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What is scrub?
Scrub is an abusive element that rubs or scrapes away tread, reducing tire life.
The result of this scrubbing action is the same as using extra-fine sandpaper on a piece of wood. One or two times across smooths the surface, but the same motion day in and day out will produce quite a pile of sawdust.
Abusive scrub is worse. It's like using coarse sandpaper on an electric belt sander and scraping off large amounts of wood - or rubber in this case - with each pass. Trucks that maneuver in tight spots, that stop and sharply turn the wheels in one direction or the other, scrape off quite a bit of tread. Which, of course, significantly reduces tire life.
What role do road surfaces play?
Obviously, crumbling roads and sharp potholes are potential dangers. A long-distance tractor trailer that travels 99 percent of its time on the Interstates encounters far fewer hazards than a regional or urban truck that drives across two-lane roads with potholes, train tracks and loose, crumbling asphalt. Or for that matter, on gravel or unimproved roads, which are even tougher on tires.
How so?
Gravel is extremely abrasive to truck tires. Let's go back to our sandpaper analogy and imagine a big electric drum sander being used by an inexperienced operator. The sander could "get away from him" and the uneven pressure could cause gouges and deep grooves in the wood's surface.
Sharp gravel can also gouge and cut grooves into a tread's surface.
If a fleet's regular route takes them on unimproved roads, a tire with a tougher tread compound can help prevent the kind of damage that reduces tread life.
The new R250 ED is compounded for mild on/off-highway use, which, depending on how rough the road surface is, could mean up to 30 or 40 percent time spent on gravel surfaces.
What does the compound do?
It helps resist cuts, chips and chunks, which can reduce tread life.
Another element that can reduce tire life is trapped stones, which can damage a tire so severely it has to be pulled from service, preventing the casing from being retreaded. So the best way to prevent the damage is to prevent stone drilling in the first place.
How do you do that?
There are two ways to prevent stone drilling. One is to use stone rejector platforms, which can be found on most Bridgestone drive radials, like M726 EL and M725.
The second is to design the shape of the groove so it discourages stones and rocks from lodging or getting stuck in the groove.
How does that work?
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While many grooves are "U"-shaped, the groove shape of the R250 ED is "V"-shaped. This design lets stones fall out easily along with dirt and other small debris.
The design promotes retreadability and of course, lower tire costs.
Two other features of the new R250 ED promote retreadability. First is a solid shoulder, which offers superior durability. And resists curbing damage for longer life.
And the second?
The rugged sidewall protector ribs also promote retreadability by reducing curbing damage. Both sidewalls are ribbed, so if one side wears away, you can turn the tire over for continued protection.
Why doesn't it have a groove in the side or shoulder like most other Bridgestone steers?
Remember our sander analogy? High scrub rubs tread off so quickly, like an electric belt sander, there's little chance for irregular wear to become a problem.
Many Bridgestone radials incorporate a Defense Groove™ feature that promotes even shoulder wear. On most urban routes, where there's a lot of maneuvering, especially around tight places, that groove can be torn right off the edge of the tire.
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