It’s funny to watch things evolve. Or devolve, depending on how you view the filled-yet-not-full glass of water. Plus-size tires started with a less is more through more mentality. More contact patch meant less tread. Early versions looked like massive preposterously large modern-day gravel tires with their file-tread-esque patterns. They had to kinda-sorta seem light or at least look fast in order to tempt people into trying them. And at least the first the 27.5+ sighting hoped to fit within existing 29-inch bikes, so side knobs went by the wayside.
Then along came 27.5-inch full suspension plus bikes designed around 2.8- and 3.0-inch tires. Damn.
Today, you can even buy Maxxis Minion DHF 2.8 27.5-inch tires, quite the knobby plus-size pattern. So how does this influence plus, and isn’t this about the Bontrager XR4 tire?
The Bontrager XR4 2.8 27.5-inch tire isn’t a downhill spike and it also isn’t a gi-normously voluptuous oversized gravel tire. It’s a trail tire with a trail tread. And it seems quite fitting for plus-size full suspension bikes of late.
The tread pattern is open but not massively open. The block height is also tall yet not towering. It strikes a balance, and at a weighed 926- and 928-grams, it’s reasonable for a 2.8-inch trail tire.
When first installing the tires, I made a point of poking and prodding the casing between my fingers, working from bead to in-between tread blocks in search of thickness. The XR4’s are incredibly even. No hot spots, no extra globs of rubber. Some tires have a robust casing beneath blocks and feel anemic on sidewalls, others the opposite. Others still, thick all the way through. Compared to the Maxxis Rekon 2.8 27.5-inch EXO TR tires on the Spot Mayhem 27.5+ I’ve been riding, the XR4s feel burlier from bead to bead. Compared to a WTB Bridger 3.0 27.5-inch TCS Tough High Grip tire, the XR4s were discernibly thinner in casing thickness. Not surprising--they reside between the Maxxis and WTBs in weight.
On the trail, the mid-width spacing and pitch of the XR4’s block placement was certainly appreciated. Even spinning pavement to the trailhead, the open pattern is somehow just tight enough to avoid tractoring or the dreaded cloppety clop. ‘Tis a technical term, cloppety clop. On hardpack, they’re quick. There’s a hint of ramping to the central-most squares that may assist in this speed, but overall I felt more atop a shelf, pointing to proper spacing. They still punch through dust as things get slightly deeper. In kitty litter, there’s enough spacing to claw for traction and they certainly conform to large, off-camber rocks at slower speeds--as to be expected from a plus tire. Siping of the medium-sized blocks may help with this. Braking was consistent and dependable, no noticeable squirming or weirdness shutting things down while changing direction. For pressures, I settled on 15 psi for the front and 17 psi for the rear. I’m 185 pounds and always carry too much.
Sadly, I can’t speak to foul weather performance. Rain’s strictly forbidden ’round these parts. The XR4’s even spacing shouldn’t take issue with mud, equidistant open spacing points toward clearance.
Sounds pretty ideal, eh? No discernible drag, good braking, off-camber traction, what’s not to like? My gripes are minimal--the tires have a somewhat more round profile. Rather than sinking right into the aggressive side knobs as one would with more flat-topped tires, you have to go hunting a bit more to find the XR4’s side biters. It’s a blessing and a curse. Getting too loose on a descent, my front end went ping-ponging off to the side at an angle where I was sure I’d entirely lose it. Those lower side knobs certainly did their job though. They clawed their way onto an off-camber rock at an unheard of angle as I was was just barely still grasping the bars. I was impressed. But I also didn’t get the gluttonous immediate dig-in sensation felt on flat-toppers.
It is very worth noting that I ran these tires for the entire duration of the test on 40-millimeter inner-rim-width Mavic XA Elite 27.5+ wheels. 40 millimeters is a great width for 2.8-inch tires, but going to a 45-millimeter inner-rim-width would further flatten, or ‘square out’ the profile of this tire. It would also increase the width--sitting on 40’s, the XR4 2.8-inch tires measured 2.7-inches wide.
Final nitpick? The amazingly even spacing doesn’t make for the largest cornering channel when moving from central to intermediate to side knobs. This is just fine as there is no shortage of traction with this tire but it didn’t make for the unmistakable set it and forget it lean angle of cornering found in tires with cornering chasms, not to be confused with cornering channels. Again, this is not a repurposed downhill tread now in plus mode, so insatiable voracious hands-free cornering is beyond the scope of most trail tires.
All in all, the Bontrager XR4 Team Issue TLR 2.8 27.5-inch tires are great all-rounders. They roll quickly, are predictable, brake well, provide excellent hold off-camber and are a reasonable weight with ample protection. If you’re hunting for a downhill-cornering tire with a flat-topped profile, either run a wider rim or look for just that--a downhill-cornering tire with a flat-topped profile. For all else, and all in general, the XR4’s are great.