On an inclined plane a riders weight will have an effect on how quickly they accelerate horiontally (it's not the same as freefall), a smaller rider however will be likely to be more aerodynamic, and will thus have a higher "terminal velocity".
Gravity Assisted tarmac racing anyone?
Oloivered - nope - the bigger rider will go faster as they are heavier. The increase in weight is greater than the increase in air resistance.
Try free-wheeling downhill alongside a mate - the fatties go faster - thats why tandem are a lot faster downhill - 60% higher terminal velocity
TJ is right - this time 🙂
I agree fatties accelerate faster, and this has the larger effect. (Probably wasn't clear on this before) but the terminal velocity is dictacted solely by the drag and eventually would favour the skinnies (altough this is probably a long way past where mortals fear to tread)
Do all pro roadies spend a lot of time descending ?
Do they all go off training in mountains etc ? (can't be for the altitude benefit, since their haematocrit is "optimal" anyway)
Surely it's not that helpful for the majority of races (or are there one day pro races that go up & down mountains ?)
Well yesterday's tour stage went up and down a mountain, as did today's, and tomorrow's goes up three mountains and down two. So I'd say it's a pretty helpful skill to have, yeah.
Every stage is a one day race, winning a stage on the tour is bigger than most one day races (classics and monuments excepted).
so, here are the assumptions on my part:
in a really good pro's year there might be what, twenty or possibly thirty big mountains (if they ride 2 big tours) ?
of all riders in the big tours, maybe 5-10 can REALLY make a big showing there
if descending skills probably hardly ever actually win races (look at today - 20 secs to contador and then he got caught by a chaingang), the only way it's worth picking them up is as a side-effect of climbing long hills, rather than training specifically
I reckon if I was in charge I'd make my team concentrate on riding flat & rolling stages rather than poncing about on big mountains, unless I had a genuine GC contender or an already proven climber
if these assumptions are true, why/how do pros learn to descend so much better than amateurs ?
I'm about 4/5 stone heavier than my mate, i always roll faster than him, by quite abit too. In general I find it much easier to get away from or to overtake him on a downhill, conversely he destroys me uphill by a huge margin, it really doesn't balance itself out in that respect! 😥 
so if it's noticable on rough mtb ground, the difference on the road must be much more pronouced.
I agree fatties accelerate faster, and this has the larger effect. (Probably wasn't clear on this before) but the terminal velocity is dictacted solely by the drag and eventually would favour the skinnies (altough this is probably a long way past where mortals fear to tread)
Terminal velocity is a free falling term I think, so not to get confusing I'll say max velocity.
Max velocity occurs when acceleration = 0 - the forces are balanced. So you will have a weight component, and an air resistance component.
The rider with the bigger weight will be able to go faster if the air resistance is the same between both riders.
If it's different, then it depends on how different it is, but in real life, I think bigger riders have a higher maximal velocity - within reason.
So whoever is more dense can go down hill faster?
😉
On the tandem we have twice the mass but only the same wind resistance as I do on a solo. we go much faster downhill. s a slope I hit 40+ on the solo we hit 50+ on the tandem- both times reaching terminal velocity for that slope
Logic as real man says
Following two mates on a tandem down Kirkstone doing the Whitton a few years back we klicked 58.9mph i would have not gone that fast if i had not been in the slip stream Tandems rock down hill.
As far as I'm aware 50mph (or 60mph) is the same speed wether you do it on the Quantocks or the Alps, and it still surprises me that people post on here that they've never been faster than 45mph etc.
I think i'd go faster if people didn't keep calling it [i]terminal[/i] velocity.
So whoever is more dense can go down hill faster?
Yep, a 15st muscle man will be faster than a 15st lardy, in theory.
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
Have you read the thread? No one is actually saving normal riders would stand a chance.
PS wouldn't disc brakes allow everybody to descend faster?
A good set of road brakes can lock up the wheels fairly easily, why would you need any more than that? Suspect the amount of usable power from discs would be pretty minimal as you really don't want to lock brakes on the road. Guessing they will start appearing on low end bikes soon as they will be a lot more confidence inspiring than crap road brakes for new riders.
The pros will have trained how to corner at some point in their career, the descending skills will come from that and time spent doing it. If a pro was so slow they were always getting dropped they either wouldn't get a team ride or would be given training to sort it out.
if these assumptions are true
they are not end of story. Whilst being shit hot at descending can not often win you a race being shit can easily stop you winning it.
Just look at the places most pro' choose to live and train to get an idea of the terrain they train on. Some of the one day races have some terrifying descents on cobbles for example, you need skill to ride them even if they are not super long alpine descents.
