Wider rear tires/wheels then front, Why?? Options

[Jetsetsurfshop]

Ive been running a "square" set up for years. 15x7 with 205/50/15 Hoosiers.
I'm now contemplating running wider rears then fronts and started to ask myself why? At the HSR races all the 914 guys are staggered. It looks like the PCA guys stagger too.
Whats the performance advantage here? Is it handling? Something to do with getting hard on the brakes? Putting the power down? Fitment on the front suspension?

Teach me something.... (IMG:style_emoticons/default/beerchug.gif)

[ThePaintedMan]

Shane,
This is a really cool site which explains what's happening with the tires very well. Maybe even a little too detailed in some ways.

http://racingcardynamics.com/racing-tires-lateral-force/

Here's what's important, in my understanding - remember that the tire reacts in three dimensions - X,Y,Z in side forces (yaw), acceleration and in vertical loading. If you look at a tire in terms of contact patch, it's never just a rectangle on the ground unless you're sitting in the pits. It's constantly deforming in the X and Y planes, and x4 for each corner. When chasing grip, you're always trying to maximize that contact patch, or the amount of tire which is interfacing with the racing surface.

The fastest way to influence that is by changing the characteristics of the tire itself - i.e., air pressure. But what you do with the suspension of the car influences the forces placed on each tire of the car under given scenarios. So if you need more grip at say, the front, you want to transfer more weight onto that tire (i.e. braking before turning). What the suspension does is allow you to control how much weight transfers when you do hit the brakes (or turn, or accelerate, etc).

As others have stated, by increasing rough tire width, you are instantly giving more static contact patch. Logically, putting more tire on the rear with an already understeering car is probably not going to improve the understeer. I think when you see staggered setups it's because they have crossed into the threshold where they have enough engine that they are constantly breaking the tires loose, particularly on corner exit, so they need more contact patch where it counts.

What fascinates me is how *tiny* the actual part of the tire is that interacts with the road at any given time. It's a fraction of the size of the whole tire, but even with a street tire, it's enough to corner over 1G in most cases.

Having been the only other person here that's driven you car (I think), my impression is that you still have plenty of rear tire for your current setup. Note - I've also only driven it with DOT radials, not slicks. If anything, I always felt like it suffered more from lack of initial turn-in. When we had a full tank of gas, which is much closer to your front axle-centerline due to the fuel cell, I could get a lot of weight up front, which is ideal for turn-in. The problem I saw was that I was locking up the wheels, which means the brakes were overpowering the tires, at least with a full tank of fuel. That's a good problem to have, IMHO- you never want to have more tire than brakes available. In my mind, what would improve it would be to make the whole front more compliant, which would mean loosening the sway bar, maybe dropping front pressures a little to allow you to trail-brake a little more (keeping weight on the front longer) without locking up the wheel.

The real fun part, as you mentioned is when some of the gas burns off, will those adjustments make the car oversteer like crazy? I personally like some oversteer, and as is often said "loose is fast."

Take all my thoughts with a grain of salt - I don't have near the experience as most of these guys. (IMG:style_emoticons/default/smile.gif)