Heavy Towing

Topic: Heavy Towing (Read 1391 times) previous topic - next topic

Heavy Towing

October 06, 2011, 01:27:46 am

Thinking about replacing our Subaru TOAD with a full size pickup. Has anybody ever pulled a vehicle in excess of 7500 pounds? Should I expect a big hit in mileage? Currently, I average 10.1 MPG towing the 3300 pound Subaru.

Re: Heavy Towing

Reply #1 – October 06, 2011, 02:21:15 am

I know a few FT owners who tow heavy loads eithe with a trailer or a full sized pickup and an atv in the back. Mist are getting in the 8 to 9. I tow a wrangler and get in the lw 8s but the mountain driving osts me a bit. On the flats in the midwest I am in the high 8s. So you will lose a but towing but not too much since you are adding only 4k and had some rolling resistance before. I get better miage not towing but tat has only hapoened on a couoke trips over the ast ten years.

Re: Heavy Towing

Reply #2 – October 06, 2011, 11:10:25 am

I too have been thinking four door PickUp to replace my Outback so I will be interested in the answers you get as well.

Re: Heavy Towing

Reply #3 – October 06, 2011, 12:02:42 pm

I'm towing a 4,400 lb XTerra and it's fine when on the flats. When the road tilts up I have to slow down and watch the temp gauge adjusting speed to keep from overheating. I've had a couple of occasions to drive in the hills without the toad and was pretty surprised at how much better Big Agnes did. She felt like a young girl again.

I guess what I'm saying is be prepared for a performance and milage hit. If you're ok with that go for it.

see ya
ken

Re: Heavy Towing

Reply #4 – October 06, 2011, 12:13:12 pm

The answer to what effect more weight has on MPG is IT DEPENDS.

Straight physics dictates that weight is not that critical at steady highway speed on flat ground.

On grades, weight becomes a very important factor in determining not only performance, but also MPG.

So, if you live in FL, expect much less impact than if you live in CO.

Brett

Re: Heavy Towing

Reply #5 – October 06, 2011, 12:45:49 pm

Another way of looking at this, would be to consider the engine HP vs the total weight of your vehicle comb.
In simple terms, the smaller the engine and the larger the weight, the slower you are in the hills, on flat land not much to concern you, but as you get into the mountains, things start getting more interesting, slow on the up grades, while on the down hills, brakes with either retarder or Jake setup is a real concern.
Heat is another concern both going up and down, can you control the heat issues.
Goes back the the weight part of the weight and balance issue, as the weight goes up, the performance does down.
FWIW

Re: Heavy Towing

Reply #6 – October 06, 2011, 01:25:13 pm

Our 1997 U295 has a measured gross weight of about 28,000#. The engine is a C8.3-325 with a Banks Stinger. We normally tow an old Jeep Cherokee that weighs 4,180#. The only time I drive the coach without the Jeep on is to take it from home to dump waste tanks, fill the fuel tank, or give it a bit of exercise in case it has been sitting. We have had no overheating problems with the engine or transmission.

We measure about 7.1 mpg, based on miles/fuel pumped into the tank. The fuel burned includes fuel consumed by the generator. We drive at 65 mph when conditions permit. Our mileage is lower than what most people report. The exhaust is clean, temperatures are good, and performance is acceptable. We move about 98.5#/HP according to the OEM engine rating. If the Banks Stinger gives a 25 HP boost, we would be moving about 91.5#/HP.

There is a difference in the feel of driving without the towed vehicle. The coach is a bit more "nimble" without the additional 15% of additional weight. I expect I would feel an additional 3,000# (~9% of gross combined weight) over the current towed weight. It would mean using a bit more fuel, and being a bit more sluggish when acceleration is required. Stopping the combination would be a bit different as well. That difference would depend on whether the brake system on the towed is proportional or binary. If I were towing something weighing more than 25% of the weight of the tow vehicle, I would want proportional braking.

I would not want to tow more than 6,000# with our coach. The difference between our GVWR and GCWR is 6,000#. Also, it is my understanding that the hitch apparatus before 1999 was built to handle up to 6,000# of towed weight. Tongue weight is not an issue if you are towing a vehicle with four wheels down.

As Dave M says, those are my experiences and opinions FWIW.

Re: Heavy Towing

Reply #7 – October 06, 2011, 01:42:26 pm

J.D., Interesting point, just ran the numbers on my setup, coach and toad 36,000 lb.
So that gives 72lb/hp, 23.2.lb/ft lb and most interesting 18lb/ft lb retarder alone.
One reason I love the setup in this coach towing the F150 w/ATV.
FWIW

Re: Heavy Towing

Reply #8 – October 06, 2011, 02:16:12 pm

It sounds like 100#/HP is a reasonable minimum ratio for acceptable performance in DP RV. We have the testimony of a partially recovered "power junkie" that 72#/HP is lovable.

