Shimano GRX400 caliper piston defect - Replacement options?

Hi all,

I have a brand new 2022 Giant Revolt Advanced with GRX400 brakes and the rear brake is rubbing considerably. My bike shop tried everything to align the caliper and were not surprise as they’ve had multiple customer with issue with the RX400 calipers as they piston apparently do not fully retract. Tey would normally replace the caliper with Tiagra but they’re not available at the moment. I do have an option to buy new Ultegra calipers and I was wondering if someone knows if there’s a difference between GRX calipers (RX400, RX610, RX810) and their road counterparts ? I know they’ll be compatible but is there a difference like better disc clearance with GRX compared to Ultegra? Basically I just want calipers that will work at this point.

Thanks for your input!

4700 series Tiagra, GRX Calipers, R8000 Ultegra, R7000 105 - all compatible calipers.

I’m running Ultegra calipers on my gravel bike and they work great…no issues.

I can’t speak directly to the calipers, but some of the GRX 800 stuff is basically the same as Ultegra badged stuff. The mechanical GRX-810 shifters are the same housing / body as Ultegra, just with a different blade design. It would not surprise me if the GRX calipers are essentially the same as Ultegra ones.

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Magura also do compatible flat mount calipers. More expensive but do also have a bit more pad clearance, I know their MTB rotors are thicker than Shimano so might need new rotors sooner.

Hope also do flat mount gravel ones which are awesome colours.

Both options are definitely more expensive but you might get better chance of getting hold of them.

Thanks all that’s great info. I think I’ll go for the Ultegra calipers (no other choice anyways, thanks part shortages!). Good thing is that there’s only about a 20$ difference between Tiagra calipers and Ultegra one.

I actually heard something similar: that all the GRX brake calipers are the exact same.

I just noticed today that the stock rotors on my Revolt are misaligned vertically or simply out when the wheel spin they are significantly moving up and down. My other bikes do not seem to have this issue and I’m wondering if the rotors bolt hole are misaligned or do not interface properly at the hub. They are 6 bolts disc for reference. I’m wondering if my issue are not the calipers but bad rotors. Has anyone ever seen something similar?