Yet Another Cycling Forum

General Category => The Knowledge => Further and Faster => Topic started by: Bolt on June 05, 2017, 11:13:34 pm

Title: Ideal bike weight as a percentage of body weight?
Post by: Bolt on June 05, 2017, 11:13:34 pm
As a tall and lean but relatively heavy rider of 185lbs I was wondering if there is any wisdom, perceived or proven, on the ideal percentage weight of a bike with respect to that of the rider? 
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: sojournermike on June 05, 2017, 11:17:21 pm
Perceived wisdom is lower is better. At 178lbs a 16lb bike feels different to a 19.4lb bike, but not sure the weight actually makes any real speed difference. Riding position does however.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Bolt on June 05, 2017, 11:42:57 pm
Perceived wisdom is lower is better. At 178lbs a 16lb bike feels different to a 19.4lb bike, but not sure the weight actually makes any real speed difference. Riding position does however.
Thanks, that's reassuring in that my position is good but less so in that my all up bike weight is ~36lbs :o
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: T42 on June 06, 2017, 10:13:13 am
Total weight matters - take it ad absurdum and imagine pedalling a 100 kg bike up a 20% hill. But it's more the strength of the bike that matters. The rider-weight limit for my carbon bike is 100 kilos, which is something like 220 lb.

From the weight, I'd guess that your current bike would be a steel tourer or MTB. You'd probably be fine on a carbon butterfly weighing half as much.

There is a rule of thumb re rider weight vs tyre pressure, which goes pressure in bars = 1/10 rider weight in kilos, to the limit of the manufacturer's spec.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: mrcharly-YHT on June 06, 2017, 10:22:53 am
There is a rule of thumb re rider weight vs tyre pressure, which goes pressure in bars = 1/10 rider weight in kilos, to the limit of the manufacturer's spec.
15% deflection is a much better rule of thumb, if a tad difficult to measure.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: citoyen on June 06, 2017, 10:58:50 am
Based on the 6.8kg lower bike weight limit for pro racers, and the reported weights of riders:

For Dumoulin (71kg) the bike is a bit over 9% of overall weight.
For Quintana (58kg), it's under 11%.

How much of a difference does that make? Is Quintana unfairly penalised by the UCI bike weight limit? Or does that actually work in his favour?
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: asterix on July 07, 2017, 07:33:50 am
 
Perceived wisdom is lower is better. At 178lbs a 16lb bike feels different to a 19.4lb bike, but not sure the weight actually makes any real speed difference. Riding position does however.
Thanks, that's reassuring in that my position is good but less so in that my all up bike weight is ~36lbs :o

That's some bike. My Dutch (Gazelle Impala) upright was 39lbs

(http://www.stegink-bike.nl/admin/images/lar_4893DSCN1223.JPG)

I used it to commute through York (flat) - it was good training especially with a strong headwind.


Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Cudzoziemiec on July 07, 2017, 09:53:23 am
What advantages derive from greater bike weight as opposed to greater stiffness, strength? I can't think of any, apart from training.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: lahoski on July 07, 2017, 10:02:08 am
Perceived wisdom is lower is better. At 178lbs a 16lb bike feels different to a 19.4lb bike, but not sure the weight actually makes any real speed difference. Riding position does however.

My bike weight as a percentage of body weight is reducing at an all too alarming rate.

 :'(

What advantages derive from greater bike weight as opposed to greater stiffness, strength? I can't think of any, apart from training.

Momentum? I think the benefits come more for utility cycling... I find a heavier bike much more pleasant in windy conditions - lighter bikes (even with similar geometry) always feel a bit skittish.

As long as the distances are relatively small and there are no bastard hills, heavy bikes can be quite pleasing.

I'm not sure for 'proper' cycling there are any particular advantages beyond stiffness, strength, durability and training.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Cudzoziemiec on July 07, 2017, 10:11:32 am
Stability in wind is a good point. I'm not sure about momentum, as inevitably you never gain quite as much on the downhill as you lose on the uphill.

