Perfect tyre pressure for dry & wet conditions

[Hayeso]

Hi peeps

 I’ve recently swapped from Bridgestone 225/40/19 S005 to Michelin Sport Pilot 4S to see if I prefer it.

I tried the 4S on my previous Superb 4x4 TSI 280, but preferred the stability of the Potenzer S001s although loved them on my wife’s Mini CooperS! 

 

 I’m guessing the brand of the tyre doesn’t matter much with regards to the pressures as the pressure guide, in the fuel filter cap, is generic! 
The issue with the ‘guide’ is it really only covers a fully laden car & economy.

 

My question is, what is the best tyre pressure for the front and the rear in dry conditions for grip and the best tyre pressures for wet conditions for a VRS estate that has one or maybe two occupants?

 

I’m thinking it’s around 42 psi on the front and 44 psi on the rear approximately, but is it recommended to dramatically change them for wet conditions?

 

 

[RADIOTWO]

3 minutes ago, Hayeso said:

Hi peeps

 I’ve recently swapped from Bridgestone 225/40/19 S005 to Michelin Sport Pilot 4S to see if I prefer it.

I tried the 4S on my previous Superb 4x4 TSI 280, but preferred the stability of the Potenzer S001s although loved them on my wife’s Mini CooperS! 

 

 I’m guessing the brand of the tyre doesn’t matter much with regards to the pressures as the pressure guide, in the fuel filter cap, is generic! 
The issue with the ‘guide’ is it really only covers a fully laden car & economy.

 

My question is, what is the best tyre pressure for the front and the rear in dry conditions for grip and the best tyre pressures for wet conditions for a VRS estate that has one or maybe two occupants?

 

I’m thinking it’s around 42 psi on the front and 44 psi on the rear approximately, but is it recommended to dramatically change them for wet conditions?

 

 

You don't need to adjust for wet or dry, as long as they are the correct as per the guide 

[Hayeso]

But the guide is for fully laden (5 people, full boot) or fully laden full economy!

 

 What about having some fun on your own, wanting the best grip?

[Ootohere]

You might very well need to adjust for wet or dry,  cold wet as the net weeks might be. 

 

You are the one driving, easy to go higher with the pressure, reset the TPMS and then see how you like it, stability, traction / grip, feel on the poorest of surfaces more than just the best like the faster roads / corners.

 

The tyre type can make a big difference and the pressures. Trial and error.     Compound, road temp more than the air temp and the road temp can be several degrees lower than the car shows the temperature is.

 

A TPMS that shows the pressure and temperature at each corner can be quite revealing.

As with BMW / MINI for when there are Run Flats fitted.

 

On the Mini Cooper S is can  be very noticeable just a few psi up or down. Especially with the supposed sporty tyres they come on bad are basically ECO in many cases even on the most powerful ones.

[RADIOTWO]

2 hours ago, Hayeso said:

But the guide is for fully laden (5 people, full boot) or fully laden full economy!

 

 What about having some fun on your own, wanting the best grip?

it wont make any difference 

[Ootohere]

It can make all the difference with many different tyres / profiles if the tread / surface meeting the road surface changes as the tyres are inflated more and the laden weight is pretty much as the 'unladen weight' might be,

 

But then many might not notice and difference doing some spirited driving at UK NSL,s,  maybe just a flash of the TC / ASR light & not aware if the ESP has to do it,s thing, 

or the haldex getting to do some work. 

 

[Gerrycan]

On 05/01/2024 at 20:28, Hayeso said:

 

I’m thinking it’s around 42 psi on the front and 44 psi on the rear approximately, but is it recommended to dramatically change them for wet conditions?

 

I agree with @RADIOTWO that the right pressures are appropriate for both dry and the wet conditions. I've never read anything to suggest otherwise.

I was a bit intrigued by the figures you gave though, which I think, are for a fully loaded vehicle and  appropriate for over 400kg of people and luggage mostly added over the rear wheels.

 

If you have only two people in the car then surely 44psi on the rear is a lot more than necessary to avoid excessive tyre flexing at higher speeds and potential overheating?

