jusplainwacky

One would think that with all the threads (no pun intended) on tires, how can anyone be confused...well, leave it to me.

I asked Diamond Back what tire they would recommend for a 58 corvette and this is what they said...

Yet, it appears that most people on this forum are choosing the 205/70R15...why is this...wouldn't the speedometer be off?

I was thinking of going with the 215/75R15 because that seems to be the closest to the same diameter as the original, but a wider thread...but then I read my spare tire cover would be sticking up quite a bit....but I hear it will stick up with the 205/70R15. I'm guessing the original 6.70-15 was skinner than the 205/75R15 so this wasn't a problem?
I really don't want to put a Chevy S10 tire in the truck...I want a real spare.

-Dennis

59BlueSilver

The "real" spare I went with is the Kumho 165/80R-15 (25.4" dia.). It fit the cavity.

SW Vette

I think you'll find that 215/70-15 is the best overall compromise for width and diameter.

jusplainwacky

Hey SW...but what I don't get is why people don't go with an R75...it would be about the same diameter as the original and your speedometer would read correctly. Seems most go with the R70 even as you recommended.

SW Vette

215/70 gives you almost the same diameter as 205/75 and slightly more width. I don't have the exact numbers in front of me but you can find a converter on the interwebs.

jusplainwacky

I posted the diameters on my first post. You can see the difference from the original.

SW Vette

Ok, here's the correct data:

jusplainwacky

Very cool. The information I posted is based on the tires Diamond Back sells.

jusplainwacky

I like that website...very informative. Still confused as to why people choose the 70R15 verses the R75...cause the R75 is closer to the same diameter as the 6.50x15 if I'm understanding this correctly.

SW Vette

You've transposed the profiles - it should be 205/75 vs. 215/70. The diameters are so close, difference in speedo error would be less than 1%.

SW Vette

Here's a chart without all the confusing diameter data

jusplainwacky

According to the chart...(6.50-15)...why is it that the wider the tire, the smaller diameter is the equivalent? I don't get it...one would think that you'd keep the same diameter regardless.

jusplainwacky

Although I have received a lot of information on tires on this thread....my question still hasn't been answered.
Why is it that the majority of people are buying the 205/70R15 tire for their C1 when the 205/75R15 would be closer to the same diameter as the original?

59BlueSilver

I don't. I buy the 205/75R15.

jusplainwacky

LOL
Is your speedometer accurate? What tires did you put on the car? Do you like them?

59BlueSilver

Yes, love em and hope to replace them with same. BF Goodrich Silvertown radials with 2.25" whitewall. Speedometer is accurate.

jusplainwacky

Good info!! Thanks!!
I'm thinking of putting on Diamonback's.

rfn026

I simply gave up on the speedometer thing. I use an iPhone Ap. Actually I use 2 different ones.

One is called Speed Box and the other is called Speedometer.



The nice thing is you can check the accuracy of your other cars as well.

Richard Newton
Car Tech Stuff

Frankie the Fink

Because most people aren't as **** as you...if you're abandoning originality for a radial tire why not get a little more "meat on the street". I bought mine because that's what the guy at the NCRS meet 4 years ago had stacked up beside his tent - 4 new tires, still in the blue wrap, Diamondback wide whitewalls for $600. You think I was worrying about exact sizes ?

Secondly you presume an accuracy on the old cable driven speedometers that doesn't exist. The difference in the tire diameter is prob within the margin of error for a 50 year old cable driven speedometer.

If you want a different size than everybody else bought - go buy it.
Why obsess over what they did ? Having read dozens of your posts their rationale isn't gonna satisfy you anyway.

Roger Walling

I had just purchaced a 700R4 without the speedometer gears, I called PATC,(https://transmissioncenter.net/shop/) and they instantly gave me the info that I needed. Naturally I purchased the gears from them right away. No guess work just excellent service. All you need is gear size and tire dia.