Surly were one of the original players in the plus-sized world and are still pushing all kinds of fat wheels and tires in their range. The Dirt Wizard is currently the chunkiest, heaviest, and most aggressive 27.5+ tire I have used to date.
The Dirt Wizard is only available in a 3.0" width for 27.5" and 29", and there's also a 26" version in 2.75" and 3.0". The tubeless compatible, folding bead tire uses a single 48a durometer rubber compound, with a 60tpi casing that has added nylon sidewall protection. All that rubber comes at a price, and for $90 USD / €94.95 EUR the Dirt Wizard better have some tricks up its sleeve.
Dirt Wizard Details
• Casing: Folding
• TPI: 60 w/Nylon sidewall protection
• Compound: Single 48a
• Size: 27.5'' x 3.0''
• Bead: kevlar
• Bead Seat Diameter: 584mm
• Weight: 1210 grams and 1252g (actual)
• Price: $90 USD / €94.95 EUR
Design and Performance
The Dirt Wizard is currently the most aggressive plus tire on the market.
I had given up on plus-bikes for the kind of riding I do; they had some notable advantages, but were always too flimsy, prone to punctures, and I could never find anything that I preferred over swapping to 29" wheels with an aggressive/heavy set of tires. At the beginning of plus, most brands wanted to offset the added weight and rolling resistance of the bigger volume tires by using very low profile tread and lightweight casings to make tires around 800g.
The theory was this: more volume = lower pressures, lower pressures and more surface area = more grip. But, to counter that, many plus tires had a shallow tread, which equaled less grip, a light carcass that gave more chance of puncturing and less stability, which meant increasing pressures to get the right stability and puncture resistance. This leaves you back at square one, where I always wanted to try the added benefits of the plus size but combined with the existing benefits of the thicker casing and aggressive tread.
The downside of that combination is added weight, but there are riders who want plus-size grip and value stability and puncture resistance over weight savings, and there's also a whole new breed of plus-sized eMTB's that deserve tougher rubber.
The Dirt Wizard's carcass measures up at 2.65" and nearly 3.0" at the outside of the tread blocks on a 40mm rim.
The Dirt Wizard has a huge amount of spacing between the blocks which allows mud to shed easily. The 48a single compound rubber strikes a good balance between super soft and tacky, but maintains some durability and rolling speed.
Set on 40mm wide rims, the Dirt Wizard still maintains a rounded profile with the center blocks protruding much higher than the edge blocks. I found the ideal pressure was 20/22psi, meaning that on asphalt or harder terrain I was riding upon the center ridge of blocks and had surprisingly fast rolling speed. Running lower pressures, around 15psi (which is normally the starting point for plus tire recommendations) allowed the tire to compress too much, allowing the edge blocks to contact the ground too, this made a noticeable difference to the rolling speed. Over-inflated skinny plus tires means a very springy and un-damped ride, but the Dirt Wizards still had enough damping to calm them down as the pressure rose to 20/22psi.
The casing proved to be the toughest plus-size tire to date, although Maxxis Double Down casings in plus-sizing are just reaching the shelves. I never managed to cut the sidewalls or pinch them against the rim, which is the most common way to puncture a thin plus-tire, often close to the rim bead which can be difficult to repair or plug. I did manage to cut the tire between two side blocks above the line of nylon sidewall reinforcement, which required a tubeless repair patch on the inside.
The Dirt Wizard offers tons of braking traction, climbing traction, and a very smooth and predictable transition on the the edge, with a predictable breakaway point due to the rounded shape and huge blocks.
So who is the Dirt Wizard for? It's best suited for the rear wheel of an eMTB for massive climbing traction, good rolling speed and a tough casing. It could also be a good choice for plus bike riders who need a reliable tire for aggressive riding in soft and loose conditions and don't mind the weight penalty.Pinkbike's Take: