Thread: Spring rates or specs

Originally Posted by Rangier Rover

Guess mine will soon work on LBS per cubic ft

Pressure = Force / Area.?


Be interesting to calculate it out.
Air pressure in a given area = X force to hold the vehicle at a given ride height. There for I should be able to calculate the weight of a given load by using the air pressure.

Gas spring rates are a bugger to work out as the spring has a rising rate as it's compressed.

Saw some numbers years ago in one of my race car references, probably Race Car Engineering where Ken Anderson (a damper/suspension guru, ex Penske, F1, etc) discussed the difficulties and had some numbers and it looked a little complicated

Originally Posted by rick130

Gas spring rates are a bugger to work out as the spring has a rising rate as it's compressed.

Saw some numbers years ago in one of my race car references, probably Race Car Engineering where Ken Anderson (a damper/suspension guru, ex Penske, F1, etc) discussed the difficulties and had some numbers and it looked a little complicated

I hear you on that.

We have some very clever people here, so one will come up with the formula needed Probably wont be me.

I could partly solve it with trial and error. Put a ton on then see how much pressure it takes to get it back to the normal ride height?

Originally Posted by Rangier Rover

I hear you on that.

We have some very clever people here, so one will come up with the formula needed Probably wont be me.

I could partly solve it with trial and error. Put a ton on then see how much pressure it takes to get it back to the normal ride height?

Here is the Firestone Air spring design manual:
www.firestoneindustrial.com/pdfs/OE/AirideDG.pdf (8.3 MB !!)
It has all the equations you need. Page 25 has a sample static load deflection graph. However it would be easiest to get the data sheet for your specific air spring(s) from firestone.

(Thanks to Bush65 for telling me about the design manual and where to find it)

Thanks Ben, I'll download that one when I retire for the evening

That's if the connection doesn't do it's usual bundy off routine

I have finally got around to fitting the springs and taking measurements on ingoing and outgoing springs.

Dobinson - outgoing
Guard top hgt 1175mm front 1225 rear
Bump stop 100mm front 145mm rear
wire diameter 17mm front 19mm rear
free standing hgt 417mm FPS 430mm rear
425mm FDS

130 springs - ingoing
Guard top hgt 1135mm front 1155mm rear
Bump stop gap 55mm front 115 mm rear
wire diameter 16mm 19.5 rear
free standing hgt 385mm FPS 410 RDS
395 FDS 400 RPS

For further comparison the project 110 has guard top hgt of 1135mm front and 1185mm rear, and bump stop gap of 63mm front and 115 rear.

Hi All

All this spring talk made me want to get out doors and do something so I went and measured the 120 to see what I had and so I measured the spring stop gaps.

I measured the rear axle to bump stop gap with ome springs and nitrocharger shocks and they measure out at 180 mm and the front measured at the rear of the front axle - minimum gap as the axle pad isnt level is 37 mm.

So i'm guessing i need about a 115mm lift at least and as I have a steel bar and highmount, winch spotties and snorkel then it's not the lightest landy in the front end either

Anyone got any ideas or suggestions for me that doesn't involve me giving it to them

Regards Mark

Originally Posted by rar110

I called a spring manufacturer about springs for the 110. I used the army parts book to describe the original springs and they calculated the rates as 220 pounds front and 240 pounds rear. The inf on the net seems to indicate the same rated springs are fitted to later tdi 130 s. The isuzu motor is about 120 kg heavier.

So the question is can 130 tdi springs be fitted to an isuzu 110.

Thanks.

What did you end up using?

Originally Posted by rfurzer

What did you end up using?

The same used 130 springs are still fitted.