Will Shimano GRX levers work with cantilever brakes? Related question here but answers more about shifters.
2 Answers
If you want mechanical cantilever brakes with a GRX crank and derailleurs you can use mechanical brake road shifters.
Tiagra 4700 series shifters are compatible with with 10 speed GRX
105 (5800 and 7000 series) and Ultegra (6800 and 8000 series) shifters are compatible with 11 speed GRX.
You also have the option of using mini v-brakes with road shifters as these match the cable pull of the brake levers in the shifters. Note regular MTB v-brakes should not be used with road brake levers as they use a different cable pull.
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A mini v-brake does not match the cable pull of the brake levers in the shifters. All it does is reduce the mismatch to such a level some cyclists could consider it barely acceptable (but I wouldn't consider the setup acceptable): bicycles.stackexchange.com/questions/71954/…– juhistCommented Jan 6, 2021 at 8:38
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1@juhist This is incorrect. standard V-brakes have the wrong cable pull for road levers. Mini-Vs have the right cable pull. Commented Jan 6, 2021 at 16:18
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1@WeiwenNg Mini v-brakes work surprisingly well with normal v-brake levers. They do not often work well with road levers. I'm sure they are "supposed to" but my experience with various types does not suggest they are a good solution.– NoiseCommented Sep 12, 2022 at 10:06
No. GRX levers are only designed for hydraulic brakes. All cantilever brakes that I know of are actuated by cables.
Edit: per Adam's comment, Magura does make hydraulic cantilever-style rim brakes, e.g. the HS33. However, these pair to Magura's own flat bar brake levers. I was not aware of this fact, and I didn't consider these brakes.
In Googling the Magura brakes, it does seem like some people used them on mountain bikes in the mid to late 2000s as disc brakes were growing in prevalence but many older MTBs had fittings for V-brakes. Thus, they might have sufficient power for cyclocross. However, to pair them with GRX shifters, I am not certain that the mineral oils that Magura and Shimano use as hydraulic fluid are completely inter-compatible. Mineral oil refers to a general class of hydrocarbons, so the composition and additives might differ between manufacturers. If they are not compatible, you would risk damaging the rubber seals or other components of the brake calipers and/or the shifters. A Magura rep in 2013 swore that the fluid they used then was incompatible with Shimano fittings. I have seen people on forums say they use Shimano oil in Magura units, but I am honestly not sure I would chance it. I'm more writing this out of general interest.
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1This is a tangent, but Magura does make hydraulic rim brakes that mount to canti bosses (although they are not cantilever brakes, properly speaking). The general consensus seems to be that it is OK to mix Shimano and Magura parts. Commented Jan 6, 2021 at 17:20
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@AdamRice You know, I knew that SRAM made (now discontinued) hydraulic caliper brakes in its last generation of groupset. I may have been aware that Magura made some sort of hydraulic rim brake, but I did not realize that they fitted to cantilever posts. You are correct that Magura and Shimano do both use mineral oils as their brake fluid, but the oils are different, and Magura has sworn that Shimano oil will destroy their own seals. This could be interesting... Commented Jan 6, 2021 at 17:26
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The “Shigura” setup is not uncommon in the MTB world. Shimano levers and Magura caliper. Commented Jan 7, 2021 at 18:19
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While the magura rim brakes are incredibly powerful, they are unlikely to work with the GRX levers due to the amount of fluid required to activate them compared to a disc caliper. The fluid compatibility is not an issue if you do not wish to preserve the warranty.– NoiseCommented Sep 12, 2022 at 10:09