The front pressure seems about right because those tyres are subject to most of the cornering, acceleration and, especially potentially, heavy braking loads.

Consider that full emergency braking is near 1 g so the torsional weight on the front tyres is near 3 tonnes,  pressures need to be high to avoid tyre deformation potentially reducing tyre contact and braking effect.

The rear tyres on a fwd vehicle have a far easier life and so a lower pressure will theoretically enable a little larger and more sustained tyre contact on a bumpy corner.

 

Tyre pressures should be set when the tyres are 'cold' (ie at ambient temperature).

It is probably fair to say there would also be a sort of automatic adjustment of actual tyre pressure on a dry warm day (where the air pressure in the tyre would increase with the internal air temperature from driving ) compared to a colder wet day (where the conditions and cold water would suppress the internal air temperature and pressure).

 

I've got no racing or performance experience but a couple of advanced defensive driving courses I did for work drummed home the importance of correct tyre pressures for safety were about 5 psi over manufacturer's recommendations which were for comfort on the high profile tyres of that period. My 17 inch tyres lowest recommended pressures are 32 psi all round so I run 37 psi which feels about right for me with two people in. I up the pressures as per recommendations if doing long distances with heavy loads.

 

For what it's worth, each of my tyres lose about 1 psi a week, so I top up every couple of weeks or so when I refuel. I like to think I can feel the difference.

Edited 7 January by Gerrycan

[RADIOTWO]

1 hour ago, Gerrycan said:

For what it's worth, each of my tyres lose about 1 psi a week, so I top up every couple of weeks or so when I refuel. I like to think I can feel the difference.

That would worry me a little, when I set my tyres they stay at that pressure for months if not years, although I did have a cat that did 

loose pressure and it was down to corroding rims, so I had the tyres removed, cleaned up and refitted, and never had a problem since.

[Ootohere]

If anyone bothers to look at what so called experts recommend for in the wet or very wet they might recommend increasing tyre pressures to reduce the risk of aqua planing.  Others will suggest reducing the pressure to have more tread on the roads. Well that might be again about tyre type and profiles.   It is amazing how location location location and temperatures can be what matters.  Under inflated tyres might well get to hot.  If it is crap ECo bias tyres which have poor grip / traction in the first place in the wet I would not want to put the pressure up more than they are normally run at. 

[Mrjohn1989]

@Hayeso

Hello, not sure how much this will help you, but here's a photo of tyre pressures in BAR.
The car does not have DCC, so I'm curios if that will influence the recommended tyre pressure( if anyone of you has a photo from a car with DCC that would be an interesting comparison).
 

 

[Gerrycan]

19 hours ago, RADIOTWO said:

That would worry me a little, when I set my tyres they stay at that pressure for months if not years, although I did have a cat that did 

loose pressure and it was down to corroding rims, so I had the tyres removed, cleaned up and refitted, and never had a problem since.

Interesting, I don't think I have ever had tyres that retained pressure for that long.

Glad your cat got better  

[Paws4Thot]

On 05/01/2024 at 10:12, Hayeso said:

But the guide is for fully laden (5 people, full boot) or fully laden full economy!

 

 What about having some fun on your own, wanting the best grip?

 

6 hours ago, Mrjohn1989 said:

@Hayeso

Hello, not sure how much this will help you, but here's a photo of tyre pressures in BAR.
The car does not have DCC, so I'm curios if that will influence the recommended tyre pressure( if anyone of you has a photo from a car with DCC that would be an interesting comparison).
 

 

The left hand columns are for up to 3 occupants (plus luggage); the right hand columns are the only ones that apply to "full load".

[RADIOTWO]

8 hours ago, Gerrycan said:

Interesting, I don't think I have ever had tyres that retained pressure for that long.

Glad your cat got better  

oops got a fat finger

If the tyres good I would certainly take to a tyre place and have them removed and the rims cleaned and refitted  

[TheUltraRunner]

I have a TSI RS with DCC.