1970 tires

[Duke W.]

Do a generic search for 215/70R15 on the tire rack. Look at a handful of examples and click on "specs". Most will list a recommended wheel width range, and I believe that for this size the typical wheel width recommended range is 5.5-7.5", but the Sprint Classic is 5.5-7".

This tire is designed for vintage cars that typically had wheel widths of no more than 7". The 8" wide wheel that became standard on '69 Corvettes was probably the widest wheel of any production car on the planet at that time. It's perfect for a C2 with OE wheels, especially 6" KO's or Rallys.

The 215/70R15 will look a little "skinny" on a 8" wheel, but I believe it will provide better performance than any less expensive tire of the same size.

If you know of an experienced tire installer, talk to him and also contact the Vredestein US office, try to get a hold of someone who actually knows what they're talking about and discuss.

Take your time, do some homework and keep us informed.

Duke

[Joe L.]

Attached is the tire article from Corvette News that I mentioned in a previous response. This is from the April/May 1970 edition.

[Duke W.]

Thanks for making the pdf files and posting that article, Joe. I'm sure I have that issue in my CN collection.

The "sudden breakaway" characteristics of early steel belted-radials like the 6.70-15 MIchelin X I mounted on my SWC in 1964 were well known as was the fact that radials provided better grip in the wet (due to the deflection from loading being in the sidewall rather than squeezing the tread blocks together as with bias ply tires) , and given that the SWC spent the first five years of its life in Seattle, wet grip was a primary reason why I went with the Michelins. (The other candidates were the 7.00-15 GY Bluestreak Sports Car Special and the Pirelli Cinurato 367. The latter was not available in a suitable size, and I found and bought a set of the former in the mid seventies at Carol Shelby's GY racing tire warehouse in Carson, CA and bought a set of the early Western Wheel KO repros to mount them on.)

The Michelins offered better than bias tire grip in both wet and dry conditions, and since their entire grip range is at lower slip angles than bias ply tires, it gave rise to the expression "like riding on rails". But at the peak of the adhesion curve rather than flatting out before finally falling off, it falls off suddenly, so one needed to develop good SOTP feel for where they were on the adhesion curve. I did lose the SWC twice on those tires back in the day. The first time the road was wet and the second time I was wet, but neither mishap resulted in any damage other than to my ego.

I did have a few other harrowing experiences. If you're familiar with Seattle you might know of North 34th Street that runs on the north side of Lake Union east of the Fremont bridge. This was a part of my route from my parents house in Magnolia Bluff to the Udub campus.

About a mile or so east of the Fremont bridge the North 34th Street rises then drops off leading to a left hand curve of about 50 degrees azimuth change that is both downhill and off camber, and the name changes to North Pacific Street. It was tricky even in the dry, but I always saw it as a challenge, dry or wet.

It was wet and I was doing about 45 MPH (definitely over the speed limit, which was probably 30) and realized that I was too hot approaching the curve - should have been on the brakes earlier, so I got on them, and they started to lock. I reduced pedal effort to unlock the brakes as I entered the turn and the rear stated to slide, but I caught it with a quick steering input, but that got the SWC into a yaw oscillation that I managed to damp out with a few more steering corrections and got through the turn. It was a good learning experience due to the high "pucker factor".

A couple of years later when I needed to replace the Michelins I went with the 205HR-15 Pirelli Cinturato CN-72, and one of Pirelli's key marking points was that this fabric-belted tire had much more predictable breakaway characteristic that I found to be abolutely true., and they also had greater grip than the Michelins, both wet and dry.

I don't know how it was done, but modern steel belted radials have milder breakaway characteristics than those early Michelins, and as far as ride is concerned I found the radials transmitted less high frequency ride harshness like was occurs on worn, patched pavement than the OE two-rayon bias-ply General JetAires.

Duke