Range While Towing

[O-G]

There has been a great deal of chat about the weight that the MX can tow. I am not overly concerned about the weight but the impact on range. Not being an expert in this area, I ask for input from others. Is there a way to calculate the impact? Can I ask a trailer mfg for a drag coefficient or something else that will then allow me to at least estimate the impact on range. Personally, I am looking into an Rpod light weight trailer. Dry weight is about 2500 lbs, loaded weight 3500 lbs so the weight is not the problem. But, if it brings me down to 100 mile range, I can't even jump between superchargers. Is there any way to figure this out? I'd hate to buy the camper and then say whoops, that doesn't work! I wonder if TM has any calculations?

 

[Jon]

Too many variables, and it is not likely any trailer manufacturer will have measured them yet.

That being said, the best way is to try it. I think if you were to approach the trailer dealer and ask if you could do a test tow prior to purchase, they'd be happy to oblige so they can then advise other EV customers.

You may need to offer them a ride I your Model X in return, of course.

Let us know how you make out. I'm hoping to get a travel trailer camper at some point too.

Cheers,

Jon

 

[BerTX]

In highway driving, aerodynamics are a much bigger factor on range than weight. Speed will be much more important while towing, so slowing down will help. Most trailer tires are only rated for a speed of 65 mph, so plan on going slower than that.

Also, although the teardrop campers look sleek and aerodynamic, they are not any more so than a square box. They are usually smaller, and that reduction in area is where the savings are.

 

[bwa]

I'm hunting for Internet information using Google, and in 1 second I found this one:

r-pod gas mileage fix - R-pod Owners Forum - Page 1

I'd love to see airflow simulations of a stiff leather or stiffer composite material that created a seamless connection between the sides, roof and undercarriage of the TV (Towing Vehicle in the rpod forum paralance) to the rpod (trailer). You could mount the material to the Model X using some sort of really seamless type of connection, but of course that would cause damage to the top layer -- perhaps some xpel or some plastic on the X to protect it? -- then if it is a firm enough connection, it won't peal off in the extreme forces of driving speed wind (think a six month long constant hurricane for idea of the forces it should withstand). Then, it would slope gently to the slightly different profile of the rpod (or whatever trailer) naturally by connecting it seamlessly to the rpod (trailer) with some sort of spring-loaded system that would pull it tight while turning corners both on the inside and outside sides of the corner turn, which would have to let it travel many several feet I think (you'd have to go and measure this). You'd have to devise some sort of system to keep it snug to the trailer so it wouldn't "flap around" at high speeds despite being a free-floating sliding thing due to the spring loaded turn system. One idea is having railings of some sort that hold it tight to the trailer, but that would itself introduce an air hit. So would the springs. Thinking ... hmm, the stiffer composite material if made to be strong enough not to bend could have cross-springs in front of the trailer between the TV and trailer pulling the sides inward and the roof and floor toward each other, keeping them tight to the trailer. With the leather system, I think there's just too much flapping around. I'm leaning toward some sort of composite material because of that. Come to think of it: it's OK if the leather system only makes full contact when within a few degrees of straight, since it would mostly be useful at higher speeds where you're not turning much. When turning at slow speeds, it would buckle (you'd have to have anti-drag devices for the buckle side) on inside and it would spring-gap at the outside of the turn. When at high speeds, the springs would pull it into the trailer. Still not sure the best way to keep leather from flapping. I'm heavily leaning toward stiff type panels. Edit: I just realized a combination would work well: the stiff panels near the trailer and the leather near the TV, connected seamlessly. Perhaps ribs (structural beams) between the TV and the stiff panels would still be necessary (with 4-directional hinging at the TV) to keep the panels stiff enough to spring-load interior to pull them tight to the trailer. Not necessarily the best option.

BTW when reading the rpod forum, Model X people have an entirely different calculation than ICE owners for cost-benefit analysis: ICE can make it, Model X can't, if they run out of juice.

In California, speed limit on CA99 and I5 is 70 MPH, and 84MPH (1MPH less than a 2 point driving violation, only a 1 point violation) is common, for regular passenger vehicles. 55MPH is speed limit when towing anything. This by itself means you'll be driving slower. This might make up for some of the mileage.

