Also on descents like that you have to take into account of acceleration out of corners, every corner which takes alot out of you and also pedalling upto a speed where freewheeling is more aero which is where pro’s make up time

I suppose it must depend on where you ride and the type of riding you do to a certain extent. I clock 45+mph (50 on a good day) on my commute home across the Quantocks and don’t think a lot of it (apart from when it’s raining and dark) If I ride an alternate route 60+mph is easily possible.

Having almost no experience on a road bike I would either drag my brakes like a BGB the whole way down or crash horribly at the first bend

Slow, that’s how we’d compare. Compared to a pro like Sean Yates, absolutely glacial.

I’ve ridden a couple of descents in the Alps after seeing the pros do it. I thought I was quick on a road bike going downhill till I saw how they leant into and accelerated out of corners.

Would not even want to try on tyres not much wider than a gnats chuff,rim brakes and that awfull hunched riding position (probably shit myself)
Give me 2.4 tyres, 180mm disc brakes,710mm bars and a nice comfortable sat up riding position any day of the week

😆 @ Dibs comparing the quantocks to an alpine road descent 😆

I’m a pretty compitent descender/cornerer on an mtb and have descended tour route roads in both the Alps and Pyranees and know fine I couldn’t keep up with pro roadies on a long road descent even if they freewheeled the entire thing.

😯

[video]http://www.youtube.com/watch?v=-kZSzB4kEE8[/video]

yunki – Member

I would leave them gasping and astonished in a cloud of dust..

Me too- after going straight on in the first corner. “Why did he do that?” they’ll gasp in astonishment as they ride through a cloud of dust.

Let me at ’em….

Is it wrong that I much prefer a fast road descent that a mtb descent?

I think most of us would be pants to be honest, those guys are on the edge and thats all they do, great footage today on Eurosport would have loved to have ridden over that course, obviously somewhat slower than the pros and probably stopping off in that guys driveway for a rest or to let the brakes cool off.

I’ve never gotten scared when descending, not even when i was tucked at 50mph. I even tried to spin to go faster but my legs wouldn’t go fast enough.

[video]http://www.youtube.com/watch?v=RxXqQqAc2pA[/video]

I suppose it must depend on where you ride and the type of riding you do to a certain extent.

Yes, the Quantocks are the only area in the Uk that can adequately prepare you for an Alpine descent.

as most on here have more gravity acting on them they would both go faster and bounce further on crashing 😉
Me i would be scared about 50 mph ish and back off so would get dropped quite quickly.

I regularly hit 50mph (road bike) on a particular hill near here. It’s a pretty straight, wide and smooth main road. A few mph over 50 is about as fast as I can physically spin with 52/11. Do they fit 53’s for the mountain stages?

I have to say when I top out and stop putting in effort and start thinking about what i’m doing, I look at my skinny little tyres and think ooooooh sh!t. . . .

In the vid clip above the guys are freewheeling at 100km/h and touching each others bums ffs!

I rode down Alpe D’ Huez (before I rode up it) and it was pretty cool. But . . . the corners are sharp, the tarmac is smoooooth and the drop is steep. You can big-ring it out the corners and your at 40mph in seconds – just as the next bend appears.

On a technical descent like todays I would have ridden into that guys carpark, through the wall and off down the mountain . . . . never to be seen again!

EDIT: It must help knowing for sure that nothing is gonna come round a bend towards you too??

Quantocks vs The Tour

I think Cothelstone hill was classified grade 2 in a recent Tour of Britain. Obviously much shorter though.

I’ve peaked ~45 mpg down Bristol Hill into Wells on my Charge Tap road bike, and it was fun as the bends are quite gentle. Cheddar Gorge has some steep bends and is much more worrying. I’d be terrified on a skippy racing bike. No way I’d want to go much faster.

Also when I crash I tend to lie there for a while, eventually get up, brush myself down, check the bikes ok, check I’m ok, moan a little, make up an excuse as to what caused me to crash (obviously wasn’t my fault), then maybe get back on the bike and pootle off back down the hill, taking it easy.

They don’t tend to do that in the TdF – or at least the cameras don’t show it.

Re the Physics – air resistance is proportional to the frontal AREA of a rider, gravitational acceleration is proportional to the mass which is proportional to the VOLUME of a rider*.

Area increases as the square of linear dimensions (aka ‘size’)
Volume increases as the cube of linear dimensions.

So a rider twice as tall would have four times the wind resistance and nine times the gravity assist downhill.

* assuming equal density.

That guy on the yellow bike was incredible.
Loved the way he was out of the saddle sprinting, where I’d be braking. 😀

I have two points to make 1:ex mtbers are better descenders my arse and secondly most people on here talk complete shite about anything relating to road riding.
YOU WOULD ALL BE SHIT COMPARED TO THEM ALL end of story

and nine times the gravity assist downhill.

Careful now, things of different masses will roll down the hill in the same time. It’s just the ratio of mass to surface area that causes heavier riders to go quicker.

I think.

I have to say when I top out and stop putting in effort and start thinking about what i’m doing, I look at my skinny little tyres and think ooooooh sh!t. . . .

Yep. Done this many, many times. Everything’s fine until I start thinking about it.

Incidentally the fastest I’ve ever done was around the quantocks too, ‘fraid I don’t know the hill as I was being guided around by a mate but I did have a speed wobble on the fastest section which does focus the mind a little. It was a long time ago but I think the speed was in the low 50’s mph, certainly not topped it since, best I can get to locally is about 50 kph.

