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Date:         Sat, 9 Aug 2008 13:55:34 -0700
Reply-To:     Mike Elliott <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mike Elliott <camping.elliott@GMAIL.COM>
Subject:      Re: Trailer loading and tire pressure testing
Comments: To: Scott Daniel - Turbovans <scottdaniel@turbovans.com>
In-Reply-To:  <086101c8fa60$8fc7a790$6401a8c0@PROSPERITY>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi Scott,

Hmmm. The chart at http://tinyurl.com/6lg2oy says that 15 psi correct for 670 lbs per tire. I'm way under that, even. The tires are rated to 1360 lbs at 50 psi.

Maybe you're right -- I should ignore the chart and just put 25 psi into the tires.

You wrote, "I think you're 'trying to hard' or being obsessive."

I resemble that remark!

-- Mike "Rocket J Squirrel" Elliott

On 8/9/2008 1:43 PM Scott Daniel - Turbovans wrote:

> 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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