Vibrations at 80+mph & road force balancing

ex10psi · 09-22-2011, 11:10 AM

i know this topic has been discussed quite a bit on the forums. i've done the searches but still would like ot get feedback from you guys...

my m3 from the factory was smooth as butter all the way to 140 mph (on track), bone stock. then i decided to put wider tires on the car (ZCP wheels) 255 and 275 michelin PS2's. ever since then, the car has a slight shimmy in the steering wheel at 80+mph. i've had at least 6 or 7 different shops try to rebalance the wheels! NO ONE can get it right!! i even got 2 new front tires from michelin thinking the tires were defective, it's still vibrating

and everyone tells me that my road force numbers are fine... in the single digits/low double digit numbers. so these shops refuse to "road force" balance the wheels and they try just spin balancing. of course that doesnt help and the vibration shimmy is still there at 80+. what's weird is that if i have passengers or cargo in the car, the vibration is worse.

my question is... should i demand road force balance even though the machine is saying it's within spec? do our cars need to be road force balanced down to near zero? anyone in the WA state area recommend a very good road force balancing shop who actually knows what they're doing?

thanks for the help!

Sean@PYSpeed.com · 09-22-2011, 11:11 AM

Check the PSI on the tires...

ex10psi · 09-22-2011, 11:15 AM

Quote:

Originally Posted by Sean@PYSpeed.com

Check the PSI on the tires...

yup, did that.... tried several different pressures/combinations.

i should also mention, the wheels are stock zcp and they are not bent. the car has 11k miles on it but the vibrations were happening when the car had 2k miles (thats when i put on the new tires).

Malek@MRF · 09-22-2011, 11:15 AM

Make sure your lug bolts are properly torqued as this makes a huge difference on the M3 because of the rotor hat.

ex10psi · 09-22-2011, 11:17 AM

Quote:

Originally Posted by Malekreza11

Make sure your lug bolts are properly torqued as this makes a huge difference on the M3 because of the rotor hat.

i use a high quality torque wrench at set the lug bolts to 88 ft lbs. so i dont think its the lug bolts. thanks for the idea tho, keep them coming!

SEI · 09-22-2011, 11:22 AM

if you put your stock rims back on do they still vibrate? if they do it could be warped rotors

ex10psi · 09-22-2011, 11:34 AM

Quote:

Originally Posted by SEI

if you put your stock rims back on do they still vibrate? if they do it could be warped rotors

i am still running on the stock rims. the only thing i changed was the tires. unfortunately i dont have the stock tires anymore to put back on. but i did have the 2 front tires replaced under warranty by michelin and even still, the vibration is there.

i honestly feel like the wheel balance is not done properly and shops are telling me that they wont road force it because the road force machine is telling them the numbers are within spec.

my question is... what is within spec for our cars on the road force machine? and can these shops road force anyway and would that help?

elh0102 · 09-22-2011, 12:17 PM

I don’t understand. If the shops are telling you the road force numbers, then they are road force balancing. They either have the equipment or not.

ex10psi · 09-22-2011, 12:30 PM

Quote:

Originally Posted by elh0102

I don’t understand. If the shops are telling you the road force numbers, then they are road force balancing. They either have the equipment or not.

no they are not. they are putting the wheels on the road force balancing machine, spinning the unit, and telling me what the machine displays on the screen. and then telling me that it is "within spec"

if they were really road force balancing, it would involve finding high/low spots on the wheel and tire. marking said spots, partial dismount of the wheel/tire combo, then remounting based on marked location. hunter website goes in to great detail about this procedure.

my question is.... for those of you who do have road force balance experience. even if the machine is telling you that it is within spec, for the M3 (who's sensitive to wheel imbalance) do i need to demand that the road force be done anyway and do better than what is "within spec"? anyone with first hand experience with this? thank you

BimmerRob08 · 09-22-2011, 12:48 PM

Since it's a new car, very low miles and you just changed the tires ONLY. I really doubt it's you're rotors. Mine was super smooth until I put 12mm spacers on at about 19,000 miles with APracing BBK. But that's probebly the spacers of course and soon I'm putting on new wheels (ARC-8, sitting in my garage now).

