Author Topic: Onirii hydraulic flat mount brakes  (Read 2427 times)

svanimpe

Onirii hydraulic flat mount brakes
« on: February 11, 2023, 11:11:27 AM »
Does anyone have any experience with these?
https://www.aliexpress.com/item/1005004992742710.html

I'm considering them for a flat-bar gravel setup. They seem quite pricey, but unfortunately, the cheaper Shimano stuff is sold out everywhere here.



coffeebreak

Re: Onirii hydraulic flat mount brakes
« Reply #1 on: March 21, 2023, 10:35:43 PM »
I guess one advantage these have is that they’re flat mount. Shimano stuff is all post mount all the way up to XT/XTR which have flat mount calipers. In current sale on Aliexpress, ZRACE version of these is $65 which sounds like a good deal.

kbike

Re: Onirii hydraulic flat mount brakes
« Reply #2 on: March 23, 2023, 08:11:44 AM »
I bought this calipers this week. If they look good I'll swap out my ltwoo brakes. 

Nothing performance wrong with the ltwoo. I just don't like how much they weight and look. Everyone weighs the ltwoo without brackets which is wrong. With flat mount calipers you can mount without brackets but ltwoo you must use brackets.

dsveddy

Re: Onirii hydraulic flat mount brakes
« Reply #3 on: March 23, 2023, 02:01:14 PM »
I bought this calipers this week. If they look good I'll swap out my ltwoo brakes. 

Nothing performance wrong with the ltwoo. I just don't like how much they weight and look. Everyone weighs the ltwoo without brackets which is wrong. With flat mount calipers you can mount without brackets but ltwoo you must use brackets.

Actually just did the same. I noticed the price on the set from ZRACE dropped to $45 for the anniversary sale. Weight of the calipers alone is supposedly 100g lighter compared to LTWOO. I suspect the ZRACE mounting hardware is also lighter. Fingers crossed!

Re: Onirii hydraulic flat mount brakes
« Reply #4 on: April 02, 2023, 04:58:37 PM »

dsveddy

Re: Onirii hydraulic flat mount brakes
« Reply #5 on: April 11, 2023, 10:28:33 PM »
Reporting back after my first ride with the ZRACE XG calipers hooked up to LTWOO RX. Did a bunch of hill intervals, about 200ft/60m elevation on each, with decently steep terrain--so you could say it's a fair test.

Nothing too interesting re: power and modulation. It's about the same as the OEM LTWOO RX brakes. Brakes generate a TON of dust though, compared to the RX. My only point of reference are Shimano XT and Sram Rival hydro brakes (the original iteration)--I would say this setup definitely has better power and modulation compared to those old Sram brakes, and approaches that of the XT brakes.

Didn't detect any brake fade. That being said, I've never experienced brake fade, I think you really need to descend a serious mountain to experience that.

These brakes are light and look sharp, but I have to say, I am disappointed by how wide they are. They are a full 5mm wider than the LTWOO RX. If you care about marginal gains, these are definitely less aero than the LTWOO calipers, and I think that's nothing to scoff at. Most brakes will hide nicely behind the fork legs, but on the XG calipers, the cylinder port stands proud of the fork's silhouette. Having an extra 5x10mm square section in the wind near the leading edges probably costs a watt or so.

Now, the weight is really the big win here. Sub 100g calipers with pads is a big deal. Haven't done a final weigh-in on the bike to see what the improvement is, but I will report back once I do.

kbike

Re: Onirii hydraulic flat mount brakes
« Reply #6 on: April 12, 2023, 10:30:35 AM »
There is a design flaw that will cause only 1 piston to move.  I also found a random metal washer floating behind one piston. No clue why it was placed there unless it was to prevent full bottoming out of the piston. Idk

As for the flaw.  The pin hole port to flow fluid to one piston is 90* of the hose.  The hose does block this port preventing equal flow or completely blocking flow.  Not seating the hose fully into the caliper was how I prevented the blockage.  This was a pain. you have to guess where the olive will compress onto the hose.  Getting the olive placed just right will stop the hose from fully seating into the caliper and allowing free flow of fluid to both pistons.

As for use only have 1 ride so far. I'm doing another tomorrow.  I had to strip my bike after the gravel race. I had an inch of sand under bb and the bb bearings were destroyed.  So I've had more maintenance than riding on that bike.

dsveddy

Re: Onirii hydraulic flat mount brakes
« Reply #7 on: April 12, 2023, 05:18:35 PM »
Awww shit. Mine are doing the same and I didn't catch it. I think I am going to send them a message to complain, this is pretty unacceptable

jonathanf2

Re: Onirii hydraulic flat mount brakes
« Reply #8 on: April 12, 2023, 05:52:20 PM »
Oh man, I think I'll keep the LTwoo hydraulic calipers and stomach the 100g weight penalty! I've also seen a few hydraulic 105 calipers for sale and thinking of grabbing those instead.

