When are tires too wide......

[JAJ]

...fire it into a corner without lifting, ever, the car is probably too tight.

Or underpowered

 

[blacksheep-1]

If you can't add HP then start subtracting tire. I talked to a confidant named John Heinricy about this and he agrees, at some point he tire can get too wide for the car, and he's experienced it first hand. There is a point of diminishing returns out there..someplace.
Reminds me of the time I talked Kurt into jacking the air pressure up to run a fast lap in practice. We kept getting faster so we decided to go for it and find the edge in practice rather than in a qualifying or race deal. Somewhere around 8psi is the edge. Kurt came in and said that was the fastest half lap ever...then I couldn't hold on to the car for the second half...lol

 

[drano38]

More tire is probably like asking a fighter pilot if there's such a thing as too much thrust - he'll always say no.
At extremes, I'd agree too much tire is possible, like maybe 20" wides on a go cart. But on a Mustang, probably can't get too much tire.

 

[JeffV8]

20" wides on a go cart. .

It’s go kart ... sorry raced karts for almost 20 years.

 

[302BOB]

My stock size tires get me as fast as I want to go........

 

[Norm Peterson]

With the current trend of bigger is better.... is their a point when its too much? A buddies gen 5 ZL1 is running on R7 335/30-18's all the way around, and though he has amazing grip he seems to one second slower then he used to be.

Has the new tire size forced him to be in higher gears than before? In many places?


Norm

 

[8250RPM]

Since most of the supers run articulating wings, that's not a great example, but point taken.

Sorry modernbeat, nothing is lighter than an MG Midget with the exception of a box of Kleenex.
At some point out there, there will be an edge, whether it's a kart, or formula car or a sedan, at some point a fat, sticky tire can very well become the point of diminishing returns.
If you were to take that miata, and run 14 inch , 45 durometer tires on it, (or whatever) fire it into a corner without lifting, ever, the car is probably too tight.

A triumph spider is lighter than a MG Midget.
The Alfa Romeo GTA was also light.


Sent from my iPhone using Tapatalk

 

[blacksheep-1]

In any case, my point is that you should run the smallest tire that provides adequate traction

 

[Mad Hatter]

In any case, my point is that you should run the smallest tire that provides adequate traction

That reminds me of a R&T (I think...) article that showed 1/4 mile times of different comman tire upgrades on a golf gti..... the widest was the slowest time. But then again not a very powerful car.

Sent from my SM-G900M using Tapatalk

 

[modernbeat]

Sorry modernbeat, nothing is lighter than an MG Midget with the exception of a box of Kleenex...

Both of my Europas and my Seven beg to differ. 1320lbs, 1140lbs, 950lbs. And they all got faster with wider tires.

 

[Mad Hatter]

Out of curiosity, what size can you get on the Europas?

 

[blacksheep-1]

I'm sure they do......

 

[modernbeat]

Out of curiosity, what size can you get on the Europas?

Under stock fenders? I think we ran a 175/70-13 or something close to that. The one with flared fenders ran a 20x13 R25B on all four corners, then swapped the rears to a 22x13 and changed the gearing in the Hewland to match. I ran both of those same setups (20" and 22") on the Seven also.

 

[Norm Peterson]

Jason - that 7 look at all like this one?

Belongs to a friend of mine from autocross days. From what I hear, there isn't much he doesn't get held up by going through the technical sections at NJMP. Might be as light as 11xx lbs with 190-ish HP.




Norm

 

[Mad Hatter]

I would imagine that autocross would be pretty much as wide as you can possibly fit. Where as tracks with long straights would have a bigger drag penalty for huge tires?

 

[racer47]

I can't see any drag penalty. The rolling resistance difference is trivial. The tire aero drag difference is trivial on full bodied car. The only downside I see is a bit of extra tire and wheel weight that needs to be spun up down the straights. But I've never seen anyone pick up 5 seconds a lap with light weight wheels. But everyone goes faster with bigger tires. I don't doubt that there are diminishing returns and probably some hypothetical maximum size. But thats likely to be way bigger than the practical size limit.

 

[stuntman]

Depends on the car, weight, power, tire, use, etc...

While big, heavy, powerful mustangs will almost never find the point of having "too much tire", if a given car can't generate enough energy into a tire to get it in it's operating window, a smaller tire that is in it's window will be faster.

Put a 305 Pirelli slick on a 200hp Miata in 40* weather, and the tires will never switch on. It will feel like it's on ice/wet. Now put a smaller Pirelli on it that can get some heat in the tire and it'll be significantly faster.

Like the BRZ example, a 275 on a *road course* would probably be slower on a <200hp Gen 1-2 miata than a smaller tire due to the increased mass, rotational inertia, drag, etc... Where any gains in the corners (if any) are more than offset by the weight and drag penalties. Now if it was a 120* day and you were running super soft tires where say a 225 was outside it's operating range and blistering, then a 275 would be faster if the larger mass kept the temps within it's operating range.

So it all depends. But in most street car cases, short of miatas, elises, brzs, and the like, generally wider is faster because heavy street cars are under-tired.

 

[racer47]

Your mixing in tire compounds with tire sizes. If its 40F you need softer tires. What exactly are these "drag penalties" everyone keep repeating?

 

[Norm Peterson]

A few lbs aero drag plus a few lbs rolling resistance. They exist, but I doubt them to be significant effects in most cases.


Norm

 

[racer47]

Exactly, a few pounds. Compare that to higher cornering speeds, shorter braking distances, more grip exiting resulting in sooner to wot.