Air Pressure Scamp / Scamp 13 - Fiberglass RV


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Old 09-07-2015, 02:37 PM   #1
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Name: Ken
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Air Pressure Scamp / Scamp 13

Hi Guys - ready ( I hope ) for first outing - Baltimore to Thousand Islands -
in Acorn / Scamp 13 .

There are stickers above each wheel well stating Max of 20 lbs of air pressure in each tire ...

This seems low to me --

What airpressures are you guys actually running ??

Presently I have the pressure set at 33 which is the same pressure I run my Tundra ..

Instruction appreciated .

Ken Max
tobyboat@verizon.net

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Old 09-07-2015, 02:46 PM   #2
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Name: Norm and Ginny
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I set them at 50 lbs, their maximum pressure.
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Old 09-07-2015, 04:02 PM   #3
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Look at the sidewall and set than at or near the maximum value shown. If you have the correct "ST" trailer tires that will be 50 or 65 PSI. If you have automotive tires it will usually be less.

But, in any case, before leaving read the date codes on the tires. If they are more than 6 years old you should replace them before going on a trip.


Not to forget, if you haven't had the wheel bearings inspected and repacked, put that on the to-do list as well.
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Old 09-07-2015, 05:00 PM   #4
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I run my tires at the pressure that they state on the sidewall.
20lbs seems crazy low but I'm no tire expert. I wonder how old the sticker is and what type of tires the instruction would have been intended for.
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Old 09-07-2015, 06:04 PM   #5
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Trailer tire are best run at side wall pressure (what's printed on the sidewalls) Some of our Scamps will be ok with less but then there's less room if one leaks. Some, if not all, trailer tire manufacturers say to run the pressers at side wall indications.
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Old 09-08-2015, 05:35 AM   #6
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There should be a recommended tire size as part of the sticker. The pressure choice the trailer manufacturer provided should allow the recommended tire to carry the axle GAWR. Do you have the recommended tire? What does you trailer actually weigh (per side is ideal)? If you don't have the recommended tire you'd have to look up the load vs. inflation chart for the tire size (available at the tire brand's site).

When picking inflations industry guidelines say you should de-rate P-metric tires when they are used on a trailer (a “P” at the front of the tire size on the tire). I prefer ST tires. Some like LT tires, neither of which have to be derated like P-metrics do.

Inflating trailer tires to the maximum on the tire sidewall does no harm, other than a harsher ride for the trailer contents, and likely provides a load carrying cushion if you don’t have actual trailer weights.
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Old 09-08-2015, 07:19 AM   #7
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As the op is indicating that he has an Acorn/Scamp (c. 1976?) any stickers thereupon are pretty much out of date. I would go with current Scamp recommendations for new 13'ers.


FWIW: P=Passenger Car tires, LT= Light Truck tires ST= Special Trailer tires
Actual words may be different, but that's how it turns out.


While I oppose using P-metric type tires on trailers, maybe Steve can provide a link to the "industry guidelines" he mentioned for derating P-metric tires when used on trailers, so those that do, or want, to use them can have some indications of what needs to be done.
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Old 09-08-2015, 07:54 AM   #8
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The load/inflation table wouldn’t have changed in those years but finding the particular tire size from an older vehicle might be difficult as the industry has gone to metric sizing over time.

The industry group for tires, wheels, valve stems, tubes, etc. is the Tire & Rim Assn. In the Light Truck section, Page 2-03 of the 2014 association handbook states (as it has for years);

"Passenger tires – When a passenger tire is installed on a multi-purpose passenger vehicle, truck, bus, or trailer, the tire’s load rating shall be reduced by dividing by 1.10. The sum of this new reduced load rating of the tires fitted to an axle shall not be less than the gross axle weight rating (GAWR) of the axle system as specified on the vehicle’s certification label."

It may be a chicken or the egg type discussion but it’s not surprising that section S4.2.2.2 of federal regulation F/CMVSS 571.110 states:

"S4.2.2.2. When passenger car (P-metric) tires are installed on an MPV, truck, bus, or trailer,
each tire's load rating is reduced by dividing it by 1.10 before determining, under S4.2.2.1, the
sum of the maximum load ratings of the tires fitted to an axle."

You-all will have to find your own access point I’m afraid. For at least the federal regulation that shouldn't be too hard.
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Old 09-08-2015, 08:14 AM   #9
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This is an interesting discussion as it has been a major topic of conversation between my husband and I for the past four days. When we bought our Scamp in May, the RV place we bought it from put brand new tires on it that say 50 PSI on the sidewall. However, they only inflated them to 35 PSI. We proceeded to put roughly 4000 miles on those tires over the summer, at 35 PSI. (For what it's worth, the tires on our Toyota Highlander also say 65 PSI, but the tire place refuses to air them up past 38 PSI, even when asked to do so).

