By on March 11, 2014

TTAC Commentator sastexan writes:

With the extreme cold throughout the US and seeing a few shredded tires on the highway this week (in fact, I had a flat myself – not sure what caused it but possibly doing donuts in the FR-S on a parking lot last week with lots of broken up ice on the edges), I got to thinking about spare tires.

Many of the Best and Brightest have “keeper” cars – myself included with our old Camry. Tires have limited lifespans due to dry rot, and I’m guessing spare tires are included in that category. The spare in the Camry is the original 14 year old tire (full size spare at least). How often do people change their spares, if ever? Has anyone with an aged spare had it blow out due to dry rot? Can you just order a new space saver spare off of tire rack?

Take care,


Sajeev answers:

Very interesting question, one that raises even more questions! Keep these in mind before we proceed:

  • Tires dry rot slower when living in an enclosed space with no exposure to sunlight (UV rays).
  • You may not see visible cracks like other rotted tires, but rest assured at some point the rubber has petrified like a rock.
  • The odds of getting stranded by a rotted temporary spare is less likely than an ordinary tire, as nobody wants to roll around on that tiny donut for an extended period.
  • Low air pressure can be the reason for a spare blow out, as they tend to leak profusely after a few years of hibernating in a trunk.
  • The items listed above will not necessarily apply to externally mounted spares in trucks/SUVs/CUVs. Treat those more like your other four wheels.

Externally mounted full size spare owners: change the tire every 5-10 years…more or less, depending on your risk tolerance and driving needs.  Or re-use one of your “old” tires as a spare when upgrading to new ones for your regular wheels. And if you are luckily to have a matching 5th wheel as a spare (or unlucky enough to have 5 steel wheels on your ride) just rotate it into the mix.

Externally mounted temporary spare owners?  Good question, as this is a future quandary of my little Ranger pick-em-up truck.  Then again, it might be similar to our next case…

Internally mounted spare owners?  Who knows the safe lifespan, but I’d wager that 10+ years is fine, since I’ve used the original spare in my Mark VIII for short distances in urban conditions. I’d change my tune if I was traveling hundreds of miles daily on rural roads…grabbing spare tires from crusher-bound Taurii and Fusions in the process.

Whenever you “internally mounted spare” folks are ready for new rubber, well yes, Tire Rack sells spares…but I’ll assume China’s finest off-brand donuts trade for less money from another vendor, as that happened when my 1983 Ford Sierra needed new tires in it’s unobtanium space saver-esque size for a measly $34 a pop.  Which is more than adequate for the job.

In the case of your Camry?  I say replace it (full size spare in the trunk) with one of the external tires when its time for new shoes. Or get a used tire from any local shop for $20-ish.  Or just make sure it’s inflated to spec and you drive SLOW (i.e. 50mph or less) for a short period of time. There’s no wrong answer here, unless you’re stranded in the middle of no where and must rely on a fresh tire to take you hundreds of miles away in a harsh climate.

As with everything in life, this Piston Slap boils down to: It depends.

So eyeball the rubber and keep it inflated to spec.  That’s a good start. Off to you, Best and Brightest.

Send your queries to [email protected]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. 

[Image: Shutterstock user Wachira W.]

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41 Comments on “Piston Slap: “Spare” Me from Dry Rot!...”

  • avatar

    How does 4wd/awd affect you if you want to rotate a spare into the mix? I know you can do some real damage to certain awd cars’ differentials by running tires with differing diameters.

    • 0 avatar

      If AWD then the tires need to be very close in tire height to each other. Each car has a different tolerance, check forums for the particular model. Often getting a flat means you have to replace all 4 tires unless you can find a place that will shave the tread for you. I have a full size spare with matching wheel so I include it in tire rotations that I get every 5k miles to keep height roughly the same. A true 4wd part time system doesn’t have the same liabilities unless it has a locking or limited slip differential, in that case the axle with the locker will need same height or you will burn out clutches. I imagine brake based traction control systems would go crazy if one tire spun at a different speed than the others.

