1) While tire pressure is very important, especially on the track, "stickies" are VERY prone to temperature. Cold "stickies" don't stick.
2) The H mark is a relative term on the S2K and several owners have reported variation in where the H mark is on the stick. If there is too much oil in the pan, the crankshaft will pick it up and cause cavitation which introdues air into the oil. Air in the oil will reduce oil pressure and this reduced pressure may prevent V-Tec from coming on. Might try draining oil a bit and see if that helps.
3) Your on your own here.......might want to email these guys:
http://www.autopia-carcare.com/autopia/noname.html

 

I don't know what you guys are thinking running these high tire pressures. Tires will give more grip with lower pressure than high pressure. Turn in may be more instant with higher pressure but the ultimate grip will be with the lowest pressure that does not allow the tire to roll over onto the sidewall in hard cornering. The autocross guys will "chalk" their tires on the side walls and if any wears off after a run they up the pressure until it doesn't.

For my money the S02s handle best on this car at 32 all around. This may be because of my driving style where I am on the gas to set the rear through the turns. Your results may vary depending on your style.

 

Bieg, I'll have to dig out the various authorities on tyre pressure and start to post them for you. Here in Oz, and in my experience everywhere else in the world, all road testers and magazine writers (I'm not just talking journos, I am talking writers who are also amateur or professional racers) recommend a minimum of 36psi for ANY road vehicle on the street. This even includes US boats (Devilles and Town Cars). The only reason low pressures are recommended by manufacturers is for a smooth ride.

Yesterday at the track our chief instructor (who also happens to be the current Australian Porsche club champion) was berating us for running anything under 39psi and advocating up to 45psi.

My experience with tyre pressures around the 32psi mark is that the vehicle will slide all 4 wheels easily. The reason this happens is that 32psi is not enough pressure to get the full tread width of the tyre touching the road (the middle of the tyre is sitting slightly higher than the outsides). Without the full tread width providing grip you cannot be getting maximum grip from your tyres.

 

That is just wrong. Higher pressures will inflate the tire to the point where it will ride on the center of the tread and not let the side of the tread touch - not the other way around as you state. Anyone that has ever taken tire temps across the inside, center, and outside will tell you that. The ideal pressure is where the temps are equal across the whole tire. Too much pressure and the center will run hot, too little and the edge of the tread will run hotter.

I don't know who your experts are but they are wrong. High pressure serves to keep the tire from rolling over onto the sidewall of the tire under high cornering speed conditions. Anything higher than what is needed for that is going to take away grip.

According to your theory if the tire had no air the edge of the tread would not be touching the ground. Strange logic.

[Edited by Bieg on 03-26-2001 at 09:27 AM]

 

Beig-

Who is the authority you refer to when you state that 32psi is the optimum pressure for the S0-2?

Is that a manufacturers recommendation or just your "expert" opinion? It might lend your argument more credibility if you can speak from experience ie track time, autoX, engineering background.

I'm intersted in your reasoning and just like proof especially when your dising others opinions so strongly.

Thanks

 

My knowledge of this is not first hand, but I have agreed with Bieg so far- my understanding was that you get better traction with lower pressure and better steering with high pressure at the cost of losing some grip. I've heard this throughout my life from various sources.

Overinflation will cause uneven wear, but so will underinflation. 32 is recommended for the car/tire combo, so its not underinflation for sure. This should produce a flat/even tire surface.

I can tell you from first hand experience that when my tires are overinflated, its easier to break them loose at launch. When they are at lower pressure, they don't spin. This would seem to agree with what Bieg has said. I've also seen numerous posts in the past suggesting lower tire pressure gives better traction...

My .02$ worth...

-B

 

HONDA. Check your owners manual.

NOTICE THEY SAID INCREASING TIRE PRESSURE ROUNDS THE PROFILE AND DECREASES THE CONTACT PATCH.

This technique is used to help mitigate Hydroplaning.
More pressure = LESS contact patch.

Or maybe you don't think Tire Rack knows anything about how air pressure effects tire contact patchs ?

