12 replies to this topic

[Jimisgod]

I always thought that it was beneficial for drivers to have the optimum possible grip so as to put down enough power and corner better, and that was achieved by wider tyres.

However looking at Lotus cars through the years, it took progressive widening with each successive Lotus model until about the 72 and 76 to make slick tyres as wide as they seem to get on the rear. Was it just that grip was served by grooves and the techniques to make wide slick tyres that could endure that speed did not exist at that time?

Why did cars from 1950 until the late 60s run thinner tyres is the basic question, however dumb it may be.

[Vitesse2]

Not really a stupid question. Twin rear rims were used in hillclimbs before WW2, although that may heve been more to get a faster start rather than for extra grip on the hill. A few drivers did also try them in racing, but generally only in wet conditions and the only circuit I know where they were used was Crystal Palace - notoriously slippery after rain. Parnell used twin rears in Swedish ice races in 1947, but I believe he was considered to be cheating - although mainly by his competitors who hadn't thought of it!

[Tim Murray]

My understanding is that it was known (as Richard illustrates) that more rubber on the road gave more grip. However, the tyre manufacturers then had to work out how to mould wider tyres so that the tread stayed flat when the tyre was inflated. Obviously this also involved running the tyres at much lower pressures than with the narrower tyres, so the technology of racing tyres had to be completely rethought. Here's an earlier thread on the subject:

Why were racing tyres so narrow in the 1950s and 1960s

It would appear that the wide tyre technology was first used in drag racing and eventually got to F1 via Indycar racing.

[kayemod]

One thing restricting tyre width was chassis rigidity, or rather the lack of it. With flexing cars, and more suspension movement needed for bumpier tracks, wider tyres wouldn't have helped cars much in the 50s & 60s. Stiffer monocoque chassis from the Lotus 25 onwards, better track surfaces and the 3 litre F1 of 1966, together with radials and advances in tyre technology, all mode wider tyres worthwhile.

[jgm]

Here are a few quotes from Setright's book 'The Grand Prix'.

'What was wanted (in the mid-60s) was a tyre that could put more rubber in contact with the road and keep it there with more uniform pressure over the whole contact area. At the same time it had to give if possible a higher cornering power and faster responses than existing tyres, and to have as much controllability, predictabilityand general progressiveness in its behaviour as drivers might require.'

'It was in pursuit of this theory that led to racing tyres becoming fatter and shallower in section over the years from 1957 to 1965.'

'Firestone... wanted every bit of rubber to be forced against the road to the same degree as every other bit of the contact patch: and the way to achieve this would be through a rectangular contact patch, in turn demanding that the tread be not convex but flat.'

'Yet there no satisfactory way of building a racing tyre of such a shape by conventional constructional methods. Making a flat tread by building up the shoulder would simply accelerate breakdown of the rubber through overheating...'

'It was while puzzling over this that Martin, of the Firestone Racing Division, came across a weird corn-harvester tyre that his firm had made back in 1934, a tyre with huge shoulders and a concave tread whose shape was echoed by its carcass. This was the first contour-moulded tyre, forced in the vulcanising press to adopt a shape quite different from the simple tubular one that seemed so natural. Thus was born the idea of the contour-moulded racing tyre: and it was an immediate success.'

[arttidesco]

I always thought that it was beneficial for drivers to have the optimum possible grip so as to put down enough power and corner better, and that was achieved by wider tyres.

I thought that until a friend of mine fitted Golf GTi Pirelli Wheels and tyres (P6's ?) to a humble Golf LX back in the early 1980's, driving the LX round corners with the wider low profile tyres did not instil any confidence at all, in fact the opposite the car felt strangely 'floaty' because the suspension was too soft for the amount of grip the tyres had to offer.

I suspect the enormous tyres of the mid 1970's would have been wasted on for example a Lotus 25 simply because the 25 had little to no aerodynamic down force to get the necessary heat into them, even if the necessary tyre technology had been rediscovered, as mentioned above, in the early sixties.

Edited by arttidesco, 16 September 2012 - 16:17.

[Jimisgod]

I thought that until a friend of mine fitted Golf GTi Pirelli Wheels and tyres (P6's ?) to a humble Golf LX back in the early 1980's, driving the LX round corners with the wider low profile tyres did not instil any confidence at all, in fact the opposite the car felt strangely 'floaty' because the suspension was too soft for the amount of grip the tyres had to offer.

I suspect the enormous tyres of the mid 1970's would have been wasted on for example a Lotus 25 simply because the 25 had little to no aerodynamic down force to get the necessary heat into them, even if the necessary tyre technology had been rediscovered, as mentioned above, in the early sixties.

