Building a sub 8kg bike

[Polar Bear]

Only 10%.  Very good for a first pass as such a loose set of requriements.

[Gus]

My Giant weighed 7.2 kg .
But the carbon frame including fork+ headset+ seatpost weighs 1600gram.
I was build with Ultegra groupset, Ksyrium Elite wheelset and lmore carbon parts.

I Paid £1600 for it  

Btw. the frame are for sale if you need a light frame and knows how to get it
transported from Denmark to UK cheap.

[rogerzilla]

The Orbit was around 18.5lb (8.4kg) with light tyres and no bottle cages, and the frame is made from 531C with conventional 32/26 spoked wheels and 105 kit.  The big weight savings came from the carbon fork, SLR saddle and the light tyres.

Buy pretty much any *quality* alu frame (cheap ones are heavier than 531) and fit it with a carbon fork, light saddle and decent conventional wheels and you'll be there.  If you can cope with them, downtube levers also save a fair bit.  There's no need to go for exotic components at all.

[Jacomus]

I find downtube shifters have quite an effect on that age group. In their world it's like riding a penny-farthing, or solid tyres.

Similar, but without the respect for braving the 'farthing 

[GruB]

if you own a 10kg bike already you could just loose 2kg of body weight

HA, that is what I did !!

[rogerzilla]

It's not the same though.  Don't ask me why, but 5lb off the bike is far more noticeable than even a stone off the rider.

[geraldc]

I can't bring myself to lose the creature comforts such as a triple, mudguards, and at least a kilos worth of water and bonk rations on a bike.

[GruB]

It's not the same though.  Don't ask me why, but 5lb off the bike is far more noticeable than even a stone off the rider.

I disagree Roger.  Lifting a sub 8kg bike up is of course light, but so are most bikes ( maybe not yours I agree  ) without the rider on them.  However I have noticed that my TCR is now more responsive with me being lighter.

Dropping a lot of weight must make a difference.

[Jacomus]

It's not the same though.  Don't ask me why, but 5lb off the bike is far more noticeable than even a stone off the rider.

I disagree Roger.  Lifting a sub 8kg bike up is of course light, but so are most bikes ( maybe not yours I agree  ) without the rider on them.  However I have noticed that my TCR is now more responsive with me being lighter.

Dropping a lot of weight must make a difference.

I agree with the 'zilla - making the bike lighter draws big gains in performance.

Though the rider does make a difference too.

[andygates]

While the power formula would suggest that only net weight matters, we all know that where the weight is removed affects performance and handling.  Plus, at its simplest, the lightweight stuff is higher spec.  So of course that Cayo feels nicer than my Etape!

[bikenerd]

When I'm fit and riding a lot, I can get to the point where dropping another 2kg from my body weight would be rather unhealthy.  (Sorry chaps )
I agree with the above, you notice a light bike more than a lighter you!

[mattc]

It's not the same though.  Don't ask me why, but 5lb off the bike is far more noticeable than even a stone off the rider.

If we ignore all the other variables between bikes, I can only see 2 reasons for this:

- You can't just 'drop' 5lb of flab by clicking your fingers, but you can switch bikes in seconds - you therefore associate light bikes with a tremendous increase in speed, but never notice the effects of changed bodyweight. OR

- It's the unsprung weight thing, well known to car engineers**. You don't go faster by moving 5lb from the bike to your body*, but the increase in ride quality and 'lively' handling makes for a more pleasurable experience, giving a psychological boost.

M

The footnotes:
*I'm being heretical here, suggesting we carry as much stuff on our body instead of the bike. Well, I think for pure performance, this probably works. But a heavy rucksack will still tire you out over a long ride, enough to banjax any minor handling improvements!
**Who laugh at boy-racers adding bigger tyres+wheels, as they are usually heavier, and thus often result in WORSE handling. As a Miata driver Roger, you of all people should know about this

[rogerzilla]

The heavy rider/light bike thing certainly works best offroad or on rough surfaces, where your legs become the suspension.  In fact, for "SPD hops", the higher the rider/bike weight ratio, the better, because when you bend your legs the bike is more likely to move towards you rather than you move towards it.

As far as hill climbing on a smooth road is concerned, there's some highly unscientific waffle about dynamic weight (which you hurl around as you stomp on the pedals) vs static weight (as the bike stays planted on the road) which is often used to explain it.

Another complicating factor is that losing body weight frequently involves a loss of power too (I'd never deliberately try to lose weight "in season").  So if you go on a diet and lose half a stone without also increasing training load, your TT times will probably suffer.

[hazeii]

Dropping weight off the bike feels more significant because it's a quite a large percentage of the *bike* weight - 2kg off a 10kg is 20%! So when you push on the pedals, the bike accelerates that much faster underneath the rider. Of course, the rider has to hang on - but the impression is the bike is shooting forward much quicker.

Similarly in mountain biking - it's much easier to move a light bike about under you than it is a heavy one.

[Lucky]

It's not the same though.  Don't ask me why, but 5lb off the bike is far more noticeable than even a stone off the rider.

Perhaps because the loss of weight from the bike is instantaneous, whereas loss of rider weight is a more gradual thing, happening over a period of months, so you have time to become accustomed to it?

[David Martin]

It's not the same though.  Don't ask me why, but 5lb off the bike is far more noticeable than even a stone off the rider.

Perhaps because the loss of weight from the bike is instantaneous, whereas loss of rider weight is a more gradual thing, happening over a period of months, so you have time to become accustomed to it?

You've never noticed that 'flying along' feeling when returning to the bike after a vicious bout of D&V?

..d