Autocross lateral G's results
05-20-2003, 06:59 PM
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Autocross lateral G's results
During my recent autocross, I finally brought my G-Tech meter and obtained maximum instantaneous g-force readings during my runs. I was quite surprised by the results. In my better runs I had readings from 1.04 up to 1.13. I'm quite surprised by these readings, but I have no reason to doubt them except to account for some accuracy tolerance of the instrument.
I have a Ruf equipped suspension, Ruf wheels with new S-03's, Ruf shock tower, lowered, ....The conditions were perfect 70F with medium roughness asphalt that was mostly flat with some mildly positive camber sections.
I guess the real test would be to try out on some other cars at the next autocross for comparison readings.
Any comments?
I have a Ruf equipped suspension, Ruf wheels with new S-03's, Ruf shock tower, lowered, ....The conditions were perfect 70F with medium roughness asphalt that was mostly flat with some mildly positive camber sections.
I guess the real test would be to try out on some other cars at the next autocross for comparison readings.
Any comments?
05-20-2003, 10:59 PM
#2
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I've actually used the "Continuous G" feature to compare grip at varying tire pressures. It's a great tool for tuning and a lot of fun. <img border="0" title="" alt="[Wink]" src="wink.gif" />
05-21-2003, 09:05 AM
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Here's an excerpt from my previous post:
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> Since traction is critical at autocross events, I ran these tests under similar conditions. I drove several miles on an expressway and through residential streets prior to finding a nice, secluded parking lot to conduct the tests. To get a continuous g reading, you drive your car in a circle and accelerate gradually until you lose traction. You must maintain a specific force level for at least 3 seconds to register a reading.
I have 17" wheels with 205/50 and 255/40 tires front and rear. I set the pressure level the same for all four tires and kept the steering wheel cranked at approximately the same point for all readings. These are the best numbers obtained at the various settings:
44 psi 0.91
40 psi 0.90
36 psi 0.88
32 psi 0.84
In my experience the difference between cold and hot pressure, under normal driving conditions, is approximately 4 psi, so evidently the Porsche engineers were right on the money when they suggested 36 psi all around on 17" wheels. Once your tires warm up, that number will apparently yield the best combination of traction and ride comfort.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">
</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> Since traction is critical at autocross events, I ran these tests under similar conditions. I drove several miles on an expressway and through residential streets prior to finding a nice, secluded parking lot to conduct the tests. To get a continuous g reading, you drive your car in a circle and accelerate gradually until you lose traction. You must maintain a specific force level for at least 3 seconds to register a reading.
I have 17" wheels with 205/50 and 255/40 tires front and rear. I set the pressure level the same for all four tires and kept the steering wheel cranked at approximately the same point for all readings. These are the best numbers obtained at the various settings:
44 psi 0.91
40 psi 0.90
36 psi 0.88
32 psi 0.84
In my experience the difference between cold and hot pressure, under normal driving conditions, is approximately 4 psi, so evidently the Porsche engineers were right on the money when they suggested 36 psi all around on 17" wheels. Once your tires warm up, that number will apparently yield the best combination of traction and ride comfort.
</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">
