OK, back at a desk..
Have you measured the roll centers on an 2-11?
Nick Adams said:
Measured at the wheel rim from a 100 F / 110 R base ride height the car has 19mm of bump and 44mm of droop at the front and 22mm of bump and 40mm droop at the rear. Now you can see why I get sweaty when people start wanting to drop their cars below 90mm ride at the front..... :lol:
I don't have Exige S figures to hand, but it has about 10-15mm more bump and simliar droop at both the front and the rear. Note that the Exige rides at 130mm all round, so at the same ride heights as the 2-Eleven it has almost no bump travel at all!
Nick
Yes, I have, and as I have said, they are exactly the same as all the 2ZZ engined Elises/Exiges.
Right, tyres:
I'm running Hoosier A6 tires
205/45/16 up front
245/3-16 rear
(I assume he means 245/40ZR17? or is he running 16" rears and 245/45ZR16?)
Looking up the spec's for them vs. the factory fit A048R's shows that the front will be ~10mm lower and the back 5mm (or 2 for the 16") - bear in mind this is from tyre spec charts so you have to treat them with a little respect as different makers measure in different ways and this does also not tell you what the effective radius is when the car's weight is placed on them etc etc.
Right, great, at least he's going in the right direction, (although they are pretty wide tyres for the std Lotus rim widths? - once again going on the tyre chart data).
Assuming he has the 'std' Lotus Ohlins, the fronts have only 55mm of stroke and the rears 65mm (both inc bump rubber space), ie bugger all.
Roughly speaking, it's about 1.37 and 1.34 (F/R) wheel to damper ratio (varies at the front depending on where you are as it's falling rate due to the angle of the damper).
so, on that basis, with 55mm of stroke, the limits of wheel travel will be Approx 75mm - reading Nicks post 19+44=63 so being kind and assuming he's discounting the use of the bump rubber, that's probably about right for the front, however, at the rear 65mm at damper = ~87mm at the wheel, and he's talking 22+40=62mm at the rear - way off (and if true would be hopeless, 22mm of bump travel is a joke).
Right, what I am getting at is that in std trim, the 211's with their Ohlins are just wrong, you don't really have enough damper travel (specifically at the rear), but worse than that, the window if that travel is at ride heights that just won't work.
just to put this in context, here's a picture of a 211 with the chassis on stands and the rear wheel at full droop:
as you can see, the rear wishbone is already past horizontal, imagine what it looks like at ride height...
this is what people mean when they talk about roll centres being below the tarmac, it's just wrong, the chassis (and I mean the chassis for *all* Elise variants) was designed for the cars having ~150-160mm heights, just dropping them down 60+mm without making some fundamental changes to the kinematics just does not work.
