enter image description here I am using Schwalbe lugano 700*25C for commuting, it's a almost brand new tyre with less than 500km. Recently I am starting to find some cuts around 1cm on my the tyre thread. Does anyone know what's the cause of a tyre cut? I inflate the tyre slightly above the max rated psi, is that part of the problem?

  • I recommend you add a photo so we can have a look at the kind of cut you are talking about.
    – brendan
    Commented Nov 10, 2015 at 1:39
  • 2
    Also - why do you inflate them over the max? You wont get any increased speed from that, just a greater chance of the tyre coming off the rim...
    – brendan
    Commented Nov 10, 2015 at 1:40
  • The tire pressure itself should not be a problem, so long as you're not exceeding the sidewall upper bound by 30% or more. The cuts, however, could be due to riding through broken glass, and damage from that is probably slightly more likely at higher pressure. (A picture or three would help a lot.) Commented Nov 10, 2015 at 1:52
  • Gidday and welcome to SE Bicycles. I think your tyre cut is caused by a foreign object. Did you find anything embedded in the cut? Was it deep enough to cause a puncture? Are you riding a route with broken glass ? Or do you park your bike in a bad spot and some non-cyclist has slashed it ?
    – Criggie
    Commented Nov 10, 2015 at 2:18
  • Yeah, looks like broken glass, or perhaps metal fragments from a manufacturing operation nearby. (First time I rode my current bike I picked up a fragment of cast iron in the tire.) Commented Nov 10, 2015 at 3:27

1 Answer 1


That looks like broken glass cut to me, you might find the remains of the sliver in the bottom of the cut. Over time that fragment will work inwards and eventually you will get a puncture.

That's left will be smaller than this, the sharp, flat edge that actually cut into your tyre then broke off:

enter image description here

This question has photos of a similar problem, where not getting the fragment out meant puncture after puncture. And this shows the punctures you get.

One maintenance task some people do is to get a sharp metal object and dig all the little splinters of glass out of their tyres. That does reduce the number of punctures, but in my experience it saves ten minutes of puncture repair for every hour or two of picking bits out of the tyre. It's not worth it. Instead I use puncture resistant tyres, which are heavier and slower than ones like yours. I probably spend an extra hour riding for every ten minutes of puncture fixing avoided... but I ride partly for fitness so that doesn't bother me.

  • An hour or two picking out debris versus a ten minute fix may be a bit of an exaggeration. And picking out debris is at the comfort of your shop/home.
    – paparazzo
    Commented Nov 10, 2015 at 5:42
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    If you spend 15 minutes every second week to save a puncture every two months, that's an hour per puncture.
    – Móż
    Commented Nov 10, 2015 at 8:57

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