RefRick

Can anyone specifically tell me which brake mount adapters I need for a build I am working on? My LBS originally handed me 2 unbranded brackets which do not fit, then ordered the wrong set for me. Please let me know if any additional information is needed from me.

I am building on a Velo Orange Pass Hunter frameset using Shimano GRX 810 Series components. The frame has an ISO/flat brake mount. The calipers are post mount. I am using 160mm rotors. The front caliper came with a flat mount adapter which instructs which end to install upward based upon your rotor size. The rear caliper has no adapter installed.

The Pass Hunter frameset specifications are available on the Velo Orange website if needed. I attempted to post photos but have not posted enough to be eligible to post a URL.

dsaul

I hate to be the bearer of bad news, but your frame and chosen brakes are not compatible. The frame has an IS brake mount and all of the GRX hydraulic brakes are flat mount (post mount is a different thing). There is only one company that I know of that makes an adapter to make flat mount brakes work on an IS or Post mount frame and they are currently out of stock. https://www.assolutions.ca/shop/adap...-for-is-frame/ They are also not compatible with all frames, so you would need to print out their diagram to make sure there are no obstructions on your frame and/or fork that would prevent their adapter from working.

Your best bet would be to swap the flat mount GRX calipers for some Shimano post mount calipers. Shimano still makes MTB calipers in post mount and most of them would be compatible with the GRX levers.

RefRick

Thank you. I will take a solution even including bad news at this point! This is my first time installing hydraulic brakes and I have been pulling my hair out.