Tyre pressures

[Kane1234!]

Hi everyone, I have gone for continental sport contact 7s
on 255/30 and 225/35 on my 19s , I have researched quite extensively regarding the pressures needed and cannot get a definitive answer? I have been advised that 40psi front and rear is correct but this doesn’t sit right with me due to the difference tyre sizes, does anyone have the same set up , what do you find works best for everyday commuter drives for comfort and wear? Thanks for any advice appreciate it.

 

[B21]

On my SC7s (and GY5 and MPS4) I use somewhere around the 32/34 mark…maybe 34/36 ..the same tyres on the G29 are in the 30/32 32/34 area

Not mandatory to have same pressures front and rear

40 front under any circumstances is plain dumb..

 

[Kane1234!]

Thanks B21
I will set at 32 front 34 rear straight away, I had a feeling it was wrong they set them as 40psi when fitted, I knew asking here with people with real world experience would get me the correct answer really appreciate it thank you.

 

[B21]

Thanks B21
I will set at 32 front 34 rear straight away, I had a feeling it was wrong they set them as 40psi when fitted, I knew asking here with people with real world experience would get me the correct answer really appreciate it thank you.

Feel free to experiment ..no harm will come provided you don’t drop below 30 psi ish..assuming you’re not running in excess of a sustained 100 mph

 

[Kane1234!]

If I was on a longer journey,and theoretically sitting at a sustained higher speed, what would you suggest then?
Just out of curiosity

 

[B21]

If I was on a longer journey,and theoretically sitting at a sustained higher speed, what would you suggest then?
Just out of curiosity

Tyre pressures should be adjusted upwards for increasing speeds…several vehicles they consider it TFD so they have an over inflated figure for normal speeds and an ok figure ..

If you use my suggested figures then +4 psi for speeds over 100mph sustained

 

[Kane1234!]

Makes sense, Thanks again

 

[Pondy]

Hi everyone, I have gone for continental sport contact 7s
on 255/30 and 225/35 on my 19s , I have researched quite extensively regarding the pressures needed and cannot get a definitive answer?

Those are standard sizes for 19", so why wouldn't you just read the instructions on the inside of the driver's door jamb? :?
I don't quite understand why you would need to do 'extensive research' when the recommended pressures are written on the car.
The make of tyre has nothing to do with the pressures required. The pressures are pertinent to the car, not the tyres.

 

[Nictrix]

If I was on a longer journey,and theoretically sitting at a sustained higher speed, what would you suggest then?
Just out of curiosity

Tyre pressures should be adjusted upwards for increasing speeds…several vehicles they consider it TFD so they have an over inflated figure for normal speeds and an ok figure ..

If you use my suggested figures then +4 psi for speeds over 100mph sustained

I always thought that higher speeds meant you ran with less starting psi as the pressure increased as the tyre got hotter.

 

[Pondy]

I always thought that higher speeds meant you ran with less starting psi as the pressure increased as the tyre got hotter.

Yes it's called the "pressure/ temperature relationship"; Boyles first law of thermodynamics IIRC.

But Peter knows best! :roll:

All these 'discussions' about tyre pressure within 2 or 3 psi is absolute nonsense unless you are using dry N2 in your tyres. It was all the rage about 20 years ago, but people got bored of paying for 'air' so it isn't a thing anymore (unless you are a racing team looking for the ultimate set-up).

 

[Marcoose]

I apply loads of pressure on my tyres.

 

[flybobbie]

Just experiment. On my car with 18 inch GY Asy i have tried everything from 33 to 40.
33 the front is so heavy i can barely turn the wheel.
If i run 36-38 steering easier.
Currently 40 all round but makes the car a bit wobbly on the lumpy daily drive country roads. Was looking today drop to 35 and test drive today.
Never found happy pressure, i think sometimes the wheel widths are too big.
Also you need to have driven at least half an hour for tyres to warm up to asses.

 

[Phoenixboy]

Just experiment. On my car with 18 inch GY Asy i have tried everything from 33 to 40.
33 the front is so heavy i can barely turn the wheel.
If i run 36-38 steering easier.
Currently 40 all round but makes the car a bit wobbly on the lumpy daily drive country roads. Was looking today drop to 35 and test drive today.
Never found happy pressure, i think sometimes the wheel widths are too big.
Also you need to have driven at least half an hour for tyres to warm up to asses.

I find the heated seats better to warm up asses

 

[enuff_zed]

If I was on a longer journey,and theoretically sitting at a sustained higher speed, what would you suggest then?
Just out of curiosity

Tyre pressures should be adjusted upwards for increasing speeds…several vehicles they consider it TFD so they have an over inflated figure for normal speeds and an ok figure ..

If you use my suggested figures then +4 psi for speeds over 100mph sustained

I always thought that higher speeds meant you ran with less starting psi as the pressure increased as the tyre got hotter.

Increasing the pressure means less deformation of the tyre at high speeds and therefore less work put into the compound. It is this 'working' of the tyre that generates the heat. The heating of the air inside the tyre then increases the pressure. Hence why sustained high speeds require higher pressures initially, to prevent the tyre heating up too much.

 

[Busterboo]

35iS 18" GY A6 36/44. Sharp for bendy roads and stable for fast ones. Not good for Driving Miss Daisy, though.

 

[Kane1234!]

live and learn
Thanks for all the great advice
Cheers

 

[Kane1234!]

Old dogs new tricks and all that
I was under the impression the pony old “Run flats” would have been a higher PSI , probably why my extensive research hit a brick wall.
Cheers all

 

[Bombur]

Old dogs new tricks and all that
I was under the impression the pony old “Run flats” would have been a higher PSI , probably why my extensive research hit a brick wall.
Cheers all

I actually was checking this last week and realised my tyres were quite low on pressure given the guide.

My E89 has 18's non runflats and from this picture, same as on my car:

My fronts should be 33 psi and rears 40 psi

40 psi seems high?

 

[B21]

It’s pointless looking at the door jamb tyre pressure advice if you are NOT using the OE runflats..

The OE runflats needed very high pressures to support the tyre design which was unique with very thick sidewalls…

You would be much better off looking at the G29 tyre pressure advice as that reflects modern non run flat tyres settings on a very similar size / performance platform..

 

[Bombur]

It’s pointless looking at the door jamb tyre pressure advice if you are NOT using the OE runflats..

The OE runflats needed very high pressures to support the tyre design which was unique with very thick sidewalls…

You would be much better off looking at the G29 tyre pressure advice as that reflects modern non run flat tyres settings on a very similar size / performance platform..

Thank you