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Getting a grip

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#1 Gary Davies

Gary Davies
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Posted 20 October 2001 - 10:44

The photograph of a hillclimbing Bugatti recently posted by Rainer brought to mind something about which I've wondered for many years.

Clearly, manufacturers/designers/tyre companies - whomever - came at some (pre-war) point to understand the advantages (Traction? Cornering speed?) of having a greater contact area through the driven wheels ... at least in respect of hillclimbing.

So the question is, how come narrow tyres were de rigeur so long in circuit racing?

Could not the Mercedes and Auto Union drivers during the 30's have used a bit more rubber to tame their cars' wayward tails? And might not the same be said of their brethren right throught to the end of 1960?

Sure the tyres gradually became wider but it seems to me the first tyres you could properly call doughnuts only showed up in 1967.

Was the tyre technology not there to build wide tyres during the thirties through to the sixties? Or did the penny not drop with designers?

Anyone know?



#2 BertlF

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Posted 20 October 2001 - 13:50

I think this has to do purely with tyre technology. I remeber having seen Auto Union's with double rear wheels as well to get more grip!

There are basically 2 technologies to produce a car tyre. Radial tyres are built by applying the differend layers radially to the circumference of the tyre. Today radial tyres are mainly used for trucks and heavy machinery. With this technology, the side flanks of the tyre has to be increased in a fixed ratio if the width of the tyre increases to maintain stability of the tyre. Just think of the relative 'high' tyre flanks of truck tyres in comparison to their width!

At diagonal tyres, the layers are applied diagonally. Diagonal tyres are the standard tyres in road cars today, however, until the late 1960's mainly radial tyres were used on road cars too! Until the late 1960's (I don't know the exact date), there were also only radial tyres in racing.

Would anybody know by whom resp. when the first diagonal tyre was used in racing?

I think it was Dunlop which started to experiment with diagonal tyres. With the diagonal technology and the introduction of inwoven steel threads in the layers, the stability of the tyre flank has been increased significantly, therefore the 'surface' of the tyre, which provides the road contact, could be increased in relation to the flank and the lateral stability of the tyre maintained.

When the engineers realised, that the spot, on which the tyre actually gets in contact with the road, defines the only point, where the most critical forces (acceleration, braking, lateral forces) between the car and the road are transmitted, the tyres became wider and wider to increase the possible transmission surface. (I think the maximum tyre with with slick tyres was in the early 1980's).

So, Auto Union, Mercedes etc. just didn't have the necessary tyre technology to use 'more rubber' to get into control of their 'wayward tails'...