Thread: Lifted P38 on air - questions

Hi Keithy,

Ive opted for 4mm thick 50mm hi rhs for the extended bump stops.

I was thinking to use hard rubber and found some hard 55mm thick but the weight of the car crushed it down too far and it was no more anywhere near 50mm.

Ive looked at the standard bump stops when vehicle lowered all the way down and they crush down to almost nothing.

With a flexible material it could be difficult know just how far 50mm ext might compress under extreme conditions and could cause a failure.

Planning on fitting my assembled kit this Tuesday. Assuming the little one is in day care. Otherwise, he'd want to help.

Finally got back to an auto eas that I can rely on. That was necessary in my opinion before playing around with the suspension some more. Hoping the 2nd hand modded rear sensors don't screw that up.

Will obviously let you know how it goes. Concerns are air spring feet pushing too close to the top of the air spring in compression. And my +20mm bump stops needing further mods.

Hi Sean

Ive just checked mine with vehicle on the bump stops by depressurizing the system and removing the air lines to the rear so it cant go any further. With 50 mm rhs bump stop extensions in place, and the rear sensors extended plus 22mm on the upper arm and plus 23 on the lower arm the elbow of the sensor arm was 10mm away from the left rear rhs bump stop ext and a few mm closer on the right hand rear. Close but I think that will be ok.

The bump stops on the rear come down right on the front of the rear plates, in fact slightly over the edge on mine so the extended stop plates cannot be shifted back further away from the sensor arms.

My plates are 100mmx100mm.

The fronts are 75mmx75mm (50mm hi) and sit perfectly in the middle

Those original bump stops crunch down to 10mm thick when lowered.

Cheers Paul

My 20c worth on this, based on playing around with +50mm suspension lift kits for quite a while, using +50mm shocks at the front, and equivalent of moving old front shocks to rear:
- front bump stops @ 65mm
- rear bump stops @ 90mm

If reusing old bump stops, extend the plate at the diff to accommodate the bump stops using something with a little bit of give like high density rubber.
A customer or mine in the US found that ice hockey pucks (1" thick, 3" dia) were very useful. Another used marine/boat rubber to achieve the required support and resistance.

Can someone remind me of the overall height of the oem bump stop.
Of course, one of the original aims with this lift (correct me if I'm wrong) was to achieve greater articulation. If we all end up extending bump stops too much, we won't have achieved the aim. But of course there are practical geometric limitations. Certainly don't want to bottom out on shockers or damage the bags on full compression.

I've already extended my bump stops by 20mm front and rear. I'll see if they need further modding once the kit is fitted - hoping it'll be today.

- front bump stops @ 65mm
- rear bump stops @ 90mm
Paul is that measurement the full length of the bump stops when they're out of the car, or is measurement taken from chassis

If anyone is keen to remodel the rear airbag tophat, ill buy a pair!

Have had to extend the rear bump stops primarily due to the height sensor tapping the chassis (the elbow of the sensor arms is the point of contact with the chassis). Secondary reason was due to the piston of the rear springs getting very personal with the tophat.

My bump stop pad is 55mm taller in the rear.

The options (and thus the reason I'm not completely finished my lift) are:

- Bend rear sensor top arm down a few degrees and extend it, reverting the lower sensor arm to standard. Then limit up-travel with the bump stops once the piston meets the tophat.

Or

- As above, except, manufacture a tophat for the rear springs that allows the piston to travel further up and run with no bump stop extension.

As for the front end, the height sensors hit the low limit before the spring has fully compressed (piston could theoretically travel up another 2 to 3"). My front bump stop pad is raised by 35 - 40mm from memory.

The way I see it, the front end has these options:

- Front height sensor upper arm bend a few degrees and extend by 25mm (estimate), revert the lower sensor arm to standard. If the length and angle of bend are right, the arc of travel will prevent the sensor from reaching its low limit on up travel and will actually begin to arc down again briefly at max spring compression.

Or

- Leave front bump stop pads as-is and put up with EAS faults if the car drops below access height. This happened to me twice prior to raising the bump stop pad. It was easily reset and the car lifted itself up no worries, but it is a pain.

This part of the lift (in my case) is very much R&D now that I've got a baseline and working suspension setup that I can safely drive around on the street.

Any engineers out there who wish to aid with height sensor mods, feel free to shout out! It's all about getting that arc of travel right. Prerequisites are:

- Top height sensor arm to be bent down near the sensor by (x) degrees and lengthened by (x)mm to allow the same bit count at current heights, but modify the arc of travel to a lower point at the join between the two arms.

Hope it explains the train of thought!

Cheers
Keithy

Keith, I'll have a proper read of your post in due course. But can I ask - do these problems all stem from the 65mm high spacers? Mine are 48mm and my initial findings after fitting everything today seem positive. I've still to calibrate the eas, but compression to the bump stops front and rear seems fine. My sensors have been extended +25mm on each of the upper and lower arms. This works. For the front I've raised the attachment point to the radius arm by 25mm. Left the sensors alone.

Will need to double check it all. It was a rushed job today but it all seemed to go fine. Used the lynch pins to attach the rear spacers to the axle pads and these seem fine. Might bolt or weld as well.

Thanks to you for all the help and input. .