I commute and want to draft another bike, but still have room to stop when someone opens a car door in front of the rider in front of me. At what distance does drafting significantly reduce drag? Are there factors other than following distance that influence drafting efficacy (wind direction, etc)?

This is not a question about whether the drafting while riding through urban environments is a good or bad idea. I know that it is probably a bad idea.

  • 2
    Are you talking about drafting another bike, or a car? If a bike, you have little choice; you'll have the be directly behind them. If you're talking about drafting a car, I'm closing this question as blatantly unsafe and illegal behavior. Oct 14, 2010 at 21:00
  • 12
    Clearly, I am referring to bicycles. See first sentence. Oct 14, 2010 at 21:10
  • 1
    That's fine. I found your opening sentence to be unclear, though; I added "another bike". I suppose the "the rider in front of me" should have tipped me off! As odd as it seems, there are many, many cyclists who do draft cars, trucks, and buses. (Also see Ben's answer.) Oct 15, 2010 at 0:44
  • 1
    It depends on how good he/she looks in lycra
    – mgb
    Jan 25, 2011 at 23:22
  • 4
    You should not ride within a car door's distance of a parked car, regardless. Sep 26, 2015 at 17:43

7 Answers 7


My opinion:

I don't believe you can effectively draft and have enough time to stop. I don't know the exact aerodynamics (and I suspect it's affected by speed and wind), but if you watch any paceline or peleton, they're never more than a couple feet (about half a meter) behind the rider in front, often only a few inches (centimeters) behind. With a crosswind or larger groupings, they're even likely to have wheel overlap (where the front part of the front wheel of the following cyclist is next to the rear part of the rear wheel of the lead cyclist).

You can really only draft safely with the cooperation of the lead cyclist, who needs to signal back to you before starting to stop.

Do the math:

Let's put it another way:

  1. If you're going 15 miles/hour (25 km/hour)
  2. That's also 22 feet/second (6.9 m/second)
  3. And if you're following 3 feet behind (1 meter) (a bit far for drafting)
  4. You have 0.136 seconds (0.145 if you take the metric rounding version) to react to something that causes the lead bike to need to brake suddenly to avoid colliding.
  5. If you're 2 feet (2/3rds of a meter), you have less than a tenth of a second. If you're 2 feet and 20mph (32 km/hour) you have about 1/14th of a second to react.

Less than a sixth of a second to figure out that the lead bike is braking and to start braking, and that's assuming your brakes are as good or better than the lead bike's brakes. If the lead bike has slightly better brakes (or wider tires, or grippier tires, or even just pulls the brake levers a bit harder than you do), you may simply have no reaction time available and a collision will be unavoidable.

In other words: you definitely can only safely draft with the full cooperation of an experienced lead cyclist who won't brake unless they've warned you or being rear-ended by you is better than whatever they're about to run into. If you were going to go by hazards, they'd need to warn you about upcoming hazards and you'd need to pull back to 10 feet (3 meters) or more.

Avoid the door zone

Additionally, you should simply stay entirely out of the door zone so that opening car doors aren't much of an issue. It's not unheard of for car doors to open very fast with no warning, so that nobody has enough time to avoid hitting the suddenly opened car door. I haven't checked the laws of every single state in the US (and definitely not outside the US), but in general the area that parked car doors can open into (the door zone) constitutes a hazard that you're not required to ride through. When a bike lane is in the door zone I'll either ride the line on the left of the lane (if that's outside the door zone), or simply ride in the right wheel track of the car lane next to the bike lane.

  • 12
    Excellent write-up. The emphasis on full cooperation is important. The rule is basically: Before drafting someone, make sure they know you are there. Oct 15, 2010 at 23:19
  • 5
    I'll add that if you're drafting someone at an effective distance (1-3 feet), you will hit them if they brake hard without warning. This is why braking in a paceline is a big no-no. So if the rider in front of you gets doored (no warning) then you are going to join in the fun!
    – darkcanuck
    Oct 17, 2010 at 1:37
  • Nice comment about avoiding the door zone - if only that was possible round here. One of the roads on my commute is so narrow that the door zones from the 2 sides of the road are only about a handlebar's width apart, and where the bike lane runs in the door zone deliberate dangerously close passing to try to force bikes into the lane that shouldn't be there becomes commonplace.
    – Chris H
    Mar 3, 2014 at 10:08
  • 5
    The don't ride in the bike lane on that stretch. Take the lane since it's obviously not safe to be in the door zone, and if the door zones are that close together there is no room for a car to pass you either. Sep 27, 2015 at 18:07
  • @ChrisCleeland that was my approach when I rode that route, but dangerously close passing was common (often combined with pulling in with no room for me to do anything other than swerve into the bike lane, after which there are too many cars to pull out again). The really narrow stretch didn't have a bike lane - it was urban but effectively a single track road (conversation at 1 year intervals!)
    – Chris H
    Sep 2, 2016 at 12:50

