DEFLATION a 12V air compressor pumping up off-road tire

 

The subject of tire deflation is a controversial one. With so many variables at play, many off-road enthusiasts battle to agree on figures. What’s more, with a near-infinite number of terrain types on offer, it’s hard to know what pressure is right for the job.

 

This point is further complicated by other variables, such as tire size, vehicle mass (including payload) and tire construction (sidewall thickness). Then, one must also consider pressure fluctuations caused by heat and rising road temperatures.

 

In the end, the art of tire deflation is best mastered through a process of trial and error – one determined by personal preference, vehicle setup, and tire brand. However, to help in this process, here are a few deflation tips to consider…

 

1) DEFLATION FOR STRENGTH

A deflated A/T (off-road) tire can be (up to) 1000% more puncture-resistant than an OE fitted H/T tire! This is mostly due to the tire becoming more subtle and “malleable” to the terrain, but its also due to better weight distribution thanks to a larger tire footprint.

 

2) FIT DEDICATED OFF-ROAD TIRES

Unfortunately, a number of all-terrains look like off-road tires as far as tread design is concerned, but in terms of durability, weight, and puncture resistance, they’re no different to a high-way terrain. For example: Using a 265/65/17 as an example, the Cooper S/T Maxx weighs 24.5 kg, while many OE specced all-terrains are little more 18 kg.

 

That said, the difference is usually a matter of Light Truck tires versus Passenger-carcass alternatives. Be sure to look for the letters “LT” on the tire’s sidewall.

 

35 inch Cooper S/T Maxx

Be sure to fit a genuine light-truck all-terrain tire, many OE products are NOT heavy-duty in terms of carcass construction.

3) ALWAYS DEFLATE

Most vehicle manufacturers will tell you to stick to your vehicle’s recommended tire pressure – as per the service manual. However, most 4x4 training courses advise that your tires be deflated when driving off-road. The information is conflicting, but rest assured, a deflated tire offers considerably more traction off-road.

 

If you’re still undecided, don’t let traction be your motivating factor, consider the environment. A deflated tyre is safer, more comfortable, and far less harmful to the environment.

 

4) SMALL CHANGES, BIG RESULTS

Don’t underestimate the impact of a small tire-pressure change, even if it’s just 0.2 Bar. For example, what may not be possible at 1.0 bar, could be a breeze at 0.8 bar.

 

5) AVOID SHARP TURNS

Never perform a sharp turn if your tires are deflated below 1.2 bar – doing so will place pressure on the tire’s sidewall and may cause it to de-bead off the rim.

 

6) FRONT & REAR 

Your 4x4’s rear tires can be deflated slightly more than the front tires; this is because the rear tires are not subjected to turns and sidewall load. This is especially the case when driving in soft sand.

 

Cooper S/T Maxx on Land Cruiser

In most cases, you can deflate your 4x4’s rear tires more than the front.

 

7) GOING BY SIGHT

If you don’t have a tire pressure gauge with you, and you’re about to drive over sharp rocks, stop deflating the moment you notice the tire bulging at the sidewall.

 

8) ESSENTIAL GEAR

Always travel with an accurate tyre-pressure gauge, a heavy-duty compressor, and a puncture-repair kit in your 4x4.

 

9) SPEED KILLS

No matter what the terrain type, never drive a deflated tire at speed, doing so will cause heat build up, irreparable damage, and ultimate tire failure.

 

10) GRAVEL TRAVEL

A small decrease in tire pressure will dramatically improve your vehicle’s gravel-driving performance and road comfort – especially over corrugations.

 

Analogue tire pressure gauge deflation

Be sure to use a high-quality tire pressure gauge. An inaccurate gauge can do more harm than good.

 

11) TURNING BLUE

If your deflated tires take on a blue-ish tone, chances are they’re under-inflated and overheating. Reduce your speed, or re-inflate a bit.

 

12) OVER THE TOP 

Always drive OVER sharp obstacles rather than trying to squeeze around them. The tread is the strongest part of a tire, and it can also be repaired when damaged. In contrast, the sidewall is a tire’s weakest and most vulnerable area, and it can’t be repaired. If in doubt, drive over, not around.

 

Cooper S/T Maxx driving over sharp rocks

The tread belt is a tire’s strongest part. Try to avoid sidewall contact as much as possible when driving through loose rocks.

 

13) IT’S ABOUT LENGTH, NOT WIDTH

The performance advantage of deflating one’s tires is linked to an increase in tread length – as the tire deflates – and not tread width.

4x4 tire tread pattern in sand

When deflating, you want the tire’s tread length to “stretch” out, and not bulge at the sidewall.

 

14) TIRE CONSTRUCTION

Tire construction greatly influences how a tire will react to deflation. Some tyres use a robust carcass that requires additional deflation in order to achieve the same “stretched-out” result. What’s more, a road-biased H/T tire with a 2-ply sidewall rating will require less deflating than an A/T or M/T tire with 3-ply sidewall.

 

15) APPROXIMATE DEFLATION GUIDE

Bitumen: 100% (Manufacturer’s recommendation)

Gravel: 10 – 15%

Corrugated dirt tracks: 10 – 15%

Sharp rocks: 10 – 15%

Smooth rocks: 20 – 50%

Mud: 25%

Sand: 50 – 60%

 

Original published here.

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