[Closed] are we obsessing over bike weights (again)?

Lighter bikes are faster up and downhill. Fact. They make your ride more easier, faster and more fun. A lighter 6" bike will be much more entertaining than a heavier one.

They're easier to manouvre on downhills, easier to pop in the air, you're less knackered from the uphill, it's easier to maintain speed on the downhill and so you enjoy yourself more.

I'd much rather a 27/28lb 5/6" machine to something as big as my current bike which is 30lb. So long's the geometry stays the same, I'd be faster. And no, lighter bikes are not knocked off line more easily until you get to super low weights sub 20lbs.

I'm convinced that losing 2/3lbs off a bike will have more affect than losing 6lbs off yourself, and is much easier. I'm 11 stone now and my riding doesn't really change whether I'm down to 10.5 or up to 11.5.

Grr.

All this 'have a crap' stuff.. you morons. Have a crap when you need a crap. A light bike is still quicker up hills. Ride what you want but don't tell me my taste is wrong just because you're an arsehole.

Lightweight stuff's great, until you encounter rocks. Then it tends to bend..

Never broken any of my lightweight bikes (21lbs) until last weekend when the freehub broke which was one of the most standard parts on the damn thing. And they take a damn hard pounding.

YOU may bend light stuff, but you may be an oaf.

pointless having a weenie bike (apart from for pose factor) if you're not going to race on it

What's pointless is not getting the bike you fancy because someone on a forum informs you that it is wrong.

As for the percentage weight thing - 28 mins up the Cwmcarn on my 21lb bike versus 32 mins on my 30lb bike. Insignificant? Not in a race. Which bike do I usually take? The 30lb one. What does that tell you? That light bikes are faster up hills - SHOCK! 🙄

when was the last time u didnt pick a bike up an check weight ?

people who care about how good their camera is spend the rest of their time licking windows and stalking celebrities

Let's not forget also that a light bike is much easier to accelerate sharply, decelerate, flick through corners, hoick up over obstacles and finesse over technical bits - all of which make a great big difference to your fatigue levels on technical climbs such as Cwmcarn, which could explain my times.

I must admit I've not noticed much difference when saving or adding 1-2lbs on the road bike.. but on the MTB the difference is stark.

And since when is recreational MTBing all about time to the top of the hill? It's about feel, and light feels good on climbs and singletrack.

Weight off the bike feels more noticable, because the bike weighs many times less than you. All that your legs power however is the bike+you.

[i]I KNOW it weighs ABOUT...

Probably find its a lot more.[/i]

Probably not, as it was weighed on some scales which were calibrated (& owned by Trading Standards, who my brother in law works for)

Oh & a 'clem' is a stone. Old NorthEastern word for large stone or rock.

Let's not forget also that a light bike is much easier to accelerate sharply...

only if it escapes you - if you stay on the bike you have to accelerate at the same rate. The bike can move relative to you, but only within a limited envelope.

As for the percentage weight thing - 28 mins up the Cwmcarn on my 21lb bike versus 32 mins on my 30lb bike.

aracer - read the second post.

only if it escapes you - if you stay on the bike you have to accelerate at the same rate. The bike can move relative to you, but only within a limited envelope.

Yes, and it does that all the time on a technical climb.

Barnes - have you ever actually ridden a 21lb bike? Seriously?

And they take a damn hard pounding.

I live in South Wales. Where it's pretty rocky. And I push my race bike harder than my other bikes due to being in a race.

Let's not forget also that a light bike is much easier to accelerate sharply, decelerate, flick through corners, hoick up over obstacles and finesse over technical bits

Uh, you're being stupid Juan. I'm [b]f*cking obviously[/b] not saying a light XC bike is better for donwhill racing.

My race bike has 2.0 Racing Ralphs on it - hardly semi slicks.

Why don't you try riding the same bit of woodsy singletrack on a race machine with 2.0 RRs on it, then on a DH bike with 1kg DH tyres on it, see which feels nicer.

Stupid...

Well molgrips I am not atlking a bout a DH bike but same bike different tyres so you just can see you talk shite. Cornering braking, going through obstacle has more to do with grip than wieght... And I wouldn't want racing ralph for fire road they are as shite as they get.

http://www.analyticcycling.com/ForcesLessWeight_Page.html

Hmmm no mention of rotating mass of wheels & energy required to accelerate same..... technical not!

Juan - we are talking like for like here your, far as I am concerned I'd rather pay a wee bit more & have some similar tyres / rims at 100gms lighter if I can.

If you keep an eye on weight & avoiding becoming obsessive (although it can be a dangerous route to go down) you can easily shave 50g off each component which can amount to 1kg in a full build - okay so thats f all when compared with my 87kgs, but seems to make a difference in the weird & wonderful world that I occupy. 😉

Racing Ralphs get me through the technical sections of races pretty damn quickly. They work for me.

