It’s an obvious thing, but not so obvious that I haven’t been caught twice in the last month. When buying a secondhand car, or just the secondhand tyres off a car, check every tyre!

To the latter first. Recently someone in the small town in which I live advertised the tyres from an EF Falcon. ‘Near new’ said the ad. Since at that time I still owned an EF Falcon, I rang up. The seller didn’t know the tyre size but dutifully went away and checked. The size was right, so I went off to inspect the tyres.

Much to my surprise, I found that the tyres – and wheels – were still on the car! A wagon, it had spun and hit a tree. The car was a write-off, but the owner was trying to recoup more than she’d have got from a wrecker. So, the tyres (and wheels) were for sale, as was the engine. Trouble is, she didn’t tell anyone that you’d have to get them off (the wheels) or out (the engine) on your own!

This flummoxed me a little, especially when I pointed out that if I took the wheels and tyres off the car, it’d be awfully hard to move around her steep, grassy backyard – that’s where the car was. So, I suggested, perhaps she should place the car where it would be easy to winch, wheel-less, onto a truck when it was time for the car to finally go. I looked at a couple of the tyres, saw the brand-new tread, and made an offer. She accepted, so I went off for my trolley jack.

It was only when I was taking off the wheels that I noticed that in fact only two tyres were near-new. The other pair was probably half worn. But it was too late to complain… I should have checked the tyres more carefully before making my offer…

And blow me down if the same thing didn’t nearly happen again! This time I was buying a complete car. With the incident of the Falcon tyres still very clear in my mind, I checked with more than usual care the tyres on the car I was buying – a Peugeot 405 SRDT. And, again, there was a surprise in store.

Incredibly, the sizes front and back didn’t match. Now that might not be a shock on a Porsche 911 but it certainly is on a Peugeot 405! The correct standard tyre size for the Pug is 185/65 14. But lo and behold, on the back were 185/70 tyres! I quizzed the owner and he waved away the problem with a sweep of his hand. But why were they different? Oh, he said indifferently, perhaps his son had been responsible for getting those put on the car…

So, as I said, always check all four tyres….

• » Comments (3)

When you were taught to drive I’d wager 10:1 that no-one ever said anything about left-foot braking. The left foot was for the clutch, or in an auto car, for bracing yourself when cornering. (The driving instructor never said anything about that either? Oh well.)

I first started left-foot braking about 15 years ago. After reading a story on RWD handling that described left-foot braking, I decided to have a go. The first thing that I found was that after years of accelerator operation, my right foot had developed a super sensitivity – but my left foot was used to only operating the clutch. Left foot braking therefore resulted in a crick in the neck, until I learnt some sensitivity with that foot as well!

The worth was proved when I found myself pedalling a loan car, one that handled like it was shod with 75 series rubber pumped up to 20 psi.  The auto car had chronic understeer, but – much to my surprise – I found that it could be largely cancelled-out with a dab or two of left foot braking.

• » Continue reading or Comments (16)

I’d no sooner finished writing A Disappearing Suspension Technology than I came across something that goes a long way to explaining the reason that swing-arm suspension was used by such hugely respected engineers like Porsche and by companies like Mercedes.

The magazine article is on a very interesting car produced by one of the all-time greats in suspension theory. The designer of the car was Bill Milliken and the premise was that by using narrow tyres running a huge amount of negative camber, very good cornering grip would be able to be obtained.

Now there’s a lot more to his car than just that (by clicking on the magnifying glass you can enlarge the article scans enough to print/read them) but the narrow tyres/huge neg camber is a very short summary.

The tyres being used by Auto Union and Mercedes pre-WWII race cars were similar in width to current big motorcycle tyres and so would have been far less susceptible to loss of grip through lifting of the flat tread of the tyre that would otherwise occur through negative camber. In fact, the lateral thrust from the camber achieved by the swing-arms would, as the Milliken car shows, have made a major contribution to cornering grip.

It makes me think that a lightweight car running low pivot point swing-arm (or semi-trailing or leading) suspension and motorcycle tyres could develop a lot of grip while maintaining an ultra lightweight suspension, in turn giving a very low unsprung weight and low total vehicle mass. And the narrow wheels and tyres would also give far lower rotating inertia, improving acceleration and braking still further…

• » Comments (5)