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View Full Version : Rhytmic sound from wheels, what is this?



Scany
09-15-2006, 08:33 AM
This is starting to drive me crazy :mad:

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 :rolleyes: ).

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
09-15-2006, 10:29 AM
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
09-15-2006, 09:28 PM
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
09-15-2006, 10:49 PM
The driveshaft only spins when the rear wheels are rolling.

Scany
09-16-2006, 10:48 AM
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
09-19-2006, 09:39 PM
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
09-20-2006, 04:12 PM
vibration at 70mph... maybe rear tires... possibly driveshaft.
if it growls... it's a wheel bearing.

Scany
09-25-2006, 06:28 PM
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 :confused:

chicane
09-28-2006, 09:10 PM
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 :confused:

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
09-28-2006, 10:27 PM
I see, thanks

chicane
09-29-2006, 10:17 AM
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
09-29-2006, 03:16 PM
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
09-29-2006, 04:11 PM
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
09-29-2006, 04:43 PM
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
09-29-2006, 09:12 PM
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.

ErikT
09-29-2006, 10:33 PM
Yea, I thought the idea of putting any sort of spray on your rotors probably wasn't the best idea. I'm not getting any sort of rattle, just a squeel.

OwnedbyDuncan
09-30-2006, 06:24 AM
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.

Next time you at a drivers school go ask the chief instructor! He just happens to be my mechanic and has been for the last 24 years. He replaced my pads front or rear without turning or replacing the rotors more times then you have posted to this forum!

And again you dont turn BMW rotors

Dave Apker

chicane
09-30-2006, 07:31 AM
Next time you at a drivers school go ask the chief instructor! He just happens to be my mechanic and has been for the last 24 years. He replaced my pads front or rear without turning or replacing the rotors more times then you have posted to this forum!

And again you dont turn BMW rotors


First, you can turn just about any rotors as long as they stay within spec. The reason most people do not these days is that it just isn't economically feasible. When it used to cost $5 to turn your rotors it was worth while. When it started to cost $25 per rotor and the cost of a new rotor is around $30 it just doesn't make sense.

And again your change rotors with pads (then follow a bedding procedure).

Scany
10-11-2006, 03:14 PM
I see that there is a lot of opinion in this area. i can see the sense in putting new pads on when I replace the rotors. But won't pads wear a lot sooner than the rotor? Therefore it's just not practical at all to change rotors when changing pads.

Also interesting that the Bentley manual dooesn't mention to change both or a bedding procedure.

I didn't change both, and never did anything special, like a bedding procedure. The brakes works great except for a minor squeak at low speed braking. but I'm not sure if the old pads will set it's mark on the rotors and therefore I should change them. But if the pad is the softer material, the pad should shape to the rotor. So I don't really see anything wrong with my replacement of rotors without pads and no particular bedding procedure (ofcourse I didnt do heavy braking for 100miles or so)

As for the vibration/sound, still there. I have a strong feeling it's the wheels/tires. Maybe even in the rear, even though it sounds like its coming from the front. When I figure it out i will let you know.

Thanks for all the replies.

mlytle
10-11-2006, 10:03 PM
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.



um, absolutely not. pads and rotors DO NOT need to be replaced at the same time. mechanics who tell you they do are just trying to sell more pads or rotors.

as several others have posted, if you just change one or the other, wet sanding the rotors with 600 grit and brake cleaner will remove the old pad material on the rotors and then just bed in the new pads, or just replace the rotors and bed the old pads to the new rotors.

the only exception to this is if the pads or rotors are worn out or have an abnormal wear pattern on them.

on the original topic...your symptoms do not sound like a brake or driveshaft problem. have your checked the REAR wheel bearings? and how did you check the fronts? suggest you do a search in this forum on "wheel bearings" there was a long thread or two a few months ago specifically on this topic.

marshall
did more brake work at road atlanta last weekend than most folks do in a lifetime....

mlytle
10-11-2006, 10:11 PM
I see that there is a lot of opinion in this area. i can see the sense in putting new pads on when I replace the rotors. But won't pads wear a lot sooner than the rotor? Therefore it's just not practical at all to change rotors when changing pads.