I'm not sure for 'proper' cycling there are any particular advantages beyond stiffness, strength, durability and training.
I'm trying to isolate stiffness, strength, durability from weight. They depend on materials and construction too. So if you have two bikes of identical stiffness etc but one weighs say 9kg and the other 14.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: jsabine on July 07, 2017, 11:24:58 am
What advantages derive from greater bike weight as opposed to greater stiffness, strength? I can't think of any, apart from training.

Lower cost?
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Samuel D on July 07, 2017, 10:29:38 pm
Based on the 6.8kg lower bike weight limit for pro racers

Most bicycles in the pro peloton are well over the UCI weight limit (here’s an 8 kg example before adding computers, transponders, etc. (https://www.youtube.com/watch?v=8pzM2GkSo9I&feature=youtu.be&t=169)). That’s because grams that avocational riders obsess over do not matter even to pro racers.

If you do the calculations, even rotational mass at the periphery of the wheel (that counts double during accelerations) makes a typically trivial difference. The energies involved are negligible compared to a typical cyclist’s power. Nonetheless, people convince themselves that ‘light’ wheels, that weigh maybe 200 g less than ‘heavy’ wheels, are nothing less than transformative. I think this happens because there is a noticeable difference in inertia when the handlebars are quickly rotated through a large arc at walking speeds. In this unconscious test, the lighter wheel feels more nimble, responsive, agile, quick, etc. – all those words that bicycle reviewers use when they should be saying something important.

The magic of the wheel is that it takes the work out of carrying weight.

I don’t think a bicycle should weigh some proportion of its owner’s weight. Rather, it should be built for its intended purpose. If that is a lifetime of being thrown around bike racks and left outdoors in the rain with maintenance every decade whether needed or not, you end up with Dutch-bike weights. If it’s one season of racing, you end up with something pretty light.

But even if you’re racing, a comfortable saddle will probably make more difference than saving 100 g. And 400 g pedals with ball bearings are certainly faster over most courses than ultra-light pedals with plain bearings, despite the latter (plastic bushings) being the default choice on road bikes these days.

When I chose a set of components for a long life of solo rides, enjoyable blasts in fast groups, and a bit of practical transport, I ended up with something around 10 kg. For me, that’s a benchmark of sorts. Much below 10 kg leads to compromises I’m unwilling to make, and even the lightest machines are not usefully faster. Much above 10 kg gains me little in function and makes carrying the bicycle up the five flights of stairs to my flat needlessly hard work.

Some interesting weights are quoted here (https://janheine.wordpress.com/2017/07/05/concours-de-machines-results/).
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Bolt on July 08, 2017, 12:18:14 am
Samuel, thanks for these wise words that help articulate the relationship between between weight, function, reliability and speed.  Since my original post I felt compelled to reduce the weight of my bike following during a 5 day tour in preparation for LEL where every other rider told me I was mad for riding such a heavy bike, even though I was able to complete every climb and finish each day's ride in comfort when others riding modern lightweight road bikes were not.  The "unconscious" improvements following the 1.2kg weight reduction are exactly as you describe whereas the coincidental improvements that have been made through the use of better pedals, forks, tyres and riding position are measurably significant at the expense of a small amount of comfort.  The only thing left to consider now having watched the video you linked on Marcel Kittel's bike is whether to swap out my 31.8 seatpost for a 27.2 , is the difference in comfort really noticeable?
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Samuel D on July 08, 2017, 09:34:12 am
Differences in seatposts have not made any difference in comfort to me, although I only weigh 66 kg. I’ve tried narrow and fat, carbon and aluminium, all with no perceptible difference (different forks or cranks, on the other hand, have made a clear difference). Anyway, how can you change the seatpost diameter without buying a new frame?

Cyclists believe extraordinary things about bicycle weight. Like you, I’ve been told I’m hampering myself by riding a heavy bicycle – except in my case, mine was about 10 kg and theirs was about 8 kg! (But theirs were carbon, with all the alleged magical properties of that material.) This was shortly before a long climb out of a café where I put in an effort to make a point, dropping three-quarters of the commentators, all of whom were racers.

