5 ms·

> However, towing for awhile ... is something that could presumably be done by just about any passing car A Tesla model 3 weighs over 4000 pounds. A base model

> However, towing for awhile ... is something that could presumably be done by just about any passing car A Tesla model 3 weighs over 4000 pounds. A base model Toyota Tacoma isn't even rated to tow that weight, there's no way any passing sedan could. Now remember that for regenerative _braking_ to work, the tesla's brakes have been on! Definitely not something any passing car can handle.

Gustomaximus 5y ago
> A base model Toyota Tacoma isn't even rated to tow that weight Isnt this rating more about supporting and breaking force for the combined vehicle and load weight. My understanding in this case tow means 'pull the vehicle' vs carry the front weight. So I think even a smaller car would be fine to pull a Tesla.
- dahfizz 5y ago
  Being able to safely break is part of the towing test, as well as being able to haul the load up hill at highway speed. The point is that an average sedan absolutely does not have the power to tow 4,000 pounds, let alone 4,000 pounds with it's breaks on.
- throwaway0a5e 5y ago
  >Isnt this rating more about supporting and breaking force for the combined vehicle and load weight. There are braking requirements in the test but the bottleneck is almost always (i.e. I want to say always but I don't put it past Dodge to show up with a 700hp vehicle) the acceleration and minimum speed up a grade portions of the test. Given the weight that can be accelerated and pulled up a grade per the test requirements basically every vehicle winds up passing the braking portion with room to spare. But if you get all your vehicle performance advice on Reddit and HN I can see why you'd think brakes are always the bottleneck.
matt-attack 5y ago
The weight of the Tesla is moot. The majority of the load experienced by the pulling vehicle is in the incredible drag of the Tesla’s wheels. They’re extremely difficult to spin and this for pace far exceeds any others that would normally be encountered when pulling a traditional load.
- elihu 5y ago
  Well, at 70 mph the load would be a lot. If the car were towed at 25 mph it wouldn't be as difficult, and I assume most EVs let you configure the regen amount. If you set it to light regen it'll be easier to tow, but charging will take longer. Having at least some regen braking all the time seems like kind of a benefit, since there's less risk of the rear car hitting the front car if the front car stops abruptly and the driver in back doesn't step on the brakes fast enough. I can agree though that if the EV being towed really thinks it's supposed to try to stop as hard as it can, it would take a pretty powerful engine/motor or low gearing in the lead car to drag it along.
  - gorkish 5y ago
    The cool thing about EVs is that they have an instantaneous power meter in them, so there really is no need to speculate. The following numbers roughly correspond to my 2017 Model S: At 30mph the car consumes approximately 200Wh/mi (6kW or 8hp) and at 70mph approximately 300Wh/mi (21kW / 28hp). This is the power required to maintain these velocities against all external factors, and therefore is exactly equal to the power required to tow the vehicle at these speeds. If you have regen set to normal, the car will supply up to 50kW / 67hp through regen. TBH I don't know exactly what the minimum speed to achieve full 50kW is, but I am reasonably confident that the car will do it at 30mph since the tires have more than 10 times the required grip to do it. Towing at 30mph = 56kW / 75hp, 89% charging efficiency, equivalent to a ~2000lb trailer Towing at 70mph = 71kW / 95hp, 70% charging efficiency, equivalent to a ~2500lb trailer The trailer weight estimates are roughly basaed average of engine power / towing capacity figures for medium duty pickups. The tow vehicle to do this safely in my estimation should have a 250hp power plant or larger. The biggest flaw with the linked article is that it's not necessary to go 70mph to achieve the maximum charge rate from regen, and indeed it is less efficient to do so.
throwaway0a5e 5y ago
All modern trucks are conservatively rated in the towing department because of the grade pulling requirement in the test all the OEMs use.
- dahfizz 5y ago
  The SAE J2807 tow grade test is done on a real highway in Arizona, not some made up crazy scenario. If you can only tow a certain load in ideal circumstances (no hills, no sudden braking, no wind, etc) then you actually cannot safely tow that load. The real world has hills and the occasional need to slam on your brakes.
  - throwaway0a5e 5y ago
    >The SAE J2807 tow grade test is done on a real highway in Arizona, not some made up crazy scenario. So? That doesn't make it representative of typical conditions. >If you can only tow a certain load in ideal circumstances (no hills, no sudden braking, no wind, etc) then you actually cannot safely tow that load. So someone in Kansas or Florida should be limited by grades that aren't even with a day's drive of them? Do you seriously believe this? This line of reasoning is even more comical in light of how the current SAE test almost always results in engine power being the bottleneck. There's a pretty massive amount of safe behavior you can do outside the confines of the magic rating number and even more options of unsafe things you can do within the number. At the end of the day some amount of good judgement and discretion is required because there is no shortage of variables that are static in the SAE test Your position is only a stone's through from the pitch of the slimy RV salesman who says you can tow something anytime anywhere because it's less than the magic number. I think you (and the hypothetical RV salesman) need to take your appeal to authority and desire to substitute a nuance-free number with critical though and shove them somewhere unpleasant.
    - dahfizz 5y ago
      > So someone in Kansas or Florida should be limited by grades that aren't even with a day's drive of them? Do you seriously believe this? I never said that. I think the current tow rating system does represent the safety margins needed in real world towing. If a truck can't tow X pounds up an actual hill on an actual US highway, then it shouldn't advertise being able to tow X pounds. But, if you live in Kansas and you are sure that your brakes can handle a higher load, that's fine. As you said, it's up to you the driver to know what's safe and not. I also think you have it coming if you lose control of an overloaded truck and your insurance company refuses to cover damages, etc. I view it similar to overclocking a server. Servers are clocked somewhat conservatively to ensure reliability. You are free to overclock a machine you own, but you run the risk of instability and you cannot complain to the manufacturer if you have downtime resulting from running your machine outside of spec.
gorkish 5y ago
Towing ratings are given in lbs but you have to remember that is a "full system" number which includes the load on the hitch, the tongue weight, and (the usual limiting factor) the ability for the vehicle to reasonably accelerate and stop the entire mass in a reasonable time and distance. I estimated the required power and the equivalent "trailer weight" of towing a tesla model s under full regen elsewhere in this thread; it's roughly equivalent to towing a trailer of approximately 2000-2500lbs, depending on speed. A vehicle with a similar tow rating and a minimum 250hp engine should do the job.