Well, not enormous, but the 'Indy' Lotus 38 had fairly large rubbers. Did the relative speed of ovals get heat into them faster?



http://www.sportscar...rs-of-interest/

Edited by Jimisgod, 17 September 2012 - 17:34.

[Charlieman]

Well, not enormous, but the 'Indy' Lotus 38 had fairly large rubbers. Did the relative speed of ovals get heat into them faster?

When we think of a Lotus racing on ovals, we come up with Indianapolis which was fast, of course. But the Lotus 38 and similar cars raced on slower ovals, and there were different fast circuits (eg banked Monza) for other competitions. We really have to look at the car.

A tyre will get hot when it delivers torque and power between the track surface and chassis. The torque (assuming suspension that keeps wheels perpendicular to the road) depends mainly on the engine, partly on gearing, partly on brakes. Given that different engines (eg varying number of cylinders but roughly the same bhp) have different torque curves, we have to consider that different tyres may be required. The same car with a different engine may work better with different tyres.

Looking at contemporary prototype sports car racing, we have had a couple of manufacturers with turbo diesels who dominated Le Mans. They were manufacturer teams with full support from tyre companies, but their advantage over the "privateer" petrol engine teams may have been smaller if tyres had not been optimised for the diesels.

[David Wright]

Well, not enormous, but the 'Indy' Lotus 38 had fairly large rubbers. Did the relative speed of ovals get heat into them faster?

Yes, speed, combined with the extra vertical loading as the car (and hence tyre) is compressed into the banking, does result in more heat going into the tyre.

To quote Setright again - "One compound widely used in 1966 needed to reach 210 F for its properties to be fully developed, but seldom enjoyed better than 160 F in (F1) racing. Had this been rememdied more quickly than the intervening Atlantic made possible, Firestone tyres might have been less astonishingly hard wearing, but also more effective in adverse weather conditions." The Firestone tyre used in F1 in 1966 was based on Indy technology.

This also brings up the issue of compounds. Wider tyres enabled the use of softer compounds. The move from narrow high-profile hard-compound tyres to wide low-profile soft-compound tyres required development not only in suspension and tyre construction but also in compounds. When you look at the growth in tyre width say from 1960 to 1970 - progress was actually pretty rapid IMO.

Edited by David Wright, 18 September 2012 - 19:21.

[paulhooft]

For a long time I am searching for an article By Mickey Thompson.
He wrote somewhere in 1962-64?.
It is about what he called "The Racing Tyre of the Future".
I read a translation of it in the Dutch Autovisie or Auto Revue around that time..
Love to read this article again in Dutch, or to read the original American-English version.

Paul Hooft.

[Henri Greuter]

I always thought that it was beneficial for drivers to have the optimum possible grip so as to put down enough power and corner better, and that was achieved by wider tyres.

However looking at Lotus cars through the years, it took progressive widening with each successive Lotus model until about the 72 and 76 to make slick tyres as wide as they seem to get on the rear. Was it just that grip was served by grooves and the techniques to make wide slick tyres that could endure that speed did not exist at that time?

Why did cars from 1950 until the late 60s run thinner tyres is the basic question, however dumb it may be.

Strange story:

The powerful Novi Indycars (1946-1960) wore out tires so fast that, in order to reduce the wear on the rubber they ran on larger tires so that there was more area to share the load over in time. they used 18 and tried 20 inch tires while the opposition used 16 Inch. Less revolutions over a given distance for each wheel was believed to reduce the tire wear a bit....

It was only in 1963 when the Lotus Indycars required smaller tires 15 instead of 16 inch that Firestone decided to compensate for the smaller area by widening the rubber a bit to still get about the same area to unload all stress on as a 16 Inch had. And then they found out that because of the actual contact area of the tire with the track surface had increased the speeds went up. Somehow, no-one had ever envisioned that by increasing the width of the tire even more, it could make the cars go faster.
The roadster gang then insisted on getting wider 15 Inch tires as well, Firestone got into supply problems, AJ. Foyt and others called upon GoodYear to bring over their stock car tires and the tire war at indy had begun....

That is how it went at Indy....


Henri

[RonPohl]

And for that matter, why did intake so long for slicks to come to F1? It seems if the idea is maximum contact area between the Tire and road, the slick would be obvious on a dry clean track.

[D-Type]

And for that matter, why did intake so long for slicks to come to F1? It seems if the idea is maximum contact area between the Tire and road, the slick would be obvious on a dry clean track.

Discussed a while back, "Search BB" for "slicks" turns up several threads including this one

Like wider tyres, it all came down to tyre technology.