Thread: Self Levelling Unit for RR Classic

Originally Posted by Lotz-A-Landies

Sorry you haven't convinced me about the benefits of the self levelling unit.

While I agree with keeping the ride attitude over different loads you can achieve the ride attitude by using Poly-air bags in the spring. The low rate springs become a problem when the load leveller is pumped up under load and the additional weight is being carried over the centre of the vehicle. Everything goes along fine while you are running along in a straight line. However in cornering the central pivot/boge unit exacerbates rear end instability under centrifugal forces.

My RRc runs fine with no the boge unit, polyairs and attention to ride attitude but without the previous instability in hard cornering. The only improvement would be to install a control unit from the drivers position rather than having to manually inflate/deflate the Polyairs.

Obviously those who enjoy their RRC's offroad ability have not been able to articulate the benefits of enhanced articulation provided by the Boge / A frame design.

DL

OK, I performed the same test and took measurements of a Range Rover based 100'' hybrid i have. This vehicle is Isuzu powered with extended cab, Defender body,full exocage, comp style trayback with mid mounted winch and twin 80 litre under seat tanks, so no light weight.
It is fitted with heavy duty rear springs that are yellow and have 9 coils 18mm in dia with spacers totaling 4cms thick for some reason,and 12'' stroke Koni dampers on 38mm raised upper mounts,in the early fashion of bias mounting, as with the Rangey. It is not fitted with a Boge unit.It has cranked trailing arms. It is fitted with 235-85 x16, 31'' dia tyres on normal lwb series 3 rims, which have only 5mm more backspacing than 110 rims.
Some comparison measurements with the RangeRover of earlier.
Static spring length =33cm RR=30.5cm {7 coils 13mm diam}
Bump stop clearance=17cm RR=10.5 cms

Anyway, with right rear damper still connected I drove up the ramp until the rear wheel lifted and measured the vertical height from the bottom of the front tyre to the ground.This was only 65cm and I observed that the side wall of the left rear tyre was stuffed heavily into the top of the spring tower.
I next disconnected the right damper and drove up the ramp again until the wheel lifted and took the following measurements as before with the Rangey.The Rangey numbers are repeated in brackets
Distance from bottom of tyre to ground =68cm {82cm}
Vertical distance between upper and lower spring seats=53cms {50.5cm}
Free length of coil spring=41cm {43cm}
Compressed length of spring on left hand side=24 cm {15.5 cm}
Compressed length of left rear damper=48cm {36.5cm}
Lateral angular displacement of axle relative to chassis=14degrees {21 }
Distance between upper and lower damper mountings=83cm {70cm]
Observatoins
Left tyre sidewall dangerously stuffed into spring tower.{110s have larger dia springs and wider towers so this situation would be worse.)
Although trailing arm is cranked, bushing was still maxed out..
Make of all this what you will, but as can be seen, fitting heavier springs and raising the static ride height alters the axle articulation geometry relative to the chassis which inhibits wheel travel and can cause damaging tyre interference with the spring tower. Rangerover tyre was well clear of tower on earlier test.
Although it is difficult to quantify, the hybrid felt significantly tippyer when rocking the body by hand than the Rangey, despite not being able to climb as far up the ramp.
I'm thinking the optimum compromise would be something like Boge unit,soft springs, and polyairs inside the springs for the higher speed handling requirements.
Wagoo.

Originally Posted by 350RRC

Obviously those who enjoy their RRC's offroad ability have not been able to articulate the benefits of enhanced articulation provided by the Boge / A frame design.

DL

I still have exactly the same "A" frame, coil springs and suspension articulation. Just no boge unit.

Originally Posted by Lotz-A-Landies

I still have exactly the same "A" frame, coil springs and suspension articulation. Just no boge unit.

If so Diana you mustn't carry anything heavier than a cut lunch.
Wagoo.

I rebuilt the suspension on my 1990 RRC about three years ago. I loved the comfortable off road ride so went with LR-spec HD springs (only about 10 pounds higher rate + an inch in length), and softly-valved Bilsteins for a 'soft lift'. The Boge was reconditioned by a crowd in Sydney, forgotten who.

I don't think the fitment of the Boge affects articulation ability (compared with a non-Boge vehicle with springs suitable for the load weight) but it certainly improves ride comfort off road. I've ridden in a friends Disco 1 with stock suspension and while it's light years ahead of say, anything non-LR, there is much more side-to-side shaking compared to my equally stock RRC. All my 4wd friends remark on how amazingly comfortable my truck is off road; and it will go anywhere their lifted, large-tyred, locked, etc trucks will go too.

Perhaps there's a little more body roll in the corners with a Boge and soft springs but then I never bought a Rangie Classic to be a sports car. I wouldn't accuse the standard 3.9/Auto as having a 'sporty' response either, so I figure the stock suspension suits it best.

At the other end of the truck, I've found that the radius arm-axle bushings make quite a difference to cornering roll and no apparent difference to articulation or off road comfort (mine has no sway bars). When I did the rebuild, I used bushes specified for the earliest model Rangies and the body roll during a corner was impressive but I never felt it dangerous. They flogged out pretty quickly and were changed for the post-EFI/pre-sway bar spec bush that have an extra ring of steel around the middle. To my surprise, these made it handle much better without any noticeable drop in off road ability.

So for me, most of the time the Boge/soft springs is absolutely perfect. The only time it's less impressive is when the truck is fully loaded for a camping trip (family of four + all the gear): It rides a little low and after two Easters of just driving a little slower to avoid bottoming out I fitted some 220 pound rears from LRA just for the trip and it's much better. When the load comes off, it handles flatter through the corners but does lose a bit of traction off road. The ride is still quite good, although 220 is hardly a 'heavy' spring in the overall scheme of things. I've gone back to the 170 pound springs as I now use a D2a with SLS for big/heavy camping trips.

cheers,

bidds

Originally Posted by wagoo

If so Diana you mustn't carry anything heavier than a cut lunch.
Wagoo.

Or my Series II SWB on a car trailer?

Originally Posted by wagoo

If so Diana you mustn't carry anything heavier than a cut lunch.
Wagoo.

The most I've carried/towed with it was a SIIB with steel tray, 2 spare gear boxes, A frame, rear PTO and belt drive, spare wheel and sundary other spares. All up Mt Victoria, it also has LPG manifold tank on the rear floor and 125litre main tank which was full.



Doesn't seem to be dragging it's bum on the ground to me!

Originally Posted by Lotz-A-Landies

I still have exactly the same "A" frame, coil springs and suspension articulation. Just no boge unit.

I agree that your vehicle is sitting level in the above photographs, but your words above suggest that you just removed the boge unit and retained the original springs. So why is it not dragging its bum? Because you fitted polyairs to compensate.Not the same effect as central springing for offroad ability.
Wagoo.