F5000 spring rates

[tige00]

Anybody out there know what spring rates f5000 cars used, specifically the rear. Thanks

[kea]

The Surtees TS-5A in the shop has run #400 rear springs.
I remember changing the Chevron B24 springs (mid 70's) to #500

[tige00]

Thankyou very much, any reason for such soft springs.

[S Lathrop]

Given the power that you have with a F5000, I would suggest that you concentrate on what the wheel rate of the springs you choose should be.

To do that you will need to know how much weight will be supported by that spring, The sprung weight of the car on a corner. Then you need to know how far the spring moves when the wheel moves 1 inch, the motion ratio of the spring and shock. Motion ratios are unique to each car and to the front and rear of that car as well.

Say the motion ratio of you car is .6. that means that it you move the wheel 1 inch the spring will move 0.6 inches. If that is the case, the wheel rate for a 400 pound spring will be 144 pounds per inch. Will that be enough to support a corner of a car that might be close to 1500 pounds? That would be 1500/4 = 375 per corner. Then take the un-sprung weight of the tire, wheel, brakes and upright at say 50 pounds. That leaves an average sprung weight per corner of 315 pounds supported by a wheel rate for the spring of 144 pounds per inch.

Now, if the motion ratio is close to 1:1 then that spring might work great.

[kea]

Will that be enough to support a corner of a car that might be close to 1500 pounds? .

Steve,
No corner of the car weights 1500 lbs. The whole car maybe.
Remember, springs rates I've given are for old cars, in some case, not adjusted for modern replacement tires.

[E1pix]

Thanks Steve for presenting dynamics a guy like me really learns from.

I imagine the weight bias of a 5000 car to be maybe 40% front and 60% rear. This is totally a guess, but helps make sense of your 400# rear corner comment on a 1,500 lb. car.

I’ve noticed when corner-weighting our karts (and when weighing corners on our car to balance it better side-to-side) that say a total front weight is always less than adding the two corners. I’ve seen the same when weighing sides.

I have some theories on why this is, but am not sure and I’m all ears... plus my library is a thousand miles away (Tune to Win reference, for one).

Thanks.

[S Lathrop]

Steve,
No corner of the car weights 1500 lbs. The whole car maybe.
Remember, springs rates I've given are for old cars, in some case, not adjusted for modern replacement tires.

I should have been more precise. Now read my edit of that post.

[kea]

Steve, Yep, that reads easier.

[tige00]

Thankyou to all who answered, helps me out tremendously.

[johnhafkenschiel]

Thankyou to all who answered, helps me out tremendously.

Is there a specific car you are trying to set up (like March 732-15)? I would think the period set up of the fastest prior owner would be a good starting point.

[tige00]

Yes and I agree thankyou