Date: Sun, 10 Aug 2008 21:46:51 -0700
Reply-To: Jake de Villiers <crescentbeachguitar@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Jake de Villiers <crescentbeachguitar@GMAIL.COM>
Subject: Re: Trailer loading and tire pressure testing
In-Reply-To: <489CA011.6080703@gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Go with 20 PSI Mike, and don't look back! :)
Didn't I say this already?
On Fri, Aug 8, 2008 at 12:35 PM, Mike Elliott <camping.elliott@gmail.com>wrote:
> Hi all,
>
> I don't to join the legion of unskilled trailer haulers who find
> themselves in a terrible jam because they were dozing in Trailering 101.
>
> So if anyone wants to check my work to see if I overlooked something, that
> would be helpful.
>
> TRAILER: 270 lbs. (Small fiberglass-bodied single axle utility trailer.
> Empty weight: 270 lbs. This was derived from weight on tongue = 30 lbs,
> weight on one tire 120 lbs. It's safe to say that the other tire had as
> much weight on it.)
>
> PAYLOAD: 218 lbs.
>
> TOTAL COMBINED WEIGHT: 488 lbs.
>
> The rule of thumb seems to be to have 10% to 15% of the gross weight on
> the tongue, so I balanced the load to get 55 lbs on the tongue.
>
> TIRE PRESSURE
>
> Too much pressure = bouncy ride, too little = hot sidewalls and possible
> kablooey. Each tire is carrying (488 - 55)/2 = 240 lbs. These tires are
> ST175/80R13, and according to the load inflation chart at
> http://tinyurl.com/6lg2oy 15 psi is more than enough. Refer to the chart
> if you don't believe me -- these are beefy tires for such a little
> trailer. Heck, 15 psi is good up to 670 lbs per tire.
>
> So I aired each tire to 15 psi and took the loaded trailer for a 7 mile
> ride, half of it on the freeway. At the end of the ride, the sidewalls of
> the van's tires (aired to spec) had risen to 97F (ambient here is around
> 76F), and the sidewalls of the trailer tires read about 90F. This suggests
> that the tires are not underinflated, which is in agreement with the load
> inflation chart.
>
> However, the pressure in each tire had risen to 20 psi, a 33% increase.
>
> A list member had p-mailed me a couple days ago about a tire pressure rule
> of thumb: if the pressure goes up more than 10% after a fast 5-mile drive,
> the pressure is too low.
>
> So...according to the rule of thumb, the tires are underinflated.
> According to the chart, they are nowhere near being underinflated.
> According to the comparison to the sidewall temps of the van's tires, they
> are not underinflated. Anyone want to comment on that?
>
> Oh -- by the way, the trailer towed like a dream. No side to side
> oscillations which indicate that there is too much weight to the rear, and
> no excessive bouncing. It followed along like a little sweetheart.
>
> --
> Mike "Rocket J Squirrel" Elliott
> 71 Type 2: the Wonderbus
> 84 Westfalia: Mellow Yellow ("The Electrical Banana")
> 74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
> KG6RCR
>
--
Jake
1984 Vanagon GL
1986 Westy Weekender "Dixie"
Crescent Beach, BC
www.crescentbeachguitar.com
http://subyjake.googlepages.com/mydixiedarlin%27
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