Thread: HELP in Determining the correct Spring Rates for my Defenders...

Would these weights be close to the mark:

• Rover Front Diff & Housing - 130kgs
• Salisbury Rear Diff & Housing - 125kgs

Does that sound about right?

Took both Defenders to a mates workplace to weigh axle loads over the front and rear of both Defenders results as per attached photos

Looks like I may need to look into a GVM upgrade if it is even possible. A mate informed that I could look at the Qld LS11 upgrade... I don't know much about it so will have to do some research into it


BTW: Does anyone the FRONT and REAR AXLE load ratings on both the 110 Tdi300 and the PUMA models?

Thanks in advance

Given you know the spring rates, you can compare the spring free length against the spring installed length and it will give you the vehicle weight.

You also have spacers, so you know that the free lengths for a given spring rate need to be increased by the spacer thickness to level the ride heights with all else being unchanged.

There also isn't a "correct" spring rate for the weight of the vehicle.

Originally Posted by Slunnie

Given you know the spring rates, you can compare the spring free length against the spring installed length and it will give you the vehicle weight.

You also have spacers, so you know that the free lengths for a given spring rate need to be increased by the spacer thickness to level the ride heights with all else being unchanged.

There also isn't a "correct" spring rate for the weight of the vehicle.

Thanks... I'm also assuming that I need to take off the weights of the unsprung weight (Diff & Tyres) from the weights I recorded and then work out spring rates from there... Would this correct?

Originally Posted by Robmacca

Thanks... I'm also assuming that I need to take off the weights of the unsprung weight (Diff & Tyres) from the weights I recorded and then work out spring rates from there... Would this correct?

No, this will give you the sprung weight only. The unsprung weight.... well, its unsprung so doesn't form any part of the calculation if doing it that way.

For your new spring rates, you can calculate then how much they will compress with your vehicle corner weights and you know what installed length you want, so you can calculate from that the spring free length required. Your springs will settle a little in the first year also, I think even scragged springs do this.

Originally Posted by Slunnie

No, this will give you the sprung weight only. The unsprung weight.... well, its unsprung so doesn't form any part of the calculation if doing it that way.

For your new spring rates, you can calculate then how much they will compress with your vehicle corner weights and you know what installed length you want, so you can calculate from that the spring free length required. Your springs will settle a little in the first year also, I think even scragged springs do this.

Correct, but unfortunately each corner weight I got also includes the un-sprung weight of the Wheels & Diffs. I need to take these weights off accordingly to get the real Sprung weight of the 4 corners. From what I've found on the Web, the Salisbury Rear Diff is 125kgs and the Front Rover Diff is about 130kgs, so I need to work out how these weights are distributed over the RHS and LHS of the car. Because the Diff Pumpkin is not central, I reckon somewhere between a 70/30 or even a 60/40 split in weight from the RHS to the LHS should be roughly right... I think

What I'm saying is that if you calculate the weights from the spring installed length vs spring free lengths, given you know the spring rates, the weights that you come up with will be the sprung weight of the vehicle.

Originally Posted by Slunnie

What I'm saying is that if you calculate the weights from the spring installed length vs spring free lengths, given you know the spring rates, the weights that you come up with will be the sprung weight of the vehicle.

Yes, I've done that but my concern in doing this is if the spring has sagged due to age that the calculation may not give me a correct figure...