Rhytmic sound from wheels, what is this?

[Scany]

This is starting to drive me crazy

There is a rhytmic sound like "woh woh woh..." that varies with the rotation of the wheels. Sounds to be every rotation of the wheel.

I am pretty sure it is coming from the front. Maybe front right wheel.

Also when I drive over bumps while turning, or when I was braking slightly while hitting a long "hole" in the asphalt, the wheel feels like it's vibrating like gello.

Another symptom is in traffic when I am releasing the brakes I can hear a moaning sound and the steering wheel will shake if I leave the brake slightly touching the rotors. I don't know if this is normal since this is my first automatic car (read: got a girlfriend ).

I don't get alot of vabration at speeds except for at around 70mph the rearview mirror shakes and I can feel it in the car.

At first I thought it was warped brake rotors. They were low anyway, so I changed them all around without much change at all. the old ones don't seem warped. I did not change pads out of budget restrictions and because they were fairly new.

While replacing rotors I checked the front bearings. They don't make any grinding sound or have any play. I also don't have sounds while turning. They don't spin freely, but I guess they shouldn't either. But they also don't seem to spin with much restriction.

I have balanced all wheels and replaced front wheels with spare trying to find the problem without any luck.

I have checked the suspension briefly, and it looks good to me. I also find it hard to believe that suspension failure will cause rythmic sound with the wheel rotation.

It's almost like I have a flatspot on the tire or something. I'd appreciate any ideas on this subject. I so don't wanna change bearings just to find out it's not the cause (even though I should change them sometime soon anyway).

Sorry about the long post

[OwnedbyDuncan]

Driveshaft? Back last summer I thought I had a wheel out of balance or bent. Switched tires around etc. Put the snows on. Had the front wheels balanced. No luck. Had Bill Shook look at and he said driveshaft. Had 220k miles on the car at the time. Put new driveshaft in and problem gone.

Dave Apker

[ErikT]

I have have something somewhat similiar...

If I'm going under 10 mph on a smooth surface it almost feels like one of my wheels is oval, not quite round. The body will actually rock slightly. I really only notice it when I'm stuck in traffic. It feels the same regardless if I'm coasting in neutral or have the clutch engaged.

I'm no expert, but I think the drivesharft would still be spinning even if the car was in neutral. I'm over 200K miles on my E30. know my wheels are true & have new tires. Could that be a driveshaft? I'm pretty sure a driveshaft will still spin if you're in neutral, would be a good explanation?

[Scotty]

The driveshaft only spins when the rear wheels are rolling.

[Scany]

But the sound being equal to the rotations of the wheels would suggest not the driveshaft? Wouldnt the driveshaft rotate faster than the wheels because of the diff gears?

[chicane]

Why did you change the rotors and not the pads? You really need to change these as a set and follow a proper "bedding" procedure. If you have checked everything that you said this could be your culprit.

[jhm5]

vibration at 70mph... maybe rear tires... possibly driveshaft.
if it growls... it's a wheel bearing.

[Scany]

Why did you change the rotors and not the pads? You really need to change these as a set and follow a proper "bedding" procedure. If you have checked everything that you said this could be your culprit.

I don't know what exactly is ment by bedding procedure, and the pads looks very new, and my budget could not fit in pads at the time. Why is it so important to change everything as a set really?

My Bentley manual doesn't mention any of this as far as I've read

[chicane]

I don't know what exactly is ment by bedding procedure, and the pads looks very new, and my budget could not fit in pads at the time. Why is it so important to change everything as a set really?

My Bentley manual doesn't mention any of this as far as I've read

A bedding procedure is basically a mating of the new set of pads with a new set of rotors. Think of it as breaking in a new pair of sneakers.
pads and rotors need to wear together, so if you put on a new set of rotors with a set of pads they were on with you old rotors they have different wear patterns and thus can cause vibration. This vibration is usually more noticeable during braking.

[Scany]

I see, thanks

[chicane]

I see, thanks

You need to replace these items as a set. If you are changing pads you need to replace OR turn the rotors. And if your are replacing or turning rotors you need to replace the pads. And follow a proper bedding procedure. The bedding procedure you can goggle or look up on bimmerforums or unofficialbmw.

Here is one:
http://www.pagidusa.com/bedding_in_procedure.htm

[OwnedbyDuncan]

You dont need to turn or replace the rotors when you replace the pads on a BMW. Many of us do it for schools and or autox's and dont replace the rotors or turn them. BMW rotors should never be turned according to BMW and my mechanic.

I replaced the pads numerous times over 240k without turning or replacing the rotors.

Dave Apker

[ErikT]

When I had my "new" E30 inspected in August it needed new pads to pass. Since I don't have anywhere to work on it (live in an apartment) and I wanted to get it on the road I had them replace the rear pads. Since they wanted another $200 for new rotors I said "no thanks" The manager at Merchant Tire said that my rotors couldn't be turned and that my current rotors are still within spec. Oh yea, I also realized I'm now missing a rattle pin.

With the new rotors my brakes now squeek like crazy once they get warmed up. They said it would stop once they wear in, but it's been about 3K miles already. Had I done it myself I would have put new rotors on. The squealing is starting to drive me nuts so I may actually put on new rotors anyway.

Not to hijack the thread, but I saw a "spray" at pelican parts that is supposed to be an anti-brake squeel spray...Will is find a way to ruin my calipers or anything? I think the route of my noise is due to the fact that the pads make contact with part of the brake disk that wasn't previously "utilized".

[SharkD]

Bedding-in brake pads simply is the act of heating the pad material and taking off the top layer of compound so that the gasses trapped inside during manufacturing will escape while your car is cooling down in your driveway, not when you need the brakes in traffic.

When changing pads, you can lightly scuff the surface of the rotor with sandpaper, but IMHO, it's not necessary. What is necessary, even if you're just swapping between street and track pads and back again is that each time you put a set of brake pads that haven't just come off the car into the calipers, you repeat the bedding process.

As for brake "squeal" most of the time, it's actually the vibration of the pad in the caliper bracket that you're hearing, not the surface of the pad on the rotor. Lots of places sell a paste that you put on the back of the pad to absorb some of the movement. Never coat the face of your pad or rotor with something that claims to reduce noise or squeal (in fact, never put anything on the face of your rotors or pads, unless it's sandpaper, when they're off the car).

[chicane]

You dont need to turn or replace the rotors when you replace the pads on a BMW. Many of us do it for schools and or autox's and dont replace the rotors or turn them. BMW rotors should never be turned according to BMW and my mechanic.

I replaced the pads numerous times over 240k without turning or replacing the rotors.

You need to turn or replace rotors whenever you replace pads. I don't know any reputable mechanic who would tell you otherwise. Driving schools and AutoX, obviously you may not have the time, materials, or tools to change rotors at the track, but for the street the constant vibration would drive anyone nuts, whereas on the track you have so many other vibrations one more probably isn’t going to affect your driving.

Also, if the brake vibration is violent enough it can cause some other serious problems, down the road, with the suspension.