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Drafting big rigs saves a minimum of 10 percent range
- Thread starter artsci
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- Driving Dynamics Model S
MartinAustin
Active Member
Seems like it makes sense to draft behind the biggest thing you can find that doesn't have those terrible rear guards! Just drafting in general seems like a great way to extend range. There's not a lot of sport in it though...
MTOman
Member
I normally wouldn't draft in my MS due to the aforementioned flying rocks factor but I was driving back from Lake Lure yesterday and was running short on range. Especially once I got on I-40, and the speed limit went up to 70, range started dropping fast in relation to miles left to destination. Once the range was 125 miles, and I still had 120 miles to go, I realized I had 3 options.
1) Slow down - a lot - or more realistically try to find an alternate route since I'm not going to be "that guy" doing 55 in a 70.
2) Stop and charge for hours somewhere since there are no supercharges along the route and I would be forced to use a 30 amp charger at a dealership. Even a HPWC would need a couple hours.
3) Try drafting.
I chose option 3
Found a big rig that was driving fast and got right up behind him, keeping what I'm guessing was around 50-100 ft separation (I was counting seconds and it was a half second or less). Using this method I drafted almost all the way home and made it with 7 miles to spare. I'm now a firm believer in drafting but will only do it when necessary so as to limit risk and damage.
1) Slow down - a lot - or more realistically try to find an alternate route since I'm not going to be "that guy" doing 55 in a 70.
2) Stop and charge for hours somewhere since there are no supercharges along the route and I would be forced to use a 30 amp charger at a dealership. Even a HPWC would need a couple hours.
3) Try drafting.
I chose option 3
Found a big rig that was driving fast and got right up behind him, keeping what I'm guessing was around 50-100 ft separation (I was counting seconds and it was a half second or less). Using this method I drafted almost all the way home and made it with 7 miles to spare. I'm now a firm believer in drafting but will only do it when necessary so as to limit risk and damage.I normally wouldn't draft in my MS due to the aforementioned flying rocks factor but I was driving back from Lake Lure yesterday and was running short on range. Especially once I got on I-40, and the speed limit went up to 70, range started dropping fast in relation to miles left to destination. Once the range was 125 miles, and I still had 120 miles to go, I realized I had 3 options.
1) Slow down - a lot - or more realistically try to find an alternate route since I'm not going to be "that guy" doing 55 in a 70.
2) Stop and charge for hours somewhere since there are no supercharges along the route and I would be forced to use a 30 amp charger at a dealership. Even a HPWC would need a couple hours.
3) Try drafting.
I chose option 3
You'd rather risk damaging your $100k car than slow down? No thanks!
Yea I've done this several times now. One big rig didn't like me doing it though and kept crossing over the shoulder intentionally to kick up dirt and rocks. When I didn't move he eventually pulled over on the shoulder and as soon as I passed him he pulled back out onto the road behind me. It does allow you to get get range though. Doing 75mph and getting 200-250Wh/mi is great! Good thing I have XPEL ultimate. I need my windshield replaced though haha
green1
Active Member
Forget damage, he'd rather risk death then take an extra few minutes... EXTREMELY dangerous activity, just not worth the risk in any way.
I've seen what happens when a car hits the back of a semi-trailer, and even Tesla's advanced safety features are unlikely to save you. at half a second following distance you won't even be able to lift your foot off the accelerator before your impact.
The only safe way to draft is a full 3 seconds back. It won't gain you nearly as much efficiency, but you'll live to tell the tale.
Really... Like how fast does a big rig stop? What some people call traffic is drafting - it is just a matter of picking your lead vehicle. And frankly a slow braking truck is probably safer than being behind another Tesla.
But the safer way is really to be in the lane next to a big rig trailing back a little. Much much safer and you can still increase range.
Of course you wouldn't really need "hours" at a L2 charger. One hour and you would have gotten comfortably home. But the best trade off probably would be an alternate route for 1/2 the trip. Cost you 1/2 hour probably. If that.
But the safer way is really to be in the lane next to a big rig trailing back a little. Much much safer and you can still increase range.
Of course you wouldn't really need "hours" at a L2 charger. One hour and you would have gotten comfortably home. But the best trade off probably would be an alternate route for 1/2 the trip. Cost you 1/2 hour probably. If that.
EarlyAdopter
Active Member
Therein lies the problem: a full truck stops slow, an empty truck stops fast. Can you tell the difference?
green1
Active Member
Depends what he hits.
Seriously, you're not just worried about him stopping at a traffic light (though at a 1/2 second following distance you'd likely STILL hit him if he did that because you wouldn't have time to take your foot off the accelerator once his brake lights came on) You're also worried about him hitting something, him having a tire blow out (those will do a LOT of damage), him swerving around something, him driving over something that he has clearance for and you do not, and many other things.
Anything less than 3 seconds following distance is EXTREMELY dangerous. It doesn't matter how quick our car can stop, your reaction time isn't fast enough for it to matter. Of course it keeps us EMTs employed...
MTOman
Member
Wow... This was not the reaction I was expecting. I've noticed on other threads here that the "safety trolls" often turn an informative thread into a discussion on safety. I did not mean to cause that turn in this thread. We all know drafting is dangerous. We all know taking highway ramps at high speeds is dangerous. We all know driving is dangerous in general. However, I suspect most people don't visit these message boards to find out how dangerous things are. So please, pretty please, with a cherry on top, stop worrying about what others are doing with their cars. After all, their cars are theirs to do with as they please. If they want to risk their personal property what is it to you?
