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I was reading some product reviews for bike tires and came across a complaint from a customer who had received "new old stock" tires. Here's the relevant part of the review:

enter image description here

Feb 07, 2020

The two tires I received had the manufacture date stamp inside the tires of 2007 !!! THIRTEEN YEARS OLD RUBBER !!! ... In reading these pages you have seen reviews stating premature blow-outs, and greatly diminished tire wear. Both are symptoms of OLD rubber. ... It would be a good bet that this supplier bought-out some distributors ‘old stock’ for pennies-on-the-dollar. Let HIM eat his investment, not you. ... See the date stamp in the attached photo, both tires had the same stamp...

(source)

The review correctly states that other customers had complained about severe blowouts after relatively short miles, suggesting they too may have received tires too old to be reliable.

This seems plausible; but on the other hand I have some bikes with pretty old tires without problems. Of course riding conditions may also play a role.

In summary: is there a valid concern about otherwise new-condition tires that are 13 years old being unfit for use?


Note: I'm not asking for a judgement of this specific tire. It's just an example that prompted the question.

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    A lot has to do with how it's stored. In a cool, dark place, away from any petroleum fumes, a 13-year-old tire would likely still be in usable condition. But likely it's lifetime, before it develops cracks in the sidewalls, etc, would be cut in half. – Daniel R Hicks Apr 18 '20 at 17:51
  • And the main test of the condition of an older tire on a bike is to check it for wear and cracks. – Daniel R Hicks Apr 18 '20 at 18:05
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    I should add that exposure to ozone is another bad thing for tires. – Daniel R Hicks Apr 18 '20 at 20:31
  • There are plenty of tyres out there - the only reason to consider this one is if the price is really good. – Criggie Apr 18 '20 at 23:11
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    How sure can you be that's not (20)th (07)July 20(18)? Or some part code/manufacturing batch code that is only tangentially related to a date? – Affe Apr 19 '20 at 22:26
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A 13-year-old tire may be rideable for a few years, but it wouldn't be fair to sell it as new. It just won't last as long as a new one would, and the hardened rubber will perform worse and possibly wear faster.

So, not necessarily "unfit for use", but definitely "unfit for sale as a new one". But depending on storage conditions and the tire, even a few years can make a tire unusable, such as obvious hardening or visible cracks.


As for the particular review linked in the question, it seems the buyer has misread the date code.

The page identifies the tires as Schwalbe Marathon HS. The Schwalbe Warranty Page has this photo of their production code:

Schwalbe production code

The format appears to match the one in the question, but it still leaves at least two reasonable interpretations:

  • Day/Month/Year: giving dates of 20th July 2018 (question) and 26th September 2018 (warranty page).
  • Week/Year: giving dates of week 20, 2007 and week 26, 2009.

But, it appears that Schwalbe has changed their production code format with an extra digit in 2010 or so. Older sources, such as this recall from 2009 show a code that has only 5 digits before a letter:

Production code from 2009

Based on this, I'd say the format is Day/Month/Year and the date on the tire is 20th July 2018. It still makes the tires somewhat old to be sold as new, but not terribly so.

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  • The question is not about this specific tire. This is useful information but doesn't address the main point. – StayOnTarget Apr 20 '20 at 15:28
  • @UuDdLrLrSs The first paragraph does address the general question. But yeah, I guess for the general case the part about figuring out the particular date code is not as useful. – jpa Apr 20 '20 at 15:57
  • I didn't mean that as a criticism, I actually was hoping people reading would notice that. I didn't want people to focus only on this specific date code and perhaps not add information about tire age in general. I wish now I'd made this 2 different questions... – StayOnTarget Apr 20 '20 at 15:59
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is there a valid concern about otherwise new-condition tires that are 13 years old being unfit for use?

Yes, it is a valid concern.

As user48539 says tires degrade no matter what.
What we would like to know is:

  • Why?
  • How old is too old

Why?
The answer to "why" is oxidation over time.

I could find no studies that focus on bicycle tires specifically. The following is an excerpt related to automotive tires. Similar forces are at work on bicycle tires.

