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
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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