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Old 06-26-2012, 06:07 PM   #1
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GOING ALL THE WAY? why wouldn't it be safe?

So I still don't understand why people offer up advise for not towing to the capability of any TV. (myself included) I have been doing some research for myself and it seems most tow capacities are determined by engine size within a brand.

Say the ford F150. engine makes a difference for what it can tow. not taking into account different body styles. That changes things too..

Now when you move up to a F250 or F350 you have a stiffer frame so you can tow more also. But engine size determines different tow capacities here also.

You can throw in a tow package to increase towing. Oil and Transmission cooler.

So back to the original statement. Why would a company give you a tow limit and then not expect you to tow to that limit?

I started a thread on the 80% rule and never got a straight answers for it, other than "it seemed like a good idea."

So again, why do we give advice not to tow to the limits of our TV when the manufacture seems to believe this is a safe limit to take it to.

I would believe they must figure people will tow more and build in some sort of safety margin. Is this crazy for me to think.

When towing my AS I still have a few 1000's lbs left, but have towed it to it's capacity and beyond and not felt unsafe. Climbing 2000 ft up and down a mountain.

As long as you have Trailer brakes, that work well, and you have a working WD and sway control, why not tow to your TV limit? Many don't want a 3/4 ton truck or can't afford one. I would love one, but it's not practical for my family.

Any Ideas?
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Old 06-26-2012, 06:19 PM   #2
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IMPO, you can certainly tow up to the stated tow capacity and load to the stated GVWR. There IS, I repeat, IS a margin already engineered into the specs. I have verified it with our engineers. I WILL NOT, however tell you what that margin is....because some will then tow to that figure and be PO'ed when something wears out prematurely. The margin is more than adequate for those who want to be conservative.

Jason, GCWR is a function of "horizontal" loads...powertrain and braking. The limiting factor could be any component in those systems. GVWR and tongue load forces are limited by "vertical" loads. These could be frame, spring hangers, springs axle housings/shafts (1/2 ton only, typically) hubs, lugs, wheels, tires.

Because of all these variables, there are many specs for 1 truck.

I can't wait for the new tow spec, based on performance, up a hill at a given speed. We will never know the actual capability of the TVs anymore. The new figures are marketing spec for those who just have to drive at high speed while towing.

I have a bad feeling these new specs will arouse discussions which will make the "I can tow my 34'er with my Smart Car..." seem calm.
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Old 06-26-2012, 06:45 PM   #3
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Quote:
Originally Posted by purman View Post
..... I have been doing some research for myself and it seems most tow capacities are determined by engine size within a brand.

Say the ford F150. engine makes a difference for what it can tow. not taking into account different body styles.

Any Ideas?
My one observation (and this applies to the F-150 you talk about) is that in fact the max towing capacity of an F-150 is determined more by gearing, suspension and cooling system specs than by the engine size. Take my 2010 F-150 with a 5.4l engine. The towing capacity of my truck is something like 8300lbs with the gear ratios installed. The capacity increases to something like 11,300 lbs with a taller gear set and suspension changes. In fact the newest engines all make more power and the max towing capacities are exactly the same.

My one thought on the 80% rule is that it just is not wise use "everything you have"..... Speaking as a mechanic, I see what happens to cars when driven close to the max all the time. I prefer not to "hammer" my mechanical stuff...

Bruce
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Old 06-26-2012, 06:48 PM   #4
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Your correct, Rear gear ratio does make a difference in TC. I think number of gears and transmission can also be a factor. There are so many dang options. I would think it would make life easier for the company not to have so many options.

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Originally Posted by Bruce B View Post
My one observation (and this applies to the F-150 you talk about) is that in fact the max towing capacity of an F-150 is determined more by gearing, suspension and cooling system specs than by the engine size. Take my 2010 F-150 with a 5.4l engine. The towing capacity of my truck is something like 8300lbs with the gear ratios installed. The capacity increases to something like 11,300 lbs with a taller gear set and suspension changes. In fact the newest engines all make more power and the max towing capacities are exactly the same.

My one thought on the 80% rule is that it just is not wise use "everything you have"..... Speaking as a mechanic, I see what happens to cars when driven close to the max all the time. I prefer not to "hammer" my mechanical stuff...

Bruce
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Old 06-26-2012, 07:46 PM   #5
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Quote:
Originally Posted by Bruce B View Post
Take my 2010 F-150 with a 5.4l engine. The towing capacity of my truck is something like 8300lbs with the gear ratios installed. The capacity increases to something like 11,300 lbs with a taller gear set and suspension changes. In fact the newest engines all make more power and the max towing capacities are exactly the same.

My one thought on the 80% rule is that it just is not wise use "everything you have"..
You've got that right.

Having worked in marinas and construction where I had no choice in what I had to tow, with what, or even any kind of special hitch, much more is possible with a little common sense and safety than most could imagine looking "at the numbers".

The spec'd towing capacity of my older model f150 with a v6 and stick is 2000lb with 3.08 gears but goes up to 3300lbs with 3.55 gears., I run 4.30.

Just adding an automatic transmission to identical truck (same engine chassis, brakes, axles, tires etc) bumps its spec'd towing capacity to 5500 lbs.

With a V8 it is spec'd at 8700lbs

I think US towing specs reflect more the legal analyses than the engineering ones. Engineers know about fail safe structural safety margins
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Old 06-26-2012, 07:58 PM   #6
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Jason,

By the title of your thread I first thought you were promoting AIDS awareness among the membership.....

Seriously now, I am one that believes that if a manfacturer publishes a Combined Gross Vehicle Weight of, say, 15,200 pounds then I should be able to do that.

Same way as if I bought a house advertised at 4000 s.f. I don't expect it to measure 3000 s. f without legal action pending.

That's why it's hard for me to understand those advocating the 75% - 80% rule.

Sergei

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Old 06-26-2012, 08:00 PM   #7
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The 80% rule is for those too lazy to search out the info to set up the rig appropriately (not that they receive any help from dealers, et. al.) A thumbsucker rule.

At a minimum the rig needs to be weighed, singly, and in tandem. Use those scale derived values to set up the hitch rigging, tire pressure, etc. Know how things work, and learn to adjust properly. This gives confidence.

Where one goes (climate & terrain) determines the level of comfort most will have with a particular rig, and this is leavened by experience. A few trips around the region (150-miles there and back) is different than a 10,000-mile trip.

I rarely enter the highway (several times daily) at even 50-mph, more often am below that. This is not by choice, it's just how the vehicle combination works when fully loaded.

Speed up a hill, or onto the highway is a meaningless problem (baseless fear) where otherwise the TV is up to the job.

Best hitch rigging, best trailer brakes and best brake controller make the usual justifications for a bigger TV without a leg to stand on (especially when one can avoid bad-handling TV's such as all truck based ones).

.
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