What makes the R227 different?

For one thing, its unidirectional tread pattern. Outside of racing tires or high-performance passenger tires, you rarely see a unidirectional tread pattern.

By designing it to travel in one direction, Bridgestone engineers were able to optimize the R227’s performance, especially for irregular wear. What happens if we run it the opposite way? It won’t damage the tire, nor will it diminish traction. Nevertheless, for best resistance to irregular wear, you should always run the R227 in the direction of the sidewall arrow.

Can we rotate the R227?

If you need to rotate because of misalignment wear, swap sides, but be sure to demount, flip and remount the tires, so they continue to rotate in the proper direction.

Do we have to maintain that direction once the R227 is retreaded?

The R227 tread is unidirectional, but the casing is not. Once you’ve retreaded, you can mount retreaded R227s for either direction of rotation.

How does the R227 fight shoulder wear?

Shoulder edge wear starts because of abnormally high contact pressure at the shoulder edge, which scrubs away part of that edge. Then it continues and worsens because of lower contact pressure resulting from the initial wear. The result is rapid spread of irregular wear across the shoulder.

Side forces cause wear to begin at the edge of the shoulder, which then rapidly spreads to the rest of the shoulder rib.

Why does that happen?

If you bolted two tires of different diameters together, both would have to cover the same amount of road with each revolution. The smaller tire, with its smaller circumference, gets dragged to make up the difference between its circumference and that of the larger tire.

A smaller tire and a larger tire cover different distances in one revolution. If they’re bolted together, the smaller tire gets dragged the extra distance.

So the smaller tire wears much faster. If one part of a rib on a multi-rib tire is a bit smaller than the rest of the rib, the same sort of thing happens. It drags, wearing away faster than the area beside it.

If the shoulder gets a little worn because of side forces from turning and maneuvering, or even road crown or alignment, the edge becomes smaller than the rest of the shoulder, and wears much faster.

Eventually, that irregular wear spreads.

Is that where the Side Groove™ feature comes in?

Correct. Because of its design, the Side Groove structure adjusts pressure at the shoulder edge. With high side forces, it closes a bit, to relieve pressure.

With low side forces, it can open, to even out pressure, for even wear. Some people liken it to a “shock absorber” for the shoulder edge.

The Side Groove structure on the R227 can open or close to relieve pressure at the shoulder edge to fight irregular wear.

What are these narrow ribs alongside the inner ribs?

They’re Equalizer Rib™ structures. Bridgestone engineers found forces promoting both even wear and irregular wear in the tread surface.

But what is truly revolutionary is that by deliberately creating an area that promotes irregular wear, irregular wear forces from the tread surface can be funneled into this area.

When that happens, irregular wear forces are drawn away from the rest of the tread, promoting even wear.

The R227’s Equalizer Rib structures attract irregular wear forces to themselves, sacrificing themselves to protect the main ribs beside them from irregular wear.

How is that done?

The Equalizer Rib structures are slightly smaller than the ribs beside them. Just as in our explanation of shoulder wear, these smaller ribs create dragging forces as they roll through the footprint.

Almost like lightning rods, these ribs draw irregular wear forces to themselves, dissipating them harmlessly. And, those irregular wear forces are removed from the main ribs alongside.

Equalizer Rib structures in the R227 control the distribution of wear forces that contribute to even wear.

Is there anything else distinctive about the R227?

One thing is its initial footprint. Generally speaking, an ideal footprint is slightly longer in the middle,
roughly squarish overall, with slightly rounded edges.

Unfortunately, as a tire wears, its footprint changes. This often results in tires that start with near-ideal footprints and end with less than optimal ones.

What have you done about this?

You’ve probably noticed that flatbed trailers often aren’t flat, but bulge upwards when they’re empty. That’s so when they’re loaded, the bed will actually be “flat.” You make the bed not flat, so it will end up flat.

Bridgestone engineers did something similar. The R227 starts with a footprint that doesn’t look “ideal” at all. Then, as the tire wears, the footprint stabilizes into a near-ideal shape.

That promotes even wear, and when coupled with the Equalizer Rib feature, makes it even more effective.

The R227 footprint starts out looking a bit odd, so that after it changes with wear, it becomes virtually ideal for promoting even wear.

What other new features does the R227 have?

Notice the tiny notches along the middle rib and the ones alongside. These small sipes help relieve tread element stresses as they roll through the footprint. They work so well that we’ve nearly doubled the number of them in today’s production of the R227.

And, to give the second rib tread elements more stability to fight squirm, we’ve increased the height of miniature tie bars that link each block to the next. This also helps fight the initiation and spread of irregular wear.

Tie bars linking tread elements fight squirm that can lead to irregular wear. Note also tiny rib edge sipes that help reduce river and wavy wear.

What’s the result of all this technology?

Most steer radials are removed for irregular wear, not for wearout. Since a steer has to be removed if any portion has 4/32" or less tread remaining, the more even the wear, the higher the removal mileage. And the higher your removal mileage, the lower your cost per mile. That’s what every Bridgestone radial is designed for, including the R227.