Date: Fri, 13 Mar 2009 16:01:19 -0700
Reply-To: mark drillock <mdrillock@COX.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: mark drillock <mdrillock@COX.NET>
Subject: Re: Tires - Why oh why NOT?
In-Reply-To: <20090313223329.A582C1165C1@hamburg.alientech.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
A good explanation but one more thing. The Vanagon tire spec is for a
tire that can be run 100% of the time loaded at GVWR. The Mercedes could
in theory be loaded on rare occasion to the GVWR but the Vanagon can in
practice be loaded that high often or even constantly. That is why VW
spec'd strong tires for it. The Vanagon was built as a cargo vehicle and
most of them are in that type use around the world, except for the North
American market.
Sure, a near empty van can get along on substandard tires, but don't
ever load 8 people in and run at 75 mph like that poor guy on Samba did.
Wonder if he ever checked his tire pressure?
Mark
Mike S wrote:
> At 03:23 PM 3/13/2009, Chris S wrote...
>> A 1990 Mercedes 560 SEC weighs about 4000lbs. It rides on 205/60 R15
>> tires. The tires are not reinforced.
>
> Incomplete info. What's the load rating of the tire you're talking
> about? More importantly, what did M-B spec?
>
>> My answer is that our tiny concrete-filled 14'' donuts need to be
>> reinforced because nothing else in that size can handle 4000lbs of van
>> and furniture, and the 15'' Mercedes tires and wheels are just fine.
>
> First, neither is "4000 lbs." Both Vanagon and M-B 560 have a GVWR of
> over 5000 lbs. So start there. Ignoring F/R imbalance, you need a tire
> rated at for at least 1250 lbs.
>
> When you actually consider the individual axles, a Vanagon has a GAWR
> (rear) of 2866 lbs. So for rear tires, make that a 1433 lb weight
> rating, static. I think the 560 is closer to 2600 GAWR, so that's a
> 100+ lb lower load rating which the MB needs, right there.
>
> But, in addition to considering just the static weight of the vehicle,
> you must consider weight transfer during cornering, when the outside
> tires carry significantly more weight.
>
> One difference between a van and a sedan is weight transfer during
> cornering. The higher center of gravity and consequently greater weight
> transfer is part of the reason passenger tires must be derated when
> used for truck duty:
> http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=70
>
> VW spec was 185R14C (6PR) (that C means light truck), or optionally,
> 185SR14 reinforced. This is the same as bay buses, and there's a good
> article here: http://www.ratwell.com/technical/Tires.html
>
> Reinforced tires are only necessary if you're using a passenger car
> tire, not needed for a light truck tire, see the comment above on the
> difference.
>.............
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