So with new tires you just put on, I think it's a balance issue. I can't see it being anything else. Have you tried different shops or just one? Did you go to the dealer and have them road force balance & do an alignment? Good luck!

ex10psi · 09-22-2011, 01:32 PM

yes, i've tried about 6 or 7 DIFFERENT shops if you can believe that :O

tried the dealership as well but they tell me the SAME THING: road force is within spec, and they will not road force them. this car has been spin balanced so many times its ridiculous. and along the way have picked up some inevitable nicks and scratches from shops....

i'm actually waitin gto hear back from teh dealership. they say their road force machine is broken but should be operational soon. i am asking them to road force it regardless of "in spec" or not.

this whole ordeal has been a nightmare. why is it so hard for people to balance my wheels/tires? i dont get it.

elh0102 · 09-22-2011, 02:25 PM

Quote:

Originally Posted by ex10psi

no they are not. they are putting the wheels on the road force balancing machine, spinning the unit, and telling me what the machine displays on the screen. and then telling me that it is "within spec"

if they were really road force balancing, it would involve finding high/low spots on the wheel and tire. marking said spots, partial dismount of the wheel/tire combo, then remounting based on marked location. hunter website goes in to great detail about this procedure.

my question is.... for those of you who do have road force balance experience. even if the machine is telling you that it is within spec, for the M3 (who's sensitive to wheel imbalance) do i need to demand that the road force be done anyway and do better than what is "within spec"? anyone with first hand experience with this? thank you

Yes, I’m very familiar with the process. In my experience, if the Hunter machine is indicating single digit road force imbalance, it is damn near perfect, and doing anything further is pointless. In fact, I have found anything much under 20 is fine. But, your vibration occurance with the tire change only is certainly suggestive of a tire problem. I can’t imagine a tire shop refusing to do it. But, given the numbers indicated, you should expect to pay them for the extra time. Just for the heck of it, you might try rotating the wheels front to back, and see if you feel it with the rear wheels/tires up front. Obviously, the car’s handling will be a bit different, so don’t push it. If you feel it with the rears up there, then you will know it’s something else.

ex10psi · 09-22-2011, 02:51 PM

Quote:

Originally Posted by elh0102

Yes, I’m very familiar with the process. In my experience, if the Hunter machine is indicating single digit road force imbalance, it is damn near perfect, and doing anything further is pointless. In fact, I have found anything much under 20 is fine. But, your vibration occurance with the tire change only is certainly suggestive of a tire problem. I can’t imagine a tire shop refusing to do it. But, given the numbers indicated, you should expect to pay them for the extra time. Just for the heck of it, you might try rotating the wheels front to back, and see if you feel it with the rear wheels/tires up front. Obviously, the car’s handling will be a bit different, so don’t push it. If you feel it with the rears up there, then you will know it’s something else.

excellent suggestion... why didnt i think of that, haha. this weekend i'll try rotating front to back and see what happens.

thanks for the input regarding the road force imbalance numbers. sounds like i might not want to road force if the numbers are looking good on the hunter gsp9700 machine, last shop told me it was 8 to 9 lbs of road force.

lm1z · 09-22-2011, 02:57 PM

It seems that our cars are VERY sensitive to tire/wheel changes.
My story is a long one. To keep it simple, my problem went as follows:

Swapped to aftermarket wheels/tires.

1. Shimmy at 60+
2. Turned into shimmy when braking as well.
3. Found slight bends in the front wheels. Had them straightened.
4. Tried a roadforce balance.
5. Swapped front tires.

After swapping my front tires now I have ZERO vibration when driving, but I still have it when braking, although not as bad.

I'm having the shop check my rotors, pads, etc. again to make sure it's not a brake issue, but I'm almost 100% positive it's probably because the wheels aren't hubcentric, which is quite common with wheels (hence the process of balancing wheels and tires).

It's very possible you DO have a bend and you just dont know it.
Ask to go out and watch the wheel rotate on the balancing machine. You can clearly watch the inner/outer of the barrel to see if it's rotating completely flat. Also check the surfaces of the tires. Don't rule out your rear wheels/tires either. You might want to get a used set of rears to throw on and see if that solves your issue.

