brakes not quite right
Discussion
this seems a bit of a saga so i'll give some background to paint a picture...
Car is a 2015 civic typeR. Daily driver with trackdays thrown in a few times a year. standard discs all round, pads have been upgraded; fronts ProjectMu HC800's, rears have been projectMu NS400, and now Dixcel Z's.
Since the trackday seems to be the commonality of this, i'll base the timescales from then.
T-18months - fitted HC800 front pads
T-2months - replaced rear OEM pads at around 18k miles. pads see woefully underspec'd for the power of the car, but hey ho - 18k, not too bad. brake fluid replaced with ATE typ200.
brakes feel perfect at this point. good bite, good pedal. no difference than the factory brakes.
Trackday - all good for a few sessions, until pedal seems to travel a bit further. Noticeable difference, maybe 1/3rd extra travel, but brake performance still good. came in to pits, cooled off just to ensure it's not fluid or anything unexpected. all seemed fine. nearer the end of the day, i lost the rear brakes so back to pits to cool off again and a final run to end the day with.
drive home all was well, except for the long brake travel. solid pedal, brakes performed fine.
T+few weeks - notice theres little pad material left of the rear brakes - lasted about 3 months. i think pad thickness was fine pre-trackday so put it down to not man enough for track use. i upgrade to the Dixcel Z pads which are rated for track use. also notice initial bite when cold seems to be a small but noticeable problem assume it's down to rear pads.
T+1.5months (the last week) - dixcels rear pads fitted, both rear brakes seem to be binding. took them apart to double check and diagnose everything; piston returns fine, pads loose in the carrier, caliper slide pins free & greased, h/brake cable removed. everything seems good & well on the health of the system. car been for a good blast up the road and got the rear pads so hot, they were smoking. something seemed off as being on the road simply isnt enough to generate that much heat. rear brakes do seem less noisy but still got that scraping sound from dragging brakes.
early morning initial bite still poor and not like it was pre-trackday.
that's the background, so 2 main issues at hand: slightly longer travel on pedal (brake performance fine), rear brakes binding.
I'll be pulling the brakes apart AGAIN this weekend and likely be doing a brake bleed to eliminate that, but without a spongy pedal i'm doubtful this will have any benefit.
Any help appreciated, i'm stumped on this one and clutching at straws now.
Only possible thing i could think of, is the NS400 pads did not come with an anti-squeal pad, these Dixcels do. I think the OEM pads did not come with them either. Is it possible that these anti-squeal pads are slightly compressible and causing the piston to not return enough causing the dragging? afterall, when you remove old pads with these fitted, ime they are slightly compressed where the caliper contacts them.
Car is a 2015 civic typeR. Daily driver with trackdays thrown in a few times a year. standard discs all round, pads have been upgraded; fronts ProjectMu HC800's, rears have been projectMu NS400, and now Dixcel Z's.
Since the trackday seems to be the commonality of this, i'll base the timescales from then.
T-18months - fitted HC800 front pads
T-2months - replaced rear OEM pads at around 18k miles. pads see woefully underspec'd for the power of the car, but hey ho - 18k, not too bad. brake fluid replaced with ATE typ200.
brakes feel perfect at this point. good bite, good pedal. no difference than the factory brakes.
Trackday - all good for a few sessions, until pedal seems to travel a bit further. Noticeable difference, maybe 1/3rd extra travel, but brake performance still good. came in to pits, cooled off just to ensure it's not fluid or anything unexpected. all seemed fine. nearer the end of the day, i lost the rear brakes so back to pits to cool off again and a final run to end the day with.
drive home all was well, except for the long brake travel. solid pedal, brakes performed fine.
T+few weeks - notice theres little pad material left of the rear brakes - lasted about 3 months. i think pad thickness was fine pre-trackday so put it down to not man enough for track use. i upgrade to the Dixcel Z pads which are rated for track use. also notice initial bite when cold seems to be a small but noticeable problem assume it's down to rear pads.
T+1.5months (the last week) - dixcels rear pads fitted, both rear brakes seem to be binding. took them apart to double check and diagnose everything; piston returns fine, pads loose in the carrier, caliper slide pins free & greased, h/brake cable removed. everything seems good & well on the health of the system. car been for a good blast up the road and got the rear pads so hot, they were smoking. something seemed off as being on the road simply isnt enough to generate that much heat. rear brakes do seem less noisy but still got that scraping sound from dragging brakes.
early morning initial bite still poor and not like it was pre-trackday.
that's the background, so 2 main issues at hand: slightly longer travel on pedal (brake performance fine), rear brakes binding.
I'll be pulling the brakes apart AGAIN this weekend and likely be doing a brake bleed to eliminate that, but without a spongy pedal i'm doubtful this will have any benefit.
Any help appreciated, i'm stumped on this one and clutching at straws now.
Only possible thing i could think of, is the NS400 pads did not come with an anti-squeal pad, these Dixcels do. I think the OEM pads did not come with them either. Is it possible that these anti-squeal pads are slightly compressible and causing the piston to not return enough causing the dragging? afterall, when you remove old pads with these fitted, ime they are slightly compressed where the caliper contacts them.
