[START]It’s random, bored driving down the motorway question time again…[START]
How close would you have to get to the truck infront of you to make use of their ‘slipstream’ 
and would you really save much fuel using it
[/END]It’s random, bored driving down the motorway question time again[/END]
answers on a post card please. 
About three feet and yes you would save fuel. 
DieselDemon:
About three feet and yes you would save fuel.
OK, i’ll say it - but you might not save your life 
When my brother was a poor student with a 125 Honda, 60 mph was all it would go with a favourable wind. Unless he snuck up to a truck on the mway. He reckoned he could almost come completely off the throttle & still maintain 60mph. He was probably getting 200mpg 
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The world record for highest speed on a pushbike was once set by a guy v. closly following a Rover 3.5 SD1 down the M40 before it was opened. He reached 125mph IIRC, as the Rover was doing all the work.
i’ve got a 5 meter strop that’d take the weight. You’d get good economy with that - infact my truck uses .4 gallon per hour at idle which i recon is 140mpg at 56
Not quite in the same league as two trucks slipstreaming but I’ve had a good slipstream off a tractor on my pushbike.
It makes a hell of a difference. On a road where I’d normally be doing 20mph at a push I was sitting easily at 25mph barely turning the pedals. To get the best effect you need to be within 10-15feet though…
i’d say it makes a huge difference so many times i’ve pulled out to over take and suddenly lost loads of speed alternatively how would you know if someone is sneakily stealing your fuel by slipstreaming you apart from using your mirrors
caravaners i"ve noticed do it loads,they come up and sit behind me for mile after mile after mile,the look of bemusment when i pull up outside a garage,and the driver is sitting there still is priceless!!lol.
Funny how I never hear a sudden spool up of the turbo or anything when I pull out for the kill. I also have rarely seen the instant fuel economy change when pulling out. Maybe I’m not getting close enough 
Really, is it worth it?
It would seem so and the answer is very, very close:
Secretelephant:
The world record for highest speed on a pushbike was once set by a guy v. closly following a Rover 3.5 SD1 down the M40 before it was opened. He reached 125mph IIRC, as the Rover was doing all the work.
Olympic Cyclist and IRONMAN triathlon winner, John Howard set a 152.2 Miles per Hour speed record at the Bonneville Salt Flats near Wendover, Utah on July 20, 1985. He was slipstreaming 500 Horsepower Streamliner. The pace vehicle was modified by adding a large tail fairing to the 337 MPH record holding car. The fairing reduced the aerodynamic drag he is pedaling against to virtually zero.
buck73:
caravaners i"ve noticed do it loads,they come up and sit behind me for mile after mile after mile,the look of bemusment when i pull up outside a garage,and the driver is sitting there still is priceless!!lol.
I tow a caravan and it is common practice on motorways to find an empty truck that keeps at 56mph and stick behind it. This is nothing to do with fuel economy as we wouldn’t be anywhere near close enough; but all about maintaining a speed which is comfortable and causes no problems to other road users (especially HGVs). Drive any slower and we are constantly buffeted by overtaking lorries and coaches. Any faster and we are forever having to change lanes.
I never heard of anyone following a truck into a garage though.