Date:         Thu, 3 Aug 2006 01:16:39 -0400
Reply-To:     The Bus Depot <vanagon@BUSDEPOT.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         The Bus Depot <vanagon@BUSDEPOT.COM>
Subject:      Re: 15" Wheels/Tires
In-Reply-To:  <cf4df96f0608021953v220c9775ra0e3f9bcb96e0f36@mail.gmail.com>
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> > Even though like many others I run 15" wheels, I'm not sure 
> > I would agree that "a 15" wheel is the preferred size"

> Larry is in the know  about tires and rims but I have to add 
> that I noticed NO difference or loss of power going from a 
> crappy 14" up to 15" with 225/70R15. 
> 
> Plus:
> Better cross wind stability
> Better ride with larger tires
> Better road grip against hydroplaning and snow slip
> Lower RPM = happy engine
> 
> Cons:
> More money


I don't see how this can be. 

First of all, all things being equal, it is a fact that a THINNER tire will
do better in terms of hydroplaning and snow slip. Therefore a 185R14 is
optimal for this purpose (even better than the 205/70R14 commonly used on
14" alloy wheels, which is why I use 185R14's on my alloys).  Secondly, the
tires you are using are 2" taller than stock, so this would tend to WORSEN
cross wind stability (again all things being equal), throw off your speedo
by 7 percent (which is a fairly sizeable margin), and on a Westy, possibly
make it too tall to fit in some home and parking garages. On the other hand,
you do gain ground clearance (which can be a major plus if you have a Syncro
and go off-roading) and improve dry-road grip by virtue of the wider tire
(at the expense of rain/snow performance).

You can eliminate the last three drawbacks (speedo reading, garage fit, and
cross-road stability issues) by choosing a 15" tire that maintains the same
height as the stock 14" tire. We sell one for this purpose, which is
commonly used on Eurovans; the Vredestein Comtract 205/65R15. Not owning a
Syncro myself (hence no need for increased ground clearance), if I were to
go to 15" wheels that's what I'd use. However there are some drawbacks to
this solution as well, which I will go into later.

As for my next couple of points, let me first remind Vanagon owners that
standard-load passenger car tires are UNSAFE for Vanagon use (as per both
VW's own engineers and U.S government safety standards) whether in a 14" or
15" size. Please read my write-up at http://busdepot.com/details/tires.jsp
before arguing this point. If you are going to respond with anecdotal
evidence such as "I have used car tires on my Vanagon and never had a
problem," then your argument is akin to saying "I smoke a pack a day and
haven't had a problem" or "I never wear my seatbelt and haven't had a
problem."  Take the risk if you choose, but at least admit that you are
taking a risk. So, that being said...

Regarding ride comfort, this is subjective of course. If you are using
inadequately-rated tires (which have insufficient sidewall rigidity), you
may indeed notice a cushier ride, because your sidewall if flexing too much.
You could have gotten the same effect by simply buying taller 14" tires that
had too much sidewall flex.  This may feel cushy, but it can be dangerous
under accident-avoidance conditions (again, see the above link). If a
cushier ride is what you're after, there are ways to accomplish this that do
not involve buying tires with dangerously weak sidewalls. The simplest is to
use a softer riding shock. An oil damped shock like a Boge (or better yet, a
Koni, where you can actually adjust the ride to taste) will give you a
smoother ride than a typical gas-filled shock like a KYB or Bilstein,
without potentially risking your life. 

If your tires ARE properly rated, but taller, you still may feel a softer
(subjectively "better" to some people) ride, because there is more rubber
sidewall to absorb the bumps. This becomes a judgement call. Do you feel
that the advantages (smoother ride, increased ground clearance) outweigh the
drawbacks (speedo error, garage fitment, wind resistance)? If so, as long as
the tires are properly rated, go for it. However you could also accomplish
the same thing without springing for bigger rims, by simply buying a
properly-rated but taller 14" tire, such as our Hankook 195R14 or Vredestein
205R14.

If you choose to increase to 15" rims but want to maintain stock ride height
to avoid the aforementioned trade-offs, this means you must use a
lower-profile tire to offset the taller wheel. All things being equal this
will actually make your ride less smooth. Even a sidewall-reinforced tire
has more flex than a metal rim. So if you are increasing the height of the
wheel and correspondingly decreasing the height of the rubber, you will get
a bit of a stiffer ride. As for whether such a change is better or worse,
again this is subjective. Some people like a more taut ride, others like
more cushion.  Also a lower-profile tire is slightly more prone to blowouts.


As for cost, assuming you are using the correctly load rated tires for your
Vanagon either way, 15" tires are MUCH more expensive than 14" ones.  A set
of Hankook 185R14's will set you back about $75 each. A comparably rated OEM
or name-brand 15" tire will cost at least 50% more per tire.  And that
doesn't include the cost of replacing the wheels.

So that's my take on it. IMO, the only reasons to go with 15" rims is if you
want to increase ground clearance, or love the look and don't mind spending
some bucks to get it. (And I say this as someone who sells 15" wheels.) Some
may disagree with my analysis (after all I'm reopening the "tire thread"
Pandora's box:-), but my position is backed by hard science, not anecdotal
evidence, and I stand by it.  Flame on! :-)

- Ron Salmon
  The Bus Depot, Inc.
  www.busdepot.com
  (215)  234-VWVW

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