How do I determine Shock Stiffness for my ATV?

[Thoran]

I'm in the proccess of drawing up plans for my first go-cart(off road).
I'm planning on making it a full suspension cart.
I have many questions, but I'll start off with some easy ones. At least I think they'll be easy.
The shocks I have been looking at list there total load capacities.
How do I determin the proper shocks for my cart?
One shock each on front, dual shocks on back, total of 4.
At this time I don't know the total wieght that my cart will be.
Thanks for any wisdom you can pass my way. :thumbup:

[mancoowner]

dont u mean total of 6? one on each corner of the front and two on each corner on the back makes six. anyways, make sure they will flex well, not be fully compressed when the axle [or whatever is going to be on the front] moves just a few inches, make sure it has plenty of travel. then just make sure the shocks will hold about 100-200 pounds more than the weight of the go-kart and riders. thats my $.02 :gmorning:

[Thoran]

I might have typed it wrong. When I said dual shocks on back, I meant that there will be two shocks on the back, one on each side. I have seen carts with just one large shock on the back.
Anyway, thanks for your input.

[Thoran]

If I have a shock that is listed as (3" comp. 730lbs total load), I asume that if you placed 730lbs on it, it would compress 3".
Now if I have the same 730lbs, but 4 shocks. Each shock should be carrying 182.5lbs, and compress only about 3/4", leaving 2 1/4" of travel.
I am about 160lbs, and if my cart is about 570lbs, I should have 2 1/4" travel on each shock. So my goal should be, with these shocks, to keep my cart under 570lbs. Does this sound correct? :thumbup: :thumbdn: :eek:

[nasimuto]

you have to leave a 'safe zone'
e.g when you are jumping with your kart (which is not an atv btw) and it lands, the suspension is given an instant load equal to the 10x weight of you and the kart.

that load can break just about anything

of course, u cant have 7000 lbs shocks :P
the good thing is that the 10x force is applied when it hits a certain acceleration during landing - that needs alot of altitude.
so.. instead plan a 1,2x to 2x 'safe zone' (how much are you gonna play stunts with it ?), a 1,2x safe zone allows the suspension to be given a load equal to 700lbs from the altitude of about 40" (1 metre)

i hope this made sence :D

[Thoran]

Basically, I will try to keep the weight down as much as possible.
If the cart gets up in the 450-500lbs I will try to find stronger shocks.
I don't plan on doing anything really wild with my cart.
If I have to, I can make it dual shocks, instead of single.
Thanks :)