I really think Tesla needs to come up with trailer-mount battery storage for tow vehicle use while driving solutions, for just this reason. An additional port would be made available connecting the Model X TV to the trailer that supplies the necessary power and control connection between the two vehicles. Charging the trailer would be a matter of connecting it at the SC (Supercharger), either directly, or having the Model X charger charge both at the same time. This requires engineering, which is why I'd like to see Tesla do the work and productize it.

 

[Red Sage]

Apparently there are some States that have no restrictions whatsoever on towing speed. You are allowed to drive at the same rate of speed as passenger cars while towing. I apparently haven't driven through those States, because I remember seeing signs that limited towing vehicles to either 55 MPH or 10 MPH less than the posted limit for passenger cars. Some go further, by lowering the speed limit for all vehicles by 10 MPH at night.

 

[BerTX]

View attachment 93454
Apparently there are some States that have no restrictions whatsoever on towing speed. You are allowed to drive at the same rate of speed as passenger cars while towing. I apparently haven't driven through those States, because I remember seeing signs that limited towing vehicles to either 55 MPH or 10 MPH less than the posted limit for passenger cars. Some go further, by lowering the speed limit for all vehicles by 10 MPH at night.

No state has a speed limit higher than 65 mph while towing. That may be the same as the non-towing speed limit in some areas.

People are probably unaware that the speed limit is lower while towing, but most ignore it whether they are aware or not.

 

[Red Sage]

No state has a speed limit higher than 65 mph while towing. That may be the same as the non-towing speed limit in some areas.

People are probably unaware that the speed limit is lower while towing, but most ignore it whether they are aware or not.

That's what I thought, but I was shouted down on the Tesla Motors forum by people who insisted that in States like Utah you could tow with impunity at 80 MPH. They directed me to a link, that I don't have handy, that seemed to prove their point. So I relented, though I have not observed higher towing speeds myself.

 

[santana338]

I'm interested in this question too (subscribed to the thread). I'm trying to talk my wife into getting a used MX in a few years. The one thing that is an unknown for me is whether we will be able to tow our pop-up camper with the MX and be able to make it from SC to SC. Range is going to be incredibly variable. In our case the AC on top of the camper is an aero brake. So are the bikes if they are on top. I'm going to have to work on my wife a little at a time though. She is used to just getting in the car and hauling the mail to our destination. Slowing down will be a hard sell. SC stops are not seen as something positive at this point either.

I'm hoping this thread will be a central location for real world info on MX towing starting next month.

 

[Red Sage]

I believe this may have been one of the links I was directed to before:

Passenger Car Trailers - AAA Digest of Motor Laws

Few States actually mention towing speed at all, and most don't list a maximum speed even then, unless you are moving a house or mobile home. This seems to do with the total weight of whatever is being towed more often than not, and would not apply to a 5,000 lbs tow capacity typically. Most seem to be primarily concerned with hill holding or ability to stop at low speed.

Per AAA:

ALASKA: The maximum speed while towing a mobile home is 45 mph.

...

ARIZONA: Vehicles towing trailers or semitrailers may not exceed a rate of speed that causes lateral sway.

...

ARKANSAS: Speed limits are 70 mph on rural interstates; 55 mph on urban freeways; or as posted.

45 mph is maximum when towing house trailer.

...

CALIFORNIA: Maximum speed for any vehicle towing another vehicle is 55 mph.

...

DELAWARE: No trailer carrying a gross weight of load in combination with a vehicle in excess of 4,000 lbs. shall be operated at a speed over 10 mph unless equipped with suitable brakes controlled by the operator of the towing vehicle.

...

FLORIDA: Unless otherwise posted, 30 mph in business and residential districts, and 55 mph at any time at all other locations. Turnpike and other designated highways 65 mph, except where posted 70 mph (minimum speed 50 mph).

...

KANSAS: Every combination of vehicles shall have a service braking system, which will stop such combination within 40 feet from an initial speed of 20 mph on a level, dry, smooth, hard surface, and shall have a parking brake system adequate to hold such combination on any grade on which it is operated under all conditions of loading.

No person shall operate a vehicle towing a house trailer at a speed greater than 55 mph.

...

MICHIGAN: A person driving a passenger vehicle pulling another vehicle or trailer shall not exceed the posted speed limit.

