Good Street Tyre Pressure

[Sydneykid]

What The! The most miss understood bit of information ever printed is the Tire Recommended Specs.

The manufacture put recommended tyre pressures to have a average Jo Blo sedan have a soft ride.QUOTE]

Simply not the case with performance tyres' date=' Jo Blow doesn't buy them.

The max pressure warning is for the septic tanks (Yanks). Its part of the USA design rules that all tyres in the USA must have a max tyre pressure rating.

I wonder why they have a design rule then?

It has nothing to do what you can actually run the pressures at and what you should run them at.

So the tyre companies are wrong? They don't know their own tyres?

For drags go soft under 30 psi.

Try "under 20 psi".

For good handling, tyre life, economy and less chance of a tyre blow out go for min 38.

Care to explain how 50 psi in your tyres (hot) lowers the "chance of a blow out"?

Go ahead and run at the tyre manufactures spec he and the local tyre shop will appreciate the business in tyre sales.

That's more to do with suspension geometry than tyre presures. "Get a decent wheel alignment" would be a better suggestion to improve tyre life. At 38 psi my Skylines would wear out the middle of the tyres, but they have proper suspension geometry. At 30 to 32 psi they wear nice and even across the tread.

But hey what would I know? I have only been racing and engineering race cars for 25+ years. One of our cars had pole position and 4 race wins out of 4 races last weekend, and it didn't have 38 lbs in its tyres hot, let alone cold.

Sorry if the above is a bit harsh, but something so obviously WRONG has to be killed off pretty heavily.

[xRHETTx]

I was told to run my tyres at 40psi hot by Kevin from Driver Dynamics at his advanced driving course which i attended last year. He said it improved handling (turning) and improved traction and reduced aquaplaning in the wet. So thats what i was basing my opinion on.

My car is stock so traction is not so much of an issue, is there a compromise between handling (turning) and traction when running tyres at say 32psi?

Do the dimensions of the tyre/wheel combination influence the pressure you should run in them? Ive got 17x9s with 235s on them, i guess the pressures i should have for them would be different than say a stock wheel with 205s or whatever?

Rhett

[Duncan]

Gary a couple of points.

Firstly race and r type tyres are a totally different proposition. People using them should be familar with how to set them up, and the correct target temperature for their use. Generally the hot temp for a race tyre is between 30 and 40 but it does vary considerably as I'm sure you know.

Secondly, 40 hot on a road car will only be a couple of psi higher than your recommendation of 32 cold, my guess is in normal driving they would come up to say 36-38 anyway.

I totally agree, if your tyres are wearing in the middle, you are running too high a pressure. In my experience most street skylines wear the inside of the tyre first due to lowering anyway

I have tried road tyres at a wide range of pressures, and 40-42 definately improves the handling. As for the risk of blow outs, I have run those pressures on Falken fk451s at 200klm/h for 2 hours straight when up in the NT with no problems.

[race_snooze]

I run mine at 38 - 40 doesnt matter much to me, 265 40 18

[SLY33]

sorry guys but this is one of the stupidest threads ive read in a while, with everyone giving advice to this guy without even asking what size/type of tyre he is using.

[KRiMiNaL]

i got 17inch wheels. 275 or sumfin

[Sydneykid]

Gary a couple of points.

Firstly race and r type tyres are a totally different proposition.  People using them should be familar with how to set them up, and the correct target temperature for their use.  Generally the hot temp for a race tyre is between 30 and 40 but it does vary considerably as I'm sure you know.

Secondly, 40 hot on a road car will only be a couple of psi higher than your recommendation of 32 cold, my guess is in normal driving they would come up to say 36-38 anyway.

I totally agree, if your tyres are wearing in the middle, you are running too high a pressure.  In my experience most street skylines wear the inside of the tyre first due to lowering anyway

I have tried road tyres at a wide range of pressures, and 40-42 definately improves the handling.  As for the risk of blow outs, I have run those pressures on Falken fk451s at 200klm/h for 2 hours straight when up in the NT with no problems.

Hi Duncan, oh gooooody, a chance for a debate.......