A good set of road brakes can lock up the wheels fairly easily
In the rain? I doubt it.. admittedly I only have 105 brakes but in reasonable rain I pull the brakes and literally nothing happens at all for a good ten or twenty yards. I'm guessing it could be different with new rims, new blocks, and dura ace though.
In the rain? I doubt it.. admittedly I only have 105 brakes but in reasonable rain I pull the brakes and literally nothing happens at all for a good ten or twenty yards. I'm guessing it could be different with new rims, new blocks, and dura ace though.
Ultegra ones don't seem to have much of a problem with it. Then again, in the rain I will be pulling the brakes on early and really trying not to lock up. Haven't had the same 'shit, I'm not stopping' moments I used to get with Tiagra brakes anyway.
I have done one big alpine pass. I was descending at 50 ish mph in places, these guys do 70 mphish.
Yeah, but they have drop bars and an aero position. See also how them hitting 60+ regularly (let alone 70) is BS. Anyway, it's not the speed on the straights that's the issue, it's the speed they corner at (and managing that for 15-20 minutes continuous when knackered from the climb).
I'm way too scared to go past about 45 kph on any bike in any kit on any surface/trail. 😳
... although we would all easily be faster than Andy 'Boo Hoo, Pedallling Down a Big French Hill is Really Dangerous' Shrek
[url= http://www.guardian.co.uk/sport/2011/may/09/wouter-weylandt-giro-ditalia ]Wouter Weylandt RIP. This may be why they are a little sensitive.[/url]
No one here would touch the slowest in the peloton.
Haven't had the same 'shit, I'm not stopping' moments I used to get with Tiagra brakes anyway.
Change of pads and a degrease of the wheel rim sorted my 105s that were a little tame to start with. Still not brilliant in the wet, but I mince about in the rain anyway.
if these assumptions are true, why/how do pros learn to descend so much better than amateurs ?
They ride a lot more than amateurs. See if you can find the GPS tracks of the pros in training on Strava or a similar site; they really do put the miles in and if they're going up hills, they're coming down a lot too.
Stokes theorem states that for a sphere falling througha viscous liquid the terminal velocity is proportional to the radius.
It proably not too hard to go from there to the idea that larger riders will reach a higher terminal velocity than smaller riders, all other things being equal
Tried breaking on carbon rims and cork pads in the wet??
They're shi*e they are until they warm up and dry out, which is about 70mtrs after you want them to work..
Hahhahaha
Change the pads and feather the breaks like you used to do with the old canti's you once had on your old Marin Pine Mountains..
Hahahaha
No seriously..
Ultegra ones don't seem to have much of a problem with it
Ultegra brakes, £50 per end from wiggle.. they are on my shopping list 🙂
Don't even start to think that a set of Ultegra brakes will stop you as well as a set of BB7s - especially in the wet.
I can say with confidence I would be closer to them top to bottom than going back up again.
Don't even start to think that a set of Ultegra brakes will stop you as well as a set of BB7s - especially in the wet
Given I can endo with Ultegras in the wet, I'm really struggling to work out how BB7s could possibly stop me faster.
So slightly off thread, how is a downhill skier faster on the snow/ice than when he/she jumps a hill instead? Drag must be the same (assuming same aero tuck), no power input (i.e. wheels pushing them forwards etc.). Must have missed that lesson at school whilst behind the bike sheds with me pals.
[alert, spoiler from yesterday] Respect to Voeckler on that downhill yesterday, landing in that car park - it looked like a pretty large hop down onto the concrete!). Kiss of death mind, saying he was a great descender!!!
No direct experience, but when I went out to do the etape I was a bit nervous, having never done an alpine descent.
I need not have worried, biggest issue was traffic and making sure you don't touch a wheel. My fellow 'competitors' were almost all absolutely terrible.
If the day is warm, but not so warm the tarmac melts, it is stunning the amount of grip availible. I was just slapping the bike in and hoofing as much weight as I could on the front. Completely different to the cold, rain slicked, greasy and patchwork quilt pot holed roads in the UK. Supremely confidence insipiring.
I've never keep up with the best, but I'm pretty sure I'd keep up with the pack ... well, on the descent anyway. I completed the stage 2 hours slower than the pros ...
a skier will gain speed well in the air but in the wrong direction, basically they are falling, gaining velocity straight down. When they are on the snow the reaction force of the snow applies a force that is in part horizontal so pushing them the direction they want to go.
Watching the descent yesterday was more like watching Moto GP than a bicycle race.
You'd be surprised how a well ridden bicycle can corner compared to a motorbike too. But not too much if you've ever watched the 125s compared to the bigger bikes. Yates was one of the best descenders in the peloton and he was a keen biker too.