I put new rotors on last night (front only) and left my brake pads because they were still in good condition. I am going to turn the rears and put new pads on if needed this weekend.

Anyway, I was driving over to a friends last night after I put the rotors on and it felt like they were warped? (pedal pulse) These rotors are brand new. Is this normal?

 

If there was rust build up on the hubs the new rotors could be offset enough to wobble.

 

Hmmm that could be it, should I remove and clean the hubs?

 

I have been told in the past to use old brake pads to break in new rotors and old rotors to break in new pads.... you are saying this is not true?

I'll get the new pads tonight...

 

GM and many other sources say it is fine to use old pads with new rotors and vice versa.

I'd go with Fast One's suggestion. That seems much more likely.

 

My first recomendation is to check and make sure that there is no rust or dirt on the mating surface of the hub and the rotor. If that is good, they you may have received warped rotors. We have gotten brand new ones that were as much as .0026 out. The only way I know of checking them is with a dial indicator/run out gauge.

Good luck.

 

I am going to take em off again, clean the hubs and put on new pads...hopefully that will work! If not, I got warped rotors and am going to be :mad

 

Personally, I don't think anyone knows the answer to this question. Some people (rotor manufacturers) usually say that you need to "season" your new rotors before you can bed new pads. This implies that you should put on new rotors, and season them with your old pads. Once you've seasoned them, then you put on new pads and bed them. Other places say that you need to put new pads on when you put new rotors on.

I don't buy that the pads/rotors "form" to each other. You can change pads over and over, and as long as you bed them properly you don't need to change/resurface the rotors. There is a lot of good information at http://www.baer.com and http://www.stoptech.com (although, they often contradict each other.

Also, from what I understand, rotors almost NEVER warp. When you feel pulsing, its from a pad not being bedded properly.

 

When changing pads GM recommends the rotors not be resurfaced unless they are damaged so why shouldn't it go the other way. New rotors do not have any brake residue and whether the old pads are tapered or not you aren't going to get any pulsing. The worst thing is you might groove the rotors if the pads were grooved.

You probably have some rust build up around the hubs that will not allow the rotors to fit properly or you did not seat the rotors on the hub well when you reinstalled the wheels. I had this happen on a lot of my front wheel drive cars when changing brakes and found if I cleaned the bearing hub and made sure the rotor was seated properly while installing the wheel and tightening the lug nuts I didn't get any pulsation.

I have changed a lot of brake pads and rotors over the years and have never found a warped rotor. Although I did have pulsing on the front rotor of my 99 Tahoe it wasn't due to a warped rotor. There was a big hole (half dollar size) rusted in the back side of the rotor.

Do the simple things first. They usually work and save you a lot of money in the long run.

Bill

 

I went through the same thing turned out it was the rear rotors that were warped,it felt like the fronts were warped.Its really hard to tell from pedal feel if its the front or rear that are warped. Do yourself a favor and Turn or replace the rear rotors.

 

If your old pads are still in good shape you can reuse them by simply sanding them a little to rough up the pad and remove the "glaze" off them. They will then reseat to the new rotor.

I also agree with the other folks that you may not be fully seated behind the rotor or that you may have received a warped rotor. You do not have to purchase new pads when replacing rotors.

 

I agree with Capt. JeanlucPicard. He's never wrong. :thumbs: :lol: The glaze part of the pads will have some residue from the other rotors that u had on there and since rotors of different brands are made up of different metals, some of that glaze on the pads will still have that material on there from the old rotor, so when u reuse them without sanding the glaze off, it's like having 2 different types metal rubbing against each other. Thus the pulsating. Sand it down, slap it back on and I think u'll be fine. No need to buy new pads.

As for reseating new rotors with old pads and vice versa... to each it's own opinion. Think about it this way, when you buy a new car, the pads are new and so are the rotors.

 

You can never go wrong with new rotors and pads.

 

I have to say I think it's silly to save a few dollars by not replacing the pads and the rotors (Unless they are like brand new) when we spend so much money on MODS's. :lolg:

 

Ok - I cleaned up the hubs good and also replaced the pads with ceramic pads. I also made sure to seat the rotor on the hub correctly. Well guess what, I still have pedal pulse, not as bad but still there. I am 98% sure that it is the front since I can also feel it in the steering wheel at higher speeds....What now??????? Is it possible to get brand new rotors that are out of round??????? This is going to drive me crazy. :cuss

 

ttt

 

Okay JSCHELL;

According to my Helms manuals - er, you do have a set of Helms manuals for your car right? Anyway, according to my Helms manual, brake pedal pulsation can be caused by:

1. Warped rotors. You have apparently addressed this already.
2. Faulty real time dampening system module in your suspension.
3. Loose wheel bearing. Check for tight wheel fit. You might also want to make sure your alloy wheels do not have any trash behind them where the lug nuts go. Same issue as a rotor. Clean behind your wheel centers!
4. Improperly bled hydraulic brake lines. May sure all air is out of the system. You can pedal pump or use a bleeder pump (which is what I do).
5. Faulty bias spring in master brake cylinder. Replace.
6. Faulty antilock electronc brake control module. Should have a DIC code if this happens. Would have to go to dealer for a new module.

My guess is that you may have some air in the lines and that your rotors are still slightly warped. After cleaning behind your wheel centers (not the rotors) drive it and see if you still pulse. If so, I would take the car up to around 70 and stomp on the brakes (find a deserted stretch of road please) and do not hold the pads against the rotor after you stop. Take off again and cool the rotors down. Repeat this until you stop having the pulse - or run out of gas :D .

I have had my rotors warp and that's how I have corrected it. When you normally stop you hold the pedal down and the redhot pad sits against the rotor with all that heat in a small area. It will warp the rotor. You "unwarp" by reheating the rotor - DO NOT TURN THE ROTORS! Less metal means shorter life and more likely to warp. Give this low-tech method a shot and see what happens.

By the way, all rotors are warped a little. No way for them not to be.

Good luck. :cheers:

SAVE THE WAVE :seeya :cool: :cheers:

 

My first job out of school was selling brakes for Wagner Brakes. It wasn't uncommon to have new rotors show up warped. Many installers would throw them on the lathe and make one pass just to avoid the dreaded comeback. Your best bet is to get them turned. Go to a reputable shop or your dealer and have them do the job. It shouldn't be more than $25.

In all my dealings with disc brakes, I've never recommended to anyone to use their old pads. If your pads were wore unevenly at all (most are), your likely to do the same to your new rotors...not to mention the potential for squeals. While your used pads may be in good shape, I'm sure they have small groves in them. By using them, you are reducing the contact patch of pad to rotor. The pad will ride on it's ridges until it's worn flat. However, that means that your rotors aren't making full contact and are likely to get grooved.

Just my .02$.

-Mike, ASE Certified
'99 FRC

 

Actually its the racing pad manufacturers that recommend that you use old pads to break in new rotors and old rotors to break in new pads. I have received those written instructions from both Hawk and PFC many times. One thing you can say about both companies is that they should know what they are talking about. Not sure if the recommendation would apply to street brakes but I really do not see why not.
Bill

 

It is possible that the rotors are warped out of the factory... I thas happened to me before.... I hope you figure out which one it is and get it replaced pronto. :yesnod:

vetterdstr :cheers: