Bill51sdr

Based on what?

Mongo

I'm running 36 in the front and 40 psi in the rear. I like it!


44 psi rear pressure is fine as long as you don't autocross the car at that high of a pressure....it will go boom boom.

sharkmeister85

Based on a world wide consensus of tire scientists. There can be no further discussion or debate.
Glenn

heinrich

Bill I'm not interested in a verbal sparring match. As such, go run whatever pressures tickle your fanny, see if I care. As for me I will run what I have experienced to be safe pressures and give ultimate grip, which on my 16's; 17's; 18's and 19's .... 32 all-round for street driving (cold). I'll continue advising 928 owners into the future to shoot for 32 cold. have a nice thread Bill.

Shane

Really? But I thought you said one rear tire should be up around 60-70 psi so you can do burn outs real easy...

Bill51sdr

My problem is your assertion that 44 psi is an unsafe pressure, which clearly it is not, you and I both showed that, ironically. I have no problem with anybody running whatever they deem safe or enjoyable.

Have a good day H, I enjoyed the debate

heinrich

What is the max tyre pressure rating of your tyre manufacturer Bill? Max permissible PSI on many tyres is 44psi. Many new tyres can bear as much as a maximum of 51psi. Are you sure that when you inflate your cold tyre to 44psi it remains under the tyre manufacturer's absolute maximum permissible pressure when it gets hot?

bigmac

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I used to run 34 in mine all the way around, and this was just fine for sedate driving. But when I check tire pressures after some spirited driving, they were up around 38psi, even more when I was running at the track. So now I drop them to thirty when I know I'm going to put a lot of heat into the tires.

Shane, One could argue the reason your pressures went up is that they were underinflated to start with. Sincerely. Mac
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Bill51sdr

H the maximum you speak of is built into the cold psi specification. The manufacturers expect the increase you speak of and there is a margin for it. If you are racing a car and heating the tires up in that way, it is the driver's responsibility to adjust the pressures. It becomes quite apparent when the pressures become too high in that environment anyway. If you race, the cold pressures will be set lower to allow for the anticipated increase.

Oh! AFAIK, the max COLD pressure on my current tires is 45 psi.

Bill51sdr

Underinflated tires is a condition Ford is intimately familiar with, i.e. Explorer. In this case, the overheating was localized to the sidewalls with the resulting catastrophic tire failure. But yeah, underinflation does generate a lot of heat and would increase pressure a bit, to a point.

Richard S

At the ORR's, almost all drivers increase the cold tire pressure before the race. I set it at 40psi before the start. It is done in order to keep the tire temps lower during the event. The organisers keep tire data for each car, and used to measure tire temps for every car after the finish line. Is Porsche recommending a high cold tire pressure keeping in mind the speed potential of our cars?

Rich

heinrich

So, if you are comfortable pushing the tyre to the ABSOLUTE MAXIMUM cold pressure, that is your choice but 1) I am not comfortable with it and 2) my experience on multiple cars is that the MAXIMUM is TOO HARD and causes loss of traction.

Now how about you explain to the class why you believe REAR tyres deserve MORE PRESSURE than the fronts?

Bill51sdr

I will have to defer to Porsche on that one H for the definitive answer, but I suspect it is the weight of our beloved beasts that determined the 16" wheel specification. There is a lot of weight in the rear of the 928.

heinrich

You go right ahead and do that Bill. As for me I will defer to the opinion od Good Year:

QUESTION: Why are some tires in the same size stamped on the sidewall with a maximum pressure of 35 PSI, while others have 44 PSI?
ANSWER: Within the past several years, the Department of Transportation has amended the Federal Motor Vehicle Safety Standards to allow standard load (SL) tires to be marked with 44 PSI maximum inflation pressure (instead of 35 PSI) with no increase in load carrying capacity. This amendment came about because of the increasing awareness that improved fuel economy may be achieved through the use of higher inflation pressures. No matter what the maximum pressure indicated on the sidewall, only recommend the air pressure as highlighted on the Vehicle Tire Information Door Placard. NEVER EXCEED THE MAXIMUM INFLATION PRESSURE LISTED ON THE SIDEWALL OF THE TIRE.

and

QUESTION: When mounting an auto tire on a rim, what is the maximum air pressure recommended to seat the beads:
ANSWER: After lubricating the beads of an auto tire, no more than 40 PSI, should be used to seat the beads. If the beads don't seat at 40 PSI or less, deflate the tire, turn it 180 degrees on the rim, and inflate again. ONCE AGAIN, NEVER EXCEED 40 PSI WHEN MOUNTING AN AUTO TIRE ON A RIM IN YOUR ATTEMPT TO SEAT THE BEADS.

heinrich

VERY weak answer Bill.

Your car has 50/50 weight distribution. Other than BLINDLY reading and following the sticker on your 25yo car, please explain in logical terms WHY you think you need more pressure in the rear of your 928.