Warped Rotors And/Or....?

[Dalmus]

Hello again,

Let's start with the (hopefully) easy one: When braking at slow speeds I feel a gentle pulse in the pedal... When braking at high speeds, I get a washboard effect through the pedal, and actually feel it in the seat, too, but not very much in the steering wheel. Am I correct in thinking that this is primarily a symptom of warped rotors (probably the rear)?

Now, tot he "And/Or?" part of the post... Can warped rotors cause a vibration while driving (but not breaking)? If not then I have something else going on.

Symptom: I get a weak pulsating feeling that I can feel through the wheel and through the seat while cruising down a road (not braking). Its only slightly noticeable from 0-40, but between 40 and 55, it gets to the point where I have an almost washboard effect. From 55-65, it settles down to a "slight" vibration, and then from 65-75 (don't normally cruise any faster!), it gets more pronounced again.

I thought that perhaps it was a bad tire, but after rotating the tires this weekend, I didn't notice any difference at all in the vibration effect... but I did notice that the front tires were worn unevenly, with the outside being significantly more worn than the rest of the tire... Giving me the impression that the tires are sitting in a \ / shape.

Here's a picture:

I don't want to throw an alignment at the front end automatically, and I don't want to replace rotors willy nilly if there is likely to be something else causing these problems...

What are some other possibilities?

Thanks,

 

[swetrid]

I would say rotor problem.

 

[Mustangman66]

i had the same problem on a 2003 xlt, new brakes, no change, new rotors, no change, then before i ended up figuring out what the problem was, i crashed it, so in my opinion, the best way to fix it is just to crash the thing... lol,

but seriously, its either the rotors, an alignment, or bad wheel balancing (look at your wheel weights, and see if they might have moved a little bit...

 

[Dalmus]

Thanks for the replies...

I took another look, and noticed that one of the wheels (what was the right front tire before the rotation) actually has no weight at all on it... I should have noticed that straight off!

Okay, so that may account for the vibration at speed... Rotors probably need to be replaced since I feel pulsing in the brakes, correct?

Since both front tires show the same wear problem, how likely is it that its just an alignment? Could it be a symptom of the springs getting weak? Or did the Wisconsin winter (potholes) just happen to screw up the front end more or less equally?

 

[Limited02]

If the rotors are warped, you should feel the steering wheel shake. You'll actually be able to let go of the steering, apply the brakes and watch it move back and forth.

If the steeing wheel doesn't shake, then it would likely mean the rears are warped. Either way, if the brakes are in need of being changed, I'd get new rotors and pads and be done with it. Get the tires balanced and get it aligned too

 

[Mustangman66]

Do you do any wheeling or have you hit any unusually large curbs lately?

 

[Dalmus]

If the rotors are warped, you should feel the steering wheel shake. You'll actually be able to let go of the steering, apply the brakes and watch it move back and forth.

If the steeing wheel doesn't shake, then it would likely mean the rears are warped. Either way, if the brakes are in need of being changed, I'd get new rotors and pads and be done with it. Get the tires balanced and get it aligned too

Sad part is, the front brakes were done last year, and the rears were done just two months ago... the vibration has been there a long time though, so I guess its possible the guy that did the front over tightened the lugs and warped the rotors...

I guess I can throw on a new pair of rotors for $100 and see if that alleviates the washboard effect.

Sheesh, between that, an alighment, a balance, and the stupid leaking rear pinion seal, I'm going to be nibbled to death in the wallet!

 

[Dalmus]

Do you do any wheeling or have you hit any unusually large curbs lately?

I don't do anything intentional... occasionally I go off-road as a necessity up north, but its soft/sandy trails, and I don't recall running over any large rocks.

I do think that perhaps it might be the poor plowing over the winter... Many of the roads around here actually DO feel like washboards for several days after a snow, combine that with potholes, and maybe my baby's been hurt more than I thought by the roads...

 

[Limited02]

You couldn't tighten the lug nuts enough to warp the rotors. Now if the tire wasn't mounted properly and cause a vibration, you could eventually warp the rotors over time.

I'd first get the tires balanced and have them check to see if it even needs to be aligned. Drive it and see how it feels and report back.

I know exactly what you mean about needing to fix a few things here and there as I've got a few things to do on my list as well

 

[Dalmus]

I took the truck in to get her wheels balanced... After talking to the service manager, he wasn't too confident that was the problem, so he dug a little deeper.

Bottom line:
The two front wheels WERE out of balance (.75 and 1.0).
At speed (45ish and up), the drive shaft is moving slightly in and out of the rear differential - He thinks its the pinion bearing...which the tire shop doesn't do.
There is some (not much) "noise" coming from the front transfer case and the rear diff.

The rods, u-joints and springs and the rest of the suspension looks fine, and no obvious signs of alignment issues... The tire wear he says is basically from not rotating often enough... Which I can't argue with.

The vibration is just as bad post balancing, so I don't see any reason to discount the pinion bearing theory...

Thoughts?

 

[jrford]

"0-40, but between 40 and 55, it gets to the point where I have an almost washboard effect. From 55-65, it settles down to a "slight" vibration, and then from 65-75"

Couple of things come to mind:
Yes driveline can cause this too. My Old heep with 130k, had a similar vibration for 60k, then it broke big time and got stuck in part-time. Anyways it need to be rebuilt, after which the vib where gone.

