mark kibort

those that us that are students of the sport and been doing this a long time, have a lot of empirical evidence. cooration of that evidence is the challenge.
I agree, it all looks simple at first. but when you start running the numbers, things change quite a bit.

for you , i would ask that you put down on paper here, what those numbers are so that your results can be seen. you have seen my calculations. if you dont see those same results, something has to change.... the only real variable of significance is the tire mu factor, that changes with the tire loading sensitivity.
i still am having trouble seeing how that is incorporated in your analysis. right now im working on looking on what Scott put together (cornering has a few more variables for sure).. longitudinal , though related, is much simpler.
again.... as far as empirical evidence.... correlation doesn't constitute causation.

ProCoach

"Correlation does not imply causation" is what I think you meant, Mark.

Words matter!

outline

I never said it did. They are quite distinct concepts.

winders

The numbers would be exactly the same. All of them. You still don't see what is going on. If you did, you would know the answer to your question.

If there were no such thing as tire load sensitivity, adjusting roll couple distribution would have no effect on chassis balance.

mark kibort

yes....thanks.... that was a substantial correction.

Interesting enough, from the school of Oxford, they used what i said.. but what do they know, when a huge semantically based arguer is present!!

But, yes you are right.... I did mean "imply". I was just writing down my thoughts as i sometimes do!


From Oxford excerpt:

15, 2013 - ... slogan in statistics is that correlation does not imply causation. ... But do even these, sometimes weak, correlations constitute causation?.......

http://blog.oup.com/2013/11/correlat...not-causation/.

mark kibort

Actually you said exacty that. as Peter said.... "words matter" ha ha ha.

you said,

so again," coorelation (i.e. empirical evidence) doesnt imply causation (results of your model)"

However, i am interested if you can put down a few numbers to see how it can be different than what i had calculated.

mark kibort

Scott, ill admit... im not getting it then. I think i might be looking at it from another POV. I still lean to think that.................ah, wait a min.... are you talking tire load sensitivity, or proportional tire force based on increased mass? if so, we are are not talking about the same thing... tire load sensitivity is the ratio of increased load to increased friction forces. This might be the confusion.

winders

I officially give up......

mark kibort

It would be great to have you provide the answer, instead of the put downs. I know you find joy out of being condescending and feel superior by putting someone down, either for not knowing the answer, or not understanding your point.
I could care less about any of it. I find your position interesting and Im trying to understand your point or the answer. And maybe, those are one and the same and we all (or at least me) will learn something.
Everyone knows handling concepts are the most complicated in racing, and this discussion (I think) is good.

mark kibort

How is this possible scott, because if there was no tire load sensitivity, increase vertical load would be equal to friction force.

I don't see how if this small factor of tire load sensitivity was not a factor, how adjusting roll couple distribution could have 0 effect on chassis balance.

Help me understand!

mk

From wiki :
Tire load sensitivity describes the behaviour of tires under load. Conventional pneumatic tires do not behave as classical friction theory would suggest. The load sensitivity of most real tires in their typical operating range is such that the coefficient of friction decreases as the vertical load, Fz, increases.



Example[edit]

As an example, here is data extracted from Milliken and Milliken's "Race Car Vehicle Dynamics", figure 2.9:

Vertical load
(lbf)
900 1.10
1350 1.08
1800 0.97

winders

Mark,

Discussing this stuff with you is like:

First of all, "tire load sensitivity" is not "the ratio of increased load to increased friction forces". The phrase "tire load sensitivity" is the name for the phenomenon that is the behavior of tires under load. Grip lost or gained due to "tire load sensitivity" not a ratio either. It is a curve and the shape of the curve varies amongst tires.

One facet of the "tire load sensitivity" phenomenon is that a tire adding load loses grip faster than a tire subtracting load gains grip. This means that two tires in a system (on an axle) generate the most grip when the two tires are evenly loaded. Any load transfer that moves away from that 50/50 distribution negatively impacts the overall grip those two tires provide. The further you move away from that 50/50 distribution, the more severe the reduction in grip. So, a two tire axle with 75/25 load distribution generates less grip than the same two tire axle with a 60/40 load distribution.

The above is how "tire load sensitivity" comes into play with anti-roll bars and roll couple distribution to affect chassis balance. Read post #100 again. Look at what happens to the front and rear axles when we soften the front anti-roll bar. Which axle has the load distribution closest to 50/50. Which axle lost grip and which axle gained grip?

Without "tire load sensitivity", adjusting roll couple distribution would have no effect on chassis balance since each axle would handle its load over its two tires the same regardless of actual load distribution and the grip on each axle would remain the same.

winders

Huh? If the vertical load increase came along with an equal gain in friction force (i.e., no "tire load sensitivity"), how could changing roll couple distribution affect chassis balance?

mglobe

Can someone please summarize and tell me what the score is?

DTMiller

You can add all the weight to your car you want, won't hurt braking performance. So add that mini fridge.

2BWise

Good question. Especially as it pertains to aero forces. I wouldn't use the same wording, but that is a basic description of why wings work.

It's what makes this sport so interesting.