Hi, I'm changing the tyres on my RT-2 and it would be interesting to find out how old they are.
Front 3.25-19 Dunlop Trials Universal (T5Y201)
Rear 4.00-18 Dunlop Sports (A5A222). Both Made in Japan.

Anyone?

All the best!
Stefan, Sweden

Hi Stefan, most modern tires have a 4-digit date code stamped into a box, though I'm not sure they use the same format in every market. The first two digits are the month, and the second two indicate the year of manufacture.

The first two pictures below are Shinko tires that I bought recently. One of them was made in the 16th week of 2021, the other one was made in the 20th week of 2021.

The third picture is the date code a fifty-year-old Yokohama Trail Sport tire, and I have no idea how to read it.

   

Interesting fact Tom, seems for quite some time, Yamaha used a dating code from when an Emporer was in charge/power… then, it was how many years after that became the way to date it…. How would I know such stuff?
I have an old Yamaha guitar that uses that… it was stamped like 230… which is how many years after that reign… which put my guitar at a 1970.. FG-150…
Maybe helps? Maybe not..
Sneezles61

In the the 1970's US market tires were marked with a three digit code in ID number.  First two are week of production and last one is year.  Problem is they didn't think about decade changes because tires normally aren't supposed to be used for more than 10 years.

My best guess is front was made in the 20th week of 1971 and the rear was made in the 22nd week of 1972 or 1982...  maybe even 1992? 

Checking the production date on steering head and mileage on bike and condition of rear are good clues too.  If it's a high serial number bike produced around 6/72 both tires could be original.  More likely rear was replaced at some point. 

Just guessing though...  I had a part time job in a tire shop in the 70's and we used to advise customers to consider replacing tires once they got 4 or 5 years old even if tread looked good.  Tires were crap back then compared to now and blow outs were far too common...  TPMS has helped a lot too.

"Emperor" dates were used on Yamaha literature like brochures too...  here's a decoder someone posted here a few years ago.

 

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Thread hijack...  here's an example of the code on a Yamaha brochure for the 1976 DT175C. 

The "50.7" is the "Emperor date" which translates to July 1975.