Topic: New tire vibrations !!

[rickd]

Last week,I picked up a new ,05 , VW Passat TDI.The dealer had installed MICHELIN tires,knowing I prefer them,MX4 Energy ?

Anyway,they had a vibration that started about 80 k,and almost never went away.The dealer thinking that the tires had "flat spotted" from sitting on another unmoved car for some time,changes rims and tires from another car,which supposedly had not been sitting around.

These tires,CONTINENTAL CONTACTS, have a similar problem,just not as bad.

I had the balance checked at an independant tire shop,and only one wheel was out a miniscule amount.

So,I have a car with about 500 k's,an annoying vibration starting at about 80k,and tires that are balanced.

Is it possible to have a balanced tire that is out of round,or has flat spots

Anyone help

BTW,The recommende tire pressure (16") is 36 fr--44 rear !!!!.  44 -- doesn't that seem like a lot ?

Thanks

[Minou]

Did you experiment with tire pressure?

Why 44 PSI on a rear tires of a FWD car is beyond me.  Unless it is a fully loaded wagon.  You may have confused the label with the figure for a fully loaded car?

I may be flamed for this, but if that car were mine, I wouldn't run more than 35-36 PSI at all corners.

Who knows, it may alleviate your problem and improve your ride at the expense of some high speed handling.

[ovr50]

I think 44 is nuts on any tire on a car. Just my opinion.

[Traum]

A general rule of thumb that I've heard is to divide the vehicle weight (in lbs) by 100, and that's your basic tire pressure. Then depending on the front / rear weight balance, dial in an additional amount of up to 10% to the heavier end. For example, with my 3000lbs FWD vehicle, I'd inflate the front tires to around 33lbs, while the rears take 30lbs.

Of course the rule of thumb is for street driving.

-Rick

[capriracer]

A couple of thoughts:

If the dealer replaced the tires and the vibration only got better, then I would suspect that the major part of the vibration has nothing to do with the tires, perhaps brake rotors, or CV joints.  I've seen a case where the vibration was in the engine and a power steering hose was rubbing against the steering column causing a vubration that felt exactly like a wheel end vibration.  I'd go back to the dealer and tell him that changing tires didn't work and he should try changing something else.

Inflation pressure:  While 44 psi sounds high, I would be very, very reluctant to ignore the vehicle manufacturer's recommendation.  The inflation pressure is what determines the load carrying capacity of the tire.  Overloaded tire failures can be pretty ugly.

Hope this helps.

[avtoller]

A general rule of thumb that I've heard is to divide the vehicle weight (in lbs) by 100, and that's your basic tire pressure. Then depending on the front / rear weight balance, dial in an additional amount of up to 10% to the heavier end. For example, with my 3000lbs FWD vehicle, I'd inflate the front tires to around 33lbs, while the rears take 30lbs.

Of course the rule of thumb is for street driving.

-Rick

I find that "rule of thumb" really odd and ridiculous! An Echo needs about 32 psi, not the 22+ this "rule" would suggest, while an Avalanche would require 58+ psi - a VERY improbable figure to say the least. I don't know where you got it, but it is not a "rule of thumb" I would ever consider using!! 

[rickd]

I went to the dealer to-day,and drove an IDENTICAL car...even the colour.It has about 4000k's,mine has 500,but it was silky smooth.

I checked the demo units tire pressure,and found it was 30 psi..all around !

They didn't know about the 44psi (?),but figured it would rattle your teeth with that high a pressure.

[ovr50]

For tire pressures settings - read the Manual and/or the sticker on the door post - those 2 are correct - everything else, including what the dealer says is BS if it's not the same as those tow.

That's the end of the story.

[morty]

Just because tire and wheel assembly is balanced doesnt mean it is round. You can get any wheel and tire to balance no matter how bad it is bent, but still bent. However, if you have swapped tires and wheels from another vehicle this eliminates this from being the problem. Vibrations sounds like it could be something in the driveline or braking system. Also make sure the wheels are properly bolted on. Check to see that there is nothing on the hub that is interfering with the wheel sitting flush. I would be taking the car back to VW and let them figure it out.

On air pressure....no rule of thumb, read the manual or door jam placard. This is what VW has recommended and is the minimum required to carry the weight of the vehicle.

[rickd]

Morty,with regards to the tires carrying the weight of the vehicle,the sticker says 36 psi for the FRONT-HEAVY end,and 44 psi,for the empty end.

Couldn't this make the back end a little "squirrely" on wet pavement ?

[morty]

If this is what VW has required for the vehicle my recommendation is that is what you need to run. It does seem high, but there must be a reason for it. It may not only be weight requirements..it may be for handling as well. If you lower the pressure in the rear you may begin to experience more understeer. What this means is that with lower pressure in the back the contact patch gets larger and the rear tires have more grip than the front. Perhaps... You could always call VW Canada and ask "How come?"