Date: Sat, 19 May 2001 04:57:21 -0000
Reply-To: Mike Finkbiner <mike_l_f@hotmail.com>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike Finkbiner <mike_l_f@hotmail.com>
Subject: Tires, Load Range and Pressure
Content-Type: text/plain; format=flowed
Volks -
I think I have been giving the wrong advice about the proper load range for
Vanagon tires.
I came to this conclusion a couple of weeks ago as I was driving to Seattle
at 55 mph, breaking in a new engine. You seem to have more time for thought
when the scenery is slipping by more slowly.
On the information panel on my '87 Westy, it lists two possible tire sizes
185R14 C, inflated to 43 psi front, 48 on the rear or 205/70R14 Reinforced
97, inflated to 36 front, 40 psi on the rear.
It's always bothered me that the only one of the two that specifies a load
range is the 205. The 185 just says C (equivalent to the old "6 ply"
rating). Why is that?
In a word, pressure. The load capacity of a tire is specified at maximum
pressure. A 185R14 C tire with a maximum inflation pressure of 50 psi and
the common load range of 93 (the Kirkland tires come to mind) can carry 1433
pounds at 50 psi. At 48 psi it can carry a bit less.
A 205/70R14 reinforced, also with a maximum pressure of 50 psi, can carry
1609 pounds - AT 50 PSI. At the VW spec of 40 psi, it will be a lot less.
How much? According to one article I found, Ford said that dropping the
pressure from 30 psi to 26 psi on the Explorer could reduce the capacity by
400 pounds (didn't say per tire or per vehicle). If it's per vehicle,
that's 25 Lbs capacity per tire per pound of pressure. Ten psi would be 250
pounds per tire, so the 1609 capacity is now 1359. That's not an accurate
figure, but it's probably in the ballpark.
So - I'm willing to bet that a load range 93 tire at 48 psi can handle the
same load as a load range 97 tire at 40 psi, if they both have a max
pressure of 50 psi.
The 185/14 Agilis, by the way, has a load range of 99 (1710 Lbs) but at a
max pressure of 54 psi.
At least my advice has been erring on the side of caution, but after working
this through, I'm a lot happier with all of the load range 93 tires people
have been talking about.
As long as they keep them at least 48 psi on the rear.
So go check your tire pressure!
- Mike Finkbiner
'87 Westy
Moscow, Idaho
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