Who wants to do 50mph?

mrushton

60mph down the Woodhead descent to the roundabout. I was on 53x12 prob. with a tailwind. I backed off because at that speed if it goes wrong the outcome won't be good. Any trip to the Alps/Pyreness should easily see you reach 50mph+. especially on descents from eg the Iseran/Izoard etc

briantrumpet

simpoman wrote:

Must be SW thing.....mine was down from Merrivale to Tavistock

That, and the next one (Pork Hill) are the exact ones where I've wimped out and kept dabbing the brakes. My therapist says I shouldn't get too exited...

BarryBonds

63 tourmalet no helmet so i wouldnt have felt a thing

SBezza

Fastest I have been is 51.1 mph, that was on the TT bike on the tri bars as well. Luckily the brakes work well, as there was a RAB at the bottom which I had to turn at and go back up the hill. Not in the SW though

Personally I think coming off at 40 mph or 50mph + the outcome isn't going to be much different, you are going to have a shedload of gravel rash whatever.

petemadoc

TommyEss wrote:

56mph on a 50x12 - but I'm hefty.

I was pretty good a physics at school but I still can't figure this one out. How does weight affect your speed on descents?

My top speed so far is 51mph

Ollieda

To be fair, a lot of people talking about bike setups and so on, doesnt really matter in comparison to body weight and road. Theres a hill near my where i can touch 50 simply from getting into a tuck posistion on the way down, no need to peddle and my bike is only an entry level cost.

I could easily push faster if I peddled and fully committed from the top but the first bit is a bit of a blind bend so i'm normally a bit hesitant and on the brakes for that bit. It's the part where saftey clashes with fun for me and saftey wins there

bompington

PeteMadoc wrote:

I was pretty good a physics at school but I still can't figure this one out. How does weight affect your speed on descents?

You reach your terminal velocity (maximum speed) when the force pushing you downhill (gravity possibly + pedalling) matches the resistance (mainly wind resistance, rolling resistance from tyres & internal resistance from hubs are much smaller at high speeds).

If you are heavier, there is more force from gravity, but the difference in wind resistance is much smaller. This also applies when pedalling on the flat or downhill (uphill is a different matter) - heavier riders are likely to be more powerful but the wind resistance is not noticeably different.

I've seen this in action quite a lot - out with fitter, faster riders on better bikes, I find that I can easily beat them dowhill, sometimes without pedalling. This is on a 15 year old Raleigh that is subject to the most negligent servicing regime north of the border.

My PB is 57mph* down a fairly hairy hill between Dundee and Perth, it requires a tailwind, pedalling furiously down the first stretch and round a bend at about 40, then tuck & pray for the rest - followed by a dead stop for the junction at the bottom. This particular road surface has been deteriorating steadily and I haven't managed over 50 in a couple of years.

*That's the truth, but you only have my word on it don't you?

pst88

I regularly do 70mph.... driving to the start of a sportive. Oh you mean on a bike? Probably no more than 35mph cos I get scared.

Fodder666

I've managed 40.66mph downhill and 28mph on the flat all on a mountain bike with full tread tires

freehub

Stuy-b wrote:

micken wrote:

Stuy-b wrote:

52.96mph is my fastest so far this year, there was a big cross wind so lost my nerve at 52.96, and was on the training bike. i think i can hit 58ish on a good day on that road

Where's that road?

dropping down to the goyt vally from the top of long hill.

I've heard someone did well over 60 on that road.


The fastest I've done is 52.8.

Gazzaputt

48 and no way would I do that ever again.

It bloody hurts when you come off plus the bike gets trashed. I have kids, wife and a mortgage. I need to work so even better reasons not to take unnecessary risks.

These days I stick to a speed I'm comfortable with which at most is 38mph.

BarryBonds

a light is being shed here

GeorgeShaw

49 on the decent into Machynlleth on the Trans-Cambrian sportive, close to that on the north descent of the Rhigos. The former was hairy, the latter is safe enough.

benno68

I've done 50mph on a 50x12 on Caerphilly Mountain dropping down into Thornhill. There's a bit of a nasty bend and not the best road surface so I must admit that a certain part of my anatomy twitched a bit.

I could do with an 11t but at my as I'm 42 and 13.5stone, I still need the insurance of a 27t.

Cressers

46mph down a welsh tarmac road, and in the Forest of Dean. In both cases I was concerned about the sheep that lay in wait on the road...

snailracer

bompington wrote:

PeteMadoc wrote:

I was pretty good a physics at school but I still can't figure this one out. How does weight affect your speed on descents?

You reach your terminal velocity (maximum speed) when the force pushing you downhill (gravity possibly + pedalling) matches the resistance (mainly wind resistance, rolling resistance from tyres & internal resistance from hubs are much smaller at high speeds).

