I'm not that familiar with de dion setup but yes, considerably softer on the rear, mainly to help with traction and kerbing. Another thing is weight - a stripped LA car is probably 35-40kg lighter than a typical early de dion and I'm guessing a race S2 will be lighter still. Mine is under 540kg with (light) driver and half a tank. Late on Caterham did supply progressive springs for live axles and that might be worth exploring. Maybe have a word with ProComp Motorsport who have a lot of experience with light (7 type) live axle cars. They may also be able to supply steel dampers in matched pairs valved to suit the weight or dyno and revalve stock dampers. Caterham stock dampers are not, from my experience, matched or sensibly valved for lighter cars. Ride height at 100mm sounds too low - I'd worry about the 'box and sump (if wet) and want to stay well clear of kerbs at that. As you say, no adjustment on the front so there's also the question of rack height and how much you'd need to lift that, particularly if running very low. Can you at least use the negative camber lower wishbone?
Judging by the way S2 Lotus Elevens run a lot of negative camber in historic racing (when they had positive from the factory with essentially the same set up as the early 7s) I'd guess standard wishbone lengths are not known/checked by scrutineers?!
I'm looking at changing the geometry on my S1 (for road use) and I'm thinking of just getting some wishbones made up to my spec with increased camber and castor, as they aren't particularly complicated items. If I increase the distance between the inner ends I can use washers to adjust castor as on the later cars.
Thanks all. rkeywood yes I agree 100mm is low but there is an idea afoot to possibly shorten the sump to match the height of the bell housing (which cannot really be changed) as a part of alterations for baffling, since it must stay wet, the modification would include some means of retrieving the lost oil capacity shortening would incur. Even so 100mm will probably be risky low 110/115 being more likely. I plan to have a minimum of 65mm below sump (which is the critical measure) for track.
I'm talking to IG Racing about (limited) choice of steel dampers and he favours Gaz believing these have superior seals over others. Also he sources them in component form and builds the up to his quality control and your spring/valving requirements.
The HSCC regs require an individual 'passport' issued post inspection, which is a separate issue to regular scrutineering. Rumour has it running over the car with a magnet is to be expected.......
Paul, I like the idea of different wishbones but I fear that would fall foul of the Passport/regs process, I have a feeling the days the 7's cleaning up are fresh in their memory and they don't want it happening again!!