MO Tested: Bridgestone Battlax Adventure A41 and Sport Touring T31 Tire Review

Bridgestone has just introduced two new tire families to their lineup – the Battlax Adventure A41 and the Battlax Sport Touring T31. The driving goal behind these two new models was to improve on their outgoing predecessors’ overall performance by focusing on and upgrading wet grip and handling with an emphasis in low temperatures. On top of that, Bridgestone set out to increase feedback and contact feel across all lean angles, all while maintaining stability and no sacrifice on wear life. Sounds easy enough, right? Well…

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We got the chance to ride and test the Adventure A41 tires first, so I’ll start there. Can you imagine a better place to test adventure tires than Morocco, outside of Ouarzazate, on the outskirts of the Sahara Desert? But before feeling how well the tire works, we have to understand how it’s built. The carcass of the A41 tire is created with mono-spiral belt (MSB) construction, which means that a continuous single strand of cord is wrapped around the circumference, and serves as the belt of the tire. This one-piece construction eliminates overlapping of belts, seams and joints. As a result, Bridgestone says MSB constructed tires are lighter than conventional multi cross belted tires, offer more stability, minimize heat generation inside the tire and give higher shock absorption.

Moving outward, both front and rear A41 tires are constructed with multi-compound layer technology called 3LC (three layer compound). Basically, there’s a harder rubber compound across the base and in the center, and a softer compound on top of the harder one on each shoulder. The softer compound sections offer improved grip when leaned over while the harder compound in the center and base provides longer wear life as well as added stiffness for stability and feel. So far pretty standard motorcycle tire construction practice, but here’s where the A41 starts to differ…

Like mentioned before, Bridgestone’s goal with both the A41 and T31 tires was to increase water drainage, wet performance and overall feel with a focus in low temperatures. Consequently, Bridgestone revised the tread pattern over the outgoing A40 tire by increasing the sea/land ratio at both the front and rear tire’s shoulder area. There’s now incrementally less rubber in contact with the road’s surface at the tire’s shoulders, but more area for water to be dispersed. Since more traction in wet conditions is an uphill battle, Bridgestone implemented its latest silica nanotechnology, which works at the molecular level to improve the dispersion of silica in the compound mix. The effect is increased rubber flexibility which improves the contact feel of the surface and simultaneously enhances grip in wet and low-temperature conditions.

After extensive testing at its proving grounds, Bridgestone claims the A41’s overall contact patch is 5% greater, with a 9% higher wet friction coefficient and an 8% faster wet lap time over the A40 predecessor – not bad. Unfortunately, (or fortunately, depending on who you ask) being in the desert in Morocco, we didn’t get to test the A41 in any wet conditions. However, it is an adventure tire, and we certainly tested its off-road capabilities. Bridgestone says the A41 is a 90% on-road / 10% off-road tire, which is rather obvious looking at the tread pattern, but it makes perfect sense because Bridgestone’s extensive research has shown this is the terrain ratio an overwhelming majority of ADV riders typically traverse, despite how hard core some riders claim to be. There is, however, a knobbier adventure tire in the works.

Our ride in Morocco was closer to 50/50 or 60/40 on/off-road, so we definitely got a better taste for what the A41 is capable of where the pavement ends. Mind you, though, being a 90/10 biased tire, we kept our off-roading somewhat mellow. We rode about 90 miles off-road through incredibly loose, rocky and rutted roads. These roads snaked their way up and over mountains and spilled into giant flats, so we got to see just how well the A41s maintained traction under hard braking coming into corners as well as leaned over while accelerating through the choppy, loose stuff. We also tested what kind of stability they offered and how well they deflected bumps and rocks at near triple digit off-road speeds (at times).

You’re probably thinking, “Yeah right, triple digits my ass…” There were times when we were on a stretch of road (if you can even call it that) with absolutely nothing in sight for who knows how many miles. It was flat as a pool table and straight as an arrow. Bridgestone touts the A41’s high-speed stability as one of its greatest strengths, so why not put it to the test? Granted, we were riding full bore adventure bikes with premium suspension that obviously soaked up bumps and square edges well. The quality suspension quelled the terrain’s vibrations and made it easy to gauge the feel and traction the tires were providing.

