Picking New Tires, Trying To Get More Front Grip

Red__Zed · 07-06-2015, 06:54 PM

Quote:

Originally Posted by MacCool

The basic equation accounts for adhesion as part of the coefficient of friction. Surface area doesn't matter.

Simply not true. What you are describing is the Coulomb model of Physics, not Physics. If you had any background in physics you would know that adhesion and deformation are two of the most standard cases to break you out of the Coulomb model. Your 7th grade Physics equation assumes "hard" solids - it's a terrible approximation of a tire, especially on a performance car, where you are using "sticky" tires and air pressures that allow for a good bit of deformation.

Quote:

Originally Posted by MacCool

The solution, obvious solution, to oversteering or understeering is suspension, not tires. I can't help it if your grasp of rudimentary physics is so lacking that these concepts are beyond your ability to understand. Public education apparently isn't what it used to be.

That's for sure - now they explain the limitations of basic models to junior high students. Go do some research on the adhesion and deformative components - you can find a start on Wikipedia, but any modern Physics textbook will get you up to speed here.

Here's a relevant quote to get you started:

Quote:

When the surfaces are conjoined, Coulomb friction becomes a very poor approximation (for example, adhesive tape resists sliding even when there is no normal force, or a negative normal force). In this case, the frictional force may depend strongly on the area of contact.

Quote:

Originally Posted by Jordo!

Hmm. I was going to suggest a square set up as well, but really in order to keep tire size and compound a constant more than to play with relative grip -- a lot of that will depend on alignment settings and weight distribution/suspension more than anything.

I guess you could buy ultra sticky fronts relative to the rears, but that sounds like it will just make the car unpredictable...

So, assuming equal sized tires of same make, you want to stiffen up the rear relative to the front. That means a beefier rear anti-sway bar and firmer damper settings in the rear and softer in the front, if you can adjust them. Any other bracing you can add to the rear (without adding significant weight) will tend to nudge you more towards oversteer.

I think, maybe a little more camber in the front relative to the rear will help tuck the nose in too... not 100% certain on that one off the top of my head.

Scan over this site for lots and lots of advice on setting up cars for road racing

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This thread is helpful too

Suspension adjustments and how they affect handling

Points are true in general, but the Z tends to have more issues with stiffness up front (depending on tire selection), and not need a whole lot of help in the rear. The additional camber up front is very important. The Z runs best with 3+* of camber and a bigass bar up front from what I've seen - all the really fast guys have a Hotchkis bar and as much tire as they can get up front, preferably with a stiff sidewall. There's already a ton of stiffness out back on the Z, and a stiffer rear bar doesn't do as much for you.

Rusty · 07-06-2015, 07:20 PM

Here I am of thinking on going with 305's in the front to go with my 345's in the rear in search for more grip.

Now I'm going to have to rethink everything. Maybe I'll start a new trend by going with 145's in the front and 155's in the rear.

07-06-2015, 07:20 PM	#2 (permalink)
Rusty A True Z Fanatic Join Date: Dec 2011 Location: Fayettenam,Pennsyltucky Age: 70 Posts: 35,575 Drives: 2011 Nismo GM 6M Rep Power: 2684440	Here I am of thinking on going with 305's in the front to go with my 345's in the rear in search for more grip. Now I'm going to have to rethink everything. Maybe I'll start a new trend by going with 145's in the front and 155's in the rear. ScottOmatic, Spooler, Memphis370Z and 1 others like this. __________________ 浪人 - 殺し屋 "The Difficult Anytime, The Impossible By Appointment Only" http://www.the370z.com/members-370z-...o-journal.html

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