Author Topic: TDF Why so many crashes on descents?  (Read 2068 times)

TDF Why so many crashes on descents?
« on: July 17, 2011, 12:18:40 pm »
Watching Le Tour this year, I get the impression that there are a lot more crashes than usual.
I'm seeing a lot of riders' wheels going on the bends descending the mountains.
Does that usualy happen so much as it seems to in this Tour?
Chris Boardman said that it had something to do with carbon wheels. i thought about that and wondered if it was that wheels tend to have the spokes closer together in the hub because of all of those sprockets, which might make them more flexy laterally. Also, wheels seem to have fewer spokes these days too, allthough that's been going on for years, but may contribute too. Plus if they are carbon, that could make them more flexible laterally too? So whe they lean heavily into sharp bends at speed, they flex and the tyres loose their footing on the road as they shimmy, a bit like trying to corner fast on rumble strips.
Could it be carbon wheels, 11 speed cassettes or a combination of both with having fewer spokes not helping much either?

Or was Boardman wrong and the roas are more slippery, or are the number of crashes the same as any other year?

Biggsy

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Re: TDF Why so many crashes on descents?
« Reply #1 on: July 17, 2011, 12:24:07 pm »
Sounds bollox to me.

The riders are just pushing the limits because their living depends on it.  It's shocking how much risk they take.

I haven't been watching enough this year to see any spectacular crashes yet - just loads of unspectacular ones in crowded bunches - that we always get several a day of every year.
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LittleWheelsandBig

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Re: TDF Why so many crashes on descents?
« Reply #2 on: July 17, 2011, 12:34:37 pm »
Deep section rims are more affected by wind gusts and carbon rims can give 'grabbier' braking (depending on pad material and rain). I'm not sure any other factors have changed much over the past couple of decades.
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citoyen

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Re: TDF Why so many crashes on descents?
« Reply #3 on: July 17, 2011, 12:40:40 pm »
The explanation I've heard for the carbon rims issue is that it's to do with braking - something to do with the way they behave when hot, snatching and fading unpredictably.

Whether or not there's any truth in this theory, I have absolutely no idea, but it does sound like a plausible explanation for why such a competent bike handler as Jens Voigt would lose traction at low speed, which is what happened in his second crash yesterday.

d.

Re: TDF Why so many crashes on descents?
« Reply #4 on: July 17, 2011, 12:42:10 pm »
The criticism I have heard about carbon wheels is not that they are too flexible, but the opposite i.e. that they are too stiff and that when they hit a bump or whatever they don't absorb any of the shock they just bounce.   There was an incident a couple of years ago in one of the spring classics when there was an enormous pile up descending cobbles and a theory then was that the riders lost control because the front wheel was bouncing about.
There was also a suggestion when Geraint Thomas went off the road descending from the Tourmallet that the braking can be a bit hit and miss.   

Re: TDF Why so many crashes on descents?
« Reply #5 on: July 17, 2011, 12:49:00 pm »
How about the ones that lose their wheels on bends when they are in a line and everyone else stays up? There must be a reason why 6 people make the bend without a slip, but one of them doesn't.
There always has and always will be crashes, but it just seems a lot worse this year, to me. Could be just me.

Deep section rims are more affected by wind gusts and carbon rims can give 'grabbier' braking (depending on pad material and rain). I'm not sure any other factors have changed much over the past couple of decades.

That makes sense. It always seems to be the one at the back that crashes. They'd be braking the most.
There have been a few time when someone has crashed twice, the second time being not long after their first. Maybe because they are being a bit more carefull and braking a bit more after their first crash?

Re: TDF Why so many crashes on descents?
« Reply #6 on: July 17, 2011, 12:50:09 pm »
Carbon wheels aren't too hot against dogs either...

Those wonderful norks are never far from my thoughts, oh yeah!

Re: TDF Why so many crashes on descents?
« Reply #7 on: July 17, 2011, 12:58:51 pm »
The criticism I have heard about carbon wheels is not that they are too flexible, but the opposite i.e. that they are too stiff and that when they hit a bump or whatever they don't absorb any of the shock they just bounce.   

I thought you could do anything with carbon if you weave it correctly. Carbon can be flexy, so I've heard. Never used carbon myself though. Old school aluminium rims and stainless spokes can be stiff too, or can carbon be much stiffer?
I was thinking more of lateral flexing and that leaning into a bend heavily would put more strain on one side of the spokes. Could be totally wrong there though. Thinking about it, I probably am because there would probably be a lot of slipping on velodromes when they ride slow enough not to be perpendicular to the banking.

Dodgy braking seems more likely to me now.

Gus

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Re: TDF Why so many crashes on descents?
« Reply #8 on: July 17, 2011, 02:34:23 pm »

Too high speed and lack of feeling when breaking.
Stiffer frames  ???

Take a look at Laurens Ten Dam after he overshot
a turn on the decent of Col d'Agnes  and landed face first in the ditch.

IanDG

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Re: TDF Why so many crashes on descents?
« Reply #9 on: July 17, 2011, 03:04:38 pm »


Stiffer frames  ???