I took my "little" motorcycle to a track on Tuesday for some fun riding and skills work. Compared to most bikes at the track, it is heavy and not especially powerful. It is a pure stock "naked" or "street" bike. I just ran some numbers on it. Including my weight, it is somewhere under 6#/HP. But it doesn't have a refrigerator, toilet, shower, bed, ...

Nor will it tow anything.

Re: Heavy Towing

Reply #9 – October 06, 2011, 02:37:31 pm

Think about a average 18 wheeler at 80,000 lbs with a 500 hp engine, that is 160 lb/hp.
Soo, a 500 hp truck is a little above average, a lot of trucks are running in the 400-450 hp range. Just some thoughts. I feel a drivers ability and experience goes a long way in being able to handle the higher weights, keeping cooling, stopping etc under control. Truckers know they can not run 70 mph and stop like a car or pickup truck.

Truck drivers have been to schools to get the feel of the weight they are driving, they have to prove they have a few years of credable experience or gone thought a certified drivers training school.

Unlike many RV owners who show up with the money, crawl behind the wheel and think they have it all under control only to find driving a desk is not like the RV, so it gets costly if not dangerous for them, some body damage, some burnt up brakes and a bad case of nerves

Heck, very few DP units can stop with a Foretravel with retarder for that matter. but start adding weight and things start changing, like passing ability and of course stopping the critter.
In my case, the 36' 320 can carry the weight of the toad and still be under the GVW rating, no matter you best have toad brakes from a legal point of view.
Everyone has an opinion, this is one of mine.

As usual FWIW

Re: Heavy Towing

Reply #10 – October 06, 2011, 10:05:17 pm

Very pertinent discussion as the wife and I are talking about getting a toad. She is tired of following behind in our visits to Gainesville. We have a Suzuki XL-7 but it is 2WD and cannot be towed four down. She wants a Wrangler but I think it is too heavy for the 250hp CAT 3116. Now that she now longer needs to transport kids, she'd like a sports car but not a sporty econo car. We're not getting a Vette or something like that either though. She is willing to do the Wrangler but likes the bigger 4 door. I've found a 4WD Suzuki Grand Vitara but she really doesn't want essentially the same vehicle (minus the 3rd row seat). I've been very happy with the XL-7 since new in 02. I drive a company truck so her car would be the toad. I don't want to add another vehicle to the mix. I had considered having a driveshaft disconnect installed by they don't make one for the XL-7. I could probably put one on my 63 Falcon Sprint convertible (Ford-o-matic 2 speed) but don't want to use it for obvious reasons...though it would be handy to take the car to far flung events like the All-Ford at Carlisle, PA every summer. Anyone towing something small and sporty?

Re: Heavy Towing

Reply #11 – October 06, 2011, 11:58:08 pm

Do these calculations take into consideration that the maximum efficiency of a diesel engine is about 80%? Thus, according to Cummins mechanics, the most hp I can expect from my 300 hp C8.3 Cummins is 240 hp. Their dyno tests confirmed this. Therefore, instead of 28,000/300 hp (93 lb/hp) it would be 28,000/240 (116 lb/hp).
Am I missing something?

Re: Heavy Towing

Reply #12 – October 07, 2011, 01:11:46 am

Quote from: Dave M – October 06, 2011, 02:37:31 pm

Think about a average 18 wheeler at 80,000 lbs with a 500 hp engine, that is 160 lb/hp.
Soo, a 500 hp truck is a little above average, a lot of trucks are running in the 400-450 hp range.

But many of the company rigs out there are Day Cabs with the lowly M11 or ISM 330/370 Cummins with 10 speeds pulling the same weight under the same conditions or worse, cause they are on back roads making local deliveries. That 330/370 switches back and forth between the two horsepowers as needed.

Re: Heavy Towing

Reply #13 – October 07, 2011, 01:27:43 am

Quote from: Don Hay – October 06, 2011, 11:58:08 pm

Do these calculations take into consideration that the maximum efficiency of a diesel engine is about 80%? Thus, according to Cummins mechanics, the most hp I can expect from my 300 hp C8.3 Cummins is 240 hp. Their dyno tests confirmed this. Therefore, instead of 28,000/300 hp (93 lb/hp) it would be 28,000/240 (116 lb/hp).
Am I missing something?