If you are heavier, there is more force from gravity, but the difference in wind resistance is much smaller. This also applies when pedalling on the flat or downhill (uphill is a different matter) - heavier riders are likely to be more powerful but the wind resistance is not noticeably different.

I've seen this in action quite a lot - out with fitter, faster riders on better bikes, I find that I can easily beat them dowhill, sometimes without pedalling. This is on a 15 year old Raleigh that is subject to the most negligent servicing regime north of the border.

My PB is 57mph* down a fairly hairy hill between Dundee and Perth, it requires a tailwind, pedalling furiously down the first stretch and round a bend at about 40, then tuck & pray for the rest - followed by a dead stop for the junction at the bottom. This particular road surface has been deteriorating steadily and I haven't managed over 50 in a couple of years.

*That's the truth, but you only have my word on it don't you?

In theory, a heavy rider, say twice as heavy as a lighter rider, will have twice the gravitational force (i.e. 100% more) acting to pulling him downhill, but only 59% more aerodynamic drag slowing him down. So, all things being equal, a bigger rider should coast faster downhill than a lighter rider. It's all down to the geometric ratio of volume to area for identical shapes.

bigmat

Done 50+ a few times, but only just - 51 max I think. Would need a nice long straight as I don't like going into bends I don't know at that kind of speed. 30+ on the flat, 40+ on most poper descents. I imagine it would hurt coming off at any speed over 20 to be honest, when you get significantly faster you're in the lap of the gods as to whether it hurts, maims or kills. I therefore make sure that if I'm pushing it, I can be sure as I can be that I won't be crashing (subject to freak mechanicals etc.)

steelcat

50 isnt all that difficult. I have done that coming down parbold hill. there are a few short sharp hill around here where you can get to 50. Its the keeping it up that is the hard bit

Drysuitdiver

snailracer wrote:

bompington wrote:

PeteMadoc wrote:

I was pretty good a physics at school but I still can't figure this one out. How does weight affect your speed on descents?

You reach your terminal velocity (maximum speed) when the force pushing you downhill (gravity possibly + pedalling) matches the resistance (mainly wind resistance, rolling resistance from tyres & internal resistance from hubs are much smaller at high speeds).

If you are heavier, there is more force from gravity, but the difference in wind resistance is much smaller. This also applies when pedalling on the flat or downhill (uphill is a different matter) - heavier riders are likely to be more powerful but the wind resistance is not noticeably different.

I've seen this in action quite a lot - out with fitter, faster riders on better bikes, I find that I can easily beat them dowhill, sometimes without pedalling. This is on a 15 year old Raleigh that is subject to the most negligent servicing regime north of the border.

My PB is 57mph* down a fairly hairy hill between Dundee and Perth, it requires a tailwind, pedalling furiously down the first stretch and round a bend at about 40, then tuck & pray for the rest - followed by a dead stop for the junction at the bottom. This particular road surface has been deteriorating steadily and I haven't managed over 50 in a couple of years.

*That's the truth, but you only have my word on it don't you?

In theory, a heavy rider, say twice as heavy as a lighter rider, will have twice the gravitational force (i.e. 100% more) acting to pulling him downhill, but only 59% more aerodynamic drag slowing him down. So, all things being equal, a bigger rider should coast faster downhill than a lighter rider. It's all down to the geometric ratio of volume to area for identical shapes.

galileo proved things many years ago a 50kg weight and a 100kg weight released at the same time from the same height will hit the ground at the same time- they fall at the same rate.

the 100kg will exert a greater force on the ground when it lands than the 50Kg weight but regardless of weight of an object they will still fall at the same rate 9.8m/s sq

Feltup

53mph down Kirkstone on the Fred Whitton
51mph down Streatley Hill in the dark was scarier though!
I regularly do mid 40's on most of my hilly rides. I try not to think about coming off, so far 35mph is my fastest off and I left a lot of skin on the road, not a great way to end your honeymoon :oops:

rick_chasey

Fasted I did was in the Pyrenees - 70kph.

morstar

Drysuitdiver wrote:

snailracer wrote:

bompington wrote:

PeteMadoc wrote:

I was pretty good a physics at school but I still can't figure this one out. How does weight affect your speed on descents?

You reach your terminal velocity (maximum speed) when the force pushing you downhill (gravity possibly + pedalling) matches the resistance (mainly wind resistance, rolling resistance from tyres & internal resistance from hubs are much smaller at high speeds).

If you are heavier, there is more force from gravity, but the difference in wind resistance is much smaller. This also applies when pedalling on the flat or downhill (uphill is a different matter) - heavier riders are likely to be more powerful but the wind resistance is not noticeably different.

I've seen this in action quite a lot - out with fitter, faster riders on better bikes, I find that I can easily beat them dowhill, sometimes without pedalling. This is on a 15 year old Raleigh that is subject to the most negligent servicing regime north of the border.

