TYRES PRESSURES - DUNLOP 'R'
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From: Johannesburg, South Africa
TYRES PRESSURES - DUNLOP 'R'
This weekend I will participate in a track day. It is the first time I will be using Dunlop 'R' tires on my '90 C2. Tire widths are F 205x16/50 and R 225x16/45. Wheel alignment is as per factory spec. What cold tyre pressures should I be using? How much will tire pressure increase with heat buildup?
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From: Parafield Gardens
Dear Johan,
You are going to have to experiment. A huge amount depends on the track temperature. You need heat in the tyres on the track so you aare advised to keep pressures low to start with. Low as compared to recommended that is. 36/44 is recommended by Porsche for road use. I know racers in the USA (this is a much debated subject) who are running 29/37, 29/34 even but this is generally with wider tyres. Maybe start with 32/38 and work from here.
Sniff around before you go out. Ask other competitors. However in the end you have to find which is comfortable for you on any given day with a specific set of track conditions. I also recommend you use an accurate and properly calibrated tyre pressure gauge,
Ciao,
Adrian
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You are going to have to experiment. A huge amount depends on the track temperature. You need heat in the tyres on the track so you aare advised to keep pressures low to start with. Low as compared to recommended that is. 36/44 is recommended by Porsche for road use. I know racers in the USA (this is a much debated subject) who are running 29/37, 29/34 even but this is generally with wider tyres. Maybe start with 32/38 and work from here.
Sniff around before you go out. Ask other competitors. However in the end you have to find which is comfortable for you on any given day with a specific set of track conditions. I also recommend you use an accurate and properly calibrated tyre pressure gauge,
Ciao,
Adrian
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From: TX
I would start with 32F and 36-38R cold. On a hot track I've seen up to around +11 lbs of pressure. Of course, how you drive has an impact, in addition to track temperature. If you're just starting out, you may not be driving aggressively, and thus may not work the tires as much as a more experienced driver.
Factory spec wheel alignment isn't very well suited for the track. If you find you'll be doing more track driving, you may want to consider the Carrera RS alignment, which is still not very aggressive, but better than the stock C2 alignment specs for dual purpose driving.
Factory spec wheel alignment isn't very well suited for the track. If you find you'll be doing more track driving, you may want to consider the Carrera RS alignment, which is still not very aggressive, but better than the stock C2 alignment specs for dual purpose driving.
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From: Naaldwijk, The Netherlands
Bill, do I understand you correctly that you're saying the RS alignment would be better on a C2 compared to the factory alignment? In what sense, and wouldn't it hurt the car?
Thanks.
Thanks.
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From: Johannesburg, South Africa
Thanks for your help guys. I had a discussion with two of our local (Johannesburg)experienced Porsche racers and they recommended independently pressures of 23/24 F and 27/30 R cold. It seems as if our altitude 5500 ft. has an influence to start marginally softer than your recommendations. Ambient temperature tommorrow is expected to be 16 Celcius.
Once hot they feel that the tires should be at about 36 F&R. It has also been suggested that I run 255 wide at the rear. I will also be using a pyrometer during testing and will report the findings back to you.
Once hot they feel that the tires should be at about 36 F&R. It has also been suggested that I run 255 wide at the rear. I will also be using a pyrometer during testing and will report the findings back to you.
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From: Parafield Gardens
Dear Johan,
A mile high also makes a huge difference to answers on such things. Could I ask next time that you advise us of these conditions. This of course applies to anyone who asks similar questions.
Ciao,
Adrian
911C4
A mile high also makes a huge difference to answers on such things. Could I ask next time that you advise us of these conditions. This of course applies to anyone who asks similar questions.
Ciao,
Adrian
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From: TX
[quote]<strong>Bill, do I understand you correctly that you're saying the RS alignment would be better on a C2 compared to the factory alignment? In what sense, and wouldn't it hurt the car?
</strong><hr></blockquote>
Arthur and I also discussed this offline. For others, I said that for more sporting usage, the Carrera RS alignment specs would be better, and doesn't hurt the car. I believe Bruce Anderson also recommends the RS alignment specs in his book.
</strong><hr></blockquote>
Arthur and I also discussed this offline. For others, I said that for more sporting usage, the Carrera RS alignment specs would be better, and doesn't hurt the car. I believe Bruce Anderson also recommends the RS alignment specs in his book.
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From: Oxford, England
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The advice I would give would be to just turn up with a regular car with regular tyre pressures and concentrate on driving smoothly and safely within your own limits and get the car back home all in one piece!!!
I have always been an advocate of driver improvement first, car improvement second!!
have fun!!!!!
The advice I would give would be to just turn up with a regular car with regular tyre pressures and concentrate on driving smoothly and safely within your own limits and get the car back home all in one piece!!!
I have always been an advocate of driver improvement first, car improvement second!!
have fun!!!!!
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From: Johannesburg, South Africa
OK, Now feedback on Saturdays track day. The Dunlop 'R' Tires were about 3.5 sec per lap faster than SO2's at the Zwartkops circuit which is 2.4km in length. (That is for the first few fresh laps). Soon the insufficient camber settings made the tires overheat with excessive wear on the outsides.
Wheel alignment is currently being reset with -1.6 deg camber front and -2.1 deg. camber rear. It appears as if the ideal hot pressures are 2.0 bar (29lb) front and 2.5 bar (36lb) rear.
Overall impressions: Tire improvements seem to be the most cost effective way to improve lap times. To knock off 3.5 sec per lap on power alone would cost a bundle!
Wheel alignment is currently being reset with -1.6 deg camber front and -2.1 deg. camber rear. It appears as if the ideal hot pressures are 2.0 bar (29lb) front and 2.5 bar (36lb) rear.
Overall impressions: Tire improvements seem to be the most cost effective way to improve lap times. To knock off 3.5 sec per lap on power alone would cost a bundle!