Front pads scraping disc
Thread Starter
Advanced
Joined: Oct 2004
Posts: 76
Likes: 0
From: Austin TX
Front pads scraping disc
Hello everyone,
My front left pistons don't pull far enough back when the pedal is released. The pads still scrape against the disc on one part of each revolution.
Is this just a matter of cleaning the pistons in the caliper?
Here are some pics:
Brake engaged:
Brake released: (not enough...)
Is there a general standard distance for the gap between pad & disc when brakes aren't engaged? (i.e. 4 mm)
Thanks,
Mark
My front left pistons don't pull far enough back when the pedal is released. The pads still scrape against the disc on one part of each revolution.
Is this just a matter of cleaning the pistons in the caliper?
Here are some pics:
Brake engaged:
Brake released: (not enough...)
Is there a general standard distance for the gap between pad & disc when brakes aren't engaged? (i.e. 4 mm)
Thanks,
Mark
Thread Starter
Advanced
Joined: Oct 2004
Posts: 76
Likes: 0
From: Austin TX
The dust boots look pretty good, though the pistons seem to be slightly harder than usual to push back with the c-clamp.
This is after changing the pads, the master cylinder (refurbished) & the brake booster (refurbished). Changing so much at once has increased the difficulty of diagnosing
This is after changing the pads, the master cylinder (refurbished) & the brake booster (refurbished). Changing so much at once has increased the difficulty of diagnosing
Race Director
Joined: Jan 2005
Posts: 10,641
Likes: 13
From: Slidell Louisiana
First off are you sure that everything was assembled correctly?
Did you flush the brake fluid? If so how crappy was it IE how much moisture was in it. What's the condition of your rubber brake hoses? I seem to remember a thread a while back where the consensus was that a CF member roached a roter when the rubber hose collapsed and would not allow the caliper to release.
If both calipers were dragging I would hook my mighty vac to the bleed screw on one of the calipers, pull a vacuum and then open the bleeder and see if I could push the piston back in (using a little pry bar) if it was still tight I would pull the caliper. If it moved easily something else is the problem.
Did you flush the brake fluid? If so how crappy was it IE how much moisture was in it. What's the condition of your rubber brake hoses? I seem to remember a thread a while back where the consensus was that a CF member roached a roter when the rubber hose collapsed and would not allow the caliper to release.
If both calipers were dragging I would hook my mighty vac to the bleed screw on one of the calipers, pull a vacuum and then open the bleeder and see if I could push the piston back in (using a little pry bar) if it was still tight I would pull the caliper. If it moved easily something else is the problem.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Originally Posted by lachrimae
My front left pistons don't pull far enough back when the pedal is released. The pads still scrape against the disc on one part of each revolution.
Can you measure the gap (with a feeler gauge) that you're seeing in the left brake? Can you find any gap in the right brake? Do you feel any pulsation in the brake pedal when you press very lightly on the pedal when you're driving the car?
This close contact between the pad and the rotor is one of the reasons disc brakes work so well in wet weather. This close contact keeps any water from getting into the brake pad contact area. Drum brake shoes retract from contact with the brake drums, so they can easily get wet, and don't work nearly as well in wet weather.
Save The Wave!
Melting Slicks
Joined: Jun 2004
Posts: 3,253
Likes: 2
From: Castro Valley CA
Were new rotors installed? What brand of pads did you use?
Have you driven the car and bedded in the brakes or is it still on the jackstands? Were the pads a tight fit during install? I once encountered out of tolerance pads; I bedded them in very aggresively, problem solved.
Have you driven the car and bedded in the brakes or is it still on the jackstands? Were the pads a tight fit during install? I once encountered out of tolerance pads; I bedded them in very aggresively, problem solved.
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Melting Slicks
Joined: Mar 2003
Posts: 2,472
Likes: 0
From: Toronto ONTARIO
I would say that is normal. ive gone through numerous cars and replaced pads/rotors on may of them and ive always heard the pads rubbing slightly when turning the wheel. the wheel should spin freely though. if you turn it and see resistance than you may have an issue. but 4mm imo is waay too far for a pad to be out. from what i believe and know there shouldnt be any 'air' gap between the rotor and pad.. as stated above there is nothing inside the caliper to pull the pads back. when releasing the brake pedal (say while moving) the pad will still be touching and as it rubs gasses will be created off the pad keeping it away from the rotor enough to have no resistance. etc.
Pro
Joined: Oct 2005
Posts: 721
Likes: 1
From: Charlotte NC, behind someone going 10 under the speed limit
Originally Posted by DieL
I would say that is normal. ive gone through numerous cars and replaced pads/rotors on may of them and ive always heard the pads rubbing slightly when turning the wheel. the wheel should spin freely though. if you turn it and see resistance than you may have an issue. but 4mm imo is waay too far for a pad to be out. from what i believe and know there shouldnt be any 'air' gap between the rotor and pad.. as stated above there is nothing inside the caliper to pull the pads back. when releasing the brake pedal (say while moving) the pad will still be touching and as it rubs gasses will be created off the pad keeping it away from the rotor enough to have no resistance. etc.