For steep climbs, the maths is simple: speed equals power divided by all-up weight. In your case, the all-up weight was around 220 lb. Therefore each pound lost (around that weight) produces a speed increase of less than half of one percent. It doesn’t matter where the pound is lost from: belly, frame, or wheel rim. On most hills, where aerodynamic drag and rolling resistance still play a role, the difference is even less than that. And on the flat, the difference is for all practical purposes exactly nil.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: The French Tandem on July 08, 2017, 09:50:41 am
What advantages derive from greater bike weight as opposed to greater stiffness, strength? I can't think of any, apart from training.

Greater momentum == easier to keep a constant speed on the flat ?  I'm just trying to guess something, without the slightest bit of a scientific evidence!
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Bolt on July 08, 2017, 08:14:14 pm
Anyway, how can you change the seatpost diameter without buying a new frame?
I've actually shimmed in a 27.2 seatpost previously when I've been trying out different saddles but never considered that it might introduce a bit more comfort, I certainly didn't notice any difference.  Having got my saddle set up perfectly now I'm reluctant to swap the seatpost especially as  saddle comfort is extremely good.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: asterix on July 08, 2017, 08:34:34 pm
I'd no qualms about doing the Raid Pyrennean on a 23lb steel bike with saddle bag and mudguards. 

They laughed at my set up but at least the mudguards meant I was able to descend the Tourmalet in a freezing torrential downpour when the others were walking.  Apparently there was no hot water left at the hotel by the time they arrived.   
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: zigzag on July 10, 2017, 06:51:30 pm
lighter feels much nicer and is a bit faster uphill. every time i set off for a long ride with all the luggage/electronics/bottles attached it feels demoralising initially - so heavy, unresponsive and road irregularities are more jarring with almost double unsprung weight!! setting off for a training ride with all the bits removed it just floats over the road and feels like an extension of myself - pure joy.
as long as the bike is well put together from reliable components i don't see why heavier could be better - it's very easy to add weight.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: dim on October 02, 2017, 09:20:46 am
I'm busy building a 1981 steel framed Koga Miyata Full Pro that I am using as my daily commuter and which I will use for some shorter Audax rides

It should weigh approx 8.5kg when it's completed (currently weighs 10kg but the wheels are close to 1.9kg) .... I'm changing the groupset to Dura Ace 7800 with the Dura Ace 7900 compact crankset and will possibly fit carbon forks

from what I have read, if a steel framed bike with steel forks weighs less than 8kg, chances are that the frame will be very flexi ....

Carbon on the other hand is different

so, I would not say that bike weiht should be a percentage of body weight .... what does matter is the wheels though .... heavier rider needs more spokes
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Karla on October 02, 2017, 09:50:28 am
Based on the 6.8kg lower bike weight limit for pro racers

Most bicycles in the pro peloton are well over the UCI weight limit (here’s an 8 kg example before adding computers, transponders, etc. (https://www.youtube.com/watch?v=8pzM2GkSo9I&feature=youtu.be&t=169)). That’s because grams that avocational riders obsess over do not matter even to pro racers.

That's Marcel Kittel's bike.  He's an 86kg power sprinter FFS.  A less weight-focussed rider you could hardly have picked. 
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Samuel D on October 02, 2017, 10:44:59 am
I think you’re mistaken. Sprinting is all about the ‘jump’, i.e. acceleration. A good jump gets you on the right wheel or prevents your opponent from getting on yours. Races are very often lost by less than half a bicycle length.

Of the various categories of cyclist, only climbers should be more concerned than sprinters about weight.

However, pro racers labour under the same misconceptions about weight as the rest of us. Abrupt steering movements feel light, ergo the bicycle is quick. It’s an easy one to fall for if you don’t understand the physics to put the numbers in perspective.

Besides, plenty of weekend cyclists weigh 86 kg and think a lighter bicycle would help them keep up with their group. When you tell them they could save 50 watts by wearing a jersey two sizes smaller and drafting on the leeward side, they think you’re exaggerating! People believe the funniest things.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Karla on October 02, 2017, 11:20:44 am
No I'm not mistaken. 

