Thread: Front Springs

Originally Posted by gwac110

I had those springs fitted to mine nrc9448/9449 with nothing extra up front and the ride was good but they made the front level with the rear (with the rear empty) so any weight in the back it didn't look right.
I'm now using nrc8044 springs which are standard defender front springs and it has lowered the front and looks right but they are too soft, you don't have to hit much of a hole to hit the bump stops!
I need to find a middle ground spring, standard height but not too soft and I'm struggling!

You've got 2 reference points, and known spring rates (see link I posted earlier), so pretty easy to work out what rate and free length you need and then select a spring that matches.

Steve

Originally Posted by gwac110

I had those springs fitted to mine nrc9448/9449 with nothing extra up front and the ride was good but they made the front level with the rear (with the rear empty) so any weight in the back it didn't look right.
I'm now using nrc8044 springs which are standard defender front springs and it has lowered the front and looks right but they are too soft, you don't have to hit much of a hole to hit the bump stops!
I need to find a middle ground spring, standard height but not too soft and I'm struggling!

With linear spring rates some simple calcs will give you an idea of what to expect. The NRC8044 are progressive rate springs and the following procedure is not suitable for them.

If you measured the ride height of the NRC9448 it would be even easier.

Since you don't have the ride height, I'll assume minimum and maximum spring loads of 1200 lbf (544 kg) and 1600 lbf (726 kg)

According to my information, the NRC 9448 has a spring rate of 225.09 lbf/in and a free length of 15.3"

So with the assumed minimum spring load of 1200 lbf the spring will compress:

compression = 1200 lbf / 225.09 lbf/in
i.e. 5.33"

This will give a ride height of 15.3" - 5.33" = 9.97"

With the assumed maximum spring load of 1600 lbf the spring will compress:

compression = 1600 lbf / 225.09 lbf/in = 7.11"

and ride height = 15.3" - 7.11" = 8.19"

At a guess, Les Richmond Auto pink springs might work for what you want. These have a spring rate of 180 lbf/in and a free length of 15.9"

Then for 1200 lbf
compression = 1200 lbf / 180 lbf/in = 6.67"
ride height = 15.9" - 6.67" = 9.23"

For 1600 lbf
compression = 1600 lbf / 180 lbf/in = 8.89"
ride height = 15.9" - 8.89" = 7.01"

Now compare the ride heights for both springs
NCR9448 gives 9.97" and 7.11"
LRA pink gives 9.23" and 7.01"

The difference being 0.74" and 0.1"

The 180 lbf/in spring will give a softer ride into the bargain.

Fwiw LRA recommend purple yellow for fronts. They are 220/15.5 for Isuzu 110.

Many thanks bush65 very comprehensive answer!
I was thinking a spring with 180ft lb would be about right it's just sourcing them in the uk, although the specs of the spring Flagg describes is very close to the hd ones I have got (9448/9449) maybe though you guys out there run with heavier bull bars or a winch on.
The other option would be to run with the 9448/9449 combo up front and fit the inner helper springs of a 130 to the rear, this would also help when towing my caravan, but might be a bit harsh when empty!

PS, sorry for hijacking thread but maybe some useful info for the op

Yep that is with 1/4inch steel bull bar and a high mount.

i've added 20mm rear spring spacers in the past to rectify the level look. only really necessary when not using a bar and winch.

jc

Originally Posted by gwac110

Many thanks bush65 very comprehensive answer!
I was thinking a spring with 180ft lb would be about right it's just sourcing them in the uk, although the specs of the spring Flagg describes is very close to the hd ones I have got (9448/9449) maybe though you guys out there run with heavier bull bars or a winch on.
The other option would be to run with the 9448/9449 combo up front and fit the inner helper springs of a 130 to the rear, this would also help when towing my caravan, but might be a bit harsh when empty!

PS, sorry for hijacking thread but maybe some useful info for the op

Sorry I didn't notice your location, just assumed locals would be in the Isuzu forums.

A close spring to that LRA 180 lbf/in x 15.9" spring is Land Rover NCR8477, colour code Green-Blue-Yellow used in rear of RRC with Tdi engine (92 to 94), which we didn't get in Australia. The spring rate is 178 lbf/in and free length is 16.16".

Compression at 1200 lbf = 1200 lbf / 178 lbf/in = 6.74"
Ride height = 16.16" - 6.74" = 9.42"
or 9.97" - 9.42" = 0.55" lower than NRC9448 at 1200 lbf load

Compression at 1600 lbf = 1600 lbf / 178 lbf/in = 8.99"
Ride height = 16.16" - 8.99" = 7.17"
or 8.19" - 7.17" = 1.02" lower than NRC9448 at 1600 lbf load

Originally Posted by Bush65

Sorry I didn't notice your location, just assumed locals would be in the Isuzu forums.

A close spring to that LRA 180 lbf/in x 15.9" spring is Land Rover NCR8477, colour code Green-Blue-Yellow used in rear of RRC with Tdi engine (92 to 94), which we didn't get in Australia. The spring rate is 178 lbf/in and free length is 16.16".

Compression at 1200 lbf = 1200 lbf / 178 lbf/in = 6.74"
Ride height = 16.16" - 6.74" = 9.42"
or 9.97" - 9.42" = 0.55" lower than NRC9448 at 1200 lbf load

Compression at 1600 lbf = 1600 lbf / 178 lbf/in = 8.99"
Ride height = 16.16" - 8.99" = 7.17"
or 8.19" - 7.17" = 1.02" lower than NRC9448 at 1600 lbf load

I normally run those springs all round in my Isuzu powered RRC. The rate and ride is very good. With those orange poly extended bump stops and Koni's from a LC80 the spring and shock length matches perfectly. Full travel on the spring matches full travel on the shock, the shocks travel is a bit more than the bump-stop compressing halfway.

The valving on the Koni's however isn't quite right. I am at ~1150kg on each axle (varies with fuel etc) and I find them a little harsh on compression and even on the fastest rebound setting not quite where I want them.

I currently have a set of 240lb/in springs in the rear for towing and load carrying. They are too firm for running around lightly loaded. The 180lb/in in the rear are perfect when mostly empty.