[poldim]

So I got in my car yesterday and it started vibrating when I accelerated above ~15 mph. I noticed the worst to be around 45 mph or so. Mainly coming from front passenger side and a little from the front drivers side. When I brake firmly the vibration fades at any speed, making me think this is the rotors. If it's not the rotors, I dont know what else it could be.

On that note, I have to figure out how to resolve the problem. Is there a way of deffinetively checking that the rotors are infact damaged without taking them off?

If they are deformed and causing the vibration as they come in and out of contact with the brake pads, are resurfacing and replacing the only two options?

[KL2DC]

are you sure it wasn't your wheels/tires?

[shragon]

i would think rotors if the vibration was happening when braking.

i agree with KL2DC, sounds like you have a tire/wheel problem or possibly something wrong with the suspension. try having the wheel/tires balanced first. also check your lug bolts to make sure they're tight.

side note... for rotors, on bmw's, they replace them, no resurfacing.

[shadowcoder]

Given that this happens on acceleration it's either bent rims or your suspension.
To check your rims, see if you can pay a couple of bucks to your local gas
station that does oil changes so that they can put the car up and check your
wheels by spinning them and see if the rims deform in any way inside our out
as they spin. If they do, you know where your damage is. If not, a quick visit
to the dealer to check the suspension, may be in order.

[HRC]

Shragon is right about replacement of rotors. Just a side note on resurfacing rotors...Metal has "memory" so even if you resurface a rotor, eventually the rotor will re-warp.

Danny

[PMP]

I've always wondered about that "metal memory" thing -- why doesn't the rotor re-warp back to the original "un-warped" shape after it is bent? It seems like the memory only works when it makes it worse for the car - never the other way around.

Definately a head scratcher. Works on shirts, as well. Try ironing a crease in the wrong place on your dress shirt and then try to press it out. Ain't happening. But, the original screw up results in a perfect, wrong, crease in the wrong spot 100% of the time.

Weird.

[KL2DC]

Dip the rotors repeatedly in booze...that'll take care of the 'memory' ...

[poldim]

Originally Posted by KL2DC

Dip the rotors repeatedly in booze...that'll take care of the 'memory' ...

hahahaaha

[poldim]

Originally Posted by KL2DC

are you sure it wasn't your wheels/tires?

I drove the car home a week or so ago, parked it, and left. On the way home I did some hard breaking. Everything was fine with no problems.

Got in it yesterday and vibration is there.

[poldim]

Originally Posted by shragon

i would think rotors if the vibration was happening when braking.

i agree with KL2DC, sounds like you have a tire/wheel problem or possibly something wrong with the suspension. try having the wheel/tires balanced first. also check your lug bolts to make sure they're tight.

side note... for rotors, on bmw's, they replace them, no resurfacing.

I through that since the vibration goes away when I brake firmly, the pads are gripping the rotors and preventing the vibration of in and out of brake pad contact occuring.

[poldim]

Originally Posted by shadowcoder

Given that this happens on acceleration it's either bent rims or your suspension.
To check your rims, see if you can pay a couple of bucks to your local gas
station that does oil changes so that they can put the car up and check your
wheels by spinning them and see if the rims deform in any way inside our out
as they spin. If they do, you know where your damage is. If not, a quick visit
to the dealer to check the suspension, may be in order.

It happens during acceleration, cruise, and decelleration. I doubt its the suspension as the car was not hit, damaged, or stressed in any suspension type way.

[therealm3]

Originally Posted by poldim

I through that since the vibration goes away when I brake firmly, the pads are gripping the rotors and preventing the vibration of in and out of brake pad contact occuring.

As others mentioned, vibration from warped rotors is usually prevalent while breaking. You mentioned that the car sat for a week? You could have some slight temporary flat spots in the tires from sitting too long. This happens on my M3 all the time as it is not a daily driver. About 20 min on the freeway gets enough heat in the tires to get things back to normal.

[poldim]

Originally Posted by HRC

Shragon is right about replacement of rotors. Just a side note on resurfacing rotors...Metal has "memory" so even if you resurface a rotor, eventually the rotor will re-warp.

Danny

Metal memory can be applied to certain metals, but I dont think brake rotor metal is one of those. Rotors have been resurfaced for ages without them "remembering" their warpped shape.

BMW probably replaces them because its easier, quicker, and more money for them.

[poldim]

Originally Posted by therealm3

As others mentioned, vibration from warped rotors is usually prevalent while breaking. You mentioned that the car sat for a week? You could have some slight temporary flat spots in the tires from sitting too long. This happens on my M3 all the time as it is not a daily driver. About 20 min on the freeway gets enough heat in the tires to get things back to normal.

I thought that the runflats were the original culprit too. But I drove it about 16 miles total, 8 miles each way, about 12 miles of it was at 70 mph speed.

[therealm3]

Originally Posted by poldim

BMW probably replaces them because its easier, quicker, and more money for them.

No, they use rotors that have less metal for less sprung mass on the suspension, therefore when they wear down a bit, they are usually past minimum thickness and should be replaced and not resurfaced.

One of the prices we pay for better overall performance.

[therealm3]

Originally Posted by poldim

I thought that the runflats were the original culprit too. But I drove it about 16 miles total, 8 miles each way, about 12 miles of it was at 70 mph speed.

well, try a bit longer and if its still there, then look to the suspension.

[SignHere]

If it happens on acceleration you virtually rule out rotors.

Start with tires, then rims. I'll bet you don't have to go much farther.

[HRC]

Originally Posted by poldim

Metal memory can be applied to certain metals, but I dont think brake rotor metal is one of those. Rotors have been resurfaced for ages without them "remembering" their warpped shape...

Trying to help, but if you know more than me, then so be it. I know for a fact what I say is true...but I must be in a different world, that explains it.

Danny

[poldim]

Originally Posted by HRC

Trying to help, but if you know more than me, then so be it. I know for a fact what I say is true...but I must be in a different world, that explains it.

Danny

Never said you were wrong and I was know it all and was right. Just stated what I thought / remembered from my mse course.

[Jaws]

Check to make sure that you haven't lost a wheel weight.

[poldim]

Originally Posted by therealm3

No, they use rotors that have less metal for less sprung mass on the suspension, therefore when they wear down a bit, they are usually past minimum thickness and should be replaced and not resurfaced.

One of the prices we pay for better overall performance.

If it the rotors, anyone think that bmw will cover this according to their maintenance thing (http://www.bmwusa.com/owners/bmwulti.../maintenance)?

[poldim]

Originally Posted by Jaws

Check to make sure that you haven't lost a wheel weight.

oh, good idea...