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Posted by: dan10101 Oct 2 2019, 08:47 PM

I know these aren't the ideal tire for the purpose, but I just want to get the tire pressures as good as they can be.

295x30x18 and 245x35x18
2500# Yes it's my V8 car.

The current situation at hand is our Enduro autocross. It's about a 4+ minute run of 5 laps. (unless you're Britain Smith, then it's closer to 3:30...)

I would also like to know how this changes with a normal Autocross of about 1 minute and then again how it changes with a 20 minute road course.

Thanks
Dan




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Posted by: GregAmy Oct 3 2019, 08:08 AM

I presume you mean 295/30-R18 and 245/35-R18?

Radial DOT R7s you're probably looking for around 36-38 hot.

For autocross you should probably be running A7s. I run A7s on my 2600# road race car in cool weather, and shoot for 38 hot with either tire.

https://www.hoosiertire.com/images/content/files/TCTR7_A7.pdf

Posted by: jmz Oct 3 2019, 01:50 PM

I run A7s on my 914/6 GT as a road race tire. Since the car is so much lighter than the big american iron they a/x compound seems to work well as a road race tire for these cars. I start very low at about 17-18lbs cold and shoot for 24-25 hot. I would think for a/x the R7 wouldn't even get warm...

QUOTE(GregAmy @ Oct 3 2019, 09:08 AM)

Posted by: dan10101 Oct 4 2019, 09:46 AM

QUOTE(jmz @ Oct 3 2019, 12:50 PM)

I run A7s on my 914/6 GT as a road race tire. Since the car is so much lighter than the big american iron they a/x compound seems to work well as a road race tire for these cars. I start very low at about 17-18lbs cold and shoot for 24-25 hot. I would think for a/x the R7 wouldn't even get warm...

QUOTE(GregAmy @ Oct 3 2019, 09:08 AM)

I presume you mean 295/30-R18 and 245/35-R18?

Radial DOT R7s you're probably looking for around 36-38 hot.

For autocross you should probably be running A7s. I run A7s on my 2600# road race car in cool weather, and shoot for 38 hot with either tire.

https://www.hoosiertire.com/images/content/files/TCTR7_A7.pdf

Posted by: andys Nov 22 2019, 10:15 AM

Some years back, I had a conversation with one of the engineers at Hoosier regarding a tire pressure starting point for non DOT race tires. He advised to run pressures at 1% of the vehicle weight. From there, adjust the pressures to attain best temp profiles when combined with the proper suspension adjustments.

Andys