11 replies to this topic

[Mohican]

Lots of excitement in F1 circles about the Lotus team testing 18 inch wheels and and low profile tyres at last week's Silverstone test.

Everybody involved with modern racing appears to have forgotten that F1 cars all ran with low profile tyres back in the early 70's; admittedly there was also a number of tyre related problems such as regular punctures, etc.
As a teenager, I remember watching the 1971 French GP at Paul Ricard; the first GP to be held there - and sadly Pedro Rodriguez' last F1 race. I particularly remember a shot of his retiring his BRM P160 - due to a flat rear tyre.

IIRC, the current 13 inch wheels with high sidewalls were introduced for safety reasons the following year; or at the latest in 1973.

What goes around, comes around - in every sense. Personally thought that the Lotus last week looked very good, although I realise that a switch would entail a number of design and engineering difficulties to do with the much stiffer tyre sidewalls.

[Lee Nicolle]

The tyres really have not got taller, just skinnier! The aspect ratio has come back quite a way.

[RJE]

I seem to recall that the low profile tyres of the early seventies among other problems caused the most awful vibration, enough to crack chassis and suspension components.  I believe that a lot of the flat tyres of the day were a result of the wheels and rims.

[Lee Nicolle]

While F1s used wider tyres than the smaller classes I used 10x23x13 M&H wets for rallycross in the 70s. They were listed as a Formula Atlantic rear and midget r/r. Back when life was simpler. We used similar size and spec Goodyears on a Speedway sedan I was involved with, they were cast offs from a Midget. FA front tyres were lower and not quite as wide.

F5000s would have used similar tyres to F1 at a guess. The rears they uses these days are smaller diameter, hence lower profile!

 

Though F1s with their skinny tall tyres really do look very dated.That and the mad boffins nightmare they call aero makes them rather weird looking cars. 

[BRG]

IIRC, the current 13 inch wheels with high sidewalls were introduced for safety reasons the following year; or at the latest in 1973.
 

Can anyone cast any light on this?  What sizes of wheel/tyre were used in the 1960s?  When were 13" wheels actually mandated in F1?  And what about other formulae of the time?

[charles r]

I seem to recall that the low profile tyres of the early seventies among other problems caused the most awful vibration, enough to crack chassis and suspension components.  I believe that a lot of the flat tyres of the day were a result of the wheels and rims.

Was this also the era of what Pete Lyons used to describe as the "Bronx cheer"?

[PeterElleray]

Can anyone cast any light on this?  What sizes of wheel/tyre were used in the 1960s?  When were 13" wheels actually mandated in F1?  And what about other formulae of the time?

Generally 15" diameter in the 1960's, certainly on the 3 litre cars, with front diameters around 23" rears around 24" by the end of the decade.

 

13" wheels were not mandated until the early 1980's. Several cars ran 15" fronts in 1980 at various venue's the Ligier's famously at Brands where they came to grief with related issues.

 

However, 13" wheels were essentially universal in F1 from the 1971 season, arriving at the same time as slicks, and continued to be  until the advent of skirted ground effect cars when the  loads  were liable to overload the low profile tyres, 

 

 

The front tyre diameter at that time was 20", increasing to 21" in 1978 at the request of Lotus, for the 78 , then 23" and then 25" as aero loads increased. the 15" fronts used in 1980 were an attempt to ,maintain aspect ratio with a larger diameter tyre , rim widths 10" nominal, 11" was also used and eventually 12" and above with ground effect.

 

13" diameter rear wheels were not as universal, 15" continuing until the withdrawal of Firestone in 1974 on some cars, both  Goodyear and Firestone equipped, but then  as sole supplier Goodyear standardized on 13" in 1975. Rims were 16" all the way up to 20"! Diameters started at 24", grew to 26" then 28" before falling back to 26" where they remained for many many years.

 

There was no mandated rim diameter throughout this time, just the defacto one described.

 

Given that to balance a race car you need the aerodynamic CP to be in a similar position to the vehicle CG i have often thought that mandating 20" front tyres, which could not tolerate huge aerodymamic loads, would be an interesting way to achieve a downforce reduction, as the rear would then have to be reduced in proportion, and both would need to respect the cars mechanical weight distribution.

 

Peter

[David Wright]

13" front wheels came in in 1969 on the Ferrari and Matra for example.  I think the main purpose was to reduce drag.  By 1970 they were pretty universal.

[PeterElleray]

13" front wheels came in in 1969 on the Ferrari and Matra for example.  I think the main purpose was to reduce drag.  By 1970 they were pretty universal.

Yes that's right - on the new cars introduced that year .

 

Some carry over cars from '69, and also  the new McLaren M14 continued on 15" fronts. Almost every car ran 15" rears that year.

 

You could still obtain the 15" fronts if you wanted in 1970 although all the development was going into the 13's,  By 1971 if you wanted to run 15's you would have had to look for new 'old stock' or to a tyre designed for a different formula (ie F5000).

 

I think the drag issue was one factor, another was the prevailing weight distribution which was biased to the rear. A recognition that the early 3 litre fronts were effectively oversized for the rears. With a rearwards bias in the mid 60 per pecent a smaller front could handle the load.

[BRG]

Thanks for all that.  Of course, we should recall that there were 10" front wheels on the Tyrell P34.

[PeterElleray]

Thanks for all that.  Of course, we should recall that there were 10" front wheels on the Tyrell P34.

and 12" on the Thompson indycars...

 

i think 12" fronts were also tested in F1 in the mid 70's by Brabham and others.

[doc knutsen]

Thanks for all that.  Of course, we should recall that there were 10" front wheels on the Tyrell P34.

 

13" wheels came in with the latest tyre developments for 1964. Dunlop pioneered the new wide "doughnut" tyres on 13" rims in F1.  When NGH crashed the first BRM P261 at Snetterton early in the spring, famously acquaplaning off, the brand new monocoque BRM was still fitted with 1963-spec 15" wheels.

When the Lotus 33 came out, it too featured 13" wheels, as did the BRMs and Brabhams, with much wider rims than those in use in 1962/1963. To my mind, the new 13" rims fitted to the 1964-spec BRMs were particularly attractive.

Later,  BRM would use 15" "spoked" alloy wheels, some times at the rear only, depending on  tyre suppliers, I seem to recall,  as much as anything else.  By 1970, brake technology had advanced sufficiently for adequate brakes to be housed inside 13" rims, despite DFV power. Rear brakes were often mounted inboard on contemporary Hewlands in the Sixties and Seventies, but mainly, I would think, for reasons of unsprung weight. A side effect would have been to get the gearbox oil up to temperature toot sweet

Edited by doc knutsen, 17 July 2014 - 15:32.