Leaf spring

[starman]

Richard_B wrote:

Now the question I have is; What spring (and rate) should I fit to a Spitfire MkIII with Rotoflex wishbones, vertical links & CV driveshafts?


Spitfire MkIII or GT6 MkII or a decambered GT6 MKII


A Standard GT6 MkII is too high, a 3/4" lowering block helps.

Hi Richard-

I've got the same question myself because I'm building up a Spitfire mk3 body on a GT6 mk2 chassis with a 2.0 liter 6 cylinder engine, substituting Canley's CV driveshafts for the rotoflex ones.  I'm planning to start out with a factory stock 185 lb/in GT6 mk2 spring that I have on-hand, and suspect I will need a lowering block with it as you've found.  May be worth trying a de-arc'd GT6 mk2 spring to reduce the thickness of the lowering block or eliminate it altogether.  I don't plan to use a Spitfire mk3 spring because it has a lower rate of 166 lb/in and I'll be stiffening the front and don't want too much of the total stiffness up front, thus engendering too much understeer.  An alternative I would like to try is a GT6 mk1 spring, which is 305 lb/in, but it will likely require an overly-thick lowering block to get the ride height I want, so I assume I will need to de-arc it some so that I can fine-tune with a reasonably-thin lowering block.  Of course this will add more rear roll stiffness vs. the GT6 mk2 spring.  I'd also like to try a swing spring since it provides a lot of vertical stiffness yet less roll stiffness (I've directly measured ~320 lb/in of vertical stiffness on proper Spitfire swing springs).  Laurence Cochrane (Gt6s) uses a hybridized swing spring on his modified '72 GT6.  It has a multilink IRS based on the rotoflex arrangement, but uses sliding shaft driveshafts instead of rotoflex ones, and I hear that this setup performs quite well.  

[G.in_Lux]

Hypoid53

google "Mike Sanders Grease tape".