Wider tires, reality?

[barkingspud]

Depending on boost level 700-860

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[involutions]

yes, see my response. Street radials aren't going to reward you very much (forward) with a wider tire and bigger patch. They will however make a noteworthy change in lateral grip. Anyone who's ever driven a car on pizza cutters and then got into a car on wide tires can notice the difference.


let's also not forget that maximum friction force (for both static and dynamic friction) is dependent upon the "normal load" or weight binding the two surfaces. This is why weight transfer and suspension makes a huge difference. If you ca shift the entire 100% of a vehicles weight/downward force to the rear tires, the amount of friction force is considerably increased. If you're on a high performance track/turn suspension that does not transfer weight well, improvements to the tire setup are going to be nominal.

So once you've maxed out the practical width of the tire, sidewall of the tire (for flex) and compound of a tire, the logical next step is increasing the downward force.

I personally don't like driving a car where you tap the pedal and stair at the tops of buildings. There's plenty of suspension solutions out there that attempt to provide a somewhat changeable suspension setup/solution while trying to launch vs trying to keep a stable ass end going around turns. (changing the dampening, spring rates (or using bags) etc).

Lots of guys focus on tires, but at the end of the day, you can only do so much with the tire, it's really the suspension and weight transfer that has more pronounced effects once you've basically maxxed out what the tire can offer.

Thanks for the reply. More good info.

 

[SplawnDarts]

So first off, contact patch area is 100% a function of tire pressure. The patch area times the tire pressure has to equal the load on the tire. There's no alternative - it's physics. Wider tires do presumably give a different SHAPE patch (wider and shorter).

The coefficient of friction between rubber and road is not constant. The higher the pressure per square inch on the contact patch (aka the higher the tire pressure) the less grippy the tire will be. And compound and tread matter a lot. So you can increase grip by a) reducing tire pressure b) changing rubber or c) changing tread.

The faster you accelerate, the more weight is shifted to the rear tires and the larger the contact patch is. So to some degree faster acceleration allows yet faster acceleration, at least until the front tires unload.

The basic answer is that wider tires help only if they let you reduce tire pressure and then the help is modest. Stickier tires always help a lot.

 

[SplawnDarts]

Oh, and you can do some pretty basic calculations to figure out how much power you can get to the ground at various speeds. If you assume 1G of forward tire grip (which is probably the very very top of street tires on a RWD car) with the mustang's weight and drag coefficient and some generic rolling force numbers you get:

10 MPH: 109 rear wheel HP
20 MPH: 218 HP
30 MPH: 328 HP
40 MPH: 439 HP
50 MPH: 551 HP
60 MPH: 665 HP
70 MPH: 781 HP
80 MPH: 899 HP
90 MPH: 1020 HP
100 MPH: 1144 HP
and so on, adding about an extra 120 usable HP per 10 MPH

This explains why everyone says they can't get their supercharged car to hook up until ~60MPH or so: they can't.

Various drag tire configurations can pull much more than 1G forward - in excess of 4Gs in fact. They can do so in part because of stickier tires. There's some argument about the role that downforce and the physical impact of the tread of the tire on the ground play in getting such a high acceleration. But you can adjust the above numbers accordingly. Those sorts of tread momentum dynamics don't seem to play much role in normal street tires though.

 

[ahl395]

Overthinking it, probably.
And yes, I agree, at least to a reasonable point that wider is better. Obviously a 2" wide tire wouldn't work out well. But is going from a 275 to a 305 better than going from a Michelin PSS to a Bridgeston RE-71R, both in 275, for example?

Both, would be the best route lol.

But given the two options personally I would speculate that the tire upgrade in 275 would be better.

 

[WildHorse]

it's simple physics

Going from a 235/50r18 radial to a 325/30r19 radial did nothing. Slowed me down in fact.

 

[sigintel]

Overthinking it, probably.
And yes, I agree, at least to a reasonable point that wider is better. Obviously a 2" wide tire wouldn't work out well. But is going from a 275 to a 305 better than going from a Michelin PSS to a Bridgeston RE-71R, both in 275, for example?

From my road course experience:
RE-71R in 275 will outperform PSS even if PSS was 305(have run 305 PSS on Whippled 15 on road course).
PSS will last longer and be better tire to learn on.
PSS in 305 will handle more abuse and overdriving.
RE-71R 305 square will allow you to induce more oversteer than you can handle if you dont detune the front susp and leave enough body roll in back.
RE-71R square would like be bad for learning w stock GT hp levels.

Compound usually makes biggest difference in raw grip up to the point you can accomplish enough load shift to overload/overheat compound and push it above optimum temp range for grip/durability.

Heat cycling up a softer compound can get you more durability in exchange for lower grip.

 

[crcpdx]

I went from a 275 4s to a 325 4s when the car was stock I noticed considerable gains in straight line traction. At the strip where I had more grip than power, I actually got slower.

 

[abbeynormal]

I think a piece of the puzzle you might be looking for @involutions is that lateral grip drops as vertical loading increases. Which is one reason why adding weight to a car reduces cornering performance, even though there's more weight pushing down on the tire; you might put 2x the vertical load on the tire but you might only get 1.9x the lateral grip.

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