Gustomaximus 5y ago

> A base model Toyota Tacoma isn't even rated to tow that weight Isnt this rating more about supporting and breaking force for the combined vehicle and load weight. My understanding in this case tow means 'pull the vehicle' vs carry the front weight. So I think even a smaller car would be fine to pull a Tesla.

dahfizz 5y ago
Being able to safely break is part of the towing test, as well as being able to haul the load up hill at highway speed. The point is that an average sedan absolutely does not have the power to tow 4,000 pounds, let alone 4,000 pounds with it's breaks on.
throwaway0a5e 5y ago
>Isnt this rating more about supporting and breaking force for the combined vehicle and load weight. There are braking requirements in the test but the bottleneck is almost always (i.e. I want to say always but I don't put it past Dodge to show up with a 700hp vehicle) the acceleration and minimum speed up a grade portions of the test. Given the weight that can be accelerated and pulled up a grade per the test requirements basically every vehicle winds up passing the braking portion with room to spare. But if you get all your vehicle performance advice on Reddit and HN I can see why you'd think brakes are always the bottleneck.

matt-attack 5y ago

The weight of the Tesla is moot. The majority of the load experienced by the pulling vehicle is in the incredible drag of the Tesla’s wheels. They’re extremely difficult to spin and this for pace far exceeds any others that would normally be encountered when pulling a traditional load.

