Tire Pressures
03-31-2003, 06:38 PM
#16
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My understanding is that (within limits) more pressure actually gives more traction. It sounds counter-intuitive to me, but I have been told the same thing over and over again by people who know what they are talking about. I'm sure you will eventually reach a point where this is no longer true, but I don't know where that point is.
Changing the front pressure from the recommended 29 psi (944 na) to 36 psi increases traction on the front wheels. It is also my understanding, as mentioned by Pete, that the lower psi on the front is recommended so as to increase understeer. Increasing the pressure to 36 gives the front tires more grip and more neutral handling. I believe this is also why Porsche recommends equal pressures all the way around for 951s: since they have wider rear tires, equal pressure all the way around means less grip on the front and a tendency to understeer.
I run 36 psi all the way around on my '86 944 na.
Changing the front pressure from the recommended 29 psi (944 na) to 36 psi increases traction on the front wheels. It is also my understanding, as mentioned by Pete, that the lower psi on the front is recommended so as to increase understeer. Increasing the pressure to 36 gives the front tires more grip and more neutral handling. I believe this is also why Porsche recommends equal pressures all the way around for 951s: since they have wider rear tires, equal pressure all the way around means less grip on the front and a tendency to understeer.
I run 36 psi all the way around on my '86 944 na.
03-31-2003, 06:51 PM
#17
Big thirst, Sore Thumbs
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Napoleon
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Napoleon
Thread Starter
More pressure reduces footprint, so it can't give you "More traction" but it does give a more precise feel that can be mistaken for being "Grippy"
Look at drag racers, their tires are so low that the sidewalls actually bend (And yes there are other factors, and yes they are designed to) You reduce pressure in your tires if stuck in the snow, to get more traction.
But there are many other factors.
For instance, on my Duster (RWD) it actually started performing better in the snow with larger tires in the back, even though it reduces psi on the footprint, and technically should make it more likely to spin, the reverse is happening, but as always there are trade offs, a point of diminishing return.
Basically as others have said.
Experiment and see what works for your driving and style. <img border="0" title="" alt="[Wink]" src="wink.gif" />
Re-doing your grounds helps traction too.
Look at drag racers, their tires are so low that the sidewalls actually bend (And yes there are other factors, and yes they are designed to) You reduce pressure in your tires if stuck in the snow, to get more traction.
But there are many other factors.
For instance, on my Duster (RWD) it actually started performing better in the snow with larger tires in the back, even though it reduces psi on the footprint, and technically should make it more likely to spin, the reverse is happening, but as always there are trade offs, a point of diminishing return.
Basically as others have said.
Experiment and see what works for your driving and style. <img border="0" title="" alt="[Wink]" src="wink.gif" />
Re-doing your grounds helps traction too.
03-31-2003, 07:25 PM
#18
Rennlist Member
We need to differentiate between straight line traction and cornering traction.
Drag racers use low pressure because that helps traction in a straight line as it allows the sidewall to deform and increase the size of the contact patch. They also use tires with soft sidewalls for the same reason. Drag radials make for poor track tires for this reason.
In cornering, that low pressure works agasint you as it allows the tire to roll onto the sidewalls. So higher tire pressures will give you better turn in and better grip in corners (to a point, of course) as it keeps the sidewall from flexing and maintains the size and shape of the contact patch.
Drag racers use low pressure because that helps traction in a straight line as it allows the sidewall to deform and increase the size of the contact patch. They also use tires with soft sidewalls for the same reason. Drag radials make for poor track tires for this reason.
In cornering, that low pressure works agasint you as it allows the tire to roll onto the sidewalls. So higher tire pressures will give you better turn in and better grip in corners (to a point, of course) as it keeps the sidewall from flexing and maintains the size and shape of the contact patch.
03-31-2003, 10:49 PM
#19
Burning Brakes
With my setup, 32 all round works great, very neutral.
At the end of one of my sessions at a track day I pulled into the pits and quickly tested, 36 all round!
At the end of one of my sessions at a track day I pulled into the pits and quickly tested, 36 all round!
03-31-2003, 11:12 PM
#20
Big thirst, Sore Thumbs
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Napoleon
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Thread Starter
ninefiveone
Your absolutely right.
And while 944 are known for cornering, they also need straightline traction.
Getting started in poor traction conditions for instance.
Your absolutely right.
And while 944 are known for cornering, they also need straightline traction.
Getting started in poor traction conditions for instance.
04-01-2003, 11:23 AM
#21
Three Wheelin'
What air gauges do you guys use? I've always gone with the fairly standard pop-on sticks-out kind you find at auto parts counters. Accurate enough, I hope. I'm not about to buy a digital sucker...
04-01-2003, 11:32 AM
#22
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by Tremelune:
<strong>What air gauges do you guys use? I've always gone with the fairly standard pop-on sticks-out kind you find at auto parts counters. Accurate enough, I hope. I'm not about to buy a digital sucker...</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica"><img src="http://www.tannerracing.com/TireGauges/images/1c_glowgauge.jpg" alt=" - " />
It is pretty difficult to get precise tire pressures without a air release button.
<strong>What air gauges do you guys use? I've always gone with the fairly standard pop-on sticks-out kind you find at auto parts counters. Accurate enough, I hope. I'm not about to buy a digital sucker...</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica"><img src="http://www.tannerracing.com/TireGauges/images/1c_glowgauge.jpg" alt=" - " />
It is pretty difficult to get precise tire pressures without a air release button.
04-01-2003, 12:48 PM
#23
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The optimum tire pressure is the one that lets the entire tread of each tire be effective when you most need it. There's no one answer - it depends on the tire wall rigidity, the tread mass and profiling, the way you want to drive, the speed ...
I run 215 wide all around on a 944na, and hit my limits at slow speeds (100 km/hr) around back-road curves signed at 30. The optimum pressure for me is way lower than mentioned here - after careful observation I run 27 psi front 30 rear (cold).
For example: in general the faster you go, the more the inertial mass of the sidewall increases traction on the edges, so the higher the pressure you need to keep the tread center response up. The rougher the road surface, the slower sidewall response will be (larger mass) and the faster the tread center, so lower pressure is better. A tire with heavy tread (usually, high wear rating) is best with higher pressures than a light tread tire...
No one knows more about your tires, car and driving wishes than you. Take the time to experiment.
I run 215 wide all around on a 944na, and hit my limits at slow speeds (100 km/hr) around back-road curves signed at 30. The optimum pressure for me is way lower than mentioned here - after careful observation I run 27 psi front 30 rear (cold).
For example: in general the faster you go, the more the inertial mass of the sidewall increases traction on the edges, so the higher the pressure you need to keep the tread center response up. The rougher the road surface, the slower sidewall response will be (larger mass) and the faster the tread center, so lower pressure is better. A tire with heavy tread (usually, high wear rating) is best with higher pressures than a light tread tire...
No one knows more about your tires, car and driving wishes than you. Take the time to experiment.