Punctures!

article036Is the scene just too familiar? You’re out riding with your buddies, putting dirt under your tyres at a rate of knots; you’re fit, technically skilled and in your element – nothing can stop you… except for ANOTHER flat tyre! Your team is getting impatient, your rivals are waving cheerfully as they pass you.

The first step to reducing the number of punctures you’re getting is to understand what type of punctures are hounding you. There are four typical mechanisms:

  1. Piercing punctures involve something (thorns, branches, or glass, for example) penetrating your tyre either on the tread or through the side-wall, and then rupturing the tube. The wind you put into your tyre then becomes part of the sky, and you stop. There is typically a single hole on the outer circumference of the tube, usually small and round but sometimes large and irregular
  2. Snake-bites occur when the tube is pinched between two objects, usually a rock on the one side and your rim on the other. Obviously your tyre is sandwiched in there somewhere, but it doesn’t play an active role. Snake-bites are typically two parallel slits along the length of your tube, between 3mm and 10mm apart, and up to 20mm in length
  3. Spoke punctures are like piercing punctures, except the offending object is an over-stretched spoke that pokes through the rim tape. The hole is usually a little larger than a piercing puncture, and may be irregular; however, the give-away is that it is on the inner circumference
  4. Blow-outs occur when the tyre jumps off the rim, and is no longer able to contain the tube. These are instantaneous (although a “bubble” may exist for some time before the tube ruptures) and are easy to identify – your tyre is partially or completely off the rim, and there are tatters of tube hanging out.

Now that you know what types of punctures you are getting, you can start solving the problem.

Spoke punctures are the most obvious – replace the offending spoke, or file down the end! With the double-butted rims and improved spoke alloys we use today, this is seldom a problem anymore. However, if you seriously buckle your wheels repeatedly, and have to re-true them, watch out. Running lower spoke tension will both reduce the stretching of the spokes, and may increase your wheel strength. The old attitude of the tighter the better in no longer widely supported. Remember to replace the rim tape whenever you replace a spoke nipple or otherwise move the tape; three or four turns of standard electrical insulation tape provides a cheap, effective alternative to commercial rim tape.

Blow-outs are usually the result of running your tyres outside recommended pressures (usually around 35-65psi), having badly worn beads (the bit of wire or Kevlar that holds your tyre onto your rim), major cuts or wear in the side-walls, hitting a stone too hard, or poor technique when replacing a tube. If you run your pressures way outside spec and use tyres in poor condition, you should probably sell your bicycle for your own safety. If you hit stones too hard on a regular basis, try running higher pressures and wider tyres (tyres up to 2.1” at least are usable for AR – strong riders should be able to use 2.3”, but that is beginning to get silly and some bikes won’t accept the tyres). If you generally blow out very soon after changing a tyre or tube, take more care to properly seat your tyre onto your rim, without the tube being trapped between the two at any point.

There are a common set of ways to reduce the chances of snake-bites and piercing punctures, or to cure the problem without stopping.

