Dunlop Dirt Bike Tires: MX32/ MX52 Geomax Line

Dunlop Dirt Bike Tires Continue to Lead the Way

Dunlop combines pro performance with public availability

By Chris Denison
Photos by Adam Booth and Courtesy of Dunlop
Both the new MX32 and MX52 have an aggressive look, with the Progressive Cornering Block Technology (PCBT) visible on all but the side and mid-shoulder knobs.

For the last few years, Dunlop dirt bike tires have absolutely dominated professional motocross and supercross racing. Nearly every top rider at each AMA event is running a Dunlop, and the tire giant is often one of the first entities that a rider gives credit to from atop the podium. However, Dunlop recently identified a growing gap between what their top racers were running on the weekends and what the average customer is able to purchase at their local dealerships.

With that in mind, the product engineers set about creating a new line of Geomax tires that would be suitable for the highest level of competition while also being available to the general public. The end result is the MX32/ MX52 Geomax line, which was recently introduced to the press on a sunny morning at Milestone MX Park in Riverside, California.

Broc Glover, Dunlop’s Senior Manager, Motorcycle Racing, Off-Road and Ken Vreeke (right) explain the benefits of the new Geomax technology.

Previously, Dunlop’s Geomax line consisted of three main patterns: The MX31 (for sand and mud), the MX51 (an all-around/ intermediate tire) and the MX71 (for hard-packed, blue-grooved conditions). What the new line does is replace those three tires with just two different patterns, the MX32 and the MX52. Both Dunlop dirt bike tires feature common technology, but there are a few unique differences that set them each apart. Designed for soft-to-intermediate terrain, the MX32 rear tire features increased bending within each block due to the elimination of the internal tie-bars, which prevent contact feel and performance in muddy conditions.

Additionally, fewer blocks are now needed in the center row because of the multiple block distribution with essentially varies the pitch and angle of each center block. On the front tire, the mid-shoulder knobs are staggered and are sized differently for better grip and more response, while a chiseled shoulder block (technology that we previously saw on the MX31 tire) was designed to grip better at a lean. On the more hard-packed end, the MX52’s staggered center block distribution is aimed at helping the tire absorb impacts, such as those found in whoops and square-edged bumps. The front tire also features a unique knob design that works in just one direction for optimum traction.

Dunlop’s team of pro tire fitters spooned on fresh rubber for the press to try. These guys change tires easier than most people change lanes while driving!

All that said, the main benefit of both new Geomax tires is the concept of “a block within a block” knob, which is essentially a patented process that layers a small, stepped block on top of an existing knob in such a way that each knobby features progressive control in terrain types. Broc Glover, Dunlop’s Senior Manager of Motorcycle Racing, Off-Road, explains this Progressive Cornering Block Technology (PCBT): “This Progressive Cornering Block Technology (PCBT) came about from load tests that show how a tire puts pressure on the ground.

We started noticing that the external portions of a knob had all the pressure, while the internal portions of the knob actually had a void of pressure. By actually elevating the inside of the knob, we were able to develop an aggressive tire that is good for starts and good for straight line performance, but also works very well when the track gets harder and the bike is leaned over in slippery conditions.” Essentially, placing a small knobby on top of an existing one has brought out a whole new level of performance from this rubber.

Dirt Rider Associate Editor Kris Keefer puts the new MX52s to the test. The Milestone track was a medium to high traction level mix of packed clay and loamy berms.

“The MX32 front tire was first brought out for the Daytona Supercross of last year,” Broc explained regarding the tire’s racing history. “Ryan Villopoto, Ryan Dungey and Marvin Musquin all put it on, and the next thing you know Villopoto has not raced a pro race without that tire. At Anaheim One of this year, the entire 450 podium was nothing but MX32 tires, front and rear. We’ve never had this kind of consensus among racers, who are usually quite picky and don’t always agree on tire choice. Now, with this new group of tires, it’s much easier for us to supply the pros because they all agree on what to run. It’s really been a blessing for us.”

The new MX32 front now covers the same amount of terrain as the older MX31 and MX51 tires did combined.

On the day of Dunlop’s intro, the Milestone MX track featured a medium to high traction level with packed clay and loamy berms. Dirt Rider brought out a variety of 125cc two-stroke, 250 four-stroke and 450 four-stroke machines, allowing us to try the MX32 and MX52 tires in several sizes. Here, we noticed that the MX32 front tire improved front-end feeling and traction over the previous MX31 and MX51 versions in all conditions. The new tire actually makes the steering feel "heavy" because the tire is at maximum grip under initial lean.

This took some time to get used to, but for those who like to steer with their front end this tire is great for a wide variety of terrain. The MX32 can be leaned over more to each side with less pushing than the older Geomax. Under flat/ harder type corners the tire will comply with front end steering type riders’ demands for traction. We did feel some under-steering in ruts as the front tire would grab and want to pull the front end down more than the MX52, but we still felt that the MX32 was a better choice, even when the ground got hard packed or in slippery/ muddy situations.

A closer look at the MX32 rear shows the new PCBT (Progressive Cornering Block Technology).

The MX32 rear offers great forward bite in intermediate/soft terrain ruts and corner . Lean traction has also ben improved over the MX31 or MX51. You can lean more (sooner) coming into a corner and remain planted to the track. The "block within a block" side knob design seems to work well under every lean angle we could try at Milestone. Again, this tire works pretty well in hard pack conditions where you can still lean the bike into ruts. The only complaint we had is that when the track surface was hard pack, we could feel the carcass of the tire roll when accelerating from flat corners, when really pushing down on the rear end. This lets the rear end slide out more than we liked. We could feel the carcass of the tire really give and absorb on bigger type bumps. It has a comfortable feeling from soft to hard pack. ‘Predictable’ is a great word for the MX32 set up.

Dirt Rider Editor Chris Denison airs out the MX32-equipped RM-Z250 test bike. The track became much harder and rougher throughout the day, with a few slippery spots from excess watering.

The MX52 front gave us improved traction on intermediate/hard pack conditions. Lean angle is improved and the tire will actually bite when there is nothing to bank off of on slippery/hard flat corners. There is not that "grabby" feeling on this tire like there is with the MX32. It can lean well in softer loam but will push a little on the exits of corners. We honestly still would use the MX32 front tire in hard pack conditions, though. On the back, the MX52 rear was impressive. When the track dries out this tire does has better forward traction than the MX71 or MX51. Lean angle traction is improved over the MX71 and the tire will give you traction when you need it in hard pack conditions. The "block within a block" side knobs offer control under acceleration in flat corners. Our testers could actually feel the tire digging in and trying to gain forward momentum without getting excess wheel spin. Unless the conditions are really hard everywhere on the track we still would prefer the MX32.

Now that’s a lot of tires!

Looking ahead, we’re excited to continue to test with the new tires, but from what we’ve seen Dunlop did a great job of reducing the complexity of their product line while also improving upon their already-proven MX tire technology. There’s always a delicate balance in tire construction between durability and performance, and both the MX32 and MX52 tires strike that balance quite well. Stay tuned to the pages of Dirt Rider for a full test on these tires, where we’ll also evaluate their wear over a prolonged period of time.

Big thanks to the Dunlop crew (and their hard-working tire changers) for giving us a glimpse at the new line. Stay tuned to both Dirt Rider magazine and as we continue to evaluate the new MX32/ MX52 Dunlops.