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I had both my front and back brakes binding tightly on the discs after a steep down hill (well, for the Downs anyway)
I do drag brakes, which may be part of the issue - because I fear dying!
It has never happened (much) before - obviously over-heating is the issue. I am assuming that the brake fluid ( being DOT 5.1) has absorbed water - and expanded, hence the brake binding.
The front was easily solved by realigned the calliper - but the rear needed some pad manipulation to get mobile again.
Both brakes have now been bled, with fresh DOT 5.1 going in.
What other issues could have caused the problem?
Last time you bled the brakes, did you push the pistons back and insert the bleed block spacer? If not, or you've topped them up, the brakes might be overfilled.
Last time you bled the brakes, did you push the pistons back and insert the bleed block spacer? If not, or you’ve topped them up, the brakes might be overfilled.
No I didn't 🙁 ( I didn't know I had to - as I have never done so before)
Off to google bleed block spacer!! (However it does make sense)
Looking at the rear discs they look a little similar to real cheapies off eBay (or rather the are SRAM pattern being used on Hope calliper). How much difference do discs make?
No I didn’t 🙁 ( I didn’t know I had to – as I have never done so before)
That'll be the issue, I had the same on mine a few weeks back after some long Welsh descents. Just fitted new pads in the rear and the tell tale sign was one piston popping out when pushing the others in, like a game of whack-a-mole! Push the other in, another pops out!
If you've not done a proper flush and bleed it's worth doing one, if fact you've reminded me that I really need to do one before I spend 2 weeks in Aberfeldy in July - the brakes will be getting a pounding there!
Sometimes the calliper seals dry out a little and that slows the response of the brake pistons. You might notice a wooden feeling at the levers. It's a good idea to periodically get the brake off the bike, remove the pads and work the lever to make sure that all of the pistons are moving in unison. If you can get a tiny bit of brake fluid around the piston seals then this helps restore the braking performance.
You will need to clean the rotors, the pad surface and the brake calliper itself with a decent brake cleaner too.
As for the rotors, you won't notice any difference as such with a new disc, unless you upsize if you can. Bigger rotors are a decent upgrade for not a lot of cash.
Yeah a tiny bottle of hunters silicon lube, a very small paintbrush and some brake cleaner is all the maintenance I've had to do on mine, as per Hope's instructions.
That'll solve any sticky pistons, along with a proper bleed/flush of brake fluid and you'll be good to go.
the brakes might be overfilled.
I’ve heard this before but Hope say you should get as much fluid in as possible - they recommend opening everything up, such as bite point adjuster etc. to enable this. You always lose fluid as you roll on the diaphragm.
I had this exact problem - turns out that it had air trapped behind the pistons. The Hopetech online video tells you how to remedy this by pumping the pistons out, opening bleed nipple & pushing them back in, then closing the nipple.
Looking at the rear discs they look a little similar to real cheapies off eBay (or rather the are SRAM pattern being used on Hope calliper). How much difference do discs make?
Your rotors are thinner than what the calipers were designed for but it shouldn't be too much of an issue, I run G2's on mine and they are fine. If you've been heavy on the brakes then they will suffer, worst I had was the snow section at MacAvalanche but they never locked, just pinged angrily at me.
As for bleed blocks and all that bollocks, I do mine on the bike using the rotor (especially on my V's as they're the wrong size as mentioned). If it was something else where you are messing about with syringes and reverse bleeding I'd use blocks but just pop a hose onto the nipple, feed it to a catch can of whatever variety and you'll be fine. It's exactly the same method as bleeding car brakes.
It has never happened (much) before – obviously over-heating is the issue. I am assuming that the brake fluid ( being DOT 5.1) has absorbed water – and expanded, hence the brake binding.
Your problem is nothing to do with the type of fluid. It's most likely that they were overfilled or you have sticky pistons/seals.
