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Discussion Starter · #1 ·
Hi guys
I'm busy building some early '70's F1 cars. Mainly Classics shells which I hope to post once they get going properly. In the meantime i'm 'gathering materials' and am having trouble with tyres. This has probably been asked/answered before but all my searches (i've done a lot) come up with next to nothing.

We're talking 1970, 1971 and 1972. It seems to me that the F1 tyres changed size quite radically in that moment in history!!

I'm having difficulty finding a) the actual tyres used on any given car and
the slotcar equivalents.

So far I found that the 1972 Lotus 72 had the following:

Goodyear front - 9"/20" tyres on 10"/13" rims (always width/dimeter)
Goodyear rear - 14"/26" tyres on 17"/13" rims

That scales at 1/32 (in metric) to:

front - 7.2/15.9mm tyres on 7.9/10.3mm rims
rear - 11.1/20.6mm tyres on 13.5/10.3mm rims

Now the scaley McLaren tyres (around 1976) would fit the front but the rears are way too wide!!

I'd like alu/alloy/magn. rims to fit the tyres too. Sadly searching for these things on the usual websites is next to useless since the wheels and tyres rarely have the sizes. Its like people just know!!

So, what about 1970 and 1971? And which tyres should I be using?

HELP

Andi
 

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Hi Andi,
Penelope Pitlane have just recently released 2 new wheels which are aluminium replicas of the Scalextric wheels fitted to their 1970's F1 cars.
RSWS = Fronts
RSLW = Rears
Can't find them on the PP site but they are on the Pendle site in the Scratch Building Spares section.
Tyres to fit from RSSlotracing (Ortmanns)
37 = Front Slicks
36c = Rear Slicks
36a = Rear Ribbed
Not sure if they do ribbed fronts but if you call Colin I'm sure he will sort you with the right ones.
These are also replicas of the 1970's Scalextric F1 tyres as fitted to cars such as the Lotus 72 and Ferrari 312B,and up to the early 80's cars like the Williams FW07.
Almost all F1 cars ran on 13" wheels from about 1970. From 1976 until now only 13" wheels have been permitted.
Hope that helps.
Cheers.
****.
 

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Me again Andi,
Additional thoughts on suitable wheels and tyres.
Fronts:
The front wheels and tyres fitted to the Slot.It Ferrari 312PB and Alfa are about the right size.
Ally wheels - SIPA33als.
Tyres - SIPT20.
Rears:
Both Slot.It and NSR make wheels to take the tyres fitted to Ninco F1 cars.
Slot.It wheels - SIPA20als or mg
NSR wheels - 5005
You then have the choice of Ninco, Ortmann or NSR F1 rear tyres which will all fit either wheel.
Ninco - 80502
Ortmann - 49
NSR - 5220(Supergrip) or 5221(Ultragrip)
Cheers.
****.
 

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Discussion Starter · #5 ·
thanks for your feedback guys.....

There's a problem though. If I use Slot.it or NSR rims i'll end up with a vintage F1 car with modern touring or LeMans wheels. All those rims you've mentioned (except the old scaley one's of course) are much too large and the tyres are much too low profile.

In fact its EXACTLY what i've been finding myself with my research. Take those Slot.it rims SIPA20als for example. They are 12mm wide and 14.4mm dia. I need the opposite! 10.3mm dia. and 13.4mm wide!!!! Then high sided tyres to fit on them.....

I did see those ali scaley fitments on Pendle's site. Look good but again just a little too wide at the rear....

I've also written directly to Colin at RS to see what he can suggest as i'm sure his knowledge is unbeatable.......

Seems there's a business opportunity here for someone.......

Andi
 

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Slightly bizarre suggestion - but what about an insert that looks like a 13" rim inside a rubber sleeve, in a slot it wheel, I know what I mean but I don't know if anyone else will, you could use a old Scalextric wheel as an insert.

As mentioned above what about the Slot It Ferrari 312 PB wheels and inserts, didn't the 312 have F1 sized wheels?
 

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Hi Andi,
Sorry but you are making a very common mistake with your wheel diameter calculation.
A 13 inch wheel is 13 inches diameter on the bead. That is the area that the tyre sits on behind the rim.
The outer rim, which stops the tyre from coming off the wheel, will add about another 1.5 inches to the overall, visible diameter.
This means that the visible edge of a 13 inch wheel is actually more like 14.5 inches diameter.
What you actually need to represent a 13 inch wheel in 1/32 scale is a wheel of about 11.5mm diameter over the rim.
The Slot.It SIPA20 wheel is 14.4mm over the raised central ridge and about 12mm at the rim.
It's actually very close to a scale 13 inch wheel as it would be because the Ferrari 312PB and Alfa 33 did indeed race on Formula 1 sized wheels and tyres.
A 1/32 scale 10.3mm diameter wheel is a good representation of a 10 inch Mini wheel and way too small for a formula 1 car.
Cheers.
****.
 

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Discussion Starter · #8 ·
WOW ****, now I learnt something today!

