Debunking The Tire Age Myth The Shop Manual
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00:00You might not know this, but tires have their birthday stamped right on the sidewall.
00:07Look for the oval symbol, and the four-digit code inside represents the week and year of
00:12manufacture. And the guideline I've always heard is that you should replace your street tires
00:17after five years, even if they still look good, because the rubber will have aged and hardened.
00:23But do tires really expire after 60 months, or is that just a myth the industry pushes
00:28to sell more products? Well, we talked to elastomer experts to learn how rubber actually
00:33ages. We've got a seven-year-old set of hyper sport tires and a senior citizen of a superbike
00:39to test them with, so we're about to get some definitive answers, or at least some
00:43more informed answers. Let's open up the Shop Manual.
00:47This episode of the Shop Manual is brought to you by Kershaw, my go-to unboxing knife and a tool I
00:59carry with me everywhere. Get 25% off your order at kershawknives.com with the code TSM25.
01:08The reason people are worried about old tires or new tires that are actually a couple of years old
01:14is that over time the rubber degrades and hardens. Theoretically, that means there's going
01:19to be less traction available to you as you tip into a corner or get on the brakes to avoid that
01:24car that just pulled out in front of you. But tires aren't like fruit that goes from good to
01:29moldy overnight, so there's no set age at which they become unsafe. They're only recommendations,
01:34and because those recommendations pertain to safety, it makes sense that they would be super
01:38conservative. And yet, when I tried to substantiate that five-year rule of thumb,
01:44I couldn't find any evidence for it outside of the riders forums and word of mouth.
01:49Avon is the closest with a seven-year recommendation, but other manufacturers like
01:54Bridgestone, Michelin, Continental, and Dunlop all say that 10 years is the allowable service
02:00life for a properly maintained set of tires. And I gotta say, a decade? That was a surprise.
02:06The skeptic in me feels like that is way too long to trust a set of tires,
02:10at least for the way that I like to ride. So to test the theory that tires can be good for up to
02:1610 years, we have sourced an unused set of Bridgestone RS10s from way back in 2014.
02:22We also have a fresh set from 2020 to compare them to, and we're going to head to the racetrack
02:27with Dave, our beater GSX-R1000, to see how the old tires perform. So with any luck,
02:33I won't be filming the rest of this video from a hospital bed.
02:36For this test, we signed up for a public track day at Buttonwillow Raceway,
02:41and to kick things off, we installed the fresh RS10s with date codes from May and November 2020.
02:48I then took a few sessions to get familiar with the tires handling and establish hot pressures,
02:52as well as give Dave a chance to snack on some Italian hors d'oeuvres.
02:56He slept in, so he hadn't had breakfast.
02:58The RS10s were great. I'd rate them an A in terms of handling and traction,
03:03and I was having a blast ripping around on them.
03:05These tires feel pretty freaking good, I got to say. Very predictable, loads of traction.
03:15Very successful. First session out, did get a couple of slides out of the rear, which means
03:21got up to the limit. So we got a good benchmark for what a new set can do.
03:26Good benchmark for what a new set of tires feels like. Now, we're going to lever on the
03:32seven-year-old set and see how those do. Considering how good the fresh rubber was,
03:38deciding to intentionally lever on an old set of tires was pretty difficult.
03:43I know, supposedly they're good, but honestly, I'm pretty nervous about it.
03:48Yet, it had to be done. So on went the front RS10 from Halloween 2014,
03:54and the rear from early November.
03:58Hesitantly, cautiously, I rolled out on track. I was being really careful.
04:04A warm-up lap with an extra dose of caution.
04:07But after squirming around for a few turns like any new cold tires would,
04:12the ancient RS10s came up to temp and felt just as grippy and agile as the fresh set.
04:17All right, trail braking deep, me on the ground, all the way through this corner, heck yeah!
04:24It's crazy. Before I started researching this topic,
04:27if you told me to go drag a knee on seven-year-old tires, I would have flat out refused.
04:32And yet, a few laps in, I was charging at apexes and once again having a blast.
04:38Wide open throttle!
04:44Well, I did not see that coming. Those old tires were every bit as good as the fresh ones,
04:49even though they were three-quarters of the way through their shelf life,
04:52which was already 25% longer than I thought tires were good for.
04:55Now, the reason our old tires were still good is because they had been stored properly,
05:00and that might be more important than how many months had passed since they were made.
05:04Age is not the same thing as aging.
05:09Think of milk. It'll last for a week or more if you keep it in the fridge.
05:16But if you leave it out on the counter overnight, well, you don't want to lose that bet.
05:21It's the same thing with tires. Stored indoors, away from direct sunlight and intense heat and
05:26a couple of other factors that we are going to discuss, tires have a very long shelf life.
05:31And if you buy your rubber from a reputable store or online retailer,
05:35they will have proper storage facilities and rotate stock to keep inventory fresh.
