Sram Red disc caliper vs etap HRD caliper

Discuss light weight issues concerning road bikes & parts.
MichaelB
Posts: 729
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: 587
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: 729
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: 873
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: 729
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.

mlee6050
Posts: 3
Joined: Thu Feb 27, 2020 3:45 am

by mlee6050

mrirocz wrote:
Mon Mar 11, 2019 1:28 am
I am in the same situation. The normal Red caliper will not work with your ETAP shifters/Levers. You will need to buy the 'HRD' version of the caliper. I found this out the hard way.
They should work fine, the main difference is banjo fitting for red is at lever, for etap it at caliper, basically if use etap lever and red caliper should be like my mountain brakes that have compression fitting each end, other way need banjo

Note this is my thought I not mixed them yet, red on my road bike and etap is on my recumbent

User avatar
Alexbn921
Posts: 438
Joined: Wed Apr 10, 2019 6:39 pm

by Alexbn921

Yes they will work. Lever feel might be slightly different, but it won't be a problem. I've swapped various calipers and levers between Shimano systems and it’s a simple leverage change in some cases.
Hell you can use Hope calipers if you want on both systems.

HaroldC
Posts: 179
Joined: Mon Oct 18, 2010 2:21 am

by HaroldC

I have a full Red eTap HRD group with post mount monoblock calipers that I will be installing onto my Allez Sprint frame. I purchased the Red AXS HRD flat mount calipers and will swap those out. I know the post mount calipers used banjo fittings and the new 2 piece AXS calipers are compression fittings. I have confidence that they'll work. I don't know the piston specs, but they cannot be off that much to throw off the master cylinder that much.

My background is that I have installed many brake systems on cars, including upgrading to larger 4 and 6 piston calipers using the OEM master cylinder. Yes, the pedal feel is different, but so long as they're close, they'll still work fine.

Gerben321
Posts: 18
Joined: Tue Mar 17, 2020 11:20 am

by Gerben321

Interesting thread. I was actually wondering about something similar. I can get two Force eTap shifters for cheap (cough, 380 bucks), but I currently have a full Apex 1 set with Apex brakes. They're fine and I recently replaced the pads, so why bin them? I asked SRAM whether I can fit Force Etap shifters and make the brakes work, and they said it will physically connect, but it won't function properly and safely. This is what they said about it:
No, unfortunately that is not possible. Physically you can connect the Apex callipers to the AXS shifters although you have to shorten the pipe a lot because the connection on the shifter is different.
However, the ratio between pistons in brake lever and calliper is different with the Apex brakes than with the AXS brakes, so the brake is not reliable, so do not be dangerous !!!
But when I read the posts from some people with experience here I'm like wtf is this nonsense? What's smart? I either buy 2 shifters for 380 bucks, or buy 2 new shifters including callipers for 580 bucks. It's a 200 euro difference, but obviously safety and reliability is important here.

edit: SRAM USA also answered my mail and told me it's unsafe to do because of an other leverage ratio.

Post Reply