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1968 Spare Tire Rim Size Same?

 
Old 04-30-2019, 05:46 AM
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Redvette2
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Default 1968 Spare Tire Rim Size Same?

My PO put a 14" tire and rim in the spare tire holder which of course does not fit my 1968 car. Fortunately I found out before I needed it. I researched and believe the stock 1968 rim size was a 15 x 7, 5 x 4.75 (120.65mm) bolt pattern with -.28" (-7mm) offset with a 3.22" backspacing. My question is before I buy a new rim....is the spare rim size the same as the other rims on the car?

YEAR, MODEL, WHEEL LOCATION, WHEEL SIZE, OFFSET, BACKSPACING, TIRE SIZE
1968, Corvette, Rally Front/Rear,15”x 7”, ( - ) 7mm, 3.22”, F70 x 15

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Last edited by Redvette2; 05-01-2019 at 01:07 PM. Reason: Error....s/b -.28" (-7mm) offset
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Old 04-30-2019, 06:08 AM
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My 6t8s previous owner had put 15x8s on, but the spare still was a 15x7. T
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Old 04-30-2019, 07:26 AM
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Yes, the spare is the same size and specs as the other 4 wheels.
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Old 04-30-2019, 07:29 PM
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Redvette2, the stock '68 rally wheel is typically described as; AG 15" X 7" wide with backspacing of 3 & 3/4"

Good luck... GUSTO
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Old 04-30-2019, 11:07 PM
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Yes I confused backspacing with offset. Found a site with more information also.

Thanks,
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Old 05-01-2019, 11:22 AM
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Originally Posted by Redvette2 View Post
Yes I confused backspacing with offset. Found a site with more information also.

Thanks,
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John, if you can find a 15" X 7" Corvette rally wheel, to mount a spare, you will probably have fewer issues getting it to fit into the spare tire carrier as well.

I have a '73 and mounted two different, brand new, 225/70-R15 radials on a Corvette rally wheel (15" X 8") and could not get either of them to fit into the spare tire carrier and close it. The 225/70-15 is supposed to be the equivalent of the standard GR70-15's that came on the '73. I had to drop down a size to get a tire to fit in there.

Good luck... GUSTO
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Old 05-01-2019, 01:02 PM
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After much thought and digesting all the information, I decided to go with a 205/65 R15 tire on a 15 x 7 rim with 6mm offset as the spare. The tire is the same diameter as the 225/60 R15 BFG's tires I just put on the rolling wheels. I will update the post as to how well it fit soon as I put the spare on.

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Old 05-01-2019, 02:22 PM
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Originally Posted by Redvette2 View Post
After much thought and digesting all the information, I decided to go with a 205/65 R15 tire on a 15 x 7 rim with 6mm offset as the spare. The tire is the same diameter as the 225/60 R15 BFG's tires I just put on the rolling wheels. I will update the post as to how well it fit soon as I put the spare on.

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John, did you mean to say 225/70-15, or 225/60-15?

The original tires on the '68 were F70-15's which are nominally 27" in diameter. The 225/60-15 is 25.6" while the 225/70-15 is 27.4", closer to the original size tire. Just curious...

Again, good luck... GUSTO
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Old 05-01-2019, 03:14 PM
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Originally Posted by GUSTO14 View Post
John, did you mean to say 225/70-15, or 225/60-15?

The original tires on the '68 were F70-15's which are nominally 27" in diameter. The 225/60-15 is 25.6" while the 225/70-15 is 27.4", closer to the original size tire. Just curious...

Again, good luck... GUSTO
No....I did put on 225/60 R15's. The 70 series was too big in diameter (27.40" vs. stock 26.30") and 225 was not available in a 65 profile. I wanted a smaller diameter tire anyway as my car is geared really tall. Fortunately this size was still good on the freeway. Here is my chart with the sizes.

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1968 Corvette Tire Size Chart


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Old 05-01-2019, 09:26 PM
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Originally Posted by Redvette2 View Post
No....I did put on 225/60 R15's. The 70 series was too big in diameter (27.40" vs. stock 26.30") and 225 was not available in a 65 profile. I wanted a smaller diameter tire anyway as my car is geared really tall. Fortunately this size was still good on the freeway. Here is my chart with the sizes.

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John, I was just wondering where you got the diameter for an F70/15 as 26.30 inches. Everything I've found shows the F70/15 as just over 27" (27.09-27.10) back in the day.

Based on your numbers however, I see why you chose the tire you did.

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Old 05-01-2019, 09:43 PM
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I'm curious to hear how it fits in the spare tire holder. I just purchased a tire for my spare tire holder and it didn't fit. I'm using a factory rally wheel and would like a tire around 26" in diameter. Very much like your going to test out.
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Old 05-01-2019, 10:03 PM
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Originally Posted by GUSTO14 View Post
John, I was just wondering where you got the diameter for an F70/15 as 26.30 inches. Everything I've found shows the F70/15 as just over 27" (27.09-27.10) back in the day.