...

MISSISSIPI: Every trailer which shall be towed on public highways at a speed greater than 20 mph shall be coupled to the towing vehicle by means of a safety chain, chains, cables, or equivalent devices in addition to the regular trailer hitch or coupling.

No more slack shall be left in any safety chains, cables, or equivalent devices than shall be necessary to permit proper turning. The safety chains, cables, or equivalent devices shall be so connected to the towed and towing vehicles and to the drawbar to prevent the drawbar from dropping to the ground if the drawbar fails and shall be of sufficient strength to control the trailer in the event of failure of the regular trailer hitch or coupling.

...

NEBRASKA: No person shall operate any motor vehicle when towing a mobile home at a rate of speed in excess of 50 mph.

...

NEW HAMPSHIRE: ...Every combination of motor vehicle with a trailer or semitrailer when driven upon the roadways of the state shall at a speed of 20 mph be capable, at all times and under all conditions, of stopping on a dry, smooth, approximately level pavement free from loose material, upon application of the foot or service brake, within a distance of 30 feet.

...

NORTH DAKOTA: Every trailer operated at a speed in excess of 25 mph must have safety chains or brakes adequate to control the movement of and to stop and to hold such vehicle. The safety chains or brakes must be designed so that they can be applied by the driver of the towing vehicle from its cab, and must be designed and connected so that in case of an accidental breakaway the brakes are automatically applied.

...

OHIO: 55 mph is the maximum speed for any vehicle or vehicle combination that weighs over 8,000 lbs.

...

OREGON: Adequate to control trailer under all conditions of varying speeds and weights; 1 safety chain is required on all trailers with 2 connections to the towing vehicle. The tensile strength of the safety chain must equal the gross weight of the trailer.

...

SOUTH CAROLINA: Manufactured, modular, or mobile homes must not be transported at a speed in excess of 10 miles below the maximum posted speed limit when the maximum posted speed limit is in excess of 45 mph, and never in excess of 55 mph.

A person driving a vehicle towing a house trailer must not drive faster than 45 mph.

...

SOUTH DAKOTA: In addition to the regular trailer hitch or coupling device, every trailer that is towed on the public highways at a speed of more than 20 mph must be coupled to the towing vehicle with a safety chain, chains, cables, or an equivalent device. This requirement does not apply to a semitrailer having a connecting device composed of a 5th wheel and kingpin assembly that meets the requirements of the Interstate Commerce Commission.

...

TEXAS: A trailer or pole trailer is required to have brakes if its gross weight exceeds 4,500 lbs. A trailer with a gross weight between 4,500 lbs. and 15,000 lbs. is not required to have brakes if it is towed at a speed of not more than 30 mph.

...

UTAH: Every motor vehicle and every combination of vehicle shall have a service braking system which will stop the vehicle or combination within 40 feet from an initial speed of 20 mph on level, dry, smooth, hard surface.

Every motor vehicle and combination of vehicles shall have a parking brake system adequate to hold the vehicle or combination of any grade on which it is operated under all conditions of loading on a surface free from snow, ice, or loose material.

...

WEST VIRGINIA: ...A motor vehicle or combination of motor-drawn vehicles must be capable of stopping at the following rates as if on a dry, smooth, level free road: (1) vehicles or combinations of vehicles with brakes on all wheels must be able to decelerate at a speed of 14 feet per second; and (2) vehicles or combinations of vehicles not having brakes on all wheels must be able to decelerate at a speed 10.7 feet per second.

...

WYOMING: Every combination of vehicles must have a service braking system that will stop the combination of vehicles within 40 feet from an initial speed of 20 mph on a level, dry, smooth, hard surface.

Every combination of vehicles must have a parking brake system adequate to hold the combination of vehicles on any grade on which it is operated under all conditions of loading on a surface free from snow, ice, or loose material.

...

PUERTO RICO: Same as for passenger cars according to the zone, but maximum speed for heavy motor vehicles is 10 mph less than permitted in any zone.

