Date: Thu, 18 Jun 1998 19:49:29 -0700
Reply-To: David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject: Re: Pre-loading Rear Springs re Syncro Suspension (long)
In-Reply-To: <3588C63D.2ACDE61F@Schwenk-Law.com>
Content-Type: text/plain; charset="us-ascii"
Great dicussion happening here! I am currently using an extra stock
"donut" on each side of the rear of my Double Cab. I have a question about
the front spacers that we are talking about. Where do you put them in and
what do you use? I am assuming that it is above the spring cap and the
piece that attaches to the frame where the spring cap rests against. If I
am correct, how high can one go before the spring/strut assembley could pop
out sideways? In the rear there is about 3" worth of spacers you could use
before you risk everything popping apart.
I have done the same on a Rabbit where I installed a 1" metal spacer
between the fender and the strut bushing but I replaced the oringinal bolts
with longer ones to hold it in place there was no chance of it popping out.
I am all for lifting my Syncro a bit, but safety first!
At 00:48 6/18/98 -0700, Steven X. Schwenk wrote:
>With a vehicle as neat and versatile as a vw syncro, good suspension is
>almost a necessity to fully utilize and realize the value of the
>vehicle. Of course, the stock suspension sucks. And there are limited
>alternatives.
>
>KYB is not an option. While they are arguably somewhat better for the
>rear than the completely stock set up , you can only get them for the
>rear...and they are poorly matched to the front Boges. The result is an
>improvement so insignificant and with drawbacks that it does not really
>qualify as an improvement.
>
>The KYB lack good dampening, but offer some measure of stiffness the
>stock set up lacks. The stock Boges offer decent dampening, but overall
>everything is a little too soft. Not much you can do about the KYB
>dampening. You can, however, firm up the boges and still take advantage
>of their "better than the KYB" dampening. Plus, the Boges are much
>better matched to the front Boges than the KYB, and thus work better
>with the front. (The KYB and Boges are the only shocks available in the
>U.S. for the syncro rear...only Boges are available for the syncro
>front.)
>
>The suspension basically has three components. Compression dampening,
>when the shock is being compressed; upswing dampening (I think there's a
>better term), when the shock is extending; and spring rate. Further
>adjustments can be had by adjusting the amount of oil and the pressure
>of the gas/air, if any. You can also change the size of the valves
>that control the flow of oil and improve the efficiency of the other
>components. These are not options on any syncro shocks available in the
>us, however. Nevertheless, if money were no object, the syncro could
>be outfitted with killer suspension that would vastly improve all that
>the vehicle can deliver above and beyond just about any other
>modification you could do.
>
>On off road racing bikes, you can (must) adjust both the compression and
>upswing dampening as well as the spring rate of both the front and rear
>suspension, with the goal being that front and rear work together and
>independently. Mosr experts also have the shock custom valved for their
>weight and riding style. The factory suspension for the top
>professionals is vastly ahead in performance of anything available to
>everyone else. The only way to obtain the right set up, though, is to
>test and test and test. There are general rules to follow.
>
>The suspension should be firm yet supple and responsive. To achieve
>this goal, you have to have the right spring rate and dampening, which
>must work together. Since there's not much to be done with the
>dampening on the shocks available to us, all we are left with is tuning
>the spring rate.
>
>On off-road racing bikes, the spring adjustment is referred to as "sag
>height." This is the amount the suspension sags when fully loaded.
>First you measure the suspension unloaded. Then you measure the
>suspension (the amount of compression) with the rider sitting on the
>bike. You adjust the "pre-load" of the spring until the difference
>between unloaded and loaded "sag" is within pre-determined specs. The
>pre-load, or spring rate, adjustment is accomplished by turning a large
>nut which can be tightened to compress the shock spring or loosened to
>de-compres it. The same adjustment can be had by inserting a spacer
>between the spring and the shock body, thereby further compressing the
>spring even when the bike is unloaded.
>
>There is an optimal "sag height" for the syncro. No one has figured it
>out yet, at least that we know of. Ideally, we would start with a
>bilstien shocks with adjustable dampening and an adjustable spring rate,
>and then do a lot of testing to figure out the best settings for both
>dasmpening and spring rate. All we can do with what's available,
>though, is adjust spring rate to the best available and
>front-rear-matched dampening, which happens to be the stock Boges.
>
> Derek Drew introduced me to the concept of using stock spacers
>used in the rear suspension to pre-load the rear springs. Derek added
>three spacers or donuts to each of his rear springs. His goal was to
>raise the height of the vehicle (ground clearance). From my dirt bike
>experience, I deduced that what he was doing was reducing the "sag
>height" of his syncro. Yes, this raised the clearance of the
>vehicle...but it did so by increasing spring rate, so that at every
>level of compression, the spring was stiffer, and hence the vehicle sat
>higher, than before he inserted the three spacers.
>
>If ground clearance is your only objective, then insert as many spacers
>as necessary to cause your suspension to be fully unloaded even when
>fully loaded, i.e., no "sag height." If you also wanted want your
>suspension to perform optimaly, however, you would not do this. If the
>springs are too stiff, they will inhibit the shock absorber's dampening
>action, on both the compression and upswing strokes. The result will be
>un-responsive compression dampening and bouncing up-swing dampening.
>This makes for a pounding and abusive ride. Even at low speeds, it
>unduly streesses other components. Your traction will also suffer
>appreciably in the wet/mud and the snow, and over fast rough stuff.
>
>My guess and experience suggest that the best shocks to use are the
>stock Boges, front and rear. I have not done any testing to determine
>the number of spacers or donuts to insert to obtain the optimum spring
>rate. thus far, I have inserted one on top of each rear spring. this
>set up is definitely better, IMHO, than the KYBs. The stiffer
>spring-rate adds firmness without sacraficing dampening. One spacer on
>top of each spring gets rid of the rocking and rolling, and provides a
>more stable ride, but it still allows the dampening of the Boges to
>abosrb bumps, without bouncing back too quickly on the up-swing stroke.
>
>For me, I am guessing that a spacer the size of the stock donut on the
>left front and rear, with a slightly thinner spacer on the right front
>and rear would be pretty close to optimum or a good starting point.
>Only through testing can you know for sure. Ideally, we would all get
>together and have someone build us each a set of shocks with adjustable
>dampening. This is more feasible than you may realize. Untill then,
>all we can do is play around with those spacers and see what we can come
>up with.
>steve
>1990 syncro westfalia
>
>
-- David Marshall, Quesnel BC, mailto:david@volkswagen.org --
-- 78 1.8L VW Rabbit, 80 2.0L VW Caddy, 87 Audi 5KQ --
-- 85 1.8L VW Cabrio, 88 1.6L VW Syncro Double Cab --
-- Volkswagen Homepage http://www.volkswagen.org --
-- USE DAVID@VOLKSWAGEN.ORG WHEN SENDING EMAIL --
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