My PB is 57mph* down a fairly hairy hill between Dundee and Perth, it requires a tailwind, pedalling furiously down the first stretch and round a bend at about 40, then tuck & pray for the rest - followed by a dead stop for the junction at the bottom. This particular road surface has been deteriorating steadily and I haven't managed over 50 in a couple of years.

*That's the truth, but you only have my word on it don't you?

In theory, a heavy rider, say twice as heavy as a lighter rider, will have twice the gravitational force (i.e. 100% more) acting to pulling him downhill, but only 59% more aerodynamic drag slowing him down. So, all things being equal, a bigger rider should coast faster downhill than a lighter rider. It's all down to the geometric ratio of volume to area for identical shapes.

galileo proved things many years ago a 50kg weight and a 100kg weight released at the same time from the same height will hit the ground at the same time- they fall at the same rate.

the 100kg will exert a greater force on the ground when it lands than the 50Kg weight but regardless of weight of an object they will still fall at the same rate 9.8m/s sq

In terms of the effect of gravity, yes you are correct. Air resistance is a signicant factor for our cyclist though.

extreme example: What falls faster, a ton of feathers or a ton of bricks?
Same mass, different rate of falling.
Pack the feathers into a box, similar rate of fall to the bricks.

A skinny lightweight cyclist will be more affected by the wind than a heavier one, subject to build and position etc etc.

rick_chasey

Drysuitdiver wrote:

galileo proved things many years ago a 50kg weight and a 100kg weight released at the same time from the same height will hit the ground at the same time- they fall at the same rate.

the 100kg will exert a greater force on the ground when it lands than the 50Kg weight but regardless of weight of an object they will still fall at the same rate 9.8m/s sq

Yeah, but that's not including air-resistnace.

Given that air-resistance is a big deal on the bike, you need to consider that.

On Earth in normal air, a heavier ball for the same shape will fall quicker...

Sure on the moon everything falls at the same speed, but we're not on the moon!

markos1963

46 mph in Norfolk!!!

micken

I regularly freewheel past my wife and other smaller cyclists on descents. In real world physics it's the air resistance vs mass as others have said.

eskimo Joe

54mph coming down the cairn o'mount, but only hit 49mph coming down it last week,

Blacktemplar

The road from Dalwhinnie to Laggan is good for that too

+1

Lovely bit of road that.

My fastestest ever was down Glen Sannox on Arran, clocked 45.2 mph. Was tailgating a Dutch tourist and the look on his face in the rearview mirror was comical. I don't know the Dutch* for "what the f*ck is that idiot on the bike doing?" but that looked like what he was mouthing to his wife..... :twisted:

Seriously though, when I think about it now it gives me the heebie-jeebies. The road surface at the bottom as you cross the bridge is appalling, and it was all I could do to hang on as I hit it at 35+

It was a monumentally stupid thing to do - newbie mistake, I'd only had the bike a month or so and was a far from experienced rider. If I'd come off at that point I'd probably have been killed. You'd think at my age I'd know better...... :roll:

Still haven't told the wife - cold get me a red card.....






* "wat in gotsnaam is die idioot op de fiets te doen" (according to Google Language Tools) but that's probably bollocks. Or "kloten" as they say in Amsterdam.

El Gordo

52mph on a tandem with front and rear panniers plus a Bob trailer and slightly scared but duitfully quiet wife on the back seat.

53mph on a road bike, but I've given that game up after a speed wobble put me into the armco at 40mph+ . I can confirm that it is not a nice experience.

petemadoc

Rick Chasey wrote:

Drysuitdiver wrote:

galileo proved things many years ago a 50kg weight and a 100kg weight released at the same time from the same height will hit the ground at the same time- they fall at the same rate.

the 100kg will exert a greater force on the ground when it lands than the 50Kg weight but regardless of weight of an object they will still fall at the same rate 9.8m/s sq

Yeah, but that's not including air-resistnace.

Given that air-resistance is a big deal on the bike, you need to consider that.

On Earth in normal air, a heavier ball for the same shape will fall quicker...

Sure on the moon everything falls at the same speed, but we're not on the moon!

Right I'm getting confused here.

Let's make this as simple as possible. I have two balls exactly the same shape and size but one weighs 1Kg and the other weighs 2Kg

I drop both them at the same time from the same height. I know that in a vacume they will hit the ground at the same time. How does that change when air is present. They're the same size and shape so isn't air resistance the same for both balls?

Velonutter

Mid 70's and a mate and I were riding a tandem going full belt down from Epsom downs to the town centre, copper in one of those horrible blue Allegros stops us at the bottom and tells us that he clocked us at 63mph :shock: As he was on his own he couldn't do us but told us to be careful in future,

Might be something to do with my mate being 6ft 4" and built like a brick sh!t house.