 

[Vitold]

There has been a great deal of chat about the weight that the MX can tow. I am not overly concerned about the weight but the impact on range. Not being an expert in this area, I ask for input from others. Is there a way to calculate the impact? Can I ask a trailer mfg for a drag coefficient or something else that will then allow me to at least estimate the impact on range. Personally, I am looking into an Rpod light weight trailer. Dry weight is about 2500 lbs, loaded weight 3500 lbs so the weight is not the problem. But, if it brings me down to 100 mile range, I can't even jump between superchargers. Is there any way to figure this out? I'd hate to buy the camper and then say whoops, that doesn't work! I wonder if TM has any calculations?

In this article authors tested 1/2 tonne pickup trucks (also interesting for measuring acceleration while towing) and provided MPG graph with and w/o trailer. Numbers show that RAM1500 lost 56% of range while hauling. I think this would be the worst case scenario for Model X for two reasons: pickup trucks are less aerodynamic, and dual motor setup may offer better efficacy curve.

Considering above, I think that worst case scenario for Tesla X maybe 110 mile range while towing All American Trailers double-axle two-horse trailer @5500 lbs. Results of course will vary based on the weight and shape of the trailer.

 

[BerTX]

I believe this may have been one of the links I was directed to before:

Passenger Car Trailers - AAA Digest of Motor Laws

Few States actually mention towing speed at all, and most don't list a maximum speed even then, unless you are moving a house or mobile home. This seems to do with the total weight of whatever is being towed more often than not, and would not apply to a 5,000 lbs tow capacity typically. Most seem to be primarily concerned with hill holding or ability to stop at low speed.

Per AAA:

I guess it's the typical Internet philosophy of searching until you find the answer you want. This AAA compilation is rediculously incorrect and incomplete, but so are most other compilations. Best to check the laws for individual states.

 

[Red Sage]

Agreed.

 

[Vitold]

Agreed.

So is disagreeing w/o proving ones point or following up with me 3

 

[widodh]

I personally think that the impact will not be very huge.

Why? Well, under normal conditions you wil drive you X to 120 ~ 130km/h (75mph), but when towing you'll drive 90km/h (55mph). That difference in speed might actually 'save' you.

Am I sure? No, real tests will have to show. But here in the Netherlands the maximum speed when towing anything is 90km/h and that is a speed where a Model X will be very efficient due to the low(er) air resistance.

 

[Red Sage]

So is disagreeing w/o proving ones point or following up with me 3

I was replying to BertX, while trying out the 'hybrid' mode, which shows threaded messages.

Was there something I was supposed to agree with you on?

 

[Vitold]

I personally think that the impact will not be very huge.

Why? Well, under normal conditions you wil drive you X to 120 ~ 130km/h (75mph), but when towing you'll drive 90km/h (55mph). That difference in speed might actually 'save' you.

Am I sure? No, real tests will have to show. But here in the Netherlands the maximum speed when towing anything is 90km/h and that is a speed where a Model X will be very efficient due to the low(er) air resistance.

Due to aerodynamic drag MX will have to use almost 2x power while pulling trailer (24ft frontal area, .8 Cd) at 55mph. On the other hand reducing speed from 75 to 55Mph will use 35% less power (assuming .25 Cd). Therefore final range will depend a lot on drag coefficient of the trailer.

 

[dwebb66]

I would venture a guess that Tesla will be basing any towing measurements will be based on the type of trailer seen in the mule photos.

 

[Macgaver]

I believe the range impact will be like with ICE.

I have a two-seadoo trailer (Total weight is ~2500 lb). My Q5 range is then 280 Miles (compared to my normal ~400 Miles). My range impact is -30%
So with my ModelX, I expect a minimum of 30% impact. Range will probably move from 240 Miles down to ~170 Miles.

It's highly dependent of the trailer aerodynamic. So if you know your current ICE Range impact, it's probably a good approximation start.

 

[Jeva]

I wonder how the regenerative coasting (I'm sure I don't have the right term here) is impacted by towing. With more weight, in downhill situations there may be less need to hit the accelerator because it wouldn't slow the car down as much (my Tesla driving has been limited to a test drive so I may be off here)

 

[widodh]

I wonder how the regenerative coasting (I'm sure I don't have the right term here) is impacted by towing. With more weight, in downhill situations there may be less need to hit the accelerator because it wouldn't slow the car down as much (my Tesla driving has been limited to a test drive so I may be off here)

Still, you need to haul the weight up the hill as well. You will never gain more energy going down then it took to get you up.