AGV Backmarker: Dunlop Q2…& A

If you read the last couple editions of AGV Backmarker, you already know that Dunlop recently launched a new tire, the Sportmax Q2, which is replacing the Sportmax Qualifier as the company’s top offering for street-biased sport riding. One of the cool things about being invited to that launch, for me, was the chance to catch up with two of the company’s top engineers Mick Jackson and Neill Rampton.

These two brainiacs weren’t just watching the test. They were working hard in support of it, doing thankless tasks like pulling wheels off bikes, mounting and balancing tires, and pumping gas. In the heat of a Nevada afternoon, I think they were grateful for the chance to take a break and answer a few questions. I was grateful to get out of my leathers for a bit and get some sense of the way they went about creating the new Q2, and where we might go from here:

Backmarker: Recently, we’ve started to see traction control and ABS braking systems on sport bikes. Are those trends influencing tire design?
Neill Rampton: I think they’re influencing measurement. The manufacturers want very specific information about how the tires behave, so we do a lot of friction testing for them on the traction trailer, so that we can measure what the maximum braking force is. So in terms of measurement, it’s more complex, but the design of tires themselves hasn’t been influenced so far.

Are modern sport bike tires becoming “dry” tires? How does a tire like the Q2 differ, compound-wise, from a tire like the (AMA-spec DOT-race) Sportmax GP-A race tire? Are the compounds a lot different because the Q2 may be used in the rain?
NR: The compounds are different, but they’re in the same family. Obviously we’re looking for more mileage. The Qualifier was our benchmark, so it had to have wet grip at least as good as that.

Mick Jackson: Having said that, the compound chemistry was changed to make the tire work in a much broader temperature range than a race tire, which works in a very specific range. The average guy in average weather will generate tire temperatures around 50 degrees C [122 F], whereas an aggressive rider at a track might generate 100 degree [212 F] tire temperatures.

Do North American riders differ much from Europeans in the mileage they put on, or the conditions they ride under? How would tires built for the U.S. differ from tires built for Europe?
MJ: In this [sport bike] segment, the riders’ demands are very similar. The big difference in America is that the roads are much straighter.

NR: In Europe, people tend to ride in all weather conditions too. The ride for pleasure, but also just to commute. Here in the States it’s a hobby, while in Europe it’s a mode of transportation.

Will the Q2 be sold in Europe?
MJ: It’s got the potential to be sold there, but it was created for the U.S. market.

It’s always been popular wisdom that tire grip and mileage are sort of a zero-sum game. Is that still true?
MJ: The Multi-Tread compound goes some way towards getting around that. With a harder center compound, the long straight roads don’t wear tires out so fast.

NR: It depends on temperature, too. There are two ways of getting grip. One is by making a very soft compound that penetrates the road surface, and the other is by hysteresis, which typically doesn’t affect wear; you can have very high hysteresis without much of a trade-off.

What is hysteresis?
NR: It’s energy lost as heat. So it’s damping [of the forces transferred between the tire and the road].

What kind of mileage should users expect to get from this new tire? Obviously there’s a range…
MJ: We don’t really test for worst-case and best-case scenarios. I would think that if you were very aggressive on a liter bike, you should still get at least 2,000 miles from the rear; the front you’d get more. Most people should get three to seven thousand.

When you design a tire, you work with a whole bunch of components: the belts, the bead construction, the compounds, the shape of the carcass… How do you go about designing a new tire? What comes first?
NR: It begins with trying to decide what the tire should do in terms of how it will handle the forces put through it. You do that with vehicle [computer] models and data from our data-logging motorcycles. Then it’s a question of how you get close to those forces. Profile’s the place we normally start. You’re trying to achieve a certain footprint at a certain lean angle, but that’s an oversimplification because you’re trying to get the best pressure distribution that you can, with a stiffness that will work with a certain suspension, and give it the right amount of stability. So it’s optimizing the contact-patch dimensions and pressure with the stiffness you need in that application.

Knowing the Qualifier and the Q2 as you do, do you see the two as radically different tires? Or is it an evolutionary step?
MJ: We worked with both front and rear of course, but the rear is really radically different. It’s multi-compound, it’s got a radically different profile; we had to make new machinery to produce it. So the rear’s a quantum leap. The front we just tuned; there was nothing much wrong with the old Qualifier, but we have improved it. Going back to your previous question, the profile, the construction and the compound are all developed hand in hand. If you have a radical profile, you need the construction and compound to support it. At some point they all marry, and you have a great tire.

NR: The thing with this tire is, we did a lot of predictive work before we started. At the time we started, we couldn’t make the tire we knew we wanted. Then we had to make new machinery; this is made with a whole new process.

Is the goal to have a constant, even pressure over the whole tire footprint?
NR: Kind of. The old Qualifier was linear up to a certain point, about 45 degrees of lean angle, then it rushed to a peak and fell off. The Q2 is much more linear, right up to 50, 55 degrees.

Is there a Holy Grail for tire engineers? What’s the next giant leap, comparable to the development of radial tires?
MJ: Eliminate the air, so no one could ever get a puncture. That’s not so much of a problem on the performance side, but on the functional side it would be a huge advantage.

NR: On the motorcycle side, we’ve found that big changes are often not that accepted. Change tends to be very evolutionary; maybe the things we think are big changes, from the outside looking in could seem fairly subtle.

MJ: What we’ve found in motorcycles is that often we’ll make a tire that doesn’t work, because the motorcycles aren’t designed to take advantage of it. After a few years, as chassis catch up to tires, the tire suddenly starts to work much better. We have to march in time with chassis and engines.

We’ve achieved greater and greater lean angles with street tires. Nowadays, street tires are capable of lean angles that would have only been seen in Grand Prix racing ten or twenty years ago. Correct me if I’m wrong, but as you get closer and closer to horizontal, doesn’t the marginal increase in cornering speed get smaller? And in any case, aren’t we butting up against motorcycle design constraints, since bikes can’t be leaned any further without dragging hard parts?
NR: I think it’s a tangent relationship, speaking trigonometrically.

MJ: There’s no point making a tire that can lean 80 degrees if the bike can only lean 50. We’re at a point of diminishing returns; I don’t know how much bikes have decreased in width in recent years.

NR: From a lap-time point of view, at that point it becomes a matter of getting better drive, or braking deeper into a corner.

MJ: It seems to me you’re talking about side grip and traction, which are two different things. Side grip has more to do with construction and profile, while drive is more about the compound.

Thanks guys.

Introducing Backmarker 2.0

Over the last few years writing this column, I’ve received lots of email from readers—most of whom went to some trouble to figure out how to reach me. Some of that mail was flattering, some critical, and occasionally those notes provided me with great story leads. The feature I wrote in the magazine, last winter, about racing vintage Honda 160s in Portland came about as a direct result of a suggestion made by a Backmarker reader.

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