jyl

Stupid thing to do. 35 mph = 51 ft/sec. Reaction time = 0.5 sec for the fastest people under near-perfect situations. 0.5 sec at 51 ft/sec = 25 feet. Typical drafting distance = 10 feet or so. In other words, when that bus or truck or car does a sudden, surprise, hard braking, it won't matter if you think your bike can stop faster than a bus, truck, or car. You will be eating the rear bumper before you've even grabbed your brake.

cooker

But the OP prefers Breaking Away (1979).

wphamilton

As several people have stated, cars have an advantage over bicycles in stopping regardless of the brakes on the bikes. If they do a panic stop or brake check you, the odds are you're going to rear end them. I don't care how good your brakes are or how fast your reactions.

That's not necessarily a disaster if you're a great bike handler who could bump and bounce off and stay in control. I've never bumped anything while drafting so that's second hand but it's reasonable because your relative speed is a lot less. If you're a great bike handler. If someone doesn't understand that motor vehicles can stop faster I don't see how they can evaluate the risks correctly, and that's going to make it more dangerous.

otter22

A additional thought for those drafters who think they can win in playing braking reaction time roulette - what happens when the bus/truck you are drafting comes to a sudden stop because it t-bones the guy who just ran a red light at an intersection or pulls out right in front of them from a side road. No brake lights, no warning - just a free half-second tour of the undercarriage of a large commercial vehicle for you and your bike.

gregf83 

I'll admit I will occasionally draft a vehicle for fun. If it's a car you should be able to see through the windows so you can anticipate any slowdowns. With large trucks or buses I'll ride on the edge of the vehicle. The draft isn't ideal but it's still substantial and I can maintain visibility forward and have an exit path if the truck slows.

I think the biggest risk to safety is obstacles the truck drops or drives over which you won't have time to react to.

gregf83 

It's a little more complicated than your example since the vehicle in front of you will be slowing, not stopped.

If you assume the vehicle in front decelerates at .5g (fairly hard braking) and your reaction time was 1 sec (mine was 281mS on the computer) you wouldn't hit the vehicle provided you could also decelerate at .5g. Maximum braking for a bike is similar to that of a bus or large truck, approx .6g.

I'm not saying it's a great idea just pointing out the biggest danger is not from the vehicle in front braking.

NoviceJohn

Following dump trucks is dangerous even when you're driving in your car. If it's a construction dump truck, then debri can fly out and hit in the face, bike, etc causing you to wreck. If it's a garbage truck, then, you have to ask yourself if it's worth it to ride and smell the garbage at the same time?

JReade

I drafted a lowboy trailer hauling an excavator the other day. It was pretty fun, max was 30 mph, on a road I know that had no stop signs. I've done it behind dump trucks, and my personal favorite was a panel van. I've done it it on a few roads I don't know, and that gets a little iffy, but on one or two roads that I ride on all the time, I know the roads, and there is plenty of bail out to the right, so I just stay close to the right of the vehicle. Best I've drafted to was 36 mph, and it was getting tough to stay in the draft.

tcs

Decades ago one of my riding partners was in his 80s. He'd worked as a bike messenger back in the late 'teens, during the Great War. Drafting? Bah. He said the way to make a quick, easy run was to grab ahold of a car or truck and let them tow you. Back then he said drivers more or less expected to give a tow to bicycling messengers/delivery boys, at the very least on the long, flat run across the viaduct over the river.

Of course it was just as dangerous/deadly then as it is today*, and society got tired of scrapping the remains of bicyclists off the street. The state legislature made cyclists hanging on to motor vehicles illegal in the 1920s.


*Cars didn't move as fast, but there were a lot more trolley tracks.

spare_wheel

It's called skitching. For a rider with skill, its also an order of magnitude safer than drafting a garbage truck.

Andy_K 

My father-in-law, who was a bike messenger in San Francisco in the 30's told me similar stories involving cable cars. He also said if you got a flat tire you could just grab the wheel off some other bike and leave yours. He said people expected it. I sometimes found myself questioning his interpretation of what other people thought was acceptable.

spare_wheel

you are assuming no detection lag and instantaneous maximal deceleration.

gregf83 

No, I allocated 1 second which is over 3 times longer than it takes me to detect and react. I also assumed similar deceleration to a large vehicle which isn't unreasonable.

JoeyBike

Been doing the same for decades. Some tips (I have not read the rest of this thread so sorry for repeats) for you:

- Don't see how much time you can spend DIRECTLY behind the vehicle so you will not be surprised by road hazards straddled by the truck or bus (cars are easier to see over/around/through). Ride JUST inside the draft cone which starts inches OUTSIDE the rear tail lights. So you should be able to actually see the road ahead of you - at least the small sliver your tires will be rolling on. This is the safest position. You will almost be splitting lanes.