Trevor .:R · 09-22-2011, 08:16 PM

I had this problem and still do ... it was because my front driver side wheel was bent... so that was my reason if you run spacers id check them aswell!

BimmerRob08 · 09-22-2011, 11:28 PM

Well OP, for just a tire swop, sure is strange that after all those balances it's still got a vibe.

I'm no Automotive engineer but how can this vehicle be that sensitive to just a small tire change in size?

I had to put 12mm spacers to clear my BBK with stock 18" wheels. Then that first drive on the highway at 80+mph I've had the slight wobble ever since. Magnafied under regular DD braking at those speeds but with no brake pedal feedback such as a warped rotor. Now I'm getting ARC-8 wheels installed/road forced balanced & a new alignment. I hope this fixes my wobble problem eitherwise I just spend over $8,000 on a BBK and new wheels for nothing. This is fustrating and I can imagine how fustrating it's been for the Op with just a tire change.

ex10psi · 09-22-2011, 11:41 PM

its been extremely frustrating that's for sure... i'll try rotating the rear tires up front and see what happens. the "bent wheel" theory is interesting also, but if the road force numbers are coming back good, doesnt that mean that the bent wheel is factored for and shouldnt be an issue?

i spoke to the dealer today and he said that as soon as their road force machine is fixed, they will do a road force balance per my request. but if the numbers are coming back good, i dont know if its worth the cost and effort. i may just try it to just exhaust all options.

totally sucks, whats weird is that the vibration gets worse with passengers/cargo in the car, when the car has more weight over the wheels.

Krozi · 09-22-2011, 11:57 PM

Yea this car is just stupid sensitive when it comes to wheels. I put spacers on my stock 18's and got wheel wobble, no bends and perfect road force. When I got VMR's I also had perfect road force read-out and no bends...also had wheel wobble.

Now I am back on OEM 19's and most of it has subsided but I still get it around 80-90. Funny thing is that after 100mph it's smooth like butter.

BimmerRob08 · 09-23-2011, 11:59 AM

Well the increased weight of passengers in the car magnafies the vibe because more down force is added to the wheel naturaly. For example, when I start to brake with my M3 at 80mph (-/+) where I feel the vibration, the vibe in the steering wheel is magnafied because of the force now being applied to the front wheels as the car dives a bit because of braking. Weight has alot to do with how a vibration if felt.

For example in my HH-60G helicopter I fly, usually when it's full of fuel and heavy gross weight, some vibrations are not felt until we burn off most of the fuel and that is because the weight in this case, dampens the vibration. Kinda a different issue of course but sometimes weight can dampen or magnafy the problem. Just depends on the application.

Also as for vibrations smoothing out at higher speeds, is because the frequency of the vibration increases and the "wave" of the frequency dip and high (just like a A/C) current on a scope if you will), the gap shortens with increased speed. At low speeds it's not felt because the frequency gap is so wide. In my car for example, going past 95mph it seems the vibration dissapears, but I start to feel that the car doesn't drive smoothly because there are other indicatiors to feel. If I feel the gear shift for example, the empty passenger seat head guard and the A-piler by my windshield. I feel an increased roughness to it. That was not there when I didn't have the spacers installed. And if I brake at 95+ mph, I can still feel that vibration in the steering wheel because of the load that's put on it, but the frequency of the vibration is now much faster.

So although it seems the vibration dissapears at higher speeds, it's not. It's still there but at a much faster frequency. If you feel around the car at different spots while driving at higher speeds, most likely you'll feel a roughness to it that once was not there. Very difficult to detect but if you know what to look/feel for, you'll spot it.

ex10psi · 09-23-2011, 04:28 PM

Quote:

Originally Posted by BimmerRob08

Well the increased weight of passengers in the car magnafies the vibe because more down force is added to the wheel naturaly. For example, when I start to brake with my M3 at 80mph (-/+) where I feel the vibration, the vibe in the steering wheel is magnafied because of the force now being applied to the front wheels as the car dives a bit because of braking. Weight has alot to do with how a vibration if felt.

