whenever i drive on the highway and have to brake hard (traffic moving at 60mph between stoplights on a certain stretch of highway) harsh vibrations shake the car until i decelerate down to 40mph (below 40 there are no vibrations). i had the brake pads changed, the rotors replaced, and the rear drums replaced and i changed up my driving/braking style a bit (drive a bit slower and brake alot sooner) so the problem is almost unnoticeable until i push the brakes hard enough. anyone else have this problem? is this something i should worry about? anything more i can do to fix this problem? thanks in advance for any help.


Blown.

sounds almost like you're experiencing your abs. is it just hard braking? or is it all braking? does the pedal move up and down? could also be tires, although i'm not sure why you would only feel tires on decel. but tires are normally the most common cause of vibrations.


-john

It is most definately without a doubt warped rotors and or drums. the best test is to do this. Get going however fast as you need, and hit the brakes and see if you can feel it in the wheel. Then get back up to speed and do use anything but the e-brake to slow you down and see if you still feel it. If you do with just the e-brake then it's warped drums. If you don't feel it at all with the e-brake then it's warped rotors. Just cuz the stuff is new doesn't mean they're not warped. I've seen very many rotors come off the shelf and need up to 30 thousandths cut off them before putting them on a vehicle.

its not all braking (even when braking hard below 40 mph). its ONLY when braking hard from highway speeds. and the pedal doesn't move. its just that the whole car shakes..just as if i were experiencing the abs, just as you said. but i'm hoping that its not the abs because i would have no idea how to fix that and my only option then would be to go to a dealership. maybe its normal and i'm just pushing too hard on the brakes?


Blown.

New pads and rotors can not come warped. Warped rotors/drums has nothing to do with the physical shape of the rotor/drum. It's deposits on the surfaces that causes variations in the friction coeffecient (different rates of braking as it goes round).

You can warp them quickly by doing a panic stop and then smashing the brake and "burning in" alot of pad material in one spot. Over time spots develop, and once started it slowly gets worse.

Also warped rotors/drums are usually very noticable at lower speeds. Does the vibration seem to be consistant with your speed? Or is it more of a constant pulse?

I think Filip's problem sounds like a ball joint. Does it shake worse when turning one direction, compared to turning the other direction? Jack the car up, grab the wheel and pull in in/out left/right; see if there is any movement at all at the ball joint (you need to be basically under the car during this to see it).

The problem does not sound like tires at all, tires would give you the most problems while crusing, not braking.

Could be the ABS system, but he would definaltely feel that pedal pulsing. Could be a bad sensor, or wiring. Considering it's 2 years old, I doubt he has ABS problems.

c.t.s: the vibration is consistent with my speed, with more of an extremely fast pulsation braking hard from highway speeds and a minor pulsation is felt when decelerating from 30mph. i guess what i'm trying to say is that when going slow, it is a softer pulsation that seems to 'grab then release' the car and at highway speeds it is quite loud and felt throughout the car, including in the steering wheel. turning has no effect on the braking (or vice versa), at least none that i have noticed. and i did have my driver's side control arm replaced a little while ago because one of the bushings was completely worn. you think that driving around like that before i had it replaced could have done something to the brakes or something else?


Blown.

Which bushing, the rear bushing is shot in 50% of car out there (I would guess).
I still think it might be a ball joint, but the warped brakes are sounding more likely since turning has not effect. Usually a bad ball joint will favor turning one way or another.

i have no idea which bushing, all i know is that i had to get my entire control arm replaced. i'm not at home so i can't go through the paperwork on it. but are we ruling out the abs even though the abs light doesn't come on? i keep thinking its the abs since i can feel the brakes grabbing the car and then releasing; its slower from low speeds and very harsh from high speeds.


Blown.

I gaurantee it's a warped rotor. I'm a certified ASE tech and he is explaining something that i hear everyday from customers. And i'm positive it's nothing to do with the ABS light. You would feel the pedal pulse and you can hear the ABS unit pulsate also. Also there is the fact that it's consistant with speed which goes back to a high/low spot on the rotor surface that would cause the vibration. And yes new rotors do come warped, i've seen very many times especially on cheaper brands.

Todd: you can take your ASE certification somewhere else, it's worth less than your opinion to me any many others here.

I agree that it isn't ABS. It wouldn't vary with the speed of the car, it would pulse at a consistant speed.

It does sound a lot like warped rotors. But I still would check the ball joint.

Both bushing can be removed from the control arm. I assume there was other damage, otherwise it would have been an unnecessary expense.

Was the car realligned after the new bushing was installed? Could it be bad alignment or camber? I don't know, im just throwing out suggestions... when was the last time you rotated your rotors or purchased new ones?

CTS : I'm not trying to start an argument here at all. I'm just trying to help him out with his problem. Now let's take into concideration of what he told us. He said vibration, and the WHOLE car shakes. I don't see where a bad ball joint only under hard braking is going to cause such a problem. You must remember that the lower ball joints on our cars are load bearing, meaning that there is weight on them unless it leaves the ground. And with weight on that ball joint it's not going to cause a vibration while braking. But if you want to discuss this more lets keep it out of this post, i hate to waste anymore of this guys time. e-mail me instead.

