Tag Archives: valves

Marv’s Law of Bicycle Punctures….Revisited



Dear Roulers,

I had intended to write a wrap up of the Giro 2015 and list of where all the surviving Australians placed.  I will digress briefly to contgratulate Luke Durbridge for his second place in Stage 21.  However, this blog is about the new clause I’m adding to my eponymous law of bicycle punctures.  For the record this is second one in 3 weeks.  Its winter, its wet and there is all sorts of crap on the roads at the moment, so therefore its not unexpected.

So this morning I’m keen to do a medium paced, for me at least, 30km. The conditions are cold, wet and windless, in other words perfect for an early morning ride. I set off slowly, I’m still getting used to the SPD-SL clip in-action.  They are super-slippery in wet conditions.  I arrive at the second most irritating traffic lights in Port Melbourne, on the corner of Beaconsfield Parade and Pickles St, when I notice that horrible ride feeling of quickly deflated rear tyre…..sigh.

I’m still a bit sleepy and still warming up.  Consequently I’m mildly annoyed, however as I said before, its not unexpected. After a fit of the fumbles I managed to swap the inner tube over.  I start pumping air into the tyre when I realise …horror… nothing is happening.  I recheck the pump and its seal on the valve.  Then I realise that my new replacement tube has a faulty valve and that I do not have another spare or a repair kit.  Now I’m cold and really irritated.  I trudge back 1.5km back to my house, no doubt mangling the SPD-SL cleats.  I have no choice.  Its this or bare foot which on a wet, cold morning was unthinkable.

So lets go back to the law:

Clause (i) If you are going to get a puncture, it will be at most inconvenient time – Tick -> early morning was very irritating.

Clause (ii) It is inevitable that you will have more punctures on your back wheel – Tick -> back wheel it was.

Clause (iii) It more likely that you will have rear puncture when you haven’t cleaned your rear running gear and/or are wearing new clothing – Cross -> I had just cleaned by gears and I didn’t have new clothing on.

Clause (iv) It is more likely that you will get a puncture when it rains – Tick -> Yep it had rained heavily overnight.

Clause (v) It is more likely that you will get a puncture and then have the weather turn bad with heavy showers making your machine’s parts that much harder to handle. Tick -> It was wet and cold.

Clause (vi) It is more likely that you will get a puncture when you are riding alone when there is no one to help you. Tick -> Yep, I was alone.

Clause (vii) It is more likely that you will get a puncture, if you are stupid enough to boast about never getting one.  Cross -> Nope, I never thought this or said it out loud.

Not bad validation so far, now for another clause,

Clause (viii) It is more likely that you will get a puncture when you have a dud spare, for example one with a faulty valve and no other way of fixing the puncture. Tick -> Yep, this was very F%&#king irritating.

Until next time,


Flat tyres are irritating – Part 1

The Breakaway

Godamit!!!!….I’ve got another <<insert expletive of choice>> flat. If you ride on the road its inevitable that you’ll have this happen, much taxes, death and Richmond not winning AFL premierships.

The Leadout

This is the first part of a two part blogfest on flat tyres. The first part focuses on the types of flats and the second explains what you might be able to do avoid them.

Slow Leaks

  • First symptom of this kind of problem, is that the tire will need to be pumped up more often than it should and its starting to drive you mad :-).
  • However It is normal for a tube to lose air over a period of weeks. Racing bike owners you should check the pressure at least once per week.
  • Slow leaks that take more than an hour to go down can be tough to find, its better to install a new tube.
  • This type of flat is not normally associated with severe tire or rim damage.


  • Typically caused by glass, thorns, nails, staples, screws. Basically anything sharp can cause a puncture.
  • Depending on how big the hole is, the tyre can deflate very quickly. Usually these are easily located and repaired with patch kit.
  • This type of flat is not normally associated with severe tire or rim damage.

Pinch Flats

  • This type of flat is caused by rapid compression of the tube between your rim and a hard surface.
  • Known as ‘snakebites,’ these are dramatic, audible flats that deflate quickly.
  • These are difficult to repair with patches quickly. You may have to replace tube or use oval patches.
  • There’s really good chance you also have rim damage as well.


  • Blowouts are sudden losses of air, usually accompanied by a loud BANG!
  • Since the inner tube is just a rubber balloon, and does take much pressure by itself, it needs to be held inside of a tire to get up to full pressure.
  • If the tire doesn’t hold the tube in all around, the tube will pop. If this happens you’ll need a new tube.

Tire Damage

  • Improperly adjusted brakes can rub through tire and cause tube to blow out of tire.
  • Maintaining proper tire pressure helps prevent flats and maximizes rolling efficiency.
  • Worn tires leave less rubber between the tube and the road, decreasing flat protection


  • Spokes and sharp spots on the inside wall of the rim can cause flats.
  • Recurring flats are usually caused by sharp metal on the rim or part of a spoke.
  • Use a file or sandpaper to buff off the sharp spot and remove any burrs.
  • Its also worth replacing the rim tape.

Valve Damage

  • Any part of the valve and stem can get damaged through abuse or overuse, through which air can leak.
  • Sealants don’t typically work well on damaged valves. It’s time for a new tube.

Sidewall Cuts

  • The sidewall of a tire is not designed to contact anything, and is not durable like the tread of a tire.
  • This type of damage usually happens when you load your bike onto a vehicle, or leans it against something, like a curb, bench, or wall.
  • Once this happens, you’ll need to buy a new tyre.