A perspective for ponderings about the balance, understeer, trail braking, abs behavior on our Spyder/Roadster:
The Front/Rear weight distribution:
MR2 43/57%
Elise S1 38/62%
Weigth:
MR2 1000kg
Elise S1 750kg
Front wheel load:
MR2 215kg
Elise S1 142.5kg
Front tyre:
MR2 185/55 x 15
Elise S1 185/55 x 15
The Series 2 btw. was a redevelopment to meet the same 2000- crash requirement the MR2 Spyder was designed to meet, thus the best comparison model.
The Series 2 weighed 860-910kg. with three engine outputs; 122, 138, 192 hp.
Same weight distribution,
tyre load 163.4-172.9kg.
tyre size 195/50 x 15.
Now take note of
http://www.morpca.org/drivers-education-guide/understeer-oversteer/
Ergo, less weight up front, less tyre load redúces understeer. Nor does it cause abs overkill.
The straight line ´instability´ at higher speed is a different issue with different causes/solutions.
All of the above is in line with the MR2 being intended for a broader public than the Elise and as such set up for more understeer by Toyota.
Note the key footnote:
´A properly set up vehicle will usually push slightly on corner entry, be fairly neutral at the apex (STEADY STATE) and exhibit slight power oversteer on corner exit. Tight courses may require more oversteer, fast tracks more understeer.´
Steady state means no braking, just enough throttle to maintain corner speed.
A typical roundabout counts as a tightish corner and a properly set up car will have a tendency to understeer there.
The MR2 is set up with a tad more understeer than ´properly´.
To be fair, it's more nuanced than you have described. Suspension geometry, spring rate, bound and rebound compression damping and ARB stiffness all play their part.
I only experience understeer at very low speeds. The rest of the time it's set up to be neutral to slight oversteer at medium and high speed corners.
Quote from: Alex Knight on October 10, 2019, 11:56To be fair, it's more nuanced than you have described. Suspension geometry, spring rate, bound and rebound compression damping and ARB stiffness all play their part.
See the list.
Furthermore I wrote no law of physics; gave perspective for ponderings.
The underlying point I want to make is that less load up front does not equal less grip or more understeer.
But yes, it is more complicated than just weight. Given the car though. and the things we can changes, it kinda is.
Understeer can also be rephrased as the tyres not changing the direction as much as they turn.
The two forces involved are the friction between rubber and surface, proccessional force (directional stability), centrifugal force. When the latter two exceed the friction availeble the tyre doe not follow the direction it is steered into.
QuoteI only experience understeer at very low speeds.
More accurately; taking a corner so tight that the for this radius high speed pushes the front of the car.
The understeer occurs at high turn rates. It is thén that the precession and centrifugal forces win out.
I want to add that going downhill through hairpins the tight corner (low speed) understeer gets more prominent.
For the rest; do with it what you like; happy ponderings :-)