Monday, 30 April 2012

wheels (and metals and tyres)

Recently a mate of mine showed me a picture he'd taken of one of his wheels on his car which had failed (broken) hitting a pothole.

This sort of highlights to me why for ordinary cars (not race cars on tracks) we benefit from lower priced but less "glamorous" steel wheels and tyres of more ordinary profile.

There is a common belief that mags are somehow stronger than steels, with some web pages (written by people who probably don't have any qualifications other than in "cut and paste" research) outlining why mags are tougher. This is only true in a narrow view of the world: the racing world. Certainly the wheel shops are happy to propagate this view.

In racing mags are chosen because for the same mass they can be made to have stronger torsional rigidity, and for less weight they can be strong enough for cornering and breaking.This helps when you are trying to get the best handling (and 100ths of a second matter) by reducing the unsprung mass of the wheels (allowing suspension to work better).

Lighter maybe, but they shatter on impacts.

Normally most racetracks don't have potholes. Potholes are unfortunately common on the roads outside of the highways and high traffic areas, especially with all the rain we've been having this last couple of years.

Further low profile tyres may have less squirm in corners than regular profile tyres, but guess what? That extra baloon effect on regular tyres provides more give than low profile tyres, so saves your butt (and your wheel) when you hit a big pothole. Not only is the regular tyre is more likely to absorb impacts and not ruin your wheel (and your day) but will be far more informative as to low pressure. Running your tyres on too low a pressure will cause blowouts and make this sort of wheel shattering more likely. Because of the nature of low profiles you're not as likely to notice a tyre with lower pressure than normal because it can't 'sag' as much to show you.

Catastrophic failure of a mag wheel in a pothole in a corner (or even just the rough shoulder of the road) could cause you to loose control of your vehicle and end up.

My mate was lucky.

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