Also interesting that the Bentley manual dooesn't mention to change both or a bedding procedure.

I didn't change both, and never did anything special, like a bedding procedure. The brakes works great except for a minor squeak at low speed braking. but I'm not sure if the old pads will set it's mark on the rotors and therefore I should change them. But if the pad is the softer material, the pad should shape to the rotor. So I don't really see anything wrong with my replacement of rotors without pads and no particular bedding procedure (ofcourse I didnt do heavy braking for 100miles or so)

As for the vibration/sound, still there. I have a strong feeling it's the wheels/tires. Maybe even in the rear, even though it sounds like its coming from the front. When I figure it out i will let you know.

Thanks for all the replies.


pads don't necessarily wear faster than the rotors. my street 97 m3 has the original pads and rotors on it at 55k miles. i don't exactly baby the brake pedal, but the rotors are almost gone, and the pads are still half there. race car is exactly the opposite...pads gone in a weekend or two, rotors last until they get heat stress cracks in them (3-4 weekends).

there should have been bedding instructions in the box with your new brake pads. it is generally a series of stops from mild to hard in quick succession.

ref my other post for suggestion on the sound.

Scany
10-13-2006, 12:54 PM
pads don't necessarily wear faster than the rotors. my street 97 m3 has the original pads and rotors on it at 55k miles. i don't exactly baby the brake pedal, but the rotors are almost gone, and the pads are still half there. race car is exactly the opposite...pads gone in a weekend or two, rotors last until they get heat stress cracks in them (3-4 weekends).

there should have been bedding instructions in the box with your new brake pads. it is generally a series of stops from mild to hard in quick succession.

ref my other post for suggestion on the sound.

Thank you for your help!

chicane
11-11-2006, 09:25 AM
um, absolutely not. pads and rotors DO NOT need to be replaced at the same time. mechanics who tell you they do are just trying to sell more pads or rotors.

as several others have posted, if you just change one or the other, wet sanding the rotors with 600 grit and brake cleaner will remove the old pad material on the rotors and then just bed in the new pads, or just replace the rotors and bed the old pads to the new rotors.

the only exception to this is if the pads or rotors are worn out or have an abnormal wear pattern on them.


Um, absolutely. Ask any reputable mechanic. Grooves develop on rotors over time (similar to grooves on a record) and these grooves need to be ground down in order for the new pads to bed properly.

Many manufacters recommend that the rotors actually be resurfaced on the car, and dealers and repair shops actually have lathes that are brought to the car and turned on the car itself.

mlytle
11-11-2006, 11:46 AM
Um, absolutely. Ask any reputable mechanic. Grooves develop on rotors over time (similar to grooves on a record) and these grooves need to be ground down in order for the new pads to bed properly.

Many manufacters recommend that the rotors actually be resurfaced on the car, and dealers and repair shops actually have lathes that are brought to the car and turned on the car itself.

see the last para of my post. if there are noticeable grooves in the rotors, that is abnormal wear. grooves do not always develop. it is not a given that turning or replacement is needed when changing pads.

chicane
11-11-2006, 07:15 PM
see the last para of my post. if there are noticeable grooves in the rotors, that is abnormal wear. grooves do not always develop. it is not a given that turning or replacement is needed when changing pads.

That's just not true. Turning or replacement of rotors is a given during any acceptable brake job. Don't believe me go to your local BMW dealer and talk to one of the techs, or go to any reputable brake shop they will tell you the same.

OwnedbyDuncan
11-12-2006, 07:57 AM
That's just not true. Turning or replacement of rotors is a given during any acceptable brake job. Don't believe me go to your local BMW dealer and talk to one of the techs, or go to any reputable brake shop they will tell you the same.

