RomanG

Hello,

I purchased a new Norco Search XR A1 a week ago. And during my first ride on it the following issue has been found:
At 2 highest (10:2 and 11:2) and the lowest (1:1) gears the chain rubs against inner plastic plates of the FD cage.
At gears x:2 (x < 4) the chain rubs against a metal edge of the FD.

At the LBS I was told that these issues are an inherent "peculiarity" of this Shimano groupset and cannot be fixed completely.
The mechanic tried to adjust FD position, cable tension, H and L limits - anyways there was a rubbing in some of the cases mentioned above.

It sounded very strange for me because this is a quite advanced groupset (Ultegra-grade) to tolerate such an issue. Especially because I recently tried a bike with 105 groupset and there was no such issues with it - any gear combinations (even pathological 1:2) worked without any rubbing.
So I chose to return the bike.

This is (could be) my first new expensive bike, so maybe I was too picky...
Can you please share your experience with Shimano GRX-810? Can it be a problem with this groupset, with this bike model or with this specific bike?

Thank you.

shelbyfv

Shimano anticipates rubbing in large chainring and two largest cogs. This caveat is present in the set up instructions for all current groups, AFAIK. I'm interested in your description of the gear combos. Can you provide a link that explains? It must be something new or maybe Euro? Thanks!

tomtomtom123

Description is very unclear or doesn't make sense. Assuming that a high number is an outer cog and a low number is an inner cog, it doesn't make sense that the 2 outermost cogs would have chain rub on the inner cage plate. If they did then all cogs should have rub. Are you sure you don't mean the 2 innermost cogs? It's also unclear what you mean with rubbing on metal edge. Which edge?

Does your trigger have trim index? That would solve rubbing on big big and small small (in terms of physical diameter of chainrings and cogs). Correct adjustment of FD should have no rub on big small and small big.

RomanG

Sorry, not sure I understand you.
Do you mean specifications of the drivetrain of this bike?
Here they are (I am a newbie here and cannot post links to external resources yet):The bike model is Norco Search XR A1 (2020).

shelbyfv

This is the confusing part. I don't understand what gears you are talking about. Is this some standard system to describe gearing or something you've made up?

RomanG

Your assumption is correct. I meant <rear-gear-number>:<front gear number>, (lower numbers meaning lower gears).

Sorry, I just meant - the plastic plates inside the cage. Actually at the highest ratios the chain rubs the outer plate, and at the lowest - the inner one.

Not sure. Common sense suggests that it is either the front-outer or rear-inner edge of FD. I did not want to waste too much time of the service guy who adjusted my bike - they are very busy these days. As soon as I was told this cannot be fixed I just gave up with it...


Sorry, I do not know about this.

It looks like when the H limit of the FD is increased to avoid rubbing at the highest gear ratios, the FD cage gets too outside and this causes the chain (which goes slightly askew at inner rear cogs combined with the big front ring) to rub an edge of the FD.
Perhaps I am wrong but rear-front combinations in the modern groupsets should have a good overlap and only 2 or 3 rear inner (big) cogs are not to be combined with the big front ring?

Koyote

I think the OP needs to learn how to trim the front derailleur. If that doesn't solve the issue, he needs to have another mechanic look at the bike.

RomanG

Thank you guys. I did not know about FD trimming.
Started to delve into this.

RomanG

I was stupid enough not to read Shimano setup guide for this FD model. Did not know about additional L-trim and H-trim positions. More to it - the inner resin plate is an expendable part.
This explains everything.
Thanks again!

tomtomtom123

You could also pop out the plastic protectors from the inside of the cage plates if you really need to get another 1mm of clearance, but correct adjustment of the FD with trim positions should not have any chain rub unless your have very special setup like mine, where I have a folding bike with very large seat tube that pushes the FD too far out and has a short chainstay that creates extreme chain angles. I solve this by widening the cage and removing the plastic protector from the cage plate for the fd4700. I have since replaced it with a sram yaw FD which eliminated any need for trim, is a couple of millimeters closer to the seat tube, and only needed a little widening of the outer cage plate which was made easier by the removable screw at the joint in the tail.
I continued to use my Shimano trigger shifter with the SRAM yaw FD because the pull ratio on the 4700 is much longer so I only need to adjust the limit screws to disable the effect of trim index and then I only get 2 effective positions of the FD.