Front end vibaration while braking

Maintenance/Repairs
1

Hi. This is a 1996 Toyota Tacoma, 2WD, 2.4L. When I apply the brakes I get a very heavy vibration in the front end, almost like a wobble. The vehicle otherwise stops fine. No noises. The vibration occurs at pretty much any speed over 20 mph. The frequency does not seem tied to the actual speed but it’s hard to tell for sure. It does not do it when I apply the emergency brake only.

I replaced the front disk brake pads, with new clips and shims. There were worn down pretty far and needed replacing. Unfortunately that did not make any difference in the vibration. Rotor runout and minumum thickness were checked while changing the disk brake pads and both were within specs. I did a quick inspection of the ball joints and tie rod ends by trying to move the tire and everything seems tight enough.

I’m not very proficient on suspension issues. What else can I look for.

Thanks

Curt

2

@Raindem

“Rotor runout and minimum thickness were checked while changing the disk brake pads and both were within specs.”

If they were checked, tell us how much runout the rotors had

I believe the rotors had excessive runout and should be replaced, based on your symptoms

Maybe the mechanic didn’t measure runout properly, maybe he only measured runout on one rotor. Maybe he has no idea what acceptable runout is

Bottom line . . . I think the guy should have machined or replaced the rotors. I don’t know how much runout they had, or how thick the rotors were, so the easiest thing is to replace the rotors

3

How were the rotors measured for runout and what were the results? If the car had a brake pulsation replacing the pads alone would make no difference. It’s a rotor issue.

4

@Raindem
"When I apply the brakes I get a very heavy vibration in the front end, almost like a wobble."
“I replaced the front disk brake pads, with new clips and shims. There were worn down pretty far and needed replacing. Unfortunately that did not make any difference in the vibration.”

I agree with @db4690… Since it was shuddering before the pads were replaced and shuddering after the pads were replaced, and since it’s mainly rotors that would cause this and you replaced only pads, then you should have replaced the rotors,too.

I replace pads only, without rotors, only when the brakes are functioning properly. If it’s shuddering you need the whole works.

Of course, weak/worn front suspension/steering components will exacerbate the problem and the front-end should be safety checked.
CSA

5

I agree with the earlier posters, rotors are most likely your problem. Were they checked for thickness variation (TV), too? Runout only shows half the answer. Hard spots can develop at a spot or 2 on the rotor(s) that can cause pulsing even when the rotors measure correctly for runout but not TV.

6

@Mustangman
Another week, then M-T Bradenton, W- Th-F, St.Pete.
CSA

7

Also agree with others. I am not even sure given your complaints and the fact that the other components checked out fine, I would have bothered measuring rotors. Would have just changed them. Now you need another set of new pads and rotors.
Rotors are relatively cheap today and labor rates are not that low, so I always change the rotors when in doubt.

8

Thanks for the replies.

I checked the runout wih a dial gauge. It was less than .003. My gauge reads in .001 so I’m estimating the runout at .0025. Maximum is listed as .0028 so I guess this is close enough to be suspect.

Minumum rotor thickness was checked with a mic and was .846. Spec is .787. I didn’t specifically check variation but IIRC it was no more than .01

Note that the symptim is not a pulsation in the pedal. It is a vibration in the front end. It’s similar to the vibration you’d get if the front tires were out of balance. So I don’t know if this is a brake problem, or a suspension problem that shows up only while braking.

9

The runout isn’t the cause of the vibration, it is the thickness variation.
The thickness variation limit is usually .0005", much less than the runout tolerance.

The thickness of a worn rotor will vary at different radius points on the rotor, the inside, center and outer surface of the rotor wear at different rates. Therefore you must measure the thickness at the same radius point in several positions on the rotor to determine if it is out of specs.

The standard procedure in the shop when there is a brake vibration is to resurface or replace the rotors (given there is nothing loose in the steering), don’t waste your time trying to measure thickness variation.

10

With all due respect . . .

What’s the point of arguing if rotor thickness variation or runout is causing OP’s problem?

