Flask

<center><img src="http://pictureposter.audiworld.com/7275/PirelliP6000.jpg"></center><p>The picture below is a Pirelli P6000 (the tire that came on my car from the factory). When the tires are mounted on the car, on the driver's side the grooves in the outside pattern "flows" from the outside edge forward. When mounted on the passenger side, the pattern flows from the outside edge rearward.

Doesn't this affect handling? For tires where the patterns flow in the same direction on both sides of the tire (symmetrical pattern) , I would think you would want them to flow in the same direction on both sides of the car, right?
Example: Dunlop Sport 9000

Could someone enlighten me?

Hibiscus Boy

Look for the arrows on the sidewall.

Flask

Not sure, but if you look at the pattern of the P6000, it doesn't seem to matter.

Bollinger

I understand what you say about the pattern and the direction of rotation, but it doesn't make any difference.

I've never understood directional tires much. A tire obviously has to apply force in both directions, since they do both acceleration and braking. I think the directional tread is really only useful for hydroplaning.

Flask

<center><img src="http://pictureposter.audiworld.com/7275/2PirelliP6000s.jpg"></center><p>Pretend your facing the front of the car. The tires will be sitting something like this (with excessive toe-in of course ;-)

The pattern on the ourside of the driver's side tire flows from the ourside edge and down toward the ground,

The pattern on the other tire flows in the opposite direction.

Flipping the tires around does not produce a different result.

Doesn't this mismatch between left and right sides affect handling? It's almost like you have two pairs of different tires.

larryV

I have the same issue with my assymetrical SP5000's... the way the tread "flows" is always different on the right as it ever would be on the left.

I don't have an intelligent answer to that but it probably doesn't matter otherwise the tire manufacturer wouldn't have designed it that way.

ChaoticS4

Yokohama Parada's are exactly the same way...

Bollinger

You don't need to ask it a different way, I think we all understood you. The pattern on the tire has almost nothing to do with its grip. The ratio of voids to tread does affect the grip a lot.

Gaps between tread blocks only do a few things.
1. Prevent hydroplaning. Since water is incompressible, you have to give it somewhere to go when the tire comes down. Light rain actually goes inside the tire compound and gets spun back out later. Heavy rain goes into the grooves between the tread blocks.
2. They give the tire some give. This helps tires not follow grooves in the road. A tread block can deform side to side. So, if you are almost following a groove in the road, each tread block is undeformed when it first hits the road. As it rolls through the contact patch, it will deform to the side, say 1/16" as it follows the groove. Then it springs back when it leaves the ground. So, although each tread block is getting pulled over, you can still go straight. Plus, as you get close to the edge of the groove, one tread block will eventually land on top of the aready next to the groove instead of in it, and it won't get pulled in. If there aren't tread blocks, then each section of tire comes down onto the road already pre-deformed since it is connected to the patch of tire next to it which is already pulled over. Also, to ride up out of the groove, the continous tread has to resist sliding down into the groove when it comes down on the edge. This is why ultra-performance tires with the continuous rib down the center follow grooves so badly.
3. Also, varying the size of tread blocks makes the tire quieter, as the noise each tread block makes is partially dependent on its size. By spreading out the sizes of the blocks, you spread out the noise over a wider frequency spectrum, but with a lower peak. So it seems quieter.

Other than these things, tread blocks don't do much, so it doesn't really matter what shape they are. This is being used to good effect lately by Yokohama and others making good-looking tread. Before, the appearance of the tread wasn't even a factor.

So don't worry about the orientation of your tires, it really doesn't matter.

Flask

Thanks. A good explanation. Either you know what your're talking about or you made that up ;-)

Bollinger

AKA Dr. G.R. Potts. He is a significant figure in the tire industry. He was instrumental in creating computer-controlled tire testing. He worked at MTS (Machine Testing Systems), then formed his own company. I worked at that company. We advanced machine testing (tire testing) incredibly in a few short years. However, our financial weakness scared clients a little. Eventually, MTS convinced our prospective customers to not buy from us and thus put us out of business. MTS then acquired the assets of the company and G.R. Potts went back there and used MTS's considerable resources and industry position to improve upon what we had done.

When I worked at his company, we made the first ever high-speed tire testing machine. This was in the early 80s. Before that, all of the more scientific (controlling all variables, as opposed to mounting them on a car and driving it) performance-related tire tests were done at an maximum of 4mph (usually 2.5mph), and the results were extrapolated up. Advances in data acquisition, machine control (variacs), and materials science allowed us to create a machine which could test usefully up to about 60mph.

Although I was a computer programmer, not a tire engineer, I do remember quite a bit from the talks he gave us on how tires work. Most intriguing was that at that time, no one really knew what held the weight of the car up. At first glance, it's obviously the air, since if you remove the air, the rim sinks to the ground. But it also has to be the tire since if you remove the tire, air alone doesn't hold the car up either. Okay, it sounds stupid, but at that time, companies were just beginning to attempt to figure out how the air/tire combo held the car up, so they could try to improve the technology. It led to changes in sidewall design.