05:41But say you have two or even three bikes to ride and you rotate through them.
05:45In that case, tire age might become an issue.
05:48Or maybe you bought a set of tires, but you don't intend to use them right away.
05:52In both situations, there are some crucial factors that are going to affect how the tires age.
06:01Tires should be stored in a cool place, like a basement or a ventilated warehouse,
06:06as opposed to a sealed shed.
06:08Once tires are in service, the only thing you can really do to reduce heat exposure is
06:13park in the shade.
06:14Ambient temperature is what it is, and sad to say it, but in hotter climates like Florida and Arizona,
06:20tires will age faster than in cooler climates like New Hampshire and Washington.
06:29Oxygen causes the atoms in the elastomer molecules to lose electrons.
06:34This oxidation causes the rubber to harden and weaken.
06:37And when your tires are in service, they're pumped full of air, which is 21% oxygen.
06:43So essentially, they're pressurized with rubber poison.
06:46You can avoid this issue by inflating your tires with nitrogen,
06:50but that's going to be a tedious and pricey endeavor.
06:52Plus, the manufacturers have already mixed antioxidants into the rubber.
06:57Now, if you are very concerned with tires that you're storing,
07:00you can always wrap them in a black trash bag.
07:03The opaque plastic will also protect them from our next reactant, light.
07:07Ultraviolet radiation causes homolytic fission,
07:11the fancy name for when molecules break down into smaller, less stable pieces.
07:16The manufacturers mix UV stabilizers into the rubber, but it gets used up,
07:20so it's very important to store tires away from sunlight.
07:24Once tires are on your bike, it is going to be better for them
07:27if you park in the shade versus in the sun.
07:29And as with hotter climates, sunnier climates will cause more rapid tire aging.
07:34Sunnier climates will cause more rapid tire aging,
07:37not just because of increased UV exposure,
07:40but because sun catalyzes the formation of ozone.
07:47Ozone is a more reactive form of oxygen that wreaks havoc on rubber
07:51and is the leading cause of dry rot.
07:53Ozone is created when vehicle exhaust, gasoline vapor,
07:56and other chemicals react with ultraviolet radiation and heat.
08:00Ozone is also created when air is exposed to electricity.
08:05So heavy electrical equipment like transformers,
08:07as well as appliances like refrigerators, compressors,
08:10dehumidifiers, and anything with an electric motor are going to kick off ozone as well.
08:15So if you've got any of those devices where you park your bike,
08:18they're probably not doing your tires any favor.
08:22Now, I'm not going to inconvenience myself by taking the beer fridge and air pig out of my garage,
08:27but if you're the type of psycho that wants to give your bike a museum-grade place to sleep,
08:31eh, it's something to consider.
08:36This is just tire flex, which is unavoidable when you ride your motorcycle,
08:40but it is directly influenced by pressure, load, and speed.
08:45And we're not just talking about tread wear here,
08:47we're talking about carcass flex that fatigues the rubber
08:50and pretty much causes all of the reactions we talked about earlier to be accelerated.
08:55When tires are in storage, they don't experience much mechanical stress,
08:58but if they're stacked up in a pile, then those tires at the bottom are getting squeezed.
09:03So your best bet for storing tires is to line them up horizontally.
09:09But honestly, nothing you can do is as important for tire health
09:13as just checking your f***ing tire pressures.
09:16Have you aired up in the last two weeks?
09:17No?
09:18Well, then you've probably got low pressure,
09:20and that's going to be worse for tread wear, rubber aging,
09:22and handling than anything your tires are going to experience
09:25outside of blatant abuse like a burnout or parking under the arc of a Tesla coil.
09:31Even still, people want fresh product.
09:34I get it.
09:35So if you're going into a store,
09:37you can always just filter through the tires and buy the most recent date code.
09:41Or if you're purchasing online, you can sort by best sellers
09:44and buy something from the top of the list,
09:46since those models are going to have the highest turnover.
09:49Alternatively, you can just buy the latest and greatest
09:51because the newest tire from a given manufacturer,
09:54it's going to be, well, it's going to be new.
09:56If you end up getting suspect tires or rubber of unknown origin,
10:00it's important to check the date code,
10:01but also visually inspect for tread wear, damage, and dry rot.
10:06Plus, consider the tire's intended use.
10:09Are you just going to commute on it,
10:10or do you like to charge hard at the racetrack?
10:13The more demanding the application,
10:15the more cautious I would be with tire age.
10:18But the bottom line is that tires don't just expire after five years.
10:22So if the tire you're working with is less than 10 years old,
10:25isn't obviously worn out or damaged,
10:27and has been stored properly,
10:29odds are it's going to be just fine to ride on.
10:31That's according to me, Dave here,
10:34and most importantly, the people that make the tires.
10:47you