Date: Mon, 2 May 2016 10:05:46 -0500
Reply-To: Larry Chase <roadguy@ROADHAUS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Larry Chase <roadguy@ROADHAUS.COM>
Subject: Re: Tires! 15" or 14"?
In-Reply-To: <287f01d1a470$41f87770$c5e96650$@busdepot.com>
Content-Type: text/plain; charset=us-ascii
Ron,
Most excellent explanation.
larry
www.roadhaus.com
> On May 2, 2016, at 7:43 AM, The Bus Depot <vanagon@BUSDEPOT.COM> wrote:
>
>> I thought that it would be Intuitively Obvious To The
>> Most Casual Observer that I was Making Reference
>> to SideWall Stiffness, Not Load/Weight Recommendations
>> I thought that it would be Intuitively Obvious To The
>> Most Casual Observer that I was Making Reference to
>> SideWall Stiffness, Not Load/Weight Recommendations,
>> but I Apparently Thought Wrong ~ So Again to Be Clear
>> For You Ron ~ My Point Was -->> >> As SideWall
>> height is Reduced the Need for Stiff SideWalls Also
>> Reduces <<
>
> Your initial point regarded, in your words, "the Tire Spec's that they did
> to the Vanagon." There is no such thing as Vanagon "tire specs" for
> "SideWall Stiffness." In fact there is no such spec in the entire tire
> industry. The spec is for load capacity. Load capacity is in turn increased
> by increasing sidewall stiffness (all other things being equal). VW did not
> lower the load capacity requirements when they moved from 14" to 15" and
> then to 16" tires. Therefore they did not lower the spec for "sidewall
> stiffness."
>
> Contrary to your assertion, they also did not lower the load capacity when
> they moved to lower profile (reduced sidewall height) tires. The stock 14"
> Vanagon tire has a 6" sidewall. The stock 16" Eurovan tire has a 5.3"
> sidewall. Despite its lower sidewall height, the Eurovan's tire load
> capacity requirement actually INCREASED. (The increase itself might be
> attributed to the slight increase in curb weight - 750 lbs - but even if
> adjusted for that, it roughly stayed the same, it did not decrease.) So no,
> reducing the sidewall height does NOT reduce the required tire load
> capacity. To your point, it may change how the tire manufacturer gets these
> (maybe they would need less "sidewall stiffness," this unquantifiable
> parameter you mention, to achieve the same load rating if there is less
> sidewall), but even if it did, so what? That's an unmeasurable value that
> has no bearing on choosing tires. The only spec that matters (or exists) is
> the tire's actual load capacity, which is the bottom line, whether they
> achieved it by sidewall height, sidewall stiffness, "modern technology," or
> magic.
>
> So to summarize, you can change "SideWall height" and "SideWall Stiffness"
> all you want but it doesn't change the VW van's tire load capacity
> requirement one bit. If the van called for tires rated at 1600 lbs load
> capacity before, and you switch to tires with different rim sizes or
> sidewall height, you still need a tire rated at 1600 lbs. (Not according to
> me, but according to the only real experts that have ever weighed in on this
> - Volkswagen themselves, and the National Highway Safety Administration.)
> That is the inconvenient yet incontrovertible fact that some retailers try
> so hard to talk around, to justify hawking tires that don't meet those
> specs. (And that some Vanagon owners try so hard to talk around to justify
> purchasing such tires.)
>
> So if you choose to run tires that VW says are underrated, own that choice.
> It's your van and your life, and you can justify it any way that makes you
> happy. But no amount of justification will change the fact - not opinion -
> that you are running tires that do not meet the safety standards set by the
> people who engineered your vehicle.
>
> Again - <http://www.busdepot.com/details/tires/>
>
> Ron Salmon
> The Bus Depot, Inc.
> www.busdepot.com
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