Wrong. Ask NCC's Chief Instructor Bill Shook who also owns his own shop Kraftwagen. Our family has used this shop now for almost 25 years. On my E30 the pads were replaced numerous times in 237,000 without replacing the rotors. He was formerely a a top dealer mechanic. His shop is top rated for quality and service by Washington consumer's Checkbook. Many a time just pads were changed before a drivers school. My brother on his E46 has had pads changed without changing the rotors.

Dave Apker

chicane
11-12-2006, 03:52 PM
Wrong. Ask NCC's Chief Instructor Bill Shook who also owns his own shop Kraftwagen. Our family has used this shop now for almost 25 years. On my E30 the pads were replaced numerous times in 237,000 without replacing the rotors. He was formerely a a top dealer mechanic. His shop is top rated for quality and service by Washington consumer's Checkbook. Many a time just pads were changed before a drivers school. My brother on his E46 has had pads changed without changing the rotors.

Dave Apker

I think I've already discussed this with you so please see post above.

mlytle
11-12-2006, 05:00 PM
That's just not true. Turning or replacement of rotors is a given during any acceptable brake job. Don't believe me go to your local BMW dealer and talk to one of the techs, or go to any reputable brake shop they will tell you the same.

and who stands to make money by turning and replacing rotors all the time? the folks you just said to check with. they are biased.

are you a tech? have you done a lot of brake work?

chicane
11-12-2006, 06:11 PM
and who stands to make money by turning and replacing rotors all the time? the folks you just said to check with. they are biased.

are you a tech? have you done a lot of brake work?


Like I said don't believe me check the following two authoritative sources:
1. Bentley Manual's (The Bible for BMW Automotive repair)
2. BMW OEM Service Manuals (The manufacturer of your vehicle)

See if they don't both recommend either turning of or replacement of rotors when changing pads.


And yes, I have done quite a bit of brake work and I always turn or replace the rotors.

mlytle
11-12-2006, 10:04 PM
Like I said don't believe me check the following two authoritative sources:
1. Bentley Manual's (The Bible for BMW Automotive repair)
2. BMW OEM Service Manuals (The manufacturer of your vehicle)

See if they don't both recommend either turning of or replacement of rotors when changing pads.


And yes, I have done quite a bit of brake work and I always turn or replace the rotors.


they don't. i just randomly pulled one of the bentleys off my shelf, the e46, and there is nowhere in there i could find that says rotors must be turned or replaced when pads are changed.

the bmw oem manual says to replace a lot of things that don't need to be replaced. i wouldn't be surprised if it said rotors. that is more money for their dealers and parts biz, and it covers their butt for liability.

i have done hundreds of brake jobs on bmw's from 2002's to 7 series and have maintained a number of race cars. i never turn bmw rotors, not worth it. if damaged, they get tossed. if good, they get new pads put on. never had any problems, nor do i expect any.

if you like to replace or turn rotors more often than needed, go for it. not required, but doesn't hurt.

chicane
11-12-2006, 11:04 PM
they don't. i just randomly pulled one of the bentleys off my shelf, the e46, and there is nowhere in there i could find that says rotors must be turned or replaced when pads are changed.

the bmw oem manual says to replace a lot of things that don't need to be replaced. i wouldn't be surprised if it said rotors. that is more money for their dealers and parts biz, and it covers their butt for liability.

i have done hundreds of brake jobs on bmw's from 2002's to 7 series and have maintained a number of race cars. i never turn bmw rotors, not worth it. if damaged, they get tossed. if good, they get new pads put on. never had any problems, nor do i expect any.

if you like to replace or turn rotors more often than needed, go for it. not required, but doesn't hurt.


From the 1984-90 (E30) Bentley Service manual
© Bentley Publishers (June 1990)- Page 16 of the "Brakes" section specifically states that the rotors should be resurfaced or replaced when changing pads!

Ouch.

OwnedbyDuncan
11-13-2006, 07:44 AM
An I had an E30 for 16 years. the rotors were only replaced when needed not when the pads were replaced. And when I was running schools I was replacing pads several times a year. I probably had 6 front pad changes on the front rotors and 4 rear pad changes on the rear rotors when I got rid of my E30 and the rotors had approx a 160,000 miles on the car and the car recently had a major service and my mechanic would have advised a rotor change. And since E30 rotors are cheap it wasnt a cost issue.