  • This one is a serious no-brainer, but it caused me an extra puncture (last tube!) on a long ride in Wales one winter just as night was falling: when you get a puncture, FIND THE OFFENDING OBJECT!!! Run you fingers along the inside of the tyre and pull the tyre liner through your fingers a couple times until you find the thorn or piece of glass. You may need pliers or a knife to extract a large thorn. Also ensure that no grit is left in the tyre
  • If you get a large cut in the side-wall, put a piece of plastic e.g. an off-cut of your tyre liners, the side of a plastic margarine tub or some heavy cardboard, inside the tyre to cover the cut – make sure it extends a long way and don’t take the rocks too fast
  • Tyre liners are strips of plastic that you lay between your tube and tyre. They help deflect piercing objects (only coming through the tread – no help for side-punctures) and give a little bit of bulk to ward off snake-bites; the weight and cost penalties are minimal. Ask at your local mountain bike shop
  • Lots of people use slime – a green gunk that forms a “scab” to seal a puncture, much like blood clotting. With car valves, remove the valve and squeeze in the slime. With road-type valves you’ll have to cut a small hole in your tube, pour the slime in, and repair the hole. Slime adds a little weight, which some people claim to notice when sprinting. However, a bigger problem comes when you try to change your tube, or reduce the pressure – unless you are careful, the slime seals your valve, forcing you into drastic action, like ripping your tyre apart, or riding on a semi-inflated tube. That said, I have seen slime perform impressively.
  • Higher tyre pressures often help reduce the chances of either type of puncture, especially snake-bite. Slightly lower rolling resistance may off-set the slightly less comfortable ride and reduced traction – not a lot in it for AR. Tyre pressures and tubeless tyres are dealt with later.
  • Harder, thicker tyres, particularly in the side-walls, are less prone to punctures, but obviously weigh more. A while back, I got some ultra-light Panaracers to try out – I was snake-biting like nobody’s business, no matter what pressure I used. I swapped back to my trusty Michelin Wildgripper 1.85” tyres and the problem went away. Maxxis tyres have proven to be nicely puncture-resistance, despite running them at 30-35psi
  • A more conservative riding style, particularly for heavier riders, may also help – go around the sharp rocks and thorn trees, not over them!
  • Valves should be kept clean, and tubes and tyres replaced when they show signs of wear. If you are riding with Presta (road-type) valves, remember to tighten the bead!
  • For important events, consider new tubes, and, possibly, a pair of competition-only tyres. This is more important for road riding, where tyre pressures are much higher, speeds are greater and the consequence of a flat more severe – a few minutes can be devastating and a sudden flat at 80km/h isn’t fun.
  • Patching should be done with great care, to ensure the perfect seal. Practice makes perfect. Park Instant Patches have had very good reviews, but all other instants are looked down on. Conventional patching requires up to an hour before the tube can be used (depending on the temperature). Carry spares and patch immediately so the tube is ready later – however, there is a technique that involves burning the cement on the tube; I haven’t tried it, but it is reputed to allow the tube to be used within a couple minutes.
  • Talcum powder between the rim and the tube is supposed to reduce the wear on the tube, and the chances of snake-bite. I’ve never tried this
  • There is only one fail-safe way to prevent punctures, though: perma-tubes. These are closed-cell foam rings that you fit instead of tubes. They offer the worst of all worlds – non-adjustable, heavy, uncomfortable, etc, but do ensure you never get a puncture. When cycling the Karakorom Highway, I seriously consider these.

There are several other considerations when talking about tyre pressures

  • XCountry junkies and roadies often use “bombs” – small CO2 cylinders – to reinflate their tyres. While this may shave a minute off the process, they cost money, weigh a bit and can’t be reused during the race. Also, the CO2 molecule is smaller than nitrogen (the main component of air) and so leaks out of tubes faster. While this isn’t significant during a 3-hour road race, it could be in AR or endurance cycling.
  • In the past, Schrader (car-type) valves lost pressure and tyres had to be refilled every few days. This is less of a concern today, but I still prefer Presta (road-type) valves – I find them easier to use. They fit all rims, while Schrader valves only fit Schrader-drilled rims
  • Tubeless tyres, such as the UST system, do not snake-bite, as there is no tube to pinch. However, the softer compounds mean the (very expensive – R500+) tyres wear faster and lose pressure (up to 10psi/day starting at 60psi). They are also a mission to repair or fit a tube to when you do puncture and are expensive (in case I didn’t mention). They are also more prone to side-wall cuts because of the softer compound. The added traction and smoother ride are irrelevant to AR
  • Recently, a product was launched in the UK to convert your standard non-UST rim and tyre combination into tubeless, at relatively low cost. This has had good reviews to date and offers to by-pass many of the problems associated with UST. It is still unclear, though, whether this system is useful in AR

OK – you’ve still punctured for the hundredth time on this leg, you’ve run out of tubes, and your patch kit is with your seconds. What now?

