For the past couple years, the off-road cycling community has been abuzz about the new semi-slick tires. The idea, born in the European racing circuit, is a bald-top tire with aggressive knobbies on the side. The tires looked odd, but everyone who has used them swears by them. The theory: No knobs mean less rolling resistance which means faster speeds. Sounds great in theory, but do they really work?

In search of the truth, the dirty crew and I headed to the hills with two pairs of Bontrager's Revolt SS tires and a pair of nameless knobbies. We tested the tires for braking, cornering, climbing, mud, racing and more. Here's what we found. The Revolt SS are very light and fast cross-country racing tires. The bald, knobless center rolls smoothly across hard pack, slick rock and pavement allowing unbelievable speeds while maintaining tremendous stability and traction. On the trail, the slicks worked great. Rolling resistance was greatly reduced and the light-weight tires allowed noticeably quicker acceleration.

Hill climbing is amazing. This is an area we expected to see the greatest performance drop, but it was quite the opposite. The Revolt SS tires actually climbed better than the knobbies. Santo who has always been a great climber, he's part mountain goat, flew up the hills even faster.

These tires corner as well as any knobby we've ridden. Once the bike starts to lean into the turn, the aggressive knobs on the side dig in and guide you around the corner.

Bontrager admits there are some limitations to the tire. For instance, the tire is not ideal for loose rock and gravel. The tire also adds a little more of a challenge for extreme technical riding.

Much to my surprise these tires handle mud quite well. I found no traction problems in the mud that my knobbed counterparts didn't also encounter. The shallow diamond tred translated to fewer places for the thick mud to pack in. Our test knobbies filledin with mud quickly greatly reducing any advantage knobs might have had. With the tire's narrow design it also allows for greater mud clearance than standard tires.

Bontrager also says they don't recommend the Revolt SS tires for heavier riders. When our 200 plus lb test rider tried these out he strongly disagreed. Not only did he fall in love with the performance, but he got better braking and gravel performance than light-weights like Santo and I got.

Another limitation is braking. The semi-slick pattern will break loose under hard braking more easily than full knobs. But, with a little practice we quickly learned how to brake better. Extremely steep descents, especially with loose dirt, are tricky as well. Braking was nonexistant on wet grass where the knobs still had plenty grip.

These tires are one of the best things to happen to trail advocacy. The smooth tread impacts the trail much less than large knobs. They don't dig as deep into mud and soft dirt and leave virtually no trace on hard pack. I strongly recommend these tires for fragile trails or trails at risk. Low impact riding is vital to the future of trail access.

These tires are truly remarkable. Everywhere I've gone with these tires people have come up to me and asked how I liked them. How do they work in the mud? Climbing? Technical? I simply reply they work great. And to my mom who saw them and said, "You need new tires. Those are bald." I say I wouldn't have it any other way. Skepticism is still high among the non-believers and all I can say to them is try the Bontrager Revolt SS tires. These tires are the best of their kind we've ridden.