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?


http://forums.maxperformanceinc.com/...1&d=1566437420

Here's the original G70 Goodyear wide tread I have.

http://forums.maxperformanceinc.com/...1&d=1566439273

http://forums.maxperformanceinc.com/...1&d=1566439273

http://forums.maxperformanceinc.com/...1&d=1566439273

http://forums.maxperformanceinc.com/...8&d=1566439261

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

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. :)

Easily misunderstood since a greater weight rating would require a larger tire. New technology has changed that assumption in some respects.

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.

My 69 came with F-70 14's, still have the original spare in the trunk.

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.

Ha......good question, don't know.

[url]https://www.tacomaworld.com/tirecalc?tires=225-70r14-235-50r17[/url

Great forums
Have a 2105

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.

Yes I am, drove it off the show room floor. The spare in the trunk still has the sticker on it.

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.

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.

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.

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.

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

https://forums.maxperformanceinc.com...1&d=1567532878

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.

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.

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/