ASK ARB – Air
Locker vs LSDs

Hi,
In the article ‘To Locker or Not to Locker’, Ian Bellert makes the following statement: “The factory limited slip differentials tend to do exactly what you don’t want them to – throw power across to the wheel that is spinning and has no grip.”
This is fundamentally wrong. An open differential will throw power to the spinning wheel. A limited slip differential (by definition) limits the slip of the spinning wheel and moves power to the wheel that has traction. A locked one will move 50% of the power to the wheel with traction, but a limited slip differential is a lot better than an open differential.
There were plenty of things that Ian could have done before it got to tears in the car. 20 PSI is way too high for trying to climb slippery mud. If Ian had dropped the pressure to between 5 and 7 PSI, he could have carefully driven straight up the hill with full traction and no tears. You can’t easily run 5 PSI in sand, because you need speed, but you can do it in mud, where you can crawl up a hill. Letting tyres right down is something that people need to know is an easy option in these kinds of situations.
Kind regards,
Stu

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Hello Stu, and many thanks for questioning Ian’s opinions on limited slip differentials. First up, I should tell you a little more about Ian’s background. Blerto, as he is better known to his mates, has been in the media for many years working on a variety of publications. He is best known to ARB through his time with 4×4 Australia Magazine & Australian Geographic.
I asked Blerto to write the article for us when I found out he had fitted a locker to his Navara. I knew that none of his previous vehicles were equipped with lockers, so I was really interested to see what made him fit one to his latest fourby.
In theory, what you say about LSDs is quite correct. However, in practice, Ian is absolutely spot on in his observations. When I used to work in sales, we would regularly demonstrate the ineffectiveness of LSDs to customers in the car park. We used to jack up one rear wheel an inch off the ground and then try to drive off the jack. Customers used to be gobsmacked when their LSD equipped 4X4 sat there motionless on the jack, with one wheel spinning.
But you don’t need to take our word for it. The team at Australian 4WD Action, filmed a video a while back on traction aids. They took three Toyota LandCruiser Prados, one equipped with an LSD, another with traction control, and the third with Air Lockers. This video clearly illustrates how ineffective LSDs are in mildly challenging off road terrain. You can check out the video at www.youtube.com/ARB4WD. It’s called Air Locker vs LSD vs traction control and is split into two parts.
With regard to your comments on tyre pressures, whilst what you say may be acceptable practice for a competition truck equipped with bead locks, I believe these pressures would be inappropriate for a typical family touring wagon running all terrain type tyres. However, given I am not an expert on tyres, I sought the opinion of someone who is.

This is the reply from Steve Vickers, the National Sales Manager for Exclusive Tyres, the Australian distributor for Cooper Tyres & Mickey Thompson:

“5 PSI is too low for a family touring wagon running all terrain type tyres without bead locks! On sand I would always start at about 22 PSI, come down to 18 PSI and then 14 PSI if I had to get out. I would be hesitant of going below that. 5 PSI would be an absolute extreme measure to get out of a sticky situation such as an incoming tide. If this was the case then pressures should be immediately brought up to a safe level afterwards because at 5 PSI there is a very real danger of building up too much heat in the tyre and having a major failure or rolling the tyre off the rim causing a roll over at speed.Even in the mud this is excessively low without bead locks, as with the sand, you run the danger of rolling the tyre off the rim and/or getting mud, sand, dirt and/or grit in between the bead and the rim. If you were to run this pressure it would be imperative to have the tyres stripped and cleaned to avoid damage later on. Of course, whenever you alter tyre pressures to suit off road terrain, it is absolutely essential that you immediately inflate the tyres back to road pressures once you hit the bitumen.”
In summary Stu, there are always other options to get out of a tricky situation. But none are safer, quicker, easier and more controlled than using Air Lockers.
Regards,
Matt Frost
(Marketing Manager)