<VV> Tires for the 67

[Bruce Schug]

On Sep 15, 2009, at 10:35 PM, Jay Pitchford wrote:

> Mike - check out this link:  http://www.miata.net/garage/tirecalc.html
> <http://www.miata.net/garage/tirecalc.html>You can put in the stock  
> tire
> height for the 'vair (185/80-13 for the LM, similar or same for the  
> EM),
> then type in your potential match beside it. You'll find you  
> 205-70-14 is a
> decent choice for matching original, as you're running 61.6 MPH when  
> the
> gauge says 60 (or about 2.6% big). However, typing in the 205/75-14  
> doesn't
> look so good. Personal opinion, I'd try the 195/70-14 for a better  
> fit both
> width and height with the goal you're looking to achieve.
>
> Jay Pitchford
> Columbus OH
> 65 Corsa 140/4 Vert
>
> On Tue, Sep 15, 2009 at 10:16 PM, <Mikeamauro at aol.com> wrote:
>
>> Needing tires and still pondering what to do. Presently using   
>> 205/70/14s
>> mounted on Camaro rally wheels. I'm considering changing to   
>> 205/75/14.
>> This
>> change in profile would provide a slightly taller tire, with a   
>> little
>> narrower tread width. It's the wife's driver, and the narrower  
>> width  would
>> help
>> a little in low speed turning situations. Has any one else used the
>> 205/75/14 size on a late model? Comments? Thanks...Mike Mauro
>>
>> _



Here are the approximate diameters of original Corvair tires:

6.50-13 = 24.5"

7.00-13 = 25.3"

By going to this link: http://www.powerdog.com/tiresize.cgi

You can calculate the mathematical diameter of the 185/80-13, which is  
24.7".

My regular site no longer has the 80-series 13's showing:

http://ejelta.com/tiresize/

Obviously the 185/80-13 is a good replacement for the 6.50-13. but  
still small for the 7.00-13.

A look at 14" sizes here: http://ejelta.com/tiresize/index.html?ws14=1&

will reveal that a 205/70-14 is exactly the same diameter as a 7.00-13  
and a good replacement for it, if you're trying to get the original  
diameter.

You will also see that a 215/70-15 is 26.11" - a mighty tall tire! I  
certainly would approach a tire of that diameter with caution, as you  
may have some interference. If I could, I'd find a used tire that size  
and mount it, them put the wheel on to see how it fits. Personally, I  
wouldn't run a tire that tall, unless you were setting the car up for  
economy runs ;-)

As for tread width, generally you will find that, as the section ratio  
goes down (like from 75 to 70), the tread width will increase. Look at  
it this way - a tire, in cross section is kinda' oval shaped. Now  
flatten it at the bottom, to create the tread width. Let's say that's  
5". And we'll say our tire is a 75-series tire. Now, let's pretend  
we're going to change the tire to one with a 70 series. We'll do this  
by slicing the oval off higher up on the tire. You could also say  
we're flattening the oval - the tire - more. This makes the section  
ratio lower (like from 75 to 70), the diameter smaller and the tread  
width wider. The tread width gets wider because, you're slicing the  
tire off higher up the oval where the oval, and thus the tire, is wider.

Looking on this site: http://tinyurl.com/qodovp

we see that this Dunlop tire changes its tread width as follows:

205/65-15 = 6.3"

205/70-15 = 6.2"

205/75-15 = 5.7"

Why isn't the change in tread width more proportional? I don't know;  
just the way they makes those tires. This illustrates why you should  
always check the manufacturer's specs.

Finally, regarding steering effort, I think tire construction will  
make as much difference as anything. I recently put new tires on the  
front of my Corvair and the steering effort is quite a bit less.  
There's no other reason for this except for tire construction.

Another factor is tire pressure. If you want to reduce steering effort  
without changing tires, simply put more air in your tires. I'd try 4  
psi more air in the front tires and see how it feels. Don't get too  
far off the 10 psi differential between your fronts and rears on your  
Corvair.


Bruce

Bruce W. Schug
Treasurer & Membership Chairman
CORSA South Carolina
Greenville, SC
Stock Corvair Group
Performance Corvair Group
bwschug at charter.net

CORSA member since 1980

'67 Monza. "67AC140"


P.S.

Seth - I bet you were just waiting for me to do this, weren't you?