Marcel Kittel puts out 4 figure powers during his sprints, so he needs a bike built to cope with that.  He rides a Specialized Venge, which was originally designed with another sprinter - Mark Cavendish - in mind.  On any mountain stages, Kittel isn't vastly concerned with weight because he he's not contesting for a win or even a placing, just to get round within the cutoff. 

Quickstep's GC man Dan Martin doesn't ride the Venge, he rides Specialized's lightweight bike, the Tarmac.
 
An 86 kg weekend warrior will be putting out a tenth of the power, and doesn't need a Venge, but does need all the help they can get from a light bike. 
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: citoyen on October 02, 2017, 11:30:29 am
In Kittel's case, the rationale will be that stiffer and more aerodynamically efficient frame and wheels are of more benefit in a sprint than lower weight - the thinking will be that the 'jump' can be more effectively achieved by more efficient power transfer and reduced drag than by reducing the overall bike weight. (I make no claims as to the correctness or otherwise of this way of thinking.)

If you weigh under 60kg and can put out ~400 watts on a ~10% climb for several km (http://www.cyclingweekly.com/news/racing/giro-ditalia/strava-stats-reveal-just-how-fast-nairo-quintana-attacked-on-the-blockhaus-at-the-giro-ditalia-330645), the difference between a 6.8kg bike and an 8kg+ bike might be noticeable. I would wholly agree that for a typical Sunday rider weighing 86kg, a lighter bike will make no practical difference at all.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: quixoticgeek on October 02, 2017, 11:43:39 am
In theory it's pretty simple, for a given input of power, speed will be directly proportional to all up weight (rider+bike). Assuming that friction (air and road) remains constant between the two. So if you are putting out 200W, and you plus bike == 100kg, then you will have a speed of x, if you plus bike =80kg and you're putting out 200w, then your speed will be proportionally greater than x.

Where this becomes more complex tho is that aero drag represents a far bigger factor about your speed than bike weight. I often see Dutch bikes with clip on aero bars. They may weigh 25kg, with a 80kg Dutchman on, but in the Omnidirectional headwind, those bars make a significant difference. It's also worth noting that aero drag effects things based on a cube root or some such (no doubt Kim will be long shortly to correct me), so an improvement in your frontal area by x, will have a much more significant impact as a proportion, than a similar change in weight...

Then of course we get to the fun of rotating mass. On my Brompton riding next to a friend on an Omafiets, I notice that my small wheels have less inertia than hers, meaning that if I stop pedaling and coast, I slow much faster than she does. Useful as I'm a faster rider so I can moderate my speed by lifting off for a second...

For anything other than a city bike, I'd question how exactly you get to something that weighs over 15kg. Even an all steel Genesis Croix De Fer is only 11.5kg. Add on a pair of mud guards and racks, and you're still gonna be under the 14kg mark...

Will a lighter bike be faster/easier to ride? Probably. Are there other things you can do that are cheaper and with better gains, probably. Does this mean you shouldn't treat yourself to a lighter bike? Only if you can afford it...

J

PS Conversion of metric to funny units is left as an exercise for the reader.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Greenbank on October 02, 2017, 12:01:58 pm
In theory it's pretty simple, for a given input of power, speed will be directly proportional to all up weight (rider+bike). Assuming that friction (air and road) remains constant between the two.

No. With that assumption that air/road friction is the same between the two then the speed would be the same. It would just take the heavier rider slightly longer to get up to same speed.

On the flat you stop accelerating when the input power is being used completely to overcome friction (air and road), so if that friction is the same between two riders then the same input power will result in the same terminal speed. It's only on the way up to that speed (accelerating) when the mass of the rider is relevant and means more work (power * time) is required to get the heavier rider up to that speed.

So if you are putting out 200W, and you plus bike == 100kg, then you will have a speed of x, if you plus bike =80kg and you're putting out 200w, then your speed will be proportionally greater than x.

Again, not on the flat. And talking about "proportionally greater" doesn't really make sense here, you'd probably say "speed would be inversely proportional to weight" but that's still not accurate given the complexities involved.

Where this becomes more complex tho is that aero drag represents a far bigger factor about your speed than bike weight.

Yes, and aero drag will be significantly higher for a typical 100kg rider than for a typical 86kg rider.

