Suspension and Wheels

Suspension:

The plan is to replace the steel springs with air springs.
I used to own a Subaru GL-10 which had driver adjustable air springs with automatic ride height control. It had the best ride on washboard dirt roads of any car that I've driven. It convinced me that air suspension is the way to go. I also expect that lowering the stretch a few inches when driving on the street will increase the gas mileage by one or two MPG.

The rear looks like it will be easy. There is a lot of room around the steel spring that should be able to accept a large air spring from Firestone.

The front looks more difficult. Since I need to design for a static load on the front axle of 3000# and the spring is located about half way out the effective arm, I'll need springs that can take 3000# of load each at close to full extension. This one, a style 202 could take the load, but the 9.9" diameter is going to be hard to fit in the front suspension. I'll have to take some more measurements.



Another option is a 1T28C-7 which also comes in a 4 ply rating (as opposed to the 2 ply standard). This one is a reversible sleeve type, similar to what my Subaru had. It's a little better at only 9.1" dia, but still, a quick look at the photo at the top of this page shows that it may take some major work to make it fit. It also need a minimum height of 5". The reversible sleeve type have a very constant spring rate in their normal operating range. I'm assuming that this would provide a smoother ride than the bellows type.


Once I figure out how to support the front of the stretch on air springs, I'll have to control the ride height for varying driving conditions and vehicle loads. Remember that Subaru that I used to own? Well, it met it's end when a kid stole it and ran it over a curb and through a fence at high speed while being pursued by out friends in blue. Since the kid wasn't old enough to drive, he also had no insurance. As a result I ended up with quite a few parts, including all the electromechanical parts for controlling the suspension. It was a bit expensive, but it was better than getting nothing for the car.



Control electronics.
The local Subaru dealer was very kind. They allowed me to make copies of the wiring diagram for the air suspension system. Click here if you want to see them. It looks like the wire colors even match what was in the car! :-) I've analyzed the original Subaru struts (which are much to small for a Vanagon) and found that ride height is measured using a set of four reed switches activated by a magnets inside the struts. I expect that I will be able to duplicate this in some way and also provide more than the original two ride height options by adding more switches.





Wheels and Tires:

I wanted better wheels for a few reasons. The 14" wheels looked much too small on the stretch. I wanted better handling, and I was hoping for lower rolling resistance.
Knowing that the stretch was going to have very high loads, and see off road use, I decided to look only at forged alloy wheels. I've seen forged wheels in junkyards, usually they don't crack. They are much more likely to bend when they yield. Cast alloys are more likely to crack when severely overloaded. I didn't like the idea of a wheel cracking on me if I happen to hit a large rock at high speed off road.

I've found these Mercedes 8 hole 15" X 6.5" wheels locally from Acker Wheel in San Jose. Mercedes part number is: #210 401 03 02 and they are marked 6.5JX15H2 and ET 37. I was quoted $145 each on the phone. But that turned out to be an error. They wanted $250. each. In the end they gave me a better deal than that, but they were still pretty pricey.

I looked around for tires and found on a local Eurovan the Michelin Ajelis 205/65 R 15 C, M&S, 102/100T, 1875 LB. at 54 PSI. I liked the look of the tire so I ordered them from Americas tire company. They cost $456 for 4 balanced w/ road hazard warranty and tax.

8/5/99 1 hour Drilled out stud holes in wheels to 15.1 mm, chamfer and deburr.
8/18/99 Bought Porsche studs. Rear 901 331 671 00 from a 65-68 911 rear 52mm (need longer). Front 911 331 671 00 from a 924 Rear Disc 79 - 82 67mm. About $85 for 20 studs, aftermarket.
8/18/99 5 hours Install studs in front Syncro hubs. These went into the hub with light pressure indicating that a slightly larger spline would be better. The hubs had to come off to install the studs. Machined 1/4" wheel spacers for use on the rear with steel wheels.




The studs for were too big for the holes in the wheels so I drilled the wheel out on the mill with a 15.1mm drill. This worked out to about the same percentage over the stud size as the original holes were over the original studs. 15.1mm also happens to be some "standard" fractional inch size. The Mercedes lug nut seating surface has a different shape than the VW one. I machined the stud contact seat with a VW lug nut that I made into a cutting tool with a chisel and a grinder. I used a old stud as a pilot to guide the tool in the hole.

I installed new rear studs. 901 331 671 00 from a 65-68 911 Porsche, 52mm long. The studs should be longer by 5mm for full thread engagement when the wheel is on. I could only find one 58mm stud and I haven't figured out what it came off of. I did not need to remove the hubs to install the studs, only the drums. The studs pressed in tight which is good. The front studs came from a `79 to `82 Porsche 924 rear disc and are 67mm long. The front hubs on the Syncro had to come off to replace the studs. The front ones were only a very light press fit in the hubs. It would probably be better if they were a tighter fit. The studs cost me about $85 for the set of 20.

The new tires ride well. Small bumps are more pronounced than they were with my large sidewall 14" ones. The rolling drag feels like it is down some but I didn't take any measurements. The steering is much easier and sidewall flex is much reduced.