When to change back tire?

[Clark Kent]

How does one know when it's time to put on a new back tire?

I  got my Valk with a worn back tire.  I have no idea how many miles it has on it.  

As usual  all the wear is in the middle of the tire.  The sides are new.

The sides have a bit more than 1/4 " tread. (new) the middle of the tire has about 1/3 of that left.  

I rode the bike 2000 miles last year and couldn't see much of any wear on the middle tread. (looks like it did when I got the bike)

Should I put a new tire on now?  

The tire is a Dunlop Elite  180/70R 16

Used the car tire trick , Penny and Lincolns head. The middle tread is about twice as deep as the edge of the penny to Lincolns head.

Thanks for any advice.

CK

[Cycho]

There is a wear bar on the tire, when the the tread wears to that point, replace the tire.

I have a 98 Valk with the original tyres still on. I know this is not common, but the tyres still have enough tread on them not to warrant changing, but because they are now almost 8 years old, they seem to have hardened: the material does not retain its characteristics when new.

So it's not only lack of tread depth that one has to consider for a tyre change.

[rodeo1]

clark

get yourself a tread depth indicator tool. available at most car part shops for about 10 bucks. replace the tires when they get down to 2/32

dennis

[Clark Kent]

Thanks to all who offered advice.  CK