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Old 06-24-2017, 10:09 PM   #21
CWtheMan
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Originally Posted by MattHelm21 View Post
Do I see an error in your way of doing this calculation? No one is likely to ever be at a published dry pin weight at GVWR. 1805 divided by 11965 is only 15 percent pin weight which is below minimum for a fifth wheel. So doing the math while properly loading this trailer at 20% minimum pin weight, 11965 X .2 = 2393. Using your formula, 11965 - 2393 = 9572. 9572 should be the maximum load on the axles and divided by 4 would be 2393(interesting coincidence pin vs tire?). With the tire max load as 2540 and axles rated to 10160 total, that does leave a margin for error. It isn't great but if every part does its job as designed, these numbers should work with this trailer.
The published hitch/pin weight is a mandatory figure the trailer manufacturer must provide to comply with certification regulations.

I've done some numbers on a lot of Keystone RV trailers and for the fivers the Keystone average is something between 14-17%. It's realistic and obtainable.
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Old 06-24-2017, 10:44 PM   #22
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Originally Posted by busterbrown View Post
This post is very interesting (and informative) as "most" prospective buyers have no clue what defines 'reserve capacity'. I didn't when I purchased a 35' ultra light TT last year.

OEM Trailer King tires were 205 75 14, LRC, 1760 lbs at 50 PSI.

Bullet 308BHS spec'd out with GVWR at 7600 lbs, Dry weight at 6210, and Tongue weight at 700 lbs. A little math shows me that I had very little (if any) reserve capacity left if I pulled a completely loaded trailer at 7600 lbs. 12% of 7600 is 912 lbs of trailer tongue weight. 7600 - 912 = 6688 lbs carried by 4 tires. At 1672 lbs on each tire, I was darn close to the max capacity of each tire when brand new. 88 lbs of reserve (5%) for each tire is slim margins. Using your figures the hitch weight - 700# - is subtracted from the GVWR - 7600# and divided by 2 which equals 6900# divided by 2 = 3450# GAWR axles divided by 2 = 1725# minimal tire on each end of the each axle. ON Keystone's computer model those figures will work. Now weight and balance is in your ballpark.
Here is an excerpt from the FMVSS. They contain the standards each RV trailer manufacturer must comply with. Notice the big red letter word.

"These Federal safety standards are regulations written in terms of minimum safety performance requirements for motor vehicles or items of motor vehicle equipment."

When other recommendations are used the parameters will change. The important words for the buyer of a new unit is “at the time of first sale”. At that time the unit must be sold in accordance with its labeling. After that the new owner is 100% responsible for its weight and balance.

The time to challenge is before the papers are signed.
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