Don't draft me!

Bean Long said:

OzCableguy said:

http://www.sportsci.org/encyc/cyclingupdown/cyclingupdown.html#downhill

Scaling reveals that larger cyclists have a greater ratio of mass to frontal
area. They therefore descend hills faster as a consequence of purely
physical, not physiological, laws. Since the larger cyclist has a greater
mass, gravity acts on him or her with a greater force than it does on a
smaller cyclist. (Note: A common misconception is to note the equal
acceleration of two different sized objects in free fall in a vacuum, and
assume that the force of gravity on both is equal. The force on the more
massive object is greater, being exactly proportional to mass, which is why
the more massive object is accelerated at the same rate as the less massive
one.) While the larger cyclist also has a greater absolute frontal area than
the smaller cyclist, the difference is not as great as that for their
masses. Thus, the larger cyclist will attain a greater s3 before a balance
of forces results in terminal velocity.

Aha... cool! Or not so in my case... I'm tiny (voice goes up an
octave). If someone is prepared to do the maths, how much slower am I
going to travel that Oz going downhill. I'm 60 kg. No wonder I was so
sh!t at the ITT on Monday! :-)

Thanks for the physics lesson all. Us biologists have no idea!

the only problem for us fat, lazy sprinters, is that going uphill, the
main limiting factor (acceleration against gravity) resistance varies
linearly with velocity, but going downhill, the main limiting factor
(drag) varies quadratically with velocity. So, we don't get back on
descents as much as we lose on climbs.

Poo, eh?

Zebee Johnstone said:

So unless the heavier rider is carrying the weight aerodynamically,
they'll be slower due to wind resistance?

Yeah, but frontal surface area is a power of 2, while volume (and hence
mass, assuming a very rough mean density of 1g/cm^3) is power of 3. Go
from 80 kg to 120 kg and your frontal area probably only goes up around
25%, if that.

And beer guts are aero, or so the SS guys keep telling me.
--
Dave Hughes | [email hidden]
That which does not kill me, make me stranger
- Old Dragon Axiom

On 2006-11-29, Zebee Johnstone (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

In aus.bicycle on Wed, 29 Nov 2006 14:56:16 +1000

Tamyka Bell said:

And point two - there's different acceleration due to other
forces (those nasty non-conservative ones - kinetic
friction, wind resistance...) which depend on such things as
the mass/volume/surface area etc of an object.

So unless the heavier rider is carrying the weight aerodynamically,
they'll be slower due to wind resistance?

Shouldn't all the factors combine to make the heavy one slower?

The major one is air resistance. Air resistance goes up with frontal
area, with units of length*length. Weight goes up as volume, or
length*length*length.

So the ratio of the forces is in units similar to weight/frontal area,
which are units of length, which increases as the rider's mass
increases. So a higher mass rider will experience relatively more
"gravity" than "friction", and hence will go faster downhills.

This is all assuming the rider is a spherical frictionless ball.

--
TimC
"I wish there was a knob on the TV to turn up the intelligence. There's a
knob called `brightness', but it doesn't work." -- Gallagher

On 2006-11-29, Stuart Lamble (aka Bruce)
was almost, but not quite, entirely unlike tea:

Quoted message said:

Theo Bekkers said:

Bleve said:

Theo Bekkers wrote:

Quoted message said:

> On the road, the same tactic is called tailgating. It is dangerous
> and illegal. Should an accident happen, guess whose fault it is,
> both morally and legally.

Quoted message said:

Who's fault is it?

The tailee, of course. Try running up the back of some-one in a car and
saying "It wasn't my fault".

Nitpick: if they cut in front of you and slam on their brakes?

I've had this too. Right in front of a copper. I was travelling at
100km/h in a 100km/h zone, some doofus overtook me at 110km/h,
probably barely enough to get ticketed. He passed me, switched back
into my lane, then within a second, saw the police radar in the
highway median, slamming on his brakes down to 90km/h. Glad I was
paying attention, because he didn't exactly leave me with much room
when pulling back into my lane in the first place.

Would be amusing the be watching from one of these radars, at the
numerous idiots per day you would see creating dangerous situations
just because of your presense. Alas, I didn't reach the horn in time
-- if I had, perhaps it would prompt them to add another number to the
tally "this is why cameras should be hidden, and not in plain sight".

--
TimC
"I used to be better at logic problems, before I just dumped
them all into TeX and let Knuth pick out the survivors."
-- Plorkwort, 26 September 2004 on alt.religion.kibology

TimC said:

This is all assuming the rider is a spherical frictionless ball.

