John/TSR

We didn't want to 'get back to the point', since for many/most of us, it's irrelevant. We race cars that are limited, in some way, as to the width of tires we can run.

Tomasz@Startup

Ha! This is very interesting, as I did not know this before. Thank you.

FixedWing

Yes, very interesting. :-)

Mark Dalen

You said:
"Does a wider tire (every thing else being equal) have a higher frictional force? Duh, yeah, absolutely."

Not necessarily. With a soft tire (racing tire) the rubber deforms and 'grabs' the surface irregularities. A narrower tire has higher pressure on it and will deform more. That can actually cause a narrower tire to have more grip that the wider tire. THIS IS ONLY IN SOME NARROW CASES but the point is that you can't generalize about what creates more grip.

Now add the real world of heat. A narrower tire will get hotter. If you have a fairly light car, you can add enough tire so that you fail to get enough heat into it and get lower grip with the wider tire than with a narrower choice.

Here is a real world puzzle. When I had my Radical (2 seat) I would lose ~2 seconds per lap by carrying a passenger at most tracks. Pahrump was no exception. Except one cold day we were playing and struggling to get grip due to the low temps and the failry hard compounds. On that day, I could run the same lap times with a passenger or solo. So here is the puzzle. Why was the car just as fast with an extra 200 lbs as without? Things often do not work as expected.

Mark Dalen

Yes, with similar tires I beleive that the wider tire will give a larger contact patch. But, if you read my post below (from tonight) I do not concur that always results in more grip.

Within limits, wider gives more grip, but you can easily fall outside those limits in the real world. BUT, more grip is not always good. More grip in corners means you go faster. More grip down the staights means you have more drag and go slower. Keep putting wider and wider tires on a low powered car and you will see lap times get slower after ther optimum point.

Tomasz@Startup

Good discussion. Thank you.

ryoung

Did you measure tire temps with and without the passenger?

Mark Dalen

Exactly. With the extra weight, the tire temps were higher and there was more grip which offset the negative of higher weight.

Just an example of how things don't often work the way we expect in the real world.