It Doesn't matters, It's not the bike/kit you have...

[cyberknight]

This cracked me up. Not the fact that the gains are marketing hype, but the comparison and your suggestion.

You compare a 15kg mountain bike and a 7kg road bike and suggest that “a poop” before riding cancels the difference out. Now, we are all different, but if you’re taking an 8kg “poop” then the type of bike you have is the least of your worries!

+1
my slicked mtb gotta weigh close to 20 kg with panniers etc, i have drop bars on it and can get a good aero tuck but theres no way i would take it on a club run , its a beast to keep over 18 mph and on the hills you just die if you want to keep any semblance of speed.Caught a guy on a road bike the other day on the flat and gave him a draft , soon as we hit an incline he left me for dead.

 

[DaveReading]

The weight of your bike/kit ONLY matters when you go up a hill (barely), in straights- almost 0 difference.

Provided you never have to slow down and accelerate again. If you do, Newton's Second Law applies.

 

[derrick]

This has to be the best thread of the year,

 

[SkipdiverJohn]

I think people are focusing too much on the poo aspect and are losing sight of the original point; which is that the majority of power is absorbed overcoming aerodynamic drag which is not weight-dependent, and that for a typical rider, losing quite a bit of weight off their bike is still only going to make a few percent reduction in the combined running weight of bike and rider.
In my clothes I weigh 90kg give or take, and I have a choice of Raleigh Pioneer that weighs 14kg, and an old-school Raleigh MTB that weighs 16 kg. Choosing the lighter bike of the two is going to save a whopping 2% on my total rolling weight. At low speed, power required is going to be roughly a 50/50 split between aero drag and rolling drag, therefore saving 2% on my rolling weight by saving 2kg on bike weight, but nothing on aero drag, is going to result in around a 1% reduction in propulsion power required for a given speed (assuming similar rolling resistance tyres are used).. And for fast riders on road bikes, the aerodynamic loss is going to be much greater than for a plodder like me, so the effect of reducing bike weight is going to be even less in terms of power required.
It seems to me that if people are going to worry about weight reduction, their body fat should be the first thing on the agenda, not the weight of their bike (and no financial cost either), and they should only start obsessing about silly stuff like lightweight wheelsets once they cannot get any further reduction in body fat.

 

[bpsmith]

I think that you need to factor in that you don’t ride at a constant speed on the flat for your whole ride very often. Let’s have the stats for the difference in time it takes for your 16kg MTB to get to 20mph, compared to a 7kg road bike? Let’s also have the stats for the same bikes travelling up an 8% average climb?

EDIT: Forgot to ask why losing body weight and losing bike weight are mutually exclusive?

 

[screenman]

I think people are focusing too much on the poo aspect and are losing sight of the original point; which is that the majority of power is absorbed overcoming aerodynamic drag which is not weight-dependent, and that for a typical rider, losing quite a bit of weight off their bike is still only going to make a few percent reduction in the combined running weight of bike and rider.
In my clothes I weigh 90kg give or take, and I have a choice of Raleigh Pioneer that weighs 14kg, and an old-school Raleigh MTB that weighs 16 kg. Choosing the lighter bike of the two is going to save a whopping 2% on my total rolling weight. At low speed, power required is going to be roughly a 50/50 split between aero drag and rolling drag, therefore saving 2% on my rolling weight by saving 2kg on bike weight, but nothing on aero drag, is going to result in around a 1% reduction in propulsion power required for a given speed (assuming similar rolling resistance tyres are used).. And for fast riders on road bikes, the aerodynamic loss is going to be much greater than for a plodder like me, so the effect of reducing bike weight is going to be even less in terms of power required.
It seems to me that if people are going to worry about weight reduction, their body fat should be the first thing on the agenda, not the weight of their bike (and no financial cost either), and they should only start obsessing about silly stuff like lightweight wheelsets once they cannot get any further reduction in body fat.

Why silly, it is my disposable, this sort of topic often seems to show up a green eyes monster.

What do you do with your disposable each week that is sensible.

 

[bpsmith]

Why silly, it is my disposable, this sort of topic often seems to show up a green eyes monster.

What do you do with your disposable each week that is sensible.

He spends it training on how to get the perfect torque setting without ever needing a torque wrench.

 

[bpsmith]

Based on your examples @SkipdiverJohn, using the first call that I could find, it would take an additional 36 mins for the same rider to travel 80km on a 7kg road bike compared to a 16kg MTB and that’s on the flat!

 

[delb0y]

I find stopping to take photographs, or have a look round, or a drink or a cake, has quite an effect on my speed. That must be where I'm going wrong. I suppose adopting this aero-tuck thing might mean I don't see the things that make me want to stop and have a look round anyway, so it follows an aero tuck would make me faster. Would spoil cycling massively, of course. But I'd be faster.

