The Great Towing Debate Continues...

[Chuck]

Ok, here's one to think about....

anyone seen the ads for the new Chrysler 300? weird looking car. BUT, it has the 340 HP 5.7L Hemi, tow-vehicle-like rear end ratios (I think 3.73 and 3.92 were on the list), a long-ish looking wheel base, rear-wheel drive...max towing: 2000lbs.

Why? unibody? or they just didn't test/configure it for towing, as GT commented was the situation w/ her Kia?

Now, if a certain dealer hooked this thing up to a 34 foot A/S w/ a Hensley, and said "no, really, it tows it just fine!"....I wouldn't be so skeptical.

what dost thou think?

[thenewkid64]

I would say one it is a Unibody chassis. The manufacturers do not want to have the car split in two. The second is whether the transmission will hold up to the severe service that the towing will create. The engine "should" be the same one that is in the Durango. The transmission may also be the same. The Durango is rated to tow 6000 pounds with the 3.92 rear end, the same ratio is available in the 300.

I would say it comes down to the answers on the transmission, and the carrying cap of the car itself. The springs are not designed to carry as much as the durango so you would need to stay small. At the same time there is the warranty from Chrysler if you are exceeding the factory spec as well as the shyster lawyer that will be sure to sue you if you get in an accident (no offense to lawyers, I just have some strong opinions). Will your US based insurance company insure a 300 pulling a 25 foot trailer? That is a question I would want answered before I pulled off the lot!

[Cruiser]

I think I read in a newspaper review that the Chrysler C with towing package was rated at 3800#. Does anyone know if this is right?
We're happy right now with our '94 Roadmaster, but if the "C" turns out to be a good car, we might think about looking for a used one a few years from now...it'd look great towing an A/S.
Doug

[Chuck]

their website was kind of funky, imo...it was difficult to find any info on the subject. But from the main page, if you let the web site pick out a car for you ("which one is right for me?" link...), it eliminates models based on tow ratings. very few details.

anyway, when I looked, it said the chrysler was 2000lbs.

and fwiw, the durango w/ the 5.7 and a 3.92 rear end is way more than 6k. from the same page on the dodge site, it says "up to 8950, properly equipped". it has a 14k gcwr.

which brings me to my next question, which was also touched on in the other thread....

how do they compute these numbers? are they "computed" at all, or are they simply subjective?

weight and balance figures for airplanes (afaik) are actually calculated...of course, a safety factor is built in, but they are based on real numbers. lift exceeds weight...it flys. weight exceeds lift...it don't fly.

doesn't it seem odd that the "ratings" for typical light trucks have seemed to leap up by 2 to 3000lbs in just the past couple of years? has anything really changed mechanically that justifies this, or is this simply a marketing war? We've all seen the Can-Am Intrepid...obviously, it "can" move an enormous trailer...the debateable point is whether or not it should.
So I'm wondering if these numbers are really a reflection of a vehicle's actual capabilites, or simply a reflection of the amount of liability risk the manufacturer is willing to accept.

[bryanl]

Originally Posted by chuck

how do they compute these numbers? are they "computed" at all, or are they simply subjective?

When you mention aircraft you were talking lift and not stress. Most aircraft can handle several g's at max load in various directions. How much is a matter of design and SWAG.

The GCWR is mostly SWAG (Scientific Wild Assed Guess), I think. Even most GAWR and GVWR are nowhere near breaking points. Any vehicle has to be able to take bumps and shock that greatly magnify the stress of load. This is why you can severly overload a vehicle and get away with it most of the time - if you are careful. Tires are more likely to go before anything else does.

Wear and tear are the major issue in weight ratings, I think. Power and fundamental load carrying capacity are generally sufficient to carry the load at highway speed on level roads (unless you get ridiculous).

Wind resistance is a major factor in GCWR and used to be specified in mfg ratings. Stopping should be via the trailer's own brakes (why they are required for any trailers over 3000 lb or so). Acceleration is an issue but that is more a matter of gearing (just ask truckers). Hitch weight is only that of a few people but it located in one place and that can cause handling problems if the vehicle structure cannot accomodate it properly.

Since there are no legal or insurance issues for RV trailer rigs (AFAIK for nominal range rigs weights), weight ratings are more of a guide for safety, longevity, and handling than anything else. Most folks find out real quick if their rig isn't up to snuff because they are unhappy with its handling or performance. So there is a strong feedback loop that promotes proper weight ratings considerations.

