FIA Rims and Tire sizes, Resurrected Topic
 

FIA cars used 6.5 and 8.5 wheels, with 6.70x15 and 8.20x15 GY Speedway Special tires. When I research those sizes for old 'racing' tires, they come out narrower than 235-60 and 295-50 typical go-to sizing. They came out closer to a 215-70 and 255-60. I know the 6.00x15 and 7.00x15 GY Vintage Sports Car tires shows much wider, but there is no way those could fit properly on a 6.5/8.5 set-up. However, they do fit well on the 7.5"/9.5" set-up. What's the real story? does anyone have an early 60's race tire catalog?

Is 6.70 designation the tread width? meaning sidewall is around 8.5-9 in wide bias designs, perfect for 6.5" wheel.
Likewise, the 8.20 tread would have a sidewall around 10-11 in wide, perfect for an 8.5" wheel.

Just throwing it out there for continued discussion.

The point of this, is determining where to go on my Unique FIA. It has very old 245/60's and 275/50's on it. The unavailability of the 275-50's in a true matching DOT rated tire is the problem. The wheels are 8" and 8.5". A 295/50 is not going to fit well on the 8.5", and I cant go any further inboard because the wheel tire flange is right at the hub 'knuckle', about 1/2" away. The tire area has plenty of clearance inboard but the tire flange doesnt. So, the rear wheel size and position are set. A 255/60 is where I am, leaving a 235/60 up front. But I want a proper stance. So, the front needs to be a 6.5"-7" wheel. The tire choices there, for a proper fit is a 215/70 or 225/70 (too tall).
Both of these seem quite similar to the original FIA front 6.70x15 on a 6.5" wheel. I have seen some of the cars on here with 215/70 and 255/60, how do they handle and how do they look?

I have original Halibrand magnesium FIA wheels on my Cobra, 6.5” and 8.5”. I run 205 70 in the front and 245 60 in the rear. At one point I did run 215 70 in the front but the turn in was a lot quicker with the 205 70. I also only run AVON C6ZZ tires.

So, your confidence and selection makes much sense than just assuming the Goodyear 6.00x15 and 7.00x15 vintage sports car tires are the same exact size as the tires in the 60’s. There’s no way they fit 6.5/8.5 wheels. Your 205/70, 245/60 are much much closer fitment to those wheel sizes. I’ll have to look thru. Your posts for pictures of your car. Thanks.

For my 289 FIA, seeing no further track time, I removed my Avon's and added a simple set up blackwall Cooper Cobras for the street:
235/60/15 for the front
295/50/15 for the rear

The Avons I replaced were the same sizes, and I have no clearance issues, nor rubbing of any kind. Having used the Coopers on other street driven Cobras I've owned, they are already a known entity for me. If you are not planning any track time, do not over think the process, as you do not need a tire rated at sustained speeds of 140mph or above.

The above are readily available and should fit your Unique FIA without any issues.


Bill S.

Bill S, so those tires (235/60, 295/50) are mounting to 6.5” and 8.5” wheels or to 7.5” and 9.5” wheels?

My Cobra…..with 205 70

It's funny, when I had the rims off two weeks ago, I did not even think to look, but believe they are 7.5" and 9.5" rims. If I find this to be different later on, I'll update my post.

Bill S.

Most of the wheel repop manufacturers sizes are 7.5” and 9.5”. The only manufacturer and he stopped manufacturing the wheels over a decade ago was Phil Schmidt.
Most repop Cobra manufacturers were focused on providing cars that could fit much larger (wider) tires on their cars as their clients wanted the big tire look or they planned to track the cars. Kirkhams even went so far as to alter their 289 Cobra frame jigs from the original type structure to one that accept the larger wheel/tire combination supposedly at the request of Shelby on the chassis they ordered for their aluminum body Continuation Series Cobras. I don’t know if Kirkhams ever changed their chassis jigs after that? The EARLY 7000 Series Continuation Series aluminum Cobras had a chassis that represented the original 1960s 289 Cobras.

Now that Superformance has taken over the manufacturing of the 7000 Series FIA Cobras I do not know what wheel sizes they provide with their cars, I would assume that it is still the 7.5” and 9.5” wheel as most of the cars that I have seen run wider tires than what a 6.5” wheel would take? Maybe one of the Superformance owners could chime in?

crosthwaite&gardiner in UK are producing original spec magnesium FIA Wheels in 6,5" (front) and 7,5" or 8,5" (rear)


https://crosthwaiteandgardiner.com/parts/ac

That makes more sense, because the 295/50 on an 8.5" width can look pretty awful, likewise a 235/60 on a 6.5". My Unique has 8"f/8.5"r and is designed for 235/60 and 255/60 combination, but I want the correct FIA look (to me), so i will probably head towards narrower 215 on the front requiring a narrower wheel (Ill do a 7").

I am not trying to overthink, but simply wanting to head towards the most similar sizing (in modern street tires) to the original 6.5/8.5 wheel and accompanying tire set up.

I cant afford the real car, so I want closest look I can achieve (a personal desire) on my Unique FIA.

whats on your car currently?

245/60 and 275/50 currently but they are at least 10 yrs old, probably 12-15. 275-50 isnt a normal size any more for standard street tires.

The Hi-Tech cars (Superformance and Shelby) are supplied with 7.5" and 9.5 FIA wheels. We also have available 7.5" "Kidney Bean" wheels in six-pin drive configuration.

Well after a long time, I settled into a 215/65-15 front on a 7" wheel and a 245/60-15 rear on an 8.5" wheel on our FIA replica.

Im happy, the car tracks well (with 0 toe), enters, and exits well (for me). In hindsight, the only change I'd make, is swapping out the 245/60's for 255/60's; purely for aesthetics.

The 215/65 front is quite similar to the 6.70 original and the 245/60 (and 255/60) rear are quite similar to the 8.20 original.

I realize most of the current FIA replicas are running 7.5”/9.5” wheels. I feel 235/60-15 (and 245/60-15) and 295/50-15 are very decent as well matching the current SCCA AP race sizing quite well.?

Pics????

Figured I’d post mine
205/70 fronts
225/65 rears