And dont forget BMW with their OEM rotors recommends against turning the rotors and states you should replace them instead.

And lets see Bentley manual or a BMW mechanic with over 30 years of experience, former BMW dealer mechanic, shop owner, NCC chief Instructor, recognised E30M3 expert and owner of E30325is. And a man I trusted with my life to prep my car and keep it safe for drivers schools. No ouch, bubba. Just face it you are wrong.

Dave Apker and collies

chicane
11-13-2006, 12:55 PM
An I had an E30 for 16 years. the rotors were only replaced when needed not when the pads were replaced. And when I was running schools I was replacing pads several times a year. I probably had 6 front pad changes on the front rotors and 4 rear pad changes on the rear rotors when I got rid of my E30 and the rotors had approx a 160,000 miles on the car and the car recently had a major service and my mechanic would have advised a rotor change. And since E30 rotors are cheap it wasnt a cost issue.

And dont forget BMW with their OEM rotors recommends against turning the rotors and states you should replace them instead.

And lets see Bentley manual or a BMW mechanic with over 30 years of experience, former BMW dealer mechanic, shop owner, NCC chief Instructor, recognised E30M3 expert and owner of E30325is. And a man I trusted with my life to prep my car and keep it safe for drivers schools. No ouch, bubba. Just face it you are wrong.

Dave Apker and collies

While it's admirable that you hold your instructor in such high regard, that doesn't change the facts. The combined experience of the Bentley editorial team (who do nothing but repair BMW's) trumps your one experience from your instructor.

This is not a BMW specific maintenance procedure either. Turning or replacing rotors or drums while replacing pads and shoes, respectively, is a tried and true principle of proper brake maintenance, with decades of proof behind it.

vjmvjmvjm
11-13-2006, 04:28 PM
The authoritative E36 Bentley manual (copyright 1998) (written by the editorial team that apparently trumps everybody else) does not include turning or replacing rotors as a mandatory step in brake maintenance. From pages 340-3 through 340-5 on the topic of "Brake pads, replacing":

10. Thoroughly clean inner and outer surfaces of brake rotor. Inspect rotor for cracks, signs of overheating and scoring.

11. Measure thickness of rotor. See Table b. If rotor does not pass minimum thickness requirements, or is damaged, replace as described later.

Also, page 340-7 includes: CAUTION -- M3 brake rotors must not be machined.

Can't we all just get along?

Next up on Geraldo, how often should I change my oil? Should I take my $80,000 7-series to Wal-Mart for oil changes? Do I need winter tires, or are my excellent driving skills adequate? Can I use synthetic oil in my E30? Are K&N filters any good? What is the best religion? Where do I get my butt dyno calibrated?

Vic

mlytle
11-13-2006, 06:42 PM
Next up on Geraldo, how often should I change my oil? Should I take my $80,000 7-series to Wal-Mart for oil changes? Do I need winter tires, or are my excellent driving skills adequate? Can I use synthetic oil in my E30? Are K&N filters any good? What is the best religion? Where do I get my butt dyno calibrated?

Vic
you win best post of the thread vic!!!!

i am done...if after 4 pages tripower doesn't get it...he won't ever!

OwnedbyDuncan
11-13-2006, 08:39 PM
He is a Pontiac guy and an old one at that. Enough said.

Dave Apker

chicane
11-14-2006, 12:21 PM
you win best post of the thread vic!!!!

i am done...if after 4 pages tripower doesn't get it...he won't ever!

Get what? It's your car and your business how you take care of it, but I certainly am not going to let those comments go unanswered, especially when they are presented as the definitive answer and especially when I can find documentation to back up my point.

Brakes are serious business. People should have all of the facts when doing work like this and then decide for themselves how best to take care of their vehicle.

chicane
11-14-2006, 12:23 PM
He is a Pontiac guy and an old one at that. Enough said.

Dave Apker

Wow. And you gleaned all of that info from...