Date: Wed, 9 Mar 2011 14:42:32 -0500
Reply-To: Mike S <mikes@FLATSURFACE.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike S <mikes@FLATSURFACE.COM>
Subject: Re: And now - still trying for NEW TIRES
In-Reply-To: <BA97A528226E48FEBAB4F9B9A4E0E61E@RON>
Content-Type: text/plain; charset="us-ascii"; format=flowed
At 11:52 AM 3/9/2011, The Bus Depot wrote...
> > Maximum load != normal load. Do you always drive your Vanagon
> > loaded to full weight capacity? The regulations certainly
> > don't expect that to be the case, and that's not what they apply
> to.
>
>Exactly. What the D.O.T. is saying is that there should be a safety
>margin -
>that "maximum load" means just that, maximum, not typical. They are
>saying
>that while the vehicle can be driven periodically with the maximum
>load that
>the tire can handle (if it is an LT rated tire - otherwise 9% below),
>on an
>ongoing basis its NORMAL load should be at least 6% BELOW the tire's
>rated
>capacity.
Or derated capacity, in the case of a passenger car tire. So, you take
a Load Index 97 passenger car tire, which is rated for a maximum load
of 1609 lbs. Divide by 1.10 and you get a rating of 1463 lbs when used
on a Vanagon. That's suitable for a normal, non-Synchro, Vanagon,
including Westys, which have a rear GAWR of 2866.
The regs say the "normal load" has to be 6% under the tire rating (2 x
1463 = 2926). The regs also define "normal load" to include a single
150 lb passenger in the rear.
It's been previously reported here that the actual rear axle weight of
a standard Westy is ~1920 lbs (
http://gerry.vanagon.com/cgi-bin/wa.exe?A2=ind0110C&L=vanagon&P=R9822&m=164259
). Add 150 for the "normal load" occupant, and you're at 2070, a full
29% below maximum capacity. Some other places say a Westy can weigh as
much as 2420 lbs in the rear, which with a 150 lb passenger still puts
you more than 10% under the maximum rated load. The 6% simply doesn't
apply on a Vanagon, ever.
Additionally, the maximum capacity rating for P-Metric tires is
standardized to an inflation pressure of 35 psi. VW never spec'd an
inflation pressure that low for the rear (minimum was 40), and higher
pressures = more load capacity, which only increases the margin.
Finally, in the final years of the Vanagon, the OE tires were, guess
what, 205/70R14 97R. Your "you need 99's" contradicts what VW actually
used.
>Bear in mind that VW Campers were sold by Volkswagen as "unfinished
>vehicles" and the GWVR is based on that designation. That is why a
>Westy and
>a Non-Westy have the same rated GWVR. So a Westy will NEVER operate
>at
>"normal load" - rather, it approaches "fully laden" at all times.
All the Westy owners will be disappointed to hear they can't carry much
more than a couple of sleeping bags and pillows, since they start out
"fully laden." Unless by "fully laden" you mean 1000 lbs below the GVWR
(not "GWVR"), which is reality.
GVWR is the same because they're the same vehicle, with the same
suspension components. Finished or unfinished has nothing to do with
it. You simply can't load as much additional weight into a Westy,
because there's more weight in it to start with. But again, based on
actual measurements, there's still ~900 lbs you can load in the rear of
a Westy and be within spec.
Since you're still arguing that this additional 6% derating is
required, why does your website say Load Index 99 is sufficient? A
Synchro would need Load Index 103 tires.
