Anyone know anything about disc brakes?

I'm back!

SRAM Force AXS (D1) levers paired with my Hope RX4 calipers. Using the same Campy rotors I normally do. Insane amount of rub and way too much friction. This isn't a slight rub, but full-on hugging the rotor shizzle.

I last used these brakes on a SRAM mechanical Rival groupset with no issues - rotated between all kinds of rotors, pun unintended. Not too long ago I cleaned and lubed (Hunter's Silicone grease) every b!tch @$$ piston too. Have I 'overbled' the system?

The Campy rotors are actually a slither thinner (or maybe just a margin of error while measuring) than the SRAM centerlock rotors that were on the bike before, and they didn't rub as badly, but only slightly - I was able to ride the bike with my group telling me they can hear rub lol. The rubbing now is too consistent to indicate the rotor is bent at a given position, but I'll try to true it anyway.

Help please!

Okay... The friction isn't as bad as it was before. I did the whole "push out the pistons on one side, attach a syringe, and then retract them" and repeated for the other side. There's still loads of rub and noise, but the wheel doesn't immediately come to a stop now. Maybe that helped? I don't think it's enough though.

With these RX4s, I've always found the smaller two pistons are slower to engage. It's never, ever been even.

Open shifter port, push pistons in, close port, center caliper and brake a few times.

That's the case with most four-pot calipers; one set will always be more inclined to move than the other, as fluid takes the path of least resistance.
Lubing the pistons with Hunters silicone really helps, possibly even a full rebuild. My RX4s needed it from new, as the smaller pistons just weren't lubed enough, and got stuck. Been fine since.

Balancing the pistons - by holding the more freely moving pistons back with the opposite pad until they strike evenly and simultaneously - really helps

8mm metric open end spanner wrench

Get an 8mm crow foot wrench. The 8mm fittings on a lot of hoses are made of mild cheese and round easily with spanners in my experience. The crows foot grabs on more sides of the nut and is much more resistant to rounding the fittings. You can also get a torque wrench on it this way if you're that way inclined

https://www.ebay.co.uk/itm/193884035651

8mm flared nut spanner is the proper tool 5-7Nm is the recommended torque, so it's not much.

Tried this a couple of times. First time it felt like there was a subtle improvement.

proper tool

It does the same job and mine works with a torque wrench so you lose

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Yeah, tried the this. The brakes were working fine for me. I then had them off a bike for a good 6 months. When I then fitted them to the road bike (don't fit the gravel), I made sure to clean and relube every piston with Hunters. Individually they move quite freely and easily.

Checking the rotor and it's pretty darn true.

Did you bleed it with the pads in?

Nope, bled with the alu bleed blocks that came with the brakes - how I've always done it. Never had issues on the old Diverge with rebleeding and other servicing tasks for these calipers.

In terms of procedure, I've probably watched the Hope video so many times since I bought these calipers during covid days (2020?), that I've memorised it. At one point I got fed up and spoke to Hope both by phone and email to have them replaced. They instead sent some instructions with additional steps (not in the video) that really helped get the brakes working good.

Repeating that process hasn't worked lately. I set the RX4s up on my road bike about 3 months ago - rubbing galore, so I left them. I've bled them twice today, same issue. I feel I've spent far too much time on them today.

As an aside, I've bled other calipers (SRAM Force/Rival etc.) with zero issues too. The clearances on these Hopes is so bad.

Well nice, 5/8" though? ;)

First pic from googimages 😔

At this point, I'm thinking of rebuilding the brakes completely. I've got all the tools and even some spare parts.

What could go wrong?

Did you push the pistons all the way back in with the funnel/syringe still on the shifter? If the shifter bleed port was closed, the system is maybe over filled

Correct. Normally the syringe on the shifter/master cylinder is the last one I remove, after I've pushed the pistons back in.

I think TooTallTim's tip might have helped with over-filling.

Also, Force AXS and Rival 1 doesn't use the same caliper. I think AXS push more fluid so could be causing issues.
Hope 4 pot is rubbing festival anyways, don't know why anyone with a gravel bike bothers.

Same shifter/master cylinder you mean? The master cylinders on the old Rival 1 were quite notorious. There was also a lot of lever pull just to get the brakes biting. Didn't have rubbing issues with thr RX4s - or maybe when swapping rotors wheels - but a quick align fixed things.

On the Force AXS levers/shifters though, these Hope RX4 have been an utter pain lol. I sold my Force calipers so I'm kind've stuck.

Or I could shell 675 per caliper and rotor set, and get the new SRAM Red epic brakes!

I am exactly that way inclined. :) Thank you & everyone else for the tips, I'll just need to get my hands on a shimano compatible cheapo PM caliper and im off to go.

Setting up 12 speed ultegra calipers, the rear bolts are way too long for my frame. I have a bunch of shorter bolts but none that are shimano. Can I use aftermarket bolts or am I best tracking down shimano, specifically the bolt on the right with the little thingamijig on top

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Me: Any bolt will be fine, torque it up to spec.

Also me: Get the proper bolt if you can, the circlip is just an insurance as if it gets to that point you'll already have felt the judder way before.

Not any bolt, but a decent grade steel bolt with some kind of loctite or nyloc and a washer will be fine. You could even just chop that one down with a hacksaw.

My cargo bike has SRAM brakes. All my other bikes have Shimano.

Cargo bike has a sticky piston. Using mineral oil to lube that sticky piston is going to be fine, right?

Most SRAM uses Dot fluid, not mineral. Check yours via Google, and if the system uses Dot fluid, only lube the sticky piston with Dot fluid.