Intermittent Brake Wobble (1 Viewer)

[Onefastrx7turbo]

The process of bedding the pads in isn't to seat them in the caliper grooves, but to evenly transfer the pad material into the disk surface in the hopes of creating a uniform friction surface. The pulsing/shimmy/vibration from braking is because the friction surface is uneven, and as the rotor spins, the brake pad encounters varying coefficient of friction levels.

 

[C6H12O6]

Got it. Thanks. I was thinking you were wearing the new pads down to match the contour of the rotor to achieve the "uniform friction surface." That makes sense, though.

Only problem is, this isn't that. My old Nissan pickup had issues where I would get the friction surface pulsing/vibration and I would go through the bedding procedure to take care of it. That was a much higher frequency pulse and I could feel it through the brake pedal. This is weird. The vibration is more side-to-side, there is no brake pedal feedback, and it is much slower in frequency. Slow enough that it isn't anywhere near the RPM of the turning wheel. Hard to explain. It changes with vehicle speed, but the wobble is slower than that.

I just ordered new longer OEM soft hoses all around. Still up in the air about the calipers. I bought some at Napa for $57 each up front. Dealer remans are only $30 more each side. I also ordered new thrust washers for the front end. I'll re-adjust the wheel bearings with the new washers and drive it around a bit, then tackle the brakes. I'll follow a proper bedding procedure and see how it goes.

Thanks for the help.

 

[BreckenridgeCruiser]

It's only when braking? Not when hitting a bump or coasting? Just checking...

 

[C6H12O6]

Just when braking, yes. Drives and coasts great and even brakes fine 90% of the time.

 

[97 greenmonster]

I actually have same issue. At first I thought it was my tire pressure it was off so fixed that. That seem to help but came back. So figured it was old worn tires put new ones on and it seemed to go away. But came back. Then I checked my bearing and the driver side was loose so I tighten it down and seemed to help but then again came back. It's odd only does it going down hill stoping from like 45 mph I get slight wobble on steering wheel. Every time I thought I figured it out it was still there. Got new rotors and pads to do next.

 

[C6H12O6]

I replaced my rotors and pads a couple years ago. The problems started not too long after. Pretty strange.

I'm going to try to find some flat ground and jack it up to check the whole front end out again, a la Landtank's testing procedures. Trunion bearings, wheel bearings, OEM calipers, OEM tie rods/ends, steering gear box, OME shocks all replaced within the last 10K miles. I'm stumped.

My wobble started off slight, too. It's gotten progressively worse over the last year. Hopefully, I'll be able to figure it out this weekend.

 

[BILT4ME]

When you installed you rotors, did you torque them properly and evenly with a torque wrench where they attach to the hub?

 

[C6H12O6]

Oh, and tires.

 

[C6H12O6]

Yes, torque wrench used for everything.

 

[baggar11]

I had this problem on my Cruiser for years. Took me a while to track it down. It seemed to be worse with downhills and/or when the braking system heated up. It was the cylinders in the calipers all along. They were pitted and gross.

Either rebuild and cleanup the calipers or get new ones. I've been problem free for a couple years now. Good luck!

 

[C6H12O6]

I thought about having the rotors checked, but I'm still stumped by the fact that it can be downright scary to stop at a light, then I take off at the green light and everything might be totally fine. I would think that any rotor problems would not react that way.

 

[C6H12O6]

Thanks, Baggar11. I have reman. Napa calipers in the garage right now. Waiting on Toyota for the new brake lines to come in and I'll do it all at once. Still trying to decide if the Toyota reman. calipers are worth the extra $60.

Of course they are. Stupid. I should just call Toyota and add them to the order. The front pads have plenty of life on them. Should I still replace them with new after the caliper swap?

 

[baggar11]

Thanks, Baggar11. I have reman. Napa calipers in the garage right now. Waiting on Toyota for the new brake lines to come in and I'll do it all at once. Still trying to decide if the Toyota reman. calipers are worth the extra $60.

Of course they are. Stupid. I should just call Toyota and add them to the order. The front pads have plenty of life on them. Should I still replace them with new after the caliper swap?

For what it's worth, I ended up replacing my calipers with Centrics. They look and function the same as the Toyota's that I pulled off. Except of course, they didn't have any pitting on the cylinders.

 

[94L C8E]

hey all,
i've been keenly following this thread: might have just cured a similar (real identical) issue, and wanted to share:

 

[94L C8E]

- i'd suggest checking your rear brakes: check brake pads for uneven wear, and try pushing in your rear caliper pistons with a hammer handle (see FSM) and see if they're seized. And try removing old/ adding clean brake fluid to your MC res.
*i used a Method Dish Soap dispenser/bottle to suck out the MC res, up the spout into the soap bottle.

