to make it work than just buying what I needed in the first place. You know you are going to need a specially splined wrench to take it off, one that only fits Tiagra, and another that only fits 11sp! (or something like that. If you ever had Campy you know what I mean.)

Shimano has a compatibility chart that shows everything but can be difficult to understand too.

BNB

I'm debating all this too - new wheel and all. It's probably not worth the cost and hassle. I worked on the tiagra shifting today ... the shop had it set up with low limit screw incorrectly set, cables have stretched, test ride tomorrow. If it shifts better then I'll probably keep what I have. I switched out the freehub body on my white industry hub to go from the 11sp to 12sp and found it was easy to do. I also found a diagram online showing this 131mm vs 130mm, so I can see the potential for problems.

thanks for your input.

icemilkcoffee 

The 11 speed hub is wider than the 10 speed hub. BUT the 11 speed cassettes with the largest cog > 34t, are dished in in the back. So it fits over the 10 speed hub.