  • Walking isn’t always an option, but think about it – it will help you to remember tyre liners and slime next time!
  • Bum tubes off your rivals. This may involve hiding in bushes with heavy rocks to throw at them as they pass, or out in the middle of the track with your tastiest food laid out in front of you, while you genuflect before them.
  • Stuff your tyre with grasses. This isn’t a joke – it gave me hope on the Logwood Classic last year! You will have the bumpiest ride of your life, with awful traction, so take it easy. Fill them as hard as you can and stop every few kilometres to refill your tyres as the grass gets milled to dust.
  • Select the tube in the worst condition, but ensure it only has one hole. Cut it clean through at the hole, and knot both ends twice. Put this into your tyre, and pad the gap with as much NON-SPIKEY grass as possible. This gives a better ride, but is harder to get right, than the grass trick.
  • Strap your bike to your back, and hop on the back of your buddy’s bike – make sure he’s the strongest rider and has an inferiority complex. Patronisingly suggest that you’re happy to take over “when he gets tired”

Tyre pressures are a constant source of debate in some circles. Lower pressure gives better traction (ask the downhill or trials riders – they run down to 12 or 13psi sometimes) and a smoother ride, but increase, particularly, the chances of snake-bites. Lighter riders, or those with fat tyres and dual suspension can get away with lower pressures. Weighing in at 90kg in my riding kit, I run 50psi on my hard-tail with 1.85” tyres, and 35psi on my dual-suspension endurance bike with 2.1” tyres. I run my road bike at 80psi with 23mm tyres. I used to run a lot harder, but the traction and comfort have won me over.

Track pumps are well worth the money – they last longer than mini-pumps, and allow you to deliver exact, and higher, pressures. Crank Bros, from the US, produce a smart mini-pump with a pressure gauge that can deliver up to 80psi without too much hassle; however, there are no importers to South Africa, and it would retail at over R300.

This article has sought to give a few ideas about what causes punctures, and how to reduce your chances of slowing your buddies down. Experiment – there are lots of other little tricks out there

the scene just too familiar? You’re out riding with your buddies, putting dirt under your tyres at a rate of knots; you’re fit, technically skilled and in your element – nothing can stop you… except for ANOTHER flat tyre! Your team is getting impatient, your rivals are waving cheerfully as they pass you.

The first step to reducing the number of punctures you’re getting is to understand what type of punctures are hounding you. There are four typical mechanisms:

  1. Piercing punctures involve something (thorns, branches, or glass, for example) penetrating your tyre either on the tread or through the side-wall, and then rupturing the tube. The wind you put into your tyre then becomes part of the sky, and you stop. There is typically a single hole on the outer circumference of the tube, usually small and round but sometimes large and irregular
  2. Snake-bites occur when the tube is pinched between two objects, usually a rock on the one side and your rim on the other. Obviously your tyre is sandwiched in there somewhere, but it doesn’t play an active role. Snake-bites are typically two parallel slits along the length of your tube, between 3mm and 10mm apart, and up to 20mm in length
  3. Spoke punctures are like piercing punctures, except the offending object is an over-stretched spoke that pokes through the rim tape. The hole is usually a little larger than a piercing puncture, and may be irregular; however, the give-away is that it is on the inner circumference
  4. Blow-outs occur when the tyre jumps off the rim, and is no longer able to contain the tube. These are instantaneous (although a “bubble” may exist for some time before the tube ruptures) and are easy to identify – your tyre is partially or completely off the rim, and there are tatters of tube hanging out.

Now that you know what types of punctures you are getting, you can start solving the problem.

Spoke punctures are the most obvious – replace the offending spoke, or file down the end! With the double-butted rims and improved spoke alloys we use today, this is seldom a problem anymore. However, if you seriously buckle your wheels repeatedly, and have to re-true them, watch out. Running lower spoke tension will both reduce the stretching of the spokes, and may increase your wheel strength. The old attitude of the tighter the better in no longer widely supported. Remember to replace the rim tape whenever you replace a spoke nipple or otherwise move the tape; three or four turns of standard electrical insulation tape provides a cheap, effective alternative to commercial rim tape.

