[importsmasher]

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

[Trevor78]

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.

[SS-TA]

An F60-15 is approximately 26 inches tall a 235 60- 15 is the closest current size.

[78w72]

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.

[72projectbird]

Run a 225/70 or a 255/60.

[Formulabruce]

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.

[78w72]

Originally Posted by Formulabruce

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.

225/70/15 tires are 27.4" tall, not 26.2.

[Formulabruce]

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.

[78w72]

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.

[importsmasher]

Originally Posted by Formulabruce

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.

Does this hold true if it has the ride and handling package (the Trans Am suspension)? I always thought that option got you 15 inch wheels. Am I wrong?

Thanks,
Importsmasher

[johnta1]

The Formula Handling Package came with the 15" wheels (plus other things)
F60-15 or G70-15

[Formulabruce]

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

[71GP76TA]

P245/60R15

[importsmasher]

Originally Posted by Formulabruce

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

Ok that agrees with my understanding. My car has the Y99 option, and no other mention of wheels on the PHS, so I believe that means I should have 15x7 body colored wheels and dog dishes; is that correct? My uncle put honeycombs on it back in the 80s, but I like the dog dish look better.

Importsmasher

[grd777]

Originally Posted by 71GP76TA

P245/60R15

Attachment 617096

all 4

[Formulabruce]

Plain steels with no option chosen. Probably a 15x6 too if no tire specified.

[importsmasher]

Originally Posted by Formulabruce

Plain steels with no option chosen. Probably a 15x6 too if no tire specified.

Good to know, thanks! I hadn't thought about them being 15x6. Now to find some (15x6 orv 5x7) and hub caps!

Importsmasher

[Held for Ransom]

Stop the misinformation. "Steelies" were 15x7. What was the price on the Y99?
https://forums.maxperformanceinc.com...d.php?t=772622

[71GP76TA]

Originally Posted by grd777

all 4

Yes

[71GP76TA]

Originally Posted by importsmasher

Ok that agrees with my understanding. My car has the Y99 option, and no other mention of wheels on the PHS, so I believe that means I should have 15x7 body colored wheels and dog dishes; is that correct? My uncle put honeycombs on it back in the 80s, but I like the dog dish look better.

Importsmasher

Standard '73 Y99 came with 15x7 standard steel wheels with baby moon arrowhead caps. My car is a Y99 that came equipped as such..

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.