Noticed today that while stopping at slow speeds the front brake feels like its grabbing ( as if im engaging and disengaging the brake, but not as violent) Am i looking at warped disks? If so where is the best place to buy? Ps. The bike is running brembo carbon ceramic pads if that makes any difference
Could be a warped disk or a sticky piston. I stripped and cleaned my calipers on Friday. Pistons out, cleaned and copper slipped. The amount of crud in there was horrendous. Used all of my cleaning skills and the wife's toothbrush to get the Pistons free again [emoji6]
My method is as follows. Get 500ml of new brake fluid. Remove the 4 bolts holding the callipers to the disks. Place bin bag over front tyre (or you won't want to ride it after). Squeeze lever until first piston comes out completely. Clean and copperslip piston Replace piston and cable tie in so that it can't come out. Top up fluid in master cylinder Repeat steps 4-7 until each piston has come out. Bleed Cable tie lever back overnight.
Quite possibly it's due to cementite build up. This can occur when the brake is held on to a hot disc and pad material burns into the surface. It results in an even friction around the disc with the same feel as a warped disc.
When you say "until piston comes out completely" you mean just before falling off or all the way out, so the brake fluid starts dripping? I've read that it's very difficult to put the pistons back in the caliper.
I did it until it fell out into the old washing up bowl I was using. Best way to ensure you clean the whole thing and that you don't still have grit and dirt at the bottom. You don't lose that much oil unless you tip the calliper, and they aren't that difficult to get back in. As long as it's square on, it slips right in.
As I said, I did this Friday evening. I spent longer bleeding the system than I did trying to get the pistons back in. Only one went in wonky and took me 3-5 mins to get back out.
Depends how bad it's got. If you catch it early enough before the cementite process has properly got going you can scrub it off with emery but once it's gone to far there is little you can do. Home autotrackdaymonthly.com - The Final Word on Brake Vibration and “Warped” Rotors
Thanks for all the advice, gave the calipers a good clean yesterday along with the disk bobbins for good measure, then took a ride to chris at cjs today and brakes feel pretty much the same. Going to take the pistons out this weekend for a deep clean and get some emery cloth for the disks, then hopefully i wont have to fork out the £400 odd for new disks
If you were a bit bloody closer i'd help you clean the pistons! I'm sure your disks will be fine. I had a bloody awful groaning when hard braking and cleaning my pistons cured that too.
Right so i ordered a few bits today and decided to go all out and get a replacement seal kit to rebuild the calipers completely as i noticed the top inside piston is sticking quite badly on both sides, can do a walkthrough style video on how to rebuild these if anyone is interested ? Fair few videos on how to do this on youtube but its always nice seeing it done on your own bike
Problem solved!! .... Sort of. Pulsing has now completely gone after i rebuilt the calipers this morning, but after bleeding the brakes, ive noticed that on the first pull of the lever theres more travel than usual ( about an inch from grip ) but if i pull the lever quickly afterwards the lever is fine, untill i leave it alone for 15 seconds, then back to it was before. ive tried bleeding it using the old fashion method as well as with a cheap vacuum pump but nothing seems to be working. I assume theres just a bubble of air trapped somewhere (abs pump maybe?) Any advice or shall i just set the fucking thing on fire?
Haha... you've done exactly the same as me! It's trapped air. Squeeze the lever until it goes hard, then hold and cable tie it in that position overnight. That solved mine although it reverted after a week in the garage. Best is to immediately bleed it after doing the cable tie overnight trick. Mine's worse in that I get no brakes for the first pump. After an overnight cable tie it's rock hard!
Just a note here , do not you copper slip with any aluminium and metal mix , I assume alluminium caliper and steel Pistons or steel brake pins and alloy calipers .... it causes galvanic corrosion , don't use copper grease on backs of brake pads or near wheel bearings ...... it has metal flakes in it . There is special brake caliper greases for pads and calipers Padgid do it . Copper grease is ok where it is metal to metal contact e.g a steel wheel on a steel hub , alloy wheels on steel hubs use non metallic bases greases .
Spot on ,the cementite builds up on the discs and causes DTV ...disc thickness variation , same symptoms as a warped disc
Had a bit of luck from the cable tie but still got around 15mm difference, going to cable tie it for the next couple of days and see if that sorts it, if not im going to put a bleed banjo at the abs pump and try get the air out that way. And if that doesnt work, im just going to get my hammer.
