TdF time trial

[spider2106]

I watched the TdF time trial today, the teams go to huge expense in money and time to gain every possible aerodynamic advantage, I noticed that a lot of the riders had standard biddons , I can't understand why a fully hydrated rider would need a drink over an approx. 20 mile time trial given the extra drag it must make.

On the other hand the big ,well organised teams must have some good reason to do this ? can anyone explain please?

[Cyril Haearn]

Justin case
Could you see what was in the bidons?
Food and drink for the riders are planned very precisely, maybe they cannae go 40 mind without, they must take on energy
Mind, one should be able to ride 40 minutes without sitting up, taking a drink could cost many seconds

[reohn2]

a)Drink is needed in such a solo effort race distance.
b)Bidon's are a standard size and handled on a daily basis maybe a hundred(?)times a day,something unfamiliar to handle whilst on the absolute limit,not to mention an unfamiliar cage to take it from and replace in,may outweigh any aero advantage.
A dropped bidon is a useless bidon.
c)aerodynamic bidons used to be banned at one time I think.

[RickH]

The top GC guys didn't appear to have bottles (or cages) on their bikes for the TT.

[Ray]

I noticed at least one with disc brakes. Little to be gained in a TT, I would have thought. And aren't they heavier? Less aerodynamic?

[RickH]

I noticed at least one with disc brakes. Little to be gained in a TT, I would have thought. And aren't they heavier? Less aerodynamic?

It's easy enough to make bike that is lighter than the current UCI minimum weight so it doesn't really matter how you make up the weight to the limit.

I've read that some of the newest aero bikes are actually more aerodynamic as they have been designed with discs from the start & so can concentrate on smoothing out all the bits where rim brakes would have gone & where the discs are now. (Interesting to note that Chris Boardman - in his "tunnel vision" pieces on the TdF coverage on ITV4 - reckoned that clothing has probably had a bigger aero effect than the bike design.)

[Brucey]

disc brake wheels are less aero, that is why they are not used (except by Sylvan Chavanel, who presumably took the money for so doing and added it to his retirement fund...). Simples.

If you want to make a TT bike aero, you can hide rim brakes in the frame/fork. Discs and disc calipers stick out, of necessity; the idea that you can make them more aero than rim brakes is

a) almost certainly wishful thinking on someone's part and
b) it definitely hasn't happened yet, else they would all be using them.

On the track, the bike has ~10% of the aero drag and the rider has ~90% of the aero drag. Probably on the road this is about the same.

If you can reduce the aero drag of the bike by 10% that is 1% total aero drag reduction. To have a similar net effect by reducing drag on the rider, you only need to change the drag on the rider by ~1.1%; this is well within that which might be achieved by using fancy clothing.

cheers

[NATURAL ANKLING]

Hi,
Socks are UCI regulation length.

[Postboxer]

If the bike is only 10% of the drag, how much can the disc brake make up? Are there gains in other areas when having disc brakes, better, more assured braking into corners, lighter rims so faster acceleration out of corners, faster climbing perhaps?

I thought this thread was going to be about what on earth went on with the timings, it looked like they were making them up, I even looked back at Froome and Dumoulin starting the TT, timing 4 minutes between them then fast forwarded to the end just to check, all seemed ok, Froome's clock stopped before he got to the line, a policeman had stood on the sensor.

[Brucey]

If the bike is only 10% of the drag, how much can the disc brake make up? Are there gains in other areas when having disc brakes, better, more assured braking into corners, lighter rims so faster acceleration out of corners, faster climbing perhaps?

'not really', not at that level, anyway. The rims don't have to last long with rim brakes so there is no real weight saving, TTs tend not to put a heavy emphasis on braking and cornering either; if they did then a simple gain would be to allow faster cornering by having a machine that handles more like a road bike and an improved choice of riding positions that allows better control on the brakes and/or in the corners. As it is, the aero gains arising from having a really uncomfortable riding position with a bad weight distribution and a bike that has rubbish steering absolutely overwhelm gains that might arise from such things in most cases; the most that is usually seen is a brief use of the cowhorns on the brakes and in the corners. This can slow you down if you do too much of it; no one has come up with an aero riding position that allows good steering (not on a conventional bike, anyway).

I thought this thread was going to be about what on earth went on with the timings, it looked like they were making them up, I even looked back at Froome and Dumoulin starting the TT, timing 4 minutes between them then fast forwarded to the end just to check, all seemed ok, Froome's clock stopped before he got to the line, a policeman had stood on the sensor.

yes, I thought it was very odd for a few minutes but then looked at the VT and thought that there must be a reasonable explanation. It seems a bit mad that the same system that generates the official times is not used for generating the times seen on TV though.

cheers

[JamesE]

It's easy enough to make bike that is lighter than the current UCI minimum weight so it doesn't really matter how you make up the weight to the limit.

IIRC (can't find the source now) time trial bikes are around 8-9kg thanks to deep section rims, disc rear wheels, larger tubes in order to get the aerodynamic profile etc etc. (Hence the bike swaps on TTs that end on a big climb, like last year's World Championships).

[pjclinch]

It's easy enough to make bike that is lighter than the current UCI minimum weight so it doesn't really matter how you make up the weight to the limit.

IIRC (can't find the source now) time trial bikes are around 8-9kg thanks to deep section rims, disc rear wheels, larger tubes in order to get the aerodynamic profile etc etc. (Hence the bike swaps on TTs that end on a big climb, like last year's World Championships).

Boardman was commenting on the differences between TT and road bike during commentary on ITV4, and while he suggested they were heavier it was also handling and riding position that made climbing harder, and he also pointed out the podium at Bergen consisted of people who'd ridden their TT bikes the whole way.

Pete.

[thirdcrank]

There are plenty of people who base their equipment choices on what élite riders use. I can't help feeling that the élite riders base own their decisions on stronger evidence of what gets them round fastest.

[Brucey]

There are plenty of people who base their equipment choices on what élite riders use. I can't help feeling that the élite riders base own their decisions on stronger evidence of what gets them round fastest.

pros are often paid to use stuff; they don't always get to choose what they really want. On the other hand elite riders don't always have the money to get what they want either.

One thing that did surprise me is the number of professional teams that actually pay money for their groupsets (even if they have a bike sponsor that supplies framesets and/or money to the team). I guess even they can be offered 'deals' and incentivised to use particular equipment though.

cheers

[thirdcrank]

In the days when I used to read everything avidly, I remember an article in the comic about Raleigh TI team equipment and they made a lot of economies like using steel BB spindles rather than titanium. I still think that the choice of things like what type of bike is used for a TT is driven by what goes fastest.