I'm running 700x35 Marathon tires with their Greenguard puncture-resistance layer (not as thick as the Marathon Plus's, but it's there). Should I check the outside of the tires for bits of glass or similar material? If so, how often?

Mostly-urban riding; there's a bar en route to work that does sometimes sport the odd smashed bottle in the street.

  • Sure? Why wouldn't you? Commented Apr 24, 2014 at 23:24
  • Because it's not necessary?
    – D.Salo
    Commented Apr 25, 2014 at 1:36
  • Glass will often fall out by itself, I'd be more worried about bits of wire which can work their way in. Either way it's more likely to cause a normal puncture than a blowout so risks annoyance rather than crashing.
    – Chris H
    Commented Apr 25, 2014 at 10:50
  • It depends on how likely the hazard is. If you ride where there is lots of broken glass, thorns, etc, then checking is worthwhile. Commented Apr 25, 2014 at 13:43

2 Answers 2


Even if the glass doesn't work through the puncture proof layer (which it will, eventually), it's still a good idea to check once in a while for cuts etc, especially in the side walls, which almost never have a puncture proof layer. It's a "better safe than sorry" approach, but it takes all of five minutes to check both tires, so in my opinion that's time well spent if you know what happens when the tires blow out on a descent or, in your case, running a green light very late.


It's not a bad idea to make some checks, not just the tires but everything, from time to time.

For the tires, I wouldn't really worry about it unless you know you've been on a road with broken glass or something that you fear may puncture the tire, that would be the only situation where a check would be advisable (IMO of course).

I'm saying this because I hardly (never) check my tires, and there has been 4000Km and no punctures!

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