Rotor warped? or not?

[ajchien]

I've got a confusing problem.

Rarely when I brake, the steering wheel will vibrate back and forth, classic for a warped front rotor.

However, my problem is that it happens, maybe only once or twice or never during a car trip. Intermittent and infrequent. Can be at any speed.

Still assume its a rotor and have them machined? Or look for something else?

 

[postjeeprcr]

How do your shocks look? Do they look like they are leaking oil?

 

[gtx510]

What vehicle and mileage? Could be a worn suspension bushing?

 

[doubleclutch]

Sticking caliper(s)? I have never had a warped rotor vibrate occasionally. Have you had your tires rotated lately? Those air guns in the hands of the untrained or uncaring, will warp a rotor in an instant. Some models are more prone to warp also. Our '95 T Bird is one example. They will warp in a heartbeat.

 

[Pablo]

If all your suspension parts are in good shape, the intermittent nature makes me think of poor rotor metallurgy. In other words your rotors may have relatively soft and hard sections (simplistic view) and when you drive ~ just depending on the current and previous friction (heat) cycle the rotors will not behave uniformly.

 

[duaneb9729]

we had this same problem in a one ton van recently and found it was a wheel bearing that was bad.

it was a 2004 chev G3500 if that helps

 

[PandaBear]

Originally Posted By: Pablo
poor rotor metallurgy


+1

Most warp rotors are poorly cast, not because of wear and tear.

 

[mechtech2]

Probably a rotor.
When you get it fixed, I recommend new cheap Chinese rotors instead of machining the old ones. [and new pads]

Want to buy expensive name brands? There is no guarantee they are not similar to the 'white box' type anymore.

 

[PandaBear]

Originally Posted By: mechtech2
I recommend new cheap Chinese rotors instead of machining the old ones. [and new pads]


Dad's mechanic just machined the old rotors and the problem came back shortly after. I am going to replace the rotor with a reputable value brand/model next time around, heard that Autozone Duralast gold was very good despite made in China, and have converts that used to use nothing but Brembo rotors.

 

[ArrestMeRedZ]

Very common problem in GM F-bodies. Mine were warped well before 10k miles, before the car had ever seen the track, or any form of hard use. GM service bulletin called for them to be machined. I considered that a waste of time, as the F-body sites indicated they would warp again in a few hundred miles.

I replaced them with Brembo blanks that were cryo treated. Not sure if the cryo treatment helps, but considering the marginal extra cost and the fact I'm lazy and don't like to do the same job twice, it was worth it to me to go for the snake oil. Went with Autozone ceramic pads.

So far, no problem with the new setup.

 

[ajchien]

Visually and crow bar stressed the shocks, springs, suspension, checked out the brakes. Except for pads being at 3-4mm, due soon for change, everything seems good.

Yeah, recently had a flat and tire place put on new tire.
Retorqued the lug nuts, and ... the vibration is still intermittent, but *less prominent*. Hmm.... Retorqued them again, will update you again later.

 

[ARB1977]

I replaced my rotors six months ago with the same issue on my Tacoma...the issue hasnt come back.

 

[tom slick]

I had the same issue and it was a slightly warped rear rotor.

 

[rpn453]

The rotors on my mother's Sunfire seemed to be warped (based on braking feel) when I changed out the original pads at 130k, so I also installed the premium NAPA made-in-USA rotors while I was at it. I drove the car a few months later, and was unimpressed that the new rotors had warped again so soon. The brake pads - $25 Jasper semi-metallics - were worn out in only 70k km, so I decided to try something else and installed $65 NAPA ceramics. I assumed the warping was inevitable with such small rotors so I left them alone. I drove it after installing the brakes and then again a few weeks later, and was surprised to find that the brakes felt smooth. Maybe the cheap pads were depositing material on the rotor and causing that feeling? I don't drive it often enough to say anything for sure, but I'll take it for a spin next time I get a chance.

 

[kgb007stb]

Rotor warping rarely if ever happens. Most people mistake rotor warping for uneven deposits which create different heat spikes throughout the rotor. Early uneven rotor deposition can be treated to some extent, but once left for too long it will permanently damage the rotor. As different surface parts heat and cool at different rates, permanent rotor damage happens. People thinking that rotors are warped, re-surface only to have the problem re-appear fairly quickly, this being due to the damage already done. Now the re-surfaced rotor has permanent damage which only a brand new replacement will cure.

Had the rotor not had uneven surface deposits, therefore even heat distribution re-surfacing would cure the problem.

 

[Tosh]

The factory front rotors on my 2001 Acura CL warped around 25k (and warped again in the same mileage when replaced under warranty). And they're not hot spots, as I measured perfect sinusoidal runout of 0.001 inch on both (cold, with a 0.00025 inch indicator), which is within spec. But when they heat up on the highway they get much worse, almost intermittent as OP describes.

 

[The Critic]

Originally Posted By: Tosh
The factory front rotors on my 2001 Acura CL warped around 25k (and warped again in the same mileage when replaced under warranty). And they're not hot spots, as I measured perfect sinusoidal runout of 0.001 inch on both (cold, with a 0.00025 inch indicator), which is within spec. But when they heat up on the highway they get much worse, almost intermittent as OP describes.

Runout isn't the direct cause of pedal pulsation. Pedal pulsation is caused by disc thickness variation.

The original poster should inspect his brake rotors for runout and disc thickness variation and take appropriate action. Sometimes the pulsation problem will only appear when the brakes are worked very hard.

 

[Tosh]

I've read Honda/Acura's TSB "explanation" as well, and it's bee essence (and their 'fix' - resurfacing - only serves to run out the warranty).

I would really like an explanation for how a ventilated disc can develop a variation in thickness in a perfectly sinusoidal pattern. Am I to believe material migrates from thin to thick? Maybe the car sat too long and gravity pulled on it, like what (people believed) happens to window glass after 100 years?

 

[ajchien]

Update:

After retorquing the lug nuts 3 times with minimal changes, I decided to look at everything again. Suspension seemed fine again, but I noticed a bit of rust on the brake pad/mounting bracket junction. Cleaned up the area, but I didnt have any grease on hand, so I lubricated with some 5w20 for the time being. Seems to have solved the vibration issue.

 

[ajchien]

Update:

After retorquing the lug nuts 3 times with minimal changes, I decided to look at everything again. Suspension seemed fine again, but I noticed a bit of rust on the brake pad/mounting bracket junction. Cleaned up the area, but I didnt have any grease on hand, so I lubricated with some 5w20 for the time being. Seems to have solved the vibration issue.