Avon’s Gripster tire is old as dirt and I’d guess has been used on BMW’s GS line almost since it’s introduction. Designed from the git as a dual sport tire, the AM24 features front and rear specific tread designs that should be mounted following the directional arrows on the sidewall. Both tubeless and tube type varieties are available, though the tubless ones can be used with a tube. If you’re riding an R100GS, you’ll need a 90/90-21 for the front and a 130/80-17 out back.
The profile of the front tire is nice and round, about the same as you see pictured for the rear. This translates to a very neutral steering feel, with no tendency to flop over in a corner, or to roll over to a certain point only to resist further efforts at turning. If the front tire looks narrow, that’s because it is. Just don’t let that slimness diminish your faith in the tire’s ability to hold a line when the road really starts to twist. These things stick like glue, letting you drag your toes at will. On a GS, that means you’ll be waaaaay over and will still have some chicken strip at the edge of the tire. In my book that makes the AM24 a great street tire, as good as any so called sport tire around. If you’re dragging the crash bars with dual sport tires, how much difference can a sport tire make?
The cleats are deep, meaning you’ll get lots of wear (maybe six thousand miles) before the tread’s gone, and you’ll get pretty decent traction when the road turns to dirt. Pushing the bike around the garage you’ll feel the tires bumping from knob to knob, and on the pavement they’ll sing a little bit, but nothing loud enough to be distracting. In fact you’ll hear nothing but wind noise at speeds over forty, and you’ll be hard pressed to notice any bumpiness from the knobs at speed.
But how does the Gripster do off-road? Like any dual sport tire, the AM24 is a compromise when it comes to sliding friction. If you’re used to hammering a CR500 through the whoops and ricochetting off berms, you’re gonna be disappointed. The Gripster is as good a dirt tire as the GS is a dirt bike. In other words, a Gripster won’t turn your GS into a CR, but it will do a pretty good job of getting you to a remote campsite at the end of a rugged Jeep trail, with all your gear, and getting you out again. Running the right pressure makes a big difference, and I’ve found that 32 psi in the front and 36 in back are about right. They don’t seem to run hot on the road with those pressures, so that’s generally what I use all the time. Go higher and the front tire will bounce around and act like it has a mind of its own, especially on gravel and loose rock.