It's 4s time and not sure if wider is better and four vs just two. Would appreciate anyone with prior experience sharing their thoughts.

 

there's not much to gain on a RWD car from 305 width tires up front. In fact, you are a lot more likely to run into clearance issues and have more sidewall deflection in corners. I'm pretty sure they won't even fit on the wheels, as the fronts are narrower than the rears. The wider tires in the rear will help a tiny bit with traction, but in my experience you will probably not notice much of a difference versus a 295, assuming you experience both of those widths in the same tire. Our cars simply have too much torque to stay within the limits of tires that can fit in the wheel wells. Clearance may be a concern there as well. Even for the AWD models, I don't think there is much benefit to changing the tire size.

 

From the picture, it looks like an R-RWD. You will have some benefit from 305 in the rear (go 265 in the front). Ideally you will use an 11" wide wheel in the back and NOT 10.5"

 

 

Right, to clarify, 265 front vs leave it at 255, and 305 rear or leave at 295. Rear wheel drive. On stock wheels so unhingd's reply helps a lot. Then no diffrence unless I move up in wheel size? Searched a bunch of the old threads and couldn't find that nugget.

 

while I agree that the wider wheel is necessary to maximize the benefit, I still hold that a 10mm difference (on street tires, including the venerable 4s) isn't enough to notice in our cars, even with the wider wheels. without much effort, and with traction control disabled, the rear tires will happily spin through 3 gears. It'll be the same on 305. That has been my personal experience on my highly modified '98 Cobra, which still has 10% less power than my f-type R. I wasted a lot of money swapping out perfectly good wheels and tires to discover that the only way to improve the traction on that RWD beast is to modulate my right foot.

 

 

On my R RWD I have the Michelin 305 on rear and left the fronts the stock size.. I simply preferred the look.. these are about as far as you can go regarding width on the stock rims..
I have a picture of these somewhere on the forum from a couple of years ago but I don't recall the thread.
No complaints.
Lawrence.

 

Wouldn't a bigger (wider) tire have a larger contact patch? I'm assuming you would run a pound or two less pressure..

 

Most consumers neglect to consider "Tread Width". As you are set on one specific tire it is not relevant to you. However for others if they are comparing different manufacturers or even different tires of the same size from the same manufacturer, then it may make a difference.

https://www.tirerack.com/tires/tiret...jsp?techid=201

 

 

I imagine there is also a range of width where going wider also helps. Taken to an extreme, one only need to imagine of a very narrow tire on our cars, say bicycle/motorcycle width - clearly going wider than that would increase fore/aft traction too. Diminishing returns as you continue to add width, but do we know that the manufacturers always select the optimum?

 

Running the same PSI and ignoring sidewall stiffness, no. Pressure = force/area. Lower the pressure in the tires and yes the contact patch will get bigger. But changing the width of the tires themselves doesn't change contact patch area; just shape.

Of course.

OEMs make compromises for fuel economy, tire life, handling, etc. Everything is a balance.

 

And aesthetics. Those original E-Type tyres look really skinny nowadays.

 

The technology did not exist back then to manufacture super wide radial tires.

 

But changing the width of the tires themselves doesn't change contact patch area; just shape.

Might be remedial math but how could adding 10mm of tire width not increase the contact patch width by 10mm? And again, all other things being equal, why would a larger contact patch not equate to greater traction in all directions? It's been a while since physics in college and I still struggle with gyroscopic precession on a motorcycle but clearly am in need of an education.

 

The contact patch does get 10mm wider; but at the same time it also gets shorter relative to that 10mm. When you make the tire wider but keep the pressure and weight of the car the same, the tires are still squishing the same amount they did before, but in a different shape. Think about how skinny the contact patch of a tire is when its just sitting on the ground by itself. Then think about how much fatter it is after you've put the weight of the car on it. If you make the tire wider, the tire doesn't have to squish down as much over its length to support the weight of the vehicle, because it has additional width to help.

 

That's why I mentioned reducing pressure a couple PSI, 10 posts ago.

Then, you also have the consideration of getting the tire's temp up to the proper temperature for maximum grip. (It's a complicated world we live in...)

 

WOW! Ok, so the actual size of the patch is determined by the nominal width of the tire (transversal) and the longitudinal one is determined by pressure and structural rigidity of the tire (so long as the weight on that wheel remains constant). A wider tire of course provides greater resistance to side dragging at the potential detriment of longitudinal traction (acceleration and braking). However, that's where tread pattern design kicks in, not only for water displacement but it needs to provide the highest possible patch density.
Tire compounds are formulated to work at specific pressures (not air pressure) but mass/path area, these pressures vary from the sides to the middle and additionally, steering affects it because of weight transfer. The above generalizations are all good as long as you compare a 295 vs. 305 on the same manufacturer and same model tire. Another brand/model may have different structural designs and the patch may vary in size and shape.

Another significant factor is the sidewall rigidity, when very stiff, it aids greatly in directionality but will not deform in a matter that would help in acceleration (by not allowing the patch to deform longitudinally) and vice versa. Suspension geometry also affects the contact patch... basically, a "wider tire" isn't always a guarantee for better grip in every direction, and equal size tires from different manufacturers perform differently, not only because of the rubber compound or tread pattern but structural rigidity.

There is a tremendous amount of engineering in a tire and I cringe when I see so much simplification that can result in adverse effects.

 

Yes, yes... you did say that. And you could also reduce pressure in the original size tires and then we'd be right back where we started with this discussion; which is why i ignored tire pressures.

Cringe all you want, but this admittedly oversimplification is better than people continuing to think a wider tire makes the contact patch bigger and will help prevent wheelspin. I see this statement everywhere and its just plain wrong. Sidewall height/stiffness, compound material/construction, and tire pressure all have their place in this equation, but if you're choosing a wider tire for the sole purpose of reducing wheelspin, you're doing it wrong... and that's the point i'm trying to make.