Blow-outs are usually the result of running your tyres outside recommended pressures (usually around 35-65psi), having badly worn beads (the bit of wire or Kevlar that holds your tyre onto your rim), major cuts or wear in the side-walls, hitting a stone too hard, or poor technique when replacing a tube. If you run your pressures way outside spec and use tyres in poor condition, you should probably sell your bicycle for your own safety. If you hit stones too hard on a regular basis, try running higher pressures and wider tyres (tyres up to 2.1” at least are usable for AR – strong riders should be able to use 2.3”, but that is beginning to get silly and some bikes won’t accept the tyres). If you generally blow out very soon after changing a tyre or tube, take more care to properly seat your tyre onto your rim, without the tube being trapped between the two at any point.

There are a common set of ways to reduce the chances of snake-bites and piercing punctures, or to cure the problem without stopping.

  • This one is a serious no-brainer, but it caused me an extra puncture (last tube!) on a long ride in Wales one winter just as night was falling: when you get a puncture, FIND THE OFFENDING OBJECT!!! Run you fingers along the inside of the tyre and pull the tyre liner through your fingers a couple times until you find the thorn or piece of glass. You may need pliers or a knife to extract a large thorn. Also ensure that no grit is left in the tyre
  • If you get a large cut in the side-wall, put a piece of plastic e.g. an off-cut of your tyre liners, the side of a plastic margarine tub or some heavy cardboard, inside the tyre to cover the cut – make sure it extends a long way and don’t take the rocks too fast
  • Tyre liners are strips of plastic that you lay between your tube and tyre. They help deflect piercing objects (only coming through the tread – no help for side-punctures) and give a little bit of bulk to ward off snake-bites; the weight and cost penalties are minimal. Ask at your local mountain bike shop
  • Lots of people use slime – a green gunk that forms a “scab” to seal a puncture, much like blood clotting. With car valves, remove the valve and squeeze in the slime. With road-type valves you’ll have to cut a small hole in your tube, pour the slime in, and repair the hole. Slime adds a little weight, which some people claim to notice when sprinting. However, a bigger problem comes when you try to change your tube, or reduce the pressure – unless you are careful, the slime seals your valve, forcing you into drastic action, like ripping your tyre apart, or riding on a semi-inflated tube. That said, I have seen slime perform impressively.
  • Higher tyre pressures often help reduce the chances of either type of puncture, especially snake-bite. Slightly lower rolling resistance may off-set the slightly less comfortable ride and reduced traction – not a lot in it for AR. Tyre pressures and tubeless tyres are dealt with later.
  • Harder, thicker tyres, particularly in the side-walls, are less prone to punctures, but obviously weigh more. A while back, I got some ultra-light Panaracers to try out – I was snake-biting like nobody’s business, no matter what pressure I used. I swapped back to my trusty Michelin Wildgripper 1.85” tyres and the problem went away. Maxxis tyres have proven to be nicely puncture-resistance, despite running them at 30-35psi
  • A more conservative riding style, particularly for heavier riders, may also help – go around the sharp rocks and thorn trees, not over them!
  • Valves should be kept clean, and tubes and tyres replaced when they show signs of wear. If you are riding with Presta (road-type) valves, remember to tighten the bead!
  • For important events, consider new tubes, and, possibly, a pair of competition-only tyres. This is more important for road riding, where tyre pressures are much higher, speeds are greater and the consequence of a flat more severe – a few minutes can be devastating and a sudden flat at 80km/h isn’t fun.
  • Patching should be done with great care, to ensure the perfect seal. Practice makes perfect. Park Instant Patches have had very good reviews, but all other instants are looked down on. Conventional patching requires up to an hour before the tube can be used (depending on the temperature). Carry spares and patch immediately so the tube is ready later – however, there is a technique that involves burning the cement on the tube; I haven’t tried it, but it is reputed to allow the tube to be used within a couple minutes.
  • Talcum powder between the rim and the tube is supposed to reduce the wear on the tube, and the chances of snake-bite. I’ve never tried this
  • There is only one fail-safe way to prevent punctures, though: perma-tubes. These are closed-cell foam rings that you fit instead of tubes. They offer the worst of all worlds – non-adjustable, heavy, uncomfortable, etc, but do ensure you never get a puncture. When cycling the Karakorom Highway, I seriously consider these.

