Trek mountain bikes have improved dramatically over the past few years. Bikes like the Remedy, Fuel and Slash have been introduced to compete well in their categories. The Bontrager tires have lagged in this revamp a bit and some might say that they have held back the bikes from their full abilities.
Trek knew of this and they have installed members of their A-Team to work on the Bontrager tires and components. The goal was not only to bring the bikes to their full potential but also to make some of the best tires available for the aftermarket. Michael Browne, formerly on the mountain bike group, called to say that he was genuinely excited about this year’s tire line. He said the XR1 and the XR4 tires have been revamped and invited us to push them on some dirt corners.
The revamp started by recruiting one of the premier experts in the field, Frank Stacy. Stacy was a pro motocross racer for over 20 years and he moved on to tire development after that. He has worked for companies like Dunlop, Pirelli, Specialized and Kenda developing tires in the moto, utility and bicycle areas. A good article on his career can be found here from Motorcross Action. Stacy is a student of the tire development field and he focuses on lab testing, field testing and really identifying and quantifying the elements like traction and rolling resistance. His own site here called Stacy Testing gives you a peek at his methodology.
Ok, enough science. The UPS man arrived with a bunch of XR4 tires and we were rightfully excited. The tread pattern is much different from the previous generation as it is more modern with a simple, blocky and more open style. The casing is supple and tires mounted true. The Team Issue tires are light and are dual-compound. The center knobs felt normal but the side knobs were gummy and pinching them with your nail resulted in a scar that last many seconds as the tire slowly morphed back into its original shape. All the knobs had some siping or cuts to give them extra traction.
The 26er tires are called XR-4 and the 29er tires are 29-4. The ’4′ refers to their trail/traction abilities on a 0-4 line with the XR0 being an ultra lightweight xc race tire and the XR4 being an aggressive all mountain tire. There is also an XR-Mud for wet and muddy excursions.
This graphic from Bontrager explains the tire line-up very well.
The XR4 tire size line-up is as follows.
|29 x 2.30 (Team Issue)||120||69.99||Aramid||120||794g|
|29 x 2.30 (Expert)||60||49.99||Aramid||60|
|26 x 2.20 (Team Issue)||120||64.99||Aramid||120|
|26 x 2.20 (Team Issue TLR)||120||64.99||Aramid||120|
|26 x 2.35 (Team Issue)||120||64.99||Aramid||120||730g|
|26 x 2.35 (Team Issue TLR)||120||64.99||Aramid||120||760g|
|26 x 2.20 (Expert)||60||49.99||Aramid||60|
|26 x 2.35 (Expert)||60||49.99||Aramid||60||770g|
|26 x 2.20||60||34.99||Wire||60|
|26 x 2.35||60||34.99||Wire||60|
We mounted the tires to a few bikes, a Santa Cruz Blur TRc, an Ellsworth Evolution 29er and a BMC FS01 and have been riding them for the last month. The tires had good size and shape to them as they lived up to their 2.2 and 2.30 inch claims. We rode them in the loamy singletrack of Santa Cruz, loose fire roads of Los Gatos and wet trails of Waterdog and Skeggs in Woodside.