RealMan – Member
Also when I crash I tend to lie there for a while, eventually get up, brush myself down, check the bikes ok, check I’m ok, moan a little, make up an excuse as to what caused me to crash (obviously wasn’t my fault), then maybe get back on the bike and pootle off back down the hill, taking it easy.

They don’t tend to do that in the TdF – or at least the cameras don’t show it.not only am I shit, I’m also a bit of a pussy.

FTFY 😉

Are we allowed to use hydraulic discs? Because as we’ve all agreed in previous posts, they’d be better on road bikes.

thats why the MTb’er who won this was running discs, oh wait…

[video]http://www.youtube.com/watch?v=uwseIy89_fc[/video]

Thank you GW 😆

1:ex mtbers are better descenders my arse

C.Boardman, I think, attributed Cadel’s excellent descent yesterday to his mountain bike skills, since Cadel won two XC world cup races prior converting to road. And since Boardman is an ex World Champion himself, I’d be concerned about your arse 😉

I’ve decended Alpe D’Huez twice, once just getting a lift up to ride down. Didn’t have a speedo but on the only section where you could go really quick was over 60+ as left the car for dead. The speed didn’t bother me being a ski racer at the time, if any thing wanted to.go quicker.

Pros would be quicker as they can accelerate out of corners quicker.

For me, it’s a combination of the traffic and the road surface that makes a descent scary (or scarier). The first few rides on carbon forks were an eye opener too! 😯

I’m not keen on the tendency locally to repair worn out roads by spraying 15-20mm chippings onto tar – that’s really horrible to ride on, and it ruts quickly from being compacted by traffic (not deeply it must be said, but riding on 25’s you don’t have much to play with). Anyway, all that aside, I’m in the ‘I’d be crap’ camp.

😉

FunkyDunc is that kmh or mph?

I’d really like to see someone hit 60/100 on the Alpe straights are just not long enough IMO I’m not saying you didn’t do it – but it would be a stellar performance

(I would not rely on cars as they do not do 100kph down the Alpe)

It’s incredibly hard to get over 52ish mph on a road bike – the aerodynamics are so against it – and the gradients are really not that steep in France as the roads are so well made.

That 112kph of Thors the other day is an exceptional speed, he is a big guy, with exceptional skills – even among the elite descenders.

The MTB rider makes better descender line is BS when comparing pro roadies – what does A Schleck do in the off season – and The Chicken was ex MTB and his bike handling was a joke.

And roadies bike handling is much better than MTBers give them credit for – when I crossed over I was expecting to be embarassed but now I’ve been doing it for a bit think most riders are crap as well as slow and unfit. Obviously there are exceptions… That said my road bike descending has improved a lot since coming over, but I attribute a lot of that to jedi’s coaching

Hmm that WOUld have ben beter wiv raNdom CAPs and no grammer

Anyway those of you that really have done 60mph on a road bike – I salute you

Buzz-lightyear – Cadel didnt win two world cup races – it was two world cup series that he won.

Yes of course we would be shite but I think the relative position still exists further down the food chain. When I go out with my roadie mates several of whom are good triathletes, they thrash me into tiny pieces on the climbs but on the downs they are like a pensioners bingo outing. They do realise this and are taking lessons from a motorbike racer in an attempt to go down faster [oops]. Unfortunately the time I lose flogging up a big long climb is far more than they lose going down, still it’s nice to be in front once or twice a day.
PS wouldn’t disc brakes allow everybody to descend faster?

Careful now, things of different masses will roll down the hill in the same time. It’s just the ratio of mass to surface area that causes heavier riders to go quicker.

I think

That’s what I am saying. Taking arbirtary units, that ratio would be 1:1 in any given rider, and 4:9 in a rider twice the height.

I have peaked at 55mph riding off the Mendips on a tt bike with tri bars using 55×11. The fastest I have done was 60mph coming off Dartmoor after the finish of the Devil Audax

We’d be rubbish and slow, just like trying to keep up with Cav on the climbs, he’d still hand you your ass

Mph. The first few bends down have reasonable straights before the next village bit.

You can get 60 mph down a small hill in to Otley, Leeds too its not really the length that matters its the steepness and getting speed up quick.

Re the Physics

Lets put two rider with the same bike at the top of the same hill.
With no air resitance, the only work they receive is the work of gravity:
for rider one:
1/2m1*Vendofthehil²=m1*g*height of the hill
for rider two:
1/2m2*Vendofthehil²=m2*g*height of the hill
As you can see you can remove the weight in both equation, therefore they will it the bottom at the same speed.
Now perform this on earth you must add wind resistance: F 1/2*S*C*V².
so for rider one:
1/2m1*Vendofthehil²=m1*g*heightofthehill-1/2*S*C*V²
and for rider 2
1/2m2*Vendofthehil²=m2*g*heightofthehill-1/2*S*C*V²

Which arise the question, whom, of the two rider has the biggest S*C coeff 😉

I have done one big alpine pass. I was descending at 50 ish mph in places, these guys do 70 mphish.

None of us could get close to them

C.Boardman, I think, attributed Cadel’s excellent descent yesterday to his mountain bike skills

well Chris Bordman is talking out of his arse as the two skills are very very different. Was Lance MTBer first? Was Salvodeli, Hushovd, Spartacus? Cadel is a good descender because he has those skills and no doubt works at them having been a top mtber has no influence on it at all. Millar was a BMX racer and mtber in his youth and was shocked by the speed of the descending in the pro races.
Its just a lazy line that presenters use.