69 Charger on the autocross

[68 Sport Satellite]

I actually dont adjust mine much. I run 45 front for autocross and 40 rear. For winter I'll take them down to 35 for just sitting. They're rated for 50 or 55 so I don't have any issue running them high.

wow, that sounds pretty high. Grip is nice at those pressures I'm assuming? I had a friend show me the chalk tread test before for maximum contact patch and my rear 555R's are at max contact patch width at 25psi. I increased them up to 28psi for stiffer sidewall, but maybe I'll try running them at 35-40 on the street and see how it feels. Thanks.

 

[SlinktRR]

I run them at 32psi right now, I will probably match rusty for autox. They have a good sidewall compared to any of the MT drag radials, I have no qualms about putting them in the front but right now I only have 15x7's for using 225/70 so I'm still running BFG.

I'm ordering 15x8 and 275/60 from Summit for the front. If you order wheels and tires combo they will mount and balance for free. I can even rotate my tires now lol. Front to back at least, they are directional so you can't do a standard rotation.

 

[Rusty knuckles]

wow, that sounds pretty high. Grip is nice at those pressures I'm assuming? I had a friend show me the chalk tread test before for maximum contact patch and my rear 555R's are at max contact patch width at 25psi. I increased them up to 28psi for stiffer sidewall, but maybe I'll try running them at 35-40 on the street and see how it feels. Thanks.

They're certainly rounded and the contact patch is less at the higher pressure. Everything is a compromise. I'm fighting sidewall deflection. The higher air combats that.... at the expense of contact patch. However, the tire deflection actually gets you some of that back.

Here's what 35psi gets you. Darn near scrubbed the letters on the tire. At 45 I'm just touching that shoulder indicator about an inch up from the edge of these scrub marks. At 35 psi I was understeering like crazy. At 45 I don't. My fastest runs are usually the 3rd run in a heat, after tire temp has raised, with tire pressure too.

 

[68 Sport Satellite]

They're certainly rounded and the contact patch is less at the higher pressure. Everything is a compromise. I'm fighting sidewall deflection. The higher air combats that.... at the expense of contact patch. However, the tire deflection actually gets you some of that back.

Here's what 35psi gets you. Darn near scrubbed the letters on the tire. At 45 I'm just touching that shoulder indicator about an inch up from the edge of these scrub marks. At 35 psi I was understeering like crazy. At 45 I don't. My fastest runs are usually the 3rd run in a heat, after tire temp has raised, with tire pressure too.
View attachment 1918855

after you posted this I read some other non-mopar threads about people running these tires (and other tires) and one guy made a very good point - contact patch is a good baseline, but it doesn't tell the whole story because it's usually taken going straight and not leaning in turns. Camber settings also affect how the tire will behave in turns. So, I'm inclined to run some higher pressures on mine and experiment. Thanks for the motivation! By the way, I'm only running the 555R's in the back and all season Mickey Thompson Sportsman S/T's up front, both 15". I may try some different tires at some point, but I'm 99% street.