For example in my HH-60G helicopter I fly, usually when it's full of fuel and heavy gross weight, some vibrations are not felt until we burn off most of the fuel and that is because the weight in this case, dampens the vibration. Kinda a different issue of course but sometimes weight can dampen or magnafy the problem. Just depends on the application.

Also as for vibrations smoothing out at higher speeds, is because the frequency of the vibration increases and the "wave" of the frequency dip and high (just like a A/C) current on a scope if you will), the gap shortens with increased speed. At low speeds it's not felt because the frequency gap is so wide. In my car for example, going past 95mph it seems the vibration dissapears, but I start to feel that the car doesn't drive smoothly because there are other indicatiors to feel. If I feel the gear shift for example, the empty passenger seat head guard and the A-piler by my windshield. I feel an increased roughness to it. That was not there when I didn't have the spacers installed. And if I brake at 95+ mph, I can still feel that vibration in the steering wheel because of the load that's put on it, but the frequency of the vibration is now much faster.

So although it seems the vibration dissapears at higher speeds, it's not. It's still there but at a much faster frequency. If you feel around the car at different spots while driving at higher speeds, most likely you'll feel a roughness to it that once was not there. Very difficult to detect but if you know what to look/feel for, you'll spot it.

thanks for the explanation, it makes sense. no wonder you are experiencing it at braking too, i do not get it when braking... it is definitely more evident though with more weight in the car.

i also notice the sensation of the vibrations going away at 95-100+ and it make sense that the vibrations are probably still there, just not as noticeable.

i'll try throwing the rear wheels up front hopefully this weekend and see what happens. let me know if you get your vibrations sorted out as well... when i did some searches, i think i ran across one of your posts about vibration issues. not sure if you got that sorted out or what your next steps are, thanks.

BimmerRob08 · 09-24-2011, 01:32 AM

The only way I think to find out what's causing it is by process of illimination. Change the front tires, swop wheels, etc. Of course this is a very expensive and painstaking method. I'm kinda doing the same thing by going with ARC-8 wheels and hoping(praying) that once the wheels are road force balanced and a new alignment will clear up the problem. Sure is a pain in the ass. Maybe just go back to your stock size tires and hopefully that will get rid of the vibes.

To me it's not worth an extra 0.5" of rubber and end up having a anoying vibration at speed. But of course if you've modifed stuff like I did, you can't go back but just try different things.

If you narrow it down and figure it out, let us know man. Very interested in figuring it out.

Emil · 09-24-2011, 04:28 AM

i had a similar problem and could not find a solution. all components were balanced peefectly. no success. i talked to a very experienced bmw engineer and he told me something very surprising:
first of all, the m392 is very sensitive for vibrations. but in my specific case the vibes were caused by aerodynamic effects, not by misbalancing. by mounting spacers (or wider tires as in your case) the air hits a bigger part of the tires outside shoulder. now some shoulder tread profiles tend to drag the air more than others. the ps2 tires seem to be known for building up some kind of resonant peak in specific speed ranges due to a different to stock air stream. maybe that could be the reason in your case too.