What's Lance got to do with this?

monsterman said:

The problem is the injury / damage / inconvenience they cause is not necessarily compensated for by the fact that you can prove it was their fault. For example, my frame is basically irreplaceable, and I'd be pretty p*ssed if it was lost due to some attention deficient neville riding up my @rse

Exactly! I'm happy for someone to draft if they let me know they are there first and it's safe to do so, not on a crowded bikepath full of peds. If I have to brake suddenly or take evasive action I don't want someone right on my wheel without knowing. I don't want to wreck my nice rear wheel or have my expensive campy deraileur bent my some wally running up my [censored].

Fair enough ride close for a bit if you are waiting to pass, but not right on the wheel and definately not overlapping wheels. Friendly riders who want to sit in would come up along side and have a chat "hey mate I'm shagged, mind if I sit on for a bit to get home?"

If I discover someone drafting unexpectedly, I'll slowly accelerate preferably while drinking or adjusting my backpack until they aren't there anymore. It's no big deal though.

Adam

--
Frank
[email hidden]
Drop DACKS to reply
"Bleve" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Theo Bekkers said:

Bean Long said:

About 100 m
up the road he realises I'm on his wheel and then pull's slightly to
the left. I wasn't sure what he was doing exactly but I stuck with
him and just gave him a bit of room, thinking something was amiss.
Suddenly he brakes and I shoot past. Not a word from him, just hard
braking. I continued riding thinking he'd stopped to adjust his
knicks or something.
A few moments later he burls past shouting "don't draft me mate!".

Drafting is something you do on a racetrack, with people you know and

whose

Quoted message said:

Quoted message said:

abilities you trust. Cars do it, motorcycles do it, bicycles do it, even
runners do it, in racing conditions. It is an accepted tactic in racing

and

Quoted message said:

Quoted message said:

everybody does it.

When I'm riding, if someone drafts me, I don't care, it's their risk,
not mine. If I'm doing an interval around a velodrone and someone
hooks on,. unless they're doing it to use me as a leadout or something
it's a waste of their time, but hey, the air's free .. sniff my [censored] if
you like ... *I* can see what's up ahead, if they choose to trust me,
that's their judgement call. Likewise if I choose to draft someone,
it's my risk decision to suck wheel or not.

Quoted message said:

On the road, the same tactic is called tailgating. It is dangerous and
illegal. Should an accident happen, guess whose fault it is, both

morally

Quoted message said:

Quoted message said:

and legally.

Who's fault is it?

I'm trundling along in my own little world and someone hooks on to my wheel.
Unlikely, but you never know what an 82 year-old granny riding to the shop
will do :-P

I don't know the person at all. I don't know their ability to stop if I need
to slam on the brakes, I don't know if they are going to collect me from a
bad judgement call, I know nothing about eh person's abilities (or lack of).
Why would I want the risk of someone like that centimeters from my back
tyre?

Not only that but I don't ride in bunches (HATE that on cycle/shared paths!)
so my ability to deal with someone drafting is insufficient. Again, why
would I want to allow it?

Agreed, the guy should have politely declined your drafting, not slammed on
the brakes. Perhaps his bunch abilities are the same as mine; non-existent,
and he didn't know any better. Not everyone on a bike is an accomplished
rider, nor do most want to be. Most people on bikes are just riding along in
the same way thatmost people who own a football will never play 'properly',
just a kick about in the park. For most, cycling is not a sport - it's a
passtime, a hobby or a means of transport. That's not to be looked down on.

As far as fault is concerned, I see it the same as tailgating in a motor
vehicle. If you drive into the back of my car it's your fault for being too
close. Similarly, if someone drafts me (tailgates) and I have to brake hard,
it's their fault if they ride into me. Save the wheelsucking for your
training...

me (cheesed off with assumptions made about people just riding along)

--
Frank
[email hidden]
Drop DACKS to reply
"Bleve" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Theo Bekkers said:

Bleve said:

Theo Bekkers wrote:

Quoted message said:

> On the road, the same tactic is called tailgating. It is dangerous
> and illegal. Should an accident happen, guess whose fault it is,
> both morally and legally.

Quoted message said:

Who's fault is it?

The tailee, of course.

That's right ... so what's the problem if someone jumps on your wheel?
If anything goes wrong, it's their problem. (or yours, if you're the
wheel sucker)

Hmm - someone collides with me from behind at 40km/hr, I fall off. It's good
to know that my injuries are their problem...

me

Plodder said:

Quoted message said:

That's right ... so what's the problem if someone jumps on your wheel?
If anything goes wrong, it's their problem. (or yours, if you're the
wheel sucker)

Hmm - someone collides with me from behind at 40km/hr, I fall off. It's good
to know that my injuries are their problem...

I think that was a "Carl-ism" 🙄

"Plodder" wrote ...

Quoted message said:

Perhaps his bunch abilities are the same as mine; non-existent,
and he didn't know any better. ...

I can relate to that.

