Tire pressures and AutoCross

[AlphaDigital]

Doesnt make sense to me either, I see a mix of people saying one or the other LOL

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[Dave B]

Maybe if you had a soft sidewall tire and virtually no negative camber, raising the front pressures might work as otherwise when the car rolls it will lift up the inside of the contact patch. Still don't get why decreasing the rear pressures are going to help understeer. Maybe there should have been more proof reading of the content.

 

[wildbilly32]

Somebody help me with why a stiffer rear sway bar would help eliminate understeer as they are advertised to increase grip. I'm trying to decrease rear grip. I'm guessing it relates to body roll dynamics...?

 

[AlphaDigital]

Somebody help me with why a stiffer rear sway bar would help eliminate understeer as they are advertised to increase grip. I'm trying to decrease rear grip. I'm guessing it relates to body roll dynamics...?

https://www.motortrend.com/how-to/h... quality issue,controlling the rear body roll.

 

[wildbilly32]

https://www.motortrend.com/how-to/how-to-understand-sway-bars/#:~:text=Adding a rear sway bar solves the ride quality issue,controlling the rear body roll.

Got it thanks:

 

[wildbilly32]

So this leads to the next conundrum. Safe to assume it is better to tighten up the end that is suffering traction loss(front) before loosening up the end that is stuck(rear)?

Since I have chosen to stick with 20" rims for the playtime AutoX I do and, therefore, limited on choices for tires due to limited TW specs at this point I think I'll keeping playing with pressures in the OEM Contis until I burn those up. Honestly the Contis worked well this season.

 

[AlphaDigital]

I would go with a stiffer and wider rear sway bar as its supposed to assist with getting you better rotation.

 

[Dave B]

Stiffening up the rear will allow for more rotation.

 

[jrow3]

Somebody help me with why a stiffer rear sway bar would help eliminate understeer as they are advertised to increase grip. I'm trying to decrease rear grip. I'm guessing it relates to body roll dynamics...?

Rear bars, will "loosen" the rear end, and typically cause oversteer. Generally for autocross most drivers prefer a much looser rear end, and thus will both run an incredibly stiff rear bar (karcepts makes the stiffest one), as well as running higher rear tire pressures, and even a smaller rear tire, all to reduce the grip on the rear and allow the car to rotate in corners.

To that end all season I ran 275 RT660's at 36 psi up front, paired with 245 RT660's at 38-42 pis (depending on how much I wanted the rear to slide around, higher for a tighter course, and lower for a more sweeper focused course). All the above with the karcepts bar set to full stiffness.

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