70 series or 60 series tires for my '69 BB?
I've run 255/60/15 tires for a long time, but I'm wondering if there is any real driving difference between them and a 225/70/15. The bigger 60's look very good, and may have a traction advantage, but, are there any differences when normal driving? I've heard that the 60's require more steering effort. True?
Opinions?

 

I went from 225/70r15 to 255/50r17, so not exactly the same, but the same width. I didn’t feel a difference as far as steering effort, but I have power steering. I imagine a car without it might feel a difference.

 

I just don't think you can go wrong with the 255/60/15's when choosing between the two. It's likely harder to turn because of the wider footprint.....I bet you wouldn't notice any difference with the same footprint width between the two profiles.

Just my .02

 

This will come down to your personal preference. There are theoretical differences in steering feel, dry traction, and wet traction for the two, but I highly doubt you'd ever really feel it. I just swapped from 245/60R15s to 275/40R18s on a different car and in normal street driving there was no difference at all. Autocross was a different story, but I was surprised how little difference there was on the street.

If you've only ever run the 255, why are you looking at the thinner tire? Is steering effort an issue for you?

 

With power steering you should never notice any difference in steering effort. Without it you may notice a slight difference at very slow speeds (such as in parallel parking), but once moving the effort shouldn't be any different. In "spirited" driving the wider tire's larger contact patch may actually provide a little more feel and feedback than the 70 series, and obviously will provide more adhesion at the limits.

The original tire on a 69 Corvette (and all 68-72's) was an F70x15, which the modern equivalent of is a 215/70R15. In 73 when Chevrolet went to radials on the Corvette they switched to the slightly larger GR70x15 (225/70R15 today). From 1978 to 1982 all Corvettes came with 225/70R15 tires as standard equipment and 255/60R15's were offered as an option. To be in line with the Government's push to the metric system, in 1978 the tire makers switched from the earlier letter sizes to metric sizing.

Personally I think the slightly taller 225/70 and 255/60 look better on 68-72's because visually they fill the wheel opening better (but the taller tire will have a slight effect on the accuracy of your speedometer).

 

Years ago I went from G60-15 to 225-70 15 and I was impressed with how well the car handled.
now to add to the equation I blueprinted the steering box and rebuilt my TA at the same time so it was a huge difference between before and after but the tires did have an impact

 

The only time I noticed a difference was way back when I changed from the original G70's to the all new Goodrich G50 T/A.

Steering response was like night & day....

 

Yes, even with ps, the car is tiresome after long drives. I wonder if my ps is actually working well?
Perhaps I'm spoiled by the great, easy, experience of driving a C6.
Our local group does monthly 125-200 mile cruises, that include some spirited mountain driving. I'm usually quite a bit more tired, sore, etc. when I drive the '69.
Thanks everyone for your input.

 

Gearing and speedo reading would change slightly due to tire height decrease, although I'm not sure if it would be noticable.

 

I run both. 225/70-15 up front and 255/60-15 in back, on my '77.
Tire rotation from front to back is pretty much irrelevant for a car who's tires age out before they wear out.

 

First question: is the steering actually what makes it tiresome? I can tell you the noise, vibration, and rough ride do a lot more to wear you out than you'd think.
Second question: is the power steering functioning properly? These cars don't generally have that heavy of steering, especially in comparison to a modern car. While 80's land barges would have one finger power steering, modern cars like that C6 tend to run more effort than that.

Assuming those two are correct, you can reduce steering effort with less positive caster in your front alignment, a slower ratio steering box, a larger diameter steering wheel, a lighter weight steering valve, and probably a host of other things I'm missing. I don't think the tires are going to get you there though.