q Tires are no different from any of us. When they get old, they start slipping. It’s just a matter of time before replacement is inevitable. But you can postpone retirement, at least in the case of tires. Mark Evans came up with a product called KnobbyKnife, which you can use to give new life to old tires. This is a heated tool that kind of resembles an old-fashioned soldering iron, but with a 1.25-inch razor at the top. It’s designed to cut rubber quickly and easily, so that you can either groove the knobs or give them a fresh edge.
Tire groovers have been around for years. Goodyear made one that dirt-track racers have been using since the ‘50s. But that one is large, clumsy, expensive and hard to find—we don’t even know if it’s still being made. The KnobbyKnife is compact and inexpensive, and it’s fairly easy to use. You just plug it in and wait for it to warm up—there’s no on/off switch. Once it’s up to temperature, it cuts through rubber like butter.
We cut several tires with the KnobbyKnife; it really is easy and fast on conventional block-style knobs. The product was originally designed for use on motorcycle knobbies, so if your tire has that type of tread pattern, giving each knob a fresh edge just takes seconds. You just start at the top of the rounded-off part of the knob, then push down and scoop off the worn piece of rubber. A tire with block knobbies can be done in about 15 minutes. On rear tires, it’s easy to know where the most effective place is to cut. The worn edge is the one doing the most work, and that’s where a fresh edge is needed the most. On front tires, the same principal holds true, but it isn’t always on the leading edge of the knobby. The side knobs, where the tire rolls over slightly, can show the most wear.
Lately, tires with chevron patterns and large ridges are becoming more popular, especially for loose terrain. These are a little more difficult to cut cleanly with the KnobbyKnife. It’s still best to cut downward, toward the tire, rather than try to cut across the edge of the knobby. But instead of cutting one knob with each motion, you can only cut a little section at a time. That makes it more difficult to produce a neat and pretty edge, but the end result is the same. You can get a fresh-edged tire with a fairly short amount of work.
So how effective is it at extending the life of an ATV tire? We found that it can make a tire effective longer, but not necessarily make it go farther before it wears out. As you can imagine, there’s a great benefit in having a fresh, sharp edge on each knob. A worn tire will feel like new right after it has been cut. Plus, you can cut grooves on top of knobs to have more sharp edges, and that can make a tire actually perform better than new ones.
But at some point you have pay to homage to Old Man Time. The sharp edge goes away very quickly, then you can cut the tire again, but you’ll start running out of rubber at some point. If you aren’t careful, you can also cause a knob to tear off. That means the KnobbyKnife is essentially a performance product more than an economizing tool. It’s an excellent piece of equipment for racers who want ultimate traction. With a little practice, riders can come up with special cuts and patterns that might give them an advantage. As for recreational riders, they tend to wear tires down farther, and when there’s not much rubber left, the KnobbyKnife doesn’t have enough material to work with.
Some tread patterns are harder to re-edge than others, but the KnobbyKnife can cut through any rubber very quickly.
You can refresh an old tire with the KnobbyKnife in about 20 minutes. You just have to have some rubber left to work with.