The phenomenon of tire age degradation or thermo-oxidative aging has been documented in technical papers going back more than 80 years, and according to one journal article from 1931, it wasn’t news then: “The auto-oxidation of rubber has been known for a long time, and for a long time, too, it has been known that it plays an important part in spontaneous deterioration or aging, and it has been the object of numerous studies of much interest.” Safety Research & Strategies Inc

Bicycle tires will oxidize at different rates depending on many variables. Exposure to sun, higher temperatures, the type of materials used in the tire, tire coatings, etc. can have an effect on the rate of oxidation over time.

What I've seen is that age - oxidation - reduces the flexibility of the materials that make up the bicycle tire.
enter image description here

As a tire rolls it flexes where it comes in contact with the road. When the casing material becomes inflexible and breaks it can't hold the bead and the tube will blow out of the tire. When the tread becomes inflexible it wears faster.

The tire tread, casing and sidewall become "crunchy" over time. They begin to break rather than flex.

How old is too old?
It depends on all those variables mentioned in the "why" part of the answer plus it depends on the application for the tire. Higher pressure, higher performance tires are less tolerant to degradation. And generally, higher pressure / performance tires are more likely to hurt the rider when they fail. If you have a low pressure, low performance application sometimes you can get away with a little more degradation.

You can tell a lot about a tire by how it feels.
(I'll probably catch some heat for this but here goes)
Get the tire in your hands and compare how it flexes to a newer tire. If you can twist the tire into a figure 8 with the same effort as a new tire, and with no crunching sounds, especially for a low pressure, low performance application - it's probably OK.

This won't help with mail order. Best to avoid old tires via mail order.

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    Need to consider the traction provided by new rubber vs old, hard rubber. There no doubt MTBer's on old tires suffer a loss of performance due lack of traction, but often it just means the ride takes a bit longer.... Road riders tend to crash if they go past traction limits. – mattnz Apr 19 '20 at 1:17
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    I’m not sure that low pressure is better since it (usually) means that the tire deforms more. – Michael Apr 19 '20 at 7:11
  • @Michael at you are right, if a tire hits a level of degradation that it can't hold the air pressure it does not matter. Generally a low performance, low pressure application demands less of a tire. 30 psi is easier to hold in than 110 psi. – David D Apr 19 '20 at 13:06
  • This actually answers the question. Good job David. – Cullub Apr 20 '20 at 23:00
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A 13 years old not used rubber is always subject to degradation of properties and it doesn't matter how good it is stored. Its operation time will be quite lower than a new produced tyre and there is no way to understand when and where it will fail.

If manufacturers find such products in their warehouses, they would scrap them for sure and investigate how could they stay like that for years.

My only doubt is its production time format, I have seen so many different date formats on rubbers, batteries, pipes, hoses etc. Most probably you read it correct but it doesn't have to be Day/Month/Year all the time. It could be serial number/quarter/year, pp/year, week/year, year/week, only last two digits of the year or all 4 digits of the year, year/batch number, etc... My point is 07122017 could be any of these:
date is for example

  • batch 0712, year 2020, week 17
  • batch 0712, PP 20, year 2017
  • or just 07 December 2017
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    Good to challenge the assumption about the date code. Actually the "20071814" couldn't correspond to an actual date. Checking with the manufacturer about the code seems necessary. – StayOnTarget Apr 19 '20 at 0:29
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All polymers degrade over time. If they didn't, it would be hard to quickly produce them in the first place (chemistry, that is).

Then again, the speed of the degradation can be orders of magnitude slower or faster, depending on the conditions. A tyre stored in cold, dry and dark place for 15 years can be way better than a tyre exposed to the weather conditions for a few months.

An adequate rider quickly adapts to tyre's age-reduced performance without even knowing that, just like one adapts to safely handle different brands and types of tyre.

I am sure I have used both automobile and bicycle tires older than 15 years with no ill effects, just by not doing stupid things.

The only inevitable result of an aged tyre are more frequent flats - up to the point of becoming unpractical.

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