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Date:         Sun, 31 Oct 2004 12:00:33 -0800
Reply-To:     "Todd P. Last" <Rubatoguy@COMCAST.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Todd P. Last" <Rubatoguy@COMCAST.NET>
Subject:      Re: Largest diameter wheel.
Comments: To: John Rodgers <inua@CHARTER.NET>
In-Reply-To:  <418540DF.1000304@charter.net>
Content-Type: text/plain; charset=windows-1252; format=flowed

Good point, as you increase the surface are of the tire, the weight on each sq. inch. will be reduced - making it easier to break traction. Wider tires also tend to make the contact patch more rectangular (shorter front to back) compared to a smaller tire (with the vehicle weight constant.).

I have Michelin XCA's as well and agree, they are great dry tires and wear like steel. (I have 25K miles on mine and they look virtually brand new as far as treadwear.) But they are not for wet driving - they slide easily on wet roads anytime you make abrupt steering or braking inputs. Interestingly, these are no wider than the tires they replaced on my Van (Michelin MXT's) So I have to assume that the difference is a combination of the stiffer sidewalls, harder rubber compound, and hi-way tread.

Todd '88 Westy

John Rodgers wrote:

> 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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