As for grip vs weight - it depends on the course. If it's very tight and technical (like say a Gorrick) then your overall speed will be slow, but there will be a lot of acceleration and deceleration. So grip is less important than low mass. And rolling resistance of sticky DH tyres is typically very high. Everyone interested in bikes knows this, apparently apart from you.

Do not tell me I am talking shite. I know a lot about bikes and I am very intelligent.

Something I learned in my early riding days 20 yrs ago, IT MAKES NO DIFFERENCE TO THE GRIN FACTOR.
Just ride the bloody thing.

Juan is wrong. I can't really put that much different really.

Well, I'm pretty sure I would break a 21lb race bike without changing my riding style and I'm no fatty or phat air freak.

But in answer to to OP - judging from the answers there seems to be plenty of weight weenie obsessed here. 🙂

[i]Hmmm no mention of rotating mass of wheels & energy required to accelerate same..... technical not![/i]

Oh dear....

Please show me the maths that demonstrates the difference between mass and rotating mass when the context is a bicycle....

Please show me the accelerations produced by the average STW rider....

Rotating mass in bicycle terms is just the same as mass; the old 'a pound off the wheels is worth two/three off the frame' might give some small advantage but you'd be better off getting more aero than losing weight.

I'm not saying light bikes aren't more fun, or more desirable, but the effect of bicycle weight when considered as a part of the total weight of bike+rider+Camelbak+water+all the other stuff people seem to need is way less important than people think.

Juan wrote, "MWAHHHHHHHH yes you are absolutely right. Now do something go to Fort william. Take your bike with you. Take two set of tyre. One will be apure semi slick XC tyres. The other will be a pair of very heavy/sticky maxxis DH tyres. Now you ride the same course twice and you tell me if your above statement it right... "

Do you think those tyres are better because they're heavy? Here's a better comparison- fit heavy XC tyres, something horrible like a Factory XC, then fit DH tyres that weigh less. WHich is better? Still the DH tyres. If you really believe that heavy is better, why is it that your only example has nothing at all to do with weight?

Please show me the maths that demonstrates the difference between mass and rotating mass when the context is a bicycle....

Well do a Physics A level and they'll tell you all about it 🙂

To accelerate a bike forwards, you need to give your wheels (and the rest of your bike) forward momentum, but you ALSO need to give the wheels angular momentum. The two are independent - you can have a wheel spinning and not moving forwards - and you can have it moving forwards (as in the back of a car) but not rotating.

Can I suggest something? Can all posters state the approximate weight of the lightest bike they have ridden? I'd like to see if anyone can say 'yeah I've ridden a 20lb XC machine and it felt no different to a 28lb AM machine'.

aracer - read the second post.

I still reckon it's the tyres - or maybe a less efficient pedalling suspension system - or just possibly psychological.

In compliance with your latest request I'll point out that I ride a 21.5lb full-sus (and have a <15lb road bike).

If it's very tight and technical (like say a Gorrick)

Barnes - have you ever actually ridden a 21lb bike? Seriously?

of course not, as I've said before, I wouldn't take anything I felt as a measurement anyway. Certainly, if the bike accelerates differently to me for more than a very short period it will necessarily be somewhere else 🙁

Well do a Physics A level and they'll tell you all about it

Crikey - way too long since I did my Physics & Maths A levels, but I can assure you that acceleration of a 800g weight weenie tyre & rim combo compared to the same of a 1300g all mountain/trail combo is significant - and then multiply that by all the start stops in a single mtb ride.

It's ok, honestly, there is a large section of the bike industry and a significant part of the advertising industry (in bike terms), plus a number of bicycle magazines who depend to a great extent upon people believing the 'reduce weight by X grammes and you'll be lots faster' thing.

It's not true, but that's ok..

As I said, it seems that bicycles don't obey the laws of physics anyway...

Light bikes are great, but they don't make you noticeably faster, unless of course:

[i]There are two "non-technical" explanations for the effects of light weight. First is the placebo effect. Since the rider feels that they are on better (lighter) equipment, they push themselves harder and therefore go faster. It's not the equipment that increases speed so much as the rider's belief and resulting higher power output. The second non-technical explanation is the triumph of hope over experience—the rider is not much faster due to lightweight equipment but thinks they are faster. Sometimes this is due to lack of real data, as when a rider took two hours to do a climb on their old bike and on their new bike did it in 1:50. No accounting for how fit the rider was during these two climbs, how hot or windy it was, which way the wind was blowing, how the rider felt that day, etc.

