What makes a tow rating?

[180shabah]

Re: What makes a tow rating?

why and how, do they tow with smaller cars in Europe.

They don't have our overactive legal system.

Up to an including 3K# in MD does not require brakes.
No annual insp. in MD on anything.

Noted, thanks.

 

[avenger79]

Re: What makes a tow rating?

Just to re-connect this to my initial question. Yes, all of those things matter, but I guarantee I can find specs where torque is lower on one truck and the tow rating is higher. My favorite example again is the Toyota . . . So if those three things are what matter (they do) why are there multiple examples of the opposite? So, yes, those things are extremely important to you and me, but they don't seem to determine tow ratings at the OEM level, yet you and I all refer to them endlessly as gospel. Which leads me back to marketing . . .

BTW, Duallies have LOWER tow ratings than their single wheel counterparts . . . I just went through the Owners Manual for my 2008 GMC and it is what caused me to post this thread. IMHO, GM/Chevy sits in a room and says, "OK, max GCVW is gonna be 13,000 lbs on our half tons with a 5.3 V8 & 3.73 rears." So then, if curb weight for the single cab with a short bed is 5000 lbs, then the tow rating is 8000. If a crew cab is 5500 lbs, then the tow rating is 7500. They do the same for the 2500s and the 3500s. Dually is heavier = lower tow rating.

And this example (loosely based on the data I just pulled from the Owners manual that covers all 2008 GMC pickup models) is why I have asked this question. We all would be more comfortable with the Dually setup, yet it has a lower rating . . .

It's a combo of those, along with other factors as well. Lower torque but higher ratio would be equal towing. Weight of the vehicle, length, weight bias. I have a 1/2 ton Ford that is set up to pull more then a base model 3/4 ton truck. Keep in mind the 1/2, 3/4 and 1 ton ratings really have nothing to do with towing. They are carrying capacities of those respective trucks.
I think a lot of it is as stated how much the factory is willing to warranty their product for towing. In the final end it's what is your personal comfort zone with towing a load with a particular vehicle. I've seen people pull huge campers with mini vans. Of course I've also seen them with their bumper literally on the road when something broke. Sometimes you get lucky sometimes you don't. I try to stay well under the vehicles rating.

 

[Titanium48]

Re: What makes a tow rating?

If you look up the tow ratings of European cars you'll find two numbers, depending on whether the trailer has brakes. The unbraked ratings are very similar to the ratings for North American cars - around 500 kg (1100 lb), while the braked ratings are usually in the 1000 kg (2200 lb) to 1500 kg (3300 lb) range. It's as if nobody's ever heard of trailer brakes in North America, although just looking at a trailers under 1500 kg might give an outside observer that impression.

The European braked ratings are based on the ability of the combination to get moving up a 12% grade. While grades steeper than 12% are generally rare, it's not uncommon for boat launches to be steeper than that. I wouldn't want to be retrieving a 3000 lb boat with an Opel (Saturn) Astra or Toyota Corolla.

There's also an unofficial guideline suggesting that the trailer weight not exceed 85% of the curb weight of the tow vehicle to reduce the chance of instability. That would put the recommended maximum at around 2000 lb for an average compact car. Still twice the North American rating though.

 

[QC]

Re: What makes a tow rating?

I try to stay well under the vehicles rating.

Which is why I keep going back to the Toyota . . . Let's say you wanted to tow 7700 lbs. That is exactly at my C1500 GMC tow rating, 100% maxed out, not "well under". But . . . if I went with the Toyota Tundra, then I would be "well under" the equivalent 10,000+ rating. So which is safer? Which one is the stouter truck? Why? Is Toyota simply smarter? Or willing to take more risk? Or are they not trying to force you to buy a 2500 that they don't have? Hmmmmmm . . . .

Opel (Saturn) Astra

Or Vauxhall or Holden . . .

 

[Bigprairie1]

Re: What makes a tow rating?

