Does drafting slow down the leader?

neil²
neil² Posts: 337
edited September 2009 in Amateur race
Greetings,

This was a discussion over the post club run beer(s) last week....

Imagine.... you as a 'normal' roadie out for your Sunday run happen to be overtaken by a TT rider; you manage to lock on and draft them for a bit. Will this affect the performance of the TT rider apart from p...ing them off?

What dyu reckon?

N²
The Riddler
The GT

Comments

  • Pokerface
    Pokerface Posts: 7,960
    edited September 2009
    I believe that the conventional aerodynamic wisdom is that drafting off someone actually increases the lead rider's speed.

    Thread on this topic here: http://www.bikeradar.com/forum/viewtopi ... t=drafting
  • MattFT
    MattFT Posts: 178
    it could actually speed him up. An area of low pressure behind the TT cyclist will actually slow him down a little. If you occupied that area and reduced the low pressure, it could help. However, I'm not sure if you get fast enough for this affect to be significant.
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  • knedlicky
    knedlicky Posts: 3,097
    From the aerodynamics aspect, I believe Pokerface (and his link) and MattFT are correct, although I think the differences are likely to be quite small unless in a trained team riding close together over a closed circuit, so not quite matching your question example.

    I’ve done to what you allude - been overtaken by a rider in a TT but managed to lock on and draft for about 4-5 km. Then, to compensate, I went in front for about 3-4 km, but he stayed 10-15 m back, as if his conscience didn’t allow him to draft. I later felt guilty about this, in case my drafting him had disturbed him. This all happened at around the one-third-point of a 50 km TT, so maybe he recovered.

    In lower category amateur races, I'm sure individual psychology affects performance of the leaders of any group more than aerodynamics, but that's another topic.
  • nickwill
    nickwill Posts: 2,735
    knedlicky wrote:

    I’ve done to what you allude - been overtaken by a rider in a TT but managed to lock on and draft for about 4-5 km. Then, to compensate, I went in front for about 3-4 km, but he stayed 10-15 m back, as if his conscience didn’t allow him to draft. I later felt guilty about this, in case my drafting him had disturbed him. This all happened at around the one-third-point of a 50 km TT, so maybe he recovered.

    I don't think it would be conscience. Drafting isn't allowed in TTs and he would have risked disqualification.
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  • neil²
    neil² Posts: 337
    Thanks, most enlightening!

    The two guys that actually did the drafting a few weeks back should be pleased that they didn't adversely affect performance of Mr T(T).

    I totally agree on the psychological bit. I'm sure that bike upgrades have at least as much effect on confidence as outright mechanical / aero performance. What's the Tom Cruise film - Days of Thunder? - where he gets given 'special' tyres. Mind you, to be honest I don't mind so much why I get quicker as the fact that I am quicker! Psychological advtage?... bring it on!!!

    Cheers!

    N
    The Riddler
    The GT
  • knedlicky
    knedlicky Posts: 3,097
    Nickwill wrote:
    knedlicky wrote:
    I’ve done to what you allude - been overtaken by a rider in a TT but managed to lock on and draft for about 4-5 km. Then, to compensate, I went in front for about 3-4 km, but he stayed 10-15 m back, as if his conscience didn’t allow him to draft. I later felt guilty about this, in case my drafting him had disturbed him. This all happened at around the one-third-point of a 50 km TT, so maybe he recovered.
    I don't think it would be conscience. Drafting isn't allowed in TTs and he would have risked disqualification.
    I know it would have been against the rules, I used to do TTs myself years ago, but I also know from duathlons, which I still do, that nowadays not everyone is so exact in what they’re prepared to risk and not to risk. Also, I don’t think it was a big event he was in, just a club internal TT, and the rider clearly wasn’t anyway going to end up on the podium if I could lead with comfort for 4 km!

    If caught, he could also have tried arguing that the rules usually forbid drafting another competitor or a known companion, and that I was just a stranger who resisted being overtaken. Even if this didn't fully wash, I don’t think he normally would have been disqualified for a first noticed offence. Instead he’d get told to stop and have seconds added to his final time, maybe based on not maintaining sufficient side distance since it wouldn't be blatant drafting behind another competitor or a known companion.

    The rule-of-thumb I know for not maintaining sufficient side distance is that his average speed is translated into seconds (e.g. if his average speed was 40 km/hr, then he’d have 40 secs added). Given the length of this particular TT (50 km), if you manage 5-10 km before being caught, the added time by this rule-of-thumb is so small, for some the risk would be worth it.

    In any case, he didn't have to stay 15 m back, he could have closed the gap to 5-10 m, depending on what the event rules were, without fear of penalty.

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