Trying to get some hope Rx4 pistons to play nicely. Followed to Hope vid but used silicon spray lube as cleaner and to lubricate. Pushed pistons back centralised calliper to disc, pads in, pumped brake and it drags like a bastard. The pistons are not all coming out equally.
I’ve got some Hope discs coming as the shimano one look like the braking surface isn’t wide enough.
Should I put new pads in when the discs come- current ones have plenty life but a bit uneven.
Should I use the brake fluid as a lube or buy some silicon grease?
Any other tips please.
These are the road 4 pots btw.
I always suggest using brake fluid, whatever type is inside the caliper, to clean pistons.
I remove the caliper from the mount/disc.
Remove the pads.
Gently pump the lever to drive out the pistons - not so far as they fall out!!
Then rub brake fluid all over the cylindrical part of the piston.
Clean the pistons with a bit of lint-free cloth and then push them back in.
Repeat until ALL are 'playing nicely'
Grease can cause problems, SRAM tell you not to use their DOT grease on SRAM pistons and seals https://www.sram.com/en/service/articles/Hydraulic-Brake-Grease-Formerly-DOT-Grease
Different products, I know, but Hope have always been helpful with technical Qs IME
I use the hope silicon lube that hope recommend.
Dab a bit on each piston with a cotton bud and push back in. Repeat if piston is still sticking.
I use the Hunters lube linked above. I generally pump the pistons out a bit, clean with a toothbrush and warm water, then use a little craft brush to put some lube on. Push all four pistons back and then work them them in & out individually with an r3pro tool till they're all moving nicely.
However, my experience with my E4's is that once the rotor is to thin, the pads won't retract properly. New discs sorted it both times.
I always suggest using brake fluid, whatever type is inside the caliper, to clean pistons.
+1
Although I'd suggest clean them with brake cleaner and rag, then swab with a cotton bud of fluid. You don't want them swimming in gritty fluid after the first ride.
Never had much luck cleaning sticky pistons. Usually end up just replacing hebpistons and seals and they feel like new again.
Thanks all.
I’ll prob use the mineral oil as I have already.
Dab of dot fluid and dental floss.
Dab of dot fluid and dental floss.
Don't do this if your brake uses a Mineral Oil for brake fluid. It'll bu66er up the seals in no time at all.
Never mix DOT and Mineral Oil :o)
Don’t do this if your brake uses a Mineral Oil for brake fluid. It’ll bu66er up the seals in no time at all.
Never mix DOT and Mineral Oil :o)
I think that's why they recommend silicone oil/spray, it's usually compatible with both (it's the same stuff as in the stuff you spray on fork/shock seals to make them nice and slick, and DOT5 is silicone based and compatible with DOT4 /5.1 seals).
Thanks so mineral oil is okay on Shimano set up with Hope callipers.
Will all four glide out together when it’s properly done or are they always a bit different when pads are out?
Had go with mineral oil. All the pistons move but not all the same amount and the pads still rub, I’ll probably wait till the new discs arrive and I’ll stick fresh pads on, and keep the part worn for emergencies, and start again with the set up.
I thought that mineral oil attacks the seals on DOT brakes and vice versa?!!
There needs to be some friction in order for the piston seal to flex when the brake lever applied, and flex back when the lever is let go, so the piston moves towards the rotor, and then back again. Silicon oil is super slippy so maybe the pistons slip forwards too easily through the seals and cause the dragging.
Sram say to just clean with Iso (or did last time I watched their internal videos. Shimano say use their mineral oil, which is still less slippy than silicon. Setting the pads a little further away from the rotor when adjusting the brake can also help. These are a bit of a faff and I normally use something else, but the idea is sound:
https://www.birzman.com/products_2.php?uID=2&cID=4&Key=133
Methylated spirits and a toothbrush here. No lube because it is the seal drag that causes the seals to flex, which is what retracts the pistons. More seal drag equals more piston retraction.
Methylated spirits and a toothbrush here.
Same here, when I run out of vodka. Glad I don't smoke anymore as it could cause some issues I guess...
If you're struggling, don't fanny about exposing pistons a little bit.
Rank your pistons 1 to 4 in terms of retraction. Strip the caliper and clean everything with IPA. A drop of Hunters on your fingers and wipe it on the seals, not to lube them but just to help keep them supple. It's the tiniest bit needed.
Reassemble remembering which seal and piston combo was 1 to 4. Put the best two opposing each other and the worst two opposing each other (unless they're two different bore sizes) then the best go on one side with the worst in the other. They might creep with time but it's an easier fix than trying to stop it rubbing with a lazy inside top and outside bottom.
Oh Jeezuz
Went for a longish ride yesterday, felt pretty battered, rear brake dragging still. Meanwhile rotors arrived, fitted new(ish) hope rotor, and new pads, spin the wheel and it actually went round more than twice. Seems much better although you can hear the pads touch the disc a bit it can’t be much. Hopefully that’s sorted. Thanks for all the suggestions and tips.
Follow up- new Hope discs, cleaned and lubed pistons with mineral oil (shimano), bled brakes, new pads, centralised calliper and pistons as per Hope instructions.
4 days in the mountains, from Nice to Verdun Gorges and back. The brakes were faultless, easy one finger braking, more than enough power and no over heating and no dragging at all.
Unfortunately this means I have no excuses for being so shit up the 19,000ft of climbs over 220 miles. I was awesome on the descents obviously.