Date: Sat, 9 Aug 2008 13:43:15 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Trailer loading and tire pressure testing
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=response
i think you said the max inflation pressure listed on the side of the tires
was 35 psi ?
anything like 15 or 20 psi sounds way way too low for a 13 inch tire to me.
I'd do 25 psi cold, and not worry about it.
I heard another 'trucker's rule' about hot tire pressures.
'never let air out of a hot tire' .............the idea being, I believe ,
is that you don't now how low it will be once it's well coooled off.
So I just set them at something reasonable cold,
and drive.
If things are harsh or bouncy, then I let some out, 3 psi at a time say.
works for me !
I've towed trailers and vans and cars just countless times, for decades.
I think you're 'trying to hard' or being obsessive.
I suggest put 24 psi in them cold.......nice even # that.........and head on
out.
Super that you did a test drive !
I always carry a spare tire for trailers or anything towed too.
scott
----- Original Message -----
From: "Mike Elliott" <camping.elliott@GMAIL.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, August 08, 2008 12:35 PM
Subject: Trailer loading and tire pressure testing
> 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
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