At 08:07 AM 11/22/99 -0800, Jay wrote:
Again I apologise if my timing is late - Digest only for me!
>If you start with tires that are much larger than optimum for the car's
>mass, the effect of the nonlinearity may still not be that great.
Enough to measure. Enough that I'd want the half weight car.
>> Ever wonder why "wider wheels/same tire compound" always gives
>> higher skid figures?
>
>Always? I've seen the opposite happen (admittedly in rare
>circumstances).
On What? Just curious. It would have to be a REALLY bad suspension
geometry to screw up a skid pad.
>> It is due to the non linear ness of the CF figure.
>> Which is why everyone tries to run wider wheels in SP over stock.
>
>Ever hear of "steering response?" That's as strong a motivation to go
>wider/lower profile as steady-state cornering. Autocross has relaitvely
>few steady-state features and lots of transient maneuvers.
Lower profile is a different issue, IMHO. Yes, lower profile does affect
steering response. As does shock settings, springs, sway bars, sidewall
stiffness/design and tire design.
But my argument is that the major benefit of wider wheels/tires is a higher
tire grip.
>> If the CF were truly linear then there
>> would be no advantage to a low CG on a skid pad.
>
>As I pointed by implication out earlier in this thread.
I think we are really agreeing on the basic points here. I'm
sorry if I didn't understand the gist of what you were trying
to relay.
>No argument there. However, it is not true that a car's cornering
>capacity decreases in direct proportion to increases in weight, even if
>the tire sizes are the same.
;-) ;-) ;-) ;-)
It is really tough sometimes to discuss something on the internet. I
guess I'm struggling with the nuances. As you wrote the statement
above, it follows my understanding. But if you are emphasizing the "direct
proportion", then I'm thinking that a better way to write teh statement
would be to say:
"It is TRUE that a car's cornering capacity decreases as weight is added",
which may be exactly what you meant, but which I missed when reading
your post.
>My autox car weighs 1330 lbs and has 8" rims with 225/45 tires, and I've
>gone to quite a bit of trouble to get it as low and as light as
>possible. Over the winter, it's getting lower still.
My car is a 2300 pound behemouth with 7 inch wide wheels. I got LOTS of
power, great transitional, but no steady state and crappy 60-0 times. I
personally think that there are more steady states then most people think.
Which is why wings in A-Mod are so effective and CP guys are willing to
widen their cars to get more rubber on the ground.
-Doug Miller
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