[route149]

When I was a kid, I had a book called the World's Fastest.  It described riders in the Tour de France hurtling down hill at 60 mph while casually adjusting the saddle with one hand on the spanner...

Whatever.  Implausible as this description clearly is, what da foch is da highest downhill speed recorded?  My wife says it's something like 100 Km/hr, but I am having problems getting hard data.  (btw, I once dared myself to go as fast as I could stand down the Ringinglow Rd... and was staggered to see that I whimped out at just 34 mph, which felt terrifyingly fast.)

Any one have a secret stash of Tour de France stats?  And what's all this bollox or truth about not being able to brake too hard because you overheat the rims and the tyres burst? Truth or fiction?  If so, why aren't there wheels that can dissipate heat better?

Go on, you know you want an audience.

[slackline]

It ain't the Tour, but this nutter gets to ~130mph (210.4kmh) on a bike in the snow 

[Palomides]

I don't have any past info, but I have a couple of friends who did l'Etape du Tour on Monday - it was the Montelimar > Mt Ventoux stage the pros are doing this Saturday.

The final descent from the Col des Abeilles (sp?) down towards Bedouin before the climb up Ventoux is down a big, fast major road. My friends clocked 75 km/h, and I'd expect the pros to go quite a bit faster.

[webbo]

heat doesn't cause tyres to burst it melts the glue that holds on tubular tyres so they then tend to roll off.this is usually caused be excessive air/road temps rather than excessive braking.

[matthew]

heat doesn't cause tyres to burst it melts the glue that holds on tubular tyres so they then tend to roll off.this is usually caused be excessive air/road temps rather than excessive braking.

I hate to disagree but yesterday on ITV4 coverage of the Tour they specifically said that overbraking causes excess heat and tyre bursting situations....

[fatboySlimfast]

It ain't the Tour, but this nutter gets to ~130mph (210.4kmh) on a bike in the snow  

Nice bike.....Id like one in black...

[Percy B]

Lots of heavy braking (like you might do on a long technical alpine descent) does cause your bike rims to get very warm indeed. This can cause a couple of problems. Firstly, if you have pumped your tyres up super hard, then the air in the tubes will heat up and expand even more making you more likely to puncture, have a blow-out, or just pop your clincher tyres off the rim of your wheel. Secondly, as Webbo pointed out, you can make the glue that bonds tubular tyres onto the wheel rims go all spoogy as it gets hotter, and the tyre will come off the rim when you corner or brake. Whichever way, its not going to be much fun.

Best ways around these scenarios is to ride on tubular tyres that are well glued (and not taped) to your wheel rims, use alloy rims and not carbon ones, run your tyres at a slightly lower pressure than you do on the flat, and avoid loads of heavy braking. That way you shouldn't have any problems, but should you puncture you should still have some control over the bike (the joy of tubular tyres), unlike when you have a puncture at speed on clincher tyres which normally means inevitable heavy contact with the tarmac.

All these thoughts are always brought to the forefront of my mind (for some bizarre reason) when descending really fast - I hit just over 85kph on the descent of the Croix de Fer last autumn (well over 50 mph for the old skool), and the pros have been descending in the mountains in this years tour at well over 90kph in places. Makes that footage of Jens Voigt's crash yesterday seem even more unpleasant when you think about landing on your face at that sort of speed!

[clm]

Max speed is not really recorded.  max average is by Chris Boardman - prologue timetrial

[route149]

  max average is by Chris Boardman - prologue timetrial

What?  Jeez, I didn't know he  was ever that good! 

[webbo]

  max average is by Chris Boardman - prologue timetrial

What?  Jeez, I didn't know he  was ever that good! 

despite him being olympic and world pursuit champion and the world hour record holder in both versions.

[Duma]

Eurosport commentary said Cancellara was clocked at over 100kph after he punctured and had to rejoin the peleton on stage 7. Think Cofe posted a vid over on the TdF thread.

[route149]

Eurosport commentary said Cancellara was clocked at over 100kph after he punctured and had to rejoin the peleton on stage 7.

Saw that.  Scary!

[chappers]

i was pretty proud of myself this week for doing 80 km/h on the decent from the Col d'Izoard. then i thought how stupid i had been!! too busy looking at my computer at that speed, a puncture could have been the end of me!

[Joepicalli]

I managed 82kph down Scotsmans pack hill t'other day, that was fun.