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All this talk of dropped spindles and caster angle changes motivated me to revisit my little engineering/geometry exercise from awhile ago. If you have visited my website and the lowering section, you know that I measured all the suspension geometry and did some calculating. It showed that the caster does indeed decrease with upward suspension travel (non-parallelogram geometry). However all was not rosy since the numbers really didn't make much sense overall. They showed a designed-in negative caster at normal suspension positions. Certainly not the case. Anyway, for all the details from last time visit my site. So what did I find this time. I went back with a bubble level protractor and remeasured the angle of the tunnel relative to horizontal and the angle of the beam mounting plane relative to horizontal. The one assumption I made is that the design position of the car is such that the tunnel is horizontal. Compensating for the position of the tunnel resulted in a built-in angle at the frame head of 13.2 degrees. (BTW, this is considerably more than my original calculation of 9.1. Maybe I did miss it by nearly 50%). So with the varying thickness of the rubber isolators added in, the total caster built into the beam mounting is 14.1 degrees. Now the trailing arms.... The lower trailing arm has an effective length of 7 1/4" The upper trailing arm has an effective length of 6 3/8" The pivot points at the ball joints are 6 7/8" apart The pivot points on the beam are 6 1/2" apart. Certainly not a parallelogram! Laying all this out gets a 4 degree caster angle at the spindle (where it matters) when the lower trailing arm angle is about 10 degrees above horizontal. Looking at Sophy this seems about right. It also means about 2 1/2" of travel before you get to 0 degrees of caster. Again this is about right since this is when you are getting into the bump stops. Anyone know what the upward travel of a stock ride height Type 3 is supposed to be? All this also means that with a 3.5" drop you end up at about 3.5 degrees of NEGATIVE caster! And this assumes that you have lowered the rear an equal amount. If not, you can add another 2.1 degrees (arctangent of (3.5 inch drop/94.5 inch wheelbase)) of negative caster for a total of over 5.5 degrees of NEGATIVE caster. Not good. So, where do dropped spindles fit into all this? If the car is lowered only with dropped spindles in the front and an equivalent amount in the rear the suspension geometry and ride quality will not change. Lower just the front with dropped spindles and leaving the rear at stock ride height WILL result in a caster angle change for the NEGATIVE. Lower the front by indexing the torsion bars WILL result in a change to the caster angle for the NEGATIVE. This is compounded if the rear is left at stock height. Want it lower than dropped spindle alone can get you but want to maintain positive caster angles? Do what VW did. Vary the thickness of the rubber isolators. Moving 1/10 of an inch of rubber from one side to the other of the beams buys you 0.9 degrees of caster. Just make sure you do it on the proper side. For my money I would look a the upper isolator. It has the simplest geometry and is uniform thickness of 0.45 inches now. Get yourself some 0.15 inch thick rubber sheet. Cut the isolator in half. Use the front half and 2 layers of sheet stock in front of the beam. Use one layer of sheet stock by itself behind the beam and you have effectively bought 2.7 degrees of caster. I would try super-gluing the layers together to make sure they don't move. My guess is that the ride will be a bit harsher since you now have less isolation between the tunnel adn the beam, but that is the price we have to pay. Comments/suggestions/independent verification of measurements welcome. If anyone tries this, please let me know. Just my engineering 3 cents worth. Maybe a bit more. Later, John Jaranson '71 FI AT Fasty (Jane - Darkside Project) '66 Square (Sophy - Daily Driver) About Half a Late Square (Organ Donor) http://mywebpages.comcast.net/jaransonT3/jaransonT3/ http://mywebpages.comcast.net/jaransonT3/notavwclub/ ------------------------------------------------ To unsubscribe, E-mail to: <type3-off@vwtype3.org> For more help, see http://vwtype3.org/list/