I have had several interesting conversations with various guys about truck capacity including towing. A lot of guys beef up their half tons supposedly to 3/4 ton status without know what all makes that truck heavier duty and more capable. You probably have the best experience with this QC but my take on this is simple starting from the ground up...literally.
Tires: Heavier capacity trucks have bigger tires capable of doing more load related work. That even includes more lugs per tire....8 on a 3/4 ton vs 5-6 on a 1/2 ton.
Brakes: Heavier capacity trucks have bigger brakes and stop bigger loads carried or towed by the truck.
Axles: Heavier capacity trucks have bigger axles (& full floating) vs. 1/2 ton trucks which are load bearing. Bigger axles means bigger capacity.
Rear Suspension: Heavier capacity trucks have heavier suspension (usually more leaves and heavier sections) which allows them to maintain load stability when hauling or pulling.
Load Stabilization components: Usually in the form of both heavy duty front and rear stabilizers.
Frame: Heavier capacity trucks have a frame with a larger section modulus than a 1/2 truck and often may be a gauge or two heavier in thickness. This translates into more strength for sure...and usually more stiffness and stability.
Drivetrain: Heavier capacity trucks have drivetrain geared (literally) for working harder. This includes higher numeric rear axle ratios, larger driveshafts, heavier transmissions, and engines often with heavier duty components within them.
Other stuff: Heavier capacity trucks have cooling systems that will allow the truck to work hard safely at lower speeds without heating up etc. Things like multi-row rads (3/4/5) as an example.
One thing you get extra with all of the above stuff....is you get a heavier vehicle...for free. This means its going to be a lot harder for any load to overcome, wiggle or de-stabilize the greater mass of the vehicle carrying/hauling it.
Now, thats my take and my experience on this. I do find it amusing when some guys put some big tires on a 1/2ton...and maybe some helper springs and are convinced it is up to 3/4 ton standards. Nope, not in my opinion.
BP

 

[QC]

Re: What makes a tow rating?

Yeah, I agree with all of that BP . . . I just continue to have a problem accepting that a Nissan Armada is truly a more capable tow vehicle than my GMC Sierra. Nissan may think it is better, or GM may be conservative, but if they were studied side by side I would be amazed if your list above favored the Armada . . .

 

[Bigprairie1]

Re: What makes a tow rating?

Yeah, I agree with all of that BP . . . I just continue to have a problem accepting that a Nissan Armada is truly a more capable tow vehicle than my GMC Sierra. Nissan may think it is better, or GM may be conservative, but if they were studied side by side I would be amazed if your list above favored the Armada . . .

Yeah I'd have to agree. I like the Tundra/Nissan stuff...very high quality stuff, great power trains, etc. However I don't buy the tow rating comparison across the board. Some of it might be related to the Tundra/Nissan people cutting a finer line on their safety factors to make a more positive number.
Its not unheard of. Ford has had a policy for almost 40+ years to always have a higher GVWR rating over GM, period. Check out any GM truck and in the same class Ford will have a similar truck with about 200lbs more capacity...supposedly. I don't think GM pushes their rating limit much....no need, yet.
The Japanese makers are working very hard to try to take market share so I think they might be simply lowering their margin on the load/safety factor stuff. Who knows what anyone of them actually use...70%-170%, you know its all safe either way.
I probably would still trust a full size GM (or North American) truck tho' in a comparison..heck just look underneath one, nice and beefy.
My two bits.
BP

 

[QC]

Re: What makes a tow rating?

Yeah, I agree, and I think it is a significant factor for both the Japanese guys (I almost bought the Tundra) and the Americans that the former do not have 3/4 and 1 ton trucks and the latter do. Why buy a 3/4 ton to get 10,000 lb rating if the 1/2 ton already has it? And why buy a 7000 lb rated 1/2 ton Toyota if you need to tow 10,000 . . .

I almost bought a Cruiser a year ago that had literally been used (the exact boat) in an Armada towing commercial, 27 foot Regal with twins and over 9 foot beam. They had literally towed this thing up into our local mountains and I wouldn't really consider towing it with my truck, let alone the Expedition I had at the time (higher rating than the GMC BTW) . . .

 

[avenger79]

Re: What makes a tow rating?

my only info about toyota trucks is this. I had two of them, I did not like either one. A friend had a 3/4 ton Dodge, sold it to buy a Tundra. Said it was going to be the greatest thing in the world. 6 months later he had another 3/4 ton Dodge. I would not personally attempt to outpull a 3/4 ton truck with a Toyota.
again the rating of the truck is not for towing but for carrying capacity.

 

[QC]

Re: What makes a tow rating?

again the rating of the truck is not for towing but for carrying capacity.

They publish Curb Weight, Payload, GVW and GCVW, and they do some of the math for you and also publish a Towing Capacity (GCVW minus Curb Weight) . . . but yes, the 1/2, 3/4 and 1 ton thing refers to payload. And even that is all over the place as most "1/2" ton's payload numbers are in the 1500 LB range . . .

In the UK they still use this ton stuff to refer to GCVW and somtimes payload. They call their max trucks 44 tonners (metric tons, so 96,800 lbs compared to our 80,000) . . . They are a three axle tractor and three axle trailer for max non-permit capacity. They also call their city trucks a "rigid" or a 7 tonner, but I think that is payload, not GVW We might call it a straight truck or a bobtail.