If anyone has something meaningful to share about drafting then I'm all ears.
“A ship is safe in harbor, but that's not what ships are for.”
- William G.T. Shedd
"A Tesla is safe when parked, but that's not what Teslas are for."
- MTOman
If anyone has something meaningful to share about drafting then I'm all ears.
“A ship is safe in harbor, but that's not what ships are for.”
- William G.T. Shedd
"A Tesla is safe when parked, but that's not what Teslas are for."
- MTOman
dhrivnak
Active Member
The problem is while it is your personal property if you end up in the ICU for months and need rehab for months more you certainly aren't paying for that. Your insurance will but unless you are a multimillionaire and paying cash for your care, everyone else who pays insurance on your plan is picking up to tab. You wrecking could also end up causing a wreck behind you or even someone going the other direction who witnesses it and gets distracted.
Something meaningful would be drafting a foot off the bumper will save a lot of energy but is very dangerous. Drafting 3 seconds back is safer but there is less energy saved.
If someone is drafting and is unable to stop in time when the truck they are drafting puts on its brakes and they hit the truck and bounce into an adjacent lane or they swerve into an adjacent lane to avoid hitting the truck and cause other cars to swerve and a multi-car pileup with injuries and fatalities results they are responsible for that!
Public roads must be used RESPONSIBLY by those who drive on them. Drafting is not responsible, it is reckless and endangers others. State laws requiring drivers to maintain a safe distance in respect to other vehicles apply to drafting.
You admit drafting is "dangerous" yet you seem upset that people make that same point.
Raffy.Roma
Rome (Italy)
Actually speaking as a professional truck driver I would like to let you know that a fully loaded truck stops the quickest then a empty truck, and finally a truck without a trailer takes the longest. This is due to when a truck brakes suddenly the wheels lock up and skip when there isn't any weight or very little. Semi trucks are built for safest handling when hauling 40 tons gross. And also speaking as a driver I too pull over when unsafe drivers are near me (this includes tailgater). Calle lazy but I dont like paperwork and any accident I get into (even the ones I am not at fault of) I have to do a ton of paperwork, work extra hours, and could be disqualified even during the investigation. Pulling over to get myself away from the dangerous driver honestly saves me alot more than just time. Oh and btw just as a FYI rock damage from any truck cannot be the truck driver's/company's fault due to the fact that in order for the rocks to damage your vehicle you had to be following extremely close.
MTOman
Member
@dsm363: Seriously? With how many wrecks happen every day in this country you're really worried I'm going to cause your rates to go up? I've never been in a wreck, have you? If so, you may be the one causing my insurance to go up a tiny fraction of a penny every year! Don't worry though, I won't hold it against you :biggrin:
@ecarfan & raffy.roma: I also admitted driving is dangerous in general but that doesn’t mean I'm not going to drive. I was driving on I-40 for 120 miles, I passed plenty of state troopers both driving and on the side of the road, if they thought my driving was dangerous they had plenty of chances to pull me over. Your uninformed armchair judgment is not necessary and only serves to derail the topic of conversation. Which, by the way, is about how drafting can save range not about how dangerous drafting is.
Overall I'm just shocked at how many safety trolls jumped in this conversation without knowing a single thing about the situation other than what I was able to fit into a couple paragraphs. So, I've decided to retract my original post. It was all a lie, just a theoretical story I made up. I've never drafted in my life, have never sped even 1 mph over, never taken a highway ramp at more than 15 miles an hour (25 is way too dangerous!!) and I stop and look both way, 12 times, anytime I cross traffic. Especially if the light is green.. because you never can be too safe! I drive exactly like a 60 year old. Is everyone satisfied now? :tongue:
@ecarfan & raffy.roma: I also admitted driving is dangerous in general but that doesn’t mean I'm not going to drive. I was driving on I-40 for 120 miles, I passed plenty of state troopers both driving and on the side of the road, if they thought my driving was dangerous they had plenty of chances to pull me over. Your uninformed armchair judgment is not necessary and only serves to derail the topic of conversation. Which, by the way, is about how drafting can save range not about how dangerous drafting is.
Overall I'm just shocked at how many safety trolls jumped in this conversation without knowing a single thing about the situation other than what I was able to fit into a couple paragraphs. So, I've decided to retract my original post. It was all a lie, just a theoretical story I made up. I've never drafted in my life, have never sped even 1 mph over, never taken a highway ramp at more than 15 miles an hour (25 is way too dangerous!!) and I stop and look both way, 12 times, anytime I cross traffic. Especially if the light is green.. because you never can be too safe! I drive exactly like a 60 year old. Is everyone satisfied now? :tongue:
EarlyAdopter
Active Member
That hasn't been true since the 90's and the advent of air brakes and ABS. In fact, unloaded trucks are required to, by design, stop shorter than loaded ones, per FMVSS 121.
Stopping distance for 70,000 and above GVWR at 60 mph is 310 ft or 335 ft, depending on axle count. Same truck, unloaded, must stop from 60 mph in 235 ft or less.
NHTSA did a test with a 1991 Volvo tractor with ABS. Loaded to 50,000 GVWR, it took 295 ft to stop from 60 mph. Unloaded, it was able to stop in only 185 ft.
A modern Volvo tractor with air disc brakes and ABS, unloaded, can damn near outstop a passenger car.
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