Another explanation, of course, may be marketing benefits associated with selling weight reductions.[/i]

From wikipedia, and so taken with a pinch of salt, but still way more dependable than STW..

Crikey, if you understand the website you posted you must also know just how incomplete their model is. For one thing, it only gives rolling resistance up to "paved but rough surface" which would be more or less a very good fire road, beyond that you have to guess, and it doesn't qualify what sort of bike or tyre so the rolling resstances could be wildly off. It doesn't take into account variations in slope at all- when did you ever ride a completely constant slope? Or obstacles on the trail. But most importantly it doesn't give you the time lapsed, just the time saved which leaves the numbers meaningless unless you go digging.

Basically, if we could punch numbers into that and it'd tell us how long it takes us to ride the distance in total, that'd mean we could sanity check the numbers. I don;t need to give you numbers to show the weakness of the set you've provided. But, here are some anyway.

Take a nice sensible real world climb, let's say 10km of climb for 500 metres of gain- sounds like a fairly typical trail centre "one up one down" climb to me. Throw in my exact weight numbers.

The numbers that you get back say that if you save 3 kilos (the difference between my Kraken and my Soul, effectively) and it tells you you save 74 seconds, and that those 74 seconds equate to 340 metres. So simple maths, we have an average of 4.5 m/s, which would mean that you've done your 10km climb in 37 minutes, at an average of 10mph, no breaks. Don't know about you but I bloody don't!

In short, I think that both the conclusion you drew from the model is wrong, and the model itself is wrong 😉

From wikipedia, and so taken with a pinch of salt, but still way more dependable than STW.. 😆

Hmmm interesting, think I'll have to give my son a few calcs to do whilst he's revising for his mech eng degree & see what he can sus out from first principles.

Bet I'll still be pissed off that I put some 570g AM rims & fatter tyres on my prince albert though 😥

but I can assure you that acceleration of a 800g weight weenie tyre & rim combo compared to the same of a 1300g all mountain/trail combo is significant - and then multiply that by all the start stops in a single mtb ride.

but you're multiplying it by the wrong thing - yes, the angular component more or less doubles the effective inertia of the rotating components - but unless you take them off they have to accelerate at the same rate as the rest of the bike and the rider - which have about 50 times the inertia - so the the 1.3 - 0.8 = 0.5kg, even doubled up is still less than 2% of the all up figure.

...and energy used for acceleration in cycling (even technical MTB) is a tiny proportion of the total energy used.

Do you see what you've done? You've got me agreeing with sfb on a weight weenie thread. Have you no shame?!

The model isn't perfect, but it does go some way towards quantifying the silliness inherent in the 'help me save 2 kilos and therefore watch me ride off into the sunset at 100mph' argument.

It's also the best analysis of weight saving that I'm aware of, and, as above, if you can show me a better one, I'm ready and waiting.

SFB gets closer than anyone to the real decider; we all accept that power to weight ratio is the real defining equation when it comes to bicycle performance....

Changing bicycle weights by a realistic figure of 1, 2 or even 3 kgs doesn't impact that much on your power to weight ratio; the weight has to include everything from your socks to your multitool as well as you, your breakfast and your bike.

If lightweight was so great, why do mountain bikers ride about with half the bloody kitchen on their back?

If lightweight was so great, why do mountain bikers ride about with half the bloody kitchen on their back?

Sorry - slight diversion there, I'll get back to arguing on your side again in a minute.

Ahem, 'most mountain bikers I see at trail centres'... 😀

Now I am really laughty out loud.. Please if you think gorrick it technical get a grip...

F*cking hell Juan if you were here I'd thump you. Maybe at the speeds you ride at Gorricks aren't technical, but at my lightening pace it's a white knuckle ride. Trails alone aren't what makes a technical ride, but of course if you knew more than c0ck all about biking you'd understand that. Otherwise, that Lewis Hamilton would have to be a right useless driver - all he ever drives is totally flat and smooth!

I'm a competent technical rider, and I've ridden all sorts of trails. So please stop insulting me for absolutely no reason. Your default positions seems to be that I am a complete idiot - whereas in fact, if you resepcted me as an experienced cyclist and took the time to talk through and understand what I am saying you might learn something, or at least see what I am trying to say. Riding a Gorrick course slowly is easy, riding it very fast is not.

As I said, it seems that bicycles don't obey the laws of physics anyway...

That or your model's incomplete...

From wikipedia, and so taken with a pinch of salt, but still way more dependable than STW..

Who do you think writes Wikipedia?

Barnes and others - your models seem only to take into account the amount of weight lifted over a height. This is clearly not the only factor in a technical off-road climb.

I did some calculations on here a while ago that showed that a given weight saving made far more difference to the acceleration, deceleration and handling of a bike than it did to the amount of energy required to lift it up the climb.

