Date: Sun, 31 Oct 2004 13:45:35 -0600
Reply-To: John Rodgers <inua@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <inua@CHARTER.NET>
Subject: Re: Largest diameter wheel.
In-Reply-To: <BDAA77D1.4A26%wetwesty@tactical-bus.info>
Content-Type: text/plain; charset=windows-1252; format=flowed
I cannot address the issue of what size (diameter) rim that can be used,
but here is a caution.
You do not want a tire on a Vanagon whose road contact surface is really
wide. While wide tires may look "Macho", they are crap when the chips
are down and you need serious friction on the road for vehicle control.
There is a functional relationship between the total surface of the tire
in contact with the road, and the amount of weight bearing down on that
tire contact surface. If that relationship is upset by changes in either
weight or tire contact area, then performance is degraded and may be
responsible for an accident of the skidding kind. Generally speaking,
and this is "Generally", a wider tire will have have less traction and
be more likely to allow the rear of the vehicle to de-stabilize
resulting in a skid. Not a good thing most of the time. Although I have
had in my driving career at least two occasions where being able to
easily induce a skid saved my butt by allowing me to get out of the way.
The relatively narrow tire specified for the Vanagons was done so for a
reason. Vanagons really are "trucks" by nature, and as such have widely
variable weights at different times. A narrow tire with a high load
rating at the road will be a more controllable vehicle in varying
weather conditions, but most especially in wet weather conditions.
Be especially careful about the tread type. I run Michelin XCA's
205-75R14's. I find that in dry weather it is a great tire. But it is a
truck tire. And as such it doesn't have a very aggressive tread design.
The tire relies on that heavy load ratios of the bigger trucks for the
friction it needs for stopping and also to avoid skidding. My vanagon
simply doesn't have the weight for the tread type. Consequently I have
to be more aware and more careful when driving in wet weather. Don't get
me wrong. I love the tire, but it has it's limitations. Less than the
best aggressive tread is one of those limitations. In this case, with
the loads I carry, the number of grooves in the tire tread is
inadequate, consequently the wide rubber between the grooves in the tire
tend to make the tire want to float on the film of water on the road
when it is raining - hydroplane - So I have to be careful. More weight
would force the water out from under the tread. But I don't have more
weight. What to do, what to do? Increase the number of grooves in the
tread. This allows the narrower rib of the tread to cut through the
water, displacing it sideways and into the grooves of the tire,
resulting is more rubber on the road. Thus the better control.
So it is all a balancing act between rim sized o carry the right, tire,
sized for the best contact with the road, adjusted for weather type, and
load.
We take it all sort of for granted, but rim, tire size, tread type, and
loading are really fascinating subjects and important.
Again, be careful of what you do with tires when you change them.
Regards,
John Rodgers
88 GL Driver
jimt wrote:
>I am just looking for the largest diameter wheel that can fit in the wheel
>well of a 2WD vanagon. And be used of course. Not into adaptors or
>anything else just the diameter or tire sizes and I will compute the
>diameter.
>
>Height not treadwidth.
>Thanks
>
>••••••••••••••••••••••••••••••••••••••••
>jimt
>Planned insanity is best.
>Remember that sanity is optional.
>http://www.tactical-bus.info (tech info)
>http://www.westydriver.com
>
>
>
>
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