09-22-2011, 11:10 AM	#1
ex10psi Private 4 Rep 62 Posts Drives: 2011 E90 M3 Join Date: Feb 2011 Location: WA iTrader: (1)	Vibrations at 80+mph & road force balancing i know this topic has been discussed quite a bit on the forums. i've done the searches but still would like ot get feedback from you guys... my m3 from the factory was smooth as butter all the way to 140 mph (on track), bone stock. then i decided to put wider tires on the car (ZCP wheels) 255 and 275 michelin PS2's. ever since then, the car has a slight shimmy in the steering wheel at 80+mph. i've had at least 6 or 7 different shops try to rebalance the wheels! NO ONE can get it right!! i even got 2 new front tires from michelin thinking the tires were defective, it's still vibrating and everyone tells me that my road force numbers are fine... in the single digits/low double digit numbers. so these shops refuse to "road force" balance the wheels and they try just spin balancing. of course that doesnt help and the vibration shimmy is still there at 80+. what's weird is that if i have passengers or cargo in the car, the vibration is worse. my question is... should i demand road force balance even though the machine is saying it's within spec? do our cars need to be road force balanced down to near zero? anyone in the WA state area recommend a very good road force balancing shop who actually knows what they're doing? thanks for the help! __________________ 2011 E90 M3 2004 996 GT3
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09-22-2011, 11:11 AM	#2
Sean@PYSpeed.com Major General 306 Rep 8,952 Posts Drives: 2009 AW E92 M3 Join Date: Nov 2009 Location: Bay Area iTrader: (22)	Check the PSI on the tires...
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09-22-2011, 11:15 AM	#4
Malek@MRF BimmerPost Supporting Vendor 731 Rep 3,735 Posts Drives: E92 M3, E46 M3, G82 M4 Join Date: Jan 2008 Location: Irvine, California iTrader: (5)	Make sure your lug bolts are properly torqued as this makes a huge difference on the M3 because of the rotor hat. __________________ BMW PERFORMANCE SPECIALISTS. Race Engines. Suspension. F/I. Brakes. Race Preparation. Factory Service. Alignments. OFFICIAL PARTNERS: KW. MOTON. Brembo. AP Racing. BBS Motorsport. iND. HRE. Turner Motorsport. VAC. BMW Motorsport. Facebook \| Instagram \| Yelp! \| Flikr Phone: 949-233-0448 \| E-Mail: info@mrfengineering.com
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09-22-2011, 11:22 AM	#6
SEI Second Lieutenant 47 Rep 283 Posts Drives: M3 Join Date: Jul 2007 Location: Jakarta iTrader: (0) Garage List 2016 Mercedes c63s amg [0.00] 2013 Kawasaki Ninja ... [0.00] 2007 Yamaha R6 [0.00] 2014 Mercedes S500 [0.00] 2011 BMW X3 35i [0.00] 2012 Mercedes E63 AMG [0.00] 2006 Mercedes S500 [0.00] 2007 BMW 335i (E92) [0.00] 2011 BMW M3 [0.00]	if you put your stock rims back on do they still vibrate? if they do it could be warped rotors __________________ now: 2008 335i (E92), 2011 M3 (E92), X3 35i (F25),2012 E63 AMG (W212), 2013 Kawasaki Ninja 250, 2007 Yamaha R6 gone:2009 GTR, 2007 335i (E93) 2004 M3 (HPF stg 3), 2008 Civic Lx, 2007 Z4M Roadster, 2001 Gembala GT550, 2007 CLS 55, 2007 STI, 2004 M3
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09-22-2011, 12:17 PM	#8
elh0102 Captain 15 Rep 751 Posts Drives: 2009 335i coupe Join Date: Apr 2010 Location: USA iTrader: (0)	I don’t understand. If the shops are telling you the road force numbers, then they are road force balancing. They either have the equipment or not.
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09-22-2011, 12:48 PM	#10
BimmerRob08 Major 110 Rep 1,311 Posts Drives: 2008 M3, Space Gray Join Date: Mar 2008 Location: KIKR (ABQ), NM iTrader: (0)	Since it's a new car, very low miles and you just changed the tires ONLY. I really doubt it's you're rotors. Mine was super smooth until I put 12mm spacers on at about 19,000 miles with APracing BBK. But that's probebly the spacers of course and soon I'm putting on new wheels (ARC-8, sitting in my garage now). So with new tires you just put on, I think it's a balance issue. I can't see it being anything else. Have you tried different shops or just one? Did you go to the dealer and have them road force balance & do an alignment? Good luck!
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09-22-2011, 01:32 PM	#11