And as far as the alignment causing the vibration... definately not the case.

an alignment was done after the control arm was replaced. so let's say that it is rotors, right now i have stock rotors. any good brands i should look out for? and any good brands that have the rust-proofing (i think its zinc?)? a warped rotor makes sense, but since the control arm was dysfunctional for a while, im worried that the ball joint could be bad as well. i think i'm going to check that out as well once i find some time between projects and hw assignments. and for the record, i can hear a very distinct 'pulsation' from a high speed, not just feel it. and at low speeds it can't be heard, it only slightly pulsates (consistent with speed).


Blown.

ABS causes the wheels to not lock up when braking hard, hence the pulsating and shaking of the car (if you have ever experienced ABS, you know what I mean). *I am not saying this is the cause...just read on**

When you brake, the pads come in contact with the rotors (this is how you slow down, obviously). If you brake hard enough, the wheels begin to lock. ABS releases the pads for a split second to prevent the lock-up. (grab and release, as stated above)

"Quote"
its not all braking (even when braking hard below 40 mph). its ONLY when braking hard from highway speeds.

Sounds similair to ABS, but could be rotors are bad. If the pads were worn, you would hear a squeek every time you braked.

CTS: if the wheels aren't locking hard, the ABS would not kick in as hard, and the pulsating would be lighter. However, I do agree w. CTS on the "spots" on the rotors from panic stops, should also be considered as a possible cause. AND I agree w. Todd about the ball joint issue.

My suggestion: go drive around your block, and brake gradually and slowly (almost coasting to a stop). If you still shake, then it is something other then ABS.

Sam (at work and has to stop talking on the .ORG)


Ban low-performance cars, not high-performance ones.

Sam: if i do exactly what you stated then it is not the abs. its only under highway speeds and under normal driving it is a light 'grab and release'. it makes sense if the rotors were warped, as if the pads hit high/low spots on the rotors. it is consistent with speed. so i'm going to check out the ball joints and the rotors when i can.


Blown.

It is most likely NOT the ball joints. There is a greater possibility of the problem being caused by unevenly worn rotors, and you cannot check them by eye. They way to correctly see if there are high/low spots is with a micrometer, measuring all around the rotor and seeing any difference. Even a small .01" is enough.

Let me ask you some questions now: When you brake at "highway speed", does the pulsating slow down or cease as your speed decreases? Also, if you let off the gas pedal and not put your foot on the brake; but coast into a stop, does your car shake?

Sam


Ban low-performance cars, not high-performance ones.

The ball joints are not load bearing. Where do you think they get/support load??
All they do is stabilize the bottom of the steering knuckle.

I've had more than one go bad on me personally. Under breaking the whole car pulsated, the steering wheel vibrated a bit, and it was just the same as what he is describing.

Now I'm not saying that is definitely the problem, but it's quick and easy to check for, and inexpensive to fix (<$30).

Also. In case everyone has missed this point. He had the problem both before and after he changed the brake pads and rotors.

It could definitely still be the rotors. Especially if he didn't bed them. But I still think it could be the ball joint.

the car only shakes on decel if i touch the brakes. and it stays constant with the speed like i explained to cts...by that i mean when the car begins to slow down i can hear (and i guess feel) how the 'pulsation' slows down as well. from the suggestions i'm getting, though, i am very pressed to get new rotors. and i'd like to go for ones with the rust-proofing, and i have no idea where to get those. or at least one's that perform well.


Blown.

Word of advice: rotors with rust on them--the rust will come off when you brake. The friction created takes the rust off. For starters, price rotors for you car, or get them cut. If they are cheap, get new ones--no big deal. Measure them, like I stated before, to see if it is really the rotors. If there is some problem with your rotors, you have to trace it back, because rotors don't just wear unevenly for no reason. It can be the way you drive, the pads you have didn't seat correctly, low pressure in the brake line (or too much) or anything else, for that matter.

Rotors with a "rust coating" only wear off after you brake a few times. A coating is a layer.

Sam


Ban low-performance cars, not high-performance ones.

That rust coating is not meant to prevent rust where the pads make contact; and will not prevent rust there.
It prevents rust in the vanes, which is good for cooling; and it prevents rust on the outter rim, and inner hub, which just looks good but really serves little functional purpose.

Mostly, only performace rotors are available with a zinc coating.

Like Sam said, if you have warped rotors, they got that way for a reason. Any machine shop can turn (resurface) a rotor, if it's thick enough still (new ones should be plenty thick). In general you can resurface a rotor 2 (maybe 3) times, then it's done for.

Ban low-performance cars, not high-performance ones.

exactly - i didn't mean the area where the pad touches the rotor. i wanted a cleaner look because it just looks damn nasty with all the rust around the edge. my rotors are still pretty new but i was hoping to do a brake upgrade sometime, which is why i would like to get new rotors anyway. and a major possibility of how my rotors got the way they are (if it is the rotors) then it was my driving. i always braked too late, which meant i had to go hard on the pedal. i've stopped that and now i brake much sooner and don't have my foot on the gas looking to accelerate all the time. the wilwood kit is way out of my price range right now, so i planned on getting some powerslot rotors and better pads. by the way, thanks to everyone here who's helped me out (don't wanna single anyone out but i guess i will - cts and sam, thanks).


Blown.

Filip:

You mind sharing with us what fixed your problem in the end.

Thanks

Viera