Another idea, going on with the Ex, similar but not exactly, shocks (or struts if you will) are getting really worn out. for me the vib changes with the road type more than anything else. Same spot on the freeway, about 80mph, washboard effect. Now drive up another freeway and its smooth.

New tires, new brakes, etc, . . .Another thing is these rims seem to throw weights rather easy. Rotors seem to warp if not torqued down evenly. In fact i double check the shops every time. Example, my most trusted shop, guy must have had a phone call, 4 at 100lbs while the 5th lug nut was 200lbs (this will cause them to warp for sure if i continued driving it that way).

 

[Dalmus]

Update:

I took the truck into my mechanic friend's shop... told him what the tire shop said... and of course, the truck wouldn't shudder when he test drove it. He played with the driveshaft, but couldn't see any inappropriate movement.

No matter what, I need both pinion seals replaced, which he'll do for $200 (total). I'll probably do that later this week... He's slightly concerned that they both failed right around the same time, and that does lend some weight to movement of the driveshaft, but again, he couldn't replicate any movement.

So, I'm kind've at an impasse until he can experience the shudder, or I could take it to a tranny shop and pay for an inspection.

 

[Dalmus]

Update:

I took the truck into my mechanic friend's shop... told him what the tire shop said... and of course, the truck wouldn't shudder when he test drove it. He played with the driveshaft, but couldn't see any inappropriate movement.

No matter what, I need both pinion seals replaced, which he'll do for $200 (total). I'll probably do that later this week... He's slightly concerned that they both failed right around the same time, and that does lend some weight to movement of the driveshaft, but again, he couldn't replicate any movement.

So, I'm kind've at an impasse until he can experience the shudder, or I could take it to a tranny shop and pay for an inspection.

One more update... After very careful observation, I've determined that the shudder appears after I've been driving for about 10 minutes. This is the point where I notice the pulsing when I hit the break pedal, as well.

Is it possible that its not a drivetrain issue at all, but the rotors heating up and warping?

 

[Mustangman66]

Doubt full, in my experience once rotors warp, they stay warpef

 

[Dalmus]

Doubt full, in my experience once rotors warp, they stay warpef

That's pretty much what I thought, it was just a shot in the dark.

Then I'm pretty much left with figuring out what would cause a pulsating in the brakes only after I've been driving for 10 minutes or more? And would that same something cause the entire care to shake even while the brakes are not applied?

As a recap... When I start off in the morning, I have no pulsating brakes or shaking car, whether stopping gently or quickly. After I've been driving on the freeway for several minutes, I begin to get the shaking in the car, and pulsating when I apply the brakes. The pulsating in the brakes continues all the way down to a full stop, gentle OR hard.

It implies to me that SOMETHING is expanding not performing properly as it heats up, but if it were something in the drive train, how would that effect the brakes?

 

[2TimingTom]

The thing that comes to mind for me since it happens only after you've been driving for awhile is the pad/rotor combination. Basically brake pads work in one of 2 phases- first in the abrasive phase. When the brakes are cold, the pads are very abrasive against the rotor- scraping off some of the brake pad material left behind from before.. As they warm up, they transfer into the adherent phase. In the adherent phase, the brake pads are actually reacting against a transfer layer of pad material on the rotor surface. In this phase, they will work better than they do in the abrasive phase.

So anyway, my theory is that the transfer layer isn't getting transferred evenly to the rotor- for whatever reason. It doesn't take much of an uneven layer to cause what feels like a major disruption.

 

[Dalmus]

The thing that comes to mind for me since it happens only after you've been driving for awhile is the pad/rotor combination. Basically brake pads work in one of 2 phases- first in the abrasive phase. When the brakes are cold, the pads are very abrasive against the rotor- scraping off some of the brake pad material left behind from before.. As they warm up, they transfer into the adherent phase. In the adherent phase, the brake pads are actually reacting against a transfer layer of pad material on the rotor surface. In this phase, they will work better than they do in the abrasive phase.

So anyway, my theory is that the transfer layer isn't getting transferred evenly to the rotor- for whatever reason. It doesn't take much of an uneven layer to cause what feels like a major disruption.

Interesting theory... For various reasons, I was forced to go with the cheap rotors from Advance Auto when I did the rears. I wonder if I should throw a new set on their for fun and see if that changes anything.

Could this also account for the shuddering while just cruising down the road without applying the brakes, as well?

 

[2TimingTom]

I don't know. My theory is a bit of long shot.

It could be a multitude of things causing your problem.

 

[Dalmus]

Another random thought occurred to me... Is it possible one of the hub assemblies is failing? I don't have any noise that is normally associated with a failing wheel bearing, but if it warms up and then fails, that would explain why the brakes wouldn't reflect that from a cold start...

 

[Baddecision93]

I would be doubtful of a hub assembly. When mine went on my 2000 it howled like crazy, although it did get worse when it warmed up.

Easy enough to check. After it's warmed up jack up the truck and grab the tire by the top and bottom and see if you get any play.