Thread: Self Levelling Unit for RR Classic

Serg, My head is still hurting from making sense of the data from all the fiddling around with the RangeRover/ Hybrid to properly understand your questions today, so I'll have another look at your post tomorrow. Not that I know much about the subject from a handling perspective.I'm a conservative on road driver and my Landy barely makes 90kmh anyway. Might be worth calling Rick130 over to the thread.
The only thing that I recall at the moment is that I read many years ago that the length of RRC trailing arms,relative to suspension height was selected to give sufficient roll steer so as to cancel out the effect of cross winds, instead of getting blown off the road or into the path of oncoming traffic.
Wagoo.
To answer your first question Serg.The extended side damper was disconnected, so a longer damper would not apply any more downforce unless it was one of those Airshocks they use in the USA.

Re the fitting of a Mazda coil spring in place of the Boge unit. It would be woefully inadequate. As stated on an earlier post, I fitted a double opposite wound pair of coils with a combined rate of around 380LBs Inch in place of the Boge and that wasn't adequate.

Originally Posted by superquag

Interesting thought... the 89 Paj has a similar suspension setup, torsion front end with little travel and cart springs on the rear. Wonder how that would perform up your ramp...

The Renault 16 also had huge suspension travel and soft springs. - and would almost roll over as you backed out of your driveway.

- But did they hang on !!!

If your Paj is similar to the Jack it will have a powr lock style limited slip rear diff. When The Jackaroo leaned over in an attempt to cross articulate and began to lose traction on the ramp at about the 30cm height mark, I dabbed the brake pedal to get the lsd plates to bite and it kept moving,chassis leveled back up due to propshaft torque and probably would have kept going up even without the LSD effect until it fell over.Had I driven the left front wheel up the ramp instead, propshaft torque would have exaggerated the lean to the right, causing the left rear wheel to lift, and the LSD may not have had enough bite for the right hand wheel to push the vehicle up the ramp.
wagoo.

Originally Posted by uninformed

So the question is, from an onroad handling and offroad high speed handling point of view, how would lowing the rear roll axis and the rear Antisquat effect the behavior of the vehicle.

Lowering the rear roll-centre (i.e. lowering the ball joint) will make less cornering load be taken by the suspension links and more by the springs. The result is less cornering load on the rear wheels and more neutral handling. Meaning you can run firmer springs on the rear without running into over-steer issues (exactly as Quag describes).

Landrover did exactly this with the D2. They changed the rear end from a three link with a high central locator (the ball joint, which is the rear roll centre) to a radius arm setup with central locating being done much lower. In a nut-shell they lowered the rear axle roll centre so they could use firmer springs and swaybar without the resulting vicious handling.

Originally Posted by Dougal

Lowering the rear roll-centre (i.e. lowering the ball joint) will make less cornering load be taken by the suspension links and more by the springs. The result is less cornering load on the rear wheels and more neutral handling. Meaning you can run firmer springs on the rear without running into over-steer issues (exactly as Quag describes).

Landrover did exactly this with the D2. They changed the rear end from a three link with a high central locator (the ball joint, which is the rear roll centre) to a radius arm setup with central locating being done much lower. In a nut-shell they lowered the rear axle roll centre so they could use firmer springs and swaybar without the resulting vicious handling.

Thanks Dougal,
was the rear of the D2 a watts link for lateral location? how much lower than the ball was the RC?

Although your answer gave some food for thought(I actually think a LITTLE oversteer better than understeer but thats just me) I was referring to the rear axle roll axis, not the roll center....

Originally Posted by uninformed

Thanks Dougal,
was the rear of the D2 a watts link for lateral location? how much lower than the ball was the RC?

Although your answer gave some food for thought(I actually think a LITTLE oversteer better than understeer but thats just me) I was referring to the rear axle roll axis, not the roll center....

I think all the D2's are watts linkage. I don't have one handy to check.
The roll-axis is simply a line joining front and rear roll-centres, so not a big distinction there. The front roll-centre is basically axle level so visualising it is pretty easy.

Oversteer is fine if the driver can handle it. The problem I had was following car drivers into corners, they hit the brakes and as soon as I try to slow down I'm following them sideways. Likewise evasive action (avoiding other drivers, deer etc) would step the rear end out.
Softer rear springs tamed it well enough for me. I haven't had it sideways on dry tarmac for a long time, mainly on ice and that's not much fun.

Haven't read any of the thread yet, but here's info on how the Nivomat works.

A Sachs (Boge) brochure

http://www.cadillacfaq.com/faq/answers/pdf/nivomat.pdf

[edit 9:11am] I'm pretty sure the Rangie/Land Rover one doesn't include the damping feature that's outlined in that doc, only the self levelling
[2nd edit] The Nivomat is different to the Hydromat used in Land Rovers and Mercs, I'll try and upload a drawing later.

Originally Posted by Dougal

I think all the D2's are watts linkage. I don't have one handy to check.
The roll-axis is simply a line joining front and rear roll-centres, so not a big distinction there. The front roll-centre is basically axle level so visualising it is pretty easy.

Oversteer is fine if the driver can handle it. The problem I had was following car drivers into corners, they hit the brakes and as soon as I try to slow down I'm following them sideways. Likewise evasive action (avoiding other drivers, deer etc) would step the rear end out.
Softer rear springs tamed it well enough for me. I haven't had it sideways on dry tarmac for a long time, mainly on ice and that's not much fun.

ummm...I dont mean to correct you, but there are 3 dfferent roll axis in a live axle rover. The front axle roll axis, the rear axle roll axis and the vehicle roll axis. With regards to roll centers the rear is the center rotation point of the ball as this is the Instant center of the upper triangulated links (as the TA's are parrallel they do not play a part in Roll center). This point would not change with any spring lift...only tyre dia change. The front roll center is the intersection of the Panhard rod through the mid point of the chassis when viewd from the front. It will change with either spring change or tyre dia change. These 2 roll centers form the Vehicle roll axis, and like I said earlier, on a stock RR its is slopping down to the front, which is definied as "loose" and the rear is likely to break traction first. The axle roll aixs is different to this and is the definition of whether the individual axle is in either oversteer, neutral or understeer at stactic ride height. This will determine how that particular axle behaves onroad during cornering and even going over bumps etc. The more we spring lift a rover the more the front and rear axle go into roll oversteer, especially the rear....

Originally Posted by uninformed

ummm...I dont mean to correct you, but there are 3 dfferent roll axis in a live axle rover. The front axle roll axis, the rear axle roll axis and the vehicle roll axis. With regards to roll centers the rear is the center rotation point of the ball as this is the Instant center of the upper triangulated links (as the TA's are parrallel they do not play a part in Roll center). This point would not change with any spring lift...only tyre dia change. The front roll center is the intersection of the Panhard rod through the mid point of the chassis when viewd from the front. It will change with either spring change or tyre dia change. These 2 roll centers form the Vehicle roll axis, and like I said earlier, on a stock RR its is slopping down to the front, which is definied as "loose" and the rear is likely to break traction first. The axle roll aixs is different to this and is the definition of whether the individual axle is in either oversteer, neutral or understeer at stactic ride height. This will determine how that particular axle behaves onroad during cornering and even going over bumps etc. The more we spring lift a rover the more the front and rear axle go into roll oversteer, especially the rear....

I agree with all that. Just wasn't sure how far in you wanted to go.