50% of your EV energy consumption comes from wheels and tires

[Isaac Zachary]

Originally Posted by j-c-c

The wrinkling seen IMO is a byproduct of the lag of the outermost tread surface "stuck" to the pavement lagging rotationally behind the wheel rim, angling the tire's carcasses reinforcement plies from no longer being perpendicular to the rim as the rim/wheel tries to accelerate its rotation, resisted by the car's mass, and that angling of the ply's without stretching allows the tread/contact surface now to become closer to the rim, effectively shortening the rolling radius of the tire. The inherent compression as tire gets a smaller rolling radius of the contact patch forces the sidewall to wrinkle.

Yes I agree. What I don't agree with is that this somehow creates artificial downforce.

[freebeard]

Temporary drop on launch from contraction. Only the bottom of the tire distorts.

I'm pretty sure those ar bias ply. Radials wouldn't ballon like that.

That's a lot of rubber being slung in a pretty tight circle.

[j-c-c]

Originally Posted by Isaac Zachary

Yes I agree. What I don't agree with is that this somehow creates artificial downforce.

There is an increase in tire contact pressure, mainly IMO caused by weight transfer, stating the obvious.

Whoever that made that claim needs to explain it, and it wasn't me.

[freebeard]

Permalink #36?

[j-c-c]

Originally Posted by freebeard

Permalink #36?

I see nothing in #36 that relates to increasing traction in this context.

[freebeard]

Hope this helps:

When a loaded wheel and tyre is compelled to roll in a given direction, the tyre carcass at the ground interface will be deflected due to a combination of the vertical load and the forward rolling effect on the tyre carcass (Fig. 8.10). The vertical load tends to flatten the tyre's circular profile at ground level, whereas the forward rolling movement of the wheel will compress and spread the leading contact edge and wall in the region of the tread. At the same time, the trailing edge will tend to reduce its contact pressure and expand as it is progressively freed from the ground reaction.

The consequences of the continuous distortion and recovery of the tyre carcass at ground level means that energy is being used in rolling the tyre over the ground and it is not all returned as strain energy as the tyre takes up its original shape. (Note that this has nothing to do with a tractive force being applied to the wheel to propel it forward.) Unfortunately when the carcass is stressed, the strain produced is a function of the stress. On releasing the stress, because the tyre material is not perfectly elastic, the strain lags behind so that the strain for a given value of stress is greater when the stress is decreasing than when it is increasing. Therefore, on removing the stress completely, a residual strain remains. This is known as hysteresis and it is the primary cause of the rolling resistance of the tyre.
...
Not identified in this source, another paper pointed out that tires can have a circumferential vibration mode, a circular resonance. When tires "sing", they are also losing energy by flexing the tire tread.

[j-c-c]

It doesn't explain "artificial downforce" as I see it. It must be me.
The only additive load/force imbalance here that might be at play is that which is not recovered as the wrinkled tire unloads as it leaves the contact patch and is therefore lost to heat, but initially that force loads the leading edge of the tire as the ubiquitous downforce component?
Meaning its directly related to the heat the tire's sidewall generates, which IMO is not a lot and almost insignificant?

[Isaac Zachary]

Originally Posted by j-c-c

It doesn't explain "artificial downforce" as I see it. It must be me.

No.

I think you and most of us are all on the same page.

Physics are physics, and for the most part are pretty obvious.

A tire does not generate downforce by itself. Acceleration and deceleration and cornering can place "more weight" from one set of wheels to another (technically the weight doesn't move, but the angle of overall G force does, which is a combination of gravity and inertia).

[freebeard]

It doesn't explain "artificial downforce" as I see it. It must be me.

I now understand my misunderstanding.

Downforce: How much does the vehicle weigh? How much of that is on the rear wheers? All of it, if the fronts aren't on the ground?

So the side-wall flex shrinks the rolling radius by 2-3 inches. You can work it out in pound-feet of downward force [requires G].

[CapriRacer]

Doesn't twisting the tire - tread vs rim - effectively shorten the sidewall height? And isn't that why the sidewall buckles?