Shimano GRX Hydraulic brake issue….

[Yellow Saddle]

Apologies. I missed this.

Avid bike, car fettler here who’s dabbled with hydraulic systems periodically. And a mechanical Engineer by trade - so I comprehend what you’re saying.

None of which explains 2 x bikes in my fleet / 3 total in the household with Hydraulic systems - two of which took minimal adjusting to achieve zero rub ever. The other coming ‘perfect’ from new and has never been fettled since. And remains 100% noise / rub free.

From my experience it’s the one currently rubbing that’s the odd one out. Not vice versa.

I get what you say, but let's face it. There is only one reason for rub - insufficient gap between piston and disc. Whether that is via warp, out-of-square mounts, too little movement in the piston or flex. All these factors differ amongst your various bikes and there is no mystery third force at play. Car discs do rub - just jack up a wheel and spin it. You'll hear it., but not f rom inside the car.

It would be interesting if you could get your bike on top of a workbench in the normal position with wheels at eye leven and under good light. Get someone to pump the brakes whilst you look at the gap from all angles with a torch. If you can adjust it so there is a visible gap, but it still rubs, we're onto system flex.

 

[13 rider]

Would it be possible to contact the seller and get them via your LBS to agree to part of fully fund any work which sounds like should be covered by warranty ,which is obviously complicated due to buying on line

 

[sevenfourate]

Would it be possible to contact the seller and get them via your LBS to agree to part of fully fund any work which sounds like should be covered by warranty ,which is obviously complicated due to buying on line

I’d of course thought of this too. And took photos of the work being carried out last night - in readiness for being required. Let’s hope this first line of attack is the correct solution. Then I may well contact them…..