Thread: drop arms for lifted P38A

There's no factory compensation for varying heights. In fact, if you look very carefully when adjusting the height while driving, the steering wheel goes off centre ever so slightly with the changes.

You just need an adjustable panhard rod to adjust the diff back to centre but as for correcting the castor, maybe off set bushes in the radius rods (if there is such a thing for the P38) would be a quickish fix until new arms are sourced (unless you want to cut/weld the axle ends ).

Adjustable panhard, so you can set the position at your nominated driving height. (thats the easy part)

For the front arms, you could have them heated up and cranked a few degrees, to suit your normal height which is now 2" higher. Its either this or cut the brackets off the front diff, and re-weld them in another spot. Specialist job either way. I will ask around if you like.

Andy

just an observation:

Yep, all of the above... the RR steering geometry is optimised for cruising at (factory) highway height. Any deviation is a compromise... hence the speed restrictions... plus the added stress on UJs

You'll notice that as the suspension rises to max height from "Access" the length of the wheelbase varies ever so slightly.

If you were to fit an adjustable panhard rod to counteract the axle displacement, it really needs to be an automatically adjusting one which changes length depending on the height setting... no doubt some bright spark will come up with a design

Paul, i spoke to a fabricator today, and he said he can make you up some adjustable panhards for $200 each. I Dont know about cranking the front arms though, are there any blacksmith out your way? i can supply you with some spare arms if you like.

custom jobbies would be out of the question as the factory ones have that sideways bend in the middle
Andy

Thanks for the responses blokes. This is a fiddly one.

I do actually use the various height settings on the car so whatever I end up doing is going to have an adverse effect on the other settings:

• most of the time, the height is locked at standard for driving around town, and the car will fit in my garage if the roof racks are not on;
• drop it down to highway mode if doing more than 80Kph for any more than a few minutes;
• up to standard or high if playing off-road;
• down to access height if visiting an elderly relative who needs a lift.

Looking at the scenarios above, the car spends most of it's time at standard height, but the steering/tracking issue is really only a problem at higher speeds and at highway height.

I like the idea of adjustable panhards and $200 each sounds fair.

Dunno about heating up the front arms though... sounds a bit risky. The little I remember from materials science at uni *many* years ago tells me that this will likely weaken the arms. I'd imagine the arms spend most of their time in compression on the road, but a few decent off-road bumps would introduce a fair amount of tension and shear forces.

Then again, all the arms really need is a small kink to flatten out the few degrees of rotation that the diff is being pushed forward/over itself.

Argh, and of course this is leading to more stress on the prop shaft and UJ's... my brain hurts

Gentle question: Do you really need the extra 50mm of lift as a standard accessory... or could you still get by with re-jigged EAS settings which would enable you to cruise at the design height but exploit the additional lift offered by GenIII's "on demand" ?

Have you checked the front arms bushes and looked at whether you can get offset ones. This is the most common method of correcting castor on Cruisers/Patrols up to about 3" lift. Over that they go to custom arms (best approach) or castor plates.

I saw a kit with 4 front radius arm bushes so I'm gunna guess they have two bush mounts, one for and one aft, like most radius arm set up (not an owner yet sorry). You could go to somewhere like Pedders and see if they can match the bush size up to supply offset ones. You could also make up some castor plates. These bolt to either side of the standard mount set up and use the same rear hole but have a lowered front hole to set the castor. The original front hole is just used now as a fixing point. But these are normally for big lifts on Cruiser/PAtrol like 5" and over. Cruiser owners also look at slotting the front hole downwards then locking in the desired place with a fat washer tacked over the hole. On a cruiser you can get 2 degrees of castor back by slotting the hole down by 14mm (size of hole in first place)

Not sure how easily these relate to the P38 but at any rate you would need to decide at what height you want the castor to be correct and be happy with that. Depending on the difference between fst highway and town height both could still be acceptable. Offroad height is not too important as speed is not normally high.

Adjustable panhards whilst good will not change your wandering that much if it;'s your castor that's affected most. 2" Cruiser/Patrols do not normally bother with or need panhards. Of course all this is relative to what factory settings are and the length of the originals and the arcs they travel.

Custom radius arms for the Cruiser/Patrols set you back about $1,600 so you'd want to be sure you really need them especially seeing as yours are one offs.

Originally Posted by fester

Have you checked the front arms bushes and looked at whether you can get offset ones. This is the most common method of correcting castor on Cruisers/Patrols up to about 3" lift. Over that they go to custom arms (best approach) or castor plates.

I saw a kit with 4 front radius arm bushes so I'm gunna guess they have two bush mounts, one for and one aft, like most radius arm set up (not an owner yet sorry). You could go to somewhere like Pedders and see if they can match the bush size up to supply offset ones. You could also make up some castor plates. These bolt to either side of the standard mount set up and use the same rear hole but have a lowered front hole to set the castor. The original front hole is just used now as a fixing point. But these are normally for big lifts on Cruiser/PAtrol like 5" and over. Cruiser owners also look at slotting the front hole downwards then locking in the desired place with a fat washer tacked over the hole. On a cruiser you can get 2 degrees of castor back by slotting the hole down by 14mm (size of hole in first place)

Not sure how easily these relate to the P38 but at any rate you would need to decide at what height you want the castor to be correct and be happy with that. Depending on the difference between fst highway and town height both could still be acceptable. Offroad height is not too important as speed is not normally high.

Adjustable panhards whilst good will not change your wandering that much if it;'s your castor that's affected most. 2" Cruiser/Patrols do not normally bother with or need panhards. Of course all this is relative to what factory settings are and the length of the originals and the arcs they travel.

Custom radius arms for the Cruiser/Patrols set you back about $1,600 so you'd want to be sure you really need them especially seeing as yours are one offs.

I have not checked, but i very much doubt anyone makes a offset bush for a p38. The only slight chance, is if a D2 one is the same, and someone makes them for a d2. They are nothing like a patrol / rangie classic bush.

you cannot make custom arms, as the factory ones have a dogleg in them to miss the chassis rail.

Paul, your car at any height compared to a factory p38 is 2 inches higher, correct?

Andy