Uneven brake wear

B

beerdog

Registered
In preparation for doing my brakes I inspected all 4 wheels last week. Noticed that the pads on the driver's front and passenger's rear were worn down much more than the other 2. Any thoughts on if this an indication of some other problem? I did not do the brakes the last time since I did not yet own the car. I did cut the passengers side rotor after I bought it because it was warped. The last owner did not know that was all that was needed to stop the chirping noise.

Driver’s side front wheel was very difficult to remove. The lug nuts were very corroded to the studs and wheels. Also had a slight vibe above 50MPH which seems to have gone away.

Good thing was there were no leaks, no caliper slide pins were rusted, and the pads on each wheel were evenly worn.
 
Could be a number of things....and nothing really to be too worried about.

If it were my car, I would address it this way.

Do a complete fluid flush by opening the bleeder on each caliper and squeezing the caliper piston down, shutting the bleeder with pressure still on the piston. Do each one individually (back ones are a PITA unless you got the tool...which still is tough) and while you pump the brakes up, make sure you keep topping off the brake master cylinder.

Then I would be sure the rotors don't have heat spots on them and do a brake job.

When putting everything back together, put the Silver Anti-seize on EVERYTHING! Caliper slide pins, back of the pads, where the pads ride on the caliper bracket, the caliper bolts, the center of the hub where the rotor/wheel centers itself, and the wheel studs. It doesn't take much, just a dab here and there and then brush it flat. This will prevent your wheel, lug nuts, and even the rotor from "freezing" itself on.
 
Not to discount what J said, but a typical brake system is redundant. Meaning two different fluid circuits connect diagonal wheels. This is why there are two ports connected to the master cylinder. If a brake line should leak, you would still have two wheels to slow down with.

Not sure, but your problem may have something to do with that.
 
"Good thing was there were no leaks, no caliper slide pins were rusted, and the pads on each wheel were evenly worn.[/QUOTE]"

I thought you had uneven wear. You should always do pads & rotors in pairs (fronts or rears). The differences you are seeing could also be from the pad material. Maybe prior owner had two different ones in there to try and solve the previous problem.

All above are good thoughts in my book. I am a fan of Bendix rotors and pads (ceramix) and that is what I would put on (Advance Auto).
 
logres said:
Not to discount what J said, but a typical brake system is redundant. Meaning two different fluid circuits connect diagonal wheels. This is why there are two ports connected to the master cylinder. If a brake line should leak, you would still have two wheels to slow down with.

Not sure, but your problem may have something to do with that.
Click to expand...

I've seen this before, and it can be a prelude to a master cylinder problem.

I would simply do a normal brake job and monitor it after for uneven wear. If it does wear one front and the opposite rear more than the other two, it's likely the master cylinder going bad.
 
Thanks all. I was thinking it is potentially an impending master cyclinder issue. I was already planning on putting on rotors since they were getting pretty thin. If I cut the fronts they will be at the min requirement. Picked up good pads and rotors at a great price on Rock Auto. Also planning on doing a flush.
 
logres said:
Not to discount what J said, but a typical brake system is redundant. Meaning two different fluid circuits connect diagonal wheels. This is why there are two ports connected to the master cylinder
Click to expand...

:D

The two ports on a Master Cylinder are for front/back not left front/right rear and vice versa. Atleast thats the way I've understood it for all these years, haha, expecially on dual resevoir masters.

Roadboss said:
You should always do pads & rotors in pairs (fronts or rears).
Click to expand...

I never understood why people think this way, but if each caliper is kinda a "stand alone" part on the brake system, why would it matter if one rotor has been turned and one hasn't, or if one is thicker than the other. I would agree that you should always change the pads in pairs just because its easier, but again, it doesn't matter or do anything to the braking performance.

This "theory" has always been on my list of shady mechanics trying to get more money. "Never install just one new rotor, your car will pull to the right if you do." Lol! :)

Roadboss said:
The differences you are seeing could also be from the pad material. Maybe prior owner had two different ones in there to try and solve the previous problem.
Click to expand...

That is a good point! You never know what kinda work has been performed on it! A lot of people don't look at things that way, good thinking! Its kinda like assuming the new part you just installed to fix a no start issue is now ok, come to find out 4 hours later that the new part is BAD. :D
 
J said:
:D

The two ports on a Master Cylinder are for front/back not left front/right rear and vice versa. Atleast thats the way I've understood it for all these years, haha, expecially on dual resevoir masters.
Click to expand...

Maybe on a Honda. :p

From the manual...

