Equipment Tests > Under the Pump

The system equalises pressure on the tyres, or pair of tyres if it's set that way. However, if a vehicle is on a sideslope some CTI systems permit air to flow to the upside wheel. AIR CTI has special isolator to prevent this. The big worry for 4WDers is going to be, "I'd rip those hoses off where I go". Maybe, maybe not. Chet Cline, owner of AIR CTI is a keen offroader and doesn't have a problem with damage to the system, and neither do all the logging trucks that use it. You could always disconnect the short hose around the wheel itself and then reconnect it later on once you're through the tight bit.

So much for theory. To see how well it worked we took AIR CTI's Vitara for a test drive along some bitumen and dirt roads. Initially the pressures were set to highway (all of 20psi in the light Zook with oversize tyres) and when onto the dirt at speed the shortie felt, as you'd expect, skaty and nervous, needing judicious amounts of opposite lock around corners. Then I turned the control to deflate to 12psi, and I have to say it was an eerie sensation as with every corner I could feel the car become grippier and absorb rather than skip over the bumps. We all know the handling benefits of lower pressures on dirt, but feeling it as it happens was a first for me.

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Back on the bitumen with the tyres low the car felt soggy in the corners and wanted to understeer. Just a flick of the dial, back up to 20psi and it's a road car again. Absolute magic. And then we went for a play on Chet's private testing ground, with the pressures dropped down to 7psi, which allows the little Zook to pretty much climb walls. It's a great experience to be able to look at an obstacle and dial in exactly what pressure you want, and the effect is a more capable offroad vehicle.

After that experience we have to say this is one impressively useful device. The cost for the kit is around $2300 plus compressor, or fitted with everything it'll be $3000-$3500. The system can be installed to manage all four tyres at the same time, adjust individual tyres or split front/rear, which will be best for 4WDers. AIR CTIs plan to release an electronic display as an option to complement the analogue gauge, and it can warn if there is a pressure loss.

Now you could argue a CTI system isn't necessary, and you'd be right, in the same way that five-speed gearbox isn't necessary, and nor are variable-speed screenwipers. But necessary or not, once you've tried adapting the tyre pressures to the terrain as easily as we can change gear you realise it's not a gimmick, it's a bloody good idea.

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