This past Thursday, my husband decided to air them up to 48 PSI before bringing the trailer home from the storage lot so I could pack it for a 1000 mile round trip camping trip. By the time he got it home, it had bounced so much it actually broke the screen door frame away from it's screws. (It's a ten minute drive, through residential streets, so max speed was 35 MPH) We lowered the tires to 40 for the drive out to Nebraka, which kept stuff mostly in place, but thus began our long conversation about actual tire pressures.

What I'm seeing so far, is to go to the max, but it seems like that is way to bouncy for our trailer. We have ST175/80R13-6 Supercargo Trailer Tires. Any thoughts on this? Our bearings are new and the axle was replaced about five years ago.
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Old 09-08-2015, 09:08 AM   #10
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As you may have discovered from the replies to your question, there are two schools of thought on tire inflation, and each has its proponents & defenders.

The first is to inflate the tires to their sidewall maximum pressure ratings (assuming that the wheels are rated for that pressure). This provides the maximum weight rating of the tire, reduces flexing which may reduce heating, and provides a safety margin if you have a small leak.

The second is to use tire manufacturer tables to match the inflation to the weight on the tire. For example, here is Maxxis's Trailer Tire Inflation Table. The lower pressures (if your trailer weight allows) will provide a softer ride, and may provide a better tire to road footprint resulting in more even wear. It will require better monitoring of tire pressure since going too low will result in tire overheating.

Which method you choose is up to you - I don't believe there will ever be a consensus on which is correct. I've had manufacturer's representatives from the same company, RV dealers & service workers, and tire salesmen support each method, depending on who you talked with.

Personally, I inflate the ST205/75R15 D range tires on my Escape 17B to 50 PSI. Maximum inflation on the sidewalls for the D rated tire is 65PSI, however 50 PSI is well over the weight on the tires, and I've been told by the trailer manufacturer that the wheels are only rated at 50PSI. In any case, I've put close to 70,000 miles on the trailer, the first 20,000 on Goodyear Marathons, 30,000 on a set of Maxxis 8008's, and 20,000 (so far) on a second set of Maxxis 8008's.
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Old 09-08-2015, 09:13 AM   #11
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Hmmm Sounds to me like the selling dealer knew something that they didn't want you to know. I have towed a Scamp 13',(with a screen door) a Lil BigFoot 13' and a Compact-II 13', for 10's of thousands of with the tires always at 50 PSI and have never seen anything happen that could be related to the tires being to "hard".


BTW: If a tire dealer told me that they would not inflate my tires to the specification on the side wall for carrying the rated weight, (without a very good explanation such as they weren't a factory specified standard or optional size) I would look for another tire dealer.
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Old 09-08-2015, 09:17 AM   #12
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The label on my late-model Scamp specifies ST175/80R13 tires inflated to 50 psi maximum. We run 45 psi loaded. I haven't noticed any unusual effects running empty at that pressure.
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Old 09-08-2015, 09:18 AM   #13
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BTW: If a tire dealer told me that they would not inflate my tires to the specification on the side wall for carrying the rated weight, (without a very good explanation such as they weren't a factory specified standard or optional size) I would look for another tire dealer.[/QUOTE]

As it happens, both the Toyota dealership AND Discount Tire, refuse to air the tow vehicle beyond 38 PSI, and have since we bought it in 2011, both for the original tires and for the second set we are on (we drive a lot! The tow has 130,000 miles on it). It seems very odd to me. A few times my husband has inflated them himself to above that, because he does get better gas mileage but it also makes the ride MUCH harder for us as passengers.

I think the screen door was installed by the previous owner, not the factory, so I'm not sure it was ever installed correctly. We also have our little camper very, very lightly loaded, so wondering if that makes a difference.
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Old 09-08-2015, 09:34 AM   #14
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Quote:
Originally Posted by emij View Post
As it happens, both the Toyota dealership AND Discount Tire, refuse to air the tow vehicle beyond 38 PSI, and have since we bought it in 2011, both for the original tires and for the second set we are on (we drive a lot! The tow has 130,000 miles on it). It seems very odd to me. A few times my husband has inflated them himself to above that, because he does get better gas mileage but it also makes the ride MUCH harder for us as passengers.
.

My first guess as to why the car dealership and the tire store did not inflate to max pressure is they think the trailer weighs much less than it actually does.... a common misconception.

What year is the trailer? I see you purchased it in 2011 but I see it had a new axle 5 years ago which suggests this is an older trailer. How old are the wheels? What do they have stamped on them as to Max pressure. If they are the original wheels perhaps the worry is they are so old they are not rated for anything more than 40 PSI.
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