With four casing options, six different tread patterns, and numerous widths and diameters available – not to mention the four fat bike tyres it offers – the Bontrager mountain bike tyre range is about as niche-filling as it gets. Thankfully its mountain bike tyre line is nice and easy to understand. Firstly, there are three main casing styles. You’ve got G for Gravity, SE for Super Enduro, and XR for XC/Trail. From there, the number refers to the level of gnarness of the tread pattern. So the XR1 represents the lightest and fastest XC tread pattern Bontrager offers, and the G5 has the chunkiest and most aggressive tread pattern for downhill hoofing. I’ve had good experience with most of Bontrager’s recent tyre offerings, including the latest XR2, XR4, XR5, SE3 and SE4. The SE4 here uses exactly the same tread pattern as the XR4, so it’s also designed for loose and rocky conditions. However, this one comes with a different rubber compound and a reinforced casing, making it a heavier and burlier option for trail riding and enduro racing. For the past 12 months, I’ve been testing the SE4 in a 29×2.4in size. The same tyre is also available in 2.6in and 2.8in widths, and in a 27.5in diameter too. We initially received three pairs of SE4 tyres to use for the three bikes we featured in last year’s modern geometry 29er group test, though I’ve since dished out the tyres to several testers to amass some additional feedback. As such, the tyres...