Brake System--Dual

This vehicle is equipped with a pedal actuated dual brake system. The system consists of the following:

~Power brake booster

~Master cylinder

~Brake pressure control valves

~Brake tubes and hoses

The dual ABS hydraulic system is diagonally split with the LH front and RH rear comprising one circuit and the RH front and LH rear, the other circuit.
Click to expand...

:fart
 
Thats how it comes out of the ABS pump, but NOT the master cylinder....right?
 
logres said:
Not to discount what J said, but a typical brake system is redundant. Meaning two different fluid circuits connect diagonal wheels. This is why there are two ports connected to the master cylinder. If a brake line should leak, you would still have two wheels to slow down with.

Not sure, but your problem may have something to do with that.
Click to expand...

I know the systems are designed to have two separate loops to preserve some braking in an event like a brake line burst but I know one instance where that just didn't work. My fathers 94 F-150 had one of the front line burst where it goes through the frame to the wheel well opening and the pedal just went to the floor on it, no brakes at all. He nearly got in a really bad accident because of it.
 
This "theory" has always been on my list of shady mechanics trying to get more money. "Never install just one new rotor, your car will pull to the right if you do." Lol! :)


It gets to be more problematic, in that if a customer comes back with an issue of brake pull it cannot be ignored that a (used rotor/new brake pad) vs (new rotor/new brake pad) may be the problem, and everyone gets their hair up a little. Customer gets excited thinking he got a bad job, and wrench is left trying to diagnose a problem and put more time on the job. While on the counter I saw many a back yard mechanics come in a buy a set of pads and one rotor to fix a side (most often because that was all he could afford) and then come back in a couple weeks moaning about pull or noises, and ends up finishing the job with the second rotor. It has been my experience that if one side is bad, the other is probably not far behind. Get-R-Done !!
 
95blklsc said:
I know the systems are designed to have two separate loops to preserve some braking in an event like a brake line burst but I know one instance where that just didn't work. My fathers 94 F-150 had one of the front line burst where it goes through the frame to the wheel well opening and the pedal just went to the floor on it, no brakes at all. He nearly got in a really bad accident because of it.
Click to expand...

The reason it didn't work is because the port on the master cylinder for the front brakes is the one that gets "activated" (rear port) first so you lost all your pressure on the first stroke. Pumping the brake would have got some pressure to the rear brakes through the front port. Obviously if its a last ditch attempt it would be hard to have enough time to pump the brakes.

Roadboss said:
While on the counter I saw many a back yard mechanics come in a buy a set of pads and one rotor to fix a side (most often because that was all he could afford) and then come back in a couple weeks moaning about pull or noises, and ends up finishing the job with the second rotor.
Click to expand...

I don't understand how a rotor being a different thickness (not defective) causes pull....Obviously if the rotor is heat warped, has hot spots, or is AT or BELOW the runout measurement you shouldn't leave it on there.

I'm just pointing out that if a rotor is used for an undertermined amount of time (3k miles) and you have one of your rotors go bad, there would be NO point to replace them both again for example.

The caliper will squeeze the rotor with an equal amount of pressure NO MATTER what thickness it is, so having a brand new rotor on one side and another that is used (thinner) will NOT cause the car to pull.

Ofcourse you take in effect the mechanic that is too poor to afford two new rotors, and you have to take a look at what kind of work this mechanic previously did to the other side that he did not fix and how he drives etc.

I have never sold someone two rotors when they didn't need it. I would just turn one rotor and replace the ones that were below spec. Never had a problem either......

:D


Roadboss said:
It has been my experience that if one side is bad, the other is probably not far behind. Get-R-Done !!
Click to expand...

Thats because of the "theory". Haha...people always change two rotors, even if they don't need two. Ofcourse they will both continue to wear down the same. :)
 
J said:
Thats how it comes out of the ABS pump, but NOT the master cylinder....right?
Click to expand...

Geesh J ...

Again, from the manual...

Master Cylinder

The master cylinder is a tandem master cylinder. The primary (rear) circuit feeds the RH front and LH rear brakes. The secondary circuit (front) feeds the LH front and RH rear brakes. It is serviced as a complete assembly.
Click to expand...

You have two hydraulic circuits from the master cylinder to the HCU(Hydraulic Control Unit). Then you have four lines from the HCU, one to the right front caliper and one to the left front caliper. The right and left rear hydraulic circuits from the HCU go to the proportioning valve, then onto the right and left rear calipers.

I've not seen a Mark VIII with this diagonal uneven wear issue - but in fleet service, I've seen a couple Ford trucks display this symptom and each time it eventually needed a master cylinder.
 
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