Lotus Elan

Original or rear double wishbone suspension for track days

PostPost by: roadterror » Tue May 11, 2010 5:43 pm

Hi, anyone have experience with Spyder's rear double wishbone suspension on the track? Am I better off with the original set-up? Have full CV conversion, 13" KO Plus 2 alloy wheels. TIA.

Cheers,
Brian
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PostPost by: elansprint71 » Tue Jun 01, 2010 8:31 pm

Looks like nobody is running this set-up on the track (not legal in any racing series that I know of, but what do I know?).

I've got it on the road and one of the factors I did not take into consideration was that, under severe cornering load, i.e. "normal Elan driving" there is a possibility that the shoulder/side-wall of the tyre can come into contact with the inside of the wing flare (S4 style). I shaved the returns on the wheel-arch flare, beefing up the edges by filling in the resulting "groove" but the tyre can still touch the sloping inner part of the flare. The reason for this is that, with the twin 'bones, the up and down movement of the suspension and wheel is nearer to vertical than the stock set-up, where the wheel tucks neatly inboard as the suspension compresses.

I'm running 6 inch wide Minilites and 175x70x13 tyres, btw.
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PostPost by: rgh0 » Wed Jun 02, 2010 11:52 am

175 x 70 x 13 on 6 inch wheels would be a challenge on a S4 with the standard Lotus suspension and would normally require careful offset selction for the wheels and filing of the lip on the wheel arches.

Sounds like the Twin wishbone suspension has simillar and maybe slightly greater challenges.

The Lotus suspension works well in practice on the track with the right mods to spring rates and dampers to match modern sticky tyres. The camber changes inherent in the Lotus suspension are acceptable for modern tyres I believe. I have never done any controlled back to back comparision with the Spyder rear suspension but any possible handling improvement would be small I believe versus an optimised orginal Lotus setup.

cheers
Rohan
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PostPost by: elansprint71 » Thu Jun 03, 2010 8:37 pm

rgh0 wrote:175 x 70 x 13 on 6 inch wheels would be a challenge on a S4 with the standard Lotus suspension and would normally require careful offset selction for the wheels and filing of the lip on the wheel arches.

Sounds like the Twin wishbone suspension has simillar and maybe slightly greater challenges.

The Lotus suspension works well in practice on the track with the right mods to spring rates and dampers to match modern sticky tyres. The camber changes inherent in the Lotus suspension are acceptable for modern tyres I believe. I have never done any controlled back to back comparision with the Spyder rear suspension but any possible handling improvement would be small I believe versus an optimised orginal Lotus setup.

cheers
Rohan


Absolutely agree Rohan; I used the twinny set-up because it came with the Spyder chassis I purchased, via an intermediary owner, from a bloke who had not read the racing regs before he built his car, he took the Spyder chassis out after about 6 months, although the twinny bones had not been fitted, for some reason.
With the standard suspension and my chosen wheel/tyre combo the critical point is when the tyre passes the lip of the wheel-arc, with mine, not only is there that problem but it then meets the angled inner side of the flare. My Minilites have as much of the bulk inboard as possible, which is OK with the skinny springs.

Having discovered that Lotus managed to fit the body of my car with a 15mm skew to the chassis, at the rear wheels, when they originally built it, I was very careful to align the two properly during the rebuild, as I knew that there would be clearance issues.
The result of all this is that I have had to set the suspension a bit higher than I would have chosen, also I have had to do height adjustments to make it work which have resulted in less than optimal corner weights. As I'm just a road user, this is not a big deal for me.
With the improved supply situation for "original design" parts, I would go that way next time.
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