Shimano, mixing road and grx

I've got 11 speed hydro road STIs, Zee cranks, race face 10speed ring, KMC chain, GRX mech, XT cassette, Stans Hubs.

Works lovely!

Pretty much all Shimano mechanical 11sp road and gravel is cross compatible.

The GRX chainset sometimes gets a bit specific because it sits further outboard and has a 17T difference so usually needs a GRX front mech.

However, that cassette size on the back probably won't work - far too big a range for the rear mech to handle. I reckon the biggest you'll get away with is 11-40 and even that might require a Wolftooth extender.

Your suggested option would shift but I have no idea how much chain slack you’d end up with between that cassette and chainring setup. I can’t imagine any existing rear mechs would pick it up.

Do you *really* need a 50:10 top gear? Your mileage may, of course, vary, but by my reckoning I’d be 36mph+ before even thinking about spinning out (on the logic that my 42:10 gets me comfortably over 30- I’m gearing down next time). If you’re routinely spinning along above 30mp then fair play to you!

@crazy-legs, OP said grx 820 which has a mech that can take up to 51. Even the 812 11s is generally reckoned to handle a 46 and I believe rocketdog of this parish has used it with an 11-51

The 820 is a 12-sp mech though - isn't it??

The 812 rear mech would work, I think that is rated up to 46T as standard.

Total capacity for the  RD-RX822-SGS  is 41t. With your 34/50 chainring and 10-51 cassette you need 57t so you will end up too much slack when in the smaller sprockets. I don't how much leeway there is from the Shimano stated total capacity. Basically according to spec the derailleur can only handle a 10-51 cassette and a single chainring as the difference between the smallest and largest sprocket is 41t.

Your suggested option would shift but I have no idea how much chain slack you’d end up with between that cassette and chainring setup. I can’t imagine any existing rear mechs would pick it up.

Very much this^^

Maybe close the range on the chainset a bit? Say change the outer ring so it's 44/34? Do you really expect to be pushing a 50-10 ratio when loaded up?

It's worth noting the GRX double (RX600) is normally 46/30 but intended for use with a more conventional 11-36 cassette to give finer increments, good range and minimise the amount of chain slack to be dealth with, you might stretch that to an 11-40, perhaps an 11-42(?) But I reckon closing the gap between chainrings a bit is an important consideration...

Easiest thing to try might be a goat link or similar with your existing (R7000?) Mech, and an 11-36 MTB cassette in the first instance, that 34-36 ratio could be low enough, next thing would be to try an 11-40, again might be achievable with a goat link but the double will probably start to complicate things.

I've got 40 x 11-51 on two bikes, so works well if it's 1x with no extender or extra long B screw. . 2x with that extreme of chainring will make the chain either massively too tight or too baggy so I think you'll run into chain retention or premature wear issues.

Also the Grx fro2nt mech has a wider swing than the road version so make sure you match the appropriate shifter with the mech and chainset

Even the 812 11s is generally reckoned to handle a 46 and I believe rocketdog of this parish has used it with an 11-51

Indeed

Cheers all, 

My current road bike is 34,50 and 11-32

The idea was to keep that top end for pure road riding but have a good bottom end. 

As a couple of you have suggested I'll look at reducing the range a tad and learn to man up 

FWIW I have 50/39 and 11-42T on my Amazon. That's without any sort of Goat/Roadlink. I can completely cross-chain if I desire. That's very much at the max range of derailleur capacity (beyond Shimanos published specs). I can't see how 11-50T would work. 

@scotroutes I think that is what I'll try.

Cheers again all

My current road bike is 34,50 and 11-32

The idea was to keep that top end for pure road riding but have a good bottom end.

If you're dropping down to a 10t cassette, you could drop to a 46t chainring for the same top end.

I think I'd be tempted by 46/30 and 10-42.

FWIW I have 50/39

Oops. I meant 50/34

Sorry to hijack the thread OP, but I have a Ultegra/GRX cross question as a well.
I'm looking to change my ultegra 11 speed on the Tripster to GRX to lower the gear

Also the Grx fro2nt mech has a wider swing than the road version so make sure you match the appropriate shifter with the mech and chainset

If I use a 11-36 SRAM cassette, GRX 810 rear mech (medium cage) and a GRX f810 2 x Front mech with a 31/48 GRX 810 crank and still use my Ultegra shifter and brakes will it work?

or does the wider swing means it won't work with the Ultegra shifters. (fingers crossed)

or does the wider swing means it won’t work with the Ultegra shifters.

iirc grx front mech is offset to be nearer the innder ring as its further outboard if that makes sense? (further out to accomodate the wider frame needed for gravel tyre clearance) so yes it will work but probably not as nicely as a full ultegra/ultegra pairing

@vortexracing, everything I've read says a grx chainset needs a grx derailieur, for reasons stated above.

@vortexracing, everything I’ve read says a grx chainset needs a grx derailieur, for reasons stated above.

It will have a GRX front mech and a GRX chainset its the Ultegra shifters with that set-up that I don't know will work or not. 🙁🤞

It will have a GRX front mech and a GRX chainset its the Ultegra shifters with that set-up that I don’t know will work or not. 🙁🤞

They will

They will

great 👏

I’m looking to change my ultegra 11 speed on the Tripster to GRX to lower the gear

 everything I’ve read says a grx chainset needs a grx derailieur, for reasons stated above.

I've got an old Dura-ace di2 front mech working fine with a GRX 31/48 chainset. Appreciate is a bit niche and likely won't work with a mechanical derailleur, but the Di2 mech seems to have enough adjustment for the + 2.5mm GRX/Shimano road difference