Ultegra or 105 brake calipers compatible with GRX?

Everything I’ve found seems to indicate that it’s ok to mix and match, but nothing specific to these components.

Building up a new bike like Johnny Cash’s Cadillac and the last piece of the puzzle is looking to be the brake calipers. If I want to actually ride the bike sometime this year, I most likely have to forgo the 810 calipers for now, but I can find Ultegra and 105 fairly easily.

I am running Ultegra calipers with GRX Di2 levers.  Work fine.  I'm pretty sure that 105 are the same form factor and should work fine as well.

mtbnut87 wrote:I am running Ultegra calipers with GRX Di2 levers.  Work fine.  I'm pretty sure that 105 are the same form factor and should work fine as well.

Shimano’s web site says the components can be mixed and matched, but now that I hear someone else has guinea pigged it for me, I feel better. 😝

Thanks!

Indeed you can mix&match all road hydro calipers with road levers. You can even connect road calipers to MTB levers, did that recently with some grx400 calipers when converting a gravelbike to dropbar. It still brakes very well. 

Thijsvanderwal wrote:Indeed you can mix&match all road hydro calipers with road levers. You can even connect road calipers to MTB levers, did that recently with some grx400 calipers when converting a gravelbike to dropbar. It still brakes very well. 

I have even considered trying a set of 4 pot XT calipers and a 180mm rotor with my GRX levers...  I bet they work just fine.  We used to mix and match calipers and master cylinders on race motorcycles all the time....    the ratio of MC bore to piston area dramatically affects feel and power.

mtbnut87 wrote:

I have even considered trying a set of 4 pot XT calipers and a 180mm rotor with my GRX levers...  I bet they work just fine.

The old school ones with the braided lines?  I still have a set of those lying around! I’d still be using them on one of my bikes if “some idiot” hadn’t stripped one of the bleeders….

TwoWheeler wrote:

The old school ones with the braided lines? 

I was thinking of these.... 
 

I wasn't aware that Shimano used braided lines. 

mtbnut87 wrote:

I was thinking of these.... 
 

I wasn't aware that Shimano used braided lines. 

oh yeah, early 2000’s. (I think they may have been re-badged Hopes)

 

Assuming hydro because GRX is hydro only: Can confirm from experience Ultegra 8K and GRX 810 brifters/calipers are interchangeable. They also use the same pads. 

Thijsvanderwal wrote:Indeed you can mix&match all road hydro calipers with road levers. You can even connect road calipers to MTB levers, did that recently with some grx400 calipers when converting a gravelbike to dropbar. It still brakes very well. 

I am not suggesting it can't be made to work, but Shimano specification does not allow to mix & match all hydro callipers with all brake levers.  Below is the official matrix of compatibility.  (for example the new series Ultegra and Durace brake levers are only compatible with the new series callipers.)

This matrix also confirms that the GRX levers will work with 105 7xxx and Ultegra 8xxx callipers (including the latest series Ultegra).  Be careful for older non-series callipers as these are not all listed as compatible.

 

https://productinfo.shimano.com/#/com?acid=C-456&cid=C-737

You are correct, I should gave said you can’t use road levers with MTB calipers, only the other way around. See for example https://www.bike-components.de/en/Shimano/SLX-BR-M7110-Disc-Brake-J-Kit-p83046/

pkram wrote:
 Be careful for older non-series callipers as these are not all listed as compatible.

Ah someone who speaks Shimano! 😉

Good point. If I end up using what I can find, instead of the 810’s, I’ll have to remember to check the part number against that chart.

mtbnut87 wrote:

I have even considered trying a set of 4 pot XT calipers and a 180mm rotor with my GRX levers...  I bet they work just fine.

I've just fitted Hope 4 piston RX4's to GRX600 shifters. Didnt notice the increased power until I used the road bike with DA 9170 and then jumped back on the Hopes. Really nice modulation, though less gap between the pads and the rotos, so I will not be wheel swapping on these. 

widerisfaster wrote:
I've just fitted Hope 4 piston RX4's to GRX600 shifters.

Here I was thinking I might have to “settle for 105’s or Ultegras” if I couldn’t get the GRX810s….and now you’ve got me thinking….🤨

Reasonably priced upgrade, but if you need calipers, it's a no-briner. It also represents a chance to add a pop of color and individuality to your bike.

TwoWheeler wrote:

oh yeah, early 2000’s. (I think they may have been re-badged Hopes)

 

I thought the original XT ones (rebranded hopes or formula's or something) were brake fluid and not mineral oil calipers. So they wouldn't work with newer (like 2002 or newer) mineral oil Shimano levers. 

ridinggravelkiwi wrote:

I thought the original XT ones (rebranded hopes or formula's or something) were brake fluid and not mineral oil calipers. So they wouldn't work with newer (like 2002 or newer) mineral oil Shimano levers. 

Nope - mineral oil. Different mount, though.

To be clear, the above discussion applies for the 11-speed Shimano parts (Dura-Ace, Ultegra, 105, GRX). But...

The new 12-speed Dura-Ace & Ultegra have changed (improved?) the brake caliper & pistons to provide more clearance between the pads & rotors to reduce rub with a slightly out of true rotor. IMHO the precise clearance between rotor & pads of disc brakes has been an issue since the first disc brakes came out.  The additional clearance should also make it easier to swap wheels without having to realign the calipers.

NoCoGreg wrote:
The new 12-speed Dura-Ace & Ultegra have changed (improved?) the brake caliper & pistons to provide more clearance between the pads & rotors to reduce rub with a slightly out of true rotor.

NOW you tell me….after I’ve already ordered 105 calipers…😉 Yeah, I’ve sometimes had clearance issues and given that the GRX are “servo wave” levers, I think a little extra clearance is “affordable”.