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Got out on track this weekend with my new tire and brake set up. Not my best weekend. As a base set up, I changed nothing from my radial set up, just bolted on the Hoosiers and went.
First note was that braking was terrifying, car darted from side to side under heavy braking and the car was very loose. After talking with some guys at the track I learned bias ply tires like really low pressure. Session 2 started with lower pressure, 20 psi. Handling improved.. Still loose, still twitchy under braking, but better. Was told that I needed to shoot for 25 psi hot, so reduced cold pressure to 17. Handling improved a bit more, then I flat spotted a tire. Not one to give up, I tolerated the vibration from the flat spotted tire and got 1 more bit of advice, try alignment change to slight toe out. Made the change and could not tell a big difference at this point. Car was still very loose. I have a watts link and a 3 link suspension, tubular upper A arms with +3 caster built in and camber is at -2.5. Tire temps seemed to be fairly consistent across the tire after a few laps.

I think I need to lower the roll center of the watts to help with the oversteer. If you run bias ply tires let me know what you think.. Thanks
 

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I never ran bias tires. I'll say that right off the bat.
I will tell you this, the caster you would need to run has got to be different because
the two tire designs are different. Caster trail......

There are undoubtedly other differences. The tire contact patch I guarantee is different.
An alignment guy I am not. Maybe one of them will comment.

ex-Global West GM
1991-1995
 

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As I was reading, I was laughing. Yes the bias tires are VERY different than radials. It’s like trying to drive flat out on ice. Yes the car “dances” all over the track. Watch some in-car vintage races and you’ll see the hands always moving!

My current setup (which is awesome) is:
+2.5 caster
-2.75 camber
1/16” toe in
PHB is set level
6.00-15 Blue Streaks. Cold starting temps are usually 23 F, 22R. Adjust 1psi up if cold air temp and 1-2psi down for warm/hot temps.

Hoosiers run different pressures.


Mark
 

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Spammer Hammer
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My setup is similar to Mark’s with the GY BS’s. I don’t have a PHB, and I’m still learning to slide, but it comes pretty quick...at least it better.

Caster: +3.5
Camber: -3
Toe: 1/16” In.
 

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Spammer Hammer
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Check that. I think that was my caster prior to changing to blue streaks. I think I’m at 2.75-3 on caster now.
 

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Spammer Hammer
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Relative to GT289 and tire contact, I can say the front tire temps at my last event were almost dead even all the way across after every session. To me, that says the alignment is pretty darn good.
 

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A long time ago there was a member here who did a lot of road racing with his 66, Dinosawnj. He lived close to me. What he told me about bias and radial tires was that radial tires tend to run egg shape like you would see in cartoons. He told me radial tires needed more caster.
 

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Camber needs are also different. I've never run bias ply tires, but I think they like less camber than radials? I guess a quick Google would answer that question !
 
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