    • 0 avatar

      Check your owners manual. I know Subaru is particularly stringent in this regard.

    • 0 avatar

      This gets over-exaggerated. Subaru says a 1/4″ difference in diameter is safe. So an 1/8″ in tread, or 4/32″.

  • avatar

    More importantly, keep that spare properly inflated. I just checked the spare in my car the other day and it was at 20 psi.

    • 0 avatar

      +1 I always check the spare when checking tire pressures (I’m not quite as diligent as I should be – about every 2 months). It is easy to forget about, and in some vehicles (like SUVs and vans) the tire is not very accessible and hard to reach.

      • 0 avatar
        Johnny Bouncewell

        I was out doing some geology with a professor of mine and we shredded the sidewall of one of our tires. We were way off the grid and these things happen. No big deal, that was until we found the spare was flatter than a 10 day old balloon.

        Once we walked back to cell coverage, the prof gave the university motorpool guys a verbal thrashing that would make a sailor cringe. Left a helluva impression on me, every assignment was turned in on time after that.

      • 0 avatar

        I’ll second that.

        My first ever experience of having to change a flat tyre was coupled with my first ever experience of a tyre blowout.

        I was on a highway and suddenly “thunk! thunk! thunk!”. I pulled to the side, took one look, rolled out the spare and got it changed nice and quick. I remember feeling really chuffed at how smoothly and professionally I did it. I got back in, started off and drove about… a kilometre or two and poof! tyre disintegrated.

        Had to call my Dad to come rescue me with another spare and he showed up and “I know what you didn’t do. You never ever checked the pressure of your spare, right?” and he was right.

        Well, I started checking after that (and told plenty of other people, though I doubt most of them listened to me… I shan’t resist saying “I told you so!” if they ever get stranded, though!)

    • 0 avatar

      The fill sized spare in my wife’s 1st Gen Lexus IS doesn’t fit in the spare wheel well full inflated. There’s insulation and whatnot making it a really tight fit, I couldn’t get it out the first time I needed to. They’re OEM wheels and correctly sized tyres, we’re the second owners but the first was dealer staff so I’m assuming this is how they all are.
      I put a compressor in there and have the tyre a bit soft to make it easier to get in and out. I have a note stuck on in case she has a recovery guy doing the job for her, I was worried that a recovery guy would assume a soft tyre in the boot had failed.

  • avatar

    I check the donut once every 6 months. Any vehicle I had with a real spare, I checked once a month. The Camaro had an inflater {no spare}

    I was always told, not to rotate side, to side, only front to back. The spare, was just that. a spare. Though you do need to monitor,cracks air preasure etc.

    • 0 avatar

      The Camaro likely has unidirectional tires – look for an arrow on the sidewall – thus if you swapped sides, the treads would be going in the wrong direction.

    • 0 avatar

      Unless there is a situation that prevents you from rotating side to side (such as a directional tire) you can.

      After tire manufacturers solved the issue with steel belts in radial tires fluttering and causing excessive heat (ever wonder why back then when you religiously rotated a set of tires, did the same with air pressure and alignment only to have the edges of the tire wear faster than the main tread area) they were able to decouple the tread blocks for enhanced wet and all season performance. The downside to this is the tendency for the tread blocks to start pushing up at the nose of the block and the best way to combat this wear is to cross rotate the tires if possible.

      The caveat to tire rotations is if your preferred rotation method maintains adequate wear characteristics be it front to back or the proper method depending on the drive wheels or cross rotated (fwd – cross the rears to the front and drop the fronts straight back, rwd – cross the fronts to the rears and pull the rears straight to the front, AWD – depends on how the system works, mostly seem to follow the RWD pattern although I’ve seen some that are just front to back or cross rotated) continue on as usual.

      You can also swap tires across the axle if they are staggered but employ a non-directional but symmetric or asymmetric tread design. Some tire manufacturer even offer a mileage warranty at reduced mileage in this situation where staggered fitments prevent rotations front to back.

