pedal pushing back

[The Ref]

I have recently had new front pads and disks alone with new rear pads fitted I changed the brake fluid at the same time. The car also passed its mot and has covered 40 miles. This weekend I took her to Scotland and covered over 500 miles. During the weekend when I was pressing the brake pedal, it is pushing back against my foot. Has anyone come across this and if so how do i fix this problem.

Billy

[Foo]

You mean like pulsing against your foot under braking?

[The Ref]

You mean like pulsing against your foot under braking?

yes Foo that is what I mean. I think it may be air in the system.

Billy

[Monty]

You mean like pulsing against your foot under braking?

yes Foo that is what I mean. I think it may be air in the system.

Billy

If it`s Pulsing then that sounds like warped disc to me

[lotusgirlmarie]

[firebobby]

I concur Does it do it all the time, or after a heavy braking session?
It could possibly be that whoever fitted the discs hasn't cleaned the hub face, and therefore the disc is not sitting true! just a possibility and an easy one to remedy.
regards
dave

[The Ref]

You mean like pulsing against your foot under braking?

yes Foo that is what I mean. I think it may be air in the system.

Billy

If it's Pulsing then that sounds like warped disc to me

only 700 miles on a new set of discs/pads the n/s one was warped on the inside edge. had it skimmed so ok for now. I will keep a eye on the mileage to see if it happens again. if so they will be going back. thanks for your help one and all.


Billy

[Monty]

You mean like pulsing against your foot under braking?

yes Foo that is what I mean. I think it may be air in the system.

Billy

If it's Pulsing then that sounds like warped disc to me

only 700 miles on a new set of discs/pads the n/s one was warped on the inside edge. had it skimmed so ok for now. I will keep a eye on the mileage to see if it happens again. if so they will be going back. thanks for your help one and all.


Billy

If ony one disc was warped then you must have a brake caliper problem ie sticking sliding pins. So more than likely this will happen again

[The Ref]

You mean like pulsing against your foot under braking?

yes Foo that is what I mean. I think it may be air in the system.

Billy

If it's Pulsing then that sounds like warped disc to me

only 700 miles on a new set of discs/pads the n/s one was warped on the inside edge. had it skimmed so ok for now. I will keep a eye on the mileage to see if it happens again. if so they will be going back. thanks for your help one and all.


Billy

If ony one disc was warped then you must have a brake caliper problem ie sticking sliding pins. So more than likely this will happen again

can I get new pins and if so were can I gat them from ?

Billy

[dermotbell]

You can take the pins out, clean them and re-grease them and replace. You may find the rubber boots need replacing (19£ a set from SJ).

Also there is a thread here that Bob Brown is running to put in anodised pins. If he gets enough interest I think he said he would do a second run.

[Elanlover]

If it's Pulsing then that sounds like warped disc to me

No such thing as a "warped disc" unless you're racing under extreme conditions and generating heat in excess of what the iron can tolerate. Not likely in our cars under any circumstances. What you would have though (if pulsing is what you're experiencing) is cementide buildup.

Brakes use two differenttypes of "friction" to stop. Ablative and abbrasive. The abbrasive part comes from the pads on the rotor and the ablative part is the rotor shedding surface metal. The pads deposit some of their material onto the rotor surface. Over time you can get an uneven buildup or distribution of this material which can then lead to the "pulsing" feeling from the brakes that people often call "rotor warping".

Now, this can happen even with new pads and rotors if the pads have not been bedded in properly - a surprisingly critical step for new pads and rotors as I learned. There is a recommended process for bedding in rotors and pads and, since many rorots come from the factory with a coating on them to prevent rust, you really need to follow this if you can. It involves (can't remember exactly the steps but this will be pretty close) a set of progressively faster stops starting at about 20 mph, then 30mph, 40mph, 50mph, 60mph and 70mph (if you find the space to do this without getting a ticket ). These stops would be easy stops without really leaning on the pedal. Do this again for a total of 10 times with each stop becoming progressively more aggressive so that the last set of stops involves leaning on the brakes pretty hard. Allow time between each run for the rorots andf pads to cool. When done, drrive the car around for a bit with noremal braing/driving and DO NOT apply the parking brake until the rotors/pads have completely cooled.

Solution To Problem: have the rotors lightly skimmed or machined to remove the uneven cementide buildup IF that's what the problem really is.

(not trying to be a smart ass here since I used to call it "warping" too but this is a little factoid I learned last year that i thought I'd share )

[GeoffSmith]

I used to call it "warping" too but this is a little factoid I learned last year

Me too!

[dermotbell]

That's a good read

[bobbrown]

I agree with Elanlover!

Most people forget to bed in the brakes and do not check the disc when fitted for run out
In our case max run out is 0.1mm (0.004") when fitted and is checked with a clock gauge.

The subject of brake pad break-in can be a very controversial topic. Almost every tech has their own opinion!
It also depends on the type of brakes pads fitted as some require higher temperatures to reach operating range.
Heat should be put into the system gradually - increasingly hard stops with cool off time in between. Part of the idea is to avoid prolonged contact between pad and disc.
Article http://www.stoptech.com/tech_info/wp_wa ... disk.shtml


Bob

[The Ref]

I had the discs skimmed as the left one had warped slightly. After doing less than 200 miles the pulsating returned so this time I ordered two new discs and today I stipped down both callipers which are moving freely. After reasembling the callipers with the new discs I had a close inspection of the old disc and noticed that one has a crack in it (see photo's). Do you have any idea how the disc got cracked as both callipers where moving freely on the sliders.

Billy

http://i247.photobucket.com/albums/gg15 ... C_5348.jpg

http://i247.photobucket.com/albums/gg15 ... C_5323.jpg

http://i247.photobucket.com/albums/gg15 ... C_5333.jpg

[Elanlover]

My personal opinion is that's not normal. The only way you're going to crack a disc is extreme overheating. The calipers would have to be seized on the disc (which you'd obviously notice in more ways than one) or you've been doing some very, very heavy track runs that involve a awful lot of braking. I'm not the expert here but I'd take it back and get a refund. If you've only done 700 miles on the car then this is a defect, plain and simple s I can't imagine anyone being able to crack a disc after 700 miles (only one side too mind you) of normal driving including some track outings (which you haven't done).

[Specky]

I wonder if it's a manufacture flaw with the disk...

What brake pads are you running ?

TTFN

[bobbrown]

That looks more like a material flaw than any thing else.
If the crack was heat related I would expect to see a lot of hair line cracks as per pic

DiscCracked.jpg

[Elanlover]

That looks more like a material flaw than any thing else.
If the crack was heat related I would expect to see a lot of hair line cracks as per pic

DiscCracked.jpg

Good point Bob. There'd have to be more than one crack in one location if it was due to overheating. The jaggedness of your crack looks more and more like a defect. Go get a refund and don't take no for an answer. Be brave, act angry, spout terms to make them think you know what you're talking about and tell them you've had it looked at by a few brake experts (ok only one - Bob - but we all THINK we're experts ).

[The Ref]

the Front disc pads are pec pad428.