max width for s2k guards

[AusS2000]

Hey, at least I can form a coherent sentence.

[AusS2000]

Here ya go:

It's inaccurate to assume that as the section width or tread width increases that the contact patch area also increases. Nor does it remain constant as [Vertical Force] / [Constant Inflation Pressure] suggests. Conceivably, it could decrease depending on the relative vertical stiffnesses. But what will change is the shape of the contact patch, becoming shorter in the longitudinal direction as it is made wider (assuming a constant load), and this may be partly responsible for more uniform unit loading over the area of the contact patch. All else equal, integrating a more uniform unit load and associated grip coefficient function over the entire contact patch should give more total lateral grip. The wider tire probably also has higher vertical and lateral spring rates, meaning less camber loss and lateral distortion in actual driving respectively.

BTW, the drag strip crowd tends to run tires that give relatively longer contact patches . . .

From here:

http://www.eng-tips.com/viewthread.c...=102250&page=1

[AusS2000]

BTW, my S came with 225s on the rear and I'm now running 265s. So it's not like I'm not speaking from experience.

[robert112]

okay well im going to take your approach to this for ' ye what ever u know best '...
I can't give you any article that proves my theory buddy all I can give you are Time slips from wedesday nights and freaky friday events at Eastern Creek WSID of how my times get over 1 second faster with fat tyres as opposed to skinny ones...

You obviously have never driven a 12 second or faster car down the 1/4.

and according to you, the s2k needs more grip on the front of the car then it does on the back so that means its a car very prone to understeer? <insert sarcasm here>

also.... lastly if you read your own article you would see not everyone (example: GregLocock and patprimmer and a few more) agrees with the topic starter.

example:GregLocock said:

In theory for a given tyre wear you could have softer rubber on the wider tyre which should improve the dry weather grip. I suspect this is a small effect.
Cheers

Greg Locock

and patprimmer said:
patprimmer (Automotive) 29 Aug 04 2:26
I am not the most qualified to comment on this, but in my experience and from what I have gleaned from more qualified people, wider is generally better re grip, but there are several qualifiers.

edit*

Greg Locock also said:

just went to a presentation by a big tyre manufacturer, they are very insistent that in the dry, for high performance handling (ie grip vs wear, basically), wider=better.

All tyre design is a compromise, the more real estate you've got to play with, the better that compromise will be.


Cheers

Greg Locock

dude the thread is basically agreeing with me and not you, did u evne read the thing or did u just agree with the topic starter and close the window? *shakes head* ur wasting my time im no longer replying to this.

[AusS2000]

Now, now, keep your panties on. Yes I did read the thread. And I realise it is a logical opinion in agreeance with mine and bunch of ricers arguing against it like you.

Have I driven a 12 second car? Daily. Down the 1/4? No, most of my races last slightly longer than that.

and according to you, the s2k needs more grip on the front of the car then it does on the back so that means its a car very prone to understeer? <insert sarcasm here>

Yeah, you're just being a dick there. The S is prone to oversteer in corners hence the wider tyres at the rear. They are wider for lateral grip.

shakes head* ur wasting my time im no longer replying to this.

Is that a promise? I doubt it.

Look, it's a very simple fact that if a car weighs 1200Kg and is evenly weighted there is approximately 300Kg per wheel (forgive the rounding, I don't want to make it too complicated for you). At 32psi (2.25Kg/cm2) the contact patch is 133.3sq.cm. Increase the pressure to 36 and it reduces to 118.6. That is regardless of the width. All that changes is the shape. And if a tyre gets wider then the contact patch gets shorter. If you can fault the physics let me know.

Of course this is all static. As soon as you launch on the drag strip or brake at the end of a straight (in real racing ) the weight shifts aft or fore (respectively) so things increase or decrease accordingly. But the logic is still the same. Wider equals shorter (within realistic limits).

One of the questions in that thread is "if wider ain't better why do race cars have wide tyres?". The answer is really simple. You make up more time in corners (you've heard of them?) than in the straights, and wider contact patches are good for corners. You'll also notice where they comment that drag racers (the real ones, not the rice mobiles) have quite narrow tyres in relation to their diameter.

As for why your timeslips are better with wider tyres, there are probably a number of factors. Most street modified cars, and the S2000 in particular aren't very torquey. So rather than a full grip start you get the engine and wheels spinning and modulate the grip. You probably find that with wider tyres (less longitudinal grip) you have more control over the slip. Another point is that your drag tyres are probably a much different compound to street tyres. I use RE55s on the track (I think they are a 225 or 245) and a 265 on the road. Sure the RE55s have more grip, but I doubt that is just because of their width. They are a soft sticky compound.

We've both been a bit of a dick in this thread. You may not agree with me, and I certainly think you're full of sh!t but I've got nothing much more to add. Let the punters make up their own mind.