On tractors alone they say 6x2 or 6x4 or 4x2 and they have 8x4s too. Our typical tractor is a 6x4, but we would call that a "three axle" in the west, but a "two axle" in the east. So who the flip knows how all of that stuff lives and dies. Lorry is pretty much dead . . .

In Australia they have "tri-drives" any guesses what that is?

 

[SuzukiChopper]

Re: What makes a tow rating?

I think you all are trying to over-complicate the issue.

Simple law of physics... "A body persists its state of rest or of uniform motion unless acted upon by an external unbalanced force." Newton's first law is often referred to as the law of inertia. So in other words "every object in motion will stay in motion until acted upon by an outside force."

As wordy as it is... it's very simple. Unless your tow vehicle can put an 'unbalanced' force on what is being towed (unbalanced being greater opposite force then the inertia created by what is being towed), then your tow vehicle shouldn't be towing what it is. Add to that safety of yourself and those around you and you have your answer. It has been proven that a human can tow a big rig, minus the trailer, with just a rope around his waist. So what?

Vehicle manufacturers have more then just 'looking big' to deal with. They also have liability issues, etc. I'm sure when tow ratings are put in place the laws of physics are taken in to consideration as well as some level of 'what do we want to be held responsible for?'.

I guess to add to this, my Saturn SC1... 100hp... will tow my boat. It's rated at 1000lbs MAX (my boat is more then 1000lbs). In fact I towed my boat with it for a year and a half. It's got a ton of torque for the size of the vehicle, couldn't ever leave 4th gear on the highway, replaced brakes more often then city driving... however it would EASILY pull the boat, would easily launch and retrieve the boat and just the fact it's a 5 speed helped with stopping. Why did I buy a Durango then? Because it's a whole lot safer and has more of a chance to stop my boat when I need it. Could I pull a fully loaded, full sized horse trailer with it loaded more then Dodge recommends? I'd say yes, it has a 360 5.9L V8 in it. Would I? Nope, I would like to think Dodge did the research needed to figure out what is safe or not.

 

[Titanium48]

Re: What makes a tow rating?

Interesting you bring up both Newton's first law and towing with a Saturn S-series, SuzukiChopper. A 2400 lb S-series towing a 1600 lb boat has pretty much the same weight ratio as a 3500 lb Ranger towing 2400 lb or a 5200 lb F-150 pulling 3500 lb. Nobody would question the ability of the trucks to pull those loads, but the car is exceeding its rating by 60%. The trucks won't handle better than the car without trailers, why should adding a 2/3 of curb weight trailer to each change that?

I towed my ~1600 lb boat with an SL1 last year and had pretty much the same experience - handles well, maintains highway speed in 4th gear on flat roads, 3rd on moderate hills, no problem with ramps as long as they're not too steep (I'm guessing most of the launch ramps in Saskatchewan are pretty shallow too), but braking was mediocre. You solved the marginal braking problem by buying an SUV. I solved it by putting brakes on my trailer - now I can stop nearly as well with it as without it. The two truck combinations I mentioned above would also need trailer brakes to stop well (and to be legal in many places).

A heavy tow vehicle is a brute force approach to towing safely. It's simple and effective, but there's no free lunch. I get 10 km/L (25 MPG) towing my boat and 15 km/L (38 MPG) without. Most trucks can't get 25 MPG on their own. Careful attention to trailer tongue weight, using weight distributing hitches for bigger loads and good trailer brakes go a long way to maintaining stability, without the gas guzzler penalty.

Towing with the S-series worked well enough for me that when my SL1 died on a road trip to California last August (NOT towing the boat), I bought another S-series to replace it. Went for an SL2 this time though - I figured 24 more ponies and a closer ratio transmission should keep me up to speed climbing the hills when I go to BC. The SL1 was down to 75 km/h on the 8% grades in Rogers pass, but I would have been able to maintain 80 if it weren't for the excessive gap between 2nd and 3rd gear.

 

[QC]

Re: What makes a tow rating?

Excellent points Titanium, and your comments bring me back to my weight question about a 5000 lb truck with a 10,000 lb load . . . Which brakes matter most in that combination?

And if I use your numbers, and SuzukiChoppers Newton stuff, that equates to towing 4800 lbs with the Saturn

To the Durango, why would you buy a 1 ton Dodge pickup if Dodge said you could tow 10,000 lbs with the Durango? And if the answer is "they know the limitations of their vehicles". Then Toyota and Nissan just build better stuff, which I don't necessarily believe, at least not in the sense of sheer brawn. Maybe overall quality is better, but not brute capability.