Before I got into road racing I knew nothing about bunch etiquette.
I assumed if someone was sitting in behind me they were just
being lazy and it [censored] me off. Didn't occur to me that they
might eventually come around and help out.

Now I could care less ... unless it's 50m from the line :-)

Plodder said:

I'm trundling along in my own little world and someone hooks on to my wheel.
Unlikely, but you never know what an 82 year-old granny riding to the shop
will do :-P

I don't know the person at all. I don't know their ability to stop if I need
to slam on the brakes, I don't know if they are going to collect me from a
bad judgement call, I know nothing about eh person's abilities (or lack of).
Why would I want the risk of someone like that centimeters from my back
tyre?

That's true and in the context of Bean's original post it makes this guy's actions all the more reckless. It's plain crazy to yank on the anchors when the guy out in front clearly didn't have a clue of the ability of the rider behind. It's just asking to be ploughed-down from behind.

Plodder said:

Not only that but I don't ride in bunches (HATE that on cycle/shared paths!)
so my ability to deal with someone drafting is insufficient. Again, why
would I want to allow it?

This one worries me. On the bike paths if I'm on someone's tail (not exactly drafting, more following their pace from half a bike length or more back) and I can't clearly see the trail ahead, I back off and let it go. This usually happens when the person I'm following catches up with other riders--if there's a bunch to begin with I don't join.

In the same way that the lead rider can't know the abilities of someone coming up behind, the draftee can't know the ability of the draftor: will they signal at all or brake and swerve with care? This is the way that "drafting" on the trails differs from bunch rides with known others: you can't rely on anyone else. If you're behind you've still got to pay attention to the track ahead, which means you can't safely be hard on the tyre ahead--you've got to be a bit futher back. If you're fourth in line, you can't see enough--and I've got my doubts about being third as well.

It doesn't happen every day, but it's not unusual to see a line of riders five long on the Yarra/Gardiners Ck trails, and from where I sit that's an accident waiting to happen.

Plodder said:

Agreed, the guy should have politely declined your drafting, not slammed on
the brakes. Perhaps his bunch abilities are the same as mine; non-existent,
and he didn't know any better. Not everyone on a bike is an accomplished
rider, nor do most want to be. Most people on bikes are just riding along in
the same way thatmost people who own a football will never play 'properly',
just a kick about in the park. For most, cycling is not a sport - it's a
passtime, a hobby or a means of transport. That's not to be looked down on.

I couldn't agree more but common sense suggests that the wisest thing to do if you're uncomfortable with someone drafting behind is to wave them through or if they refuse to go past, gently slow down until they get bored. (That said, I did get [censored] once with a clown who waved me through then proceeded to sit on my tail for a while, overtake then wave me through, only to sit on my tail again--repeatedly.)

I never ride in bunches, but a commuter can pick up a few signals just from riding around.

Plodder said:

As far as fault is concerned, I see it the same as tailgating in a motor
vehicle. If you drive into the back of my car it's your fault for being too
close. Similarly, if someone drafts me (tailgates) and I have to brake hard,
it's their fault if they ride into me. Save the wheelsucking for your
training...

I'd distinguish between following someone for their pace and truly drafting/wheelsucking/whatever. I certainly don't trust my ability to do the latter, but I generally feel pretty safe following and leading someone for pace.

In aus.bicycle on Thu, 30 Nov 2006 13:48:13 +1100

treadly&amp me said:

Plodder said:

Not only that but I don't ride in bunches (HATE that on cycle/shared
paths!)
so my ability to deal with someone drafting is insufficient. Again,
why
would I want to allow it?

This one worries me. On the bike paths if I'm on someone's tail (not
exactly drafting, more following their pace from half a bike length or
more back) and I can't clearly see the trail ahead, I back off and let
it go. This usually happens when the person I'm following catches up
with other riders--if there's a bunch to begin with I don't join.

How fast do you have to be going before drafting makes sense?

Zebee

treadly&amp said:

That's true and in the context of Bean's original post it makes this
guy's actions all the more reckless. It's plain crazy to yank on the
anchors when the guy out in front clearly didn't have a clue of the
ability of the rider behind. It's just asking to be ploughed-down from
behind.

Possible cue: TT bars suggests triathlete. Danger Will Robinson!

Donga

In aus.bicycle on 29 Nov 2006 22:22:37 -0800

Donga said:

treadly&amp said:

That's true and in the context of Bean's original post it makes this
guy's actions all the more reckless. It's plain crazy to yank on the
anchors when the guy out in front clearly didn't have a clue of the
ability of the rider behind. It's just asking to be ploughed-down from
behind.

Possible cue: TT bars suggests triathlete. Danger Will Robinson!

What, not only might he leap off the bike into the nearest puddle, but
he might be wearing bib knicks?

