Another OCD Post On Steering Wheel Vibration

[dal59]

Yes, I know I need help. However, I cannot afford a psychiatrist, so I have to rely on you guys. Anyone that has read my posts knows that I am a nut when it comes to any type of vibration in my steering wheel.
So please be kind with replies.

Okay, this is not a typical vibration from tires, wheels or balance. The tires are brand new Michelin PSAS 4' and balanced great with fantastic Road Force numbers. The car ran perfectly smooth for the last 6 weeks. We have had a very mild winter here, but as soon as the weather cooled a bit (30', 40', 50') I started picking up more road feel. A minor shaking in the steering wheel on some road surfaces. Other surfaces, the car is still smooth.

I am running OE wheels and tires sizes - 275/30/R20 and have never owned a "sports car" with such a short sidewall. Driving in Comfort helps, but does not eliminate, so a couple of questions.

1- Is this just the nature of an aspect ratio of 30 on a tight suspension?
2- Does this happen in cooler weather as a result of the rubber becoming stiffer? Meaning, in the summer it will smooth out again?
3- Has anyone else addressed this issue by changing tire pressures from the recommended 38/32 to something else. And, if so, what numbers have worked for you?

tks, dal

[JohnEnglish]

Cooler weather will make the rubber stiffer. Also, I think the recommended pressure in the manual for the 275/30R20 tires is 36F/33R. Higher pressure will transmit more vibration.

[dal59]

Cooler weather will make the rubber stiffer. Also, I think the recommended pressure in the manual for the 275/30R20 tires is 36F/33R. Higher pressure will transmit more vibration.

I can always count on Mr. English. :)

tks, dal

[Burrcold]

The recommended psi is 38/32.

[thatTARDISguy]

The recommended pressure can be found on the door card, assuming you're still running stock tire size.. which it looks like you are.

Swing by your Costco if you're a member, they should true up your air for free.

[Burrcold]

The recommended pressure can be found on the door card, assuming you're still running stock tire size.. which it looks like you are.

Swing by your Costco if you're a member, they should true up your air for free.

The recommended pressure on the door card is for max load so it should not be followed. The owner's manual has the right pressures (for the 20/275 tires it's 38/32 for normal load).

[JohnEnglish]

The recommended pressure on the door card is for max load so it should not be followed. The owner's manual has the right pressures (for the 20/275 tires it's 38/32 for normal load).Yeah, it's 38F/32R, not sure where I got 36F/33R from.

[dal59]

Yes, I was using 38/32 during the summer with no problems. However, now I seem to have a very slight vibration on certain road surfaces so I was trying to see if a lower pressure during the winter might help out. Once summer comes and the rubber softens up again I would go back to the pressures stated in the owners manual.

[Burrcold]

Yes, I was using 38/32 during the summer with no problems. However, now I seem to have a very slight vibration on certain road surfaces so I was trying to see if a lower pressure during the winter might help out. Once summer comes and the rubber softens up again I would go back to the pressures stated in the owners manual.

I wouldn't do that, you're asking for a bent wheel. If temperatures are dropping beyond proper operating temps, you should be on a different tire not adjusting the pressure to compensate. You live in Atlanta so I can't imagine it's ever cold enough to cause a problem with those tires and the recommended tire pressure (not for long periods of time anyway).

[dal59]

Tire pressure is very important. However, my thread is questioning the nature of the sport suspension, the mannerisms of the car and the low profile tires along with cooler temperatures and the effect that has on all these matters.

The vibration I am referring to is quite minor and I guess most drivers would not even notice it. Very often when I post on this subject a lot of folks respond by saying their car has no vibration in the steering wheel whatsoever. To those I would say, try driving at 80 mph, take your hands off the steering wheel and just rest your fingertips at 10 and 2 and tell me if you feel any vibration.

[dal59]

I wouldn't do that, you're asking for a bent wheel. If temperatures are dropping beyond proper operating temps, you should be on a different tire not adjusting the pressure to compensate. You live in Atlanta so I can't imagine it's ever cold enough to cause a problem with those tires and the recommended tire pressure (not for long periods of time anyway).

Your post is right on the money. Especially since I am now running the Michelin all season tires. If they are designed for light snow and ice they can certainly handle Atlanta temperatures. I am just trying to find a happy balance with maintaining safety but with a slightly softer ride.
And, I could learn to live with it if I knew I was not the only one having this experience. Meaning, if these cars, with these tires just run a little stiffer during the winter, then so be it.

[Yeoman]

I recommend switching to an A8.. an RS car will never be as smooth as you need it to be to address your OCD. Stiffer suspension components (bushings/shocks/engine mounts) and a tire sidewall with little flexibility will of course transmit vibration at a greater level than a luxury cruiser. As already said, you shouldn't be reducing your tire pressure in the winter unless it's temporary to gain additional traction in the snow. Besides, tires naturally lose pressure as temperatures fall, so if anything you should be adding air to support sustained cold periods.

[eightamrock]

Yes, I know I need help. However, I cannot afford a psychiatrist, so I have to rely on you guys. Anyone that has read my posts knows that I am a nut when it comes to any type of vibration in my steering wheel.
So please be kind with replies.

