Date: Sat, 14 Mar 2009 14:32:19 -0400
Reply-To: pdooley <psdooley@VERIZON.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: pdooley <psdooley@VERIZON.NET>
Subject: Re: Tires - Why oh why NOT?
In-Reply-To: <D99764C6AC174F0EBCE23E902FBC8618@mike2d93581d7f>
Content-type: text/plain; charset=us-ascii
Mike,
Apparently the weight bias issue has been shot down already, so please
explain the polar moment of inertia part.
It's been a long time since my engineering classes, so I looked it up.
From what I found, the polar moment of inertia is a measure of an object's
ability to resist torsion.
You seem to be implying that a weight imbalance will affect the vehicle's
torsional stiffness.
Please clarify.
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Mike
Sent: Saturday, March 14, 2009 10:48 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Tires - Why oh why NOT?
The imbalance by the rear-biased weight, and a resultant high polar moment
of inertia during evasive maneuvers (or during a tire blow-out), is surely
the main reason for the C-load sidewall requirements, as evidenced by the
tire pressure requirements (high overall and even higher in the rear).
No passenger tire is rated or able to withstand those high pressure
settings. If you inflate a passenger tire to 44 - 48 psi, it will make it
form a different shape, causing the tread to lose total contact with the
pavement, as well as unduly stressing the carcass and ultimately causing
tread seperation and sudden and possibly catastrophic failure. All this
will likely occur at the worst possible moment, like when you've got 8
people in the van and going 75mph down the highway.
If you've never experienced a high-speed tread separation, I can tell you
it's the most out-of-control feeling you'll ever experience. Rear tire
incidents are much worse than on a front tire, due to being able to move the
steering wheel to fight a front tire blow-out. A rear tire blow-out
controls you, not vise-versa!
Also, any tire retailer that sells and/or installs the wrong tire for your
vehicle, can be held liable in court for the damages/ injuries/ deaths
caused by it.
To take it one step further, if your state inspection sticker passes with
the wrong tire(s) installed, they too could be held liable for not rejecting
it as a failure.
Mike B.
----- Original Message -----
From: Mike S
To: vanagon@GERRY.VANAGON.COM
Sent: Saturday, March 14, 2009 10:00 AM
Subject: Re: Tires - Why oh why NOT?
At 08:58 AM 3/14/2009, Chris S wrote...
>Now, let's compare some more.
>
>I once had a 1993 Ford Aerostar. Its curb weight was 3400 lbs and it
>could carry 7 passengers. No where did the manufacturer specify
>reinforced tires. The stock 215/70 R14 tires, which fit the Vanagon,
>have a max load rating of 1554 lbs. The tires are NOT reinforced.
That's not a standard load rating:
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35
Would that be the 1993 Aerostar talked about here?
http://www.allworldauto.com/comments/1993_ford_aerostar_comments_and_complai
nts_24771.html
Where the following comments have been made:
"Tire blew out on interstate, entire side. was driving at normal speed
in normal conditions."
"Tire blew out, when vehicle stopped tread was seperated from rest of
tire."
"my front left tire suddenly blew out."
"the left rear tire suddenly went flat"
"failed with a tread separation blowout"
"tread coming off tire"
>A 1991 Vanagon GL has its curb weight listed at 3400 lbs. But somehow
>its tires are required to be reinforced.
You're not convincing anyone that you know more than the factory
engineers. Why would you presume to apply Ford specifications to a VW?
It would just as valid (that is, completely invalid, although quite
obviously safer) to go the other way. As has been pointed out, VW never
equipped the Vanagon with tires having a capacity of less than 1609
lbs. (load rating 97), although they could have saved money by doing
so.
Hey, I've got a set of el-cheapo 185R14 passenger car tires, with rims,
which the PO had on. Want to buy them cheap?
