No I am not saying that in such stringent fashion and am aware it's not always how science says it to be. But footprint is not so simply just LARGER with wider tires. It is directly related to the weight of the car on the tires.

For the most part tires do result in increased grip but it doesn't necessarily translate to the intuitive first-thought version, as you already know.

 

And yes, while the dynamic footprint aggregate area AND pressure does change due to weight transfer in the vehicle while braking, the width of the tire still determines the shape of the contact patch. The rears are also going to benefit from this less than the fronts under a braking situation.

That being said, I still recognize how it isn't so clean cut, but it's "generally" within the realm of physics.

Alot of the arguments in the thread referenced appear to revolve around surface area while not giving the same "weight" (excuse the pun) to pressure increasing grip (and not just changing contact patch shape).

 

For instance, you wrote:

That's assuming only area size translates to grip - which we know it doesn't. It all goes back to pressure which all goes back to vehicle weight per corner, yadda yadda

Friction is directly related to pressure and surface area. The previous statement only takes into account surface area when pressure is constant (no weight transfer example).

 

Where did Damon's original post go?

Huh?

 

I half understand what your saying clayne. I'm a fiber optics splicer by trade so all the "technical jargon" you've mentioned went up and over my head :P

 

I need 1000 ft pair of single-mode, layed pronto jspec. ST-terminated, get on it!

 

lol! I like the "FC" connectors better...just because it reminds me of RX7s.

 

-just ordered a Wilwood Prop valve today. Once i get some more junk sold outa the garage i will pull my FD in there and start in on it finally. Rotary revolution is march 30th-april 2nd i have to get hustlin fast Clayne buddy you comming?
Either way i think it will be cool because it might actually be the first time to have a V8-Rx7 go against rotary Rx7s on the 1/4, SCCA, and full road course. I know i wont be the fastest by any means, but i am very curious to see the results compared!
-highjacking my own thread, anyone have a 3.90 rear end gear seat? Will trade my 4.10 or buy outright...
-james

 

isn't abs binary? as in on off on off? how is that better than threshold braking?

maybe i just don't have a proper understanding of abs

 

On/off VERY fast.

Think of a light flashing very fast.

 

Got cut off...

at 110. WTF?

Please, for the good of mankind aim for poles the next time that happens.

 

no you don't.

ABS performs threshold braking several times a second -- faster than is humanly possible.

Not only that, but the ABS can perform individual threshold braking at each wheel (or in the case of the FD, each front wheel and both rear wheels together).

 

On/off VERY fast.

Think of a light flashing very fast.

 

damn forum

 

I had changed my mind about introducing the topic into this thread

I'm not assuming area size is the only thing that determines grip. You guys are WAY overanalyzing the problem and coming to the wrong conclusion. At minimum we agree that wider tires offer more grip in at least some situations, right? (I insist they offer more in ALL situations). Since the chassis and weight transfer is a constant that is not affected by tire size, how do you propose a wider tire would EVER have more grip than a narrower one when according to your theory the wider tire will always have less pressure over it due to its larger surface area? How does the wider tire see the same weight transfer as the narrower one in cornering and offer more grip, while also seeing the same weight transfer in braking /accelerating and NOT offering more grip? That is impossible! You're saying the tire somehow knows the difference in weight transfer between cornering and accelerating or braking! The contact patch shape has nothing to do with this!

Contact patch size is VERY fundamental. You put a larger tire on a car and you get more grip. The contact patch automatically gets larger just by bolting on wider tires. Do not concern yourself about pressure distribution over the footprint because this will lead you to the WRONG conclusions. Rubber does NOT obey the same area friction rules as other materials!

Perform the experiment below for proof that a wider tire automatically offers increased grip in every vehicle dynamic:

Take two pieces of the same type of rubber; one piece 3"x12" and another 6"x12". We will make the 3"x12" piece of rubber twice as thick so it weighs the same as the 6"x12" piece. Even though the two pieces of rubber have the same weight the contact patch of the 6"x12" piece is twice as big (does anyone disagree that the bigger piece of rubber has a greater area of contact?). If you were to place these pieces on a surface and measure their coefficient of friction by placing a weight on them and pulling with a spring scale you'd find that the 6"x12" piece has a higher cf in any direction you choose to measure. Even though the two pieces weigh exactly the same the 6"x12" piece has twice the contact area which results in it's increased coefficient of friction. This experiment is fundamental and irrefutable. No matter what other forces (tire pressure, weight transfer, download etc) you choose to add to the experiment you will find that under the same conditions the larger piece of rubber will have a higher coefficient of friction in any direction you choose to measure every single time! This is soley due to its increased area of contact!

I'll leave it at that in this thread. Further discussion should take place
here