Severe brake pulsating. Help!

[menacekustoms]

So, when I bought my Q, it had a bad ABS (speed) sensor on the driver's front wheel. Well, to be specific, it was hanging from the knuckle, but that's aside from the point. I installed a new (from the dealer) front speed sensor, which turned off all the lights on the dash (yeah for that). However, I still have a severe, but intermittent brake pulsation problem. It shakes the whole car. Since it comes and goes, it can't be the rotors. What are some ideas? I'm sure that maxnix will tell me to search and look in the FSM, but I need some real help.

[Infinitiguy19]

Its sounds like the rotors to me buddy, Sorry.

But the car shake while braking or not?

[maxnix]

How about some maintenance history, especially on the suspension? Tire and wheel data? Air pressure?

Non-stock suspension, right?

[Aussie-Q'er]

Is it active suspension?

[maxnix]

Is it active suspension?

No active nor even variable rate shocks on 1997 FGY33 in the US.

[menacekustoms]

I'm unsure as to maintenance history since I just bought the car. It has KYB SR struts and Espelir lowering springs all the way around. The pads have pretty decent amounts of material left on them, I would say more than half. The rotors show no signs of hot spotting or warpage. It really can't be the rotors because it doesn't always do it. Everything in the suspension looks tight and in decent shape, except for the tension rods. They seem to be worn and leaking? Are they fluid filled? I seem to think though, that the tension rods are damaged because of the shaking.

[maxnix]

Well start by replacing known failed components, in this case the tension rod bushings.

It would be good to know if the strut bearings in front were also replaced when thee strut inserts were.

Wheel and tire data?


Modified by maxnix at 6:13 PM 11/26/2008

[menacekustoms]

Sorry, stock wheels with Michelin Energy tires in 215/60/16. Tread is in good shape. No visible bubbles or feathering or cupping that I can see. Rides smooth as glass when you're driving. It seems also, like the pulsating/shaking goes away as the car slows down.

[bullittandy]

It is weird that the problem is intermittent. If the tension rods are bad (which can be said with about 50% accuracy without even seeing these cars) then start there (you need them anyways so you won't waste money). They locate the entire front suspension and I could easily see the front wheels shaking if they were bad.

My guess is that the wheels shake when they are pointed straight but any kind of load or angle changes the angle of the suspension and tightens it up.

[menacekustoms]

Well, all I can say is, it's BAD. It's most notable above 40 or 45 mph and it's from right when you step on the brakes and it shakes severely, but as the car slows down, it goes away. I know I said it, but it's bad. Andy, did you get my last e-mail about those parts?

[miata007]

Should go have your rotors measured. A # of places will do that for you for free. If it is thin, it will cause this pulsation you are mentioning.

007

[maxnix]

Should go have your rotors measured. A # of places will do that for you for free. If it is thin, it will cause this pulsation you are mentioning.

Although there is a too thin specification, it is the differences between the thicker and thinner areas of both surfaces from parallel to the center plane of the rotor.

Amazing that anyone would drive a car that was so severely malfunctioning.

[oldmako]

You say that the problem is intermittent....can you be more specific? IOW, does it always do it on initial brake application (particularly at speeds above 40 or so??)? Are there times when you jump on the brakes (at speed) and it stops smoothly and without vibration?

A beat up set of rotors isn't so bad at slow speed deceleration but will ALWAYS shake when you get on the brakes firmly (and stay on them) from a hi-speed stop.

Dunno, seems to me as though you ought to slap a new set of pads on it and have the rotors turned at the same time. The whole shebang will only set you back a few hours and less than a hundred bucks. If that doesn't fix the prob, you'll have nice new binders and will have eliminated one source of the shimmy...all for less than a C note.

I hate warped rotors and their resultant shake. I replace stuff like that immediately because it drives me batschitt. Minimal cash, easy to do, and stomping on new brakes is a schweeeeeeeeeeet sensation.

Good luck with the shakes.

[menacekustoms]

Although there is a too thin specification, it is the differences between the thicker and thinner areas of both surfaces from parallel to the center plane of the rotor.

Amazing that anyone would drive a car that was so severely malfunctioning.

I know I'm the new guy around here, but you can really be a jerk! How do you diagnose a brake issue without driving it? I don't drive it on a daily basis. It has sat in my driveway a mojority of the time since I have owned it. I don't just drive it around with that kind of malfunction. Just because there are other idiots around, doesn't mean you can automatically group me in with them.

PS, I'm probably gonna throw some brakes on it, just to be safe.

[Kiven422]

I hate warped rotors and their resultant shake. I replace stuff like that immediately because it drives me batschitt. Minimal cash, easy to do, and stomping on new brakes is a schweeeeeeeeeeet sensation.

gosh cant wait for that... right now my front driver side rotor is warped real bad

i have the same problem you have menace, it shakes the whole car when i get on the brakes but not all the time... i know its my rotors, i just replaced all pads couple months ago and they still have more than 70% pad left

[TheJerseydude]

i had the same problem a couplemonths ago...its def the rotars... like an idiot i went n changed the brake caliper on the drivers side also which i didnt need to do... jus take care of ur rotars n the pulsatiung will stop

[menacekustoms]

Well, the car is down because of the knock sensors, so while it is, I will take car of the rotors for sure.

[maxnix]

you can really be a jerk! How do you diagnose a brake issue without driving it? I don't drive it on a daily basis.

By your description of the severity of the symptoms, I am glad I won't meet you on the road somewhere. The fact that you drive it at all in that dangerous condition is what is so perplexing.

Parking it = smart. Driving it = stupid.

[menacekustoms]

Well, it's parked so you should be happy. And how do you ever know if something is fixed without test driving it? I figured the pulsating was ABS sensor related, so I drove it around the block to see if the problem was still there. Jeez.