High performance road tyres and "R type" tyres are very close together now in carcas construction and tread pattern. Only the compound is softer and the tread depth less (3 to 4 mm less) this is to keep the skin temperature down, which is caused by tread movement if it is too deep. So any tyre pressure advice more than 3/4 years old, is out of date with the advances in high performacne tyres.

Like many instructors, I tell people to pump up their tyres to 40 psi. But they have just driven there, so that is warm pressure at best. That aside, it's a generalisation, if they have low profile high performance tyres, I wouldn't tell them that. If they said to me "I have these suspension settings" I would also modiify my tyres pressure advice depending on the settings. If it happens to be a suspension set up day, then I would check the tyre temperatures and adjust the pressures to achieve an even temp spread. I have yet to find a road tyre that has even temps at over 40 psi and that's hot pressure (very hot pressure).

I think if you read back over madmuf's post he was suggesting 38 psi cold. That's going to end up a lot more than 40 psi hot. Otherwise you are spot on.

I agree with you on inside tyre wear on lowered Skylines, that's why I posted

That's more to do with suspension geometry than tyre presures.

I have tried road tyres at a wide range of pressures, and 40-42 definately improves the handling.

If that is cold pressure then I would argue strongly that what you are experiencing is "feel", not actual increased grip. If that is hot pressure, then you are probably not far off.

As for the risk of blow outs, I have run those pressures on Falken fk451s at 200klm/h for 2 hours straight when up in the NT with no problems.

We ran Yokohama road tyres (not R's) for 6 hours flat out at 36 psi hot. Similar pressures on R tyres of 3 different brands for 3 X Bathurst 12 hours, 4 X 6 Hours, 3 X 2 hours and 1 X 24 hour. That's my experiences.

The people who benefit most from "40 psi cold pressure advice" are firstly those that simply don't check their tyre pressure and have 20 in one and 35 in another etc. Cars that have low performance tyres and high profiles and mostly those with bad suspension geometry. There is some justification, but Skylines are high performance cars and their owners should have the other items covered, Personally I am not going to give "wrong" advice to people who have done the "right" things. Much better to give them the "right" advice and tell them why.

My 20 cents worth:cheers:

[Memph]

well i guess this thread is pretty much over, but for what its worth i have 235 45 17 rubber all round and use around 28 on the rear and 32 ish on the front..

seems to work well for me...

Though i do have bilstein shocks, whiteline springs, and whiteline sway bars, i seem to notice a lot of inner wear on the rear tyres....

?

[Duncan]

hahah SK, I'll bow to your experience as usual.....

but tell me, generally, apart from the risk of blow out, what is the downside of running higher tyre pressures?

[Sydneykid]

hahah SK, I'll bow to your experience as usual.....

but tell me, generally, apart from the risk of blow out, what is the downside of running higher tyre pressures?

Excessive inflation pressure always wears the middle of the tyres on cars with good wheel alignment. On cars with poor wheel alignment, it generally increases the wear on the tyre in the area where the innappropriate alignment is causing problems. This occcurs because of ballooning, as a consequence the other effect is less contact patch on the road. So it must ultimatley result is lower grip levels. Another side effect is reduced feel through the steering (ie; goes light), when the pressure gets way too high it becomes difficult to feel excessive slip angles.

On some cars (with innappropriate wheel alignment) it can decrease the tyre wear. But the reality is fixing the suspension geometry would give a far superior all round improvement (ie; better grip, feel and wear).

Lastly, we increase tyre pressures in the wet, some say to decrease the contact patch and therefore decrease the chance of water build up between the tread pattern and the road. The reality for us is that all it does is compensate for the smaller increase in pressure as a reult of the lower heat levels. By increasing the cold tyre pressure in the rain, we end up with running (hot) tyre pressures much the same as in the dry.

[IanH]

235/40-18 Front & 265/35-18 Rear both running 32psi Cold (and with an OK geometry setup - could be better as I would like some decent camber adjusters). Works well for me.

[Oosh]

I have 225/50/16 and tend to put in 36psi hot but that was more of a stab in the dark than anything. I have a R32 with TEIN HA's running 4-6 clicks from hardest.

Any advice specific to my setup is most welcome.

Cheers.

[leech_]

yea i should have mentioned mine are 36psi hot with 225/45/17