Maximum speed for a mountain bike

nicklouse

130Mph.

http://www.flixxy.com/mountain-bike-wor ... record.htm

bennett_346

supersonic wrote:

A 'nondescript person' who's power output will not change compared to the road bike. This is a constant here. The gearing and drag are variables. We need to look at the variable, which is the bike, as in the question.

Clearly we both have a scientific mind and the argument here is just about limitations so lets drop it.

supersonic

Discussion, not argument ;-)

bennett_346

You'll have to try harder than that

cooldad

No it doesn't because awesome as you actually think you are, you are not a TdeF rider.

Lagrange

Boring analysis warning...


Theoretically the person will use the same energy - E cycling either type of bike.
Speed =sqrt(2*E/M). M is the mass of rider plus bike. The heavier bike will go slower anyway even ignoring friction.

Friction is affected by Speed **2 and surface area and coefft of friction of the clothing (which can in this gedanken) - a constant. Effect of tyres is anomalous - friction should be independent of area - but never is - look at F1 Tyres. Road racing bike tyres are as they are to give absolute minimum contact area to minimise surface area and rolling friction. So the next main effect is tyre area and air friction caused by the top of the tyre moving at road speed plus angular velocity which is a major effect given the width and profile of the tread and would far exceed the differential due to weight.

mrmonkfinger

http://bikecalculator.com/examples.html

400W and 65kg rider and 9kg bike and 'drops' and 'tubulars' = 45kph or just under 30mph
400W and 65kg rider and 12kg bike and 'bartops' and 'mtb tyres' = 37kph or 23mph

Although what sort of tyres with what kind of resistance that calculogizmo puts "mtb tyres" at, well, it doesn't say. 400W is fairly close to what a Tour rider will put out over a sustained climb, so half hour or forty minutes up the galibier, or whatever.

Incidentally a TDF sprint finish requires about 1500W, anyone here think they could manage that after a 4 hour ride?

andyg1966

Following on from this, how fast have you gone recorded on a cycle computer or GPS.

My maximum is 47mph down the grass slope of Butser hill at QECP pedalling for all I was worth with 44/11 gearing.

mrmonkfinger

andyg1966 wrote:

Following on from this, how fast have you gone recorded on a cycle computer or GPS.

My maximum is 47mph down the grass slope of Butser hill at QECP pedalling for all I was worth with 44/11 gearing.

52mph before shitting myself and braking, somewhere in South Lanzarote, down about a mile of 10% gradient, with a tailwind. There's a lot of wind in Lanzarote, so that wasn't hard to achieve.

craigw99

i did faster once down a very long fire road but i have been accused of willy waging :oops: so will not say again.. spun out a 48 11 ratio though

njee20

Incidentally a TDF sprint finish requires about 1500W, anyone here think they could manage that after a 4 hour ride?

I can do about 1200 if I really want to!

Seems mental that calculation has different metrics for clinchers/tubs, which will make a small difference, but nothing for deep section wheels - difference between some 80mm deeps vs some 20mm climbing wheels will be quite marked on the flat.

I've done 50mph on an MTB on the road a few times, nowt like that off road though.

mrmonkfinger

njee20 wrote:

Seems mental that calculation has different metrics for clinchers/tubs, which will make a small difference, but nothing for deep section wheels - difference between some 80mm deeps vs some 20mm climbing wheels will be quite marked on the flat.

I know.

Unrelated point, but it predicts my 10 mile TT result to within a few seconds (or a few W's).

cooldad

cyd190468 wrote:

cooldad wrote:

No it doesn't because awesome as you actually think you are, you are not a TdeF rider.

Correct but I am the same basic shape so the increase in power output from a TDF rider should affect the three times relatively. Just get a time from a 15km TT and calculate the rest.

So is an Orangutan