  • avatar

    >>FR-S on a parking lot last week

    Why? The stupidest automotive activity EVER

    • 0 avatar

      Seriously, why screw up the FR-S. Tray drift the Camry.

      • 0 avatar

        I’m surprised no ones noticed the irony, an FRS owner who also owns a Camry. One the Shirley Templeton of car buffs, the other the unappreciated dunce.

        • 0 avatar

          Actually, the Camry is my wife’s old car, purchased before I was around. Had I been in the picture at that time, I probably would have talked her into something different. However, I have grown to respect the engineering that went into the Camry by a lot over my time with it.

          We kept the car because it is a sunk cost and she always has liked driving it – and it still proves itself quite useful. Camry ownership had zero impact on my decision to get the FR-S (mostly b/c the Toyobaru is much more Subaru influenced than Toyota).

  • avatar

    I have not had a flat tire since I bought a new vehicle in 1997, and I don’t recall the last time before that. I do not believe its worth thought.

    My wife had a flat on a 2002 model year Isuzu Rodeo, and just called the local Goodyear from the parking lot, they came and replaced it. Note that all 5 tires were >10 years old at this point. So don’t just put a 10 year old spare into use, and expect it to be fine, patch or plug the newer tire, and remount it, or buy a new pair/set of tires.

    I suspect modern cars come with good rubber, and replacing them at about 80,000 miles as a set of five is your best idea.

  • avatar

    Ahhh… good ol’ dry rot, one of the best tools for selling a brand new set of tires in a tire retailer’s tool box when a buyer really doesn’t need them.

    Michelin at least likes to call it ozone or weather checking.

    Its interesting to note that a lot of the “dry rot” people see is very superficial and is more the result of some chemicals (paraffin wax IIRC) migrating to the surface of the tire and causing the surface to minutely crack and no danger at all.

    Unfortunately tire dealers, mechanics and so on fail to make this distinction out of ignorance, personal bias or greed.

    • 0 avatar

      You’re spot on with your last point. Around here, most shops will happily fail a car on a mandatory safety inspection for some minor cracking of the rubber, holding your registration privileges hostage until you pony up for 4 new shoes. No wonder the repair associations lobby mandatory inspections so hard.

      • 0 avatar

        Yes its a shame. When I used to be in the tire business I was fortunate enough to work for a company that paid an hourly wage and not commission so the impetus was on selling the correct tire and not the one that made the most on commission. It also allowed you to be more honest about the condition of the tire and not having to rely on the general publics ignorance when it came to the condition of the tire.

        We used to get a call every now and again from a mechanic shop or car dealer bitching us out for making a “bullshit” recommendation.

        Another tool in the tire selling arsenal is tread depth, I’ve seen people come in with 3 or 4/32nds left on the tire after having been told the tires are pretty much shot.

        Tread depth certainly has an effect on performance in inclement weather but generally 2/32nds for wet weather is where you draw the line and is the reason why tire manufacturers mold the wear bar in at a height of 2/32nds.

        So much disinformation out there and I’ve noticed a tendency for people to establish an hierarchy when it comes to lending credence with advice or a recommendation.

        General mechanics seem to top the list and as you progress down the chain (mechanic – alignment guy — tire dealer) people tend to trust you less as you sit further down on the chain. In one particular instance we had a local alignment shop only recommend running the max inflation pressure in a tire for best wear. They were well established and we lost a few customers over them since they “knew” more about tires than we (the tire dealer) did.

        Nevermind vehicle manufacturers stagger air pressure in some instances to tune the handling on a vehicle and the alignment shops full pressure recommendation ignored that and in particularly bad cases we had people complaining about “rough” riding tires or tires that didn’t seem to handle properly wanting to return them.

        • 0 avatar

          4/32″ is pretty much shot if you’re driving in wet weather. In Tire Rack testing of braking from 70 mph on a road with standing water, the vehicles with 4/32″ were still going at least 45 mph at the point where they had come to a stop with new tires.

          It doesn’t make sense to be so cheap with something that is such an important component of safety and performance, and is also relatively inexpensive, considering the total cost of operating a vehicle. The lower the tread depth, the less value that remaining depth has. 4/32″ is rapidly approaching the point of absolute worthlessness to me.

