Stretch Limos

June 11, 2007 at 8:02 am 1 comment

Makes you feel envious as they glide by, does it? It shouldn’t- just console yourself that they wear out their front tyres much faster then the long wheel base Fairlane or Mercedes that they were derived from.

You see, a car turns in a circle round an imaginary point some distance out from the side of the car. The rear wheels track following the fronts, the outer wheel on the circle travelling further than the inside wheel. The differential takes care of the difference. The front wheels behave differently. The inside front wheel turns in a tighter circle than the outside, because it is closer to the imaginary point, the “centre’ of the turn. The angle of the outer wheel is not as acute, because it travels in a wider circle. It’s 2 metres or so further away because of the width of the vehicle.

Now when the vehicle modifiers stitch in another two metres or so of bodywork, and a longer tailshaft and underpinnings, the relationship of the front wheels to this imaginary point is affected. The front wheel angles no longer match the designer’s intentions, and so the tyres “scrub” in ways that were never intended. They wear out fast.

This is why your front end mechanic doing an alignment checks the “toe out on turns” at full lock, to check that nothing has been bent. The steer angles of inside and outside are different at full lock.

limos and tyres

If you wish to see the differing angles, look at the front wheels of a forward control vehicle like a Toyota Hi-Ace, or a vehicle with the ability to do really tight turns. And if you customarily do very tight turns, such as garbage trucks manouvering, or hooning around the inside lane at roundabouts, then you have joined the stretch limo brigade, wearing out your tyres faster, because the imaginary point is now much closer than the designer engineer accommodated in his design.

Entry filed under: Tyre safety & maintenance, Tyre Technology, When to Replace your Tyres. Tags: , , , .

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1 Comment Add your own

  • 1. Cars for Stars  |  September 12, 2007 at 2:03 pm

    This is a very valid point and we should know!

    Reply

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