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Planning to start racing in the Vintage series - VDCA. I have a Royale RP 31 and I am looking for set up help. Going to run Hoosier Vintage treaded tires. Need help with ride height, spring rate(rocker ratios are 1.5:1 in front & 1:1 in rear), tow and camber, cold starting tire pressure.
Any help is greatly appreciated! Thanks!
Mark
Search the forum for info on tire pressures for the Hoosiers. There are a few different opinions here. Chassis shouldn't make that much of difference.
Jake King has been running a Royale in CF on bias ply slicks. He may also have some guidance on setup for vintage tires.
I’m going through the same process with my RP31, but with Avons. I didn’t like the Hoosiers on my RP16 and the Avons feel more predictable.
the rocker ratio (wheel rate) on the front is 1.66:1 and the rear is close to 1:1 but does have some reduction.I found out that there were 2 distinct versions of the rear suspension - one for the US market (smaller diameter slicks) and the UK market (taller treaded tires) the inboard upper suspension pickup point is 3/4” higher for treads than the slicks. Camber climb is quite steep if you use the lower pick up.
my plan is to run pressures at the same I used on my RP16 and go from there. With Avons I liked 13.5 F/15 R… with Hoosiers I always started at 15 F/15.5 R. I’m also going to run this car much lower and stiffer than my older car. I don’t have the specifics yet, but I can post when I discuss with my shop.
id love to see some photos of your car, PM me so we can chat offline. You probably know I’m modeling up this chassis to see what suspension movements do to camber/caster, etc… I’m also using it to show my shop what modifications I want to do to the chassis.
https://www.apexspeed.com/forums/att...d=105772&stc=1
Mark,
You will find that the wheel rate "operating window" for the Hoosier VFF tires is between 35% and 85% of the corner weights. Where in that operating window is dependent on a number of factors including chassis stiffness, roll axis height and how stiff a car you like. I usually start with spring rates that get my wheel rates to approx. 50-55% of the corner weights. Assuming you start with 50% and assuming your corner weights (with a driver) are 330# rear and 225# front you would use spring rates as follows:
Front Wheel Rate = Spring Rate / (Motion Ratio) squared
Front Wheel Rate = 250/ (1.5) squared = 111
Front Spring % = Wheel Rate/Corner Weight
Front Spring % = 111/225 = 49.3 %
Rear Wheel Rate = Spring Rate / (Motion Ratio) squared
Rear Wheel Rate = 200/ (1.1) squared = 165
Rear Spring % = Wheel Rate/Corner Weight
Rear Spring % = 165/330 = 50.0%
For ride height I will typically start with the rear lower A arms horizontal and a 1/4" rake. Ride height will be somewhat dependent on your spring rates and the car/driver weight. I would guess you will be about 2.25" rear and 2" front. I usually set the front and rear anti-roll bars at half way and adjust the handling with changes in rear ride height (rake).
For toe I usually start with 1/16" out per wheel (1/8" total) out front and 1/16" per wheel (1/8" total) in rear. Make sure your bump steer is as close to zero as you can get it. Also make sure your caster is the same side to side in the front. I generally use 3-3.5 deg.
Camber settings on Hoosier VFF is much more upright then some other VFF tires. I would start with 1/2 deg. neg. front and 1/4 deg. neg. rear. I would check tire temps or tire wear for final settings.
I have found the optimal tire temps on Hoosier VFF tires are also different then other VFF tires. They seem to work best between 16 and 17 psi HOT. There are a number of factors that will effect your cold settings including toe, how you set-up your car to handle, track temps and wet vs. dry conditions. I have set my COLD tire temps as low as 12 psi on hot days. and as high as 15 psi on cold or damp days to get my desired 16.5 psi hot.
Will you be at The VDCA Roebling Road event in Feb? If so, I look forward to meeting you.
Good luck with the car, Joe
Rear wheel rate looks wrong. I think the rate is higher…
I think the math works better if you use 200 spring
Yes, you are correct. My bad. I got my math wrong. I multiplied by 2 instead of squaring the motion ratio.Quote:
Originally Posted by scorp997
It is now corrected.
BTW, If the front motion ratio is actually 1.66 instead of 1.5 you will need a 300 lb spring in the front to obtain approx. 50% of the corner weight.
Thanks guys for your input! Joe I won't have the car done for the Feb race. I also have to get my license reinstated so I am planning on going to the driving school at Roebling Road on FEB 24-26 . Will have to figure out my racing after that .
Thanks,
Mark
Great information. This should get put on the FFCS Website!
Robby Bork
Quote:
Originally Posted by pooch776