Goodyear Eagle F1's

[Adam230K]

So you suggest i follow whats on the inside of my fuel filler cap exactly? 36psi on fronts, and 41psi on rears?

 

[Will]

It'd be a better starting point, normally I find it's best to start with the manufacturer's settings and tweak slighty according to usage and tyre wear characteristics.

30psi is too low on the rear for sure, I doubt the centre of
the tyre has adequate pressure on it - hence it's been running on the shoulders.

Will

 

[Shude]

Even though my car only really has me in it I run the tyres at the loaded pressures on the fuel cap. If nothing else I might get a slightly better MPG out of it.

 

[Adam230K]

I will give it a try for sure... but my only arguement for not following the manufacturer suggestions is because i'm running 18" alloys with low profile tyres, whereas i'm sure those manfuacturer psi suggestions were for the 15" alloys it had originally? or am i thinking about this incorrectly?

 

[timskemp]

I will give it a try for sure... but my only arguement for not following the manufacturer suggestions is because i'm running 18" alloys with low profile tyres, whereas i'm sure those manfuacturer psi suggestions were for the 15" alloys it had originally? or am i thinking about this incorrectly?

As I understand it regardless of the size of tyres the pressures are minimally altered. The pressure of air is there to support the weight of the car.

 

[prc]

As I understand it regardless of the size of tyres the pressures are minimally altered. The pressure of air is there to support the weight of the car.

I was under the impression lower profile would always run higher pressures.

 

[wemorgan]

There's some interesting information on tyre size and pressure here:

Car Bibles : The Wheel and Tyre Bible Page 2 of 2

 

[Bobby Dazzler]

I was under the impression lower profile would always run higher pressures.

Given that the manufacturer's suggested tyre pressures are just that - a suggested range given a number of different factors - they're the starting point for working out the right pressure for your car.

If you change to a wheel with a bigger diameter than the the biggest fitted on that car from that factory in that model year, then I would say it's likely that you may need to think about increasing it a little and monitor wear, then adjust as necessary.

Only yesterday I was looking at my Father-in-Law's Range Rover. Supplied with 16-inch wheel, biggest factory option 18-inch, and fitted with 20-inch. Using the pressures quoted in the handbook they appear to be wearing more quickly on the shoulders, which suggests that a higher pressure is required.

 

[Mactech]

Given that the manufacturer's suggested tyre pressures are just that - a suggested range given a number of different factors - they're the starting point for working out the right pressure for your car.
QUOTE]

Correct! There is no one right answer and it would be great if there was system like Airmatic for tyres which would vary the pressure for different situations.
If you have more load you need more pressure. If the tyres get warm you need less. For ecomomy you need more. For outright grip you often need less. For ride comfort less is more. Longevity will mean triming the tyre pressures to suit the conditions.
So what is important to you today?

Mercedes car generally run higher pressures for larger diameter wheels. My S class recomends + 3 psi when you move from 18 or 19" wheels to 20"
So I've gone and put 21" on!

 

[hygt2]

Thats almost in van territory the pressures i mean

Whats the max pressure printed on your tyre sidewall?



Lynall

Maximum pressure on the tyre wall states 55 psi which makes sense because it is extra load rated. Each tyre should take over 800kg on maximum pressure.

The standard pressure on the fuel filler flap states for front/rear are 29/32 for light load and normal speed, 32/36 for extra load normal speed and 35/39 for extra load and high speed (over 110mph I think). If tyre is hot then add another 4 psi.