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Date:         Sat, 18 Aug 2007 11:04:14 -0700
Reply-To:     Reinhard Vehring <rvehring@YAHOO.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Reinhard Vehring <rvehring@YAHOO.COM>
Subject:      Re: ride height adjustment? (long post)
Comments: To: Don Hanson <dhanson@GORGE.NET>
In-Reply-To:  <000501c7e1b0$c796f000$15b2d8d1@dhanson>
Content-Type: text/plain; charset=iso-8859-1

Don, interesting question. I had that very problem in the extreme at Syncro de Mayo this year, where my van was perfectly "unbalanced" with 100 % weight on front left and back right wheels and the other two were up in the air. I could make it rock back and forth by moving in my seat. Anyway, my two cents:

The contact force of each tire in a static situation is determined by the a couple of components. A) unsprung weight of the suspension parts (wheel, steering knuckle, control arms) this is minor compared to the other forces and only becomes more important in a dynamic situation. B) spring constant and compression of the coil spring, the most important one c) spring forces of other suspension components (sway bar torsion to prevent lean, or preloaded shocks that have a some compressible gas reservoir) this also is usually minor. So it's mostly the spring constant, k, and the spring compression. Compression is determined by the weight distribution - the center of gravity.

I don't know the k for vanagon springs. The guys who claim to have designed lift springs must know, but they are not telling (now is your opportunity!) But I can try to estimate: It's probably around 500 N/cm. If this is about right, loading 250 kg of stuff into the van ( 4 normal sized guys) would cause an extra force of 2450 N (613 N per wheel) causing it to sag about 12 mm. Now it would really be interesting to know some specs on the progressive springs that GoWesty has for the Syncro...

If I understand you right, you don't want a ride height adjustment, but rather equalize contact force (diagonally) to maximize traction. In my humble opinion, unless you want to break a new record on a (perfectly flat) race track with you vanagon, that doesn't matter. I guess this is why there is no way on a stock vanagon to adjust for that. "Unusual" ways of trying this would be: a) Mess with k: Gas bladders in the back that can be inflated to different pressure, for example, or maybe different preload on gas shocks. (the two easiest ways in my opinion) b) Mess with compression: Onesided spacers. Find out spring constant, measure diagonal force difference (with driver in place), calculate spacer thickness for compensation, machine custom spacer, install, measure again. Lot's of work and you can never take a passenger in the van or drive on anything else but a perfectly level surface, because it would throw off the balance again. If I remember right racecars are balanced with the driver in the car and they don't haul around camping equipment :-) By the way, I don't think you can affect front - back or left - right contact force balance that way at all. That's just a matter of center of gravity. For example most Westies sag left. Ride height can be corrected, contact force cannot. Even if levelled there is more weight on the left side. Have fun, Reinhard 83 "Half-Syncro"-Westy, Moose

--- Don Hanson <dhanson@GORGE.NET> wrote:

> I know, "Check the Archives"...but my dial-up > connection is so slow that > when I try to get something odd-ball out of the List > Archives, it sometimes > takes me all dang morning to not succeed anyhow. > Problem: My 84 2wd van seems a bit 'off' in it's > "stance". It is not > exactly 'even' in how it sits. With our racecars, > we called it > "Corner-balanced". Ideally, each wheel would share > an equal weight, giving > you an equal amount of traction at all four tires. > In reality, most cars > are heavier at one end or the other..Examples would > be...say,. the Olds > Tornado for a heavy front end weight bias and the > Porsche 911 for a heavy > rear/front bias.. You can't do much about the F/R > balance, but you can > adjust the side to side/corner to corner balance by > adjusting ride height at > the wheels. That is what you always hear about on > NASCAR TV broadcasts when > they talk about "loose, tight" and making an > adjustment during a pit > stop..Those cars have easily accessed ride height > adjustments that allow a > crewman to 'tweek' the ride height in a few seconds. > Many vehicles have > 'coil over' suspensions, where the springs sit > around the shock body and > rest on a threaded spring perch, allowing you to > adjust the ride height by > moving the spring perch up or down. > So my van, if you look closely or pay attention as > you drive in low > traction situations, it seems like the left rear and > the right front wheels > are taking more load than the other diagonal > corners..If you can picture the > van as a table with four legs, it would be like a > table with un-even > legs..The table, you'd stick a matchbook under one > or two legs and it would > be steady again..The vehicle, you need to extend the > suspension at one or > two corners. Or, you would cut off one leg of the > table to make it stable > again, or lower a corner of the van.. > Mine, the right rear wheel (or the left front) > seems "light", so I want > to either extend that and put more of the load > there, or lower the left > rear/right front to allow the right rear and left > front to carry more load. > It is a bit difficult to visualize..but hold a book > parallel to the floor > and rotate it around a bit, you will see the > relationship between the > corners.."corner balance" In a racecar, we used > four scales and actually > weighed the load on all four tires, and then > adjusted the suspension for the > best balance we could achieve... > So on a van, is there any way to influence/adjust > the suspension for > "length"...Not the right term, I know.."extension?" > Ride height is the term > used for racing..but a van is hardly a race > vehicle.. > Sorry if this has been discussed before and it's > "in the archives"... > Don Hanson >

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