- Keep one eye on the road ahead and the FRONT WHEEL of the vehicle being drafted, and one eye on his brake lights/turn signals so you don't get surprised by lane changes or turns. If your position is correct, a lane change won't kill you but a sudden turn might.

- Pay strict attention to what you are doing. NO WOOLGATHERING.

- If you are doing it right safety is not a BRAKE issue. It's attentiveness.

IMO...keeping up with traffic by drafting or just riding fast is always safer than letting every car on the road pass you. Keep all situations coming at you from up front where you can see them and deal with them yourself. Drafting is perfectly safe if you do it right no matter what the old fart safety nannies around here tell you.

Cheers!

Bizman

Back in the day I remember what was called skitching, although no bike was involved. It was holding onto the bumper of a school bus with both hands and bending your knees as to be in a sitting postion when the roads had snow on them or a wet surface and the buss would pull you along with both feet planted firmly flat on the ground. Several kids at a time would latch on, that was back when you could have fun at school. Skitching, havn't heard the word in years, ah the memories....

mister

I avoid drafting large vehicles because around here they are all diesel and I don't want to huff in the exhaust. Now, a CNG city bus I have done a couple times when in a head wind to catch a break. Like many others have said, I worry more about the road than smacking into the back of the vehicle.

I also tried skitching once with a delivery truck. The driver didn't much appreciate me bumming a lift and ran me to the curb. Last time I ever do that...

NatUp

You do realize that isn't how eyes work...

Hence the stupidity of drafting vehicles without their consent.

spare_wheel

skitch on the non-curb side.

spare_wheel

drafting is positioning yourself for maximal aero advantage. what you are doing is simply not drafting. i ride the way you describe all the time and it's much safer because you can split the lane.

aaronmcd

Haven't read the other replies yet.
I loved drafting buses, trucks and RVs on my commutes. As for braking, you can get a really good draft even being way back from a bus or truck. Those things are huge - no need to be right on the bumper. If I want/need to draft closely, I'll be at the right corner so I can ride up the side if it brakes suddenly. Haven't had that happen yet though.

Edit: Agree with others about drafting buses - not the best, due to all the stops. The best are vans/RVs.
Disagree with those talking about being very close. I repeat, you do NOT need to be very close to such a monstrous vehicle to get a good draft. I've gotten noticeable draft from a sedan as much as multiple car lengths back.

spare_wheel

riding 20-30 feet behind a vehicle is my normal position. so i guess i always draft.

JoeyBike

Maybe your eyes don't work. Mine work fine and never stop moving in traffic.

I almost never rest my gaze on one spot for longer than a second or two. Driver's Ed teaches this too - "Get The Big Picture" is how they put it. And peripheral vision added to eye movement is nearly 180° without turning my head. I can be looking at the horizon ahead and see a turn signal light up near my left hand. My central vision might go something like this: Horizon, parked cars, helmet mirror, parked cars, horizon, front wheel of nearest car, helmet mirror, horizon, parked cars, pedestrian crossing, road surface, etc., at about the same speed as it took you to read those words. And when I am staring at one of those locations mentioned, my peripheral vision is seeing the next closest one - at least. One place i NEVER look while rolling...down at my bike or computer.

I repeat my claim above: Drafting is all about being continually alert and proper positioning near the vehicle being drafted. If you are not capable of having total concentration on what you are doing for a duration of time...don't draft. Otherwise, it's no big deal. If you can't help thinking about that project at work...move to the bike lane or a side street.

fietsbob

theres another topic of some guy motor-pacing behind a billboard towed behind a truck on a Welsh Beach

fortunately the sand in the vortex behind the flat panel didnt fill his lungs with sand. [much?]

https://api.viglink.com/api/click?for...13885329941536

NatUp

Yeah, I hear you. I was just busting your chops trying to get at the idea that maybe it's not the best plan to put your life and someone else's bumper/paint job at risk for an activity that requires so many eyes looking at so many different things.

If I didn't want to use my own energy to propel my own self to work, I'd hop on a bus, grab an e-bike, or -- gasp -- drive a car.

Leisesturm

I have been riding for more years than you have been alive. I have briefly been a bike messenger in NYC. I have done some crazy stuff in traffic. I have run more red lights than you have had hot meals but I have never drafted a bus or anything else for that matter and neither has anyone else I know. I've played leap-frog with buses but the driver always knows I am back there. I live in a fairly small town. So did the guy in Breaking Away. Draft someone who hasn't o.k.'d it and you are asking to be brake checked into the ER. Potholes... cracks... the crack you are smoking you mean? Who memorizes all the cracks in the roads they ride, no matter how many times they ride them? How do you know someone didn't lose their muffler overnight? SMH. Do you think we were all born yesterday afternoon?