      • 0 avatar

        Holding the vehicle to ransom was a problem in the UK a few years ago. The rules changed to place some liability on garages if there was an accident after the car had been in there and the side effect was to make it a bit easier for tyre fitters or brake/suspension places to put a prohibition order on the car if you didn’t have work carried out there. They couldn’t stop you leaving but they could report you to the police for driving a car with a prohibition order.
        I called a towing company once to get a car out of a rip-off fast fit centre who wouldn’t let me leave without agreeing to brake work that I would rather have done myself.

    • 0 avatar

      Unfortunately? For once they do their job and you call it unfortunate? That’s very unfortunate.

      • 0 avatar

        “Calling a perfectly safe tire dangerous due to cracking” is not “doing their job”.

        At best it’s ignorance – and at worst it’s a straight ripoff.

    • 0 avatar

      Michelins, as excellent as they are, tend to ozone crack more than other brands. Even on their bike tires.

      • 0 avatar

        My bike tires never lasted long enough to have cracks. Honda VFR750F, 122,000 miles in 17 years. I could not take it with me when I left the US, but I still miss it.

  • avatar

    This article leads me to ask, since UV light and Ozone attack tires, would there be a way to extend the life of tires stored in a trunk or a garage? Is there a spray that could be placed on a tire to keep ozone and or UV light away and yet not damage the tire.

  • avatar

    Wrap them up in a bag and store them in a cool dry place is the best recommendation. I’ve seen tires last well over a decade stored in such a state and even in slightly less favorable conditions.

    79 Lincoln Continental comes to mind, guy purchased one set of new tires in the early 80’s and again in the 90’s with about 12 years on them. The guy loved that car and kept it mostly in the garage and was immaculate as were the tires. He was an older gentleman so I suspect that second set of tires probably out-lasted him along with his 79 conti.

  • avatar
    old fart

    30 years is way too long as I found out :). Tire had no dry rot and held air but didn’t make 2 miles (of course it was an old Firestone 721 so that explains a lot )

  • avatar

    When I was in high school, my sister and I shared our dad’s 1983 BMW 320iS, and this was the car in which I did my first track event, a BMW CCA weekend at Road Atlanta in 1993 that was my high school graduation present to myself. I was not really aware yet how important good tires were on the track, and since I was not responsible for the maintenance on the car I was not fully aware of the state of the tires. The left front had a plug in it and started leaking heavily after the first day. Sunday morning I rotated a good tire to the LF and put the spare on the RR. The spare was the original spare from 1983. About ten minutes into my first session, the tread separated in the Esses, which was, to say the least, exciting. Lessons learned: top-condition tires really matter if you’re running your street tires, and never rely on a ten-year-old spare! For the OP, I might trust the tire for lower speeds or shorter distances, but I wouldn’t rely on it as a replacement.

  • avatar

    This is an interesting topic. I bought a car three years ago that had four 20 year old Michelin X tires (Costco receipt in glove box). The car had been driven maybe 20K since the tires were new and sat outside the whole time (in Northern CA, sun and hot). All the tires held air and had plenty of tread but two clearly had cracks where the sidewall met the tread and were replaced. The other two, which definitely had spidery cracks in the sidewalls were left on. 10K later no problems. I certainly dont drive this car hard but it does make me wonder about how long rarely used tires last. Maybe I’m just living on borrowed time.

  • avatar

    I kept the donut for the Taurus for 17 years; but in between it’s age and the fact the wires were showing in spots; I was praying it would hold up the 25 miles I drove it the last time I used it.

    I was not aware that Tire Rack sold donuts; back then, I could not find them on line, and your choices were either the dealer or a junkyard. But while having the original tire replaced under warrenty at Discount Tire, they told me they are carrying the donut tires now; they are carrying the most popular sizes first, and expanding selection with time. They had a size that fit the temporary rim in the Taurus; I think it was around $35-$40. Haven’t needed it yet; but am glad to have it back there just in case.

