To Deflate Or Not

In Articles by Glyn DemmerLeave a Comment

With so many variables it’s a hotly debated topic, many off-road enthusiasts cannot agree on pressures or percentages. Add to this the wide variety of off-road tyres available and it’s not easy to specify a “correct” pressure for a particular terrain.

This becomes complex as other factors come into play – the tyre size, sidewall thickness, vehicle mass (plus load) as well as the temperature of the tyres at the time of deflation.

Ultimately through trial and error as well as a process of elimination, you will determine your personal pressures for the terrain you are travelling.

Worth consideration are;

  • Consider the tyre fitted to your vehicle, the OE H/T tyre fitted to your vehicle may be more prone to cuts and punctures than an A/T tyre fitted aftermarket. This being due to sidewall construction and malleability once deflated.
  • If you are going to go off-road, fit an off-road tyre that is made for the purpose, check the specifications and even consider doing this at the time of purchasing your vehicle- often your dealer is able to get a rebate for the H/T tyres fitted which makes the purchase easier. Look for an off-road tyre with an LT ( light Truck) sidewall, you will see this on the sidewall.
  • Deflate when off-road even if the manufacturer does not advise it, you will benefit from the additional traction when off the tar and does not damage the terrain as much as a hard tyre. A minimal change in pressure will in many cases bring about a major increase in traction.
  • If you have deflated significantly be careful of sharp turns or wheelspin which could take a tyre off the rim.
  • Play with deflation between the front and rear, a rear tyre that is deflated more than front tyres are not affected by turns and the load that places on the sidewall.
  • Carry a tyre pressure gauge at all time but if caught out do not deflate once you see a bulge in the sidewall that you can press in with your knee, to deflate evenly simply count down, 1 thousand, 2 thousand etc. to 30 thousand (seconds), this ensures even deflation, evaluate the sidewall after 30 counts before continuing.
  • If you are going to deflate then you should have a tyre pressure gauge and a decent compressor as well as a puncture repair kit as part of your equipment.
  • After deflation should you then move to gravel or tar it is critical that you inflate your tyres, heat builds up on a deflated tyre used at speed could cause a critical failure.
  • If you are travelling on long sections of gravel road a slight decrease in pressure will improve your vehicles handling and soften the bumps and corrugations.
  • Put the tread on a sharp obstacle, it’s stronger and easier to repair. The sidewall is more prone to failure through damage
  • Watch the colour, a tyre that takes on a blue tinge may be under-inflated an overheating.
  • Remember deflation increases the length of, not the width.
  • Understand the construction of the tyres sidewall and the impact of deflation. To get a great footprint a 2-play(sidewall) H/T tyre will need less deflation than a 3-ply (sidewall) A/T or M/T.

 

Some suggestions on deflation.

 

Tar or cement roads: 100% of your manufacturer’s recommended pressure.

Gravel: 10 – 15% deflation.

Corrugated gravel  roads: 10 – 15%

Sharp rocks and shale: 10 – 15%

Smooth rocks: 20 – 50%

Mud: 25%

Sand: 50 – 60%

Water: dependant on the undersurface

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