Well here a chassis for a chevelle

[Derek69SS]

In all honesty, you can get equal geometry improvements with bolt-on parts on your stock chassis for a LOT less money. The only real benefit I see over the right combination of bolt-ons is the added chassis rigidity.

The big rear tires are cool if you're not serious about road-racing/track days (which most of us aren't but if you are...), they will come up to temp much slower than the smaller fronts, effecting the balance of the car differently throughout the run... if it starts neutral, when the fronts get sticky it will go loose, then the fronts get too hot as the rears just start to get sticky and it goes tight. They also require running the springs/shocks further inboard negatively effecting the motion-ratios.

Edit: ...should add the big tires may help on a tight course such as an autocross, but likely a hinderance on a big course.

[XcYZ]

Originally Posted by Derek69SS

The big rear tires are cool if you're not serious about road-racing/track days (which most of us aren't but if you are...), they will come up to temp much slower than the smaller fronts, effecting the balance of the car differently throughout the run... if it starts neutral, when the fronts get sticky it will go loose, then the fronts get too hot as the rears just
start to get sticky and it goes tight.

I will agree with that, but if you're going to look at how the tire temp changes are different with different size tires, then you might as well start looking at everything, such as fuel load. As you use fuel your balance is going to change, just like it will with tire temps. I know some guys that used to race using methanol but have switched to race gas because you don't use nearly as much over the course of the race, which means the change in balance isn't as drastic.

Of course, with street tires, this is just about pointless. lol But if you're serious about competing (in sanctioned racing), nothing is left out of the equation.

I still say that tire sizes differences from front to rear can be dialed in with the right chassis setup.

[68protouring454]

they were out of the top 5 until they got to hot lap it 4-5 extra laps to knock the last 2-3 10ths off, at the end before the top 5, the car is cool and did well for a boat..
cool chassis, and they were nice guys too.

[PTAddict]

Originally Posted by Derek69SS

The big rear tires are cool if you're not serious about road-racing/track days (which most of us aren't but if you are...), they will come up to temp much slower than the smaller fronts, effecting the balance of the car differently throughout the run... if it starts neutral, when the fronts get sticky it will go loose, then the fronts get too hot as the rears just start to get sticky and it goes tight. They also require running the springs/shocks further inboard negatively effecting the motion-ratios.

FWIW, my '71 Camaro with a modified LS1 uses 265 front and 295 rear Pilot Sport Cup tires on the track (Portland Raceway). After a 20 min session, the pyrometer shows the rear tires 5-10 degrees hotter than the fronts, even with 4 PSI greater hot pressure.

I notice that high-powered RWD cars with near 50/50 weight balance (Viper, Z06) are often running 50mm or more rear stagger, even in full-race setups. You want that kind of car to keep the rear end stuck down when hard on the throttle exiting turns. Something like, say, a spec Miata is a somewhat different story ...

Finally, keep in mind that a solid axle car provides no provision for negative camber in the rear. Personally, I will run the biggest tires that will fit on both ends, then tune with camber, shocks, and tire pressures.