This month in “Tires 102,” we sat down with Brian Fleck from Dunlop Tires. Brian has been at the core of Dunlop’s tire development for motocross and off-road race teams for over 35 years. He’s been an integral cog at the high-end racing level at every facet of racing—from Supercross to GNCC competition. We tapped into his expertise looking to boil down the technical issues into understandable answers of some of the most asked questions concerning tires.
Dirt Bike: How do I choose which rear tire is right for me? There are so many choices of tread patterns that are terrain-specific, it’s confusing.
Brian Fleck: In off-road, there are more choices because the terrain is so varied. For slower, tighter East Coast and Midwest trails, an intermediate tire is the best choice. There are a wide variety of terrain and amounts of moisture. An AT81 is a good all-terrain choice. The MX33/ MX34 intermediate to soft are also good for these trails/races. West Coast and faster events we would recommend a hard-terrain- or desert-type off-road tire. These would include the AT81 RC, D908RR or MX53. These tires have larger blocks and hold up better than intermediate/soft-terrain tires. Front tires for these races depend on how much sand is on the trail/course. Most riders use an intermediate front. For pure moto, we use intermediate to soft for 85 percent of the tracks.
DB: For the enduro rider, what’s more important, high wear or high grip?
BF: It depends on the results the rider wants. If race results are the primary desire, then it’s all about grip. For technical and rocky terrain, the EX tires are best. Dunlop has two—the Enduro EN91 EX for softer terrain and the AT81 EX with tighter knob spacing. Both feature a super-soft rubber for enhanced traction. You can manage the wear if you don’t abuse it with the throttle. Many trail riders are using EX tires because they make difficult terrain easier to ride.
DB: I’m on a budget, I want the best traction, and I want it to last. Is there one tire that does it all?
BF: Compromise is always tough. It is hard to get best performance and best durability out of one tire. Normally, a hard-terrain tire like the MX53 works okay and has better durability than intermediate to soft tires. If a tire shows little to no wear, it’s normally a sign it does not have the best performance. Tires will wear when they are providing good grip.
DB: How do I choose the right rear tire size? Taller sidewall or bigger contact patch, what works where and why?
BF: In soft and rutted conditions, a smaller, narrower size is sometimes better. The narrower tire does not grab the edges of the ruts as much. In SX, many 450 riders use a 110/90 rear tire because the whoops get cupped out with many edges that grab the tire. When the tracks are drier and not as rutted, the wider rear works better on the 450s under acceleration and braking.
The 120/80 is firmer than the 120/90. The taller sidewall of the 90 is plusher, and we use these in outdoor MX for sure. The 90 also has a longer footprint, which improves start grip/performance.
DB: In off-road, fatty fronts are popular. Where and why are they better or worse?
BF: They have a bigger carcass, which absorbs impacts from rocks and roots better. They also are good in EX-type terrain where traction is at a premium. The negative is heavier steering and not as responsive in tight terrain. Many full-mousse inserts do not work as well in the bigger front tires.
DB: There are so many variances in what people say to run for air pressure. In off-road, I get advice saying to run high pressure to alleviate flatting. Is there a guide saying what pressure is too low or too high?
BF: We like 13–13.5 psi for front tires and 12.5–14 psi for rear tires for most conditions. If it is extremely rocky, try more air in the rear or use a double tube (a normal tube wrapped by a cut inner tube). We use this in some SX where we do not want to use full mousse, but want a little more flat protection.
DB: Should I run super-thick tubes to keep from getting flats?
BF: They are a good choice for off-road. The feel is still not as dead-feeling as a full-mousse insert. Interesting, though, many top offroad racers like the dead feeling of a mousse especially in rocky terrain.
DB: Do dirt bike wheels need to be balanced (like a car) after installing new tires?
BF: For high-speed off-road races, balancing the wheels would be a positive. For moto, not so much.
DB: What is better, thick tubes or mousse inserts?
BF: It depends on what feeling the rider wants. Most riders like the rebound and absorption that inner tubes provide. Full-mousse inserts are heavier and give the rider a dead or non-responsive feel. They do free up the rider, as he can attack nasty terrain without fear of flatting, but there is a learning curve with them, both in the ride and the installation.
DB: How do I pick the right front tire? I ride MX, off-road and some desert. Is there one that does it all?
BF: Front tire choice is very rider specific. You should try several front tires to find the one that has the traction and steering characteristics that feel best for you. An intermediate front is a good place to start. At the pro level, we have more front tire choices than rear tire choices. Riders find a front tire they prefer, and they use it everywhere.
DB: How often should you change your front tire? They seem to last much longer than the rear knobby.
BF: They do not wear as fast as rear tires. You need to see how much the sidewall starts rolling as you put more time on the tire. The carcass starts breaking down even if the knobs are showing minimal wear. Check your rim after riding to see how much the tire is rolling over the edge of the rim. Some riders will increase front psi to compensate for the tire carcass getting softer.
DB: Are all tires directional? How important is this?
BF: It depends on the pattern and design of the tire. Most soft-terrain tires are directional, like our MX14. The pattern is designed to dig better in one direction.