  • avatar

    I’ve got a 26 year old factory doughnut spare in the trunk of my 88 Thunderbird. It’s never been used and is just mounted in the trunk where it’s been since it left the factory. I fill it up once in awhile but it holds air fine and looks new. It sill has the factory paint marks on it. Would I trust it to drive on? Hell no.

  • avatar

    I suspect that tires will last a good long time before they fail. However, anyone who tracks their car knows that summer tires start losing maximum grip after about 2 years. I bought my car from an older guy who rarely drove it, garaged it, and generally babied it. The tires, Yokohoma S. Drives, had near full tread, but were already 4-5 years old. I drove on those tires for another 3 seasons and hours of light lapping, and always assumed my lack of confidence stemmed from my lack of experience and skill on track. When I finally put new, similarly-rated tires on the car, it was a night and day difference – much more grip.

    Regarding doughnuts: I’ve driven on a 14 year-old spare in my old Jetta, and it did the job just fine. Of course, you don’t want to be driving fast or long on a tire like that, but to get you to where you can get the flat repaired or replaced, I wouldn’t worry very much – how often do you need to drive more than about 60 miles to get that done?

  • avatar

    “not sure what caused it but possibly doing donuts”

    I’ve snowice drifted and Rockford’d my Volvo and the tires are still good, just had to add a little air in them. Granted I don’t do these frequently so I’m thinking that if donuts are a normal thing than you’re going to need spares more frequently.

    Also, you should hoot around in that Camry sometime, you don’t need to be told that a cars fun to have a fun time.

    • 0 avatar

      I happened to be out by myself in the FR-S and knew this parking lot was covered in a sheet of mostly virgin ice (besides the edges that were plowed). I did plenty of snow donuts in my old Contour SVT (with Michelin Arctic Alpins) so yes, FWD can be fun too!

      I have no idea what caused that flat – I put air in the tire a week later and have had zero issues the past 3+ months (of course, I haven’t driven the car a lot in this time but it still is holding air without an issue). The only causation I can think of is that I was sliding the car around on the ice, and the next time I went to drive the car that tire was flat.

  • avatar

    “The odds of getting stranded by a rotted temporary spare is less likely than an ordinary tire, as nobody wants to roll around on that tiny donut for an extended period.”

    You haven’t visited the Detroit metro area have you? Rolling on your temporary spare on a semi-permanent basis is step 1 in hooptification.

  • avatar

    A number of years ago I spent a couple of months in Indonesia on business. I came to realize that the standard for replacing tires there was when the tread had worn completely through to the cords. Tires are amazing structures that require substantial abuse to make them fail, in most cases.

    Track use is not comparable to every day driving for the stresses placed on tires. Most people are unwilling or unable to use the full acceleration, cornering or braking capability of their cars, even in emergency situations. So they can get away with poor tires and not notice anything.

    Inflation pressure is a controversial subject. The carmakers pressure recommendations should be viewed as minimum. On my Saab, that is stated so on the sticker, with higher pressures set for increased load and speeds. The tires sidewall pressure states the maximum. Yes, it produces a rougher ride at higher pressures. But load capability and handling are improved and rolling resistance is reduced. Hydroplaning speed is increased with higher pressure.

    I had the original tires on my 1972 Centurion bicycle until last year. The “gumwall” sidewalls had long crumbled to nothing. But the tread remained OK until the very end. That was 40 years. So I think perhaps the answer to the age discussion may lie in the fact that synthetic rubber does age, oxidize, and harden through UV exposure, but the rate depends on the quality of the rubber and the exposure history. If the rubber is hard and resistant to indentation, then don’t use the tire.

  • avatar

    One thing I’ve not seen mentioned in this thread is steel belt deterioration. I’ve had it happen with two sets of tires. The belt breaks, the tread gets distorted and it feels like a terrible case of imbalance. A frequent recommendation is not to use steel belted tires (most of them nowadays) beyond six years from date of manufacture i.e. not date of installation. Big problem with “collectible” cars, not so much daily drivers.

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