elihu 5y ago
Well, at 70 mph the load would be a lot. If the car were towed at 25 mph it wouldn't be as difficult, and I assume most EVs let you configure the regen amount. If you set it to light regen it'll be easier to tow, but charging will take longer. Having at least some regen braking all the time seems like kind of a benefit, since there's less risk of the rear car hitting the front car if the front car stops abruptly and the driver in back doesn't step on the brakes fast enough. I can agree though that if the EV being towed really thinks it's supposed to try to stop as hard as it can, it would take a pretty powerful engine/motor or low gearing in the lead car to drag it along.
- gorkish 5y ago
  The cool thing about EVs is that they have an instantaneous power meter in them, so there really is no need to speculate. The following numbers roughly correspond to my 2017 Model S: At 30mph the car consumes approximately 200Wh/mi (6kW or 8hp) and at 70mph approximately 300Wh/mi (21kW / 28hp). This is the power required to maintain these velocities against all external factors, and therefore is exactly equal to the power required to tow the vehicle at these speeds. If you have regen set to normal, the car will supply up to 50kW / 67hp through regen. TBH I don't know exactly what the minimum speed to achieve full 50kW is, but I am reasonably confident that the car will do it at 30mph since the tires have more than 10 times the required grip to do it. Towing at 30mph = 56kW / 75hp, 89% charging efficiency, equivalent to a ~2000lb trailer Towing at 70mph = 71kW / 95hp, 70% charging efficiency, equivalent to a ~2500lb trailer The trailer weight estimates are roughly basaed average of engine power / towing capacity figures for medium duty pickups. The tow vehicle to do this safely in my estimation should have a 250hp power plant or larger. The biggest flaw with the linked article is that it's not necessary to go 70mph to achieve the maximum charge rate from regen, and indeed it is less efficient to do so.

throwaway0a5e 5y ago

All modern trucks are conservatively rated in the towing department because of the grade pulling requirement in the test all the OEMs use.

dahfizz 5y ago
The SAE J2807 tow grade test is done on a real highway in Arizona, not some made up crazy scenario. If you can only tow a certain load in ideal circumstances (no hills, no sudden braking, no wind, etc) then you actually cannot safely tow that load. The real world has hills and the occasional need to slam on your brakes.
- throwaway0a5e 5y ago
  >The SAE J2807 tow grade test is done on a real highway in Arizona, not some made up crazy scenario. So? That doesn't make it representative of typical conditions. >If you can only tow a certain load in ideal circumstances (no hills, no sudden braking, no wind, etc) then you actually cannot safely tow that load. So someone in Kansas or Florida should be limited by grades that aren't even with a day's drive of them? Do you seriously believe this? This line of reasoning is even more comical in light of how the current SAE test almost always results in engine power being the bottleneck. There's a pretty massive amount of safe behavior you can do outside the confines of the magic rating number and even more options of unsafe things you can do within the number. At the end of the day some amount of good judgement and discretion is required because there is no shortage of variables that are static in the SAE test Your position is only a stone's through from the pitch of the slimy RV salesman who says you can tow something anytime anywhere because it's less than the magic number. I think you (and the hypothetical RV salesman) need to take your appeal to authority and desire to substitute a nuance-free number with critical though and shove them somewhere unpleasant.
  - dahfizz 5y ago
    > So someone in Kansas or Florida should be limited by grades that aren't even with a day's drive of them? Do you seriously believe this? I never said that. I think the current tow rating system does represent the safety margins needed in real world towing. If a truck can't tow X pounds up an actual hill on an actual US highway, then it shouldn't advertise being able to tow X pounds. But, if you live in Kansas and you are sure that your brakes can handle a higher load, that's fine. As you said, it's up to you the driver to know what's safe and not. I also think you have it coming if you lose control of an overloaded truck and your insurance company refuses to cover damages, etc. I view it similar to overclocking a server. Servers are clocked somewhat conservatively to ensure reliability. You are free to overclock a machine you own, but you run the risk of instability and you cannot complain to the manufacturer if you have downtime resulting from running your machine outside of spec.

gorkish 5y ago

Towing ratings are given in lbs but you have to remember that is a "full system" number which includes the load on the hitch, the tongue weight, and (the usual limiting factor) the ability for the vehicle to reasonably accelerate and stop the entire mass in a reasonable time and distance. I estimated the required power and the equivalent "trailer weight" of towing a tesla model s under full regen elsewhere in this thread; it's roughly equivalent to towing a trailer of approximately 2000-2500lbs, depending on speed. A vehicle with a similar tow rating and a minimum 250hp engine should do the job.