Here's something. You are using a simple model that takes into account the mass of rider and bike and the height of the climb. Of course, there is rolling resistance and air resistance to take into account, but those two things would be the same. But consider this - a flat piece of tight twisty singletrack ridden hard at say 15mph will raise your heart rate quite a bit. A flat piece of fire road at the same speed will hardly raise it at all. Try and ride the singletrack at 17mph and you will find it a hell of a lot more difficult than the speed increase woudl suggest. Why? Cos a lot of effort goes into controlling the bike and braking and accelerating.

I'm obsessing a little with weight, as being new to XC racing I took my stock trail steel HT, swapped a few components/tyres etc.. dropped 2-3lb out of the bike and I'm definitely noticably faster, I've timed myself on loops.

Can't see why people have a problem with trying to make their bike as light/perfect as possible for whatever budget they have to spend on thier hobby.

I have re spoke's first post of the page and, although he might be right to some extend he kind of forget something... I want to finish my bloody ride. I don't know how 27 lbs translate in real world figures (aka metrics), but it seems very light for me. To take the rim example, we (by we I mean me and my mates) have tried the DT rims (going from mavic 717 to dt whatever they are). After 2 month everyone is back to mavic. Dt were lighter but much more fragile. So all the weight figures you guys are quoting are good when you are doing "super gnar tech races like gorick" but when you ride to normal speed in the real stuff it's a whole different story. And yes I am sorry molgrips but putting gorrick and technical in the same sentence is talking shite.

Once again if light is better, light is stronger why oh why DH bikes are no XC light?

F*cking hell Juan if you were here I'd thump you. Maybe at the speeds you ride at Gorricks aren't technical, but at my lightening pace it's a white knuckle ride.

I had a ride with a friend of mine today. I use to ride at gorrick he uses to do very well (he won the sport category at busas in dorset) so not a "slow rider" by any account.

Now if you want I can ask him to pm you about today's ride.

Crikey wrote, "SFB gets closer than anyone to the real decider; we all accept that power to weight ratio is the real defining equation when it comes to bicycle performance...."

I don't think we do tbh. PTW doesn't cover what people keep referring to as things like "flickability" "responsiveness", or what I call being able to muscle the bike. Well, actually it probably does but not in the way SFB means.

But consider this - a flat piece of tight twisty singletrack ridden hard at say 15mph will raise your heart rate quite a bit. A flat piece of fire road at the same speed will hardly raise it at all. Try and ride the singletrack at 17mph and you will find it a hell of a lot more difficult than the speed increase woudl suggest. Why? Cos a lot of effort goes into controlling the bike and braking and accelerating.

[i]That or your model's incomplete...[/i]

Then model it better...

[i]Cos a lot of effort goes into controlling the bike and braking and accelerating.[/i]

Undoubtedly so, but changing the weight of a bike by a couple of kilos when the [b]overall weight[/b] of bike+rider+kitchen sink is 100 or so kgs, doesn't make the difference you are claiming, unless bicycles have some special subset of physics that we are unaware of.

[i]I don't think we do tbh. PTW doesn't cover what people keep referring to as things like "flickability" "responsiveness", or what I call being able to muscle the bike[/i]

The [b]actual[/b] weight difference is so small that if affects your ability to 'muscle' the bike, you shouldn't really be out by yourself.

Once again if light is better, light is stronger why oh why DH bikes are no XC light?

Did you read about Steve Peat's bike for the world champs? Paint stripped off hubs/wheels etc, ti bolt kits, half the riders only running 3 rotor bolts, 160mm rotors. Why?

Without wanting to agree with you Juan, because I think you're a colossal ****t (and I don't think I'm alone there, which is nice...), I must say I don't think Gorricks are technical in the normal sense of the word as it's come to be used, what they often are is pretty tight and twisty with lots of very hard accelerations, which I guess is what Molgrips was pointing out.

No one has said lighter is strong either, but heavier definitely isn't necessarily stronger, see £50 Tesco bike vs S-Works Stumpjumper (for example).

Re carrying the kitchen sink, I don't either, a bottle, a multi tool, a CO2 pump my phone, £10 and my keys for any normal ride!

Crikey, you're oversimplifying there again, controlling the bike doesn't always mean doing something with the whole 100kg or whatever of rider + bike. Think balance on northshore, or moving the bike under you in a rockgarden, or squashing a jump, or floating the bike over roots- you're often not shifting the whole package, you're moving the bike around the rider (and sometimes the rider around the bike). Then, think popping a manual, where rider weight is used to move bike weight.

Once again if light is better, light is stronger why oh why DH bikes are no XC light?

