Connect with us

Editor's Notebook

A Challenge for You: Tread Depth Rule Interest Grows, But Dealers Can Lead the Charge


Talk about your groundswell of support! Since my column urging the industry to push for a national tread depth law – 4/32nds deep for cars and 5/32nds for Class 3 and larger trucks – I’ve heard from a couple of state associations, a number of dealers and TIA Executive Vice President Roy Littlefield, all of whom voiced support.

Click Here to Read More

As I mentioned in November, many tiremakers and private research groups have ample data that supports the premise that more is best. Dr. Burkhart Weis, the head of Continental AG’s tire development worldwide, was kind enough to share some data from the Motor Industry Research Association (MIRA).

MIRA’s tests compared wet pavement braking distances at various tread depths. Using a baseline tread depth of 8mm – approximately 10/32nds, the standard new passenger tire depth – MIRA’s 100-to-0 kph tests showed braking distances jump dramatically with each millimeter of wear.

At 6mm on wet pavement, for example, braking distance increases by 9%, or nine feet for every 100 feet of stopping distance. At 4mm, wet braking distance increased about 25%, and at 3mm, the distance jumped about 35%.


What happens at 1.6 mm – the equivalent of our 2/32nds rule (well, in some states) and the current legal minimum for much of Europe? It took nearly 70 additional feet to stop. Imagine what it would be like on slush or snow.

MIRA also measured “overall safety performance” (OSP), combining braking distance with handling, traction and durability. At 8mm, OSP is at 100%. As test drum reduces tread depth to 1.6mm, the OSP factor falls to less than 50%. When tire age is also factored in, OSP falls to 0% at 1.6mm.

Continental is fully behind the 3mm campaign being forwarded in many European nations and would like to see a 4mm minimum for winter driving, as well.


In a recent op-ed piece that raised more than a few eyebrows, Fairleigh Dickinson professor Peter Woolley claimed that Americans and American media are more concerned with the number of soldiers killed in Iraq – some 800 brave souls in 2006 – than the number of Americans killed in traffic accidents – reportedly 44,000 last year. Auto accidents, Woolley wrote, are the leading cause of death for children, teenage drivers and anyone between the ages of 3 and 33.

“Opinion leaders largely ignore the ubiquitous massacre,” Woolley wrote. “It is not brought up in the State of the Union address. It is rarely the subject of public affairs shows. Statistics aren’t updated daily in major newspapers or broadcasts.”


How many of those 44,000 deaths can be directly related to inadequate tread depth? It’s anyone’s guess, as reliable field data is so very insufficient. But even at 1%, that’s 440 lives that might have been saved.

Consider that the entire TREAD Act was predicated on some 270 deaths attributed to alleged tire failure. Consider that current TPMS regulations, according to NHTSA, will save 191 to 221 lives per year – when 100% of all passenger vehicles on the road have TPMS. Which will happen in about 20 years.

Consider that the National Academy of Sciences recently spent millions to tell us the most obvious thing: Lower rolling resistance tires save on gas. How much, you ask? Maybe $30 per year. What if we had taken those millions and put it toward a 4/32nds campaign? A life is worth more than $30, isn’t it?


Woolley only dealt with the unfortunate end. How many of the 6.16 million traffic accidents recorded in 2005 (the most recent report available, as your tax dollars apparently do not pay for speed) were tread depth related? Again, even if it’s just 1%, that’s 61,590 accidents.

Those 6.16 million accidents caused 2.49 million injuries. Applying our 1% rule, that’s 24,900 people who may have been hurt due to insufficient tread depth.

I’m not going to recount the obvious sales benefits a 4/32nds minimum would mean for your business and tire companies or how fewer accidents means lower insurance rates.


But here is what I will tell you:

• Get on the phone and/or e-mail your state reps and educate them. Then, do the same with your Congressperson and Senator. State laws are fine (if they are enforced), but a national regulation is better. Tell them they have the rare opportunity to be a hero, and they can have an undeniable impact on their constituents. There are plenty of statistics available that you can share with them.

• Talk to each and every one of your customers. Urge them to get involved and contact their state and federal lawmakers. And, more importantly, educate them to be safer and switch their tires out when they have only 4/32nds left. Even without laws, you can still have a positive impact.


I challenge you take an active role in this drive. You can start saving lives – 4/32nds at a time.

Click to comment


Tire Review Magazine