blueblood
Well-known member
- Joined
- Mar 16, 2005
- Posts
- 1,082
I have been studying the axle tire load ratio for some time. First, federal regulations require that the ratio be at least 1 i.e. maximum tire load capacity must be equal to axle load rating.
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FMVSS 571-120
S5.1.2 Except in the case of a vehicle which has a speed attainable
in 3.2 kilometers of 80 kilometers per hour or less, the sum of the
maximum load ratings of the tires fitted to an axle shall be not less
than the gross axle weight rating (GAWR) of the axle system as specified
on the vehicle's certification label required by 49 CFR part 567. Except
in the case of a vehicle which has a speed attainable in 2 miles of 50
mph or less, the sum of the maximum load ratings of the tires fitted to
an axle shall be not less than the gross axle weight rating (GAWR) of
the axle system as specified on the vehicle's certification label
required by 49 CFR part 567. If the certification label shows more than
one GAWR for the axle system, the sum shall be not less than the GAWR
corresponding to the size designation of the tires fitted to the axle.
If the size designation of the tires fitted to the axle does not appear on the certification label, the sum shall be not less than the lowest GAWR appearing on the label. When a
tire subject to FMVSS No. 109 is installed on a multipurpose passenger
vehicle, truck, bus, or trailer, the tire's load rating shall be reduced
by dividing by 1.10 before calculating the sum (i.e., the sum of the
load ratings of the tires on each axle, when the tires' load carrying
capacity at the recommended tire cold inflation pressure is reduced by
dividing by 1.10, must be appropriate for the GAWR).
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In looking at a sample from a survey I did of owners of 100 5th wheel units, I found ratios ranging from 1.17 to .85 I should add I'm still working on the data and meaning of various FMVSS statues.
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However, it seems to me that the standard of one is totally inadequate. It assumes the TT is loaded perfectly, being pulled perfectly level, etc. Yet, I look at the design of my new 5th wheel and on the driver side it has all the heavy components -the kitchen with all the appliances and an island with countertops all around of Corian,the living room has fireplace and TV, and the bedroom headboard and shower stall, etc. I haven't taken physical delivery yet so haven't weighed but can it possibly be a balanced weight? I have negotiated with the parties a change out of my tires and wheels to raise the ratio to 1.14 from 1 and am awaiting their delivery at this writing.
__________________________________________________________________________
FMVSS 571-120
S5.1.2 Except in the case of a vehicle which has a speed attainable
in 3.2 kilometers of 80 kilometers per hour or less, the sum of the
maximum load ratings of the tires fitted to an axle shall be not less
than the gross axle weight rating (GAWR) of the axle system as specified
on the vehicle's certification label required by 49 CFR part 567. Except
in the case of a vehicle which has a speed attainable in 2 miles of 50
mph or less, the sum of the maximum load ratings of the tires fitted to
an axle shall be not less than the gross axle weight rating (GAWR) of
the axle system as specified on the vehicle's certification label
required by 49 CFR part 567. If the certification label shows more than
one GAWR for the axle system, the sum shall be not less than the GAWR
corresponding to the size designation of the tires fitted to the axle.
If the size designation of the tires fitted to the axle does not appear on the certification label, the sum shall be not less than the lowest GAWR appearing on the label. When a
tire subject to FMVSS No. 109 is installed on a multipurpose passenger
vehicle, truck, bus, or trailer, the tire's load rating shall be reduced
by dividing by 1.10 before calculating the sum (i.e., the sum of the
load ratings of the tires on each axle, when the tires' load carrying
capacity at the recommended tire cold inflation pressure is reduced by
dividing by 1.10, must be appropriate for the GAWR).
__________________________________________________________________________
In looking at a sample from a survey I did of owners of 100 5th wheel units, I found ratios ranging from 1.17 to .85 I should add I'm still working on the data and meaning of various FMVSS statues.
___________________________________________________________________________
However, it seems to me that the standard of one is totally inadequate. It assumes the TT is loaded perfectly, being pulled perfectly level, etc. Yet, I look at the design of my new 5th wheel and on the driver side it has all the heavy components -the kitchen with all the appliances and an island with countertops all around of Corian,the living room has fireplace and TV, and the bedroom headboard and shower stall, etc. I haven't taken physical delivery yet so haven't weighed but can it possibly be a balanced weight? I have negotiated with the parties a change out of my tires and wheels to raise the ratio to 1.14 from 1 and am awaiting their delivery at this writing.