Okay, this is not a typical vibration from tires, wheels or balance. The tires are brand new Michelin PSAS 4' and balanced great with fantastic Road Force numbers. The car ran perfectly smooth for the last 6 weeks. We have had a very mild winter here, but as soon as the weather cooled a bit (30', 40', 50') I started picking up more road feel. A minor shaking in the steering wheel on some road surfaces. Other surfaces, the car is still smooth.

I am running OE wheels and tires sizes - 275/30/R20 and have never owned a "sports car" with such a short sidewall. Driving in Comfort helps, but does not eliminate, so a couple of questions.

1- Is this just the nature of an aspect ratio of 30 on a tight suspension?
2- Does this happen in cooler weather as a result of the rubber becoming stiffer? Meaning, in the summer it will smooth out again?
3- Has anyone else addressed this issue by changing tire pressures from the recommended 38/32 to something else. And, if so, what numbers have worked for you?

tks, dal

FWIW, I am ready to throw my AS3+'s in the trash. They are noisy and prone to vibration issues. I cant stand them. Im not really sure they fixed this problem with the AS4's

[JohnEnglish]

To those I would say, try driving at 80 mph, take your hands off the steering wheel and just rest your fingertips at 10 and 2 and tell me if you feel any vibration.I tried this test this afternoon. On anything other than freshly paved, glass smooth asphalt there was vibration. The amount depended on the road surface condition.


I recommend switching to an A8.. an RS car will never be as smooth as you need it to be to address your OCD. Stiffer suspension components (bushings/shocks/engine mounts) and a tire sidewall with little flexibility will of course transmit vibration at a greater level than a luxury cruiser. Yeah, I think this the issue. I tried driving the same roads in my parents’ Lexus LS460 and there was no vibration present at all; regardless of the road surface condition. If you want a smooth, vibration free ride you’ll need to move towards the luxury side of the equation. Lowering tire pressure really isn’t a good idea.

[dal59]

[QUOTE=JohnEnglish;14700064]I tried this test this afternoon. On anything other than freshly paved, glass smooth asphalt there was vibration. The amount depended on the road surface condition.[QUOTE]


[QUOTE=Yeoman; an RS car will never be as smooth as you need it to be to address your OCD. Stiffer suspension components (bushings/shocks/engine mounts) and a tire sidewall with little flexibility will of course transmit vibration at a greater level[QUOTE]

Ah, okay, believe it or not, this helps me quite a bit. I can live with minor vibration knowing it is fairly "normal" for these cars to have at least some vibration, especially in colder weather. All the components mentioned by Yeoman are negatively impacted and get even stiffer in cold weather. It is just when I feel I am the only one experiencing it, I feel like I got a lemon, or something is wrong with my car.

Also, I do adjust my air pressure monthly and keep it at 37/33. One less lb. in the front and one additional lb. in the back. I am confident these pressures are not a safety concern. Six lbs. difference between front and back just seems a bit too much, so I cut it down to four.

eightamrock, I feel your pain. Sorry you are dealing with this.

I thank you all for your kindness and consideration. I love this car, I just have to stop doing the fingertip test.

[pwdrskr]

Slightly off topic, I found and use ww.tiresize.com (https://tiresize.com/pressure-calculator/) to calculate pressures for tire sizes other than the OEM ones. I'd always wondered (OK, my OCD would go off) what pressure I should run after upsizing diameter/width with aftermarket wheels/tires.

[ywang98]

I like my tire pressure at 41 all around, and let it go down by itself to about 39 to 40. I am used to much stiffer ride cars. RS5 suspension is like a boat during normal driving.

Wondering why the manual has lower pressure in the back. Doesn't that induce understeer?

[JohnEnglish]

Weight distribution and suspension setup play a role too. Audis are front heavy so they tend to have higher pressures in the front tires.

[IamRacer X]

Being OCD has distinct disadvantages in the car world. I too suffer from this but in a different way. My advise is to realize that people like you and I will never find the perfection we seek. It may exist but cannot be sustained long term. lol

[Yeoman]

Wondering why the manual has lower pressure in the back. Doesn't that induce understeer?

Only 43% of the cars weight is in the rear..

[RS5-TP]

I have some very light vibration with the same tire but on aftermarket wheels (20x10.5") and have learned to deal with it. I have personal use of a Hunter Road Force balancer with great low numbers and still see the water in my water bottle shaking a bit (that is a true OCD way of seeing vibration). BTW, these tires are rockstars in deep snow!

[dal59]

We had temps. near 70* for the last 2 days, and I noticed that my slight vibration is all but gone. I am really hoping some vibration is temp. related due to hardening of the rubber of the tires. I read recently that Max Perf. Summer tires will start to harden at 55* and that All Season tires will start to get harder at 45*. To be clear, I am not stating this is their limits, but merely stating when they start to get harder. If this is true, then obviously if they get harder, they would be more inclined to transfer more road feel, even if "perfectly" balanced. As Yeoman pointed out earlier in this thread, it is not only hardening of tires, but all suspension components that get stiffer in the colder weather. And this was with tire pressures at 38/34.