Questions for a Tire Engineer: Why Can’t We Have It All?

Sponsored article presented by Maxxis Tires.

When it comes to tires, sometimes we just want it all.

Then a little thing called reality gets in the way. 

“But why?” we all cry. “Why can’t we have it all?”

So we asked someone who can tell us why: John Wu, an engineer by training and now director of product strategy for Maxxis USA. John’s tenure in the tire industry goes back to 2005, but he’s been running track events for 20 years. 

Maxxis currently offers two tires aimed at the hardcore market. The Victra VR-1 is a 200-treadwear model that has found a home in today’s endurance racing scene. 

For those who want to go faster—and aren’t saddled with the 200-treadwear requirement—Maxxis also offers the Victra RC-1, an R-compound track tire carrying just a 100-treadwear rating. 

John answered some of those “But why?” questions that often come up when discussing high-performance tires. 

GRM: Why can’t you just use a softer compound to make the tire faster?
Maxxis: We must first clarify that a softer compound doesn’t automatically mean that a tire has great dry traction. For example, winter tires usually use a relatively soft compound, but its dry traction properties aren’t stellar at all. 

To answer the original question, compound engineers can always come up with a super-soft tread compound with great dry traction properties, but the challenge of bonding this compound with other parts of the tire, mixing this compound in large volumes, and making sure this compound can be processed easily can be hard to overcome. 

GRM: Why can’t you stick your race compound rubber onto a street tire to make a really fast street tire? 
Maxxis: The issue isn’t that the tire companies can’t do it. The issue is doing it efficiently and with some profitability. 

The challenge is that race compounds are designed to work under specific conditions. From a production perspective, extruding this compound into a different shape—street tires have a different profile and deeper tread—and mixing this compound in great volume can be a challenge. 

From a usage perspective, the compound and construction may not be optimized for each other, so the footprint at the limit may not be ideal to generate the best dry lap times. 

A street tire also has deeper tread, so the tire can overheat and suffer from heat-soak and/or wear problems. On top of that, tread life and the long-term durability of the tire have to be considered as well. 

GRM: Why is it so difficult to engineer a fast tire? Why not simply copy the fastest tire out there and turn it up a notch? 
Maxxis: We wish it was that easy! We can always analyze our competitors and understand the mechanical properties and chemical makeup of the end product, but how did our competitor get there? The issue is similar to cooking: A chef can share a recipe, but it still takes the right equipment, the right process, and various chef skills to deliver at the same level. 

GRM: Why can’t you offer a tire that’s really fast, lasts for many laps, and only costs $75?
Maxxis: The trade-off between price–premium materials and manufacturing cost. Speed and wear continue to be an engineering/physical reality for the tire industry, but we are all working on shrinking the amount of trade-off. 

GRM: Why can’t you offer even more sizes?
Maxxis: Usually this is just a simple business decision when the extra mold won’t be paid off fast enough to turn some profit. Sometimes this has to do with production as well, when certain factories may have size limitations due to equipment. 

GRM: Why does tread design matter? 
Maxxis: For the GRM crowd that wants the fastest tire, a race slick is the ultimate solution if the vehicle is only used on dry surfaces. 

Unfortunately, once you need wet performance, engineers have to put in grooves to help expel water from the contact patch. The challenge is that most consumers don’t want their tires to sound like mud tires either, so designing and placing the grooves is a technology that continues to evolve.  

GRM: Why doesn’t a worn tire equal a race slick?
Maxxis: A worn street tire probably has thousands of heat cycles by the time it is worn down to a slick. Therefore, the compound probably doesn’t have much dry traction performance left due to thermal and oxidation aging. 

Also, some street tires feature something called tread base rubber. This is the layer of the tire that binds the actual tread to the cords and other inner components. So, when the tires are worn down to a slick, you may be driving on this tread base rubber, which has almost no dry traction properties. 

GRM: Why can’t I keep using my street tires even though they’re at the wear bars?
Maxxis: Once the tread is worn down to the wear bars, there is just not enough void in the tire to evacuate standing water to prevent potential hydroplaning. The pattern is also usually worn out so much that they’ve lost significant wet traction properties as well, so we recommend that our customers replace tires at the wear bars. 

GRM: Why can’t I drive my R-compound tires in the winter? 
Maxxis: Driving a summer-oriented tire—not just an R-compound—in the winter may lead to cracking issues. Rubber compounds have a temperature at which they become brittle like glass, aka the glass transition temperature; therefore, engineers develop compounds with various glass transition temperatures and then select the appropriate compound for the intended purpose. Since most racing doesn’t take place during winter, we don’t design R-compounds for winter temperatures.  

GRM: Why does tire performance fall off when driving many laps in a heavy car on a hot summer day?
Maxxis: Most tires will experience fatigue because the tire’s mechanical properties change when conditions get hot, and the compound traction properties can change as well. Of course, we can engineer or find new materials that handle heat better, but incorporating it into a complex production process at a reasonable cost is a big challenge.

GRM: Why doesn’t my W speed rating mean that I can drive at 168 mph all day? 
Maxxis: The way the industry certifies speed ratings is based on laboratory testing only for assuring the durability at maximum speed. Tire companies need to test at a specific load and inflation pressure and not have any issues running at 168 mph for a set amount of time. 

Since tire companies can’t anticipate all the different outside variables (weather, vehicle condition, tire condition), we recommend that customers see the speed rating as a reference and not a ticket to drive at the tire’s maximum rated speed for an extended period of time.

To read more questions and answers like these, head over to our previous tire discussion with Maxxis.

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