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#1
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Original tire sizing G70 or F70?
For some reason I had been thinking that F70-14 was be the correct size on my 68 after measuring an original spare. Getting ready to order a set of tires & was planning on that size. Then I took a closer look at my original spare which I didn't realize is a G70-14.
However when I measure the width, tread width & diameter this G70 matches what Kelsey shows in the sizing chart as a F70. 6.5+ tread width, 8.75" sidewall width & height I am not sure if thats measured at the start of the tread edge on the side wall, or the center of the tire tread where its bulges out & is the absolute tallest? This G70 original is 26" to the edge where the tread starts, but 26-3/4 at its largest diameter (very center of the tread) so close to both specs depending on where you measure. Any idea why that would be? Are G70's the standard GTO tire size? I'm guessing so...... Build sheet says "G70 white wide oval" http://www.kelseytire.com/pages/preformancetires2.html Are the re-pops a little wider, bigger?
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68 GTO 4-spd Convertible 78 S/E Trans am L78, WS6 Auto 78 S/E Trans am W72, WS6 Auto 79 10th aniv W72 Trans am 80 Indy pace car Trans am 89 Trans am GTA Last edited by 68ragtop; 08-21-2019 at 09:35 PM. |
#2
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Here's the original G70 Goodyear wide tread I have.
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68 GTO 4-spd Convertible 78 S/E Trans am L78, WS6 Auto 78 S/E Trans am W72, WS6 Auto 79 10th aniv W72 Trans am 80 Indy pace car Trans am 89 Trans am GTA |
#3
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A G70 x 14 from Goodyear may have slightly different measurements than a Firestone or a Kelly. There's no hard and fast rule that they had to be a certain size. The G or F only specifies a weight rating of the tire.
The tire should be mounted on the appropriate size wheel to obtain the correct measurements. More good info https://www.tirerack.com/tires/tiret....jsp?techid=45 This is a chart I use from time to time. https://www.tirerack.com/tires/tiret...rsionchart.jsp Another tire tool I like to play with. Only good with Metric size tires though. https://www.tacomaworld.com/tirecalc...0r14-235-50r17
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express Last edited by OG68; 08-21-2019 at 11:14 PM. |
#4
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I never knew it was a weight rating thing. But now that you say that I do see the correlation in the chart. I have always thought it was a tire width to height ratio like F70 was the early system of 215/70 for example. E,F,G being the width. I never really studied the old tire sizing further than that assumption.
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68 GTO 4-spd Convertible 78 S/E Trans am L78, WS6 Auto 78 S/E Trans am W72, WS6 Auto 79 10th aniv W72 Trans am 80 Indy pace car Trans am 89 Trans am GTA |
#5
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Easily misunderstood since a greater weight rating would require a larger tire. New technology has changed that assumption in some respects.
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express |
#6
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G77 x 14 Red line standard. White line optional. G70 x 14 Wide Oval optional in Red or White line. 205R x 14 White line radial optional.
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74 LEMANS GT 350 4SPD MAROON Last edited by JKGTO; 08-22-2019 at 12:45 PM. |
#7
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My 69 came with F-70 14's, still have the original spare in the trunk.
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#8
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Is it possible the verts had G70's because of the extra weight? Mine is checked G70 wide oval. No brands specified on the tire options box except the "G70 wide Oval. My 68 spare is a G70, but its a goodyear wide tread, not a wide oval.
Hmmmmm.
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68 GTO 4-spd Convertible 78 S/E Trans am L78, WS6 Auto 78 S/E Trans am W72, WS6 Auto 79 10th aniv W72 Trans am 80 Indy pace car Trans am 89 Trans am GTA |
#9
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Ha......good question, don't know.
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#10
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[url]https://www.tacomaworld.com/tirecalc?tires=225-70r14-235-50r17[/url
Great forums Have a 2105 |
#11
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Are you the original owner of this car? Pontiac never offered an F70-14 tire on a 69 GTO. All you could get were G-78-14 tires or G-70-14 tires.
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#12
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Yes I am, drove it off the show room floor. The spare in the trunk still has the sticker on it.
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#13
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69 GTO had as standard a G78 tire (redline, whiteline a no cost option). The only optional tire size (and standard on the judge) was the G70. Chevelles though ran F70, so perhaps that 69 got the wrong tires on the line. The radial option in 68 was not offered in 69.