ex10psi Private 4 Rep 62 Posts Drives: 2011 E90 M3 Join Date: Feb 2011 Location: WA iTrader: (1)	yes, i've tried about 6 or 7 DIFFERENT shops if you can believe that :O tried the dealership as well but they tell me the SAME THING: road force is within spec, and they will not road force them. this car has been spin balanced so many times its ridiculous. and along the way have picked up some inevitable nicks and scratches from shops.... i'm actually waitin gto hear back from teh dealership. they say their road force machine is broken but should be operational soon. i am asking them to road force it regardless of "in spec" or not. this whole ordeal has been a nightmare. why is it so hard for people to balance my wheels/tires? i dont get it. __________________ 2011 E90 M3 2004 996 GT3
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09-22-2011, 02:57 PM	#14
lm1z Major 194 Rep 1,278 Posts Drives: 2017 GT350 Join Date: Aug 2007 Location: Frisco, TX iTrader: (22)	It seems that our cars are VERY sensitive to tire/wheel changes. My story is a long one. To keep it simple, my problem went as follows: Swapped to aftermarket wheels/tires. 1. Shimmy at 60+ 2. Turned into shimmy when braking as well. 3. Found slight bends in the front wheels. Had them straightened. 4. Tried a roadforce balance. 5. Swapped front tires. After swapping my front tires now I have ZERO vibration when driving, but I still have it when braking, although not as bad. I'm having the shop check my rotors, pads, etc. again to make sure it's not a brake issue, but I'm almost 100% positive it's probably because the wheels aren't hubcentric, which is quite common with wheels (hence the process of balancing wheels and tires). It's very possible you DO have a bend and you just dont know it. Ask to go out and watch the wheel rotate on the balancing machine. You can clearly watch the inner/outer of the barrel to see if it's rotating completely flat. Also check the surfaces of the tires. Don't rule out your rear wheels/tires either. You might want to get a used set of rears to throw on and see if that solves your issue. __________________ PAST 2007 Black Sapphire E90 335i, 2010 Jerez Black E92 M3, 2012 Mineral White E92 M3, 2013 Singapore Grey F10 M5, 2016 Azurite Black F80 M3, CURRENT 2017 Oxford White GT350
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09-22-2011, 08:16 PM	#15
Trevor .:R Captain 65 Rep 699 Posts Drives: 13 ZCP DCT Join Date: Jan 2011 Location: Thousand Oaks/Camarillo/Westlake iTrader: (1) Garage List 11 M3 [10.00]	I had this problem and still do ... it was because my front driver side wheel was bent... so that was my reason if you run spacers id check them aswell! __________________ Current: 2013 E92 M3 AW DCT Past: 2011 E90 M3 AW DCT, 2011 E92 M3 MR 6MT, 2008 E92 M3 AW 6MT
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09-22-2011, 11:28 PM	#16
BimmerRob08 Major 110 Rep 1,311 Posts Drives: 2008 M3, Space Gray Join Date: Mar 2008 Location: KIKR (ABQ), NM iTrader: (0)	Well OP, for just a tire swop, sure is strange that after all those balances it's still got a vibe. I'm no Automotive engineer but how can this vehicle be that sensitive to just a small tire change in size? I had to put 12mm spacers to clear my BBK with stock 18" wheels. Then that first drive on the highway at 80+mph I've had the slight wobble ever since. Magnafied under regular DD braking at those speeds but with no brake pedal feedback such as a warped rotor. Now I'm getting ARC-8 wheels installed/road forced balanced & a new alignment. I hope this fixes my wobble problem eitherwise I just spend over $8,000 on a BBK and new wheels for nothing. This is fustrating and I can imagine how fustrating it's been for the Op with just a tire change.
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09-22-2011, 11:41 PM	#17
ex10psi Private 4 Rep 62 Posts Drives: 2011 E90 M3 Join Date: Feb 2011 Location: WA iTrader: (1)	its been extremely frustrating that's for sure... i'll try rotating the rear tires up front and see what happens. the "bent wheel" theory is interesting also, but if the road force numbers are coming back good, doesnt that mean that the bent wheel is factored for and shouldnt be an issue? i spoke to the dealer today and he said that as soon as their road force machine is fixed, they will do a road force balance per my request. but if the numbers are coming back good, i dont know if its worth the cost and effort. i may just try it to just exhaust all options. totally sucks, whats weird is that the vibration gets worse with passengers/cargo in the car, when the car has more weight over the wheels. __________________ 2011 E90 M3 2004 996 GT3
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09-22-2011, 11:57 PM	#18
