Anyone know how?

[Wanderer]

Ok.
When you do a suspension lift you alter the castor angle.

With the new Rangies and thier ability to change the ride height.
How do they compensate for the alterations to the castor angle?

Anyone know?
Or point me to a website.

I've got visions of a motor winding in and out the length of the radius arms.


Ed

[strapping young lad]

are the new rangies on wishbones or have they got live axles?

if wishbones then that wouldnt be a problem

[Wanderer]

HI Dyf,
I missed your reply.
I haven't got a clue. Anyone know if it's wishbones?

Looks like it's get the tape measure out at Donington and see how difference there is between the radius arms for a 2in lift as opposed to the normal stock item.

Any mathmaticians out there. Apparently a 2" lift moves the castor angle by 2 to 3 degrees. How much longer would a Disco radius arm need to be?

Can you do it be using the thread on the end of the radius arm and packing it out with "whatever".

Ed

[muddyweb]

A 2" lift is around a 3 degree change in castor angle, that's right.

There isn't a great need to make them any longer.  When the suspension articulates, the axle forms an arc centred at the fixed end of the radius arm (that's where it gets it's name)

As your suspension compresses, your wheelbase effectively gets longer when it droops, the wheelbase shortens.  This is perfectly normal.

The amount of movement is not all that large until you start getting to huge axle travel.

By fitting a longer radius arm, you are only increasing the radius of the arc the axle forms.  Which may correct it in the netural position, but will make it wrong everywhere else in the suspension travel.

Hope that makes sense :-)

[Wanderer]

HI Tim,
THanks for taking the time. I know you're busy doing my stickers  :D
Is it the castor angle that is causing the steering not to straighten up as well as it ought to.
My thoughts were that a longer radius arm might bring the axle back into line thereby sorting the problem.

Or do we need to fit a pair of the angled (for want of a better word) swivels?

It's all a bit much for someone like me that's been brought up on a diet of Ford Capris and Escorts.  :?  :?  :?
It was nice and easy when you raised the back and lowered the front and didn't give a monkeys about stability.

Ed

[muddyweb]

OK...

Please forgive the diagram, it's not technically accurate, and the exact position of the bits and the angles is different between vehicles.

In it's normal position, the steering rotates around line 'A' as it turns left-right.

In this position, the steering will self-centre and be stable at speed.  (This angle is worked out by Land Rover)


As the suspension drops away from the chassis the whole thing rotates clockwise around an arc as shown...  this has the effect of turning the axle clockwise, changing the castor angle towards line 'B'.  With this change in castor, the steering geometry changes and self-centre / stability will change.

If you lift the suspension, you are moving the castor angle by increasing the distance between the axle and chassis.


So, to correct a castor angle change, you need to rotate the axle ant-clockwise relative to the radius arms so that it comes back to line 'A'

There are a few products to do this :

Machined / Modified Swivels :  These work well, but can be expensive and if you ever want to take them off will require replacement.

Caster-corrected bushes : ARB make these at around 45 quid.  Simple to fit, and easy to change later.  They can cause binding under heavy articulation.

Caster-corrected radius arms :  These have a modified end, or may be 'cranked' to return the axle to true.  More expensive than bushes but a simple fitment.  (I have a set of QT radius arms on Tigger)

If that doesn't make sense..... erm sorry... but I'm busy doing your stickers :-)

[Wanderer]

Excellent stuff Tim,
So with that info QT have also altered the angle on the axle end of the radius arm with the offset at that end.
I thought it was just a case of lengthening the radius arms.
Back to the drawing board or the bank managers :(

Thanks again

Ed

[muddyweb]

So with that info QT have also altered the angle on the axle end of the radius arm

Yup.. spot on.