I've seen this mentioned as a reason elsewhere

border-rider

Re: TDF Why so many crashes on descents?
« Reply #10 on: July 17, 2011, 03:09:58 pm »
Voigt's back wheel just seemed to slide out on tiddly bit of  wet on a dryish road yesterday.  I wonder if they're running a harder tyre compound or somesuch.

Re: TDF Why so many crashes on descents?
« Reply #11 on: July 17, 2011, 06:54:29 pm »

Too high speed and lack of feeling when breaking.
Stiffer frames  ???

Take a look at Laurens Ten Dam after he overshot
a turn on the decent of Col d'Agnes  and landed face first in the ditch.

I think he just misjudged the corner.

Rig of Jarkness

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Re: TDF Why so many crashes on descents?
« Reply #12 on: July 17, 2011, 07:02:52 pm »
Some of the wheels they're using these days are so expensive that perhaps they don't get to ride them very often, ie. only on special days on special races.  So if they're used to something else with slightly different handling then could that explain it ?
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Re: TDF Why so many crashes on descents?
« Reply #13 on: July 17, 2011, 07:07:03 pm »
Voigt's back wheel just seemed to slide out on tiddly bit of  wet on a dryish road yesterday.  I wonder if they're running a harder tyre compound or somesuch.

I'd agree if it was a one off. It does always seem to be the one at or near the back, who would be braking the most. It did look like a damp patch of road to me too though, but the others all got round OK.
It also seems to happen before they really hit the bend, so could still be braking, especially at the back of a small group.
I am a bit surprised that it's known for carbon rims to grab or judder, but they are still being used. I wouldn't want brakes like that just for riding, let alone racing down mountains!

peliroja

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Re: TDF Why so many crashes on descents?
« Reply #14 on: July 17, 2011, 07:27:26 pm »
There was also a suggestion when Geraint Thomas went off the road descending from the Tourmallet Horquette d'Ancizan that the braking can be a bit hit and miss.   
;)

Signed, A Pyrenean Pedant.  :-[

Pingu

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Re: TDF Why so many crashes on descents?
« Reply #15 on: July 17, 2011, 11:11:38 pm »
There was also a suggestion when Geraint Thomas went off the road descending from the Tourmallet Horquette d'Ancizan that the braking can be a bit hit and miss.   
;)

Signed, A Pyrenean Pedant.  :-[

 :thumbsup:

I remember when we descended the other side of that a couple of years ago there was a lot of grit on the road. On the north side there were a lot of animals which may have left some deposits.

Re: TDF Why so many crashes on descents?
« Reply #16 on: July 18, 2011, 08:14:45 am »
 Posted by: Pingu
« on: Yesterday at 11:11:38 PM »
 There was also a suggestion when Geraint Thomas went off the road descending from the (Tourmallet) Horquette d'Ancizan that the braking can be a bit hit and miss.
You're right, a senior moment!   But I'm going to have another go, regarding Voigts first excursion off the road.   If I remember correctly, he had to have a rear wheel change before he got back on the bike.   Could it be that he had a rear wheel puncture before the corner and decided to continue in a straight line rather than try to make the corner on a flat tyre? 
 


peliroja

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Re: TDF Why so many crashes on descents?
« Reply #17 on: July 18, 2011, 10:49:01 am »
There was also a suggestion when Geraint Thomas went off the road descending from the Tourmallet Horquette d'Ancizan that the braking can be a bit hit and miss.   
;)

Signed, A Pyrenean Pedant.  :-[

 :thumbsup:

I remember when we descended the other side of that a couple of years ago there was a lot of grit on the road. On the north side there were a lot of animals which may have left some deposits.
That was a great ride. :) Good memories.

The Horquette d'Ancizan road is a scenic detour/used by farmers and not as much of a general thoroughfare as the Col d'Aspin, so there is often a lot of mousse de vache and grit on the road.

andygates

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Re: TDF Why so many crashes on descents?
« Reply #18 on: July 18, 2011, 12:20:22 pm »
Grit in bad places on a mountain road is as much a part of the Tour as pavé is on the Classics - these are live roads, real roads, and not a pristine racetrack.  Ditto the bollards and dogs and fans... managing these risks, and daring the Devil, is what makes for heroes and victims.
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Re: TDF Why so many crashes on descents?
« Reply #19 on: July 18, 2011, 12:28:12 pm »
On French TV, Bernard Hinault said that he thought the teams were riding with tyres at too higher pressures, and that this was contributing to the grip issues on corners. The point of contact between tyre and road must be tiny, so any bounce will cause issues

Re: TDF Why so many crashes on descents?
« Reply #20 on: July 18, 2011, 12:31:05 pm »
Sounds likely. Someone posted a link to a blog/interview with a rider where they discussed Michelin forcing them to ride on lower pressures (the riders objected, thinking it would slow them down). The rider said they found that on the descents, they were pulling away from other riders.

Hinault might know what he's talking about.
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citoyen

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Re: TDF Why so many crashes on descents?
« Reply #21 on: July 18, 2011, 01:27:11 pm »
"Bernard Hinault said that if you don't let some air out of your tyres, you'll probably end up riding for Raleigh Banana."

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d.

TDF Why so many crashes on descents?
« Reply #22 on: July 18, 2011, 01:36:18 pm »
There was the striking point that Thomas and Voeckler both had problems at the same spot, which suggests that road conditions were a factor.