GRX Clutch Derailleur / Back-Pedal Resistance / 1x

[sfo423]

GRX mech. clutch der., GRX crank, 1x 40/42.

The bike is six months old. I assumed the resisitance was due to new build and it would 'break in.' Well, its still stiff on the backpedal, which makes me think I am wasting a lot of energy while pedaling. Shifting is spot on. Ruled out the rear hub, removed chain from crank and checked BB; crank spins freely. Jocky wheels spin freely. When I dis-engage the clutch, its spins a little better, but I do not see that as the issue.

I have an XTR clutch der on my 1x mountain bike and it back pedals very freely so I know what I should expect.

Derailleur set up? B-gap? Not sure what to mess with.

Anyone experience the same symptoms and find a fix?

[Point]

IIRC the GRX derailleur has a higher tensioned clutch over the XTR and I believe there's some way to tune this on the GRX.

[ooo]

Make sure that your hanger is straight. Can you post bike and rd pictures?
What is length of your chain stay (420,425,430) and what is width of your rear hub (OLD 130,142,148)?

Take a note on which rear cogs you have this problem.
Did you have this problem when your chain is one straight chaine line on front chainring and rear cog?
Stock 1x grx chainring have horrible 49.7 mm chain line, you can try to fix it with chainring spacers.

a) make sure chain have correct path between pulleys:
b) make sure there is no gap to hanger:
c) check your chain length:

a)


b)


c)

[Nicke]

Which GRX rd are we talking about? I have an RX800 on my gravel rig and I experience no resistance even with the clutch engaged (when the chainline is straight). And are you 100% sure the freehub isn't causing this resistance?

[sfo423]

Its a Grx Rx810 Rear Derailleur.

The chain stay is 428 and the rear hub is a thru axle DT350. The hub spins freely.

I'll double check the above but I also noticed back spin in 40/42 causes the chain to come off the cog.

[Nicke]

Then I'm not quite sure what is causing the drag. The backpedalling issue is definitely down to the chainline being too sharp. Happens to me aswell with a 1x setup.

[ooo]

rd-rx810 is optimised for 11-30/11-32/11-34 cassettes
11-40 rd-rx810 performance is not as good as rd-rx812
there is no official chain length guide for this combination (rd-rx810 + 11-40)

I still think grx 1x crank chain line is one of the more important factors,
try to reduce chain line to make chainring as close to the frame as possible

[sfo423]

Problem solved (minus back pedal on 42t and chain falling down the cassette). Not really worried about that.

I looked at my reciept again and I was upgraded (or simply swapped out) from a 810 to an 812 derailleur. Regardless, the chain was running under the prevention plate (not the pin as on the 810). Oddly, there was no 'sound' that would indicate such chain drag.

BTW; running 115 links + the connector.

Good news; I am much stronger than I thought! I'd post a pic but that seems no longer available.

[Nicke]

Glad to hear you sorted it