Based on your numbers however, I see why you chose the tire you did.

GUSTO
A web site I initially found said that the metric equivalent to the F70-15 was the 205/70 R15 (26.30) metric size. https://www.turbinecar.com/tires.htm Other sites say 215/70 R15 (26.85) so yes it could be bigger. My car feels like I am starting off in third sometimes so I went lower.

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Last edited by Redvette2; 05-01-2019 at 10:04 PM. Reason: Punkuation.
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Old 05-01-2019, 10:29 PM
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Originally Posted by gunrunr View Post
I'm curious to hear how it fits in the spare tire holder. I just purchased a tire for my spare tire holder and it didn't fit. I'm using a factory rally wheel and would like a tire around 26" in diameter. Very much like your going to test out.
Will advise in this post...waiting for rim to come to the tire shop. I will also indicate the tire/rim brands and sizes if it works.

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Old 05-02-2019, 12:20 PM
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The spare tub is adjustable for tire width. I believe that i's the same hardware as came on later C3's. You may have to extend the hangers, but I doubt it.

If you intent to actually use the spare if you experience a flat or damaged tire, I would recommend putting the same size wheel and tire as you have on the car. If you just want to have a 'correct looking' spare tire, get a '68 rim (7" width) and an F70-15 tire. There are lots of them folks already have in their spare tubs (originals that never hit the ground). I have one in mine. It's a Goodyear tire
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Old 05-02-2019, 12:54 PM
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Originally Posted by 7T1vette View Post
The spare tub is adjustable for tire width. I believe that i's the same hardware as came on later C3's. You may have to extend the hangers, but I doubt it.

If you intent to actually use the spare if you experience a flat or damaged tire, I would recommend putting the same size wheel and tire as you have on the car. If you just want to have a 'correct looking' spare tire, get a '68 rim (7" width) and an F70-15 tire. There are lots of them folks already have in their spare tubs (originals that never hit the ground). I have one in mine. It's a Goodyear tire
In my case I just want to have something safe and reliable in case of emergency. My car is a frankenvette already so having an original is not necessary for me. What I picked for the tire is the same diameter as my rolling wheels using the same 15x7 rim size but is a narrower 205 size to hopefully fit in the carrier. I see that it is adjustable but seems like some owners still have issues with the wider tires.

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Old 05-02-2019, 11:05 PM
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Well the plot thickens...on another forum post here today an original Goodyear Wide Tread F70-15 spare tire was measured to be 25 3/4 inches in diameter! Doesn't really match any of the suggested metric sizes. I think I am overthinking all this.

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Old 05-03-2019, 04:09 PM
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Well I put a 205/70R15 in the spare tire carrier and it closed nicely. With that headache down, its off to the next one.
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Old 05-03-2019, 06:05 PM
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Default 15 x7.0 x2!

Originally Posted by GUSTO14 View Post
Redvette2, the stock '68 rally wheel is typically described as; AG 15" X 7" wide with backspacing of 3 & 3/4"

Good luck... GUSTO
15x7's; the last year for the 15'x7' wheel.
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Old 05-03-2019, 08:23 PM
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Originally Posted by gunrunr View Post
Well I put a 205/70R15 in the spare tire carrier and it closed nicely. With that headache down, its off to the next one.
Sounds like I should not have a problem with 205/65/R15 then. I will know tomorrow when I pick it up.

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Old 05-04-2019, 04:35 PM
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Default This worked for me....

Originally Posted by gunrunr View Post
I'm curious to hear how it fits in the spare tire holder. I just purchased a tire for my spare tire holder and it didn't fit. I'm using a factory rally wheel and would like a tire around 26" in diameter. Very much like your going to test out.
Put the 205/65 R15 tire mounted on a 15 x 7 inch rim (6mm offset) and first checked the on car fit and then got it to fit in the holder. Had to lengthen the back two rods and fight with it a bit but got everything to snug up tight. The tire measured a little over 25 1/2" in diameter and the overall width was 8 1/2". Looking at the tire in the tray it seems like going more than 1/2" more in diameter (26+") would cause the tire not to fit totally flat in my carrier. However my carrier is a little bit bent up. Fortunately the 205/65 R15 tire was close enough to the diameter as the 225/60 R15 BFG Radial TA's I just put on.

Tire = Sentury Radial Touring, 205/65 R15 XL BSW $38.00

Steel Rim = Unique 144, P/N = 15X7 5-114.30/120.65 6 CSCHXX $64.00

Discount Tire out the door with taxes, mount and balance but no extended warranty = $133.89

Lesson learned...the formulas and website numbers do not match well with the actuals for the tires. Same sizes vary between models and manufacturers.

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Last edited by Redvette2; 05-07-2019 at 01:14 PM. Reason: More accurate measurements.
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