So, on the flat, an 86kg rider putting in 200W will generally go faster than a 100kg rider putting in 200W if they have a similar approach to aerodynamics (clothing/setup/equipment/etc).

However, a 100kg rider will typically be able to put in more power at a certain exertion level than a 86kg rider at the same exertion level, purely because the heavier rider weighs more and their muscles are used to supporting that heavier bodyweight. (Again, it's possible for lighter riders to be more efficient and more powerful than heavier riders, etc).
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Karla on October 02, 2017, 12:24:51 pm
In theory it's pretty simple, for a given input of power, speed will be directly proportional to all up weight (rider+bike). Assuming that friction (air and road) remains constant between the two. So if you are putting out 200W, and you plus bike == 100kg, then you will have a speed of x, if you plus bike =80kg and you're putting out 200w, then your speed will be proportionally greater than x.

Where this becomes more complex tho is that aero drag represents a far bigger factor about your speed than bike weight. I often see Dutch bikes with clip on aero bars. They may weigh 25kg, with a 80kg Dutchman on, but in the Omnidirectional headwind, those bars make a significant difference. It's also worth noting that aero drag effects things based on a cube root or some such (no doubt Kim will be long shortly to correct me), so an improvement in your frontal area by x, will have a much more significant impact as a proportion, than a similar change in weight...

Weight (okay, mass, but we'll assume constant gravity ;) ) has several effects:

1) It slows you down going uphill
2) Rolling resistance increases in direct proportion to weight
3) There's the noted effect on acceleration
4) If your pedalling style involves throwing the bike about, the weight of the bike acts as a damper on this.

The power required to ascend against gravity is proportional to your rate of vertical ascent (plus a constant for not rolling down the hill).
The power required to overcome rolling resistance is proportional to speed (at least for the region that bike tyres are designed to be used in).
The power required to overcome air resistance is proportional to the cube of airspeed.

What the latter point means is that when you're riding up any significant gradient, your air drag falls to virtually nothing and you're basically fighting gravity plus a bit of rolling resistance.  I heard a talk once from a bigwig in BC who said that Chris Froome is 95% fighting gravity on any alpine climb.  When I re-ran the calculation for my friend riding up a pass on holiday last year, it was more like 99% - because we were going at half of Froome's speed so air drag was even lower.


There are several ways in which bike weight will have a bigger effect on a club rider than on Chris Froome:

1) Being 99% rather than 95% of their resistance going uphill means that there's a proportional gain there
2a) Because they are travelling slowly and air resistance is less, rolling resistance will be a larger portion of their overall resistance, so the proportional increase due to greater weight will have a greater effect on them.
2b) The club rider is likely to be running heavier tyres than Chris, so the proportional increase in rolling resistance will again have a greater effect on them.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Samuel D on October 02, 2017, 12:56:35 pm
(Again, it's possible for lighter riders to be more efficient and more powerful than heavier riders, etc).

An astonishing example of that is reported here, (http://www.bikeradar.com/forums/viewtopic.php?t=12974208#p18938705) about Dan Martin.

These discussions can be interesting and pedagogical to the uninitiated, but they usually give the wrong impression to people who lack a nice judgement of scale and proportion. That’s most of us.

For practical purposes, it’s better to simply say that bicycle weight doesn’t matter to performance. The range is usually a matter of 2 kg, the bicycle spends most of its life on approximately flat terrain, the cyclist is an order of magnitude heavier than the bicycle, and there are usually much more significant gains curiously left untaken (e.g. the billowing jersey, the chain last oiled three weeks ago, tyres that defeat Dunlop’s original intention, a lack of sleep, the dreadful British diet, poor riding position (made worse by indoor training with its concentration on power and lack of aerodynamic drag), and the typical weekend cyclist’s amazing inability to read the wind and draft efficiently).

The marginal-gains mantra says we should care about bicycle weight despite all of this, since the burden of weight is in addition to all of the above, but the scale of the effect is tiny. That way lies counterproductive schemes such as Igus pedal bushings. It’s ironic but indicative of the industry that Garmin and PowerTap power-meter pedals use plain rather than ball bearings, needlessly throwing away some of the very power they’re measuring. But hey, they’re lighter!

