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Discussion Starter · #1 ·
I have been looking around to see what kind of tires I can swap out with my old ones. If i read everything correctly, I should have F70x15s originally and a 7 inch rim? The rim appears to be 8 inches wide, but it might just be that I am not measuring between the right spot.

I currently have 3 H70-15s and one F70-15. <sigh>


I wanted to get some new ones, and I wanted to make sure I am looking at the right ones. Appearantly, F70-15 converts to either 215/70R15 or 235/60R15, though many folks get 245/60s and 255/60s, but some of us old c3s rub with 255s.

I should be looking at 235/60, correct?
 

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245's look better in my opinion. My 68 came with those on 74 rims and it looked good. Just a bit wider but no problems with rubbing. Some guys are saying the bigger rims and modern rubber really improve the handling and ride, so do your research before you spend your money.

Not sure what the "correct" width is.
 

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Discussion Starter · #3 · (Edited)
I have been trying to do the research, but I'm never sure what is correct, especially when I find conflicting info. And with 68's having so much one year only items, it's harder to find specific information.

So I summarized what I thought was what I needed, and hoped I got it right. I figured out long ago to ask the 'stupid' questions and let people think what they will, instead of assuming I was right and screwing stuff up :)

I will be keeping the rims I have. Seems I found where to measure the width. 'Rim width is the distance between the bead flanges (inside to inside, not outside to outside)' Seems I have the 7 inch rims indeed.
 

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I'm afraid I can't tell you much about '68 tires specifically, but I just got a new set for my '69. Got BFG radial T/A's for $300 plus shipping online and then another $100 for mounting and balancing.

Original overall diameter was around 27.1" I believe. I got 225/70's up front and 255/60's in back. Not sure if the 7" rim could handle the 255's. :huh:
 

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You can tell if they are original 68 rims by looking for an AG stamped on the rim. If you have original rims that is a plus, I had to hunt for mine. My reference book also says there is a stamping on the inside of the rim that says the width. 68's will be 7". AZ code will be 8" rims

Here is some more info
F load rating
70 aspect ratio height to width (height is 70% of width)
15 bead to bead diameter

On the 235 tire that is the width of the tread in mm.
 

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Discussion Starter · #7 ·
You can tell if they are original 68 rims by looking for an AG stamped on the rim.
Took some searching around, but I did find it. The one I looked at had K18 4 . 23 AG
 

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Took some searching around, but I did find it. The one I looked at had K18 4 . 23 AG
K18 Kelsey Hayes, Chevrolet, 1968

2 Month

23 Day

AG Corvette

7 or 8 years ago I paid $70 a rim for correct rims. I think they've gone up.

If you really want F70's I think Coker tire or other specialty tire companies still make them
 

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I have been looking around to see what kind of tires I can swap out with my... If i read everything correctly, I should have F70x15s originally and a 7 inch rim?
Yep.


The rim appears to be 8 inches wide, but it might just be that I am not measuring between the right spot.
7" for original 68s and 8" for 69+. In either case the OE size was F70.

I currently have 3 H70-15s and one F70-15. <sigh>
Those must be pretty old...?!!?


I wanted to get some new ones, and I wanted to make sure I am looking at the right ones. Appearantly, F70-15 converts to either 215/70R15 or 235/60R15,
Neither size - actually it converts almost exactly to 225/70R15 which is also the standard tire GM replaced the F70/G70 with back in 1978.

though many folks get 245/60s and 255/60s, but some of us old c3s rub with 255s.
<sigh> Yes most do. The 255 'fills up' the wheel well and is almost universally a NON-performance tire though it will likely wear a performance looking cosmetic sidewall treatment. Yes, they 'can' rub the fronts particularly on early C3s up front especially when turned and going over a bump... They offer no performance tires whatsoever in this size either - just very very basic entry level tires which happen to have raised white letters.

I should be looking at 235/60, correct?
No - I'd recommend the 225/70R15. It's a direct replacement for the F70 dimensionally. There are also a 'FEW' actual performance tires available in this size that are on par w/ the tires the C3 was intended for.

Look for a 225/70 with A-TEMPERATURE (which usually means atleast an H if not V SPEED rating). This is a minimal specification IMHO and something I would put on a minivan or economy commuter car as well.

As for specifics a few still offering performance tires as of a couple years ago included: Goodyear Eagle RSA, Firestone PV41, General XP-2000, Michelin Pilot XGT H4 and Cooper Cobra GTH (discontinued?) and possibly the Sumitomo HTR 200 (discontinued?)

The 235/60 may also be an option - it will nominally carry about 25 more revs per mile than the OE F70 or 225/70s - roughly a 3% smaller rolling diameter. Pirelli and Michelin used to offer performance tires in this size. AFAIK those were the only 2...?

Good luck!
 

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I have been looking around to see what kind of tires I can swap out with my old ones. If i read everything correctly, I should have F70x15s originally and a 7 inch rim? The rim appears to be 8 inches wide, but it might just be that I am not measuring between the right spot.

I currently have 3 H70-15s and one F70-15. <sigh>


I wanted to get some new ones, and I wanted to make sure I am looking at the right ones. Appearantly, F70-15 converts to either 215/70R15 or 235/60R15, though many folks get 245/60s and 255/60s, but some of us old c3s rub with 255s.

I should be looking at 235/60, correct?
Greetings, I run the firehawk 500's 235/60 /15's on the original 7" in rims, the 245 will fit all four coners, and the 255 will fit only in the back on our cars

cheers


here are the 235 on all 4 corners, no issues on these fpr two seasons now




tim
 

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Discussion Starter · #11 ·
Those must be pretty old...?!!?
Yep, I'm guessing the same tires on the car since the mid 70's. Worst part is that they still had loads of tread on them still.:laughing:

I got the 225/70s. I have the next 6-10 years to think about the next set. :devil:

 
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