Humbug
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 posted on 5/2/07 at 07:34 AM |
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Brake problems / questions
A couple of things on brakes:
1. From time to time I notice that I get drag when accelerating and smell brake pad dust. A quick blip on the brake frees it up. When I stop and get
out to look, it seems like the front right brake has clamped itself on, as it feels really hot and stinks. I had the calipers reconditioned when I
built the car (Oct 2005 SVA, 2500 miles ago) so I would be pissed off if I needed to get them doen again. Any ideas on what it is and how to fix
it?
2. Although the brakes work OK, the brake pedal has some slack in it, i.e. you have to press it a way before anything happens with little or no
resistance. I have bled the front brakes, but it is still the same. Ideas?
Thanks
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marcjagman
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| posted on 5/2/07 at 08:24 AM |
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Try taking the pads out and moving the pistons in and out, usually works. Ther slack could be either an air lock or your fluid is getting too hot,
bleed them any way to be sure.
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flak monkey
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| posted on 5/2/07 at 08:26 AM |
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First thing to do would be to check the pads are free in the calipers. Suprising what a small burr on the back of the pads can do. Also make sure
theres a good layer of copper slip on the backs and sides of the pads and anti squeal shims, not so much it gets all over the pad though!
David
Sera
http://www.motosera.com
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britishtrident
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| posted on 5/2/07 at 08:34 AM |
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Could be a few things give us a few details; what is your brake set up ? , how are the hydraulic circuits split ? -- what master cylinder(s) are you
using ? and do you have a return spring on the pedal. ?
However fact that the brake clamps hard on points the most likely cause is the piston in the master cylinder not returning fully. Before anybody
suggests (someone always does) it won't be anything to do with the flex hoses.
The excess pedal travel may be an unrelated issue, my first suspect would be that the self adjusters on the rear brakes aren't working, the most
likely cause of this is that the hand brake cable is over tensioned. Try slackening the cables right back and pumping the pedal a few times.
If you have Cortina or similar design front calipers excess travel could also be due to a stuck piston in one half of caliper. Trust me on this as a
long an explanation is required as to why this has this gives excess travel.
If you have proper rubber-textile flex hoses you can eliminate where the lost motion is coming from by clamping off the hoses and trying the pedal
travel.
[Edited on 5/2/07 by britishtrident]
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RazMan
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| posted on 5/2/07 at 08:52 AM |
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My money is on a sticky piston in the caliper - sometimes just working it in & out a few times, then bleeding the caliper can solve the problem.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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mark chandler
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| posted on 5/2/07 at 10:21 AM |
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"2. Although the brakes work OK, the brake pedal has some slack in it, i.e. you have to press it a way before anything happens with little or no
resistance. I have bled the front brakes, but it is still the same. Ideas? "
Sounds like the master cylinder piston is not returning to me and holding the brakes on. Has it got a decent spring inside it or is something fouling
the rod ?
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Surrey Dave
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| posted on 5/2/07 at 11:51 AM |
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i've had my calipers apart 3 times since building the car , one would sieze and drag through too little use and road grime getting in.
The last time i made sure that I had got some grease inside the rubber bellows (should be silicon grease possibly) mine isn't.
You need some mechanical slack in the whole system or it would pump up. also it's hard to get it really solid having drums on the back as
they're free play will effect the pedal.
[Edited on 5/2/07 by Surrey Dave]
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