I heard a talk once from a bigwig in BC who said that Chris Froome is 95% fighting gravity on any alpine climb.  When I re-ran the calculation for my friend riding up a pass on holiday last year, it was more like 99% - because we were going at half of Froome's speed so air drag was even lower.

What pass was that and do you recall the particulars? 99% is an extraordinary result, particularly since most cyclists I encounter use tyres with much greater rolling resistance than Chris Froome’s. When I did a similar calculation for an Alpine climb (Col du Frêne) I did, my work against gravity was only 89%. Bicycle weight over a reasonable range would not have made much difference even on that climb.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Karla on October 02, 2017, 01:02:36 pm
What pass was that and do you recall the particulars? 99% is an extraordinary result, particularly since most cyclists I encounter use tyres with much greater rolling resistance than Chris Froome’s. When I did a similar calculation for an Alpine climb (Col du Frêne) I did, my work against gravity was only 89%. Bicycle weight over a reasonable range would not have made much difference even on that climb.

Probably the Joux Plane.  This was on proper road tyres.

On any hill above a few percent gradient, adding 1 kg to a 100kg all-up weight will slow you down 1%.  It's really not a particularly hard calculation.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Cudzoziemiec on October 02, 2017, 01:04:45 pm
2kg is a very narrow weight range. What makes you pick that figure? None of my bikes is within 2kg of Marcel Kittlel's for sure!
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Samuel D on October 02, 2017, 01:19:00 pm
Probably the Joux Plane.  This was on proper road tyres.

You won’t get close to 99% of work done against gravity on that climb. A bicycle’s chain drive alone is not that efficient. Show your assumptions if you dare.

I don’t dispute your obvious point that climbing speed is dominated by power-to-weight ratio.

2kg is a very narrow weight range. What makes you pick that figure? None of my bikes is within 2kg of Marcel Kittlel's for sure!

It’s a number that felt about right for the range of bicycles we’d consider at any given purchase. If you want a steel bicycle with disc brakes and rack mounts, you’re not looking at 6 kg Pinarellos. If you want a carbon-fibre racing machine, you’re not looking at Bob Jacksons. Bicycles may weigh from 5 kg to 25 kg, but when choosing one, we only consider models with somewhat similar characteristics and design intentions.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Cudzoziemiec on October 02, 2017, 01:25:15 pm
That certainly makes sense at the more specific uses and the lighter weights. But there's a wide range of bikes being used for many purposes. Have a look at an audax for example and you'll see everything from CF roadies to Bob Jacksons and beyond. There's someone here who famously audaxes on a Pashley, and I would be amazed if no one's ever used a Spec Tarmac. Or stand at the side a main road at commuting times.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: citoyen on October 02, 2017, 01:31:41 pm
Sounds about right if you're talking about typical mid-market carbon or aluminium "road bikes" (anything from around £1k to £3.5k) - the weight range for these bikes seems to be roughly 7.5kg-9.5kg. Steel bikes start at around 10kg but there are some that are closer to 9kg.

Of course, that's before you add pedals, Garmin, a couple of full bidons, saddlepack stuffed with spare tube, pump/CO2 and multitool, plus any other accessories. Maybe even a set of mudguards.

Audaxers are another kettle of fish entirely.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Karla on October 02, 2017, 01:36:10 pm
Probably the Joux Plane.  This was on proper road tyres.

You won’t get close to 99% of work done against gravity on that climb. A bicycle’s chain drive alone is not that efficient. Show your assumptions if you dare.


Oh feck off.  If you really want to split hairs about power at the pedals vs power delivered to the back wheel, how about you stop making gross generalisations like "weight doesn't matter".

What are you going to do, attack me with a bicycle pump?
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Cudzoziemiec on October 02, 2017, 01:38:32 pm
Audaxers are another kettle of fish entirely.
Yeah, they range from 22kg* to 122kg.  :D

*A six year old.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Samuel D on October 02, 2017, 02:33:39 pm
Have a look at an audax for example and you'll see everything from CF roadies to Bob Jacksons and beyond. There's someone here who famously audaxes on a Pashley, and I would be amazed if no one's ever used a Spec Tarmac. Or stand at the side a main road at commuting times.

