I’m going to level with you about something: Where road tires are concerned, review criteria are mostly peripheral: Did the tire flat easily? Did the tire weigh lots? Was it expensive? A road tire’s actual grip on asphalt isn’t much of a discussion point because so few riders come anywhere near sliding a tire on pavement. They all grip well enough in the dry that people back off of pushing the tire long before they begin to hit the differences in grip. What about the wet you ask? Most road tires don’t have especially great traction in the wet, but what really determines how well the tire will hang onto a wet road isn’t its durometer (a measure of how grippy the rubber is), but whether or not there’s a coating of oil, sand or ice.
Mountain bike tires suffer no such ambiguity. Sure, you can ride slicks on hero dirt and come up thinking a tire’s tread includes cat claws, but when conditions turn dusty, hard or muddy tires can perform quite differently.
Take, for instance, the Pirelli Scorpions I rode last fall. Pirelli has been known for making amazing tires for other two-wheeled devices, but they only recently entered the bike market. I mounted the Scorpions just as the end of the summer, the trails were dry and dusty. Most of the tires I’d been riding were breaking loose under hard braking. Finding a tire that could handle hard braking on dust over hard pack isn’t hard to do so long as the tires are relatively true. But put 200 miles on them and you soon find out whether they can hang on.
The tires I rode are the Scorpion Trail R and Trail S. The Scorpion is collection for four trail-oriented tires. The Trail R is a rear-specific tire and the Trail S is a front-specific tire. Where the Trail R is designed around smaller blocks spaced closer together for smooth rolling and because rear tires simply don’t need the blocks to be as large due to the weigh bias on the rear wheel, the Trail S features larger blocks spaced farther apart and oriented so their long axis runs the direction of the tire’s rotation. The side blocks on the Trail S are notable for their size.
Here’s what I really don’t like in a tire: coming off any sort of drop, no matter how small, and feeling the front tire touch down and slide sideways. On a scale of 1 to 10, my pucker factor is a solid 12. I want that front tire to touch down and roll, nothing else. If I feel that tire slide I’m going to back off from pushing the bike, which is where I think the fun begins. Mountain biking and timidity don’t make for a cute couple.
What impressed me about the Trail S was how as I moved from hard trails with loose dirt sprinkled over the top to softer trails that were often covered in redwood duff the Trail S offered precise cornering. For as long as I was willing to trust the tire, it seemed able and willing to carve a line with the confidence of an X-Acto knife.
The Trail R, by nature of being a rear tire, is a bit harder to quantify the performance of. There are two performance factors that I look for, though. The first is whether the rear breaks away under hard braking in a turn. Granted, I don’t hit the rear brake as hard as I hit the front, but I want the rear tire to handle some of the stopping duties as I rail tight turns and if the tire breaks away, causing me to oversteer, that’s a knock against it.
A brief aside: I get that sliding tires can be a terrific way to turn at speed, especially if you have the skill necessary to handle a two-wheeled drift.
But.
In many places, sliding and skidding is awful for the trails and that’s very true in most of the places I ride. I don’t want to be known as “that guy.” So I really try to carve turns rather than go tube socks on wood floor.
There is a spot at a place I ride consistently where near the top of a 50 meter hill the grade hits a solid 35 percent. It’s just the sort of place that if my weight is a bit too far forward I can slip the rear tire. It serves as a kind of wear indicator for my rear tires. On a couple of trips up this hill I leaned as far forward as my hip flexors would allow. And you know what? No spin.
The tires come in two sizes—29 and 27.5, and both are 2.4 inches wide. They employ Pirelli’s ProWALL sidewall reinforcement, which is a layer of Nylon. The upshot is that while it increases the tire’s durability for those of us constantly scraping by rock, the layer also add stability to the sidewall, making them squirm less at low pressure. And while multi-compound tires are the rage, these tires use a single compound—SmartGRIP—developed for motorsport, that in my experience balanced traction with durability as well as any mountain bike tire I’ve ridden. One thing I did not encounter in my miles on these tires were any broken or torn blocks.
Anyone worried that these tires might not be lightweight should hit the back arrow, stat-ish. Pirelli says the Trail R comes in at 930g and the Trail weighs 950g; they were rather unwieldy to try and weigh, but this is close to what I got with rubber bands holding the tires in a weighable shape. They typically go for around $70—pricing seems to be pretty consistent on the web.
Final thought: A great option that’s actually in stock with some vendors.
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