Did the 1976 cars all have the same diameter front wheels?

[Tyrone]

Hi, I'm in the progress of test fitting for my 1976 shadow build (WIP coming soon once my 2019 McLaren is finished) - I wasn't able to get a shadow kit, but will be using a tamiya M23 as a source for the DFV and tyres, steering wheel etc, all the little details.

The one thing I'm stuck on is that the front wheels on the shadow, look to be smaller than the McLaren and have higher profile tyres, but other photos it looks like they are the same,

Does anybody have any more information as to the tyre sizes from the 1976 season, and would the McLaren front tyres be suitable to use for my Shadow DN5?

Thanks!
Tyrone.

[smbrm1]

There is a reference in Scale Models (MAP hobby magazine) February 1975 AVS Shadow DN3 article(page 82-85)which says: “The wheels are fabricated magnesium, 13 in. diameter by 11 in. at front, 13x17 in. at rear. Alternative sized front wheels, 12 in.x10 in. were fitted when the newest sized low profile Goodyear types became available”

[Icon_Modeler]

I've never heard or seen anything regarding a 12" X 10" wheel but I'm not disputing its existence. As far as I know all cars from the 70 era used the same 13 inch diameter tires until they started developing ground effect cars in 78 and 79. It was then that we started to see taller front tires. All Tamiya kits from the 70's used the same tires all around. Iritani when he developed his kit of the DN5 it actually came with Tamiya parts as you have described using on your conversion complete with Tamiya tires so I suspect that the 13 inch tires depicted by Tamiya would be suitable for your build. Good Luck!!

[smbrm1]

I agree, it was my understanding that 13” wheels( with the exception of Tyrrell 6 wheeler fronts)were standard(at least for the rear) for quite some time, like from standardization in the early 70’s until when the new 18” wheel rule comes into play. My previous note was just what I read. I do recall that there have been changes in outer tyre diameter(larger) for fronts over time as well.

[Tyrone]

Okay guys, thanks for that - i'll just make life easier for myself and use the M23 front wheels. Look forward to the build post!

[JamesB]

I agree with all fellows' very sound contributions. just disagree a bit with smbrm1 regarding outer tyre size rule limits. I remember having seen those, though generally they were overlooked till early 2000.
So I'll just add that tyres grew clearly between '75 and '76. Tamiya has a smaller front goodyear, as we have seen on the bt46b.
And then as someone that has looked every picture, tell that tyres appear bigger/smaller depending on speed/accelleration conditions. The spin centrifugate effect, you know.
Better way to evaluate tyre overall size is comparing on a good pic with a known measure: front wing width, 150cm, is really handy, as is rim diameter, 17.8mm at 1/20th...

[Tyrone]

I agree with all fellows' very sound contributions. just disagree a bit with smbrm1 regarding outer tyre size rule limits. I remember having seen those, though generally they were overlooked till early 2000.
So I'll just add that tyres grew clearly between '75 and '76. Tamiya has a smaller front goodyear, as we have seen on the bt46b.
And then as someone that has looked every picture, tell that tyres appear bigger/smaller depending on speed/accelleration conditions. The spin centrifugate effect, you know.
Better way to evaluate tyre overall size is comparing on a good pic with a known measure: front wing width, 150cm, is really handy, as is rim diameter, 17.8mm at 1/20th...

Hi James, thanks for your imput!

Well you've certainly confused matters as i've just checked - and your are correct! the tyres in the BT46 Tamiya kit are considerably smaller than the ones used on the same scale M23. Hmmmmm.

Maybe using a set of those would be more accurate?

The 3D Models im using for reference aren't the best quality - but the wheel size of the 1975 earl 76 version I am building (on the right) is significantly smaller than those of the car for the following year (on the left). As I say this may be down to the model quality, or did the shadow indeed have smaller front wheels? so many questions!

[stubeck]

I agree with all fellows' very sound contributions. just disagree a bit with smbrm1 regarding outer tyre size rule limits. I remember having seen those, though generally they were overlooked till early 2000.

The specific change made in 2003 was from measuring the tire from seam to seam before the tire was run, to measuring it after it was run. This caused a rethink on the Michelin side as their tires were on the limit of the regulation and Bridgestone wasn't.

[smbrm1]

I agree with all fellows' very sound contributions. just disagree a bit with smbrm1 regarding outer tyre size rule limits. I remember having seen those, though generally they were overlooked till early 2000.
So I'll just add that tyres grew clearly between '75 and '76. Tamiya has a smaller front goodyear, as we have seen on the bt46b.
And then as someone that has looked every picture, tell that tyres appear bigger/smaller depending on speed/accelleration conditions. The spin centrifugate effect, you know.
Better way to evaluate tyre overall size is comparing on a good pic with a known measure: front wing width, 150cm, is really handy, as is rim diameter, 17.8mm at 1/20th...

Hey James, thanks for your comments. I don’t recall using the word “rules” or “limits” in my response, only making reference to the fact that tyre diameters changed.

I also found this reference: History of the Grand Prix Car 1965-85. Chapter 13, The Gordon Murray Championship Brabham, Page 110: “ Larger 15 in. front wheels and the big Monaco wing were used for Brands Hatch,...” {referring to the BT49 which used Michelin in 1980(?). There is a further quote: “ Both drivers preferred the smaller 13in. diameter front wheels.”

Grand Prix! Race by Race Account of Formula 1 World Championship motorsport racing, Mike Lang, 1980 XLII Grosser Preis vonDeutschland page 366, quotes {in the context of a rain situation} “For the Goodyear runners, in particular this brought real problems, as all of them were using the 15-inch diameter front tyres and some plumped for the narrower (16 -inch) rear tyres, whereas the only wet-weather covers available were of the older type, apart from a few 15-inch fronts. Consequently it meant that suspension settings had to be altered to accommodate them.”

Similarly Racer Magazine June 1980 quotes the use of 15-inch wheels( to accommodate bigger brakes) by Renault and the trying of 15-inch tyres by Goodyear Teams only to return to 13-inch tires. This reference being associated with the 1980 BELGIAN Grand Prix.

As always, details, details, details!

Stephen

[Tyrone]

Similarly Racer Magazine June 1980 quotes the use of 15-inch wheels( to accommodate bigger brakes) by Renault and the trying of 15-inch tyres by Goodyear Teams only to return to 13-inch tires. This reference being associated with the 1980 BELGIAN Grand Prix.

Stephen

Hi Stephen, in the case of switching rim sizes from 13 to 15" would the tyre be lower profile and the overall diameter of the tyre from outer edge to outer edge be the same between the two rim sizes? Is seems possible that they might have switched wheel sizes race by race in some cases, as I'm not building a particular race version the M23 tyres I have should at least not be 'wrong' entirely?