Depends on the size of the thing you are trying to draft.

The distances listed below are distance between objects at normal road biking speeds. Bigger distance for higher speeds. I may (or may not have) drafted a lot of things when I was younger and dumber. This is what has been observed.

  • A Bike: 1-2 Feet
  • Small Car: 2-4 Feet
  • SUV: 3-5 Feet
  • Truck: 3-5 Feet
  • 18 Wheeler: 4-8 Feet
  • Bus (my favorite): 8-12 Feet

The rudimentary calculations that others have done here are all conservative because the object you are drafting is also moving and cannot instantaneously stop, they also have to decelerate. In the case of an 18 wheeler or a bus their deceleration is likely to be slower than the cyclist. In order to truly calculate the time you have to react you would need to know the speed of both objects and the deceleration that each can achieve.

Nevertheless at these distances it is EXTREAMLY DANGEROUS to draft anything that doesn't know you are there. You will not be able to react to a rock, stick, crack in the road, or pothole, and any of these common occurrences will likely end you.

  • 6
    I'll note that there is a significant benefit to chasing another cyclist (even a safe 10+ feet): if not physics and aerodynamics, motivation. Nov 14, 2010 at 0:18
  • Yikes, be careful. If following car/bus/truck try to follow in line with wheels, try to keep a good view of road ahead so you can predict what will happen. Very dangerous if behind car/bus/truck and a HUGE pothole appears underneath you! Following in line with wheels helps with this a little.
    – gaoithe
    Aug 29, 2019 at 14:25
  • 1
    That's just reckless. Athletes get away with this kind of ignorance of safety distances because they are in a cooperating group, but you won't in commuter traffic. And you cannot tell me that you can react to a cyclist doing an unexpected emergency stop when you are following at 0.5m distance (that's only about 1/15 of a second). You are endangering yourself and others if you do this. Jun 26, 2020 at 21:25
  • 2
    I find small cars too aerodynamic - we're generally taller than them and so my head is out in the airflow, not in the drag area behind the car.
    – Criggie
    Jun 26, 2020 at 23:30
  • A cyclist (especially roadie on drops with rim brakes), won't have a hope of stopping faster than an empty bus or 18 wheeler. It won't matter if the driver knows your there or not - if something happens up front, they will try to stop. Worse, brake and swerve - the same way you went when you were unable to stop and swerved so you are now beside them.
    – mattnz
    Mar 14, 2022 at 2:08

According to this research quoted by Cycling Weekly you get pretty good drafting effects at 5 metres, as does the person you are sitting behind. And you still get a significant drafting effect up to 20 metres.

enter image description here

  • 2
    @Andrew I don't know for slower speeds, but posted the answer because it shows that drafting effect is potentially a lot further than some of the other answers here. Jun 26, 2020 at 21:05
  • 2
    Finally an answer with some science behind it :-) Jun 26, 2020 at 21:30
  • 3
    @cmaster-reinstatemonica - If you''re drafting wouldn't you want the science in front?? Jun 26, 2020 at 21:47
  • 2
    @Daniel R Hicks as long as the science is within 5 metres behind it the answer will still benefit. Jun 26, 2020 at 21:50
  • 2
    @WiggotheWookie - Yeah, but I'm always leery of getting ahead of the science! Jun 26, 2020 at 21:52

First, at around 10-12 MPH and below you are fighting rolling/frictional resistance enough that the drafting benefit is negligible in still air. If the you have a headwind of 10+ MPH or are traveling at 15+ MPH then there is some benefit to be had.

