Monday, 18 December 2017

Range Rover P38 bumpstop extensions

An uplifting experience


With EAS comes many things…comfort, practicality, safety and let’s be honest, a suave sophistication that allows us all to feel a bit special. With EAS also comes complexity, leaks, sporadic reliability and quite often, a questionable definition of the word “level”
My P38 came to me with certain modifications, some thought through a little better than others.
The vehicle was fitted with steel rims, complete with a sizable offset and massive tyre – 285/65 R16
It also had Arnott Gen 3 air bags, which give a 5cm “lift” on the front, and a 9cm “lift” on the rear.
These bags are tapered, and are designed to provide a lower than standard spring rate when extended, and a harder than standard rate when on the road.

The EAS height sensor arm values in the EAS ECU had also been played with, encouraging the EAS to sit higher at each of its positions, thereby ensuring the benefit of the taller air bags was borne out at the axle – approach, departure and ramp break over angles were significantly improved although further work on the arms themselves has improved matters no end.

Of course, certain elements don’t change – the articulation if anything was worse - articulation (in my eyes at least) is limited by either the axle/suspension geometry, or the contact point between the tyre and the body – the larger than standard wheel tyre combination hindered the full articulation potential of the car (and still does for now – I’m still pondering this problem – more as soon as ideas gel!)

The biggest weakness of the wheel tyre combination however was the bump stops.
When the EAS has an issue, there is the potential for the system to drop onto the bump stops and go into “hard fault”.
The system is relatively simple to fault find and not too technical to fix, so this alledged unreliability is not a big issue for me – I bought some hardware and software from Blackbox Solutions when I bought the car, so I can talk to the EAS, so in theory, as long as I can get the car home, I can fault find, repair and reset everything….but I do need to get it home.
In hard fault on the bump stops, Land Rover say you can drive the vehicle quite safely at 35mph, in fact they thoughtfully have the EAS remind the driver through the dashboard message centre with a not at all annoying “beep” and a “35mph max” message – the bump stops are a telescopic variable rate polymer, and although the ride may be a little harsh, they do enough.

All this works beautifully unless your car is running oversize rubber. What happens in this instance is the EAS will drop to the bump stops, but the rubber on the tyre will strike the wheel arch before the chassis has sat all the way down. 
In motion it acts as a very quick and effective (if somewhat dangerous) braking system, which draws the car to an abrupt halt, tearing bits of body and chunks of tyre in the process. At standstill, it forms an excellent 4 wheel “handbrake” and the wings slowly fold under the strain of the excess weight – the car, of course is un-movable (to the point it won’t load onto a recovery truck) ….not at all good, and certainly little chance of getting it home to sort the initial problem.

I was lucky – mine had an issue on the drive, but nonetheless, I still had to jack it back up and get some chunks of wood between the bump stop and the axle to take the strain of the wings, luckily all done before permanent damage had occurred.

Sorting the fault was no problem – it turned out to be the N/S front pipe not seated right in the airbag, a quick trim with a pencil sharpener and a test with some washing up liquid confirmed all was well, and on start-up, up she came, back to normal.

It got me to thinking though, extensions to bump stops might be a good idea.





You can extend the pad on the axle, but it involves a lot of car disassembly, and potentially welding - not ideal.
I concentrated on the chassis end, and came up with these little beauties, which fit to the chassis without welding, drilling and so on - a simple idea that now has the wheel safely off the wing when the car is sat all the way down.

Here's the car on it's bump stops - note we now have free wheel movement, and no body to rubber contact....



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