# Race car suspension Class

by Ranger Mike
Tags: class, race, suspension
 Sci Advisor PF Gold P: 1,462 Thanks John..means a lot when we get reports from the other side of the world...and I was the guy who thought the internet was a FAD... we went thru this on page 26 of this forum with a fellow running a drawf car...wider is better in that you have more cornering ability in that for a given set up you will transfer less weight and the tires can better accommodate the weight that is transferred. Also the Left rear to right front leverage is improved slightly...and thus side bite off the turn with a tad more wedge..read the whole page as we had a good debate on this... General Rule of thumb - 1 inch lower COG transfers 3 to 4 % less weight. 1 inch wider car transfers 1 to 1 1/2 % less weight. Assume we have a race car with 66 inch wide rear track and we add 100 weight to the ballast and we locate this weight 20 inch from the center line of the left rear tire. 20" divided by 66" = 37% of the added weight will go to the right and 63 % will go to the left side of the car ( diagonal weight is not in this calculation). Now if we increase the track width on t he left side by one inch we have 21" divided by 67" = 31% right side weight and 68 % left side weight. (from Short track chassis set up by Duke Southard) Attached Thumbnails
 P: 41 Ranger mike: What do you feel is more important On dirt oval? Getting shocks to work perfectly with spring rate for each corner of the car or Using dampening to control weight transfer. This is to settle argument. I feel like proper spring selection should be used to control weight transfer and dampening should be used to control that particular spring
 P: 41 To specify: Using front tie down shocks and a lr with stiff bump and light rebound.
 Sci Advisor PF Gold P: 1,462 The purpose of a shock is to dampen the kinetic energy stored in the spring during weight transfer. Specifically the shock converts this vertical energy to heat energy by creating resistance to movement within the shock. Shocks control the RATE of weight transferred during cornering. Shocks have nothing to do with the amount of weight transferred during cornering. They can affect how quickly the weight is transferred. So using shocks dampening to control weight transfer is not exactly correct. Using the dampening to control the RATE of weight transfer is correct. The amount of weight transferred is dependent on the center of gravity, roll axis and roll rates. Where the weight is transferred is dependent on the spring rates. How quickly this weight is transferred is controlled by the shocks. So Thorpe, you are a little closer to the true purpose of the shock than the other fellow..my opinion. And you are right on with the tie down scenario in that you are tuning the chassis regarding rate of transfer after you get the spring rate real close to perfect!
 P: 41 Thanks for the info. We just agreed to disagree lol. What I'm looking for this weekend is s small bit of tire loading control by change in transfer rate. On a med bank track with decent grip. I plan to run: Rf lf Soft. Lr 2 rates higher than front. Rr one rate up from front. Then stiffer bump and rebound in both lf and lr. From what I understand stiffer lf bump and lr rebound unloads lr tire load sooner on entry and takes cross weight out. Then stiffer lf and lr bump adds cross weight on exit. My hope is to be slightly loose entry and slightly tight off witch fits my driving style.
 P: 41 Btw this spring setup has been very close with equal dampening all 4 corners
 Sci Advisor PF Gold P: 1,462 All things are relative so i would make small changes like when you are on on a wet tacky or very tight track you want to loosen the chassis up on corner entry. Use a tie down shock on the Left front. This lets the left ft. drop down easily at corner entry and takes weight off the RR tire. This makes the car pivot around the Left Ft which makes it easier to steer in the the corner. The tie down shock delays weight transfers off the lefty front. In the middle of the corner when the chassis is transferring weight to the RR., it keeps the LF tied down to prevent a quick weight transfer to t he right rear. A stiffer LR shock with stiffer rebound holds the weight on the LR longer at corner entry not allowing as quick a transfer to the RT FT tire.
 P: 41 Ok I see where you are going with this and it makes sense. Thank you for your time. I got off track a little after reading this article about initial weight transitions. http://www.circletrack.com/chassiste...g_your_shocks/
P: 41
 Quote by Ranger Mike All things are relative so i would make small changes like when you are on on a wet tacky or very tight track you want to loosen the chassis up on corner entry. Use a tie down shock on the Left front. This lets the left ft. drop down easily at corner entry and takes weight off the RR tire. This makes the car pivot around the Left Ft which makes it easier to steer in the the corner. The tie down shock delays weight transfers off the lefty front. In the middle of the corner when the chassis is transferring weight to the RR., it keeps the LF tied down to prevent a quick weight transfer to t he right rear. A stiffer LR shock with stiffer rebound holds the weight on the LR longer at corner entry not allowing as quick a transfer to the RT FT tire.
I did exactly this ^^^^ yesterday for practice and absolutely love it.

Also found a problem I've been fighting for while now. My upper links.
When I drew out the geometry I must have misinterpreted something and had the inner links higher. Thought I was lowering my rc but instead had raised it.

Made the swap real quick to lower them and WOW. All I can say. It was that great. Finally made everything I've been working towards come together for a great setup.

Thank you for your knowledge you are willing to share on here I know it has helped me tremendously
 Sci Advisor PF Gold P: 1,462 Thanks for the kind words..Ifin we were racing each other on the same track I doubt I would be as Christian...seriously I appreciate it. I hope everyone realizes I have sourced some pretty good books and if everyone bought these, they would we able to figure things out..all I do is save a little time in the process and hopefully do not impart BAD advice that screws up some ones good set up...Like Jimmy Johnson just demonstrated, you have to FINISH to win. So this winter is the time to check and inspect every nut and bolt on the car. When in doubt ,,replace it!