Front brake wear very asymmetric wheel-to-wheel

Factual Questions
1

I’ve got a 2006 Honda Accord LX with about 255,000 miles on it. I do most maintenance myself, including brake work.

The front brake pads were last replaced 12,000 miles/11 months ago. At that time, pad wear was uniform and equal on all four pads. One caliper pin (upper left) wasn’t moving very freely, but I cleaned and re-lubed all four and it seemed fine on installation. The rotors appeared to be in fine shape, so in accordance with the shop manual’s recommendation I did not have them resurfaced.

I recently heard wear-indicator noises (very early based on past history), so today I popped the wheels off to have a look…

Both pads on the right wheel are worn nearly to the metal; the wear is uniform across the pads and both are worn approximately the same amount. Both pads on the left wheel look practically brand-new.

The right-side rotor is noticeably worn - it’s well below discard thickness when I measure it, and there’s an obvious ridge along the outer edges of both faces, where the pad material doesn’t quite reach. Based on the size of that ridge, it appears that both faces of the rotor have worn about equally. The left-side rotor appears normal and measures out at the “new” thickness.

All four caliper pins seem to move freely. I’m able to compress both pistons into their calipers with normal effort - they certainly don’t feel bound up to me.

Here’s what I find surprising: I have noticed absolutely nothing out of the ordinary while driving the car (besides the wear indicator noises). No pull to one side under braking (or while not braking); no altered pedal feel or travel; no pulsation. My wife, who also drives the car from time to time, has noticed nothing either.

Clearly, something is wrong.

Pads and rotors have to be replaced, of course, but if I don’t address the underlying problem I’ll be right back where I am now in a year or less. Possible problems that come to mind are:[ul]
[li]Stuck caliper piston;[/li][li]Stuck caliper pin(s);[/li][li]Internally-failed brake hose;[/li][li]Faulty master cylinder (only one “channel” of the diagonal system working).[/li][/ul]

The car is up on jackstands in the driveway right now. I’m interested in any opinions on what tests I should perform, or what failure these symptoms may point to.

2

the piston in the left caliper may be sticking. with 240,000 miles you really should have rebuilt or replaced the calipers. If you’ve never flushed the brake system you really should do that as well. contaminants and sediment eventually do build up which leads to things like seized caliper pistons and leaking master cylinder seals.

another possibility- if movement of the left piston is verified as free- is that the inside of the rubber brake hose is breaking down. When that happens, a “flap” of rubber can lift up and act as a “check valve” and impede brake fluid flow in one direction.

3

Thanks. The calipers are original. I flush the brake fluid every three years, as recommended by the owner’s manual; this was last done a year ago.

I live in the famously-benign climate of Southern California, but yeah - nothing lasts forever. The “parts darts” approach would be to just replace everything from the brake hoses down on both sides, and given the ages of the components is probably a reasonable step, even if those things haven’t (yet) failed.

The time/money tradeoff right now would come down on the side of simply replacing the calipers, rather than taking the time to (learn how to) rebuild them.

I was mulling on this while at a party earlier this evening, when the master cylinder problem possibility occurred to me. Tomorrow I can check the rear (drum) brakes for uneven wear, and I’ve read of a test by which I have a friend run the wheels on jackstands and hit the brakes - one side not working would then be pretty apparent to somebody watching from outside.

Based on what I’m seeing, I would expect it to feel fine after replacing those parts - whether the problem was fixed or not (it feels fine now!). That’s disquieting.

4

Did you buy the car new or used? The problem you describe leads me to think that the brake pads are of different composition. Odd, yes, but perhaps the pad mfr changed lots between your right and left pads. Yes, very odd.

Also might the rotors be of different material?

5

Step firmly on the brake pedal, then release and see if the right front brake is hanging up (spin the wheel, compare to left side). If so, open the bleeder screw (prepare for fluid outrush, but at least make sure bleeder is not clogged). If it still sticks on, it’s the caliper. If that unsticks it, reapply pedal & release, then loosen fitting between steel brake line and hose. If it still sticks it’s the hose. If not it’s the master cylinder.

6

I’ve had the vehicle since new. All four brake pads are out of the same box - Wagner ThermoQuiet QC914.

I’ve used these pads several times before with good success (because Gary T has spoken highly of them, actually). One thing I noticed when I installed this set was that instead of having molded insulators on the back (like previous sets of the same part number), they had metal shims. I double-checked that it was the same part number when I installed them 11 months ago, because I thought that was odd. Maybe something changed - but they were all like that.

The rotors are were installed together, and are of the same part number - Wagner BD125669E. This was at about 194,000 miles.

7

Thanks, Gary. I’ll try this series of tests tomorrow.

8

Don’t forget that if you have ABS, after the master their is the modulator block for ABS. You’d want to troubleshoot that as well if it’s not the caliper or hose.

For what it’s worth, I had a 2004 Honda, similar situation with a sticky pin. Relubed and it all seemed good to go. My guess is that the forces applied while driving don’t match what I can do on a bench and I won’t do that again. Nothing scary happened but I had to replace that caliper anyways not too long later. Might as well do it at the first sign of excessive wear versus trying to get a little more out of it. It wasn’t that expensive either to buy the whole caliper with new pins and bracket, replaced all four while I was at it the second time to avoid having to do a “double-take” on the others since the age was all the same.

9

Disclaimer: ianacm (car mechanic)

brakes on cars are typically separated into 2 circuits: left front and right rear and right front and left rear. Under normal circumstances a car will operate fine with only one of the 2.

It sounds like one of the circuits isn’t workings properly.

I would urge you to get this looked at.

10

Some other far out but still possible things that come to mind, the above mentioned different pad types, even if you got them in the same box. Perhaps a wheel bearing is going and the brakes are holding the wheel in place. That should be accompanied by a noise particularly while steering in one direction. Perhaps something got in between the rotor and the mating surface on the hub causing it not to be flat against it. Is the pad worn flat even or at some angle?

With that said I suspect the caliper, 200k+ miles is a lot to ask of them and even if not it may be good to replace as preventive maintenance. Hose would be second on my list.

11

Some tests that can be helpful in gathering information is using a IR thermometer and driving the car, then get the temperature of the wheels, you can vary driving/braking on different tests to check consistency. Both sides should be similar. FOr a rough idea you can use your hand, you might burn yourself, so touch with care.

Additionally a mechanics microphone set, I forget what it is called, but something that will let you listen to a particular part of your car and also compare it to another part while you drive can help greatly in identifying what is wrong, especially in suspension and braking. For a quick and dirty approach you can having someone drive by you and listen as it goes by with various brake pressures and sides.