You do rather sound as if you have been drinking.

Downhill bikes are made for downhill, XC for XC - this is obvious, no? Downhilling requires the dissipation of much larger amounts of energy and hence the bikes need to be stronger (I can't believe I am having to explain this).

Actually, this is a totally pointless discussion. I am not saying XC bikes are best for downhilling. I am saying that LIGHT WEIGHT is positive when it comes to climbing and bike handling. So that means if you make your bike as light as you can without it breaking for the kind of riding you do, then that is rather nice.

I am not saying take an XC bike downhilling in the alps, and I don't understand how anyone could possibly tihnk I'd be saying such a stupid thing.

And as for Gorricks being technical, well that's another issue. Technical means that you need technique, right? In the Alps, you need tehcnique just to make it down in one piece, absolutely. At a Gorrick, you need quite a lot of technique to ride the trails very fast. It's different technique, but still technique, therefore they are technical trails. I raced a roadie once - he was a far far fitter rider than me, but I beat him - because he did not have the technique to do the singletrack as fast.

Technical does not mean the same thing as hard. And for the record I never said Gorricks were gnarly either.

crikey wrote,

"The actual weight difference is so small that if affects your ability to 'muscle' the bike, you shouldn't really be out by yourself. "

Is it really? The weight difference between my Soul and my Hemlock is 20% of the weight of the Soul, is that small? Don't throw back "But combined rider and bike weight" because I think we've covered why that isn't always useful.

You keep saying "If you don't like this model, make something better". No. We don't have to produce something better to point out that what you have is giving false results. It's you that's trying to prove an argument with a poor model, you provide something better, don't try and pretend that the weakness of your model doesn't matter because it's the best you've got- it's still weak.

Then model it better...

I am trying mate, few people seem to be listening 🙂 I even did the maths once on here, CBA to do it again.

I must say I don't think Gorricks are technical in the normal sense of the word as it's come to be used, what they often are is pretty tight and twisty with lots of very hard accelerations, which I guess is what Molgrips was pointing out.

Thankyou. There are a lot of those yellow brick roads at Swinley where everyone trundles around them very gently during races. Wringing more and more speed out of your bike on some of them is pretty damn difficult. And most racers seem unable to do it, which is why I get stuck in so many damn traffic jams there.

The actual weight difference is so small that if affects your ability to 'muscle' the bike, you shouldn't really be out by yourself.

Are you just conjecturing here or speaking from actual experience of having ridden light bikes?

Did you read about Steve Peat's bike for the world champs? Paint stripped off hubs/wheels etc, ti bolt kits, half the riders only running 3 rotor bolts, 160mm rotors. Why?

Without wanting to agree with you Juan, because I think you're a colossal ****t (and I don't think I'm alone there, which is nice...), I must say I don't think Gorricks are technical in the normal sense of the word as it's come to be used, what they often are is pretty tight and twisty with lots of very hard accelerations, which I guess is what Molgrips was pointing out.

I'd just like to say that Nick isn't alone 😉

You have no model, nothing at all, no attempt scientifically, mathematically, sensibly to suggest a way of quantifying the gains you think you can make from having a lighter bike...

Nothing. Nowt.

Yet you continue to make completely unsubstantiated claims regarding the benifits of a bike that is lighter by... Oh, you never said..

Produce a sensible counter argument instead of 'muscling the bike around' and maybe the debate could go somewhere...

Careful you don't fall off that high horse Juan! And incontinence is a serious problem, I'd get that checked.

I don't really see the point you're making about Steve Peat's bike and the weight, obviously it's not 10kg, but then are you saying that if Nino Schurter had ridden a 20kg bike at the XC worlds he'd have gone faster and won by more?

Again, a £50 Tesco 'dual suspension' bike will weigh more than Steve Peat's V10, would it be stronger?

Nino Schurter had ridden a 20kg bike at the XC worlds he'd have gone faster and won by more?

[i]Are you just conjecturing here or speaking from actual experience of having ridden light bikes?[/i]

I've ridden 'light' bikes, raced mountain bikes and won on a Cannondale that was the lightest frame I could get my hands on. I've raced on a 22lb roadbike and won, I've raced on an 18lb roadbike and didn't win.

Bike weight isn't as important as you think it is.

Bike weight isn't as important as you think it is.

it's probably more important than *I* think it is 🙂 The only time I care is when I have to carry the ****er!

Juan, you insulted me by accusing me of poor reasoning. That's calling me stupid, and an insult.

You have no model, nothing at all, no attempt scientifically, mathematically, sensibly to suggest a way of quantifying the gains you think you can make from having a lighter bike...

I'll type it again for you.

