Piston Slap: Safe Thinking on Dry-Rotted Tires?
Jimmy writes:
Sajeev,
For years I traded in my Hondas and Toyotas within 18 months of purchase. However, I did not care for the newest Highlander, Pilot, and Camry, so I kept the old ones hoping the next versions would be more acceptable. While I have not had a single problem with these vehicles, with the exceptions of a few light bulbs, I’ve noticed Michelin Green X and the Continental ContiProContact have small cracks in the tread grooves. The tires have 40,000 and 55,000 miles on them with lots of tread left. I have asked tire stores and some say don’t worry while others say they are dangerous.
What is the rule for tire replacements when it comes to cracks in the tread grooves?
Sajeev answers:
A timely query: my once-new 2011 Ford Ranger is old enough for new rubber. I noticed those cracks, even with decent tread and “good” rubber between them and the wear bars. And, just like you, I certainly ain’t trading it in for a new Ranger anytime soon!
This indicates dry rotted tires, which means harder, slippery and unsafe rubber in wet/aggressive driving conditions. As the cracks grow, blow outs and tread separation failures are likely. Given the mileage, I assume your tires are also five-ish years old. Tire manufacturers have a hard stop on replacement after 10 years, while car makers (fearing Firestone-esque lawsuits?) recommend six-year replacement intervals. For a daily driven and/or primary vehicle, I’d lean closer to the six-year interval for safety concerns.
Depending on the climate (heat is the concern) and UV exposure (garaged?), I reckon we both need new tires soon. The top picture is the factory ContiTrac on my rig. The dry rot is closer to hairline cracks, not replicas of Grand Canyons. Given their admirable performance during Houston’s recent floods, these tires have several more months of life, but I’m rollin’ on borrowed time.
But looking at them up close?
Those are bigger than I remember from my last “wait for the oil to drain out” tire inspection. While I don’t see myself on a looong highway trip in the future, this is a cause for concern.
So will Sanjeev treat himself to 10 mm wider rubber so contact patch isn’t stretched so tightly and the speedo might read accurately? The autoblogosphere is dying to know!
[Images: © 2016 Sajeev Mehta/The Truth About Cars]
Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.
Also, if your tires suck and you’re shopping for new tires, help support TTAC’s work by doing your research at TireReviewsandMore.com. — TTAC staff.
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Those surface cracks wouldn't bother me. I've seen far worse. But I have a relatively high tolerance for risk. New tires certainly would be safer, allowing a much greater safety factor in an adverse situation such as an under-inflated tire at high speed. They'll also likely have considerably more grip. Structural problems - deformation or sidewall bubbles - are more of a concern to me. Tires with those issues should be replaced immediately. Slow right down and check things out if anything feels unusual. Any tire that's worthy of driving at highway speed should have no vibrations. The older a tire is, the more frequently and thoroughly it should be inspected.
I have noticed that Michelin tires seem to be more prone to cracking that other brands. The MXV4s that I put on my station car had cracking between the treads after 7 years of being outside. Still had tread life but they failed inspection. Funny, my Michelin bicycle tires did the same thing...