I came away rather impressed by how well the A41s handled the high-speed chop in terms of stability – the faster you went, the better they felt. Deflections off rocks never got squirrelly – just don’t grab a handful of front brake. Traction is another story… Being a street-biased tire, you’re not going to want to bury the front end coming in hot to a turn, but with the right amount of braking pressure, the front tire grabs loose terrain surprisingly well. In one instance, a decreasing-radius turn came up on us quick and I needed to scrub speed fast because there was nothing stopping anyone from launching off this cliff Evel Knievel style. I braked hard, trying not to lock up the front, but I also had to keep leaned over while turning in the process.

It’s hard to explain the feeling, but there was an instant where I thought, “Oh shit, it’s actually gripping (!)” and providing more dirt traction than I was expecting from a street tire. Needless to say, it was a reassuring moment that instantly gave me more confidence in the tire. Again, it’s a 90/10 biased tire with emphasis on wet traction and feel. The tire’s water-siping grooves are much wider and deeper than a road tire’s, which in turn offers greater off-road traction, even if minimally. The same goes for traction in the rear while accelerating. If you don’t grip it and rip it, but rather give the bike calculated throttle, the A41 rear hooks up in the looser stuff in a pleasantly surprising way. In fact, controlled drifts became rather frequent (so long as you could see around the corner).

These rough, cheese-grater type roads is where I felt the A41s really shined. The softer shoulder compounds on the front and rear, paired with the increased sea/land ratio with wider/deeper grooves hooked up well – much better than a full-on street tire would have I imagine.

The roads were a single lane essentially, so blind turns were to be taken extra cautiously, especially when (not if) a truck happened to be coming the other way – definitely a few butt-puckering eye-openers. But a car or truck startling you was nothing compared to the near heart attack a herd of goats or sheep darting into the street induced. Like the opposite of a deer in the headlights, free roaming goats and sheep would see or hear us coming and kamikaze into the road at the last second from any direction, creating a Frogger / Minesweeper-like obstacle course that made you wish you’d brought a change of underwear. Oh, and the wild dogs, don’t get me started on the wild dogs – they’re nuts!

Both the front and rear T31s have increased sea/land ratios on the shoulder, and slightly decreased ratios in the center, but the biggest difference the T31 offers over the outgoing T30EVO is the groove angles of the water sipes. The T31’s new grooves provide a bigger contact patch with up to 7% more camber thrust from zero degrees to full lean angle. Camber thrust, in simple terms, is the movement of a tire perpendicular to the direction it is rolling. So, in other words, the redesigned grooves provide 7% more steering power and grip in whichever direction you’re turning, which means you can rail a turn that much harder.

Additionally, according to Bridgestone tests, the improved silica dispersion within the rubber compound paired with the redesigned grooves offer a 3% higher friction coefficient on wet surfaces and a 3% faster lap time on a wet track. Again, we didn’t see a drop of rain in Morocco, so wet handling is yet to be tested. However, we did get to see how well the T31 could boogie by carving up some winding roads.

Verdict? The T31 front served up a super planted feel in any corner at any speed. At first, we started off easy to get our bearings because the day before we got accustomed to riding bikes with taller, skinner fronts that you obviously couldn’t push as hard into corners. But now that we were on full-street 17s, it was off to the races. With each turn, I was able to brake a little later and deeper into each corner while simultaneously getting on the gas sooner and harder. The rear felt nice and planted too, but the front was what really stood out.

It was point and shoot. In tighter-radiused turns with greater lean angles, the front tire felt like it was actually pulling you through, which meant you could really hang it out and let the motor eat without standing the bike up as much. The positive steering feedback translated to nice, swooping turns. However, the planted feel the front tire offered meant you could really throw some body English and assertively flop the bike into a turn with confidence, knowing the front was going to bite the pavement hard and stick.

Overall, the T31s definitely put an emphasis on the ‘sport’ in sport touring and proved to be a solid pair of confidence-inspiring tires. As for the life and mileage an owner of the Bridgestone Battlax T31s or A41s can expect? We don’t know, because it really depends on how and where you ride, but in the end, we’d rather sacrifice a bit of tire life for performance’s sake, knowing we can trust the tire and push envelope. And that’s just what Bridgestone has done, they’ve pushed the envelope.

In Gear

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