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

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.