So I re-routed it wrong, now it works…why?!? STW enlighten me please…

installing and setting up a GRX RD-RX812 derailleur on the gravel bike, 40t up front, 11-42 at the rear

Routed the chain correctly, shifting fine, chain line(s) fine but…

from the 32t to the 42t rear sprockets on the cassette the chain sits on and rubs the derailleur cage

making adjustments on the limit screws and the b screw doesn’t seem to solve the problem

i rerouted the chain (wrongly) to bypass (most of) the cage and everything is lovely, shifting spot on, chaineline still good, no rubbing

STW…I can’t work out why, enlighten if you can…

Pictures are after rerouting the chain wrong and to show where is sitting / rubbing when routed properly

I have a feeling your right is actually wrong, making your wrong right..

Unless theres something mega obvious I’m missing!

Youve routed it right (Now). GRX doesnt sit in the cage, it sits like you have it. Best picture I could find on the interwebs in the 5 seconds of searching I did; https://www.bikeradar.com/reviews/components/groupsets/shimano-grx-review

You have routed the chain correctly now

Wot he ^ says. Those photos show the chain routed correctly through the mech/cage.

Well that’s embarrassing, the very answer I feared / suspected several times over…

Note to self, read the damn instructions or google next time

Thanks all for clearing that up

Bit off-topic,  it I would run a chain a link longer.

What I was going to say, chain too short

Thanks also for the heads up re the chain

this was the first time attempting this for myself so unsurprised mistakes were made

when sizing the chain I was following this here picture from the park tool website,

looks like I need a new chain, can anyone advise where it SHOULD have been cut?!

See the section below that image on the Park Tools chain sizing page, “methods for drivetrains with large rear cogs”; you want four extra rivets, not two. (Two rivets is for “rear sprockets a maximum of 36 teeth or smaller”).

So don’t just read the instructions but read to the end of the instructions 😂

Thankyou for that @infovore maybe should read these things before goof image searching and deciding, “yup! That looks right”

new chain ordered, let’s see if I can get it right second time around

@avdave2 not once but twice ha ha

These things are pretty robust, but four links too short might be too many. (I managed to get my chain 1-2 links too short recently by dint of not having a sharpie I could see when I drew on the appropriate link. But it seems to be OK, big-to-big. I think yours is pushing it though, and chains are cheaper than new mechs…

Use an extra quick link, no need for new chain.

@infovore from what I SHOULD have done to what I actually DID do, does that not make my chain 2 links too short?

have ordered a new chain anyway just to get it right where it should be

at least I know how to route it properly now ha ha

Use an extra quick link, no need for new chain.

I did wonder this but am all out of 11sp quick links