Billboard Alignment Specs

[Sminor]

I recently mounted "Billboards" on my Roadster. They look great, but have most of the "bad" traits mentioned in previous threads (darting, hunting, wandering, ect). I did a forum search, and while the importance of proper alignment was mentioned several times, no one specified what the alignment numbers should be. I have had my car aligned using the numbers supplied in my manual, but I'm having no luck thus far in getting good handling out of these tires. The higher the speed, the more excitement ( not in a good way). And forget smooth roads, I live in West Virginia. If you have had success getting your Cobra to handle well with these tires, please post your alignment specs and advice. I have a Mustang II tubular front suspension and a Ford 9" rear with 4 link.
steve

[Silverback51]

Alignment specifications are related to a car, not the tires.

Now with that said, for the SPF they recommend 1/4 degree negative camber for the street, and up to 3/4 degree for track use. I run 3/4 on the street, and that was what I was running with my BB's.

Also, what tire pressures are you running?

[Sminor]

John,
29psi fronts, 26 psi rear. I have read in other posts that air pressure is critical for these tires relative to the balance of the car. I haven't found anyone in my area with corner scales......I may have to buy some and go from there. What are your thoughts?
steve

[mickmate]

I have found tire pressures about 20 work well. The tires balloon with too much pressure as they are so wide. The other thing is the toe in and wheelbase are even from side to side on the car. In other words make the wheels square to the frame. The biggest difference I found for the hunting and darting is to give it plenty of caster in the 4-5 range. It makes the steering a little heavy at low and parking speeds but I like the results on the cars stability.

[Silverback51]

I ran 20psi front and 18psi rear, and I'm guessing my car is heavier than yours. Try playing with the tire pressures and see if they make a difference.

Corner scales are expensive. Try to find a race shop in your area to see if they have a set and are willing to set your car up for you.

[strictlypersonl]

Going to the high end of your toe-in spec will help stability.

[Sminor]

Thanks guys. I really appreciate your advice and will experiment with your offerings. I'll let you know what happens.
steve

[jmimac351]

As I recall I ran about 22psi in mine. Look at the tread to see whether it's all contacting the ground. They will plump up in the middle of the tread with too much pressure, as mentioned. I was careful to square the rear end in the chassis, as mentioned. I also ran minimal camber... less than 1/2 degree. Pretty sure I ran about 1/8 toe in, caster was about 4.5 - 5. Toe and camber ideas came from searching around and reading guys talk about bias ply tire settings. "They don't like camber." The caster wasn't as heavy as I expected with manual steering given the width of the front tire (was running a 275 width front tire previously).

I would have played with more suspension settings if it was easier to adjust the rear, and if I hadn't sold the car. Making the rear arms more easily adjustable is on the list for the new car.

Jim

[jmimac351]

Also, 3 other buddies and I bought in to a set of scales. That's a good way to do it and have access to scales whenever you need them for a couple hundred bucks.