strut rebuild/lowering PART 2, continued

  there has been an idea in the back of my head to try installing the new struts with the shorter KYB insert without the adaptor stub, and just reposition the lower perch/spring seat to wherever it needs to be to give a reasonable amount of preload...after a couple days of mock-ups and lots of measuring i can safely say that its not going to work. i've already read this in (many, many) posts on the forum, but i needed to find out for myself, i guess. 

illustrated:

 

OEM damper              KYB damper

  that long, unthreaded section of the OEM damper is to accommodate the massive bump stop bushing/mount and the complete strut bearing/mount...an extra 85mm. the total difference in overall length between the two (in terms of the fully extended shaft) is 60mm. however, the KYB has a greater length of bare shaft (in other words, the shoulder where the threads start is a greater distance/length from the top of the cap): about 18mm. 

  since i plan on boring out my upper spring plate and using the Mazda thrust bearing, the amount of threads/shank i need is considerably reduced; the shoulder will contact the inner race of the strut mount. that effectively eliminates the bump stop & its bushing because it has no shoulder to rest on anymore. that also reduces the distance between the spring seats by at least 70mm (the combined measurements of the bump stop depth, the bearing skirt depth, and the thickness of the spring plate and Mazda bearing). thats a very rough estimate, though, since i dont have the Mazda bearing yet to measure. here's what it would look like:

 

OEM                            KYB

  anyway, regardless of spring seat spacing, its the distance between the mounting at the body and the axle of the car that determines ride height. or rather any fixed point on the strut body (such as the top of the cap...thats what i'm using) and the shoulder that contacts the strut mount. slight differences in the style of mount (symmetrical vs. asymmetrical) or height of the cartridge ( how close to flush it is inside the strut body) can give some variance, but only very small amounts. so... to test this dimension i set up one of each, as shown above, and measured between the top face of the mount and a fixed point on the body (this time i used the notch on the lower perch because it was a straighter line): 113mm (4.5")! so that means over four inches lower in the front... waaaay too much. 

  so its back to the drawing board... i'm going to have to have the stub made and just be certain of its measurements...right now i'm thinking about having an integrated shoulder for an aftermarket bump stop/bellows. also, i wonder if stainless steel would be tough enough for this kind of service...i had figured on something like tool steel, but theres the rust issue to consider...