Maximum Speed
- Thread starter dav1d
- Start date
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MacB
Lover of things that come in 3's
- Location
- Farnborough, Hampshire
marinyork said:
I'm feeling love, in a manly way of course, first ever person to mention me, and quick, in one sentence!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
needed a super Keith! to celebrate that one
You're always near the top of cyclogs. I can understand you using a hybrid for a commute, but that sort of speed on a commute isn't bad. I thought you would be on a racing bike (and rapidly getting quicker). You'll be the new BFTB before long.
grhm
Veteran
- Location
- Malvern, Worcestershire
dav1d said:
I think "full sus" refers to having front and rear suspension. Often you'll just get front suspension forks (i.e. a "hardtail" bike).
Bodhbh
Guru
On the road on a tourer most I've done is just over 35mph, which is when I run out of gears and the panniers start acting like a parachute. It seems almost a 'hard cap', although maybe I've just not found a steep enuff hill. On the MTB I've hit 35mph downhill on smooth grassy sections of the South Downs Way, which was pretty hairy for me at least, with the odd rabbit hole and whatnot. Not sure I'd have the balls to get past 40 anywhere even if I was on a bike that was capable of it.
Chris James
Über Member
- Location
- Huddersfield
bonj said:
Surely your terminal velocity is determined by the wind resistance at high speed? In which case I would have expected you to have a faster top speed on a road bike as you would (probably) have a more aerodynamic position?
I am not sure what my top speed was. I know I have been well in the 40s mph but not up to 50, although once I get above about 38 mph I start to dwell on my mortality unless the road is smooth and empty!
Randochap
Senior hunter
- Location
- British Columbia, Canada
I've hit a maximum of 85 km/h (53 mph), on my Ciclo down a long, steep hill. That was fun, until the corner came up ... then it was a different kind of fun.
The fastest I ever went on a MTB (my Rocky Mountain Blizzard) was on a steep descent of a rutted, washed-out logging road on Central Vancouver Island -- 72 km/h (45 mph) I made the decent of that section in fine form, but when I hit the graded gravel public road and approached 70 km/h, I got sucked into some big rubble on an inside corner and (according to my ride mates) did the most spectacular "endo" never recorded on videotape! Luckily I survived with only a bruised palm and pride.
As for average speed, that depends on so many factors it is useless to quote. On a good day, on the road, on my light bike, without significant headwinds, on a relatively "flat" course (there are no flat routes here), let's say my "average" average is 26 km/hr. On a "best" day, it's 30 km/h
The fastest I ever went on a MTB (my Rocky Mountain Blizzard) was on a steep descent of a rutted, washed-out logging road on Central Vancouver Island -- 72 km/h (45 mph) I made the decent of that section in fine form, but when I hit the graded gravel public road and approached 70 km/h, I got sucked into some big rubble on an inside corner and (according to my ride mates) did the most spectacular "endo" never recorded on videotape! Luckily I survived with only a bruised palm and pride.
As for average speed, that depends on so many factors it is useless to quote. On a good day, on the road, on my light bike, without significant headwinds, on a relatively "flat" course (there are no flat routes here), let's say my "average" average is 26 km/hr. On a "best" day, it's 30 km/h
Chris James said:
normally, yes, but when i was going 42mph on the mtb I was more aerodynamic than i would normally be on the MTB since I was ducking my head right down so my nose was literally right behind the stem. An un-ergonomic position to pedal, but pedalling was pointless as with a top gear of 42x12 i was spinning out way below that speed.
Advantage of a road bike is you can maintain an aerodynamic position *while pedalling* (and in slightly more comfort).
As a side, you might be surprised what difference flappy vs. close-fitting clothing makes to rolling resistance even at low speed.
To put the record straight.
There are three forces acting on a rolling vehicle which impede its motion.
1/ Rolling resistance of the tyres. - Energy to deform the rubber and absorb heat due friction with the roadsurface.
2/ Aerodynamic Drag. - The energy it takes to move the volume of air the vehicle intends to occupy and the reduction in pressure following the vehicle causing a rearward movement.
3/ Gravity. - The mass of the vehicle and the position of its 'centre of gravity' relative to its 'plan centre'. ie Angle of inclination.
All downhill velocities will be assisted by 3/, therefore elliminated from any 'speed boasting'.
Smooth clothing and 'tuck' positioning are an assistance, but valid for 'speed boasting'.
2/ is non - linear. The faster the velocity, the greater the force, and therefore the greater power is required to increase velocity. It requires more power to increase from 28 to 30 mph than it does to increase from 8 to 10 mph.
1/ is linear. If 10 Newtons are required at 10 mph, 20 N will be required at 20 mph and 30 N required at 30 mph. ( Do not take these figures at reality. They are merely to serve as an example )
I don't deal in Newtons. There is an equation to directly calculate HorsePower from Coefficient of Rolling Resistance and Coefficient of Drag.
Pf = ( Crr x (W/375) x V ) + ( CdA x (V^2/391) * (V/375) )
This is the 'Holy grail'
There are three forces acting on a rolling vehicle which impede its motion.
1/ Rolling resistance of the tyres. - Energy to deform the rubber and absorb heat due friction with the roadsurface.
2/ Aerodynamic Drag. - The energy it takes to move the volume of air the vehicle intends to occupy and the reduction in pressure following the vehicle causing a rearward movement.
3/ Gravity. - The mass of the vehicle and the position of its 'centre of gravity' relative to its 'plan centre'. ie Angle of inclination.
All downhill velocities will be assisted by 3/, therefore elliminated from any 'speed boasting'.
Smooth clothing and 'tuck' positioning are an assistance, but valid for 'speed boasting'.
2/ is non - linear. The faster the velocity, the greater the force, and therefore the greater power is required to increase velocity. It requires more power to increase from 28 to 30 mph than it does to increase from 8 to 10 mph.
1/ is linear. If 10 Newtons are required at 10 mph, 20 N will be required at 20 mph and 30 N required at 30 mph. ( Do not take these figures at reality. They are merely to serve as an example )
I don't deal in Newtons. There is an equation to directly calculate HorsePower from Coefficient of Rolling Resistance and Coefficient of Drag.
Pf = ( Crr x (W/375) x V ) + ( CdA x (V^2/391) * (V/375) )
This is the 'Holy grail'
MacB
Lover of things that come in 3's
- Location
- Farnborough, Hampshire
I feel unworthy again
...And I thought I was going fast when I got to 50km/h going down a steep hill.
I haven't tried to beat it, since a pedestrian stepped out in front of me (and a car) at the bottom of that hill, and almost got hit by both.
I'll try and top that speed somewhere outside London ;-).
I haven't tried to beat it, since a pedestrian stepped out in front of me (and a car) at the bottom of that hill, and almost got hit by both.
I'll try and top that speed somewhere outside London ;-).
Cubist
Still wavin'
- Location
- Ovver 'thill
Hadn't really thought about downhill speeds off road, so took the computer with me to Dalby on Sunday. The last 5 miles of the Blue route is virtually all downhill, and maxed out at 27 mph. Just occasionally visions of your own mortality kick in when you realise you've got to jump a rain gully and there's only gravel on mud in the landing zone. Didn't need the ex-lax that afternoon.......
