28 replies to this topic

[BRG]

There is much debate over the introduction of 18" wheels for F1 cars.  Many bemoan and question the change from the 13" wheel that has been used for so long.  Yet we in TNF know that it was never the case that larger sized wheels were not used.  The Maserati 250F used 16" or 17" wheels as did most of the other cars in the 1950s. 

 

13" wheels seem to have been the size of choice from the 1960s onwards (with the honourable exception of the Tyrrell P34 and its many 10" wheels) and at some point, it became a regulation.  I think that was well before the single or spec tyre came in which of course locked in the wheel size whether teams liked it or not. 

 

So what was the progress on wheel size?  Going back to the earliest days, wheels were much larger, being based on horse drawn technology.  They gradually shrunk but remained larger until the 1960s when both race and road cars seemed to favour the 13" size.  Since then, the introduction of low-profile road tyres has driven an increase in size to anything up to 20" or more, and a simlar process followed in racing, except good old F1 - the technological pinnacle supposedly - which stubbornly stuck to an increasingly outmoded small wheel, high-profile tyre combination.

 

Can anyone cast any light on this matter?  What were the drivers for the changes?

[Risil]

I don't know loads about this but I believe that many F1 designers in the 1990s and 2000s found the high sidewall profiles very useful from a vehicle dynamics perspective, doing a lot of the work of a suspension while allowing the actual suspension to be as stiff as possible. I think when Michelin were looking at coming back in about a decade ago, Dieter Rencken wrote something about how the desire for 18'' rims was a sticking point as the teams didn't want to redesign their suspensions. 

[Michael Ferner]

When I was a wee lad, 15 inches was the norm. Ligier once famously went for 13 inch fronts and was decisively beaten by Williams for that.

[BRG]

When I was a wee lad, 15 inches was the norm. Ligier once famously went for 13 inch fronts and was decisively beaten by Williams for that.

Looking at technical specs for different cars, the wheel size is rarely mentioned.  So you imply WIlliams were on 15"s?  When would that have been?

[Charlieman]

One of the initial reasons for low profile tyres was to accommodate a bigger brake disc in a bigger wheel without needing a bigger wheel arch. Think of Porsche 911 racers in the 1970s and the Carreras running with 917 derived brakes. Once noted as useful for sports racing cars, low profile tyres found a place with road cars. Note that brake disc diameter in F1 is limited to 278mm since 1998.

 

For single seaters and cars like them (Can Am) with low profile tyres and smaller wheels, a reason might be aerodynamic -- smaller frontal area or reduced rotational air effects.

 

The downside, mentioned in some of the discussions about the F1 change, is reduced vertical spring effect -- with a low profile tyre, the sidewall has to be stiffer to reduce deflection, meaning that the suspension does more spring/damper work*. There is also a lateral spring/damper or deflection effect which I don't understand. This change may shake up the F1 team rankings when they first test their cars, but they'll soon work it out.

 

Would I buy a second hand road car fitted with non-standard wheels and low profile tyres? Unlikely.

 

* Crude control or dynamics definition: A spring determines distance of deflection and a damper moderates velocity.

[Michael Ferner]

Looking at technical specs for different cars, the wheel size is rarely mentioned.  So you imply WIlliams were on 15"s?  When would that have been?

 

1980 French GP. But it seems my memory let me down , 13 inches were the norm and Williams used the 15s to catch Ligier by surprise, and it worked!

[Allan Lupton]

Not racing cars but both my 1938 Lea-Francis and my 2016 BMW road cars are on 17" wheels - the wheel sizes were reducing in 1938 and later but started increasing from about 1960. Tyre profiles are a very different story.

To be more on topic, if we had a Formula 1 that allowed diversity, the car designers could take advantage of what the tyre manufacturers offered, much as the road car designers can. We could then have a tyre that lasted full race distance so did not have to be changed every 20-odd laps.

[AJCee]

1980 French GP. But it seems my memory let me down , 13 inches were the norm and Williams used the 15s to catch Ligier by surprise, and it worked!

Yes, 1980, and possibly 1979 too (can’t check right now) there were changes in front wheel size. Liger went through that period mid season in 1980 where it wasn’t the size of their wheels that was the problem but the weakness of the rims.

[Charlieman]

Some useful comments about wheel and tyre sizes on pre-war GP cars:

https://forums.autos...and-tyre-sizes/

 

Whatever the aspect ratio, you have to give serious thought to mass, rotational inertia, gyroscopic effects and tread velocity. I find the thoughts terrifying as well as serious. In the case of a land speed record car, the tyre designers have to come up with a construction appropriate for the power covered with just enough rubber to last the run.

[Sterzo]

If we go back to the fifties and earlier, tyre technology limited the range of profiles possible, so wheel sizes were chosen based on the desired overall diameter. Coping with bumps was always a consideration, plus wear on the driven rear tyres. Those considerations no longer determine anything when standard tyres are mandated, and it's possible to make strong tyres with a huge range of profiles.

[Michael Ferner]

As an aside, why do people always say and write "back to the future" when they mean "forward to the past"?  Is that Hollywood over mind? 

