Weights for calculating spring rates

[toughnut]

As the title says. I'm trying to get some weights to help me calculate the spring rates for my truck. I won't be able to get acurate data until the truck is finished, however; There are lots of other trucks out there that are similar to what I am building and I'm just trying to get a feel for what I need to start with.

So. Could someone either give me some good baseline spring rates to start with or could someone please give me some basic weights like sprung weight of each corner. I've done some basic estimates below.

I'm building up a mid wheel base GU ute with 14inch shocks for the front and 16 for the rear. I'm guessing a total weight of 2200kg and a split of about 55% front and 45% rear. So that is 1210kg front and 990kg rear. Does this sound about right? I'm using the FOA calculator at the moment. Are there other calculators that are better. I'm only after a basic setup to start with. I'll fine tune with other springs once the rig is fully built.

If you have info but don't want to plater it all over the board then please PM me.

Cheers
Steve

[brooksy]

If you want to get as close as possible read the Billavista write up on Pirate which goes into Installation Rate & Wheel Ratio which is important with regard to shock angle then goes further into frequency etc.
The FOA is just a guide & leaves too many variables wide open.
It is a big read but well worth it.

http://www.pirate4x4.com/tech/billavist ... rs/Part_1/" onclick="window.open(this.href);return false;




brooksy

[bazooked]

you should be able to hire corner scales from race shops, don't know which ones you got over your way!, as for calculators go the eibach one, seems to be the best around.

[toughnut]

you should be able to hire corner scales from race shops, don't know which ones you got over your way!, as for calculators go the eibach one, seems to be the best around.

Cheers for that. Problem is that I'm at work in China for the next 5 weeks and they needed an answer today so they could send my order. The springs I have now probably won't be the ones I run unless I've jagged it for some reason. They will be used more for the fabrication setup and to allow me to have a rolling chassis etc. Once the truck is fully built then I'll weigh it properly and set it up correctly. I just wanted to get something that was close within reason.

For info, I've gone with:
Front:
300 lbs/in main
200 lbs/in tender

Rear:
200 lbs/in main
150 lbs/in tender

This will be enough until I complete the build and do some proper calcs. Its just hard to do it by remote from here in China.

[MikeH]

Complete the car with the springs you have.
Bastardize those springs for the ride height you want. (spacers or cutting coils off)
then weigh it at ride height when complete.
then order the springs.

Or guesstimate as close as you can, then weigh it when almost complete and position the heavy items to fine tune, it depends how close you want to get.

[bru21]

why use springs? cut some tube and fit it where the springs are, or some 35mm rhs where the shocks go

[toughnut]

why use springs? cut some tube and fit it where the springs are, or some 35mm rhs where the shocks go

The springs were free with the shocks and they wouldn't send them without springs. Not sure why but would have been a hold up if I delayed giving them some spring rates. As for substituting the shocks with other stuff. This is the first time I've set up a truck for coilovers and bypass shocks so I'd prefer to have them sitting in front of me to make sure they don't bind on anything.

[evanstaniland]

When I got coilovers for my bundy, I ended up going
Front - 250 load 150 tender
Rear - 200 load 100 tender

Mine is around 1900kg give or take.
Don't know how they sat, I never ran them

[toughnut]

When I got coilovers for my bundy, I ended up going
Front - 250 load 150 tender
Rear - 200 load 100 tender

Mine is around 1900kg give or take.
Don't know how they sat, I never ran them

Mine should be pretty close then. The patrol is heavier than a bundy and the winche or winches will be mounted at the rear.

[brooksy]

Don't forget it is "Sprung Weight" not total vehicle weight.
A Suzuki Diff & a Rockwell Diff will give 2 different total vehicle weight but coil rates would be similar although valving, frequency, oil displacement would differ requiring bigger shocks but with similar coil rates



brooksy

[evanstaniland]

True, I put my truck on corner scales b4 i got mine

[toughnut]

yeah. Its not going to be a light truck when its loaded up so 2200kg is probably pretty close without unsprung weight.

[MikeH]

why use springs? cut some tube and fit it where the springs are, or some 35mm rhs where the shocks go

because there needs to be some compliance in the system which is why I'd fit the springs, but I forgot about the tyres... so yes that should work with sensible tyre pressures.
It would be easy to get your unsprung weight too, weigh the corner, then jack the body up until your "spring" block isn't touching any more with the scales still under the wheel.