How are treadwear ratings determined? It’s not how you think.

First, Some Good News

Before UTQG ratings were even a thing, DOT approval was the minimum benchmark for a street tire. The desire to run motorsports competitions on tires that could be driven practically on the street to and from venues was key for successful amateur events. Most participants wanted no part of trailers, tow vehicles and unstreetable racing slicks.

So what defines DOT approval? First off, the approval part of the moniker is misleading as there is no official government approval process per se.

Section 139 of the Federal Motor Vehicle Safety Standards lays out the performance characteristics that a tire must meet to bear the DOT mark on its sidewall, but no actual testing data is submitted to NHTSA by the tiremaker. Instead, there’s a back-end compliance checking program where NHTSA sources tires at retail and tests them against key metrics.

If found to be noncompliant, lawyers get involved and penalties can be served. Given this, major tiremakers are keen to stay conservative in their internal testing and engineering processes to avoid potential embarrassment and financial consequences.

DOT-marked tires must survive undamaged at high speed, high load and high temperature while properly inflated, but also at low speed and low pressure while underinflated (20 psi). Endurance is confirmed via long runs on a machine, and a plunger is used to verify puncture resistance.

That said, the minimum DOT specifications are antiquated, and it’s not all that hard to meet them with modern methods. In fact, a DOT-marked Hoosier A7 or Yokohama A055 is quite similar to the racing slicks those two companies make. They also both state “Not for Highway Use” right on the sidewall, thus keeping the lawyers at bay.

Photography Credit: Andy Hollis

The European Union has a much more modern set of road tire requirements and compliance procedures, which result in an E mark on the sidewall plus a series of ratings. Engineering and test data must be submitted for approval, and compliance checking is performed on the back end. R-comps like the A7 and A055 can have trouble meeting the strictest of those standards and do not bear the E mark, while most of the current crop of 200tw street tires does.

Photography Credit: Andy Hollis

For the U.S. market, major tire manufacturers have formed trade associations to lobby for improvements in NHTSA’s efforts–but also, in the absence of that, to check each other’s work. If any of them goes too far from the norm, it’ll be called out by its peers.

The Tire and Rim Association is one such organization, promoting standards for tire and wheel dimensions. That way, consumers can be confident that a replacement tire of the same marked size will fit properly on their rim and inside their wheel well. The European Tyre and Rim Technical Organization performs a similar function across the pond.

Small, specialty tire companies that are not members will sometimes push the limits of these specifications, producing tires that exceed the physical widths typical for a given marked size. Hoosier is the most widely known example and caused NASA to establish physical template-based sizing for its motorsports classing.

The U.S. Tire Manufacturers Association is the industry’s other major trade group, representing its members both in the public eye with information campaigns as well as before federal and state regulators. It also does compliance checking, especially of nonmember import brands. The results of those tests are not made public, but regulators are informed of any irregularities discovered.

UTQG: Real or an Illusion?

Unlike DOT regulation compliance, which is a safety program, the Uniform Tire Quality Grading system began as a consumer information effort to better educate buyers purchasing tires for their specific purposes.

All tires are compromises, and none is best at everything. Want better traction? You’ll need to pay the price of durability and heat tolerance. Want a long-lasting tire that can be used in a wide range of temperatures? It probably won’t be the stickiest.

And tires that do lots of things really well are typically the most expensive to build, needing significant development time to get the combination dialed in perfectly. This is typical of OE fitments, though new car sales spread those costs across a larger volume than replacement tires.

The UTQG system was designed to make all of this simpler for tire buyers. Testing procedures were spelled out for each of the three grades commonly seen on street tire sidewalls: Traction, Temperature and Treadwear.

Traction is determined by skidding a tire across a calibrated wet surface and measuring the coefficient of sliding friction. Temperature is measured in a high-speed endurance test on a machine at ever-increasing velocities. The higher the speed it can tolerate, the better the rating.

Rating treadwear is more complicated, with subject tires fitted to a convoy of three vehicles, which drive a prescribed route alongside a single vehicle fitted with a standard control tire. These tests are typically conducted by third-party specialists under contract from tiremakers, and the test routes are in San Angelo, Texas.

Effective when originally rolled out in 1978, the test has become outdated as it encompasses only 7200 miles of street driving–a small fraction of the lifetime of typical modern tires. Mileage is compared to that of the control tire and then extrapolated to generate the final relative treadwear rating for the sidewall. But the process doesn’t stop there, as this number is a maximum. Tiremakers are allowed to de-rate a tire for marketing purposes. The general buying public often equates lower treadwear to a stickier, better-performing tire. We see this in online discussions all the time, and tiremakers are perfectly happy to participate in this charade.

The Emperor Has No Clothes

Imagine a city with speed limit signs and no police. Good neighbors will play nicely, but bad actors can have a field day. This is what has happened over time with UTQG treadwear ratings.

Photography Credit: Andy Hollis

The UTQG system was a great idea when everyone participated fully, but the testing required is extensive and expensive–especially for smaller tiremakers and/or niche products. Further, NHTSA does no back-end compliance checking on Treadwear ratings for those same reasons–it’s expensive and logistically complex. Instead, it relies on manufacturers to do the right thing and either empirically test or use engineering data to properly project treadwear. But none of that is submitted to NHTSA for new tires, just the final ratings.

Large tiremakers, particularly those that are members of the industry’s trade organizations, cannot afford the negative publicity or liability to their entire line should irregularities come to light in any specific model. They have teams of lawyers in their risk management departments with large lists of requirements that their street tires must meet, well beyond what DOT or UTQG specifications dictate. In today’s worldwide economy, they also typically have to meet the more stringent requirements of other large markets, such as the EU.

Small, low-volume tiremakers can build whatever they want, stamp it 200tw and sell it in the U.S. There is no external oversight, either from peer review or NHTSA. They have nothing to lose and everything to gain–as in winning. Further, they typically don’t have the budget to empirically test or engineer a proper rating.

Small, motivated manufacturers can also pivot quickly. Running changes with new compounds or internal constructions can appear without notice, or possibly even show up only for single important events–say, for example, national championships.

We’ve been down this road before in the early R-comp days, and while it produces amazing technology and pace, it’s chaos to competitors who aren’t in the know. The rules might say that “special tires for special people” are not compliant, but how would you know? Same goes for running changes made outside of the rules season for eligibility.

The End Game?

Firstly, hats off to Vitour and Sammy Valafar for doing what any good racer would do: Read the rules and exploit any weak areas. Is the P1 really a 200tw tire? Hard to say without paying for UTQG testing. Some of the manufacturer insiders we spoke with suggested that the 200tw bar isn’t even all that high and that the tire might indeed meet it. In fact, one source told us that a Hoosier R7 would likely meet the 200 bar.

Photography Credit: Andy Hollis

With the fallacy of the 200tw requirements now exposed, where do we go from here with our rules? If the goal is to continue with tires that can be safely driven to and from events, how do we define a real street tire? Or do we just throw up our hands and let the wolves run the hen house?

“I’ll know it when I see it” doesn’t really work, as everyone sees things differently. Yet the key objective metric we’ve relied on is now known to be easily compromised.

Will history repeat itself, with us yet again competing on sticky, short-lived racing slicks bearing only a small amount of tread? Will a new subjective tire submission and approval process be mandated by sanctioning bodies? Is there value in adopting the more stringent European E mark and ratings system as an additional requirement? Stay tuned. This saga has only just begun.