Steering vibration while braking

[ToniCipriani]

So I'm having some issues with the steering.

When I brake from from highway speed, steering starts from around 100km/h, slight vibration, then larger vibration at around 60-50km/h, then vibration damps out. Slight pulsation of the brake pedal at around the same speeds, same intensity variation as well, but very slight. It doesn't seem to happen if I'm braking at low speeds, only highway.

I did some basic diagnostics, rotated the tires and checked the tire pressure, doesn't seem to cut it. My rotors and brake pads are pretty new as well, got a new set on all 4 wheels last Summer.

Any ideas what might be wrong? Thanks.

[ocnblu]

Vibration while braking is almost always caused by warped brake rotors, not a steering problem. Warped rotors can result from heat buildup, causing the iron to warp, or from uneven tightening of the wheel lugnuts. Since your rotors are pretty new (and have plenty of iron thickness left), I'd suggest having the rotors "turned" on a brake lathe. This grinds them down to an even, flat surface. Then make sure the lugnuts are tightened evenly with a torque wrench to GM spec.

[ToniCipriani]

But this time it feels different. I've had warped/rusted out rotors in both the 6 and my old Cavalier, both times the brake pedal pulsates like crazy. I'm only feeling a very mild pulse, and mostly in the steering wheel.

So I'm just wondering could this mean something more serious this time...

[SAmadei]

What car is this? Mileage? Details, etc?

In my experience, I agree with Ocnblu, its rotors. And replacement rotors are notorious for being cheap, so I always buy quality ones. In my experience, one thing about warped rotors is that they will vibrate more as they heat up.

[ocnblu]

Toni if it only happens while braking, then it stands to reason it is in the brakes and not the steering.

[ToniCipriani]

What car is this? Mileage? Details, etc?

In my experience, I agree with Ocnblu, its rotors. And replacement rotors are notorious for being cheap, so I always buy quality ones. In my experience, one thing about warped rotors is that they will vibrate more as they heat up.

2006 G6 V6, 41200 kms

[daves87rs]

It sounds like someone did not install the rotors right....

[SAmadei]

2006 G6 V6, 41200 kms

And you're on your second set of rotors? Rotors should last a lot longer than 25K miles (41000kms). I would be afraid that they were damaged before being installed, the lug nuts are seriously overtightened or maybe something is rubbing badly. Or you could be riding the brake. ;-)

I usually get about two brake changes out of rotors... 40K miles on pads, 80K miles on rotors.

[ToniCipriani]

Reason why my rotors got swapped out so quickly was because they rust out so often, the original stock ones that is. I had them machined twice, so the mechanic told me I really shouldn't machine them again.

[SAmadei]

Reason why my rotors got swapped out so quickly was because they rust out so often, the original stock ones that is. I had them machined twice, so the mechanic told me I really shouldn't machine them again.

I'm not so sure that rust is that big of a deal with rotors, except appearance-wise. The bottom line is that rotors (even expensive ones like my cryo-treated Power Slots) rust fast. They heat cycle so much you can't help it.

It's the same with exhaust... you need special coatings otherwise they rust... fast. And generally you don't get these on consumer-grade automobiles.

On rotors, you can't really coat them, otherwise it wears off or affects the cooling process.

It also sounds like they cut the rotors pretty aggressively.

To be honest, I've stopped cutting my rotors, because the results are too thin and warp quickly. Unless the rotors are warped or seriously uneven, which I haven't seen in a while, I just put the new pads without doing anything to the rotors. On that, I'm still getting satisfactory braking performance, sound, vibration and wear.

I am beginning to think that cutting rotors, while occasionally justified, is generally just something mechanics try to sell us on. Same as wheel alignment. My Bonne has 200K on it, and the alignment is untouched... yet I've gotten incredibly long tire wear. Of course, I don't run over curbs.

Just my 0.02.

[Daryl Z71]

I had a set of slotted rotors from Powerslot on my 05 Silverado that had a white coating on them. They were coated all over except where the pads hit the rotor. It was a nice thing because they never rusted.

[ToniCipriani]

I'm not so sure that rust is that big of a deal with rotors, except appearance-wise. The bottom line is that rotors (even expensive ones like my cryo-treated Power Slots) rust fast. They heat cycle so much you can't help it.

It's the same with exhaust... you need special coatings otherwise they rust... fast. And generally you don't get these on consumer-grade automobiles.

On rotors, you can't really coat them, otherwise it wears off or affects the cooling process.

It also sounds like they cut the rotors pretty aggressively.

To be honest, I've stopped cutting my rotors, because the results are too thin and warp quickly. Unless the rotors are warped or seriously uneven, which I haven't seen in a while, I just put the new pads without doing anything to the rotors. On that, I'm still getting satisfactory braking performance, sound, vibration and wear.

I am beginning to think that cutting rotors, while occasionally justified, is generally just something mechanics try to sell us on. Same as wheel alignment. My Bonne has 200K on it, and the alignment is untouched... yet I've gotten incredibly long tire wear. Of course, I don't run over curbs.

Just my 0.02.

Yeah that was the dealer, actually. They say GM told them to do so under warranty.

The mechanic I have tells me to don't even bother. Same reasoning, they will just warp, because it just means the rotor is off-spec.

But back to my question... other than rotors what else can it be?

Edited May 3, 2009 by ToniCipriani

[PurdueGuy]

Did you do a proper break-in of the brakes? Almost no one does, but it makes a difference.

[ToniCipriani]

Did you do a proper break-in of the brakes? Almost no one does, but it makes a difference.

When I first got it back I did a few harder stops to burn in the pads and rotors, and followed Hawk's instructions.

[PurdueGuy]

When I first got it back I did a few harder stops to burn in the pads and rotors, and followed Hawk's instructions.

good to hear, odd that you're having issues so early. I'm not getting anything like that from my hawks from about a year ago.

[CMG]

There is a big difference in some of the low cost replacement rotors and some of the higher priced good quality rotors sometimes. Beware the inexpensive rotors with the attractive pricetag!

I find on some vehicles even one very hard stop from three digit speeds can bring a rotor to pulsate.

I assume the rotors in question are vented and not solid?

[CMG]

But back to my question... other than rotors what else can it be?

Maybe worn suspension components, or wheel bearings, but it sure sounds like warped rotors..?

[Intrepidation]

Sounds like warped rotors.

[ToniCipriani]

She's in the shop right now, so will see how that turns out. I personally agree with everyone, it's the rotors warping, but it was the shop owner saying it wasn't, but the mechanic agrees with me though.

Thanks guys.

[ToniCipriani]

OK, so the shop got back to me, checked my rotors, there is some slight imbalance in the rotors, but it's not the cause. They suspected the intermediate U-shaft, and asked me to send back to the dealer.

Now since I have sent the car back for the bulletins saying this was a problem, is there a slim chance I can get them fixed under "warranty", even though I don't have any left? They already fore-warned me that if I don't fix this under warranty I can look at several hundred, parts alone.

[ToniCipriani]

Went back to the dealership since they fixed my steering in the past, turns out it's a bad steering column. It was replaced under goodwill warranty and everything's all good.

Thanks to everyone who helped.

[pow]

Glad to hear it's been fixed. Edmunds had the steering column on their long-term AURA replaced as well.