There are several other considerations when talking about tyre pressures

  • XCountry junkies and roadies often use “bombs” – small CO2 cylinders – to reinflate their tyres. While this may shave a minute off the process, they cost money, weigh a bit and can’t be reused during the race. Also, the CO2 molecule is smaller than nitrogen (the main component of air) and so leaks out of tubes faster. While this isn’t significant during a 3-hour road race, it could be in AR or endurance cycling.
  • In the past, Schrader (car-type) valves lost pressure and tyres had to be refilled every few days. This is less of a concern today, but I still prefer Presta (road-type) valves – I find them easier to use. They fit all rims, while Schrader valves only fit Schrader-drilled rims
  • Tubeless tyres, such as the UST system, do not snake-bite, as there is no tube to pinch. However, the softer compounds mean the (very expensive – R500+) tyres wear faster and lose pressure (up to 10psi/day starting at 60psi). They are also a mission to repair or fit a tube to when you do puncture and are expensive (in case I didn’t mention). They are also more prone to side-wall cuts because of the softer compound. The added traction and smoother ride are irrelevant to AR
  • Recently, a product was launched in the UK to convert your standard non-UST rim and tyre combination into tubeless, at relatively low cost. This has had good reviews to date and offers to by-pass many of the problems associated with UST. It is still unclear, though, whether this system is useful in AR

OK – you’ve still punctured for the hundredth time on this leg, you’ve run out of tubes, and your patch kit is with your seconds. What now?

  • Walking isn’t always an option, but think about it – it will help you to remember tyre liners and slime next time!
  • Bum tubes off your rivals. This may involve hiding in bushes with heavy rocks to throw at them as they pass, or out in the middle of the track with your tastiest food laid out in front of you, while you genuflect before them.
  • Stuff your tyre with grasses. This isn’t a joke – it gave me hope on the Logwood Classic last year! You will have the bumpiest ride of your life, with awful traction, so take it easy. Fill them as hard as you can and stop every few kilometres to refill your tyres as the grass gets milled to dust.
  • Select the tube in the worst condition, but ensure it only has one hole. Cut it clean through at the hole, and knot both ends twice. Put this into your tyre, and pad the gap with as much NON-SPIKEY grass as possible. This gives a better ride, but is harder to get right, than the grass trick.
  • Strap your bike to your back, and hop on the back of your buddy’s bike – make sure he’s the strongest rider and has an inferiority complex. Patronisingly suggest that you’re happy to take over “when he gets tired”

Tyre pressures are a constant source of debate in some circles. Lower pressure gives better traction (ask the downhill or trials riders – they run down to 12 or 13psi sometimes) and a smoother ride, but increase, particularly, the chances of snake-bites. Lighter riders, or those with fat tyres and dual suspension can get away with lower pressures. Weighing in at 90kg in my riding kit, I run 50psi on my hard-tail with 1.85” tyres, and 35psi on my dual-suspension endurance bike with 2.1” tyres. I run my road bike at 80psi with 23mm tyres. I used to run a lot harder, but the traction and comfort have won me over.

Track pumps are well worth the money – they last longer than mini-pumps, and allow you to deliver exact, and higher, pressures. Crank Bros, from the US, produce a smart mini-pump with a pressure gauge that can deliver up to 80psi without too much hassle; however, there are no importers to South Africa, and it would retail at over R300.

This article has sought to give a few ideas about what causes punctures, and how to reduce your chances of slowing your buddies down. Experiment – there are lots of other little tricks out there.

Author: Dylan Morgan