Bias Ply vs Radial

[Alan Warman]

The question I have is do you have to hit a radial slick harder than you do a bias ply slick to make it work. My set up is a Cutlass g-body with 8in rims and Toyo 9X30s. My anti squat is 144% so it hits the tire hard. It don't spin the tires but feel's like it is running over them for the first five feet. Dave Morgan is a friend of mine and he says my anti squat should be around 80%. If I drop it that low will it still hook up on a radial. I would like to go to a 10in rims and radials, I think it would run faster. Anybody have any input.

[Kenny Wigington]

It will be faster. I know on mine, it was .085 faster, from bias to radials. Some folks have picked up even more. I have run as much as 24.5 lbs, depending on track, and it hooked great. Tame some of that hit down, and you should get at least .085 out of the swap. They do not last as long though...

[mopar jeff]

Pardon me for being ignorant, but what is "anti squat" and how do you measure it?

[BlueOval Ralph]

Originally Posted by mopar jeff

Pardon me for being ignorant, but what is "anti squat" and how do you measure it?

Anti-dive and anti-squat
Anti-dive and anti-squat are expressed in terms of percentage and refer to the front diving under braking and the rear squatting under acceleration. They can be thought of as the counterparts for braking and acceleration as jacking forces are to cornering. The main reason for the difference is due to the different design goals between front and rear suspension, whereas suspension is usually symmetrical between the left and right of the vehicle.

Anti-dive and anti-squat percentage are always calculated with respect to a vertical plane that intersects the vehicle's center of gravity. Consider anti-dive first. Locate the front instant centers of the suspension from the vehicle's side view. Draw a line from the tire contact patch through the instant center, this is the tire force vector. Now draw a line straight down from the vehicle's center of gravity. The anti-dive is the ratio between the height of where the tire force vector crosses the center of gravity plane expressed as a percentage. An anti-dive ratio of 50% would mean the force vector under braking crosses half way between the ground and the center of gravity.

Anti-squat is the counterpart to anti-dive and is for the rear suspension under acceleration.

Anti-dive and anti-squat may or may not be desirable depending on the suspension design. Independent suspension using multiple control arms can be an issue if the percentage is too high (say over 30%). A percentage of 100% in this case would indicate the suspension is taking 100% of the weight transfer under braking instead of the springs. This effectively binds the suspension and turns the independent suspension into no suspension like a go-cart. However, in the case of leaf spring rear suspension the anti-squat can often exceed 100% (meaning the rear may actually raise under acceleration) yet because there isn't a second arm to bind against and the suspension can freely move. Traction bars are often added to drag racing cars with rear leaf springs to increase the anti-squat to its maximum. This has the effect of forcing the rear of the car in the air and the tires onto the ground for better traction

[Tony Curcio]

My experience with an older G-body was that the radials were more consistent with a softer hit. Occasionally, a harder hit would result in better ET's, but only on a well prepped track on a cool day.

One quick way to find out if lowering your instant center (AKA reducing anti-squat) will help is to tighten the shocks on extension. If you get to full tight and the 60 foot times are still improving, you've got to move the IC down. On a G-Body stocker, your only options are to raise the housing-end of the upper control arm mounting points, or buy a complete kit from Alf Weibe. I learned this from Dave Morgan's book by the way- tried it and it worked.

Definitely go with the 10" wheel on a 9' tire. Last- my combo picked up .17 to .18 going from bias to radial .

[greg fulk]

Alan I leave @ 2000 to 2200 with my car & anywhere from 20 to 25 psi in the tires. If your @ a "good" track you can go with more air & more "anti-squat". The Toyo's are bias? Also the only Toyo's I've seen in that size were for a manual trans also?

[mopar jeff]

Originally Posted by BlueOval Ralph

Anti-dive and anti-squat
Anti-dive and anti-squat are expressed in terms of percentage and refer to the front diving under braking and the rear squatting under acceleration. They can be thought of as the counterparts for braking and acceleration as jacking forces are to cornering. The main reason for the difference is due to the different design goals between front and rear suspension, whereas suspension is usually symmetrical between the left and right of the vehicle.

Anti-dive and anti-squat percentage are always calculated with respect to a vertical plane that intersects the vehicle's center of gravity. Consider anti-dive first. Locate the front instant centers of the suspension from the vehicle's side view. Draw a line from the tire contact patch through the instant center, this is the tire force vector. Now draw a line straight down from the vehicle's center of gravity. The anti-dive is the ratio between the height of where the tire force vector crosses the center of gravity plane expressed as a percentage. An anti-dive ratio of 50% would mean the force vector under braking crosses half way between the ground and the center of gravity.

Anti-squat is the counterpart to anti-dive and is for the rear suspension under acceleration.

Anti-dive and anti-squat may or may not be desirable depending on the suspension design. Independent suspension using multiple control arms can be an issue if the percentage is too high (say over 30%). A percentage of 100% in this case would indicate the suspension is taking 100% of the weight transfer under braking instead of the springs. This effectively binds the suspension and turns the independent suspension into no suspension like a go-cart. However, in the case of leaf spring rear suspension the anti-squat can often exceed 100% (meaning the rear may actually raise under acceleration) yet because there isn't a second arm to bind against and the suspension can freely move. Traction bars are often added to drag racing cars with rear leaf springs to increase the anti-squat to its maximum. This has the effect of forcing the rear of the car in the air and the tires onto the ground for better traction

Awesome explanation, and thanks for taking the time to do that. How do you come up with a measurement like "144%" though? Do you go by photos, and draw some lines on them?

[Alan Warman]

Kenny
What back spacing do you have on your new wheel's.

BlueOval
Thanks for the post there's a lot of info there.

Greg
What back spacing do you run.

Tony
I did not no Alf Weibe made a kit for the G-Body. The shocks I have now are a worn out Koni's. The adjustment does not work anymore. Thanking about Afco's.

Jeff
I drew mine out on paper. But you can go to a hobby supply store and buy poster board, and you can drew it out full scale. Also there are programs you can buy. Just plug in the numbers and it does the rest. Go to yellowbullet.com they talk about it all the time.

Thanks for all the input guy's not only did you help me. But you help Jeff also.

Here is a picture of the car at Dallas

[Dennis Paz]

Anyone have any idea how much a typical bias tire grows compared to a radial?
Alan
I am a little new at this class stuff but my ss/ma car dont care if I leave at 7000 or 5ooo with the radial it will not spin either way and will 60 the same.

[BlueOval Ralph]

I am not that smart I just Web Search - powered by Google it and thats what came up it is amazing the info on the InterNet
Ralph



Ia

Originally Posted by mopar jeff

Awesome explanation, and thanks for taking the time to do that. How do you come up with a measurement like "144%" though? Do you go by photos, and draw some lines on them?