When you are on a technical climb, there are many many points where you have to brake and accelerate. You also have to move the bike to the left and right quickly to avoid rocks and roots etc (whilst your centre of mass continues in a largely straight line). You also have to lift the bike up over certain obstacles. I don't know why you think this would not be easier with a light bike..? Your body needs to move less to get a light bike to move in response to it, which in turn saves energy.

Do you ride with a heart rate monitor? I do. On technical downhills where I do not need to pedal, my heart rate can be up in the middle of its range, around 160, without making a single pedal stroke. This is because handling the bike takes energy.

I would come up with a mathematical model but it's just too damn late and I need to go to bed and work tomorrow. But if you are lucky you'll get a model.

Btw, can I ask what bike you ride and how much it weighs?

Produce a sensible counter argument instead of 'muscling the bike around' and maybe the debate could go somewhere

Mmm or you could just listen to other people's experiences, rather than just assume we're gullible easily-led techno-weenies who think something's good just because it's expensive. That is what you think, isn't it?

Bike weight isn't as important as you think it is.

How important do I think it is then?

Now if light bikes where that good, why the same Nico schurter, choose to ride a "heavier" bike on a race that was longer?

Well there could be several reasons. Geometry and comfort for two.

I do not always take my lightest bike to races.

I think you are missing my point. What I am trying to say is that on technical climbs and singletrack light weight can make you go significantly faster, but there may be other factors which are more important in some cases. I am not saying you cannot win unless your bike is light, I am not saying that you will win if your bike is lightest.

Why else would XC racers most often use very light bikes?

Crikey wrote, "You have no model, nothing at all, no attempt scientifically, mathematically, sensibly to suggest a way of quantifying the gains you think you can make from having a lighter bike.."

That's correct- with the exception of "sensibly", which is all we're doing. All we have are real world observations- which of course are exactly as [i]scientific[/i] as models on a screen. We also have the ability to point out the obvious failings of your model, and the ability to point out the blindingly obvious. I can see why you'd consider that to be inferior to your inadequate model wth its innacurate results 😉

Why should we provide a model to show what anyone who has ridden a bike knows, that sometimes the rider and bike move differently? This is where the simplistic argument about rider + bike weight falls apart. How does that work in any of the situations I mentioned above which you're so studiously avoiding? Can a 30kg rider manual a 20kg bike in exactly the same way as a 40kg rider would manual a 10kg bike, assuming comparable geometry? Or sidehop it? Or unweight it over roots? Of course not- yet all nice straightforward examples of "muscling the bike about". So clearly, models or not, there is a real difference between rider weight and bike weight. So there goes one of the attempted rebuttals we've seen throughout this thread.

People who want to argue against the benefits of weight loss often end up hiding in maths, and don't bat an eyelid when their maths fail to reintegrate into the real world. It's also, I suspect, why they always fixate on power-to-weight and on climbing- they're easier to put into an equation. Not so easy that you can give us any results that actually work in the real world, but still, easier. And if it's not in an equation, then it's not scientific and it doesn't exist.

"regarding the benifits of a bike that is lighter by... Oh, you never said"

Er, actually I did. Several times.

[i]That is what you think, isn't it?[/i]

Wind your neck in, you'll go faster...

I think that people in general over-estimate the extent to which having a lighter bike affects their performance. I think the main effect is a placebo type one. I think that modelling bicycle and rider performance is very difficult, and requires a number of assumptions. I think that lightness in bike terms is a good thing, but I don't think that the average rider will gain much by lightening a bicycle by 2-3-4 kilos.

The beauty of cycling and cycle sport is that it really isn't about the bike; that's why you can't walk into a bike shop and pay £5000 and come out a better, faster rider.

I've been riding and racing for 20 odd years now, and I've been in the position where I could buy light kit. My current road bike is 16.5 lbs, but I was quicker on a 531 22lb bike.

As I said, there's a whole industry dependent on selling the latest performance upgrade to people on the basis of lightweight....

They wont go bust anytime soon.

[i]People who want to argue against the benefits of weight loss often end up hiding in maths, and don't bat an eyelid when their maths fails to reintegrate into the real world.[/i]

Ah, the old 'you dont get it, hiding in your laboratory, this is the real world' stuff...

Whatever, been there, done that, know that you can lighten your bike all you want and it wont make you any quicker.

Night boys.

well molgrips I can't find the bit where I say you are an idiot.
If you don't like people telling you your reasoning is not good maybe you should stop interacting with other people...
Plus I am waiting for you and njee to answer my other point.

P.S. if you found south well rocky I really need to create a charity groupt to buy you a plane ticket.

crikey wrote, "Ah, the old 'you dont get it, hiding in your laboratory, this is the real world' stuff..."