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My Break Away Squad 1969 Fbird (Base, 350 & Sprint Cvt’s - 400HO & TA Hardtops) 1969 LeMans (2dr & 4dr Hardtop and a Cvt) 1969 LeMans Safari 2 seat Wagon 1969 GTO (2 Cvt, 2 Hardtops & Judge Hardtop) 1969 Catalina (3 Cvt’s & a 2dr hardtop) 1969 Ventura 2 Seat Wagon 1969 Executive 4dr Sedan 1969 Bonnie Cvt 1969 Bonnie 3 Seat Wagon (2 of them) 1969 Bonnie Brougham (4dr Hardtop & Cvt) 1969 Grand Prix SJ (2 of them) 1969 2+2 2dr Hardtop (Canadian model) |
#14
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Yeah we've hashed this out before. Dad bought the car brand new and still owns it. Drove it right off the show room as he described. It was built at the Baltimore plant where they also had chevelles rolling down the line so the best scenario is that it likely got the F70's by mistake. It's a very early 69 as well with the blacked out tail panel, first few weeks of production. 2nd week of Sept if I remember right.
Anyway, it definitely left the factory with the F70's, skinny white walls to be exact, and the original spare is still in the trunk, never touched the ground. If the car were to ever get restored back to factory stock, I'd put the F70's back on it.....just because. I'm sure it's not the only anomaly out there. |
#15
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Did installing wrong equipment happen from time to time? Or was it a fairly frequent occurrence?
My 68 Fremont car came with the 4 blade RA fan even though the 5 blade flex was standard for the WT engine.
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express |
#16
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Yes happened among all the brand cars. I know of a few examples. For instance quite a few survivor certified Chevrolet Biscayne's and Chevelles have been discovered in the later part of the 60's that received a few upscale interior trim pieces like rear side panels and other weird anomalies like that.
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#17
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So I am curious what you guys think about white lettered tires on the 68-69's
Why do you suppose the firestone wide ovals seem to be the tire of choice when installing a period correct white lettered tire? It would appear many of 68-69 cars (including my 68) had Goodyear wide treads. Of course these were red or white lines, but I am really puzzled why you don't see don't use good year polyglass, or Wide tread white lettered tires very often. Any thoughts? Here is an image of a 69 with them. I like the look
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68 GTO 4-spd Convertible 78 S/E Trans am L78, WS6 Auto 78 S/E Trans am W72, WS6 Auto 79 10th aniv W72 Trans am 80 Indy pace car Trans am 89 Trans am GTA |
#18
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While white letter repro rubber looks nice it isn’t correct for any 69 Pontiac (except late production 69 TA). As you mentioned only red or white line (3/8”) was possible on 69 non judges and for 69 judges your third correct choice is blackwall.
Given the high price of repro tires I wouldn’t use those white letter tires. If your going non-correct you might as well go with much cheaper and better modern white letter radials.
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My Break Away Squad 1969 Fbird (Base, 350 & Sprint Cvt’s - 400HO & TA Hardtops) 1969 LeMans (2dr & 4dr Hardtop and a Cvt) 1969 LeMans Safari 2 seat Wagon 1969 GTO (2 Cvt, 2 Hardtops & Judge Hardtop) 1969 Catalina (3 Cvt’s & a 2dr hardtop) 1969 Ventura 2 Seat Wagon 1969 Executive 4dr Sedan 1969 Bonnie Cvt 1969 Bonnie 3 Seat Wagon (2 of them) 1969 Bonnie Brougham (4dr Hardtop & Cvt) 1969 Grand Prix SJ (2 of them) 1969 2+2 2dr Hardtop (Canadian model) |
#19
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The original tires on dad's car are Goodyear Wide Treads, albeit in the F-size but still.... They are also thin white stripe tires.
I do like the Goodyear white letters as well as the Firestone Wide Oval white letters. Probably 90% of what I see in correctly restored cars out here are using the Goodyears though, so I've never considered the Firestones the tire of choice, least not around here. |
#20
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I had a set of Eagle STs back in the 80s. I'm sort of torn between those and the redlines. Then again my car came with 3/8 white lines which may look good with steelies and dog dish hubcaps.
But I'm not putting bias ply tires on it, so that may limit me to Diamond Back MX 215/70 x 15 tires made by Michelin. Available in 3/8 Red or Whiteline.. They also have Nexan, Toyo and BFG in a 225 size. Decisions, decisions https://dbtires.com/product-category/tires/
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express Last edited by OG68; 09-03-2019 at 02:32 PM. |
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