radial rollout

[thumper]

I am wondering about stagger with radial tires.I know the measuring tape shows no stagger difference with air pressure but on the car it seems like there is a change in the effective rollout.On my front wheel drive with a locked diff I noticed when I lost air in the RF the srtong pull to the left I had with different size tires was gone.Looking at the car the wheel was closer to the ground just like stagger would do.It takes a larger ait pressure difference to create the stagger change but doesnt it work the same as a bias tire?So air can create an effective stagger on a radial on a dirt track where you run 12 to 18 pounds of air.I found the taller the sidewall,the better air management works on dirt.Any ideas??

[NickHolt]

With radials you are working with sidewall stiffness rather than tire circumference unlike with the bias ply tires most racers are used to. Adding/removing tire pressure adds/removes effective spring rate (increases or decreases wall stiffness) from that corner with the radials. Two identical radial tires will show little or no change in circumference with five pounds difference in pressure between the two tires. But they sure will handle differently with 5 pounds difference.

 

Actually radials are a bit easier to tune with than with bias ply tires once you figure out to do about stagger since the tires will tell you what stagger you'll be running instead of you telling the tire what stagger you want. So, find out what stagger you can get with different size tires and tune around that amount no matter what it is.

 

Then play spring rate changes using tire pressures. Of course, you will need to use your pyrometer to get the cambers right and to k make sure you don't get too much pressure (center of tire gets too much hotter than the outsides) or to little pressure (center reading is too much cooler than the outside readings).

 

Nick