Ok ...this one has me baffled. The vehicle is a 2003 Toyota 4runner. Disk brakes on all wheels. I replaced the rear rotors and pads because I perceived a throbbing in the Pedal and it sure felt like a rear brake rotor was warped. Now, with new rotors and pads I have noticed that when I stop hard...it is very smooth. I stop gradually it is also very smooth...but if I stop with medium brake peddle pressure there is a throbbing in the peddle. It feels like a warped rotor...but I am not convinced. Any suggestions?
Rear Brake Rotor feels warped sometimes?
- Thread starter Dagwood
- Start date
- Status
The best way to tell if the rear rotors are warped is to apply the parking brake while driving. Keep your hand or thumb on the release lever so as to not lock it into position while you are driving. If there was any oil, finger prints or grease on the rotor you may have this.
Try using some brake cleaner again on the rotors. You do not have to remove the pads. Just spin the rotors.
What brand of rotor did you buy?
Try using some brake cleaner again on the rotors. You do not have to remove the pads. Just spin the rotors.
What brand of rotor did you buy?
The parking brakes for the rear on this vehicle are drum brakes. The rotors have a drum in them. I tried the same thing you suggested, until replaced the rotors and discovered that the parking brake is a drum assembly that is independent from the calipers.
I think I will try some brake cleaner and see if that helps. I always spray everything down with brake cleaner when I am finished. I might have missed something. It could be possible that I got a bit of brake grease on one of the pads. Or maybe a smudge on the rotor. The rotors are made by "GREN" by the way.
I think I will try some brake cleaner and see if that helps. I always spray everything down with brake cleaner when I am finished. I might have missed something. It could be possible that I got a bit of brake grease on one of the pads. Or maybe a smudge on the rotor. The rotors are made by "GREN" by the way.
How about ABS feedback?
You know...sometimes I do feel a minor buzz in the peddle. I was considering adding fresh fluid and bleeding the calipers.
Just how could the fluid be causing the problem? Too many people here are obsessed with bleeding the brakes, and see it as the answer to every problem. The only problem it really fixes is a spongy pedal.
Fresh brake fluid removes moisture in the system (in a logical sense, it doesn't remove it 100% but it replaces moisture-laden fluid with fluid of less mositure content.This is speaking of everything but dot 5 silicone fluid; all hygroscopic DOT 3,4,5.1). Moisture in the brakes, that is a problem, no? Moisture in the system degrades the hydraulic efficency. It's not the answer to every brake problem, of course, but you can't simply ignore this maintainence step just because it doesn't fix every problem. Brake fluid also has certain anti-wear and anti-corrosion additives that break down from the heat cycles of the brakes or just from normal use of the additives. Flushes/bleeds replenish these additives. Maximum water content usually reaches about 3%; this is readily handled by the corrosion inhibitors in the fluid. But as these glycol-based fluid inhibitors get depleted, they need to get replaced, just as motor oil and coolant does. Of course all DOT 3/4/5.1 brake fluids are synthetic in nature, polyglycol ether based with DOT 4 containing borate esters.
I was pretty darn careful about over-tightening my lug nuts. I used a torque wrench to just over 80 lbs. each. When I completed the brake job and drove with the new rotors it was just fine. It then got progressively worse. It is not terrible, just a nuisance on a long,firm stop. During a long, gradual stop you cannot detect anything. During a very short hard stop you can't feel it either. The original rotors started doing the same thing, but after 60,000 miles. I will most likely have them turned and reinstall them to see if that solves the problem.
When you installed the rotors, were you able to turn them freely? Is it possible the parking adjustment was to tight causing the rotors to over heat? If not, then you got a bad set of rotors. It happens with aftermarket stuff.
If it was fine before the brake job, and pulsating after, most likely it is a warped rotor or drum due to over tightening the lug nuts.
bad parts happen period, aftermarket or not. someone manufactures them, and mistakes happen during manufacturing and assembly.
Dagwood,
Putting a dial indicator on the rotor (wheel removed, bolts on)and/or hub will tell the story. Rotor/hub runout needs to be within factory specs. I chased a brake shudder for years on my Avalon until I purchased & used a dial indicator - found hub runout & fixed it with a runout correction plate from www.brakealign.com.
Also, with a dial indicator you can rotate the rotor relative to the hub to minimize runout.
Good luck.
Tom
Putting a dial indicator on the rotor (wheel removed, bolts on)and/or hub will tell the story. Rotor/hub runout needs to be within factory specs. I chased a brake shudder for years on my Avalon until I purchased & used a dial indicator - found hub runout & fixed it with a runout correction plate from www.brakealign.com.
Also, with a dial indicator you can rotate the rotor relative to the hub to minimize runout.
Good luck.
Tom
Thanks Tom. I think that is the way to go. You might have something there.
Some experts are of the opinion that pad material transfer is responsible for the majority of disc brake shudder (and I am reading more and more about it on Acurazine.com forums).
It seems a real possibility on my car also, as I am getting what seems to be almost random occurrances of brake shudder. Certainly if no physical runout can be measured, then it seems plausible. What thinks you? Here's the most thorough explanation I've seen: Stoptech article
It seems a real possibility on my car also, as I am getting what seems to be almost random occurrances of brake shudder. Certainly if no physical runout can be measured, then it seems plausible. What thinks you? Here's the most thorough explanation I've seen: Stoptech article
Absolutely. It was the major cause of pulsation/shudder on the vehicles I saw in the shop. It is amazing how much runout you can get away with and not have any noticeable symptoms. The problem is once it starts (lining transfer) it tends to get worse. Many techs turn/machine the rotors without checking runout first, and when that fixes it, it is erroniously assumed the rotors were warped to begin with.
As tomit said, check the hub/rotor interface. Sometimes alittle dirt, rust, etc. can cause the runout problems too. I've "fixed" alot of my friends "warped" rotors by simply pulling them off and cleaning the hub.
That would be the least expense solution. All you need is brake cleaner. I might give that a try first. Thanks gentlemen!
Thought I would post a follow-up. I had the original rear rotors turned today. It only cost me $10 per rotor. They were out about .006". I scuffed up the pads with sandpaper. I sprayed everything down with brake cleaner. I carefully applied a high quality brake grease to the caliper slots and slides. Put the pads back and tightened everything back up. Stopping is smooth as silk. Thanks to everyone for your help.
- Status
