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#1
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73 Formula tire size
Can anyone tell me the correct tire size for my 73 Formula 400? I tried searching but only found people talking about bigger tire/wheel combos. My car has 15x7 honeycombs now, but originally had steelies and dog dishes. What would the correct tire size be, translated into modern tires (as much as I'd love repro bias plies, they're not in the budget)? 225/70-15? 235/60-15?
Thanks, Importsmasher
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Scott Baggiore 66 GTO convertible 389/4 speed (parents bought new) 73 Firebird Formula 400/4 speed 74 GTO 455/4 speed 74 Grand Am |
#2
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The R15 tyres at the time were F60 and GR70, which equate roughly to 215/60 R15 and 225/70 R15. The taller tyre look better in the giant wheel arches, the width still look a little lost inside them. The front is roughly 2 tyre sizes closer to the fender edge, as in, if you had 225 on front, then the equivalent tyre but 245 on the rear would have similar space to fender edge and not look front heavy. Depends what you are looking for, stock or just original style.
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#3
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An F60-15 is approximately 26 inches tall a 235 60- 15 is the closest current size.
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#4
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As mentioned, a taller tire to fill the wheel well or top of tire to underside of fender looks better on these cars IMO. A 26" tall tire looks way too short unless the car is lowered some or going for a 100% stock look.
The later years that use the radial tires got the tire height right for these cars, a 225/70 is ~27.4" tall and fills the wheel well nicely. the wider 60 series equivalent is a 255/60 at ~27" tall. |
#5
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Run a 225/70 or a 255/60.
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"Those poor souls have made the fatal mistake of surrounding us. Now we can fire in any direction" 1970 Trans Am RAIII 4 speed 1971 Trans Am 5.3 LM7 1977 Trans Am W72 Y82 1987 Grand National |
The Following 2 Users Say Thank You to 72projectbird For This Useful Post: | ||
#6
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Originally a 73 formy came stock with a 14" wheel and tire.
Options were RWL, WW, Black wall. Bias ply tires. Probably E or F. I think a 70 series was available. On the 14 inch rims, but on the 7 inch wide rims, not 6. 14, And 15 " tire choices are slim these days. 225/70 -15 radials are what they used stock on later second gen Formulas and Trans Ams and fill the wheel well at 26.2 inch.
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"The Future Belongs to those who are STILL Willing to get their Hands Dirty" .. my Grandfather |
#7
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225/70/15 tires are 27.4" tall, not 26.2.
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#8
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Charts do have the 225's at over 27, but in reality I have measured a few and all were around 26.5. I am sure each manufacturer is different too. Point is, its good size to fill wheel wells.
On 8 inch wide Snowflakes in 1978, they are shorter than on 7 inch Snow flakes in 77.
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"The Future Belongs to those who are STILL Willing to get their Hands Dirty" .. my Grandfather |
#9
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Agree that size fills the wheel well nicely and each brand will vary slightly, but for all the popular brands ive measured, they all come in within .25-.5" of the published specs, never saw one a full inch shorter, at least for the many sets of old & new BFGs, firestone indy 500/firehawk, M/T drag radials and quite a few other off brands over the years.
How they are measured can vary too as well as psi levels and rim size can give different results. |
#10
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Quote:
Thanks, Importsmasher
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Scott Baggiore 66 GTO convertible 389/4 speed (parents bought new) 73 Firebird Formula 400/4 speed 74 GTO 455/4 speed 74 Grand Am |
#11
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The Formula Handling Package came with the 15" wheels (plus other things)
F60-15 or G70-15
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John Wallace - johnta1 Pontiac Power RULES !!! www.wallaceracing.com Winner of Top Class at Pontiac Nationals, 2004 Cordova Winner of Quick 16 At Ames 2004 Pontiac Tripower Nats KRE's MR-1 - 1st 5 second Pontiac block ever! "Every man has a right to his own opinion, but no man has a right to be wrong in his facts." "People demand freedom of speech to make up for the freedom of thought which they avoid." – Socrates |
#12
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F-41 in 70, and Y99 in 71-3 had 15 inch wheels, however there was an upcharge not in the Y99 due to type of 15 ordered.
So wheels had their own line item, and could be ordered alone as well
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"The Future Belongs to those who are STILL Willing to get their Hands Dirty" .. my Grandfather |
#13
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Current Pontiacs - 1973 Formula SD455 - #'s auto orig paint 1972 Trans Am - 4 speed orig paint 1974 Formula 400 - Ram Air automatic 1966 2+2 convertible - 421 4bbl automatic 1967 Grand Prix - 4 speed orig paint 1967 GTO - 4 speed orig paint 35k orig miles |
#14
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Quote:
Importsmasher
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Scott Baggiore 66 GTO convertible 389/4 speed (parents bought new) 73 Firebird Formula 400/4 speed 74 GTO 455/4 speed 74 Grand Am |
#15
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Quote:
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#16
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Plain steels with no option chosen. Probably a 15x6 too if no tire specified.
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"The Future Belongs to those who are STILL Willing to get their Hands Dirty" .. my Grandfather |
#17
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Quote:
Importsmasher
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Scott Baggiore 66 GTO convertible 389/4 speed (parents bought new) 73 Firebird Formula 400/4 speed 74 GTO 455/4 speed 74 Grand Am |
#18
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Stop the misinformation. "Steelies" were 15x7. What was the price on the Y99?
https://forums.maxperformanceinc.com...d.php?t=772622
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So long, farewell. |
#19
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__________________
Current Pontiacs - 1973 Formula SD455 - #'s auto orig paint 1972 Trans Am - 4 speed orig paint 1974 Formula 400 - Ram Air automatic 1966 2+2 convertible - 421 4bbl automatic 1967 Grand Prix - 4 speed orig paint 1967 GTO - 4 speed orig paint 35k orig miles |
#20
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Quote:
Here's a pic running a 225/70R15 tire. My car came factory equipped with a GR70X15 tire. Needless to say... I prefer the 60's and the rallys.
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Current Pontiacs - 1973 Formula SD455 - #'s auto orig paint 1972 Trans Am - 4 speed orig paint 1974 Formula 400 - Ram Air automatic 1966 2+2 convertible - 421 4bbl automatic 1967 Grand Prix - 4 speed orig paint 1967 GTO - 4 speed orig paint 35k orig miles Last edited by 71GP76TA; 07-31-2023 at 07:50 PM. |
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