ZRACE XG2 CALIPER DOT FLUID SWAP

[ZacItaly15]

Dear all
as you may know, the Zrace XG2 caliper are only available in mineral fluid options...but I want to install on a Sram Apex groupset.
So, I discover via youtube the inner piston of Zrace is 22 mm diameter

What do you think to swap the inner seal from mineral to dot (22mm standard seal I hope to find...) ?

[Sebastian]

Not sure if that works. In theory it’s only the seals that make the difference. After all Hope do their calipers in both versions. I’d be very interested in your experiment. Let me know if you try it.

[DavidG]

Interested to hear how you get on. I bought these same zrace calipers myself but a SRAM Rival AXS in the bike.

[ZacItaly15]

I have a written confirmation by Hope you can swap the seal and convert Hope RX4 / RX4+ (and I suppose all the hope caliper)
So, I suppose the only impact of DOT / Mineral is in the seals and not in the piston or body

Zrace use the same Shimano piston (100% compatible) 22mm but i'm struggling to find 22mm DOT seal. The closest are the 21mm DOT by Sram.

[glepore]

If its an oring seal, plenty of epdm orings available. https://www.google.com/search?q=epdm+22mm+oring&rlz=1C1CHBD_enUS854US857&oq=epdm+22mm+oring&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigATIHCAIQIRigATIHCAMQIRigATIHCAQQIRigATIHCAUQIRiPAjIHCAYQIRiPAtIBCTc0OTZqMGoxNagCCLACAfEFon3VMmHWPO4&sourceid=chrome&ie=UTF-8

Epdm is DOT fluid compatible.

[Sebastian]

No, it's not just a simple O-ring. At least not in Sram's case. Take a look at their piston service kit. The seal is more like a rubber washer with flat edges. The seal is actually pretty important for correct pad retraction. It's the only thing pulling the pistons back into their zero position after you released the brake. So I don't think an O-ring would work.

Now obviously I have not taken the ZRACE calipers apart. So I dunno what's in there.

[Sebastian]

The seals for Hope calipers have a flat washer-like shape as well

[glepore]

22.5 here:https://brakecrafters.com/collections/motorcycle-brake-caliper-seals
There are a couple others but it'd help to know the bore diameter. Tons of silicone 22mm seals on ali that are allegedly "motorcycle" which is dot, but supposedly silicone isn't dot resistant.

[ZacItaly15]

of course, they are called quadri-ring due to the not-toroid shape. But I'm pretty sure that any DOT compatible seal can works
https://it.aliexpress.com/item/1005005666514186.html?pdp_npi=4%40dis%21EUR%213.30%213.30%21%21%213.33%213.33%21%4021011b4917386956159962231d1170%2112000033947668161%21affd%21%21%21&dp=EAIaIQobChMIgo6bjeXKiwMVS52DBx0SuyH5EAQYBiABEgK8dfD_BwE&gad_source=1&gclid=EAIaIQobChMIgo6bjeXKiwMVS52DBx0SuyH5EAQYBiABEgK8dfD_BwE&aff_fcid=5ad4e774f4c141b89d412fc9db9ec4e1-1739798136171-06384&aff_fsk&aff_platform=api-new-product-query&sk&aff_trace_key=5ad4e774f4c141b89d412fc9db9ec4e1-1739798136171-06384&terminal_id=577d47f5d55f4262999ba78823360f92&afSmartRedirect=y#nav-description

here I found a 22mm inner diameter , but I'm not sure about the external diameter.
I just did some maintenance to my motorcross bike caliper and I know how this stuff works

[glepore]

Again, be careful of silicone seals with standard dot fluid...they're not compatible.

[ZacItaly15]

Yes definitely.
That's why I'm looking for automotive/motorbike application seals.
I'm aware the rubber softness, temperature profile etc etc may be far different from long lasting automotive needs and recreational cycling use