Krozi Colonel 167 Rep 2,736 Posts Drives: 2008 E92 ///M3 Alpine White Join Date: Oct 2009 Location: SoFla - Bonita Springs iTrader: (24)	Yea this car is just stupid sensitive when it comes to wheels. I put spacers on my stock 18's and got wheel wobble, no bends and perfect road force. When I got VMR's I also had perfect road force read-out and no bends...also had wheel wobble. Now I am back on OEM 19's and most of it has subsided but I still get it around 80-90. Funny thing is that after 100mph it's smooth like butter. __________________ 2008 E92 ///M3 Alpine White//Fox Red//6MT// Florida Bimmer - Join us on FaceBook!
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09-23-2011, 11:59 AM	#19
BimmerRob08 Major 110 Rep 1,311 Posts Drives: 2008 M3, Space Gray Join Date: Mar 2008 Location: KIKR (ABQ), NM iTrader: (0)	Well the increased weight of passengers in the car magnafies the vibe because more down force is added to the wheel naturaly. For example, when I start to brake with my M3 at 80mph (-/+) where I feel the vibration, the vibe in the steering wheel is magnafied because of the force now being applied to the front wheels as the car dives a bit because of braking. Weight has alot to do with how a vibration if felt. For example in my HH-60G helicopter I fly, usually when it's full of fuel and heavy gross weight, some vibrations are not felt until we burn off most of the fuel and that is because the weight in this case, dampens the vibration. Kinda a different issue of course but sometimes weight can dampen or magnafy the problem. Just depends on the application. Also as for vibrations smoothing out at higher speeds, is because the frequency of the vibration increases and the "wave" of the frequency dip and high (just like a A/C) current on a scope if you will), the gap shortens with increased speed. At low speeds it's not felt because the frequency gap is so wide. In my car for example, going past 95mph it seems the vibration dissapears, but I start to feel that the car doesn't drive smoothly because there are other indicatiors to feel. If I feel the gear shift for example, the empty passenger seat head guard and the A-piler by my windshield. I feel an increased roughness to it. That was not there when I didn't have the spacers installed. And if I brake at 95+ mph, I can still feel that vibration in the steering wheel because of the load that's put on it, but the frequency of the vibration is now much faster. So although it seems the vibration dissapears at higher speeds, it's not. It's still there but at a much faster frequency. If you feel around the car at different spots while driving at higher speeds, most likely you'll feel a roughness to it that once was not there. Very difficult to detect but if you know what to look/feel for, you'll spot it. Last edited by BimmerRob08; 09-23-2011 at 12:08 PM..
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09-24-2011, 01:32 AM	#21
BimmerRob08 Major 110 Rep 1,311 Posts Drives: 2008 M3, Space Gray Join Date: Mar 2008 Location: KIKR (ABQ), NM iTrader: (0)	The only way I think to find out what's causing it is by process of illimination. Change the front tires, swop wheels, etc. Of course this is a very expensive and painstaking method. I'm kinda doing the same thing by going with ARC-8 wheels and hoping(praying) that once the wheels are road force balanced and a new alignment will clear up the problem. Sure is a pain in the ass. Maybe just go back to your stock size tires and hopefully that will get rid of the vibes. To me it's not worth an extra 0.5" of rubber and end up having a anoying vibration at speed. But of course if you've modifed stuff like I did, you can't go back but just try different things. If you narrow it down and figure it out, let us know man. Very interested in figuring it out.
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09-24-2011, 04:28 AM	#22
Emil Private 2 Rep 64 Posts Drives: M3 E92 DCT Join Date: Jan 2010 Location: Germany iTrader: (0)	i had a similar problem and could not find a solution. all components were balanced peefectly. no success. i talked to a very experienced bmw engineer and he told me something very surprising: first of all, the m392 is very sensitive for vibrations. but in my specific case the vibes were caused by aerodynamic effects, not by misbalancing. by mounting spacers (or wider tires as in your case) the air hits a bigger part of the tires outside shoulder. now some shoulder tread profiles tend to drag the air more than others. the ps2 tires seem to be known for building up some kind of resonant peak in specific speed ranges due to a different to stock air stream. maybe that could be the reason in your case too.
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