[Arjan de Roos]

As an aside, why do people always say and write "back to the future" when they mean "forward to the past"?  Is that Hollywood over mind? 

Lotus fans I guess.

[arttidesco]

 

IIRC Williams ....

 

 

.... and Ligier tried 13 and 15 inch front rims, I believe 15'' pictured in both cases, during practice for the 1980 British GP not sure what they selected to use in the race.....

[sabrejet]

Yet we in TNF know that it was never the case that larger sized wheels were not used.

 

That phrase makes my head hurt...

[BRG]

As an aside, why do people always say and write "back to the future" when they mean "forward to the past"?  Is that Hollywood over mind? 

 

Lotus fans I guess.

De Lorean fans, surely?  Even if that POS was partly engineered by Lotus.

 

That phrase makes my head hurt...

A double negative a day keeps the doctor away...

[Ross Stonefeld]

I don't know loads about this but I believe that many F1 designers in the 1990s and 2000s found the high sidewall profiles very useful from a vehicle dynamics perspective, doing a lot of the work of a suspension while allowing the actual suspension to be as stiff as possible. 

 

This never made sense to me because the tire deflection and stiffness rate can't be controlled, whereas suspension can? You can adjust with pressure, but that then messes up your contact patch and your chasing your tail like any setup change really.

[chr1s]

I thought the main reason some teams switched  to 15" rims was so that you could fit a larger brake disc?

[Lee Nicolle]

Effff wun. The so clled pinnacle yet are years and or decades behind. Near every high powered category world wide have been on at least 15" wheels for a long time. Road cars as well. But they have stuck with their tiny little wheels and brakes.

I believe in the 70s they used both 15 and 13" wheels. 5000s did and AFAIK they used F1 tyres.

[john aston]

So what ? Honestly, I doubt if the most of the viewing public has any idea  of the wheel size of an F1 car and I suspect it would  be a shock to them if they learned that F1 cars don't even have the ABS their family run around has had for years. I am assuming the change to 18s is purely aesthetic? God forbid it enables even more effective brakes. 

[PayasYouRace]

God forbid it enables even more effective brakes.

I don’t think they’re going to allow larger brakes. As it is, there’s a natural limit on the effectiveness of brakes and it’s the tyre grip. Once the brakes are strong enough overcome the tyre grip and lock the wheel, there’s no point in going further.

[BRG]

What wheel size was common through the 1.5 litre era?  I am inclined to think they were mostly on 15" wheels but have seen nothing to support that.

[68targa]

It seems 15" were used by most from 1961 but from 1964 Lotus with the 33 switched to 13" wheels.as did others.

[70JesperOH]

My quick fix for data on any historical racing car, including F1/GP cars, are http://www.dlg.speed...e/cars/cars.php

 

Jesper

Edited by 70JesperOH, 17 December 2021 - 14:30.

[Allen Brown]

Autocourse gave wheel diameters (as well as wheel rim widths - not to be confused).  In 1970, the first time I can see such a data table, it was all 13-inch fronts and 15-inch rears but McLaren had tried 15-inch fronts and Matra and BRM had tried 13-inch rears.  In 1971, all the fronts were 13-inch, and almost everyone had tried both 13 and 15 at the rear.  By 1973, they were all 13-inch front and rear, except that BRM, March and Surtees had also tried 15-inch rears, so a definite direction of travel by now.  In 1974, all 13-inch at the front except for Brabham who had tried 12-inch fronts, and about half the teams had also tried 15-inch at the rear.  Brabham had apparently tried 10-inch rears on the BT44!  I skipped ahead a few chapters and by the end of the decade it was all 13s front and rear.

[BRG]

Thank you Allen, that is very useful info.  I note you skirted round the P34! 

 

I find it hard to believe anyone would have tried 10" rears though - I mean, why would they? - is there any supporting info for that I wonder?

 

At some point, 13" became mandatory, I believe, and that was before the single tyre manufacturer era.  Can anyone recall when this was?

[RA2]

Sooner or later they are going realize that there is too much tyre. I hope they reduce it to 310 at all 4 corners just as in the WEC. I also hope FIA mandates a common supplier for WEC and F1.

[BRG]

Oh, I agree with that, definitely.  It is a long time ago now, but rim width limits came in for rallying.  There was much wailing and gnashing of teeth - I remember letters to Motoring News saying that 6" widths would be dangerous for powerful rally cars, ignoring the fact that a few years earlier a 6" wide wheel was seen as the maximum!  Of course it soon became accepted and nobody even thinks about it nowadays.  Less tyre means longer braking distance and more sliding in corners and requires more skill from drivers to manage the tyre and manage traction.  What's not to like!?

[Hati]

I don’t think they’re going to allow larger brakes. As it is, there’s a natural limit on the effectiveness of brakes and it’s the tyre grip. Once the brakes are strong enough overcome the tyre grip and lock the wheel, there’s no point in going further.

With bigger brakes they could make them from different material, I would prefer brakes that are as powerful as now but harder to get optimal result.

[RA2]

I guess FOM sent the same memo to Pirelli to make tyres that last only a few laps and driving to a delta is best for the show.