By on July 24, 2007

pennyfront.jpgTens of millions of American motorists know the routine: to check if your tires are worn out, insert a penny in between two treads. If you can't see the top of Honest Abe's pate, it's time for new shoes. The Tire Rack says it's time to upgrade the coinage involved from a penny to a quarter, from Abraham Lincoln's head to George Washington's noggin. According to the South Bend, Indiana tire vendors, the switch raises the old test's 2/32-inch (1.6mm) or less standard to 4/32-inch (3.2mm). To justify the switch, The Tire Rack tested a 2006 Ford F-150 Super Cab 4×2. Shod with Abe-compliant rubber, the truck averaged 499.5 feet to stop from 70 miles per hour on wet pavement. The same vehicle riding on quarter-compliant tires stopped almost 122 feet (24%) shorter. We'd like to see more tests conducted using a range of rubber and vehicles in a variety of conditions performed by an organization that doesn't sell tires. Still, point taken. Is it time for tire testers to replace the penny with a quarter?

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20 Comments on “Tire Tread Debate: Penny or Quarter?...”


  • avatar

    Fifth Gear did a segment on this a few years back and came to virtually the same conclusion. Tires that were still “legal” but close to the limit were awful at braking on wet roads.

  • avatar
    TexasAg03

    If you can’t see the top of Honest Abe’s pate, it’s time for new shoes.

    Wouldn’t it be “If you can see the top…”?

    Anyway, I think it’s a good idea, although I have always replaced tires before the 2/32 depth was reached.

  • avatar
    miked

    For folks that don’t drive lots (or like me drive lots of different cars), the tires can get old before the tread gets too small. Often, people don’t realize that over the rubber gets harder as the tires age and you lose tons of performance. Generally, I get new tires every 4 years or so, but I notice most of the performance is gone after 2 years. I’ve never been even close to the 2/32 legal limit when I’ve replaced tires.

  • avatar
    tulsa_97sr5

    Miked – you are so right. One scary time on a slightly wet road with a set of Michellins that had plenty of tread but were a little dried out taught me my lesson. I always wonder when I hear or read someone brag about getting 60k or more miles out of a set of tires.

  • avatar
    turbosaab

    Here in the well-regulated State of Maine 4/32″ is already required for State Inspection.

  • avatar
    Steve_K

    For those of us that work for a living, replacing tires falls in the Necessary Evil category of vehicle ownership. Piloting a 1977 RWD Omega in the Michigan winters with nearly smooth tires was like a pass/fail driving test for me (I passed). The best tires I’ve ever owned are BFG All-Terrian T/A’s. Excellent traction and tread life, currently just over 75,000 actual miles! I will be changing them this Fall since I already passed my winter driving test. :)

  • avatar
    Megan Benoit

    I read their write-up and I think their testing was pretty fair — they used ‘stock’ tires on a 325i and F-150, tested brand new against 4/32 and 2/32 (and aged the tires in the same way they do for any testing). The results speak for themselves — naturally, some tires will wear better than others, but few people change out of the stock tires and I think it was a pretty fair test. I think that no matter what trickery you do, full tread will be better than 4/32 which is better than 2/32, which is better than a chinese-built tire (ha, zing). Is it enough difference between the latter two for the ordinary bloke to decide it’s worth upgrading early? I suppose it depends on how much it rains where you live, and how much you enjoy hydroplaning.

  • avatar
    Ralph SS

    So. Do the “estimated” milage ratings of tires mean that you should get “X” amount of miles from new till you get to the point of being able to see a presidents head from between treads? From my experience it’s about half that.

  • avatar
    Mud

    I think that for all NAFTA regulated vehicles you are allowed to see the entire peso before the tire needs to be replaced.

  • avatar
    dolo54

    I drove on bald tires much longer than I should have because I enjoyed skidding around in the rain so much. When I got the new ones, I wasn’t nearly as happy when it rained.

  • avatar
    Robert Schwartz

    “the truck averaged 499.5 feet to stop from 70 miles per hour on wet pavement. The same vehicle riding on quarter-compliant tires stopped almost 122 feet (24%) shorter.”

    76% shorter.

  • avatar
    philbailey

    122×100/499.5= 24.4%

  • avatar
    miked

    From the Article: It is also very important to recognize how much tire sizing and vehicle applications have changed in the last 40 years. The 1967 Chevrolet Impala weighed 3,897 pounds and was originally equipped with 7.75-14 sized tires that featured about 4.5-inch wide treads. The 2007 Chevrolet Impala weighs 3,674 pounds and uses P225/60R16 97S sized tires that have 7.1-inch wide treads. In contrast, today’s Impala weighs 233 pounds less and uses tires that feature a tread width that is over one and a half times wider than tires used in 1967. While this undoubtedly provides more traction and shorter braking distances on dry roads throughout the tires’ life, how do the tread depths of today’s wider tires influence stopping performance on wet roads when the tires are new, as they wear, and ultimately as they reach the legal minimum tread depth?

    Contrary to popular belief (“..now your car weighs twice as much and your tires are half as wide and you’re burnin’ ’em up…”), the width of the tire has no impact on the friction between the road and the tire. It definitely helps with tire wear, but the friction is the same, so the panic stop will be the same length. In fact, the wider tread may hurt wet stopping conditions as the water has to be pushed out a farther distance.

  • avatar
    carlisimo

    122ft is 76% shorter than 499ft
    122ft is 24% as long as 499ft
    122ft is 409% better than 499ft

    OK dunno about the last one. But it’s a surprising statistic. And pretty relevant to me because I go through a set of tires a year.

  • avatar
    Dynamic88

    Is it just me that wants to call these figures 1/16th and 1/8th ?

  • avatar
    taxman100

    Just about to crack 70,000 miles on my tires on my Grand Marquis.

    Love the rear wheel drive – easy on tires.

  • avatar
    robert_h

    Please, people! It didn’t stop in 122 feet. It stopped in “122 feet shorter”. That means it stopped in 499-122 = 377 feet.

  • avatar
    jthorner

    I rarely take tires on our vehicles down to the minimum legal limit because I routinely notice that the wet and dry traction have deteriorated enough to justify new shoes. Tires are expensive, but car wrecks are even more expensive.

    A few years ago I had recently put new tires on our Volvo 850. Driving in the rain a kid in his ricer dashed across the road in front of me and I was full on into the ABS braking. I missed him by about two feet. Old hard worn tires would easily have consumed that extra two fee.

    Tirerack has this one right, even if it is to their advantage to say so.

  • avatar
    jthorner

    BTW, Bridgestone claims that many of their tire incorporate two different tread compounds in layers. The outer layer is a relatively longer wearing harder rubber while the inner layer is a softer layer with better friction characteristics. The idea is that by the time mileage and heat have done their thing the tires will be riding on that softer inner layer and loose less performance than they would if the tire used one compound for the entire tread area as most tires do. Tirerack’s published test didnt’ include any of these Bridgestone dual layer tires. It sure would be interesting to see that same test done with two tire models side by side, with and without the dual layer design.

  • avatar

    Yeah I am a cheap bastard but even I have learned my lesson on driving on bald tires

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