Im looking at wheels for my GSR - which will soon be Turbo. My goal is maximum traction to put all the power down. I already have a Quiafe and full suspension. I will be getting some radius arms soon.

My question is about wheels and tires.
I want to get the SSR Type-C's (Competitions) which offer a 16" and 17" for the GSR - and offer both sizes in a 7.5" width. Would a 17 x 7.5 offer a larger contact patch than a 16 x 7.5?

And I should be able to use the same width tire on either correct? say a 225?


Modified by Muckman at 10:57 AM 6/12/2003

 

The wheels don't make contact with the ground, the tires do. What tire sizes are you going to use, and will the overall diameter be the same?

The contact patch is a function of the force upon it divided by the pressure (pressure x surface area = force). With the same overall diameter, the contact patch does not change in area, only in shape. A wider contact patch is better because:

1. pressure exerted onto the ground at the direct bottom of the tire is maximized. As you move circumfrencially (is that a word) up/down a tire, there is less force exerted on the tire from the weight of the vehicle, until the tire is no longer in contact with the road. This means, that if your c-patch is wide then is is entirely closer to the bottom if the tire, => a larger normal force => more friction.

2. Since you are a drag racer, a wider contact patch is better because of #1 and because a road isn't perfect and a wider patch gives a wider grip plane.

3. I ask if they are the same overall diameter because then a wider tire has a shorter sidewall (to keep the aspect ratio the same) and the shorter sidewall is stiffer (ideally) and will not rollover such that the c-patch is as close to its static size as possible.

Most people suffice to say that a wider patch is better for cornering, and I believe that is because of how the rubber displaces...

BTW keep quiet about the drag racing stuff...

 

I asked a very simple question and quoted mathmatical formulas and theory - and you never answered my question.

Heres the question again in lamens terms.
Two wheels, both with the same width and the same width tire
17 x 7.5 and 16 x 7.5

As you can see both wheels have the same width of 7.5" and therefore both can support the same width tire, say a 225mm width (as I said in my first post).

Would the larger diamater (17) wheel with the same tire width give a larger contact patch than the smaller diamater wheel (16) wheel with the same tire width? Given that all other variables are the same.

Does diamater play a role in tire contact patch?

*Edited for politeness


Modified by Muckman at 3:28 PM 6/13/2003

 

Deleted post at request of thread initator. Problem resolved.


Modified by allenp at 4:52 PM 6/13/2003

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Muckman &raquo;</TD></TR><TR><TD CLASS="quote">I asked a very simple question and you wrote an entire book quoting mathmatical formulas and theory - and you never answered my question.</TD></TR></TABLE>

You asked a poorly worded question and I told you why I needed more information. You only mentioned wheels in your original post, before you edited it, and I assumed that you could use some more information.

*Edited*

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Heres the question again in lamens terms.
Two wheels, both with the same width and the same width tire
17 x 7.5 and 16 x 7.5

As you can see both wheels have the same width of 7.5" and therefore both can support the same width tire, say a 225mm width (as I said in my first post).</TD></TR></TABLE>

Like I said, you only need to speak in terms of tires. There's no need to mention wheels. The wheel widths only affect the shape of the c-patch during sidewall deformation.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Would the larger diamater (17) wheel with the same tire width give a larger contact patch than the smaller diamater wheel (16) wheel with the same tire width? Given that all other variables are the same.</TD></TR></TABLE>

Well my first response is going to be, do you realize that (since like you said all tire aspects are the same except diameter) that these tires will change your overall gearing?

...on to the question...

Does diamater play a role in tire contact patch?

No. It is determined by the original equation I posted. The contact patch is a function of the weight of the car and inflation pressure of the tire (psi = pounds per sq. in.). The weight of the car and the tire inflation pressure have not changed.

Edit: I got this in before the politeness check, so understand that I was relatively angry.

Edit2: I'm no longer angry =&gt;



Modified by GSpeedR at 5:06 PM 6/13/2003