My car pulls insanely to one side when the brake is applied forcefully at high speeds. It pulls to the LEFT as viewed from the driver's seat. All side refferences are made from inside the car, not outside looking at it

Let me first explain the type of braking system that I have: It is a single piston, two-peice caliper design (ie the caliper part holding the pads can be unbolted from the piston assembly, which then can be slided off the torque plate) It has clips to hold the pads in, which are broken/missing (I know this isn't the problem, they're there for the pad to retract evenly so the brake pads wear evenly instead of on an angle) The brake system utilizes a proportionning valve and is a RWD car so there are no CV joints to mess things up: just an inner bearing and outer bearing on a spindle.

Here is what I did:

Pads were very low so I decided to replace them. At this time the car pulled very slightly to the left (driver) when brakes applied (figued it was due to 2 mm of pad material left... rotors are OK) Got new pads and an inner and outer bearing assembly for the RIGHT (passenger) side of the front, as I suspected I did not repack them properly the first time and now they're worn. SO I dissassembled the caliper assemblies, noted that I need to get new dust seals (especially on the left (driver) side, checked for bearing play and gave the hubs a good spin. The driver side spun freely and noise-free. I proceeded to install the pads, then tightened the caliper, forcing the piston back inside it's housing. OK it all fit. I put the wheel back on and tried to spin the wheel. Very hard.
On to the passenger side: After removing the caliper ass'y and putting it aside, I spun the hub. It spun well enough, but there were clicking sounds from it. I decided to take it all apart. I noticed metal shavings in the other bearing... clean and replace both bearings and races (had to punch them out w/a hammer...), repack them and grease up the hub. Put hub back on the car, torqued it and eliminated play, and adjusted for optimal spin. No clicking noises, spin well. I put back on the caliper and pad assemblies, same way, forcing the piston back by torquing the caliper like on the other side. I put back on the wheel, gave it a spin, and spun more freely than other side (due to more initial brake pad pressure on the other side) I road-tested the car over and over again and it pulls HEAVY to the driver's side. When brakes not applied, car travels in a straight line, eliminating the possibility of an overtightended hub (remember the PASSENGER bearings were replaced and the driver's side spun freely and were adjusted correctly) and brake drag. WTF? My Other PONY does this too, to the point where the pads wear down to the rotor in just 6000 km's on one side, other side barely touched. That Pony pulls to the passenger side, not as heavy. That Pony has two new caliper assemblies, torque plates, and pistons. They were bought new. I bled the brakes properly and made sure hubs were installed and torqued correctly for both cars. WTF am i doing wrong?????

Don't tell me to bleed the brakes!! The fluid was not touched and is at correct levels!

What the hell is wrong with my brakes!! in both cases, it is evident that only one brake is doing the stopping. WHY!

I'm going to buy a rebuild kit for my car (piston, bleed screw and seals) as well as new slide pins and a set of clips. I doubt that this will solve my problem... can you?

Jed

 

Jed, does your car have a dual-split braking system, where the right front and left rear brakes are on one circuit, and the left front and right rear are on the other?
Are both back brakes working to slow the car?
If the pads on one side are wearing that much quicker, I would want to guess that one of the front calipers is faulty, OR there's a hydraulic problem somwhere in the system.
Is the brake pedal travel normal? If there's too much pedal travel, I'd say the problem is hydraulic.

 

Pedal travel is fine, it's not mushy or spongy. in RWD cars, the brakes are split 50/50 front/rear. In this particular car, ONE brake line goes to both rear brakes (travels through rear left cylinder, then over to the rear right cylinder. There is only one bleeder screw) The rear brakes are on a separate circut entirely, but the front right I beileve travels through a PROPORTIONING valve while the left one does not. Either way, the hydraulic system itself was not touched. It is a mechanical problem, but where?

 

Could there be a problem with that proportioning valve that's not allowing enough hydraulic pressure to get to the right front, and then sending too much pressure to the left front?
Also, from the cars I've worked on, proportioning valves are usually situated in the brake system between the front and rear brakes, taking into account rear suspension height to prevent rear wheel lockup under heavy braking.
The idea usually is that if there is less weight on the back wheels (such as when you brake hard), less hyd. pressure goes to the rears, but if you have a lot of weight in the back (like three passengers or whatever) the valve sends more pressure to the back wheels.
Having a proportioning valve on one wheel only seems a little weird to me.

 

Before changing the pads, the rears would lock up before the fronts. Actually, the front's never loclked up until now

 

Come on people I NEED ANSWERS!!

 

Sounds like you need a caliper overhaul bro.

Check these:

-WHen you replaced the pads and moved the caliper pistons back, did the left front retract as easily as the right? If you had to struggle to force it back in you'll propably need to get a couple of new caliper pistons and refinish the interior of the calipers with a 1400grit wet-sand. Finish the job with Autosol polish or good old compound polish(you'll need to rinse well if you use the compound and this takes a day)

-Check the hoses for kinks
-Check the hoses for blockage
-Check the master cylinder assembly to see if the front channels are still free-flowing or if there is a kink somewhere in the seals.
-If floating disc: Check disc freeplay
-If floating caliper: Check caliper retraction along slide-shaft(yeah I forgot the name sad.gif )and see if the left is binding because of this.
-If you have acess to a workshop put excess fluid in and attempt a bleed; if the right shows signs of not having fluid come through the line then you found your problem, ditto for the left.Bleeding also helps in mechanical fault diagnosis.

Try all these first man, and good luck!

 

I went to get some laquer today for my rims and was told by a guy that owned 2 pony's before that the pad tolerances to the caliper housing and tthe slide pins were awful. (when they rust) He told me that I might have to grind away some of the pad metal (I already did this from the driver's side) becuse if I don't, the piston will push the pad on crooked and it will jam, and won't engage the rotor. Unacceptable. I will overhaul the damn calipers too, as the dust boot is nonexistent on the driver's caliper.

I might aswell bleed out the old fluid.... the back's ok, the cylinders leak (very slightly) enough that they "self bleed" The linings are fine and the autoadjusters work (surprisingly)

These MMC brakes are a *****. Floating caliper my ass!

 

Aight man now that you propably got a bead on the problem(slide-shaft)just a note; when you take the brush burnish to the shafts and finish them grease and do a test fit. If there is excess freeplay(the calipers are a loose fit on the shafts and can wiggle around and create more than 5 degrees angle between the slide-shaft and the caliper recess) you may want to pull a set of shafts; this can ause the shafts to deform and bind the caliper under retraction or actuation.

Good luck with it bro.

 

I lifted the car front up.

The front left retracts immediately and all the way. The driver's side retracts fast, but wheel is hard to turn. BOTH sides make a clickling sound, the front left makes a high pitch squeeel when cornering at low speeds... i'm SO pissed off at this now!