skipnchar wrote: It has to do at least partly with your trucks GVWR. wouldn't make any sense to have a rear axle that would handle twice the weight of the GVWR. There are several OTHER things beyond what you already mentioned that go into establishing a GVWR for your truck including engine cooling, braking power to name a couple. If axle ratings were the only thing there wouldn't even be any NEED to have other ratings like GVWR. As for those who willingly far exceed weight ratings and "have no problems at all" it's very much like running a stop sign. You may do it a hundred times "with no problems at all" but eventually you'll meet up with someone following the law with a very bad outcome.
JIMNLIN wrote: All of our LDT trucks axles are derated by the truck manufacture. With a 25 percent ?? reserve capacity the axle will simply last longer than using it at the axle manufacturers max rated capacity.
This is a paste and copy from a old long gone FMCSA homepage;
NHTSA says this about components of the GAWR:
"Gross Axle Weight Rating is the rated load-carrying capacity of an individual axle and wheel assembly. (It represents the load that may be steadily sustained by the components in the system; i.e., tires, rims, hubs, bearing, axles, brakes, suspension, sub frame, etc. with the GAWR limited by the components with the lowest working rating".
Yep as an example the Dana 60 in my Van has as best as I can determine an axle rating of 6340, springs at 6195 and a RAWR specified as 6084 based on the LT245R75x16 tires which are each rated at 3042.
Larry
Similar situation with my '92 F350SRW pickup. The axle itself is rated to 6250 lbs. The original stock size tires, 235/85-16E's, summed to 6084 lbs, thus the GAWR listed by Ford is 6084 lbs.
dodge guy wrote: Your 3500lb axle rating is the weight rating of the 2 P rated tires. Put the LT`s on it and you will have the weight rating of a compareable F250 axle rating of the same era.
This is a 100% false statement that completely ignores the facts.
The axle used in '99-up F250's, Ford/Sterling/Visteon 10.50" full float, is rated 9750 lbs by the manufacturer. The F250's GAWR set by Ford is 6084 lbs for '99-'04 model pickups.
Putting LT tires on an F150 is not going to equate it's load capacity to that of an F250. The 9.75" heavy duty semi-float F150 axle would be overloaded by 1500-2000 lbs, even going by the higher axle manufacturer's rating instead of the Ford listed GAWR.
The truck's rear axle rating is based on the combination of the axle's factory rating, the tires' rating, the springs' rating, the frame's rating, along with factors for performance and ride quality.
MegaDodge wrote: You have to remember, that on a semi-floating axle, the load is riding on the axle bearing, while on a full floating axle, the load is riding on the inner and outer bearings of the hub. BIG DIFFERENCE. On a full floating axle, the axle shaft itself bears no weight, just turns the hub. Hence the de-rating. Just changing tires will not increase the axle rating by one pound....and overloading it will cause early failure.
MegaDodge,
I have never had someone explain the difference between full float and semi float so well. Thank you for that. I now understand the difference.
Thanks,
Jerem
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Tires indeed. AAM rates my axle at 10,000# but GM lists a RAWR of 6,048. That's exactly the tire ratings of 3,042 per tire. Oddly enough the identical axle in a 3500 SRW will get a higher rating because they used wider wheels and tires with higher load ratings. I believe those tires are rated at 3,400# each so those trucks have a 6,800# RAWR.
KJ
* This post was
edited 02/17/12 04:45pm by LIKE2BUILD *
The axle's weight rating is different based on a whole number of different criteria. The axle itself is but one part of a SYSTEM that makes up any particular vehicle, and those systems have to work in harmony at a particular load rating for the vehicle. As was already mentioned, on a 150, the GAWR may only be 3500lbs, even if the axle is physically capable of carrying more. That same axle in a 3/4-ton may, in fact, be rated to carry more weight. The rating of the axle itself doesn't take into account the axle flange bolt size and pattern, wheel and tire selection, springs, frame, or bed construction or strength. The GAWR, however, does.
dodge guy wrote: Your 3500lb axle rating is the weight rating of the 2 P rated tires. Put the LT`s on it and you will have the weight rating of a compareable F250 axle rating of the same era.
This is a 100% false statement that completely ignores the facts.
The axle used in '99-up F250's, Ford/Sterling/Visteon 10.50" full float, is rated 9750 lbs by the manufacturer. The F250's GAWR set by Ford is 6084 lbs for '99-'04 model pickups.
Putting LT tires on an F150 is not going to equate it's load capacity to that of an F250. The 9.75" heavy duty semi-float F150 axle would be overloaded by 1500-2000 lbs, even going by the higher axle manufacturer's rating instead of the Ford listed GAWR.
Read up on Fords F250 from that era. yes some trucks axle ratings are derived from the ratings of the tires, specifically "P" tires. there are a lot of axles that are rated higher than what they are rated for by the door sticker, specifically because the truck is using "P" tires. Yes I know about all the differences between all the full float and semi float axles. I also know that they are rated higher than what they are actually rated for.
Just stating facts here! you said it yourself with the Sterling axle. it`s rated much higher than what Ford has it rated for.
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dodge guy wrote: Your 3500lb axle rating is the weight rating of the 2 P rated tires. Put the LT`s on it and you will have the weight rating of a compareable F250 axle rating of the same era.
Changing tires will not change the manufacturer's certified limits as stated on the placard. You may have technically increased the rating, but legally it is unchanged.
All true, and never once did I say it was OK to exceed the Manuf rating. just saying that most axles are derated by the manufacturer. see my post above!
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