"...it is better to start off with a higher pressure and work your way down to get the most contact patch"

Nowhere does it say that you get more contact patch with higher air pressure. I will say it again, THE OPTIMUM TIRE PATCH WILL BE OBTAINED WITH THE LOWEST PRESSURE THAT DOES NOT ALLOW THE TIRE TO ROLL OVER ONTO IT'S SIDEWALL IN HARD CORNERING CONDITIONS. ANY MORE PRESSURE WILL SERVE TO REDUCE THE CONTACT PATCH.

Take some liquid shoe polish (white) and put some marks where your sidewall meets the tread. Run your car hard into the turns. If any of the white is scuffed off you are rolling over onto the sidewall and need to increase the pressure. Keep doing this until you have optimized the pressure.

For driving on the street 32 is just about perfect with a stock S2000 with stock wheels and tires.

Of course that is just my opinion (informed as it may be)




[Edited by Bieg on 03-26-2001 at 12:15 PM]

 

Beig-

I don't disagree with your max grip at X pressure assertion.

Maybe we have forgotten the original question.

The issue at hand or in question was not about maximum grip, it was about control of the tail.

Fact- The S2000 is tail happy. It has been highly documented as I'm sure you now.

Fact- Higher pressures in the front tires lower pressures in the rears will help "tame" this "tail happiness".

So I don't disagree with your astute findings, I just think we got a bit sidetracked........

This was not about max grip. Obviously Optimum pressure = Optimum grip BUT Optimum grip does not necessarily give you the best handling characteristics at the limit. Varying pressures F/R thus varying grip F/R can lead to a more "controlable" car it the limit.

Of course that is just my opinion ("uniformed" as it may be)

 

Beigh, I speak from experience and the findings are simple (this not theory, this is the way it feels on the road). This is driving on the road and not the track:

- When I was running 31psi at the back - the back was very slippery and loose. The limit of grip and the back was not what I'd call high ... I had it stepping out under circumstances that I'd expect other cars to keep on gripping. I doubt it's my driving as I was getting the back stepping out around corners with the car being balances on medium throttle and not going too fast.

- Then I upped the back pressure to 35psi - the car was transformed. The back has higher limits and grips as it should. I can still get the back out but I have to actually try to do so now unlike the 31psi scenario. I drove on this pressure for a munth and was very happy ... the back would stay planted even when off-throttle mid corner.

- Now I'm running 37psi at the back just to see what will happen (only upped them yesterday so no comment yet).

Also, I've dome about 1/2 dozen 'racing courses' and in all of them they recomend 'high' tyre pressures ... as high as 50psi for the track. On my prev car ('93 MR2) I had S02 tyres as well and was running 38psi at the back ... went though 4 sets of tyres and had even wear and very good balance/grip on the car. My fathr has a 265kW 'sports sedan' with 235/40/18" S02 tyres on it. He was running 34psi in them before he went for a 2000km trip ... he absolutelly shredded the rear tyres (with high speed cruising) ... they were shreaded to the point of rubber chuncks hanging of them ... if was the inside (edge) of the tyre that gave way. He just did not have enough pressure. He spoke to the manufacture (or the vehicle) and now he's running 44psi all around and if he does another 'high speed' trip then 50psi is what he needs to be running.

ps. I know that having the prssures 'too' high is bad and will overinflate the tyres but 40psi is not 'too high' ... in anything 32psi is 'too low' as the middle of your tyre is not doind enough work. The lower the profile on the tyre, the higher the pressure you need to run for the tyre to work troperly and to not get 'shreded' ... if you take it to an extreme, look at the pressures that push bikes are running - it's about 100psi and the reason is their incredibly low sidewalls.

 

I speak from experience also. With 38 pounds in my tires all around the car had much less grip than with Honda's recommended 32.

Did you use a calibrated tire gauge? Racer's Warehouse has them and they are individually calibrated and certified accurate. This is what I use.

Did you check your pressures when they were stone cold?

When you upped the pressures were the tires stone cold?

32 pounds cold with a calibrated gauge is real close to being perfect on the street IMHO.