Tyre Pressures

[Impellor]

Well I have just spent the last two days doing a defensive driving course at the Roadcraft driving centre in Gympie provided at my employers expense. I found this an extremely worth while experience, as now I understand far more about driving techniques, and how tyre pressure improves vehicle handing and braking.

Anyway, to my horror the instructor told me to get the best out of the car I needed to put 48 psi in the fronts, and 44 in the rears. I said "that will surely wear the tires out quicker" his reply was actually this will give them a maximum tyre life. He then informed me that by actually lowering the car and using stiffer springs would also reduce the cars handling capability.

He said that with his rally car he would find the softest standard springs he could find and then use a good quality shock. He then highlighted that he felt that the biggest rim he would use was 17 inch, stating that this was the size as used by V8 Supercars. So now he had my attention, so I asked why.

His reply was that by using a 17 inch wheel and a reasonable profile it allowed for greater vehicle feedback. That by using large wheels and ultra low profiles the driver is never given any warning when the grip level capabilities are achieved, in his words it will just let go. Further he highlighted that under controlled braking tests a VE Late model camira with FE2 suspension, had a greater braking distance than a non FE2 car. His explanation was based on the vehicles inability to transfer 70% of its weight into the front suspension, thus reducing front end grip.Anyway I found that the car was better balanced with the increased pressures.

Also after day one of driving to Gympie hitting the skid pan then driving home, I was averaging 13.7 l/100kms. Today after putting 48/44 psi in the tires I averaged 11.3(and today the car copped a thrashing compared with yesterday). Now if you wish to debate this you are more than welcome to ring Mark at Roadcraft Driver Training you can 0n 54828833.

He also informed me that if you would like to do so skid pan work ring him I he can supply a number for individuals that would like to join in. Just to finish I invited Mark to take my car for a few laps. He was very impressed by the grip and feedback the car had for its size, and also commented on how torquey it was down low.

Bridgestone are a major sponsor and he also stated that they provide extensive information on tyre wear and performance, so he is well worth taking to about tyres and suspension, and how these interact with vehicle dynamics.

Anyway I thought that I would share this will you, as I found it all very suprising, but please understand I don't what to argue, if you have any issues ring the expert because I am not, Cheers

Edited 08/07/11 10:12 AM by RHR
para...WHAT??

[chippa]

Dude have you heard of paragraphs????.... hahaha and 2nd never inflate past your cold max pressure.....

[Impellor]

Right you are . Never inflate over manufacturers maximum pressure.Cheers

Edited 08/07/11 10:12 AM by RHR
No need to quote above post. USE FAST OR ADD REPLY

[xr6greg]

He then informed me that by actually lowering the car and using stiffer springs would also reduce the cars handling capability. He said that with his rally car he would find the softest standard springs he could find and then use a good quality shock.

Yes. But I tend to drive on bitumen roads in a street car which requires stiffer suspension than that of a rally car going sideways around dirt corners over pot holes?

He then highlighted that he felt that the biggest rim he would use was 17 inch, stating that this was the size as used by V8 Supercars.

Does Mark know that V8 supercars are looking at going to 18 inch rims to improve their handling?

Most experienced drivers, and 'experts', will recommend (depends on the brand of tyres of course) that a 40/45 profile tyre should be inflated to about 40/42 psi for street use. The 32/36 psi recommended by the car manufacturer is the best for making the car feel 'smooth' when you are dropping the kids off at school.

[hypnodoc]

32 to 36 is horrible. I run 40 all round and notice a big difference. Don't think I would go over that though, especially for around town driving. Jarred back and extra rattles anyone?

[Barra]

I normally run on between 46-48 psi, inflated when tyres are cold. Max is 50psi on my current tyres. I drive on alot of hwy and rough roads and getting good wear and feedback from the road.

Rattles arent that bad for me..

Edited 16/07/11 04:52 PM by Barra

[Barra]

Impellor, What size and profile tyres are you running.? I use 245/35/19.

[STAINLESS again plz]

When I had 40psi and clutch kicked 3rd at 80kmh the rears would light up violently and the car would shoot across 3 lanes.

Now with 25psi its still violent but stays straight.

The kids feel much safer on the way to school.

Edited 16/07/11 05:57 PM by STAINLESS

[Impellor]

Standard, 17, 235, 40. Cheers

[Impellor]

  On 08/07/2011 at 7:11 AM, xr6greg said:

He then informed me that by actually lowering the car and using stiffer springs would also reduce the cars handling capability. He said that with his rally car he would find the softest standard springs he could find and then use a good quality shock.

Yes. But I tend to drive on bitumen roads in a street car which requires stiffer suspension than that of a rally car going sideways around dirt corners over pot holes?

He then highlighted that he felt that the biggest rim he would use was 17 inch, stating that this was the size as used by V8 Supercars.

Does Mark know that V8 supercars are looking at going to 18 inch rims to improve their handling?

Most experienced drivers, and 'experts', will recommend (depends on the brand of tyres of course) that a 40/45 profile tyre should be inflated to about 40/42 psi for street use. The 32/36 psi recommended by the car manufacturer is the best for making the car feel 'smooth' when you are dropping the kids off at school.

It does appear that V8 supercars may go to 18 inch rims late in 2012. Although from the info I have read its got nothing to do with handling. It is mainly to do with cost saving. That is bigger brakes for reduced brake pad changes, and opens the market up on obtaining cheaper control tyres. One article highlights that they have stuck with the 17's since 1993 because they like them. But as I said in my 1st post give the expert a ring as the number has been supplied. You never know, you might know more than him. Cheers

Edited 16/07/11 06:56 PM by Impellor