True enough. And from one weight extreme to another, there is certainly a practical performance difference. If you could convince the Pashley rider to use a Tarmac instead, they’d be noticeably faster.

Oh feck off.  If you really want to split hairs about power at the pedals vs power delivered to the back wheel, how about you stop making gross generalisations like "weight doesn't matter".

I only brought up the pedals because they vividly illustrate that weight doesn’t matter. Any super-light pedal you care to mention is notionally bought to go faster but ends up slowing down the cyclist, because weight was saved by eliminating ball bearings. That shows how irrational the weight argument has become, egged on by screeds of scientifically illiterate writing in the cycling press.

It reminds me of the Drillium craze that once hindered top cyclists even as they thought it helped. Now we know better, so we remove ball bearings instead. What a time to be alive!

Secondly, although weight doesn’t matter is a “gross generalisation”, it’s a useful one for most cyclists – certainly more useful than the myths and half-understandings and – especially – the lack of sense of proportion that instead clouds the groupthink. It’s the best sort of generalisation: one that would result in better outcomes for most people if they applied it.

What are you going to do, attack me with a bicycle pump?

You wouldn’t want whacked by the pump I haul around in defiance of the weight weenies, but you’re safe if you show the assumptions that led to your 99% claim. What are you shy about? It was fun until you became so indignant.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Karla on October 02, 2017, 07:11:16 pm

Oh feck off.  If you really want to split hairs about power at the pedals vs power delivered to the back wheel, how about you stop making gross generalisations like "weight doesn't matter".

I only brought up the pedals because they vividly illustrate that weight doesn’t matter. Any super-light pedal you care to mention is notionally bought to go faster but ends up slowing down the cyclist, because weight was saved by eliminating ball bearings. That shows how irrational the weight argument has become, egged on by screeds of scientifically illiterate writing in the cycling press.

It reminds me of the Drillium craze that once hindered top cyclists even as they thought it helped. Now we know better, so we remove ball bearings instead. What a time to be alive!

Superlight pedals?  I never mentioned 'superlight pedals'.  I mentioned power at the pedals vs power at the rear wheel.  You'd just been talking about drivetrain loss in the previous post.  Geddit yet?
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: zigzag on October 02, 2017, 10:58:39 pm
wouldn't it be nice if the bike with all the accessories (lights, mudguards, toolkit, gps, water bottle) still weighed 7-8kg?.. i can ride without all that on a short summer's ride, but most other times the bike gains a couple of kgs that dampen the agility somewhat.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Cudzoziemiec on October 11, 2017, 08:47:37 am
The other day I saw a photo of a friend's hill climb bike: 5.8kg. One of the extreme weight saving measures he's taken is removing the bar tape. I suspect the purpose of this is more psychological than gram reduction: "I didn't take the *&^% bar tape off to give up now!"
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Cudzoziemiec on October 16, 2017, 07:34:06 pm
... there are usually much more significant gains curiously left untaken (e.g. the billowing jersey, the chain last oiled three weeks ago, tyres that defeat Dunlop’s original intention, a lack of sleep, the dreadful British diet, poor riding position (made worse by indoor training with its concentration on power and lack of aerodynamic drag), and the typical weekend cyclist’s amazing inability to read the wind and draft efficiently).
One problem with all that is the non-cycling sacrifices involved. A jersey even tighter than the roadie norm (you suggested wearing one 2 sizes smaller in an earlier post) is probably going to be uncomfortable and is certainly going to make you look a bigger dork than lycra does anyway, getting more sleep means curtailing evening activities ie having less fun or doing less work, eating healthily involves changing your diet relative to family and friends, not eating cake etc, and losing the many excess kilos off your body before the excess grams off your bike, well... Obviously if you're really dedicated to riding speed, you'll do all these things and more, but for the average leisure rider, cycling is only one part of life. So it's easier to concentrate on bike weight even if it's not easier gains.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: dave r on November 19, 2017, 12:20:02 pm
There is a rule of thumb re rider weight vs tyre pressure, which goes pressure in bars = 1/10 rider weight in kilos, to the limit of the manufacturer's spec.
15% deflection is a much better rule of thumb, if a tad difficult to measure.

