Need a little help figuring something out

[Ron Sutton]

Hi Ron,

Not necessarily a primary cause.

I see it as something that causes the local tire loading at the very outer edges of the contact patches to vary a little depending on whether it's a ridge or a groove that's underneath there
Absolutely.

, and this might be clouding the picture a bit.
No clouds. All clear.

Tire size vs wheel width may even be involved with this.
I concur, if the tire was on a wider rim, with more psi, the situation would be lessened.

I do know that kind of road surface sure feels different ("woozy") to drive over even when you aren't driving hard. Only one car/wheel/tire combination I've ever had might not have felt like that.

Norm

In the front, the tires push on both surfaces when turned far enough. The front end geometry & excessive body roll are causing the outside tire to go into positive dynamic camber & the inside tire to go into negative camber. Lance's helpful video provided insight & started on us on this working relationship. The tire loosing contact patch is the primary cause of the push. When it happens on the grooved concrete, it obviously adds another dynamic to the tires.

On pavement, the rear tires get a little "bound up" when the front tires go into a push condition, but are not snapping loose in this situation. The oscillations initiated from the grooved concrete are causing the rear tires to loose grip in that section, making the car momentarily loose, until Lance counter steers & it "catches".



The rear springs being too soft of rate & older shocks with weak valving are not able to control it. The soft rear springs ... combined with his rear sway bar & roll center ... are also contributing to his push condition ... as the car is not rolling equally or balanced.

During cornering, the suspension is traveling much farther in the rear than the front ... more than twice as much. As you probably know, when that happens, the car rolls diagonally ... working the outside rear tire more (increasing rear grip) and working the inside front tire less (decreasing front grip). This issue is simply compounding the push issue ... as is the uneven surface of the grooved concrete.

Lance & I are focused on both ends of the car ... with plans to travel the front end farther ... travel the rear end less ... and roll less. But first, we're working on steering geometry to correct the dynamic wheel angles to maximize front tire contact patch.