I recently bought a 2002 MCS and have noticed that once the brakes warm up, they start to vibrate as if the rotors were warped.

When the outside temperature was 35+, the brakes would vibrate from the start, but since its been in the 10's lately, the brakes don't vibrate at all until they've been warmed up from city driving for 15-20 minutes.

The previous owner replaced the all the brakes about 3000 miles ago. I'm just taking an educated guess, but would the vibration be caused from an improper break-in of the rotors? Any input would be appreciated. Thanks!

 

When you say "vibrate" - do you mean they "pulse" when you're using them?

Could be deposits on the rotors from improper pad bedding - do you see any deposits on the rotors or do they look "clean"?

 

I haven't looked at the rotors yet.

I suppose they "pulse" when I use them, just like warped rotors. There is no issue when they're not in use.

I will have to pull the wheels and check tomorrow. Winter wheels on right now (steelies), can't really see the rotors well.

 

Since the car is used, it's possible the rotors are warped. When I traded my 2003 in, it had warped rotors on it. I however gave the dealer the new pads and rotors and told them they could either replace them or give them to the new owner. It happens sometimes when people go to trade in vehicles. Check the brake fluid level too.

 

Normally I would think it was warped rotors, but the thing that makes me question it is the fact that there is no issue when they're cold. From personal experience, temperature has never played a roll with warped rotors.

 

We see this alot of times from cheap Autozone or Napa rotors. So If someone was getting ready to sell it they prob didn't spend money unless they had to, or maybe they never replaced the rotors.

 

All the rotors were replaced with OEM Mini and the pads were replaced with Metal Masters. The car came with every single service record, in and out of warranty, so it wouldn't be an issue of cheap rotors. The previous owner is a stand up guy, I have zero concerns as to the maintenance of this car. He suggested it may be deposits as well, so I will check that out first thing.

 

Sorry, while service records are good, it still doesn't mean that this guy didn't have to stop really, really, really quick one day. Say like to keep from rear ending somebody. That's all it would take to warp the rotors.

 

Don't get me wrong, I totally agree with you, it's definitely a possibility. But do warped rotors generally only pulse once they've been warmed up? When I've had warped rotors in the past, they've always pulsed, cold or warm.

 

I have driven a non-mini that only pulsed and vibrated after the brakes were warmed up....it happens. Brake job gone bad....perhaps the rotors were overheated during the bedding in of the new pads....very easy to do IMO if you do it wrong, or too agressivly.

 

If that is the case, I'll probably see if I can get them turned come this spring. I'm not about to pull rotors in sub freezing weather. Thanks everyone for your input.

 

they'll likely warp again . it's like welding; it distorts the metal if too much heat is applied . if you cool it you can pull it back, but if it gets hot again it will usually go back to it's distorted position . so when your rotors cool they may be straightening a bit and when you heat um back up they distort. break out the dial indicator when weather warms and hopefully it's just one or two .

 

LOL, I hear you. I'm waiting 'till Spring to do my clutch. Good luck with the rotors. You can have them turned, but as Herbie said, it's possible they will warp again. Sounds like you're not an aggressive driver, sooooo turning them might benefit you. If not, you can get some new rotors from Autozone or Napa and go with those. I've had good luck with those on my Suzuki Sidekick.

 

from my experience and what i have read there's no real such thing as rotor 'warp'.. it will take A LOT more heat to get a chunk of metal to actually warp. What's happening is uneven pad build up which is caused by overheating.. i get this at the track sometimes and there's some things you can do to prevent\get rid of this. Prevention - bed in your pads on a regular basis.. you need to get them hot to transfer brake pad material to the rotors - a nice even layer - which will also make your brakes work better.. this also prevents glazing. To get rid of uneven pad buildup shops will turn your rotors on a lathe, but many don't do that these days and just replace. I have a set of Ferodo 3000's (racing only compound) which i ran on the street for a few days to get rid of the buildup... with the aggressive pad material running below operating tempurature it will grind away at the existing pad buildup. You could try moving to a different pad compound and bedding in your brakes.. that might get rid of your old material..

 

How cool do you think brakes stay?
Rotors can actually be made so hot during indrusrty testing that they glow red!! While this kind of tempture extreme is unlikey on a street car, it is possible. Other causes of warpage includes overtighteng lug bolts with impact hammers, or even uneven cooling due to cold water getting splashed on rotors. While pad build-up can cause problems, since you rotors are fine cool, and they vibrate hot, this points strongly to warping.
The oem rotors I've seen are not even marked with min thickness, as they are not ment to be turned. Since labor is so $$$, I'd just toss new rotors on the car...a pair should cost less than $100, maybe even less depending on what you buy. And eitherway, I get new pads, as rebedding used pads on new or turned rotors could start you on this problemed path allover again!!

 

Well I finally got around to pulling the passenger side wheel and this is what the rotor looks like. From what I can tell this is definitely the cause of the vibration. How would I go about cleaning up this surface? Turning them or would a very light sanding do the trick?

 

Sanding will remove glaze and help new pads bed in....your only real option is to pull them off, and have the put on a lathe the recut them...since they are fine cool, and they seem to vibrate when heated, this could be a waste of money.
It does look like you have an intersting stain....Maybe a bad rotor?
With the marks like that on a newish rotor, I wonder if the pads are glazed/leaving deposts on your rotors....
I would do new pads and new rotors. If you have the rotors cut...the pads should still be replaced or bedin time may be long, and inital brake performance maybe dangerous till the pads are shaped to the newly flat rotors....IMO do it once, do it right, do it safe!!

 

When I zoomed in and looked at the rotor surface...wow...looks kinda bad...very irrigular, potmarked almost...kinda odd looking!!

 

Yeah... those should NOT look like that...

 

From research I've done, pitting can be caused by rotors that aren't used very often. The previous owner said that the car wasn't a daily driver and would sit for periods of time. That would explain the pitting and the marks left on it from the pads. I think come spring, I will get all the rotors resurfaced and pick up some new brake pads.

 

Pitting, scored surface finsh and a lot of other unsightly things do not cause pulsation in pedal. Go to Stoptech website and read White Paper on warped rotors written by Carroll Smith. (Warped rotors is mostly myth)

A few hard stops may knock pad build-up off rotors, but some pad materials seem to bild up high spots on rotors. Hawk DTC-70 pads seem to do it on Corvettes.

If you are not doing track time, switching to a cermic pad might fix this.

Also some people have had good success in cleaning rotors with coarse sandpaper.

 

Rotate that thing about ten degrees to the left and you'll see the entire pad print embedded onto the rotor. Either; hard stops with foot held onto the brake pedal (car automatic trans?) or sat overnight in the rain and bonded at that point.

Looking close I think I see another foot print to the left as well.

 

Yea they're all over the rotor. Do you think a light sanding would help in the meantime (before I can get the rotors turned and new pads)

 

I'd certainly try it. And hit the pads on some as well, then bed the pads a bit and see if the issues are gone. If you have it; a scotchbrite wheel on a air sander works well.