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

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smbrm1
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Re: Did the 1976 cars all have the same diameter front wheel

Post by smbrm1 »

I would “think“ a bigger wheel could have a bigger diameter tire. Reason is that Firestone had an issue in early 70’s like 71(I think) when they went to lower profile on fronts. Drivers were experiencing excessive tire vibration. It may have been linked to wider rear tires as well. As we know today, there is a lot of spring from the tires(side wall height and stiffness, pressure) that is balanced with suspension springs. If the tyre diameter stayed the same on the fronts with a bigger wheel, it would obviously be lower profile. This would have to be factored into the design depending on the goals of the change. Tyre wars were changing things quickly in the early 70’s between Goodyear and Firestone, and later in the 80’s with Goodyear and Michelin. Who knows how exactly they were exploring the variables and rules of each period. Tyre sidewall height is considerably higher on a Brabham BT50 compared to the M23 even though the front wheel size is the same. The difference is reflected in their respective Tamiya kits.
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Re: Did the 1976 cars all have the same diameter front wheel

Post by JamesB »

smbrm1 wrote: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.
Stephen
First of all sorry, Stephen!! :oops: I read you bad, actually I understood you meant there were NOT changes (triggered or not by rules) on outer size, when you actually said YES! :lol:
then I fully agree, sorry! 8)
Yes, it's well known that 15" were extensively used in latter half of 1980, as a solution to front tyre overheating. Bigger size (yes!!) meant lower rotation speed, and less wear (or so they thought). Most of teams kept them, though some, namely Brabham, stuck to 13": if a car designed for 13 goes better with 15, it's bad designed" G.Murray dixit.
15", almost always just at front were kept for 1981, mixed with 13.
1982 would see 15" extensively used, even Williams used them at the rear.
Same story for 1983 and then suddenly they disappeared in 1984. Maybe the dawn of radials for eveyone, including GY, had something to do.
you can check for yourselves on pics, the difference is quite visible.
Generally speaking, they were overall bigger in 1980 and 81. But somehow manufacturers saw the benefits of bigger overall diamter, as well as almost identical diameter front/rear as soon as 1982 (believe me, I spent hours checking for the 126C2 tyres) and thus 15" wheels have a clearly smaller sidewall, to keep almost identical overall size... because 13" fronts grew. Meanwhile, rears kept getting smaller. Compare 1980 and 1981 pics. Rear views are quite useful as you can compare with wing width that stays unaltered.
Ah! and yes, Tamiya nailed BT50's fronts size, but were lazy on their rears, keeping those oversized balloons...
All ths is easy to check: see 126C2 pics where you'll notice thin wall on the S Marino pics, big wall on S Africa 13s...
hope this helps
J
er... anyway, if you are making the 1976 Shadow, let's not lose focus. Absolutely NO 15" rims. Sometimes the thinner sidewall (specially if pic does not show rear wheels to compare) may make us think of bigger rims, but surely not :D
I'll take a look at available pics... should be easy to say tyre size, as rim is a well known size.
BTW I just checked: M23, bt46b and Shadow all have same front tyre, smaller than FW07 and that's correct... maybe some M23 units hae bigger, unaccurate tyres.
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Re: Did the 1976 cars all have the same diameter front wheel

Post by Tyrone »

JamesB wrote: er... anyway, if you are making the 1976 Shadow, let's not lose focus. Absolutely NO 15" rims. Sometimes the thinner sidewall (specially if pic does not show rear wheels to compare) may make us think of bigger rims, but surely not :D
I'll take a look at available pics... should be easy to say tyre size, as rim is a well known size.
BTW I just checked: M23, bt46b and Shadow all have same front tyre, smaller than FW07 and that's correct... maybe some M23 units hae bigger, unaccurate tyres.
Hi James,

That'd be great if you could look into it, but seems likely I'll just go with the M23 front wheel assembly at this point as sourcing a different size (if that would be necessary) might prove to be a challenge.
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Re: Did the 1976 cars all have the same diameter front wheel

Post by Icon_Modeler »

Tyrone,

I can sell you the perfect set of tires for your build but I think you already have everything you need inside of the M23 kit.

Stephen,

Sorry, even though you are a wealth of knowledge I believe you have done nothing but made things confusing. The question was a simple one regarding the 1976 season. No need to start quoting years that have nothing to do with 1976.

As has been pointed out every car from 1976 raced on 13 inch dia wheels, front and rear. end of discussion, those are the facts. Though I'm still wondering why a BT46B has been brought up since that car didn't see the race circuit until 1978 two years after the season in question.
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Re: Did the 1976 cars all have the same diameter front wheel

Post by JamesB »

Icon_Modeler wrote:Though I'm still wondering why a BT46B has been brought up since that car didn't see the race circuit until 1978 two years after the season in question.
That was me, Derek!!!! :lol: :lol: :lol:
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Re: Did the 1976 cars all have the same diameter front wheel

Post by steveracer »

This is a fascinating subject.

Regarding the wheels, I believe the Shadow used round hole wheels wile McLaren used the 4 spoke wheels? Is this correct as I am going only from memory.
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Re: Did the 1976 cars all have the same diameter front wheel

Post by Tyrone »

steveracer wrote:This is a fascinating subject.

Regarding the wheels, I believe the Shadow used round hole wheels wile McLaren used the 4 spoke wheels? Is this correct as I am going only from memory.
You are correct! I'm debating trying to make my own wheels, or just sand down some from a Fujimi Brabham, it's the tyre size that was the main issue. I'm not building a particular race version so details don't matter 'too' much - I just want to get the overall look of the car correct.
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Re: Did the 1976 cars all have the same diameter front wheel

Post by JamesB »

hi Tyrone. I am almost sure that I have a pair of WM wheels like that. I might replicate them for you, though it wont happen before 10 days or so...
ah! checked period pics (stay away from restored cars); 27 or 27mm tyres are the thing to use.
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Re: Did the 1976 cars all have the same diameter front wheel

Post by Tyrone »

JamesB wrote:hi Tyrone. I am almost sure that I have a pair of WM wheels like that. I might replicate them for you, though it wont happen before 10 days or so...
ah! checked period pics (stay away from restored cars); 27 or 27mm tyres are the thing to use.
Hi James,

If you could make me a copy of those wheels that'd be great! please PM me any costs etc.

I've just popped the thinner tires onto some Brabham wheels. And it looks okay - seems other modelers have done this in the past too.
Image
Image
And here's my mock up - ignore literally everything it's very early stages!
Image
Image

So yeah if you could source me some of the more period correct wheels that would be fantastic :D
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Re: Did the 1976 cars all have the same diameter front wheel

Post by JamesB »

Buuuut.... these rims are perfect, really spot on, right?
you only have to finish the holes. But design is accurate.
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