Sram Red disc caliper vs etap HRD caliper

Discuss light weight issues concerning road bikes & parts.
MichaelB
Posts: 621
Joined: Tue Apr 22, 2008 4:31 am

by MichaelB

mrirocz wrote:
Wed Mar 13, 2019 9:17 pm
https://sram.zendesk.com/hc/en-us/artic ... -calipers-

Quick research on SRAM's website...they don't give specifics as to why they are not compatible. It is a bitch trying to find the etap HRD Calipers. No one seems to have anything in stock.
That is absolutley a useless response (EDIT : ) from SRAM.

Even if there is something different inside the lever, it's just a system that pushes hydraulic fluid around. Unless the HRD uses some kind of magical suction fluid ......

Makes me turn off SRAM even more.
Last edited by MichaelB on Thu Mar 14, 2019 11:24 pm, edited 1 time in total.

youngs_modulus
Posts: 575
Joined: Wed Sep 20, 2006 1:03 am
Location: Portland, OR USA

by youngs_modulus

Michael, I assume you mean that SRAM’s explanation is absolutely useless. When I first read your post, it sounded like you were saying that mrirocz’s post was useless, which wouldn’t be fair.

I agree that SRAM’s answer—basically, “they’re just not compatible”—is way less than enlightening.

The brakes use the same fluid and both master/slave piston diameters seem to be the same. Given those things, the calipers don’t “know” anything different about what lever is actuating them. There may be some kind of incompatibility here, but I still can’t imagine what it is.

I have a hunch that mrirocz’s mechanic, though competent, is only saying they’re incompatible because that’s what SRAM says. From a liability perspective, I’d likely do the same in that situation. But from an engineering perspective (absent a compelling explanation of the claimed incompatibility) I strongly suspect the calipers are compatible.

by Weenie


MichaelB
Posts: 621
Joined: Tue Apr 22, 2008 4:31 am

by MichaelB

youngs_modulus wrote:
Thu Mar 14, 2019 6:32 pm
....
I have a hunch that mrirocz’s mechanic, though competent, is only saying they’re incompatible because that’s what SRAM says. From a liability perspective, I’d likely do the same in that situation. But from an engineering perspective (absent a compelling explanation of the claimed incompatibility) I strongly suspect the calipers are compatible.
Edited above post for clarity.

I'd tend to agree with your thoughts re liability and compatability.

spud
Posts: 804
Joined: Sat Feb 07, 2009 5:52 am

by spud

None of the explanations we've heard so far make any sense. I've built a track car, and the calipers are not the same mfg as the master cylinders. Lots of street cars offer upgraded calipers aftermarket. These guys definitely are not changing the master cylinders since they are tied into the antilock. It doesn't matter - as long as master cylinder is matched to piston size, it works.

They only possible thing I can think of is that return springs on the two calipers are different, perhaps forcing the piston too far back into the bore, which may possibly screw up the adjustment at the lever for bite point.

mrirocz
Posts: 17
Joined: Thu Feb 08, 2018 1:48 am

by mrirocz

Guys, the mechanic installed them and said they didn't function properly. Anyone here Wana try and replicate the install? I'm not saying that the mechanic is wrong, but maybe he didn't install correctly?

MichaelB
Posts: 621
Joined: Tue Apr 22, 2008 4:31 am

by MichaelB

I’ve installed Shimano 4 pot calipers on two different bikes (RS685 levers and Zee calipers, and then RS505 levers with MT520 calipers) with no issue whatsoever.

Even put a pair of SRAM Guide calipers (with new seals to run Mineral oil) onto a TRP Parabox without issue.

Great lever feel and brilliant modulation.

The whole ‘different caliper’ thing just screams suspect.

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