Assuming that there is no wind or a direct on head wind, the extension of the 'drafting bubble' is about 5 - 6 feet beyond the front rider. Any further back than that and neither rider experiences any benefit. Obviously the closer you get the better, but that requires the lead riders cooperation and that the two of you communicate.

Since wind is rarely straight on, many times you will be drafting slightly to one side or the other. The impact again is a little less, but you may be safer, as long as you are careful not to overlap wheels.


To answer this part of your question specifically:

At what distance does drafting significantly reduce drag?

I think a well accepted rule of thumb is that riding right on someone's wheel (within a couple feet) can save you about 40% drag. It depends on your speed, wind speed, wind direction, how aero the cyclist ahead of you is, etc.

I compete in triathlon, where there is (usually) a "no-draft" zone of 7 meters behind the cyclist in front of you. You can sit 7 meters behind (about 3 bike lengths from their back wheel) and still get a non-trivial draft. I think it can be about 10% depending on wind direction, speed, how aero the guy you're drafting is. The folks at Specialized measured this in their wind tunnel and said it could be as much as 20%. 10-20% may not be noticable to many people, but if you're in an Ironman race going 112 miles on the bike, I'll take a 10% energy savings any day, even if I don't feel it. On the other hand 10-20% may not be enough of a savings for you to risk getting in an accident on your daily commute.


Drafting is very well possible depending on the environment. In The Netherlands it is not untypical to have significant parts of your commute on stretches of cycle paths that are straight, free from car dooring risks and without side roads (or at least ones over which you have priority).

I find that at speeds of 25 km/h and above, when you stay less than 1 meter away from the draftee, there is a significant benefit. On the other hand, by riding slightly staggered behind the other person, you can watch the road ahead and anticipate any abrupt maneuvers.

  • I frequently have people draft behind me and do it from time to time myself. This is not unusual around here in southern Bavaria. Especially for regular commuters. On popular and faster routes it is unavoidable anyway, since bunches of faster riders form automatically since the first rider of a bunch is slowed down much more by slower riders than those following in their wake. At speed about a bicycle's lenght seems to be typical.
    – gschenk
    Jun 26, 2020 at 21:33
  • 2
    "and anticipate any abrupt maneuvers" - that's not correct. It should read "and anticipate some/most abrupt maneuvers. You won't be able to anticipate everything. And if you are riding so close that you cannot react to any maneuvers you did not anticipate, you are endangering the rider you are following (as well as yourself, of course). Don't do this to someone who's not cooperating! Jun 26, 2020 at 21:34

One wheel-length behind is what you're taught when learning to paceline.

And it is definitely a bad idea. If I caught someone doing that to me I would intentionally slam my brakes - I can easily correct from a rear wheel losing traction, but you would go down.

I didn't think it needs to be said, but I would not intentionally harm someone on the road.

  • With the present increase in cycling wheel length is about what one may hope for commutes here in my city. However the speed is low, between 16 km/h and 25 km/h. I did brake for the wrong set of red lights the other day and had a bunch of riders zip past me on either side. Also the noise of at least three back-tires scratching on tarmac.
    – gschenk
    Jun 26, 2020 at 21:28
  • 4
    I don't condone the aggressive part of this answer, but I'm thankful for you calling drafting in traffic a bad idea. Jun 26, 2020 at 21:36
  • 1
    Instead of instigating a crash, start by talking. Simply yell "Oi - get off ! " (substitute as you see fit). Then just take away what they want, by slowing down. There's nothing to be gained draughting at 20 km/h. If they still won't get off, then get along side and ask "what do you think you're doing ? " and have a dialogue. A later option is to check your strava flybys and see if they're listed, for a public shaming ("wheelsucker" doesn't sit nicely with many riders)
    – Criggie
    Jun 26, 2020 at 22:48
  • Or turn it around, and yell at the follower "hey its YOUR turn on the front!" and get some assist from the situation.
    – Criggie
    Jun 26, 2020 at 22:49
  • 1
    Good effort @Criggie but the assertion from Nathaniel's comment doesn't really make up for the first paragraph even though it contradicts it. Time to let the downvotes do the talking. Oh, and it's also dumb because the follower is likely to hit Nathaniel from behind and they'll both go down
    – Chris H
    Mar 9, 2022 at 9:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.