Well, no. I took your model, put the numbers into it and it gave us back answers which you agreed were clearly wrong, remember? You've kept on trying to use the model despite knowing it to be incorrect. But you have the nerve to talk of science.

But once again I see you've ignored all the rest of my post. A cynic might suspect you don't know how to respond to it, given the number of times you've done that...

I think that people in general over-estimate the extent to which having a lighter bike affects their performance.

I do not estimate the extent at all! I merely said the effect was significant.

Placebo effect? Not with me. I am a critical scientific thinker.

And I have not bought a lightweight component for three years. I built my race bike as an insurance replacement in 2007 and it's stayed exactly the same. It does not have the lightest of everything or the most expensive. It has disks and riser bars, and it's full sus.

I don't think that the average rider will gain much by lightening a bicycle by 2-3-4 kilos

Rider or racer? And are you talking about times here or riding pleasure? I would say that 4kg would make a significant difference do the handling speed of a bike and hence riding enjoyment (no-one likes riding a tank, do they?) and the overall position in say an MTB marathon.

Do you think you would not notice if I sneaked up and tied 9lbs of lead around your frame?

that's why you can't walk into a bike shop and pay £5000 and come out a better, faster rider.

Yeah you could. If you were riding a £500 stumpy and you bought a bike like my Heihei, I would bet you'd end up a good few minutes quicker up the Cwmcarn climb. Partly because of the weight, and partly because of the ride and handling characteristics.

For a while I had a 37lb Orange Patriot. Ask anyone who went riding with me, it was very slow up hills.

P.S. if you found south well rocky I really need to create a charity groupt to buy you a plane ticket.

I define rocky as a place where there are lots of rocks on the ground. I am absolutely sure it's not the rockiest place in the world, however there are plenty of rocks lying around so I will continue to call it rocky.

You insulted me here too:

so you just can see you talk shite

Ah, wouldn't this thread be so much better if we could put Juan in a sack- a heavy sack ideally so it does downwards faster-, tie it to some of those rocks he's so fond of and throw him in the sea?

Me plus 20lbs bike = 100kgs, me plus 30lbs bike = 105kgs, just in potential energy alone thats a 5% difference which is significant enough for me on the 500m of ascents I regularly take in on a ride around the chilterns...

Now wheres that maths book so I can add in the energy taken up in accelerating the wheels from 5 to 20 mph say 20 times in a 30 mile ride... no actually I can't be bothered, I'm not going to change anybodies view on the topic so might as well go to bed. Night all

It's funny how [s]people[/s] [s]rider[/s] [s]racer[/s] sorry race champion seems to be good at eluding questions. Plus saying you are talking shite is not an insult, saying to someone that is a twaàt is.
So I'll ask again molgrips how many races have you won, you must have wont some as you seems to be so fast.
I have been to wales and I wouldn't say there is lots of rock on the grounds. But as I perfectly willing to accept that the trail centre in the south of wales make an ergodic system of the riding in south wales.

I shall ad that if you're slow on an heavy bike but not on a light one, it's fitness. I know some pretty good riders, and to be fair they are as fast on a sub 13 kg carbone bike to go uphill as they are on a 16+ kg mini DH

Edit

I'm not going to change anybodies view on the topic so might as well go to bed. Night all

Bow to that...

Why should we provide a model to show what anyone who has ridden a bike knows

When you are on a technical climb, there are many many points where you have to brake and accelerate. You also have to move the bike to the left and right quickly to avoid rocks and roots etc (whilst your centre of mass continues in a largely straight line). You also have to lift the bike up over certain obstacles. I don't know why you think this would not be easier with a light bike..? Your body needs to move less to get a light bike to move in response to it, which in turn saves energy.

On technical downhills where I do not need to pedal, my heart rate can be up in the middle of its range, around 160, without making a single pedal stroke. This is because handling the bike takes energy.

Did you know that a lighter rider will go downhill *faster* than a heavier rider on the same bike, assuming that the bike setup is adjusted accordingly?
Go on.. Ask me how...
Actually, don't.
In the end the lighter rider came third behind the heavier rider and the bloke on the Halfords bike because his full-body spider man suit slipped down over his eyes.
In the real world you could probably collect enough data to exclude factors such as differing suspension design and rider ability to prove that lighter bikes are faster, but what would be the point?
Light bikes are fun. Sometimes a bit sketchy and fearful amongst rocks, but nonetheless fun.

as normal an interesting thread turns into , a slagging match,, especialy as the evening progresses, but it is fun to watch from the side lines,, and read those interesting well thought out arguments

we all know that it's the percentage of matching anodizing /paint that makes the bike fast

It's very disappointing that for some it's become so very personal.
It's not important, yet the vile language & insults being flung about makes you wonder quite why some of the guys here take it so personally.
Quite depressing re-reading some of the posts here.