Actually I did some calc's on that when i did the Vanwall and just completely forgot about all that..... Must be getting old.

OK, so what you're saying is that the rim diameter should indeed be about 11.5mm and indeed 12mm would therefore do.

Let me go back then and do some more research on what you're suggesting.

Cheers and thanks

Andi
 

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Hi Andi,
Just got home and measured some of these wheels.
Penelope Pitlane's new wheels are 11.55mm diameter over the rim.
Slot.It SIPA33 fronts are 12mm over the rim.
Slot.It and NSR F1 rears are about 12.2mm over the rim (it's a bit hard to measure mine accurately as they all have tyres glued on).
The wheels on your Brabham fan car look about the right diameter to me. What size are they?
Remember all F1 cars run on 13 inch wheels and have done since about 1970.
13 inch wheels were introduced in F1 about 1964 with the Dunlop Donut tyres.
Some teams went back to 15 inch wheels in the early 3 litre era (66-68) mainly with tyres based on the Firestone Indy track tyres but the idea didn't last long.
Cheers.
****.
 

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Hi, this may sound like a silly question, but does the width of the rear tyre quoted

Goodyear rear - 14"/26" tyres on 17"/13" rims

take in the tyre bulge?

Or is it just the width of the tyre surface, the part that touches the road?

There was some really big side wall bulge on the rear tyres of those 70's F1's.
 

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Discussion Starter · #11 ·
****

The Brabham uses Ostorero Lotus 79 tyres and rims. Good enough diameter but rather too wide.....

Were all the 1970-1972 tyres treaded / grooved. The NSR and Ninco tyres you uggested earlier are grooved. Honestly I was thinking slicks!!

Finally i've decided SlPA 33-als with SIPT 20 on the front as you suggested. For the rear i'm happy with the SIPA 20als but not entirely sure about which tyres to use. SIPT 20 are slick, are they not? What did the rears of the Ferrari 312PB look like? Too wide for me? I can't seem to find a reference as to what number they were?

QUOTE (Mirrorman @ 30 Jun 2011, 17:34) <{POST_SNAPBACK}>Hi, this may sound like a silly question, but does the width of the rear tyre quoted

Goodyear rear - 14"/26" tyres on 17"/13" rims

take in the tyre bulge?

Or is it just the width of the tyre surface, the part that touches the road?

There was some really big side wall bulge on the rear tyres of those 70's F1's.

Hi Mirrorman, I was wondering the same thing. The tyre is quoted as 3" thinner than the hub so i'm guessing that the tyre width must be only the part on the road as you say.....

Andi
 

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Hi Andi,
I'm afraid that the rear tyres for the Slot.It Ferrari 312PB and Alfa will be of no use to you because they used 15 inch wheels on the rear.
This was common in sports car racing at that time.
You may also find the odd example of Formula 1 cars running 13 inch fronts and 15 inch rears, but not many.
the Slot.It front tyres are indeed slicks.
Slick tyres first appeared in Formula 1 in 1971.
By 1972 they were universal.
If you use NSR tyres by the time you have trued them there will be very little tread left.
Cheers.
****.
 

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The quoted width doesn't deal with sidewall or overall width, or even the tread. As I understand it, the width quoted for tyres on full-sized cars is the width at the bead, inside the rim. In most cases, the tread width is about the same, but I don't think that is what is measured.
Actually, I thought wheel width was also measured at the tyre seat, but maybe the old mind is wandering (again).
Rob J
 

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QUOTE Hi, this may sound like a silly question, but does the width of the rear tyre quoted

Goodyear rear - 14"/26" tyres on 17"/13" rims

take in the tyre bulge?

Or is it just the width of the tyre surface, the part that touches the road?
OK.
Wheel width is quoted as the dimension between the rims.
The rims that retain the tyre on the wheel could be as much as 0.5 inches thick on a cast wheel.
So a 17 inch wheel will actually be closer to 18 inches wide measured over the full width.

The tyre measurements as quoted are:
14 inch is the width of wheel that the tyre is intended for.
They were often fitted onto wheels wider than they were designed for at that time.
Tyre treads were approximately equal to the wheel width.
The side wall bulge will make the overall width of the tyre much greater than this. Usually wider than the wheel used.
26 inch is the overall diameter of the tyre.
This dimension remained pretty constant through the years.
28 inch was the most common diameter through the 60's no matter which size wheel was used.
This dropped to 26 inch diameter in the early 70's with the trend to standard 13 inch wheels.
Cheers.
****.
 

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Just a follow-up to ****'s words for anyone with an anorak in the wardrobe, and summarising from Cimarosti's The Complete History of Grand Prix Motor Racing:
By 1969, 15in diam rear wheels, 13in front, were in common use with lower-profile tyres (height 0.4-0.4.5 of width) almost universal. "The norm for rim widths became 14-16in at the rear and 10-12in at the front."
By 1971, tyre width was about three times the height. To reduce air resistance still further, and to reduce unsprung weight, "many designers revised their idea of having 15in rear tyres and fitted 13in units instead."
So, 13in all round, at least from 1971.
In 1972, tyres became even wider, up to 18in on, for example, the Surtees TS9 rears. "The successful Lotus 72D was fitted with 9in wide tyres at the front and 14in... at the rear."
Doug Nye's book on the 1966-85 period says slicks were introduced by Goodyear at the South African GP at the beginning of 1971. "Firestone rapidly followed suit at the Spanish Grand Prix."
He says that very low profiles were adopted by Firestone in 1971-72, "but this led to severe vibration problems and Goodyear then knocked Firestone out of competition at the end of 1974".
He also describes taller profile tyres about then, based on dragster technology, which "engendered a wind-up effect which heated the tyre very effectively and gave terrific traction away from corners". It's not clear how long that trend lasted.
Have fun, Rob J
 

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Just remembered that Doug Nye's book on the 1966-85 grand prix cars has a chapter on the Lotus 72.
From that, it seems that Lotus generally stayed with 15in diam rears through the 1970-1972 seasons, though it sometimes used 13s.
The 72 began in 1970 with 49C wheel sizes: 13in diam x 10in wide fronts and 15x15in rears.
In the 1971 US GP Fittipaldi used 13in rears, at least in qualifying, though that must have been unusual for Nye to mention it.
For the 1972 season, the 72's "wheel diameters stabilized at 15in at the rear and 13in at the front..."
He doesn't specify 1973-75 sizes, but they probably changed to 13in diameter rears as Goodyear concentrated development on newer cars such as the McLaren M23 and others had to follow suit.
For 15in wheels in 1/32, the visible diameter would be about 13mm.
All this makes me think of digging out my old Motor Sport mags. Jenks, "Our European Correspondent", must have told us all.
Rob J
 

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Discussion Starter · #17 ·
One of the real problems is that for people like me who buy EVERYTHING mail order the websites selling stuff just don't give sufficient info.

What I need are detailed cross sections of all the wheels and tyres so I can see what I want and order.

I've been looking at pendle's site amongst others but have no clue what the dims really are and what goes with what????

And from the response to this thread i'd say that about 99.97% of forum users haven't either!!

Thanks to all who have offered advice and for the interesting history but i'm not that much closer really to finding the info I need......

Why are the history books so vague? Great that the '72 had 15" rears but what were the changes to the widths exactly over the years???? Nobody knows..... Or perhaps cares.....?

Thanks again

Andi
 

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Tony Condon
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Hi andi
personally i think you are worrying unnecesarily, in most cars i build the tyre sizes are laid down by the regulations so the decision on tyres is usually made by some one else
additionally those that aren,t building cars for competition ,are usually able to get the wheels right" by eye "
i am sure that with the modelling skills you have demonstrated on this forum you would be well able to do that
cheers tony
 

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Andi's original question reminded me that I have two Lotus 72 bodies to refit, a 1970 Rindt GLTL and a 1972 JPS, so my digging on wheels was for myself too. The GLTL is just a vac body, but it was one of my best painting efforts in the 1970s and deserves reasonable resurrection.
I won't attempt to go as far as Andi in authenticity (I like Tony's point), but I did look a little further and found a smack side-on photo of Fittipaldi's 1972 Monza-winning car that clears the mind after all those numbers. It clearly shows the rear wheel diameter was larger than the front, confirming the F 13", R 15" given by Nye. The caption points out the low-profile Firestone tyres that Lotus and a few other teams ran in 1971-72 for their stiff sidewalls. Their use explains the 15" wheels as opposed to the 13" that Cimarosti said many [other] teams were using by 1971. By an unscientific measurement on the photo, the visible sidewall height is 27% of the visible wheel diameter. Try that, Andi!
As for width (in effect the approx tread width), Cimarosti said F 9in, R 14in for the 72D - but no guarantees.
More accurate info and perhaps plans would be available in the history books, e.g. a book on the Lotus GP cars of the period or the 1972 Autocourse annual. I don't have either, but some folk have these to hand. The Autosport Nostalgia Forum is very useful. That's at http://forums.autosport.com/lofiversion/index.php/f10.html . Registering and putting a question is probably better than searching. Plenty of guys there are happy to dig out detailed info (and then argue over it - ask for their sources).
There may be a Lotus 1:1 enthusiasts' website with such info, though the only one I've bookmarked doesn't.
I know little of modern slot-car wheels, except that some on detailed replicas aren't accurate and I wouldn't rely on wheel sellers' scale sizes such as "15 inch". **** Kerr's formulae are more accurate.
BTW, the 1970 72's rear wheels appear to have been solid. Were the 1972 wheels solid or spoked? It's not clear in the photos I have.
Rob J
 

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QUOTE BTW, the 1970 72's rear wheels appear to have been solid. Were the 1972 wheels solid or spoked? It's not clear in the photos I have.
Hi Rob,
Solid wheel centres were very common in that period.
I can't remember the brand at this moment but we certainly used them on all the Surtees cars of the period.
Most cars at that time used inboard rear brakes so ventilation at the rear was not an issue.
Cheers.
****.
 
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