https://bikesportbicycles.com/wp-content/uploads/docs/TireDrop-OptimizingTirePressure.pdf

http://www.dorkypantsr.us/bike-tire-pressure-calculator.html
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Blodwyn Pig on November 19, 2017, 01:13:00 pm
3 rd post does actually say  ''all up weight 36lbs''  so can one assume this is bike, lights, saddlebag, water bottle, mudguards, heavier grade tyres, tools etc???? That's prob what Olive is, 2 racks, saddlebag, tools, tube,  schmidt, discs, lights,leather Spa saddle, pump!! but then I'm prob over 200lbs, but not fat, 6'2". Sometimes it feels sluggish,  as it would  do, other times, it inexplicably flies along (wind direction taken into account). The only other variable is ME, some  good days some less than good.  ::-)  I have a chum who has a Giant something or  other feather weight thing,  and I can outride him up hill  easily,  so its not all about the bike.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: dim on November 19, 2017, 07:54:57 pm
Differences in seatposts have not made any difference in comfort to me, although I only weigh 66 kg. I’ve tried narrow and fat, carbon and aluminium, all with no perceptible difference (different forks or cranks, on the other hand, have made a clear difference). Anyway, how can you change the seatpost diameter without buying a new frame?

Cyclists believe extraordinary things about bicycle weight. Like you, I’ve been told I’m hampering myself by riding a heavy bicycle – except in my case, mine was about 10 kg and theirs was about 8 kg! (But theirs were carbon, with all the alleged magical properties of that material.) This was shortly before a long climb out of a café where I put in an effort to make a point, dropping three-quarters of the commentators, all of whom were racers.

For steep climbs, the maths is simple: speed equals power divided by all-up weight. In your case, the all-up weight was around 220 lb. Therefore each pound lost (around that weight) produces a speed increase of less than half of one percent. It doesn’t matter where the pound is lost from: belly, frame, or wheel rim. On most hills, where aerodynamic drag and rolling resistance still play a role, the difference is even less than that. And on the flat, the difference is for all practical purposes exactly nil.

thats a load of toss ....

imagine if you rode a lighweight carbon bike 2 1/2 kilos lighter than your 10KG? bike

does it make a difference? ....

YUP ....big time .... thats why people spend a lot of money making their bikes lighter .... I've had many bikes and I know from experience

as for Carbon, anyone who says 'steel is real' has not ridden a decent carbon bike


Title: Re: Ideal bike weight as a percentage of body weight?
Post by: LittleWheelsandBig on November 19, 2017, 07:57:42 pm
Does a 3% weight reduction in the weight of bike-and-rider make a difference? Yes, nearly 3% quicker on steep climbs and close to 0% quicker on flat ground. The rest comes from heads and legs...
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: Ian H on November 19, 2017, 08:47:11 pm
Does a 3% weight reduction in the weight of bike-and-rider make a difference? Yes, nearly 3% quicker on steep climbs and close to 0% quicker on flat ground. The rest comes from heads and legs...

So the question is: can you shave that 3% off just the bike?
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: LittleWheelsandBig on November 19, 2017, 09:08:10 pm
Of course but it'll take a fair bit of dosh. I can take more than 5% off my fat arse and do it for a lot less money. That process is very likely to make me faster on flat ground too, unlike making the bike lighter.
Title: Re: Ideal bike weight as a percentage of body weight?
Post by: sojournermike on November 19, 2017, 09:32:38 pm
Of course but it'll take a fair bit of dosh. I can take more than 5% off my fat arse and do it for a lot less money. That process is very likely to make me faster on flat ground too, unlike making the bike lighter.

Those of us in that happy position may even save money by spending less of food, beer etc;)

I tipped the scales today at 179lbs and a suggested 21.4% body fat. I always take the latter statistic with a large pinch of salt, but losing 5% or even 10% isn't entirely unreasonable. That would be consistent with my 20s running self.