Thread: Self Levelling Unit for RR Classic

The firm section will unload first as it is putting pressure both on its adjacent spring mount, and the soft section of the spring. The soft part can't overcome the hard part.

Originally Posted by isuzutoo-eh

The firm section will unload first as it is putting pressure both on its adjacent spring mount, and the soft section of the spring. The soft part can't overcome the hard part.

Thanks Mark. It seems obvious now. The question I should have asked, and someone with a dual rate sprung vehicle, rock sliders and a high lift jack might be able to answer. How much body roll if any does it take before the hard section of the spring unloads and the soft section comes into play? And will that change the roll centre? And whilst this thread has concentrated on coil sprung vehicles,On leaf sprung vehicles,what effect do rubber or leaf helper springs have on altering roll centre when body roll brings them in to play?
Wagoo.

Originally Posted by wagoo

I have a few questions.
Is roll centre height a constant? What effect does dual rate springs have on roll centre ?

The roll centres are geometric and based off link position. So dual rate springs themselves have no direct influence.
There is also a force based roll centre. I've been avoiding that.

Originally Posted by Dougal

The roll centres are geometric and based off link position. So dual rate springs themselves have no direct influence.
There is also a force based roll centre. I've been avoiding that.

dont hold back info on us Dougal

re roll centers? at a guess, Id say the rear is fixed as the body/chassis/links pivot around the ball joint. The front is not fixed being the panhard. In my mind I see the body/chassis moving with body roll etc, and because the panhard is attached to the chassis at one end it must move...go into a left hand corner and the body rolls right,compressing the right spring and bringing the chassis end of the panhard lower in relation to the axle...lowering the RC. Go into a right hand bend and the body leans to the left which is compressing the left spring and extending the right, which raises the panhard at chassis end and raises the RC..

Like I said just a guess.

Load leveller - spring rate - shock valving???

Dougal said earlier that with the rear stepping out on his vehicle, that softer spring rates helped fix this...So what spring rates were you running and what did you change to? How do these new softer springs compare to the origanal early RR spring rates. Im guessing the soft 130ish lb OEM springs where well worked with the Load leveller...and on top of this how would shock valving effect actual handling and offroad ability when considering the whole rear end as a complete system???

Originally Posted by uninformed

dont hold back info on us Dougal

There comes a point where I have better things to do. Force based roll centres are way past that.

Originally Posted by uninformed

Dougal said earlier that with the rear stepping out on his vehicle, that softer spring rates helped fix this...So what spring rates were you running and what did you change to? How do these new softer springs compare to the origanal early RR spring rates. Im guessing the soft 130ish lb OEM springs where well worked with the Load leveller...and on top of this how would shock valving effect actual handling and offroad ability when considering the whole rear end as a complete system???

When I got the vehicle it had ~240 lb/in in the front, ~330 lb/in in the rear and the rear springs were also +1 inch height. Front radius arm bushings are polyurethane which gives me a sway-bar effect up front. It was very tail happy. The extra height of the rear coils probably put it beyond the point where the rear self-leveller did anything. So all the weight was likely carried by the outboard springs.
I also had the list to starboard that all rangies of that era have.

I found a 1 inch spacer under the right rear spring made it sit level for the first time ever. I also wen to 180lb/in springs all round, flipped front spring seats and welded in locating rings to give another ~30mm ride height in the front which made it nice and level unloaded. Very happy with the ride, but it dragged it's tail when towing or with 2+ mountainbikes on a towball rack.

The list to starboard is apparently caused by the front axle, in particular the brackets where the radius arms bolt on. With the axle out one radius arm tip is lower than the other. Swapping to 97 disco axles meant the 1 inch spacer in the right rear wasn't needed to stay level. But this also dropped the rear of the vehicle by half an inch.

I then put gas shocks in the front (koni landcruiser 80) which lifted the front by about an inch. Compounded with the lost half inch in the rear it looked stupid. Going back to standard spring seats bought me back to level unloaded and handling remained predictable.

I've been running those 240lb/in springs in the rear for the last two years or so. I haven't been into any situations with it recently where the oversteer would become apparent, which is one way of saying so far, no problem. The ride isn't as nice as with the 180lb/in springs. Perhaps happiness lies with 180lb/in springs and 1 inch spacers in the rear?

do you think this difference in the front end that causes the lean a mistake or on purpose....maybe a road camber correction device....as most roads are crowned in the center???

Originally Posted by uninformed

do you think this difference in the front end that causes the lean a mistake or on purpose....maybe a road camber correction device....as most roads are crowned in the center???

I think it was a mistake as the difference is about 3x what you would expect for camber compensation and the flop/flop feeling while driving from one corner to another was terrible.
My nissan cars all had some factory set to the right, but it was only about 10mm. The rover with factory springs was close to 2 inches. With HD springs (180lb/in) of equal length all round it was still more than expected.

Originally Posted by Dougal

I also had the list to starboard that all rangies of that era have.

The list to starboard is apparently caused by the front axle, in particular the brackets where the radius arms bolt on. With the axle out one radius arm tip is lower than the other. Swapping to 97 disco axles meant the 1 inch spacer in the right rear wasn't needed to stay level. But this also dropped the rear of the vehicle by half an inch.

I'm pretty sure the list to starboard is caused by the weight of the offset LT95 transfercase. That's why putting a spacer under the right rear spring fixes it.

There was a thread on one of the pommy sites that went right into the issue.

Didn't later models have a longer RHS rear spring from the factory?

cheers, DL