AAA:Replace worn tires at 4/32nds inch tread depth

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AAA 4/32 Tire Replacement RLANDO, Fla.— Citing safety concerns related primarily to wet braking, AAA Inc. is recommending consumers replace their worn tires at 4/32nds inch tread depth. Nationwide car owners' club AAA is basing its stance on the results of tests it conducted recently on new and worn tires, which showed significant increases in braking distances in wet conditions as tires wear. "Tires are what keep a car connected to the road," John Nielsen, AAA's managing director of automotive engineering and repair, said. "Even the most advanced safety systems rely on a tire's basic ability to maintain traction, and AAA's testing shows that wear has a significant impact on how quickly a vehicle can come to a stop in wet conditions to avoid a crash." AAA conducted its testing in partnership with the Automobile Club of Southern California's Automotive Research Center. Those tests compared the wet braking performance of new all-season tires and those worn to a tread depth of 4/32nds inch. According to the tests, tires worn to a tread depth of 4/32nds inch exhibit the following, compared with a new tire: • An average increased stopping distance at highway speeds of 87 feet for a passenger car and 86 feet for a light truck; and • A 33-percent reduction in handling ability, for a passenger car and 28 percent for the light truck on average. AAA's testing involved a Toyota Camry and Ford F-150. Tires tested on the Camry were: Nexen Classe Premiere CP671; Goodyear Eagle Sport; Fuzion Touring; Pirelli Cinturato All-Season Plus; Kumho Ecsta 4X II; and Michelin Premier A/S. Tires tested on the Ford F-150 were: Firestone Destination LE II; Bridgestone Dueler H/L Alenza Plus (113T); Cooper Evolution H/T (115T); Michelin Defender LTX M/S (115T); Hankook Dyanpro RH12 (113T); and Goodyear Wrangler Fortitude HT (115T). The complete results are available on AAA's website. "AAA's testing demonstrates the impact that tire tread has on safety," Megan McKernan, manager of the Automobile Club of Southern California's Automotive Research Center, said. "If tested side-by-side at 60 mph, vehicles with worn tires would still be traveling at an alarming 40 mph when reaching the same distance it takes for vehicles with new tires to make a complete stop." AAA said its research found that tire performance does vary by brand, but price is not necessarily an indicator of quality. Worn tire performance deteriorated significantly for all tires tested, including those at a higher price point. AAA advises shoppers to research options carefully before selecting a replacement tire for their vehicle, and never choose one based on price alone. "With newer cars going longer intervals between routine maintenance at automotive service facilities, drivers may not become alerted to the fact their tires are too worn until it's too late," Mr. Nielsen said. AAA's comprehensive evaluation of tire tread laws and regulations across U.S. states found state requirements range from inadequate to non-existent. Forty-two states consider 2/32nds inch the minimum legal tread depth. California and Idaho have set the minimum at 1/32nd, while Arkansas, Montana, New Mexico, North Dakota, South Carolina and West Virginia have no legal mininum standards. The AAA's recommendation is in contrast with Michelin North America Inc.'s contention that removing tires prematurely from service costs consumers billions of dollars and increases the amount of scrap tires to be dealt with.
 
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When I get to 4/32's I start thinking about replacing. Nothing new here, I thought AAA (and others?) had been pressing for this for years? Between 2/32's and 4/32's I adjust my driving, knowing that traction might be lowered in rain. Before anyone yells at me that I should remove "unsafe" tires--a similar argument could be said to buy the car with the shortest stopping distance, and anything longer than that is putting everyone at risk. And that driving a twenty year old car is automatically unsafe simply because it's been surpassed.
 
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I think at 4/32" one should be making their plan to get the tires replaced in the near term. And of course if a Subaru symmetric AWD then all 4 tires need replacement.
 

Astro14

Staff member
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I replace them at 4/32 most of the time, as that's the depth at which wet performance begins to significantly degrade. Legal minimum and safe aren't the same thing, most of the time...
 

CT8

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Originally Posted By: tig1
Where I come from we call it 1/8.
4/32 sounds more high tech.
 
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Sad thing is that the tread wear bars alter (not by much, but they do) the wet weather performance of tyres. But by defining the legal minimum, they at least give something to quantify compliance to an arbitrary definition of safety...a "go-nogo" principal that can be applied at the side of the road. (used to be "match heads" down here..if a match head could be hidden in the tread over 75% of the tread area, they were legal). at 275 thousandths, the Deuller H/Ts on my Colorado failed my wet weather standards...and I replaced them
 
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This is why I always say that half tread is actually 6/32nds. If most passenger tires(generally) start out at 10/32nds, and are only good(by law) down to 2/32nds, then 6/32nd is our(OUR) real 1/2 tread mark. Not according to the tire industry or safety organizations but, to me. Think about it! Others have disagreed & will continue to disagree with me. I too start thinking about buying new tires somewhere between 5-6/32nds and depending on the season, I'll get rid of them by 3-4/32nds.
 
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Quote:
Where I come from we call it 1/8.
If one looks a standard tire tread depth gauge, the gradations are by 32nds. So 4/32nds basically saying the quarter test now more appropriate than the penny test. Corresponds to display sign information now found in DT stores. https://www.discounttire.com/learn/tire-safety
 
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So if I want to maximise my bald tyre wet weather performance, I should drive a light truck, rather than a car. Good news in the US, I'd have thought.
 
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I go by the wear bars. 2/32nds. Been that way for years. With the price of quality tires today, I'll continue at 2/32.
 
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I do the same.
Originally Posted By: Astro14
I replace them at 4/32 most of the time, as that's the depth at which wet performance begins to significantly degrade. Legal minimum and safe aren't the same thing, most of the time...
 
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With AAA's concern over tread depth, I'm surprised they didn't also mention age and/or UV cracking. Most people can see a tire wearing. Most don't really key on cracking or age until the tire is really worn. Recommendations on retiring a tire based on age are all over the map too. Then you have the issue of good tread, no cracking, yet the tire is 6-10 yrs old...or older. What then?
 
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I start thinking about it when they hit 5/32's and start to get rid of them at either 3 or 4/32's. If they're less than 5/32's for the winter, I get rid of them then. 5/32's is about as low as you can go for good snow performance, 4/32's is for rain.
 
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This means more business for the tire industry, but I can see the safety aspect as well. In snow and rain country, 4/32" is a good time to replace.
 
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Originally Posted By: ctrcbob
I go by the wear bars. 2/32nds. Been that way for years. With the price of quality tires today, I'll continue at 2/32.
Exactly, typically my sidewalls blow well before that anyway
 
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Nobody keeps pennies in their pockets anymore so this is the standard. I agree with Tig. 1/8 should be used. I was taught to reduce fractions when possible.
 
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Originally Posted By: Rmay635703
Originally Posted By: ctrcbob
....
....typically my sidewalls blow well before that anyway
Really??? That shouldn't be the case unless they are run underinflated.
 
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