Tyre Pressures...

[MagpieMatt]

Hi

Im having my wheels aligned tomorrow, my coilovers have finally settled so its about time i get them done, but I'm unsure about my tyre pressures. Ive saw some stuff online where people were using 40 odd, that seems alot surely lol.

I run 19" 5 segment alloys with a 255/35/19 tyre, what psi would you recommend i use?



Thanks!

 

[Darren92]

Pressures are listed on a sticker within the drivers door jam for your particular engine and drivetrain.

 

[MagpieMatt]

Pressures are listed on a sticker within the drivers door jam for your particular engine and drivetrain.

I had 18" originally on my car and I've had the 19" recently put on with my coilovers

 

[ruairi83]

I run the same tyres and find 36psi all round to be best

 

[jdp1962]

I've just checked and reset mine today. Same size wheels and tyres, 36 front, 33 rear, just as the data sticker recommends.

 

[V6_Man]

S4 - B8.5 on 255/35/19

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[Dippy]

B8.5 S5 sportback spec is 39/33. Does anyone know why the fronts would need to be higher pressure than the S4 with same tyres?

 

[barkclark]

B8.5 S5 sportback spec is 39/33. Does anyone know why the fronts would need to be higher pressure than the S4 with same tyres?

Im totally guessing here. But as you's have the same weighted engine. Would it be due to weight distribution over the different size / total weights of the cars etc?

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[jdp1962]

B8.5 S5 sportback spec is 39/33. Does anyone know why the fronts would need to be higher pressure than the S4 with same tyres?

Are the rims wider? I know the offset is.

 

[V6_Man]

19s in S5 come with 19x8.5 (offset 32) and 19x9 (offset 33). If it is 19x9 then maybe it is the reason why it is different but then why is rear the same.


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[jdp1962]

19s in S5 come with 19x8.5 (offset 32) and 19x9 (offset 33). If it is 19x9 then maybe it is the reason why it is different but then why is rear the same.


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@Tashfeen, you will have guessed by now that my technical knowledge left the building just before my last post.

 

[Dippy]

Yes that must be it. I have the 19x9 wheels, so I guess if these are a bit wider than the S4 wheels then the tyres would need a bit higher pressure wouldn't they? Maybe due to the overall difference in shape, there is slightly less weight over the rear axle than the S4?

 

[V6_Man]

Yes that must be it. I have the 19x9 wheels, so I guess if these are a bit wider than the S4 wheels then the tyres would need a bit higher pressure wouldn't they? Maybe due to the overall difference in shape, there is slightly less weight over the rear axle than the S4?

@Dippy ; the only explanation I could think of is possibly the weight distribution (front to rear), which we all know by default is 60/40. Overall, S5 (sportback) is slightly heavier and wider than the S4 and therefore slightly heavier nose weight. I believe the higher tyre pressure is to compensate that as well as to avoid any understeer they have gone with a lower tyre pressure at the back. I personally believe the 39/33 (front/rear) tyre pressure makes the overall weight distribution (50/50) and therefore helps avoid over/understeer (let's hope I am correct here )

In terms of the specs, I believe this is how it looks like for S4 V S5:
Height
S4 - 1407mm
S5 - 1382mm
Front/rear Track
S4 - 1552/1539 mm
S5 - 1588/1575 mm
Unladen Weight
S4 - 1705 kg
S5 - 1720 kg