Disc brake pad wear issue.

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  #1  
Old 11-23-08, 03:32 PM
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Disc brake pad wear issue.

I just replaced the disc pads on the front of my '95 altima and found an uneven wear issue.

The driver side pads were worn down equally to about 20%
The passenger side pads were worn down equally to about 40%. The wear patterns on all were normal.

I did bleed the brakes well after each pad change and well into the driver's side bleeding(which I changed and bled first), I did see 2 or 3 big air sections in the bleeding tubing. Not bubbles, but big gaps of air. I saw no bubbles/air gaps on the passenger side(the less worn pad side.) The calipers were replaced 3-4 years ago and seem to be fine--no leaks etc. . .

The car did and still brakes equally--no pulling.

Could air in the system cause the wear more on the driver's side compared to the passenger side?

Thanx
 
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  #2  
Old 11-23-08, 04:35 PM
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It's the type of thing you can theorize to death.

If air in the lines was part of the equation it would affect braking performance all the way down to a spongy brake pedal. I doubt if air caused anything in the uneven wear.

Other variables could be metal composition of the rotors and the composition of the pads themselves. Or... less road residue from the curb side. In Iowa the centerline side of vehicles and trailers take more of a beating from salt.

I suspect, however the difference between the two sides has to do with the caliper piston retracting or a difference in the sliding of the two calipers which result in more drag on one side than the other. The caliper piston seal actually pull the piston back and one side could have been acting differently than the other. That difference may have been so slight as to not have been noticed over the life of the pads.
 
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Old 11-23-08, 04:46 PM
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Also, on automatics, the transaxle is usually closer to drivers side, which means more weight, which means more friction on that brake.....

I'm no engineer, but that sounds good....
 
  #4  
Old 11-24-08, 06:49 AM
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I am selling the car in a few months--it's a clunker but I do have a conscience and wouldn't want to just sell off a serious braking problem to someone else. The pads were pretty good quality (if price = quality). Maybe since the car is getting on in years the greater distance from the master cylinder to the passenger-side caliper has something to do with it??

Thanx for the help.
 
  #5  
Old 11-25-08, 04:53 AM
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Hi Cbuddy2005
A wear difference is not a major problem as long as the car is breaking correctly.
Each time am changing pads I can see they are not worn equally.
I have done something to decrease this.
You have to undo the piston of each brake, clean inside with ethanol, dry it carefully, and when remounting aply some brakes' grease (Bendix 161100B for instance) on the piston. Your brakes and your rotors will like it!
You can buy only once in your life this kind of grease which is not attacking rubber and you will have plenty left for all the neighborhood.
As you have to disconnect the liquid pipe, it is a good opportunity for a full liquid change. This should be done every 40.000 miles and help all pistons (front and rear) to last a lot longer.
Marc
 
  #6  
Old 11-25-08, 07:55 AM
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Smile uneven wear

Whenever I do a disc brake job, I ALWAYS completely depress the caliper piston so as to be able to clean the sides of the cylinder. A film can develope behind the cyl. and keep iet from moving inward as far as necessary after applying new pads. It seems to work for me; never had a problem.
 
  #7  
Old 11-25-08, 03:35 PM
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don't forget, you have 2 seperate brake lines. usually, they are criss-cross: driver front+pass rear, and visa versa. safety feature. one side fails - you still have 50% brakes good.
so, that involves some trickery with master cylinders and sometimes proportional valves. depends on manufacturer philosophy and how expensive the car is.
i'd assume several things: your master cylinder is getting there. you have one line aired and one not. sticky caliper will wear brake pad ON ITS SIDE, not evenly both on the same rotor. you do not mention anything about rear pads, so there's no knowing if the rear pads follow same pattern - and that sort of points towards the culprit. also, you did mention bleeding front calipers - but did you do same with rear ones? it's pass rear/driver rear/pass front/driver front protocol. unless you driving Japan or Brittain standard car.
 
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