Hi folks. I'm building up a gravel bike with 2 x transmission. I'm using grx shifters with a grx 46/30 chainset and an 11/34 cassette.. my question is.. can I use a 105/ultegra rear mech or does it have to be grx?
Thanks
A 105/Ultegra will work fine so long as its capacity is suitable for the 34t cassette. Only the front mech is different for GRX.
I'm using an Ultegra mech on a 40T cassette - with 50/34 chainring - so I'd say you'll be just fine.
GRX rear mech has a clutch to assist with chain retention. Can be switched off for road use / servicing and back on for gravel if required.
Bar that you are good as said above.
Aye, good point. My Ultegra has the clutch too.
@scotroutes what ultegra mech are you using? I was going for the R8000 but I thought it would only cope with a 34t cassette..
If it has a clutch it'll be the RX800 Ultegra.
By all accounts, the GRX has a better clutch than the RX800, so if you're choosing between them and cost is negligible, go for the GRX.
Surely you only need a clutch if you were going to be running 1x. I have never dropped a chain on my gravel bike running regular Ultegra 2x
I was going for the R8000 but I thought it would only cope with a 34t cassette..
Both the R8000 and RX800 will cope with a 40T cassette.
Surely you only need a clutch if you were going to be running 1x. I have never dropped a chain on my gravel bike running regular Ultegra 2x
The non-standard setup is a bit prone to chain slap. The mech is, after all, working outside its intended range. The clutch seems to improve it.