Depends on where it is measured. Is it measured at the crankshaft or the rear wheels? It will have more torque at the crankshaft and less at the rear wheels.

Re: Heavy Towing

Reply #14 – October 07, 2011, 07:52:48 am

Small, sporty, economical to buy and run, fun to drive, lightweight=Mazda Miata. My wife has a BMW Z3 that would fit the bill nicely but just too nice to drag behind with 23K miles and custom paint. Those Miatas are bulletproof.

Chuck

Re: Heavy Towing

Reply #15 – October 07, 2011, 08:42:47 am

Honda 2000? very highly rated by consumer reports

Re: Heavy Towing

Reply #16 – October 07, 2011, 10:08:26 am

I would go with the Wrangler. You will have a convertible and a great toad that can go anywhere. I was at a rally and they had a off road adventure to one of the top ten off road courses in the country. I went in my stock wrangler and had a great time and could go everywhere the built boys went but two places....

Also, when we go to the beach I can take it out on the beach and down by beach to a quiet location.

In Yellowstone you have to get off the road if you stop to see wildlife. You can take the wrangler right up or off the road where a car can not go.

I also have been out and there has been snow on the ground and you can still go where you want though a couple winters ago, I needed the big diesel truck to push thru it as it was taller than my hood.... But that is a rare reason for owning one if you have a motorhome and go south for the winter.

Re: Heavy Towing

Reply #17 – October 07, 2011, 11:48:15 am

John, it just occurred to me that you have a wrangler and a bad back. How does that work out?

I can tell you from experience now that when they tell you to take better care of your back, they mean it. They told me after my 2008 Lumbar surgery if I didn't take better care of my back I could end up loosing my ability to even walk in the future and as you know, that almost happened in August.

Re: Heavy Towing

Reply #18 – October 07, 2011, 12:08:42 pm

2011 Chevy Equinox 2wd, 3800 lbs with roadmaster 9160 braking system

Re: Heavy Towing

Reply #19 – October 07, 2011, 02:51:30 pm

Quote from: Don Hay – October 06, 2011, 11:58:08 pm

Do these calculations take into consideration that the maximum efficiency of a diesel engine is about 80%? Thus, according to Cummins mechanics, the most hp I can expect from my 300 hp C8.3 Cummins is 240 hp. Their dyno tests confirmed this. Therefore, instead of 28,000/300 hp (93 lb/hp) it would be 28,000/240 (116 lb/hp).
Am I missing something?

I did ratios based on published engine ratings and measured weights. It seems like a reasonable and easy way to predict relative performance.

We tow a 1994 Jeep Grand Cherokee that came with the coach. It is our last choice to drive when we are home, but it works well as a towed vehicle. It has an automatic transmission, can be towed four wheels down with no modification, and the rear door is a great entry/exit point for our 65# dog. It is a relatively common vehicle, so parts and repairs are available. It is great for getting around in snow when we travel in the winter.

Oh, and I repeat, it came with the coach. It was hooked up and ready to go. Open market value of the old Jeep is almost nothing, but it is worth a lot to us because we did not have to buy or set up a vehicle to tow.

Re: Heavy Towing

Reply #20 – October 07, 2011, 07:54:27 pm

Kent, the 01 tj has coil springs so it rides fine. The seat is a bit uncomfortable for more than eight hours straight but getting in and out and walking lets me go all day and no pain. In fact I drove the Jeep after surgery instead of my chevy pickup. Traded that said chevy in on a new dodge heavy duty single rear short box mega cab. Ypu can tow it and it is great to drive.

Re: Heavy Towing

Reply #21 – October 07, 2011, 10:12:21 pm

Just purchased a Dodge Ram 3500 4x4, Long Bed, Crew Cab. Took it over to the local scales, and the weight was 7910lb. I'm still contemplating towing it rather then the Subaru. I must admit, it would look funny pulling a truck that is bigger than the coach.

It's a BIG truck.

Re: Heavy Towing

Reply #22 – October 07, 2011, 10:30:13 pm

Brian,

OOH! OOH! Hand up here! If you are going to throw away the Subaru, throw it my way. (But you probably will want money for it.)

If you put a good hitch on the Dodge and a good tow bar on the FT, you could switch if you needed to.

Re: Heavy Towing

Reply #23 – October 08, 2011, 12:49:05 am

My M11 400 hp knows the Tahoe is back there, and its only about 5800..

Re: Heavy Towing

Reply #24 – October 08, 2011, 08:55:00 am

Tow it with the Subaru loaded in the bed? Have been trying to come up with a loading-unloading system so we can haul our motorcycle in the back of our Dodge P/U tow'd.

Affiliate Notice