Constant vibration - cannot pin down

[Georgesb2]

Does it do it all of the time on all surfaces? Here is a post I made on the Q50 forum. The never discussed problem.

This is something I discovered 35 years ago. It reared its head again when I had the Hakkapeliitta run-flats on my Q50. And now again with those crappy Michelin MXM4 acoustics (now gone) that came as OEM equipment on my Tesla.

If you've ever watched a crew pave a road with asphalt you will see how it happens. The hot asphalt is dumped into a spreader and then compacted with one of these. A vibrating compactor.

https://www.cat.com/en_US/products/new/equipment/compactors/tandem-vibratory-rollers/1000027463.html

The result is that the surface is not really flat like you get with concrete but contains what I call micro ripples. Depending on the car and tires it will manifest itself with a high frequency, low amplitude vibration felt more in the steering wheel than the car itself. It seems to peak at about 70 MPH. Again, depending on car and tires.

You can confirm this. If you are cruising at highway speeds and feel the vibration but it disappears when you go over an overpass that was paved in concrete there it is. You can also get a visual confirmation. We have a six lane suburban highway nearby that I drive on frequently. The old bypass route before the interstates. It was repaved recently. I noticed it on a day where it had just rained so the road was wet. The sky was overcast and my headlights were on. Those ripples stood out like a sore thumb. Very obvious. Try it yourself.

BTW, on a different note that highway was once lined with the old Nike missile sites. A Cold War relic. The Nike Hercules could carry a nuclear warhead. A surface to air missile. With a nuclear warhead. Sure glad they never used one of those.

The vibration I feel isn't from underneath the road. It's not that type. It's the rough asphalt and you can actually see it coming and predict the noise. It's the tires interfacing with the rough pavement at the surface. The "vibration" isn't periodic at all, it's more constant, like a constant hum, if you will. You might just say it's "road noise". All cars do it, some worse than others. I can hear it when a car or truck drives by and I'm still. That's all on rough asphalt only. That noise penetrates my 22 M3P a lot. It disturbs my head. I took my wife out today and we ran some experiments. Interesting is that when this noise is annoying, there's a sort of beat frequency between the two sides, a pulsating. But if we lower the front windows a bit, the pulsating disappears. She says the source of this road noise into the cabin seems lower doors or possibly floor. I've already sound treated the rest of the car. I haven't done the doors. I would have to guess why lowering the windows gets rid of the pulsating. It could possibly be atmospheric pressure pulses or beat frequency or some of both. I'll just have to treat the doors now and see if it makes any difference or not. One challenge is that this noise records down near 100 hz. I find it's difficult to treat that frequency area. Tire pressure reduction seems to reduce amplitude of the noise. That's why I'm thinking different tires might help. Different shocks might resonate at different frequencies and might dampen these better. Since there's no data available to me, I have to continue to experiment and test.

 

[hari-bhari]

I went to a specialized tire shop and they did a great job - re-indexed all wheels and tires, high speed balanced, and road forced them (which I learned are two different things). I also learned that the lowest to highest road force should go in order from driver front, passenger front, driver rear, passenger rear for the best ride quality. Road force should register < 20lbs for buttery ride (although some cars need <10 which is hard to do). They confirmed the wheels are in round. My road forces are now FL = 6, FR = 9, RL = 19, RR = 26. The road force on the rears is due to some wheel hop and they said I could take it back to discount tire to see if theyll do a replacement. I would say the vibration is 90% gone now, but I'm damn picky so I'm going to finish the job

So lesson is - find a bona fide tire shop and talk to them on the phone and gauge if they know what they are talking about.

 

[XPsionic]

I went to a specialized tire shop and they did a great job - re-indexed all wheels and tires, high speed balanced, and road forced them (which I learned are two different things). I also learned that the lowest to highest road force should go in order from driver front, passenger front, driver rear, passenger rear for the best ride quality. Road force should register < 20lbs for buttery ride (although some cars need <10 which is hard to do). They confirmed the wheels are in round. My road forces are now FL = 6, FR = 9, RL = 19, RR = 26. The road force on the rears is due to some wheel hop and they said I could take it back to discount tire to see if theyll do a replacement. I would say the vibration is 90% gone now, but I'm damn picky so I'm going to finish the job

So lesson is - find a bona fide tire shop and talk to them on the phone and gauge if they know what they are talking about.

Wow, you found yourself an amazing tire shop. Those guys did you right for sure.

 

[Georgesb2]

I've got an '18 LR RWD. Pretty much as soon as I bought it I got 19" turbines from EV Wheel direct. I've had two sets of tires - Bridgestone QuietTrack and Pirelli P7 AS Plus 3 (which are the quietest tires I have ever owned).

However, I have ALWAYS had a mild vibration at highway speeds that I can't get rid of, on both sets of tires. The vibration is mild, but if you look at a water bottle or the wheel you can see a very consistent rhythmic vibration while on a smooth road.

Here is what I have tried and results. I'll focus on the Pirellis since I've had them on for a year. Here is what I have done, in order:

1. Multiple rotate and road force balance - has caused slight worsening or improvements but never eliminated (even on the Bridgestones)
2. Index mount each tire to wheel to minimize deviations - all came within spec, resulted in improvement but not elimination
3. New tire - discount tire was kind enough to replace the tire that was 'furthest' from zero index and did not result in any improvement
4. Testing and straightening all wheels - Finally I decided the wheels must have been out of round from the factory (EVwheeldirect is now OOB but I am sure these are cheap cast alloys). I was actually in there when they did dismounted and tested. Two wheels were 35/1000" out of round, straightened to 20/1000. The remaining two were only 15/1000" out. So all wheels are now 15-20/1000" out of round which is within tolerance even for OEM wheels. This resulted in the most improvement to date, but not elimination.

What else is there to try? Alignment was done at Tesla and is in spec, tires are wearing evenly. No abnormal sounds so I don't think it's a wheel hub. I have noticed mild improvements with all the above things so my feeling is still that it is wheel/tire related but not sure what to do next.

Open to ideas. Thanks in advance.

Years ago I had a Datsun 280Z. I installed aftermarket wheels. The car would vibrate at high speeds. I tried every balance shop, nothing worked. Finally I found a place that had a machine to balance the wheels while on the car. It was a superb balance and it solved the vibration completely! I never had such a smooth ride, all the way to the fastest that car could go. I don't know exactly why this works. I can postulate only. Perhaps one or more wheels were just the slightest off when mounted to the car. I do recall having a difficult time finding places to do this type of balance. I don't know where to find it today either.