I've seen sliders that seemingly work OK statically but are worn enough to twist and jam under real braking loads. If the brakes are dragging, you should be able to come to a stop, chock the car rather than use the handbrake, jack it up far enough to get one rear wheel off the ground and feel a significant drag when you spin the wheel by hand.
answers to the questions:
standard suspension.
calipers wound back all the way - a pump of the pedal to take up the slack with the pad.
wheels drag slightly. remove the pads, spin wheel and it'll go for 10+ revolutions. fit pads and pump pedal to seat the pads gives 3 full spins. i know pads touch very slightly, but seems a bit too much reduction to know. unfortunately my last car was rwd so my perception of a fwd car rear brake drag isn't accurate and thus cant compare to what i've been used to. h/brake cable was removed for this test, and the h/brake arm sat against it's stop.
Calipers are ATE's with the 7mm hex sliders on. can be screwed in with fingers and brake grease used - seem fine as a static test; cant see how they'd bind up under a more dynamic load.
standard suspension.
calipers wound back all the way - a pump of the pedal to take up the slack with the pad.
wheels drag slightly. remove the pads, spin wheel and it'll go for 10+ revolutions. fit pads and pump pedal to seat the pads gives 3 full spins. i know pads touch very slightly, but seems a bit too much reduction to know. unfortunately my last car was rwd so my perception of a fwd car rear brake drag isn't accurate and thus cant compare to what i've been used to. h/brake cable was removed for this test, and the h/brake arm sat against it's stop.
Calipers are ATE's with the 7mm hex sliders on. can be screwed in with fingers and brake grease used - seem fine as a static test; cant see how they'd bind up under a more dynamic load.
veehexx said:
h/brake cable was removed for this test ... cant see how they'd bind up under a more dynamic load.
Depending how much flex and slack there was in the handbrake cable, I suppose it's possible that the cable itself was flapping around during bumps and just tweaking the rear brakes on slightly. But the calipers themselves can behave quite differently under real-world braking loads than when you push on them by hand and it's entirely possible they're jamming on. I explained how to test for that.fluid was changed along side the NS pads 1.5months before the trackday. Car had a dealer service the week after the trackday which /should/ of included a fluid change. I'm skeptical if it was as a week later there was no residual fluid in the bleed nipples or spanner marks on the nipples. Hard to prove without a fluid boil test but they're not cheap to buy.
The usual check for air in the system doesn't show any issues; pedal is rock solid and doesn't sink or creep.
anyway, i've decided to rip the brakes apart once again at the weekend and do a full check...check the (oem) brake flex hoses for any bulges, if ok change fluid just to be 100% sure it's not that.
also bought some standard mintex rear pads (£20 - good for an emergency set) to see if that shows anything with the dragging issue. At the moment, without part elimination, i'm unsure if it's these dixcel Z's causing the dragging or if it's both rear calipers/system fault. Can't see a 2.5year old car having anything too serious up with it but up to now the mechanical side appears to be both by-feel and visually ok on the brake side. symptoms say otherwise.
The usual check for air in the system doesn't show any issues; pedal is rock solid and doesn't sink or creep.
anyway, i've decided to rip the brakes apart once again at the weekend and do a full check...check the (oem) brake flex hoses for any bulges, if ok change fluid just to be 100% sure it's not that.
also bought some standard mintex rear pads (£20 - good for an emergency set) to see if that shows anything with the dragging issue. At the moment, without part elimination, i'm unsure if it's these dixcel Z's causing the dragging or if it's both rear calipers/system fault. Can't see a 2.5year old car having anything too serious up with it but up to now the mechanical side appears to be both by-feel and visually ok on the brake side. symptoms say otherwise.
cuprabob said:
As said, pay the £80 and put it on retention. You then have it on retention for 10 years and don't need to do anything in that time. If you put it up for sale, I'm sure you'll recover your £80 and maybe even a little profit.
Is that really your answer?I assume you have cross-posted.
looks like i had a few problems.
first, front pads were glazed. that explains the initial bite issue. they also feel better mid-pressure braking. I think i need to consider grooved discs in the future when the OEM drilled discs need changing to keep the pads in top form.
brake fluid change - no obvious improvements. at least i know i've got fluid good enough for trackdays again.
Lastly, the rear pads. removed the rear fabric type anti-squeal pads that came on the dixcels and seems to be better. brakes dont seem as warm and after a 20-30min run, fronts are notably warmer than the rears. keeping this anti-squeal pad in place made the front/rears similar temps (hand feel, on the wheels). as per my initial thought, these fabric anti-squeal pads appear to be slightly compressible and causing slightly too much drag. There was a rather obvious compression mark where the caliper piston pushes on the pad which you dont get with bare pads or the metal type anti-squeal pads.
thanks for the suggestions all!
first, front pads were glazed. that explains the initial bite issue. they also feel better mid-pressure braking. I think i need to consider grooved discs in the future when the OEM drilled discs need changing to keep the pads in top form.
brake fluid change - no obvious improvements. at least i know i've got fluid good enough for trackdays again.
Lastly, the rear pads. removed the rear fabric type anti-squeal pads that came on the dixcels and seems to be better. brakes dont seem as warm and after a 20-30min run, fronts are notably warmer than the rears. keeping this anti-squeal pad in place made the front/rears similar temps (hand feel, on the wheels). as per my initial thought, these fabric anti-squeal pads appear to be slightly compressible and causing slightly too much drag. There was a rather obvious compression mark where the caliper piston pushes on the pad which you dont get with bare pads or the metal type anti-squeal pads.
thanks for the suggestions all!
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