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Emergency Repairs

01 December 2013

Flat Tyre

A puncture is the one event that happens all too regularly when you're riding off-road. Always carry a pump, spare tube and puncture repair kit. 

  1. Remove the wheel by undoing the quick release by unscrewing it a few turns. If you have a thru-axle you'll also need to whip out the axle.
  2. A good trick to encourage your rear wheel to drop out easily, and make putting it back in a snip, is to first select the smallest gear in your rear cluster. 
  3. You'll need to use two tyre levers in tandem to force the tyre off the rim. Place the flat end between the rim and the tyre. Lock one lever in place by hooking it onto a spoke, run the other around the wheel circumference to ease the tyre off. 
  4. Extract the tube from underneath the tyre (sounds like a dental procedure). Punctures generally are the result of either a snake bite (the tube is pinched by the rim - caused by hitting a big bump with a tyre that is too soft), or a sharp object making a hole (often gorse prickles or matagouri thorns). The prickle will most likely be still embedded in your tyre, so carefully check the inside by touch and sight, and remove the offending blighter. If you take the tyre off the rim, ensure you put it back the right way round (the rotation arrow on the sidewall should match the direction the wheel rolls when you travel forward). 
  5. If your spare tube is still intact then use it (repair the wrecked one when you get home - fixing tubes in the field is a pain and should be avoided if at all possible). Partially inflate the new tube. Tuck it under the tyre and place the valve through the hole in the rim. Starting at the valve, ease the tyre back onto the rim. It gets tricky as you complete the circle (how Zen) - use your whole hand to roll the tyre on. 
  6. Don't use tyre levers - they tend to pinch the tube causing a further puncture and considerable audible obscenities. You may need to let a little pressure out to complete the manoeuvre.

Beyond tubes you can upgrade to a tubeless system like Stans with liquid sealant. Small punctures self-seal and you can run lower pressure without suffering pinch flats (snake bites).

Pump it up

  • There are two common types of valve: Schrader (just like on a car) or Presta (also known as a French valve). Any decent pump can handle either type by juggling a couple of its components: a rubber sleeve and a "pointy" valve depressor. Schrader valves require the wider diameter to fit over the valve with the depressor sticking back into the valve. For Prestas, reverse both pieces so the pointy bit is aiming into the pump, and the smaller diameter hole fits around the valve. For the details, check out the operating instructions for your model pump.
  • Ensure valve is seated properly, so it is straight up and down in the rim. Now pump the sucker up. Try it with the wheel upright and the valve at the '12 o'clock' position. Wrap your thumb and fore finger around the tyre and the pump, to hold every thing in place while you give it the kiss of life.
  • The tyre pressure should be between 60psi (bloody hard) and 35psi (can depress about 5 - 10 millimetres with your thumb). Firmer is better on the road, softer for when you need more traction, eg muddy, wet conditions. Lighter riders can get away with lower pressures.
  • Put the whole catastrophe back together - spin the tyre to make sure nothing is rubbing and you're away.

Tube Repair

  • Find the leak - not always a simple task. Inflate the tube until it's obese (about 75mm diameter). You'll be able to hear or feel air escaping (use your cheek or the back of your wrists). For slow leaks immerse the tube in water - little bubbles should lead you to the leak.
  • Mark the spot (crayon, white chalk or twink works a treat) and deflate the tube.
  • Stretch the tube over the handle of your pump, roughen up the surface with sandpaper, then smear vulcanising solution onto the tube (covering slightly larger area than the patch you're going to use).
  • Once the solution is tacky dry (about 5 minutes), peel the foil off the patch and press it firmly onto the tube (stretched over your pump again). Use pump like a rolling pin to apply extra pressure.
  • Leave to set for a few minutes, remove the plastic film and inflate to test the seal and make sure there are no other holes (be warned - snake bites usually come in pairs).

Broken Chain?

  • Locate the damaged links and nut out which bits you will need to remove - ensuring you're left with a male and female end. Or two male ends if you are using a 'quick-link'.
  • Whip out your chain breaker and squeeze the pin through to release the damaged link. Be sure not to push the pin out completely (again, unless you're using a quick-link to re join it).
  • Re-thread the chain around your drive bits - especially the front derailleur. Join the two ends together by squeezing the pin back in or use your 'quick-link'. Note that some chains require a special oversize chain pin - check with your shop.
  • Use the spacer to ease the links so they move freely. This is not necessary if you've used a 'quick-link'.
  • If the chain is getting a bit short insert your spare links or limit your gear selections to the smaller cogs.