Hi guys,
I am currently doing a personal project and will like to know what spring rate for bumpy street track do you use?
Thank you
PK
Street track spring rate
Hi guys,
I am currently doing a personal project and will like to know what spring rate for bumpy street track do you use?
Thank you
PK
Long beach is a good example
thx
Long Beach is a good example
thx
Hi,
Any help there?
Thank you
I have run a lot of cars at Long Beach over the decades, Formula Atlantics and Indy Lights. I did not make a big spring change because that track was a bit rough. But those cars have a lot of down force and controlling ride height is very critical.
Giving you a number for a spring rate would make no sense because I have no idea about you car.
What you need to post is the corner weight for the front and rear of the car fully loaded. And you need to post the motion ratio for the front and rear of the car.
As a starting point I would suggest a spring rate that gives you a wheel rate that is the same as the load on that corner. So if your car was 300 pounds on each front corner, you would use a spring that gave you a 300 pound per inch wheel rate. If the shock moves .6 inch per inch of wheel travel, Then you would need something like a 800 pound spring. If you want to be more exacting, you would take the spring rate of the tire into account.
You might go for a wheel rate of 250 pounds per inch on a 300 pound corner but that may create issues of keeping the car out of the ground or the suspension geometry might not work well with a big increase in ride height. Also you should consider using bump stops at both ends of the car to keep the car out of the ground.
This is great S Lathrop!!!
I have read a lot of treads about this but only on race tracks
And wanted to know about street track
What ride height you used? This will work for me as a reference
I appreciate it very much!
Thank you
P.k.
There is a manual with recommended setups published for your car. Use that for your starting point. The designer of the car laid out the suspension to operate in a certain range. That mainly means ride height. Say the recommended ride height is 1.5 inches front and 2 rear. You might be able to change that by 1/2 inch plus or minus. That range is probably the absolute maximum.Originally Posted by pedrok
But without knowing what the suspension geometry actually is, I would not have a clue for a ride height.
A second point is that all cars are designed around a specific tire. Here again the tire dimensions are critical. If the front tire was 22 inch diameter and the rear 23, you absolutely have to be using tires very close to those numbers. Again the suspension geometry determines what you can and can not do.
As an example, the Zink Z10 FF was designed around 22" front and 23" rear tires. The ride heights were 2.5 front and 3 rear. This was common for cars of the '70s. Interestingly, that car can run at ride front ride heights between 1 and 1.5 front or anything over 2. But ride heights between 1.5 and 2 make the car prone to loosing traction at the front in certain circumstances. But there are tire diameters and ride height combinations that work very well and are quite different from the original design parameters.
The other absolute given is that the lower you can run the car, the lower the Center of Gravity will be and corresponding the higher the mechanical grip potential the car has.
In short you need to do a lot of home work to answer the questions you have. Formula cars, because they are light and very quick responding, can be sweet harts or monsters to drive and you job is to find the sweetest spot for you car's setup.
'Street track' means nothing. What is relevant is the track surface condition. Generally speaking you have limited knowledge until you actually start racing on that surface. You are going to have to make some judgments based on visual observations before racing starts.
Your goal generally would be to have a 'light' bottoming situation somewhere on the the track. Something that is not going to damage the car over the length of the event.
I remember Long Beach having a dip that had to be repair over night. While the rest of the track could have been billiard table smooth that dip pretty much control setup decisions before the dip was prepared.
Brian
S Lathrop
Awesome!
I'm desining it from scratch something like the bac mono or a FA with a 2L 300hp engine, 1 to 1ratio rocker arms, FA 13" tires (maybe pro formula Mazda tires), running it on a track & street real bumpy track, probably 1400lb car plus me & 15 gal gas 335lb total 1775 lbs front 45% 800/2 =400 each corner, rear 500, as a start will use the same spring rate as corner weight
Having a ride height of 1.5", there will be 1" static travel (then will need 2.5" shock travel) with spring preload can be shorten, what is a good start for static travel?
Thank you
P.K.
Last edited by pedrok; 10.22.16 at 1:22 PM.
Hey Brian,
Thank you for sharing your knowledge!
P.K.
Last edited by pedrok; 10.22.16 at 4:47 PM.
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