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Tire pressure(s)

3K views 21 replies 10 participants last post by  AndreasPassat 
#1 ·
Why does my 05 1.8T 4motion have diffrent tire pressures front ( 34 ) and rear ( 44 ) ? I had 4 new stock rims put on as 3 were a little out of true ..got it back and a day later check the pressures and were 34 front and 44 rear . Let the air out till an even 32 and say what ever . Car definitely rode worce . I thought to myself that my VW guys are serious profecinals and couldn't see them effing up . Sure enough the door jam sticker verifies the mixed pressures for my tire ??
 
#2 ·
Increasing the rear tire pressure will make the car more "tail happy" -- in other words, when cornering, if your rear tires have higher pressure than the front, the car handles a little bit more balanced (even on 4mo cars because the all wheel drive system is haldex...which means its FWD biased unless it detects slip). There is no rear sway bar on the passat (even on 4mo's), so the way they compensate for that is by increasing the rear tire pressure. It doesn't give the same dramatic effect a sway bar would, but it does help the handling characteristics of the car. By putting equal tire pressures front and rear, you're actually worsening the handling of your car.

When I autocross my car, I put the rear's up to 50 and around hard corners the rear end slides around like it's a miata or an S2000. Definitely not good for daily driving but good for fighting understeer when you're pushing the limits of the car. Especially on such a nose heavy car like VW/Audi's.
 
#4 · (Edited)
(even on 4mo cars because the all wheel drive system is haldex...which means its FWD biased unless it detects slip).
Though a bit of an aside, the information quoted above is incorrect. B5 and B5.5 Passats with 4mo are Torsen systems, not Haldex. This means that the mechanical center diff sends power equally to the front and rear under normal conditions.

Many newer transverse engined chassis use the Haldex electronic 4wd system.

Edit: oops, missed hu vws post saying the same thing.

There is no rear sway bar on the passat (even on 4mo's), so the way they compensate for that is by increasing the rear tire pressure.
This information is also incorrect. The 4mo Passat is equipped with a rear sway bar from the factory.

To say that the fwd does not have one is true, but also a bit misleading. The torsion bar rear suspension essentially acts as a rear sway bar, limiting suspension travel on one side relative to the other as the beam flexes.

As for rear tire pressure, my wagon lists two different numbers. One is for "half load" and the other is for "full load". Obviously you would inflate the rear tires more for a long road trip with a heavily loaded cargo area. I'm not sure if the sedan is similar or not with the smaller cargo capacity.
 
#6 ·
i stopped at a tire place to have them look at a rattle in the rear (loose heat shield) and they adjusted my tire pressure cause they were "way off". all i can say is it corners funny at 35 PSI all the way around. FWD V6 variant. not going back there. i had an idea when nothing was moved around the fuel door release switch. on my 2000 its on the back of the fuel door.:thumbdown

i guess keeping my tires at 32 in the front and 44 in the rear is "way off" from 35 all 'round.
 
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