Zebee

Zebee Johnstone said:

In aus.bicycle on 29 Nov 2006 22:22:37 -0800

Donga said:

treadly&amp said:

That's true and in the context of Bean's original post it makes this
guy's actions all the more reckless. It's plain crazy to yank on the
anchors when the guy out in front clearly didn't have a clue of the
ability of the rider behind. It's just asking to be ploughed-down from
behind.

Possible cue: TT bars suggests triathlete. Danger Will Robinson!

What, not only might he leap off the bike into the nearest puddle, but
he might be wearing bib knicks?

No, just that he may not have much bunch riding experience. It's a
gross generalisation, of course .... but the actions described would
suggest that he didn't (who would brake-test a rider sitting on their
wheel if they had any idea about safety and bunch riding?)

Zebee Johnstone said:

In aus.bicycle on Thu, 30 Nov 2006 13:48:13 +1100
treadly&amp me <[email hidden]>

Quoted message said:

Plodder said:

Not only that but I don't ride in bunches (HATE that on cycle/shared
paths!)
so my ability to deal with someone drafting is insufficient. Again,
why
would I want to allow it?

This one worries me. On the bike paths if I'm on someone's tail (not
exactly drafting, more following their pace from half a bike length or
more back) and I can't clearly see the trail ahead, I back off and let
it go. This usually happens when the person I'm following catches up
with other riders--if there's a bunch to begin with I don't join.

How fast do you have to be going before drafting makes sense?

Zebee

I've been hoping someone knowledgeable would answer your question, but since
that hasn't occurred there's always the web, like:
http://www.cptips.com/energy.htm

About half way down the web page there is a section on air resistance, wind
and drafting. It seems to suggest there is no significant benefit of
drafting until the total bike speed relative to air (i.e. bike speed +
headwind speed) is more than 25 km/hr.

Sometimes I cycle part of the trip home with a guy from work, and when
pseudo-drafting I have trouble noticing any effect at 30 km/hr unless there
is a raging headwind. Then again, my 'drafting' is 1-2 metres behind.

There is a short section where we quite often ride at 45+ km/hr, and I find
it comfortable to let the young guy go ahead - and be mildly surprised at
how he can't leave me behind, even when he's going flat out. :-)

Cheers,

Vince

'Ecstasy#37: cycling on a long gentle downward slope with a tailwind'

I accept the logic of some of the replies here along the lines of the
drafting = tailgating safety argument, the "I just want to be left
alone" bit etc, but I wonder if some of the people who really object to
being drafted might think they're being actually slowed down by people
drafting them? So the logic goes... if the person behind is gaining
some benefit then the person in front must be paying for it. Zero sum,
no free lunch etc etc, people behind ride with less effort because the
guy in front is essentially towing them aerodynamically. Of course we
all know its [censored], but unfortunately not everyone on Earth is as
clever as aus.bicycle readers... ;-P

Travis

In aus.bicycle on 30 Nov 2006 09:56:53 -0800

Travis said:

being drafted might think they're being actually slowed down by people
drafting them? So the logic goes... if the person behind is gaining
some benefit then the person in front must be paying for it. Zero sum,
no free lunch etc etc, people behind ride with less effort because the
guy in front is essentially towing them aerodynamically. Of course we
all know its [censored], but unfortunately not everyone on Earth is as
clever as aus.bicycle readers... ;-P

Well, someone silly enough to slam the brakes on might well be silly
enough to think that!

Zebee

Bleve said:

Zebee Johnstone said:

In aus.bicycle on 29 Nov 2006 22:22:37 -0800

Donga said:

treadly&amp wrote:
> That's true and in the context of Bean's original post it makes this
> guy's actions all the more reckless. It's plain crazy to yank on the
> anchors when the guy out in front clearly didn't have a clue of the
> ability of the rider behind. It's just asking to be ploughed-down from
> behind.

Possible cue: TT bars suggests triathlete. Danger Will Robinson!

What, not only might he leap off the bike into the nearest puddle, but
he might be wearing bib knicks?

No, just that he may not have much bunch riding experience. It's a
gross generalisation, of course .... but the actions described would
suggest that he didn't (who would brake-test a rider sitting on their
wheel if they had any idea about safety and bunch riding?)

Also, except at pro level, drafting is prohibited in triathlons. The
rider in question might have been trying to enforce that rule - not
that it stops most participants drafting when the marshall is not there.

Donga said:

Also, except at pro level, drafting is prohibited in triathlons. The
rider in question might have been trying to enforce that rule - not
that it stops most participants drafting when the marshall is not there.

Maybe that was the case. Funny he slammed on the brakes instead of
telling me! :-)

--
Bean

"I've got a bike
You can ride it if you like
It's got a basket
A bell that rings
And things to make it look good
I'd give it to you if I could
But I borrowed it" Pink Floyd

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