uneven braking

[Cypher007]

ok did the brake upgrade spent the money now have car that just failed MOT . DONT UNDER ANY CIRCUMSTANCES UPGRADE YOUR BRAKES UNLESS THERE BUG**RED cause it aint worth the hassle and expense. now the mot guy says my passenger side caliper is pulling up slower than the drivers side, so i said it cant its a new caliper (from gsf) well he says maybe youll have to replace the drivers side also. ? im thinking, if the gsf one is the slow one then surely thats the faulty caliper. looking at the old discs it looks like the original caliper did the same thing as one disc was more worn than the other, hence why i replaced the frig**n caliper in the first place. could there be problems at the abs end of the braking system? also could it be the pads still bedding in? to be honest looking at the brake tester i couldnt see much of a problem.

[CTCNetwork]

Hi,

Sorry to hear your troubles.
I would have though it advisable, when dealing with brakes/brake pads/wheels/tyres etc, to do the job in pairs?
It is not clear whether you have done this..

It maybe if there is an inbalance between sides that there is an issue with the brake fluid for one side, did you bleed both near and off sides?

Hope you get it sorted..

Des. . .

[Cypher007]

replaced both pads, discs, and the one doggy looking caliper, the same side hes now saying is slow.

You could try bleeding it through again in case there is a little air trapped in that side, maybe try pressure bleeding?

Pete

[Cypher007]

how do i pressure bleed the cars braking system? is it using an extra tool? could i have a faulty abs unit? as the front brake circuits are separate (because of the TRACS system).

Yeah a pressure bleeder like Gunzon's eezibleed.

[Cypher007]

yes im using the gunsons one man kit without the bottle, using an old jam jar, its a peice of plastic pipe with a rubber connection one end of the plastic pipe and a one way valve at the other end of the plastic pipe. yes?

Originally Posted by Cypher007

yes im using the gunsons one man kit without the bottle, using an old jam jar, its a peice of plastic pipe with a rubber connection one end of the plastic pipe and a one way valve at the other end of the plastic pipe. yes?

It's good....
.... but it's not right

What that does it let you pump the pedal without having to worry about sucking air back in. And it's a lot better than "gravity bleeding".

But a pressure bleeder will pressurise the brake fluid reservoir, usually using pressure from the spare tyre. It relies on you not having an air leak around the cap. The pressure forces brake fluid in from a bottle into the brake fluid reservoir under pressure. You then open the bleed screw and a stream of brake fluid comes out, it is pushed out by the incoming fluid under pressure. The effect is to force any trapped air bubbles along and so the system is good for bleeding brakes which tend to have air trapped in them after normal bleeding.

Do you feel the pedal sinks down a bit too much and won't go hard? If so, then it is likely there is air trapped. Is the bleed screw on the top of the caliper? Air rises, so if the screw isn't remove the caliper and angle it so the screw is on the top and then try your bleed.

Another thing you could try if changing both calipers won't do it is to change the brake hoses. I dunno why but I had problems with a hose causing a bit of an intermittent blockage after changing calipers, maybe all the crud getting disturbed in the caliper changes causes it or something.

For reference gunson's eezibleed

[Cypher007]

just looked on there site and was about to post a whoops coment but you beat me to it. think ill try and find the receipt for this kit and change it. also was gonna try and get some brake grease, my dads suggestion (says its hard to find), and lubricate the piston, he says sometimes if a caliper has been on the shelf a while it can get sticky. just one other question is it possible to take the piston out of the caliper? that way i could check it more closely. one more question honest, i didnt bleed the clutch system should i have done this? oh and the tester said when i said maybe theres some air still in the system "dont think so mate the pedal seems quite hard".

p.s. do i need to put some copper grease on the brake pad runners so they slide on the caliper and caliper brackets better. and do you think adding some more silicone grease to the caliper guides might help?

Ok - that's quite a few questions altogether!

First of all, no don't lubricate the piston with anything except new brake fluid.

I'd agree it could get dry while sitting around. Some suppliers pre-fill their calipers with fluid to prevent this and to prevent airlock problems. I had some problems with volvo supplied calipers recently, one is going back as it sticks. You could try filling it with brake fluid (like when it is all connected up on the car) and then using a windback tool etc. to push it back in then use the pedal to push it back out a few times, and then hopefully you are dragging some fluid along the seal. The way a caliper works is the seal is supposed to stretch a little when you push the brake as the piston comes out and then this springiness pulls it back in. I guess if the seal is dry it maybe can't do this properly.

Re. the caliper guide pins, check them. (That's what the brake grease is meant for by the way). It's a floating caliper so as the piston pushes out it pulls the outer brake pad towards the disc. It won't if the guide pins are stuck so do check this by removing one or both pads and try pushing the caliper in and out, it should move fairly easily but tight in and out on the guide pins. If issues, remove their covers remove them and re-grease with the brake grease. You say silicone grease, yes that is the stuff. Silicone lubricant as used in plumbing could be used as well although it is thinner. From what you say I think you must have got a bit of brake grease with the caliper, it is meant for the guide pins.

I would not remove the piston. I do not see what it would achieve, unless you find the piston is scored or not machined correctly. But if you suspect the caliper is faulty, you should take it back. If you remove the piston and someone can tell, then you may have problems claiming under the warranty. You may also damage a seal removing it and end up paying for a new repair kit. It can be a bit of a pain to get them back in flush especially if it is a screw in type. Honestly I do not think there is any point to removing it.

What else... yes you can put a little smear of the copper grease on the pad backings where they will contact the caliper bracket, and also on the back where they will contact the caliper. This is largely for anti-squeal purposes but helps prevent sticking. But do clean any crud like previous brake dust off where the pads sit too, otherwise the copper grease will just sludge up to that. My opinion is that copper grease is better than the "high performance brake grease" stuff because the latter just seems to go all sticky and horrible after a short time. I had some mintex stuff which looked just like normal grease, I found it a bit thick and horrible but just my opinion. It was transparent though which could be an advantage to some people.

You may want to bleed through the clutch while you are at it if you do happen to rig up a a pressure bleeder, but as the feed from the clutch is (I expect) taken direct from a separate pipe from the reservoir then it has nothing at all to do with the brake circuit.

I have read some of your posts a bit more detail and it seems you have only replaced the one caliper. The reasoning behind replacing both sides is that it is possible that (as has been discussed elsewhere around the forum), your old caliper will now be stiffer and so that wheel will brake (relatively) less. But strangely you seem to have the opposite problem! So I suspect you have some sort of fault. But do please consider changing the brake hose on the iffy side. You can get one for maybe just £10 and it is not difficult to do (you've already done half of it in changing the caliper ). I would even post some "general" instructions right now but I'm too tired my hand hurts from all this writing, and I feel I've only got one paragraph left in me for now, and here it comes....

Do you find the car pulls to the offside (driver's side) when you apply the brakes, because the nearside front caliper is not braking properly? If you find it is only slight or not at all, then I am amazed he failed it on the MOT! My experience was the MOT brake test was never too difficult to pass, well maybe times have changed.

Cheers,
Pete