Tag Archives: flats

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 2

The Leadout

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

The Breakaway

You have two basic choices, change the way you ride or pony up for some new kit for your bike.

The Peloton

The cheaper choice – change the way you ride

Tactic Description
Road positioning This is often caused by poor road position: people often get an unusual number of flats because they are riding in or close to road gutter. The main travel lanes of most roads are kept fairly clear of glass and other dangerous debris by passing motor traffic. Cyclists who travel in the normal traffic areas of the roadway benefit from this. It also improves your visibility to motorists and provides greater room to move around obstacles.
Pressure Tire pressure is the hardness to which a tire is inflated. This is commonly measured in PSI – pounds per square inch. The “correct” inflation pressure is determined by the weight load, the tire width, and, to some extent, the riding surface. Getting it right can play a major role in puncture prevention. Too low and you may pinch the inner tube if you hit a pothole. Too high and you increase the risk of penetration punctures. Around 100psi is a good starting point for most road bike cyclists but consult the recommended pressure printed on your tyre. Less well known is the downside of over-inflation; this causes a harsh ride and can also cause poor traction on bumpy surfaces as over-inflated tires tend to bounce, breaking traction on the road surface.
Stop and check the tyre The pent-up air in your tubes wants desperately to join its friends in the atmosphere. If you ride over sharp objects, immediately sweep your tire with a gloved hand to remove debris.

The more expensive option – buy some new kit

Tactic Description
Tubeless tyres If The tubeless tyre you have a need for speed but still want to reduce your vulnerability to punctures, tubeless clincher tyres may be worth a look. With no inner tube within the tyre casing, pinch flat punctures should be a thing of the past and they roll quickly at lower air pressures so the risk of penetration punctures should also be lessened. They also work very effectively with liquid sealants; a small amount in each tyre should seal up any punctures in the tread area before too much air pressure is lost.
Thornproof tubes Special “thornproof” inner tubes protect against thorns and glass shards. These tubes are very thick on their outer circumference, so that a short thorn or a small glass shard may be embedded in the tube without being able to reach in far enough to let the air out. The outer wall of the tube is about five times as thick as a standard issue tube (see the cross section on the right) and this reduces the risk of penetration. They also weigh around 150g more than a standard issue tube—that’s 300g of additional rotating mass on your bike.
Tire Liners Tyre liners are made from robust but flexible nylon and fit between the tyre casing and the inner tube eg Mr Tuffy. They add weight and stunt tyre performance but will dramatically reduce the chance of penetration punctures. Just ensure that the liners are fitted properly with no angled edges where they are cut to size—poorly fitted liners can actually cause punctures.
Kevlar re-inforced tyres Kevlar-belted tires have a layer of kevlar under the tread surface, with the purpose of making the tire more resistant to punctures caused by small sharp objects, such as thorns and glass slivers. Kevlar-belted tires have slightly higher rolling resistance, price and weight than corresponding tires without the belt. Advantage of being fold-able and therefore transportable on long rides.

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.