 

[SkipdiverJohn]

I think that you need to factor in that you don’t ride at a constant speed on the flat for your whole ride very often. Let’s have the stats for the difference in time it takes for your 16kg MTB to get to 20mph, compared to a 7kg road bike? Let’s also have the stats for the same bikes travelling up an 8% average climb?

EDIT: Forgot to ask why losing body weight and losing bike weight are mutually exclusive?

OK, so if I was to ride a 7kg road bike I would have a rolling weight of 97kg as opposed to 106kg on the MTB. That's 8% of the total, which would give some increase in acceleration, although it would not be anything like 8% faster as aerodynamics would be constant. Climbing a gradient would be harder/slower, no arguments. However a heavier bike/rider combination also has more momentum once up to speed so do not lose speed so quickly once you stop pedalling. You might have a hard slog up a hill, but once over the crest you can bomb down the other side. What you lose going up you gain going down, so long as you can take advantage of it without braking.
Losing body weight and bike weight are not mutually exclusive. However losing body weight is totally free whereas losing bike weight can get very expensive, once it gets to obsessional levels involving mere ounces rather than pounds.

 

[bpsmith]

I find stopping to take photographs, or have a look round, or a drink or a cake, has quite an effect on my speed. That must be where I'm going wrong. I suppose adopting this aero-tuck thing might mean I don't see the things that make me want to stop and have a look round anyway, so it follows an aero tuck would make me faster. Would spoil cycling massively, of course. But I'd be faster.

You’re right, of course, if that’s what you enjoy out of cycling. You’re also not trying to suggest that not doing those things won’t make you any faster.

 

[screenman]

I find stopping to take photographs, or have a look round, or a drink or a cake, has quite an effect on my speed. That must be where I'm going wrong. I suppose adopting this aero-tuck thing might mean I don't see the things that make me want to stop and have a look round anyway, so it follows an aero tuck would make me faster. Would spoil cycling massively, of course. But I'd be faster.

I have never wanted to stop whilst out on the bike.

 

[SkipdiverJohn]

Based on your examples @SkipdiverJohn, using the first call that I could find, it would take an additional 36 mins for the same rider to travel 80km on a 7kg road bike compared to a 16kg MTB and that’s on the flat!

You're not comparing like with like though. You're assuming knobbly tyres on the MTB and an upright riding position vs slick tyres on the road bike and an aero riding position. I was only talking about the difference in weight Try running the numbers again for an upright position on both bikes and at least commuter type tyres on the MTB, which is what most riders would use for longer journeys. No-one is going to use knobblys on a 50 mile ride.

 

[bpsmith]

OK, so if I was to ride a 7kg road bike I would have a rolling weight of 97kg as opposed to 106kg on the MTB. That's 8% of the total, which would give some increase in acceleration, although it would not be anything like 8% faster as aerodynamics would be constant. Climbing a gradient would be harder/slower, no arguments. However a heavier bike/rider combination also has more momentum once up to speed so do not lose speed so quickly once you stop pedalling. You might have a hard slog up a hill, but once over the crest you can bomb down the other side. What you lose going up you gain going down, so long as you can take advantage of it without braking.
Losing body weight and bike weight are not mutually exclusive. However losing body weight is totally free whereas losing bike weight can get very expensive, once it gets to obsessional levels involving mere ounces rather than pounds.

You’re missing the fact that your MTB has knobbly MTB tyres and not smooth road tyres. There’s a serious loss straight away. You’re also missing that you’re more aerodynamic with narrower drop bars compared to wider flat upright bars. There’s also the geometry of the frame to consider. It’s clearly not totally down to weight with the examples given.

What about the difference between snug fitting road gear compared to flappy baggy MTB clothing too? (This ones a joke btw )

With regards to being able to make up the lost time from climbing, when descending the other side, I think we all know that’s not possible. A significant amount more time is lost in climbing than can be gained when descending.

With regards to losing weight being free, I beg to differ. Yes, it’s physically possible to just stop eating in order to lose weight, but keeping your fitness and muscle power intact when losing weight requires quality food with the perfect balance of what your body needs. That actually doesn’t come cheap. If you’re 175cm tall and 70kg, it’s tough to lose the 9kg difference and still ride fast.

 

[screenman]

You're not comparing like with like though. You're assuming knobbly tyres on the MTB and an upright riding position vs slick tyres on the road bike and an aero riding position. I was only talking about the difference in weight Try running the numbers again for an upright position on both bikes and at least commuter type tyres on the MTB, which is what most riders would use for longer journeys. No-one is going to use knobblys on a 50 mile ride.

I have done 100 + on knobblies. So has my son and I would imagine his wife as well. Thinking about it I know of loads of cyclist who have done the same.