I think it very poor practice (and hubris) to impugn others on their choice of tow vehicle or to malign others on how they want to do things. From my experience, most folks want a safe and comfortable ride and do what is needed to make it so. The most dangerous rigs I have seen have been the 'temps' doing a one-shot load transfer or emergency relief.

[Happycampers]

Chuck, I am beginning to think the same thing about the auto makers. I was just looking at my gm manual, I have a 2002 GMC with 5.3 and 3.73 rear and towing pakage can tow 8200 lb. Ok same truck with a 4300 six and 3.73 can only tow5200 lb. so the only difference in these two trucks is lack of towing pakage which you can add yourself and the engine. So the way I see it is if that engine can pull a 32ft Airstream and it can what is wrong with that? I am about to the point of the old saying "if it feels good do it" If you feel good about it and can get it insured go for it. Just don't overload the axle. Marvin

[Chuck]

Originally Posted by Leipper

When you mention aircraft you were talking lift and not stress. Most aircraft can handle several g's at max load in various directions. How much is a matter of design and SWAG.

Ok, so I was over-simplifying. Point is, there are real numbers involved. In my experience, the tables published for take-off distance/performance, (for example) are pretty darned close to reality.

Tires are more likely to go before anything else does.

yeah...and i was recently referencing info about tires from my OM. They're a big part of the tow rating...so how come when I upgraded my factory equipped "P" rated tires to "LT"s, my tow rating doesn't go up? (says this specifically in the OM).

[71_safari]

Tow rating is based almost entirely on horsepower, which is why the ratings have gone up so much lately, as horsepower has gone up. Saw an article that interviewed big 3 engineers about it. They said once they get the number established they engineer the cooling and other systems to meet it - they rarely lower the number to meet cooling.

This was a truck article though, I assume there are other factors at play with cars, such as lack of frame to transfer hitch loads, brake limitations, etc.

-john

[bryanl]

Originally Posted by chuck

Ok, so I was over-simplifying.

oh, don't mind me. I didn't mean any slight. I only took your aircraft idea as providing a good educational contrast for comparing two related but different scenarios for weight ratings. So my thanks are due for that and I am sorry if how I worded things did not reflect this.

Take off considerations with aircraft loading can be calculated but contrast with considerations for fatigue or failure that determine maintenance intervals. Makes me think of the episode last year of a C-130 (I think) fire tanker that lost its wings near Carson City. Weight was within ratings but the g's from a turn and fatigue did it in.

I like John's rundown on the engineers talking about cooling and other systems in trying to figure out ratings. These are considerations for the longer term, usually, and show that the weight ratings such as GCWR, GVWR, and GAWR have more to do with repair and maintenance than they do with catastrophic failure. Hence, they are SWAG's.

The increases in HP and other vehicle characteristics that improve towing handling in recent years have been remarkable. Especially in light of better milage and comfort.

If you want a good example of weight even within ratings creating havok, consider how many transmission failures (from overheating) are caused by backing a heavy trailer into a tough spot uphil. These also cause clutch failures for those with manuals for much the same reason. You can overload your rig even when it appears to be within ratings!

Good gears and driver attention are what it takes to prevent problems like these. And weight ratings are only a first guide.

[Chuck]

so the increases in HP are real, and not just marketing hype?

if the ratings are based mostly on HP...then how come this new chrysler with oodles of HP has such a low rating? could be "unibody", alone, I suppose...but it still seems really really low, considering the size of the engine.

that c130: also, it spent a fair amount of its life flying low over fires. the updrafts created by the fires create a huge amount of stress, beyond that for which the aircraft was designed. I remember seeing that footage; didn't even look like it was turning at the time of the failure. just climbing out.

There was a similar situation a few years ago with Piper Cherokees, when a couple of older models had airframe failures..(wings fell off ). The FAA issued an AD that would have basically forced all cherokee owners to simply throw away their airplanes. (cost of the required inspection would have exceeded the value of many of these older aircraft...or close enough to it. the wing spars are really hard to get at..long story...but they straightened it out). Anyway, the aircraft that had the problem were used for many years as pipeline patrol aircraft in texas. low/slow and extraordinarily bumpy work. (It would be like going highway speed on really rough, pot-holed logging roads w/ your A/S in tow. Even those DuraTorque® axles won't last 30 years under those conditions! ) Not a realistic standard, nor a real concern for 99.999% of other aircraft.