DOT fluid can absorb water if it's not stored in a sealed container. Your brake system is sealed. The idea that DOT systems absorb water is really more myth than reality. Even if they do, it won't cause the symptoms you describe.
Last time you bled the brakes, did you push the pistons back and insert the bleed block spacer? If not, or you’ve topped them up, the brakes might be overfilled.
No need for bleed blocks with Hope brakes, I've always used the method on this video, never had any problems (on e4 caliper) and they recommend getting as much fluid as possible into the system. I'd guess sticky pistons which should be sorted by following Hope's recommended procedure or contaminated fluid most likely cause of op's problems
Thanks all
I did kind of wonder how water would get into fluid in a sealed system - but it was an easy fix. As the brakes hadn't been done for ages (other than a top up the other week) it make sense to do it. And some of it was somewhat darker than when it went in.
Certainly sticky pistons could be an issue - the V4s do seem to be a little bit more sensitive that say the V2s. I have had a good brake clean for a while, so I will drop the pads out, whip the reservoir heads off, have a general piston and calliper clean and wiggle (I have both brake cleaner and Hope's suggested silicone lube).
And then I will set them up properly!
That's my evening sorted
they recommend getting as much fluid as possible into the system.
You need to make sure there's enough space in the reservoir for fluid to expand into. If you bleed the brakes with partly worn pads, you need to push the pistons back into the calipers to ensure you don't overfill them. If you do overfill them, you will need to release some fluid when you fit new pads.
I’ve heard this before but Hope say you should get as much fluid in as possible –
Yes, but if you've got worn pads in there, then they are going to be very overfilled, and cause problems when you want to get a new set of pads in there whilst out on the trail.
If you don't have a bleed block you can just use a stack of coins or washers with a wrap of insulation tape around them.
Regarding Hunters lube. It's just a generic silicone lube for plumbers to use on push fittings and the like. Any other brand will do the same job for much less than the little bottles on ebay that someone slapped a Hope logo on.
You need to make sure there’s enough space in the reservoir for fluid to expand into
I’m fairly certain fluid doesn’t expand; If you’re talking about the “expansion”caused by pushing pistons back into the caliper, this is why you use a bleed block in the first place (or any other suitably sized spacer), then as your pads wear and move towards the rotor, the “extra” fluid is accounted for with the shape of the very soft rubber diaphragm, which allows “expansion” & “contraction” (essentially the movement of fluid through system. When you roll it onto the master cylinder you lose fluid anyway (by the diaphragm shape), so there is movement either way.
Okay - sorted.
Sticky pistons was the answer!
On the back only one was moving - so now silicon lubed up on all pistons.
Front was slightly better - but not much.
Silicon lube was from a plumbers merchant on eBay!
However not a big issue for the next few days as I shagged my shoulder falling off on this morning's ride ....
😩👍🏻
My understanding of it is that when the pads run thin the exposed pistons get covered in grime and when you push the pistons back in to fit a new set of pads the crap gets pushed back onto the seals and creates friction that’s stops the pistons from retracting properly in use. Only had this issue with my hope brakes but now I make sure to give the pistons a good clean before pushing back into the calliper to fit new pads.
Once mine seized I did a calliper rebuild with a new seal kit which made properly cleaning the pistons much easier and they have moved much more symmetrically since
There’s a difference between as much fluid as possible and overfilling. If you set the pistons back into the caliperwhen you do the bleed you cant overfill them as any excess gets pushed out of the reservoir when you roll the rubber seal back on.
If you leave the pistons out then you could overfill it but if you then push the pistons in the xs fluid will likely get forced out of a seal somewhere.
By far and away my biggest issue with E4 and V4’s was sticky pistons. I Got into the habit of spraying silicon lube on the pistons every 2-3 rides which sorted it in the main but they forever had a piston or 2 that was less “free” than others and always sticky during the ride. Nothing major, but enough to bind and grind more in sloppy conditions than anyone elses brakes!
Then the best upgrade I ever made on my V4’s was replacing them. With formulas.