Juan, I don't win races, I'm too fat. The fat's not in my brain though, so my analysis of the Physics involved is not affected 🙂 Plus, no-one ever passes me in races on the flat or downhill bits 🙂 Winning races has nothing to do with understanding bikes, does it?

Aracer - I haven't come up with a definitive reason why my light bike is so much quicker up Cwmcarn; I have some ideas, but I can't prove either way. I do think the acceleration and deceleration is the main issue however.

Ti29er - I do not really object to people having a different point of view. What I really object to is people telling me I'm some kind of brainless idiot who minces about shelling out tons of cash because some magazine tells me to on the basis that I think it'll make me into a super fast race winning wonder kid.

Please, I'm a reasonable thoughtful chap, so let's put our arguments forward without the constant veiled insults (Juan, you are getting insult confused with epithet).

Well said Ti29er, ade ward & bike whisperer.

Having slept on the issue, I'd just like to conclude by saying that on a long slow climb & with all other things being equal my 8.5st girlfriend is going to have to expend approx 8% more energy to get to the top hill if she used a 30lb bike instead of a 20lb bike.

And yes before you start flaming me for ignoring wind resistance rolling resitance etc, in reality it's the hills that most people find the hardest and at 5mph struggling uphill those factors are going to be fairly minimal on their effect on the percentage of effort required.

Maybe weight is not the be all & end all, but to ignore it & pretend it doesn't matter makes no sense to me

I haven't come up with a definitive reason why my light bike is so much quicker up Cwmcarn; I have some ideas, but I can't prove either way.

Is the HeiHei your 21lb bike? Extremely light for one of those I'd have thought - what's the build?

Maybe weight is not the be all & end all, but to ignore it & pretend it doesn't matter makes no sense to me

but most of us are quite a bit heavier than that, so the figure would be closer to 5%, which may be too small to feel. I would estimate my energy levels vary about 30% from day to day. I don't think ayone is saying it makes [b]no[/b] difference, only that the differences are too small to be important, except in racing and psychologically, and probably not worth paying much money for.

I agree with Molgrips, although not his dogmatic, aggressive and over sensitive delivery. 😕 A lighter bike is easier to manoeuvre in technical situations.

I'm a distinctly average physicist, but this would be relative intertia between the bike and the rider, since the two components are not fixed and rigidly linked together.

Less intertia equals less resistance to acceleration/deceleration which is something you do all the time when manoeuvring the bike about. I don't think forward motion would have much of a role in this sort of activity, at least at the 'forces' level we've decided to examine it at here.

I guess there's a similar model between the rider and the bike during these events as there is to suspension - and it would be the same reason why its good to get unsprung mass as light as possible. i.e less inertia equals more responsive suspension.

Having read most of this thread, I think the answer to the OP is "yes".

Apologies for being over sensitive, I lost the required STW perspective and got annoyed last night...

Is the HeiHei your 21lb bike?

Yes, and to show I'm not a stupid weight weenie idiot, here's the build. It saves weight where it can do it without compromise:

Kona Heihei 2007 frame, Fox RP23 shock 19"
Pace RC39 80mm forks
Tune headset
Syntace F99 105mm stem
Easton monkeylite XC carbon bar low rise 24" width
USE alien carbon seatpost
Flite SLR saddle
ZTR Olympic rims
XTR hubs
Sapim laser spokes
Some lightweight skewers I forget what
Racing Ralph 2.0 with Stan's tubeless system including the rim strip
XTR cranks
XTR brakes 160mm centrelock rotors
XTR mechs front and rear
Dura Ace bar-end thumbshifters with Paul's components bar mounts
Xpedo ti pedals
Ritchey WCS foam grips

Of those things, people will laugh at the following:

Seatpost - I have confidence it won't break
Saddle - comfy enough for 3-4 hours in the saddle, but this is an XC race bike
Skewers - a possible concern, although they've been great so far, good cam action
Grips - cheap as chips and I find them as comfortable as any, so may as well save the weight
Stem - must admit I am a bit concerned about the 4 bolt stem and the bars, can't decide if there's a problem or not
Shifters - they actually work really well, cost WAY less than XTR and weigh loads less too.
Forks - they've been excellent, although I do somewhat wish I'd gone for the 100mm version of the same fork.

It comes up as 21.5lbs on my cheap fish-weighing scales (which I think may over-read slightly, not sure).

which may be too small to feel

May be? Well we are telling you it's not - at least the way I ride it's quite evident.

And so what if it's psychological? Most of us ride for fun, not performance - and if it feels really nice to ride a light bike (for whatever reason) then surely that's ok?