<VV> Tire size vs air pressure survey

[gerg]

How does the circumference of the 6.50 x 13 compare to the 185/80 ?

I had 185/70s up front and at 60mph the speedo read ~5 mph high. Now, with 185/80s, at 60 it reads about 2mph low. Speed measured by GPS. By this I figure either the original tires were slightly smaller than the 185/80 tires or the speedo is just within expected tolerance.  

Thanks,

Greg Blakeney
(318) 680-9224
www.calix.com

> On Dec 31, 2013, at 12:31 PM, Jim Davis <jld at wk.net> wrote:
> 
> It is the air pressures in the tire hat holds the car up.  The more 
> pressure the more load the tire can carry.  It is hard for me to 
> consider the suggested pressures found on the glove compartment door of 
> my 1965 Corsa revelent with today's tires.  After all, the original 
> equipment tires were Firestone 2 ply nylon, bias ply in the 6.50x13 
> size.  Since the early 1970s the tires have been 195/70-14 on five spoke 
> Fenton 14x6 wheels.  The current tires are Kumho Solus KR21s with a 2 
> ply polyester with dual steel belts.  The Corsa has the F41 option with 
> quick steering box and arms and Positraction.   A little white shoe 
> polish and an empty parking lot show that 24 psi front and 36 rear is 
> the best compromise between ride quality and handling.  This is a trip 
> car with over 300,000+ miles on it (one owner).  Weighing the car shows 
> 1,100 lbs on the front and 1,700 on the rear.  Max recommended tire load 
> is 1,356 @ 44 psi.   Thus the minimum air pressure would be 18 psi on 
> the front and 28 on the rear.  Any extra loading to the car besides the 
> one driver whose weight is included would have to be compensated for.
> Jim Davis
> 
> 
>> On 12/31/2013 11:34 AM, Paul Fox wrote:
>> Of course you are correct provided you use what the car came with from the factory. But if you make any changes which most of us do. I would make sure you talk to the experts to see which if any changes need to be made in pressure. Like I say there are many variables.
>> Sorry didn't mean to start a flame war.
>> Paul Fox
>> 
>> 
>> 
>> On Tuesday, December 31, 2013 11:12 AM, gerg <gergwerks at comcast.net> wrote:
>> 
>> I just had new 185/80s put on last night. I expect the tire shop put 32lbs in all. I'll check. However, I did notice that the outer edges of the front tires showed no road contact - no dirt / white dust on the outer edges, center contact only. Rode a little stiff up front too. I'll check them and drop front pressure and see what happens.
>> 
>> Thanks,
>> 
>> Greg Blakeney
> 
> 
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