<VV> The Radial Conundrum

[James Davis]

Well not exactly.  Air pressure in radial tires does two things it cushions 
the ride and it supports the tire.  Most car tires are sized so that they 
can carry the full loaded weigh of the car with just a llitle to 
spare.  This requires the tire be filled to close to its rated maximum 
pressure. It also improves the fuel economy to use as small a tire as 
possible with maximum air pressure.   Thus GM sized the 65 Corvair with 
6.50 x 13 2 ply (4 ply rated) Firestone bias tires.  Tire technology has 
really improved since then.  Considering that a Corvair will rarely have 
more than 1,000 on the front tires, it doesn't take much air pressure to 
support the front.  Consider a 185/70-13 it is rated at 1135 lbs at 35 psi 
or 500 lbs at 16 psi.  The rear tires are another problem.  There could be 
as much as 1,900 lbs on the rear.  Figure 29 psi to carry a 950 lb 
load.   Secondly to create the desired understeer (push) so necessary to 
keep the average driver out of trouble GM recommended a 10 psi difference 
in front and rear tire pressure.  I run 195/70-14 on my Corsa and find the 
18 psi on the front and 28 on the rear to be the best..  But then I like a 
stiff ride
Jim Davis

At 08:17 PM 11/4/2004, Songs by Steve wrote:
>Hello again, groupies.
>
>
>
>I've been doing a little research, and it appears that almost
>overwhelmingly, people feel that radials on 'Vairs are a great improvement
>over belted tires.  When I bought my '62 convertible, I immediately put a
>set of fresh 185/13 radials on the car.  The guys at the tire place said
>they were going to send my old tires to the "tire museum", as they were a
>mixed bunch of belted tires from the early 70's.. shined like glass, and as
>hard as diamonds!!
>
>
>
>My question is about the best tire pressure.  I've been told that too little
>pressure in a radial will damage the steel belts, and on the other hand,
>radials.. in a perfect world should have approx. equal pressure in all 4
>tires.  I think 15 psi in the front is too low for radials, so I currently
>have about 20-22 psi in the front, and approx. 28 psi in the rear tires.  I
>do only normal driving around town and on the H-way.  The tires feel fine,
>etc., but I seek the "wisdom of the group" on whether there is an ideal
>range for air pressure.
>
>
>
>My feelings can best be summed up in the following song, sung to the tune of
>"twinkle twinkle little star":
>
>---
>
>Tire Pressure where are you?
>
>I need advice on what to do
>
>Too much air will make them pop
>
>Not the ideal way to stop,
>
>Pressure, pressure where are you?
>
>That is why I'm writing you.
>
>
>
>---
>
>
>
>(Hey, that's what I do!)
>
>
>
>Songs by Steve