Well, fuck me - how expensive are they!? or am i looking in the wrong place....ebay shows 30 quid for one piston - ie a caliper needs 4....so youre looking at half the price of a set of calipers for a full set...my m4's on the hyper are a little stiff so thought...piston kit...but jesus, not at that price... Edit - found the same company selling an entire set for 195.00 but even then i expected 100 quid at the very most!!
theyre marked in a few places (im thinking theyre drawing in dirt) plus they are really stiff - even after ive extended them out and cleaned them with WD40...i cleaned the HPK's on the zed just before and after cleaning i can push the pistons back in with my fingers very easily. Net result is the hypers front wheel doesnt freely spin as the calipers are not letting go of the discs...
Well, after a bit of looking ive found this...which is much more like it...just need to ascertain that theyre for the M4's https://www.reactiveparts.com/perfo...lipers-spares/brembo-piston-and-seal-kit.html
I think your jumping the gun here, Brembo pistons are very durable and last a long time. Have you actually just striped the calipers down and cleaned them first? If not then do so as you could save yourself some serious dosh. I have had Brembos and done 50'000 miles on them in all weathers and the pistons are serviceable, I cleaned and re-used the seals as they were not leaking and they were as good as new!! I cannot remember someone buying new pistons for a Brembo unless it was for a caliper that was 30 years old and rusty. M4 calipers are not that old!!
I'm in the same boat. Pistons pitted and marked and replacing them is ludicrously expensive. I was shocked. Now wondering if I can only replace some of them but wanted to do the lot for peace of mind of knowing the job is 100%. If I only do some and seals, any damage or pitting remaining will ruin the seals double quick
Do not use oil based products (WD40) to clean brake parts, brake fluid is water based, the rubber components may not react well to oil based cleaning, use brake cleaner or water, hot water works best then thoroughly dry and assemble with rubber grease or brake fluid.
Ive always cleaned them out the same way, have done for years, always used wd40 after all, its water based. Cleaned the hpk's on the zed out and theyre fine.
Well, im saying that....i remember watching a documentary about it years ago...some ingredient from fish in there too...
WD40 is def not water based, spray/wipe some onto a piece of steel then put some water on it and see it separate. Use brake cleaner spray and an old tooth brush to clean out the old dust and crud from calipers and pistons.
Looks like a job for this weekend then....ill try the cleanout first but, im not really confident that itll work....as i say...always used it on all of my calipers (WD40) and theyre all good apart from the hyper...
FYI WD40 is based on Stoddarts Fluid (a kerosene) with some light oil. You might as well be cleaning your brake parts with paraffin.
Im not actually taking the caliper apart and cleaning it out with WD - just extending the pistons and cleaning the dirt off them...if the seals are doing theyre job nothing wd based is going back into the caliper itself...
Anyway - reactive parts just got back to me....i copy and paste.... "Ive just checked and unfortunately this doesn’t fit your bike. Speaking to Brembo UK they cant actually send you the kit to fit yourself for insurance reasons (if fitted wrong you could end up with no brakes etc..) However they can fit them themselves if that’s something that you’re interested in." Have we gone nanny state where we're not trusted to maintain our own bikes anymore??
Try www.powerhouse.co.uk they do Brembo parts. If you cleane your pistons and they still don't go back easily it may be that the bores in the calipers need the seals removing and then a thorough cleanup of the pistons an bores carried out before re assembling. Done it twice this year already on old Honda and BMW, it makes a world of difference to the operation of the calipers and isn't really that much work to do.
Cheers - thats the outfit on ebay that wanted 200 for the lot. Its not the cleaning and the taking apart but more the bleeding...takes ages...
Andy, i just replced the seals on mine after 52k, all looked ok, no dirt or corrosion, seals had hardened making pistols stiff, new seals & slide in/out nicely, not bleed them yet though, seal kit £60
Might be worth a phone call? If you can get part no's then could try a KTM dealer. My guess is that cleaning up the bores in the calipers and re assembling with a smear of red rubber grease will have them working a treat. No Pain no gain.