I had an intermittent brake pulsation issue a couple of years ago. It wasn't due to loose bearings or any other bearing or steering component. I was going to change the brake pads even though they weren't worn, but then the problem went away and hasn't come back.

I replaced my rotors and pads a couple years ago. The problems started not too long after. Pretty strange.

... opps blame for double post: Anyway, I got my '94 not too long ago and i'm still working thru PM...

Tonight I took out my rear pads: did one side at a time: D/S then P/S
saw bit of uneven pad wear; piston side pad was more worn, but had a few mm life; so i removed/ cleaned all the crud off the 4 support plates, 1 at a time, reinstalled; swapped the pads around, putting the less worn on the inside/ piston side.
Next, i couldn't for the life of me push the piston in with a hammer handle, so i grabbed a big clamp, and it easily went in under the power of a screw... put it all back together, etc, etc,..
I did the same procedure on both rear sides.
I also cleaned a lot of (21 years) of brake dust and crud with soap and water, off the insides of my rear rims)

* i made double sure to press the rotor and wheel as centered as possible as i was tightening the lugs in the 6-star pattern ('94 is lug centric) and so it's important to tighten the lugs by hand a bit at a time, in the factory pattern; after i tightened it up, i lowered jacked vehicle, and in the same 6 star pattern i torqued the wheel lugs to 108 ft/LB.

- oh, also, i again removed more dark fluid, after pushing the second piston in and then refilled to spec with new dot 3 brake fluid.


Drove around and my intermittent brake wobble is GONE. GONE.

- i'll report back after more driving, but i'd suggest checking your rear brakes.

 

[C6H12O6]

Update:
I replaced the front calipers with Toyota remans, replaced all the front rubber brake hoses, then replaced the thrust washers and lock washers and re-adjusted the wheel bearing preload. After bedding in the brakes, bleeding just the fronts, a couple short test drives around town and a long trip up to the mountains, the wobble is completely gone!

My local dealer screwed up my order, so I'll finish the rears when school gets out, but so far so good. Braking is not as good as I'd hoped, but I'm saving judgement there until I finish the rears, put new pads in front and back, and bleed the whole system correctly.

Only concerns I had were some slight cracking of the right front outer pad surface and some corresponding discoloration of the rotor. Nothing too bad, it just looks like things were sticking and getting hot. I had to re-use the old pads for now, but I'll swap them out when I order the last few parts I need from CDan.

 

[C6H12O6]

Well, crap. I even waited a week before I typed the last update and I still jinxed myself. Drove down the hill in 90 degree bumper-to-bumper traffic and my old friend is back. MUCH less than before, but back nonetheless.

Not as much wobble back and forth and not much in the steering wheel like before, so I'm thinking the wheel bearings bent locked down took care of that. This is the pulsing brake wobble. It seems like the left and right are almost taking turns braking. Crap. Back to the drawing board.

 

[Onefastrx7turbo]

Have you checked the alignment and wheel balance?

 

[C6H12O6]

Wheels were balanced when I replaced the tires last month.

Alignment probably needs to be checked, but I want to do the bushings up front this summer before I have the alignment done. The rear bushings were shot when I replaced them last year. I have the fronts in the garage, but no access to a bushing press. I'll probably end up buying one this summer.

I'm really getting bummed out. I've neglected so many little things over the last few years that the list of things to fix/check is just getting out of hand. I'm making incremental improvements to the truck that I know are needed regardless of this wobbling/brake pulsing issue, but I'd really like to solve this problem. While things like the bushings, alignment, etc. probably need to be looked at, I really feel like it is a brake issue. Even when the wheel bearings were a little loose, I think the main issue is brakes. The loose bearings might have exacerbated the problem, but it drives and handles just fine other than this brake issue.

I'm hoping that finishing the rear brakes, getting new pads all around and bleeding things properly will take care of this. Even when it isn't wobbling badly, I'm still getting a little bit of pulse/surge to the brakes as I come to a stop. I just don't know enough about it to be able to tell if the rears are causing troubles or where else to look. I really don't want to keep throwing parts at this issue by replacing the 18-month-old OEM rotors, just to see if they are the problem. The pedal isn't very firm and will drop down a bit after you pump up pressure, so maybe master cylinder should be done when I finish the soft lines in the rear. I don't know. Getting pretty frustrated, but I suppose that's all part of the decision to daily drive a 20-year-old truck with 250,000 miles on the clock.

 

[ton504]

Prob bushings. If its a tire balance issue then it would happening all the time. Toe in or toe out causing vibrations? Prob not. Worn bushings? Yea