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Discussion Starter #1
Been playing around on my new Summer Tires (Continental ExtremeContact Sports).

Sometimes I can get em to hook *perfectly*. And I do mean perfect.

When they hook, its feels great. You can just feel em grab, no spin, and the car seems to even pull down a bit in the back.

Other times they spin on me.

After trying them different times of day with different outside temperatures, different cold (and warmed up) pressure inflation, and different amounts of warm up driving time, I've noticed two significant variables seem to determine hookup vs spin.

1) The PSI of the tire when I am doing a launch. Meaning, not the cold PSI I inflated to in the garage, but the PSI the tires are at when I do the launch. This varies due to outside temperature and due to road warm up of the air inside the tire.

2) The surface temperature of the tire.

Last night I did a fast 0-60 of 4.3 seconds. Best time I can get. I've done it now 4 times I think. Hooked perfectly, just grabbed, no spin. Rear tires were at 32 PSI, front at 34 PSI (after filling them cold in garage at 30/32). And I had been running them on the freeway for about 15 minutes before getting back to a secluded area and doing this. Outside temperature was only 57 degrees. Intake temperature was around 64 degrees (I think).

This afternoon, I did another run. Tires were now at 34 read, 36 front. Outside temp was 73 degrees. Intake temp was 84 degrees. Did same launch, and tires spun through most of 1st gear. Traction control full ON (Street Mode). Everything else Sport Mode. Pulled a 4.6 and 4.7 seconds. Difference probably entirely due to the spin on launch.

Other times I have had lower tire pressure. Was even running them 28/30 cold for awhile. And did a few 0-60s with minimal warmup driving of the car or tires. And tire spin.

So seems like the tires have to be warmed up by driving (or burnouts I guess, but I don't do that as much). And the tires need to be around 32 in the rear after warmed up driving.

2lbs PSI warmed up seems to be the difference between hook and spin.

Thoughts?
 

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Is the road surface another variable, or do you always return to same stretch of road for "testing". I find my PS4S summer tires grip better at 60* and up. I haven't played with best 0-60 times yet.
 
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Discussion Starter #4
I do most of my testing at the same spot. But there is a slight difference... before or after the stoplight. Its about 20 yards difference. And I have been wondering if the patch after the stoplight is rougher and more torn up possibly...
 

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Discussion Starter #5
In doing more testing I have been noticing that the surface temperature of the tire seems to be a huge factor in traction. Which makes sense - that's why drag racers do burnouts first, to warm up the tire rubber. I haven't been doing burnouts to warm up and test on the street. Usually don't have that kind privacy or solitude. But what I have noticed is a few really good hooks at low air temperatures (57-60 deg), but the car had been running on the freeway for 20-30 minutes. So the pressure is up in the tire, but more importantly the rubber itself would be warmer from running at 70-85MPH for 20+ minutes. Conversely I have had multiple tries when the air temp was 70+ degrees, but I had only been driving the car around surface streets for 10 minutes, and even though the tires feel warm-ish, they're really not. And those times the tires spin off the line.

I need to find a place to try doing burnouts first, then a quick launch. :)
 
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