kbernstein

Re: Onirii hydraulic flat mount brakes
« Reply #9 on: April 27, 2023, 05:47:27 AM »
Has anyone tested the hydraulic calipers extensively? I popped out my GRX pistons and might need to get it replaced if I can't pull it out.
Since I can't buy a single ceramic piston from Shimano I think my options are new 105 calipers (with 10% more pad clearance) for 45€ + shipping + new hose (I can't reuse them right? I already crushed the olive), tiagra (40€ so I think 5€ for new 105 is worth it) or aliexpress offerings, I can't find the ltwoo ones alone but I see onirii and Zrace that seem to be the same, 36-40€ but that includes hose and shipping

Any advice? I think the hose will have to come from ali regardless because there's no way I'm paying 20 for just a hose from western brands

kbike

Re: Onirii hydraulic flat mount brakes
« Reply #10 on: April 27, 2023, 09:48:12 AM »
Did you push the piston out of your caliper? If so just push it back in evenly. When the piston gets pushed out it usually fine. Just takes a lot more work to bleed air out. Also just watch around the piston for oil leaking. If it is leaking you could look for the oring(s) seal (might be a square edged orings) to replace it. Don't let your pistons get damaged around the seal. Make sure no grime is on them either.

I've reused the olive. It's not a huge deal.  It can be a pain to set a barb even with basic tools.  You don't have to replace the full hose when switching. Just cut the end with a razor, knips, hose cutter, scissors. Then new barb and olive.

I'm going to do one more ride tomorrow with the onirii calipers.  I did a ride Tuesday stopping was fine.  I just want to be sure my pistons are moving and releasing evenly.  I have tons more stop and go lights for tomorrow's ride.

kbernstein

Re: Onirii hydraulic flat mount brakes
« Reply #11 on: April 27, 2023, 12:51:20 PM »
Did you push the piston out of your caliper? If so just push it back in evenly. When the piston gets pushed out it usually fine. Just takes a lot more work to bleed air out. Also just watch around the piston for oil leaking. If it is leaking you could look for the oring(s) seal (might be a square edged orings) to replace it. Don't let your pistons get damaged around the seal. Make sure no grime is on them either.

I've reused the olive. It's not a huge deal.  It can be a pain to set a barb even with basic tools.  You don't have to replace the full hose when switching. Just cut the end with a razor, knips, hose cutter, scissors. Then new barb and olive.

I'm going to do one more ride tomorrow with the onirii calipers.  I did a ride Tuesday stopping was fine.  I just want to be sure my pistons are moving and releasing evenly.  I have tons more stop and go lights for tomorrow's ride.

Long story short: it's stuck in a weird position and I can't push it back fully or take it out

Long story long for people who want to laugh at me/not make the same mistake:
I bled the rear brake last week but *really* poked my thumb trying to push the bleed block in place because there's a stupid pin inside the caliper for some reason. 20% of my thumb is still black (I'm not). Great bleed though for a first time.
I didn't want to fight the front brake while putting in the bleed block and I thought pistons would only contract if you squeezed the lever. I didn't put the bleed block (I removed the disc from the wheel and the pads of course) but big mistake, pushing in oil also activates the piston, or at least the right one. One is still in place but one fell out. I tried putting it back in but only one side pushed in properly (used moderate pressure with a plastic tire lever, nothing major I think) 
I'll take my bike to my dad this weekend to see if he can get it out. I'm hesitant about bringing it to my LBS considering it's a chinese frame and he already told me "that's what you get for buying chinese crap" after I brought him a singular wheel that needed trueing that came from a bike HE SOLD ME.
Costly mistake. Fuck you Shimano for the sharp pin.

(The bruise is on the other thumb)

jonathanf2

Re: Onirii hydraulic flat mount brakes
« Reply #12 on: April 27, 2023, 03:42:17 PM »
That sucks! I have GRX hydraulic calipers on my gravel bike and I always use the tire lever method to push them back flush, but I've never seen the pad get stuck.

I did ordered ZRace/Onirii XG hydro calipers, but I've been setting up the LTwoo hydro calipers with my R9 levers and so far they seem pretty good, I'm not sure I even needed the XG calipers (I bought them on sale for $45 USD). I think the adapter mount weight was blown out of proportion, they only weigh 13g a piece front & back, and my bike already weighing less replacing my Juin Tech F1 brakes and 105 5800 shifters. Plus the LTwoo calipers sit well behind the fork and don't really stick out on the rear, so they do seem more aero.
« Last Edit: April 28, 2023, 07:26:27 AM by jonathanf2 »

carbonazza

Re: Onirii hydraulic flat mount brakes
« Reply #13 on: April 27, 2023, 10:32:52 PM »
If you can't get it out and back in (it is possible, see on the web how a calliper is built)
Depending on the model, there are repair kits.
But a new calliper maybe the easiest and not that expensive fix.