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Tires: Dot Codes, Used Tires, Dry Rot, Plugs, & Patches

Just because you buy “new” tires doesn’t mean they were actually made recently. It can take awhile for tires to reach tire retailers after being shipped from the manufacturer. Checking your tires’ DOT Date Code will tell you when they were made and how long they may have been stored. It is important to know that tires are often stored for months or years at a time, so your tire’s DOT code might not be in the same year you bought the tires, and that’s not a concern.

How Old Is Too Old?   

This is a topic rife with misinformation. It all began with a sensationalist story on 60 minutes more than a dozen years ago. The Department of Transportation requires a manufacturing date be stamped onto the sidewall of passenger tires. It is a four digit number – the first two digits are the number of the week within the given year and the last two numbers are the last two digits of that particular year of manufacture. Suddenly, 60 minutes determined that tires had an ‘expiration date’ that could be measured from this DOT stamping. That is patently false information. Tires are a complex product as-discussed further down, and while various types of rubber compounds based both on quality but also desired driving characteristics of the particular tire model play a notable role in the ‘lifespan’ of a tire – use and/or storage are much more important. We’ve seen tires exhibit signs of no longer being usable due to cracking in the sidewall – in less than a year from their manufacture. This is undoubtedly due to the quality of the materials, but this goes against common sense and expectation. More importantly, we’ve also seen quality tires, stored in an appropriate manner – that were still usable 20 years after manufacture. The key features that we look for in determining if a tire is usable or-not, are tread depth, unsafe marks in the sidewalls, quality of wear, and cracking in the sidewalls. Legally, you must replace your tires when the tread depth falls below 1.6 mm.

We have been selling tires for over 20 years including plenty of used tires to very satisfied customers.  It is common knowledge with all our valued customers: with reference to tires as New, the reference is to the tread, and mileage; not referring to the DOT code which is the date of manufacture and does not affect the performance or safety of the tires. 

Cracking on tires is only an issue when it occurs in the sidewall of the tire. The reason that the cracking would be an issue in the sidewall is due to less material in both rubber as well as the carcass – as-compared with the tread.

As for why some tires crack and some don’t – tires are a very interesting product in-terms of the variables that go into them – many of which are at-odds with each other: Wet traction versus dry traction. Grip versus longer use/miles/life. Ability in snow. And especially price.  So many factors at-odds with each other. Tire dry rot is also known as sidewall cracking and can affect the performance and safety of a tire. 

If you see a small mark in either the tread or the sidewall of your tire, it is likely cosmetic and most likely caused by a rock or other debris from regular road use.  This should not be a concern. A deep mark in the sidewall where you see the metal belts, is a concern and the tire should be replaced.

It is safe to repair a tire if there is more than one puncture and the punctures are at least 16 inches apart. If the tire has big cuts or separation in the tread it should be replaced. 

There are two ways to repair a tire. A patch is larger than the puncture and will be pushed by air pressure against the puncture outward. The tire is removed from the rim, the patch is applied to the inside to seal it.  

A plug is wedged into the puncture and is pushed outward by air pressure and inward by the road. A plug should be used on the tread of the tire and never on nor near the sidewall.  A plug is perfectly acceptable for 99% of passenger vehicles. It is only vehicles that are driven regularly at speeds in excess of 110 miles per hour, that should require a modest puncture to be patched instead of plugged. Tire manufacturers, tire stores, and dealer service advisors are all quick to say that you shouldn’t plug a tire – and some warn against any type of tire repair. This is all in their own interest in selling you a more expensive service – or even a whole new tire.

We find that when our valued customers such as yourself take the tires that they purchase from us online at our great values to their tire shops or dealers for installation, many times these service personnel provide misinformation about the tires their customers have not purchased directly from them at their higher prices. The solution that we recommend is to go to another tire shop. 

The reality is that everyone drives around on used tires. The moment that someone buys a set of new tires and pulls out of the service bay, their tires are then used. There’s nothing wrong with purchasing safe and inspected used tires.

Changing your tire size can be confusing at the best of times, especially if you’re on the lookout for a new car or looking to change your tire size on your existing vehicle.