It’s safe to say we’re all in agreement, that the rotors should have been machined and/or replaced, as needed

11

@Raindem
"Note that the symptim is not a pulsation in the pedal. It is a vibration in the front end. It’s similar to the vibration you’d get if the front tires were out of balance. So I don’t know if this is a brake problem, or a suspension problem that shows up only while braking."

The only time I’ve experienced what you’re describing is when a caliper or calipers (and installed brake pads) stop “floating” (lose lateral movement) in their mounting hardware because slides and pins were not clean and free of corrosion.

Did you thoroughly clean and lubricate these components when you replaced the pads and check to be sure the calipers were free to move?

Also, were the old pads worn evenly in thickness or were the inner pads noticeably thinner than outer pads?

CSA

12

I don’t see anybody arguing, people should understand why brakes vibrate/pulsate while the runout is within specifications.

13

No, I didn’t lubricate anything. I just removed the 1 bolt, swung the caliper up, and swapped out the pads.

On the left side the inner pad was worn much thinner than the outer. And it was uneven, with the greater wear in front.

14

@Raindem
Disclaimer-I’m not a trained technician, just a drive-way DIY “mechanic”. You’ll have to evaluate the support or flak I receive from this opinion.

“No, I didn’t lubricate anything. I just removed the 1 bolt, swung the caliper up, and swapped out the pads.”

It could be that one of the calipers/pads were seizing in their mounts (not the piston) because of corrosion before you did the brake pad replacement and that caused the vibration (explained later). Since you didn’t clean and lube anything then problem continued after the replacement.

“On the left side the inner pad was worn much thinner than the outer. And it was uneven, with the greater wear in front.”

The smoking gun? To me this is the smoking gun that indicates that my theory is correct. I seldom replace pads only, without rotors and this is one more reason. When replacing rotors on my vehicles the calipers must be remove (except hydraulic hose). At that point I thoroughly clean all mounting surfaces for calipers and pads, any pins etcetera, and lube everything carefully (Messy, I use wire brushes, files, drill w/brush, etcetera.) I grab the caliper after installation and make sure it is free to move.

My Theory-Here’s what happens…
When the brakes are applied to stop the piston presses the inboard pad against the rotor. That causes the caliper to “pull” the outer pad against the rotor and both apply fairly equal pad pressure to both sides of the rotor. Also, there is a little wiggle room to compensate for small amounts of rotor run-out because the caliper and pads can wiggle with the rotor.

When the caliper and or pads can’t move laterally then the caliper piston presses the pad against the rotor, but the outer pad does not get pulled against the rotor with as much force if the caliper and/or pads can’t move inward. This wears the inner pad faster. Also, the wiggle room is eliminates and any run-out existing in the rotor is transferred to the caliper carrier and car. That’s why the car shudders, rather than the steering wheel alone. More pedal pressure is required and still does not deliver full braking power!

Let me guess, You live where road salt is used during the winter months. I do and that’s why I know about this. Been there, done that.

Solution? Why not just replace pads and rotors, clean and lube attaching parts thoroughly and make sure everything moves.

CSA

15

@Raindem
Here’s a good link: It even shows a photo of pads that fit your description!
http://www.aa1car.com/library/brake_calipers.htm
CSA

16

CSA, thanks for the info and the link.

I remeasured rotor thickness to check for variation, using a 1" mic at several points around the disk. On both wheels the variance was .002, which is greater than the .0005 spec that Nevada_545 posted.

So yes, I will replace the rotors. Pads are brand new so they’ll be going back on.

17

I’m not hearing the support. I’m not getting any flak. Let’s hear other comments.
CSA

18

Variation no more than .01? If the numbers and decimal point are correct no wonder…among other things.

19

@“common sense answer”

“I’m not hearing the support”

Here you go :star:

Just like in elementary school :tongue:

20

@db4690
"Here you go :star:
Just like in elementary school :tongue:"
Thanks, db. Thanks for responding and the star. I guess you generally support the theory that seizing caliper attaching hardware was the major culprit, then? I’m trying to be sure I’m not overlooking something and giving bo-o-o-gus advice.
CSA