• This topic has 202 replies, 52 voices, and was last updated 12 years ago by hock.
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  • Saving circa 500g on wheels………
  • crikey
    Free Member

    If you look at the whole picture (accelerating, braking, handling and suspension performance) it is significantly worthwhile

    In the interests of the provision of enough rope, perhaps you could actually explain this bit, because you haven’t done so yet.

    Lighter wheels are easier to accelerate. This is a fact.

    But you aren’t just accelerating the wheels…

    So come on, Professor, give it your best shot.

    TandemJeremy
    Free Member

    ratio of sprung to unsprung weight has s significant effect on the suspension performance – one reason why motorcycle racers use the lightest wheels they can.

    skywalker
    Free Member

    Lighter wheels accelerate faster, we already agree on that right?

    They handle better because of the reduced gyroscopic effect. You can notice this by simply putting on slightly lighter tires!

    They stop quicker for the same reason they accelerate quicker.

    They cause your suspension to work more efficiently because the suspensions job is to keep the wheel in contact with the ground. The wheel is forever being bounced up and down by rocks/roots/bumps etc. The heavier the wheel, the more work the suspension has to do to keep in contact with the ground. The less unsprung weight it has to deal with, the better it can do its job.

    All this combined makes saving weight on your wheels worth while.

    Not really much to argue about is there?

    I already explained on the last page young grasshopper.

    You don’t even have an argument, I really don’t see why you are still going on, you are just making yourself look silly.

    Edit: Thanks you TJ, finally someone with some brain power.

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    crikey
    Free Member

    ..Ok, now apply this to the real world, and lets see the actual effects rather than the ‘makes your skin smoother’ comments.

    Tell me the effect of reducing the weight of your wheels by 500g on a mountain bike ride of 3 hours.

    I think that if you did the ride 5 times with ‘heavy’ wheels, then did the ride 5 times with ‘light’ wheels, the difference between the two would be less than the difference between your fastest and slowest ride on each wheelset.

    You’re hammering a theoretical issue, one that is simply lost in the noise of mountain bike performance. It’s a great marketing tool, because at heart, there is a small, imperceptible gain, but in the real world it makes no difference at all.

    Especially when the rider of these ‘light’ wheels is wearing baggy shorts, and carrying a Camelbak with 3 litres of water and a load of crap, riding a full sus, upon which his ‘acceleration’ is severely limited by the bouncing and the squidging and the big fat tyres….

    crikey
    Free Member

    You don’t even have an argument

    Lol.
    You’ve plucked a wikipedia article out that DISAGREES with your assumptions….

    Bedtime for you sonny Jim.

    TandemJeremy
    Free Member

    cricky I actually suspect the difference is more than you seem to be saying as you do spend a lot of time accelerating and braking as well as going over bumps and turning – all of which are affected by the lighter wheels.

    However its almost impossible to quantify as you say it will be lost in the “noise”.

    Going between extremes of tyres on the tandem – from the DH ones to the touring ones is nearly a kilo and a half 🙂 Drag as well in that of course as well as differnt profiles but that makes a noticeable difference

    crikey
    Free Member

    …and you still think that ‘light’ wheels can be accelerated on their own

    Look at your bike, the wheels are connected to the bike, which you sit on.

    This is why

    How can it be that wheel inertial forces are nearly insignificant, when the advertisements say that inertia is so important? Quite simply, inertial forces are a function of acceleration. In bike racing this peak acceleration is about .1 to .2 g’s and is generally only seen when beginning from an initial velocity of 0 (see criterium race data in Appendix D ). Furthermore, the 0.3kg/0.66lb difference in wheels, even if this mass is out at the rim, is so small compared to your body mass that the differences in wheel inertia will be unperceivable. Any difference in acceleration due to bicycle wheels that is claimed by your riding buddies is primarily due to cognitive dissonance, or the placebo effect (they paid a lot of money for the wheels so there must be some perceivable gain).

    this is said here;
    http://biketechreview.com/reviews/wheels/63-wheel-performance

    crikey
    Free Member

    TJ, there is no doubt that lighter wheels are noticeable, but this does not translate into a performance improvement. It’s a bit like changing the colour of your bike; everyone can tell, but it doesn’t go faster.

    skywalker
    Free Member

    Crikey, no offence mate, but no matter which way I explain it too you, you aren’t going to understand. You can’t even be bothered to read the wiki link correctly, instead you are just quoting out of context.

    There is no marketing in there whatsoever, just plain facts.

    Like I said before, http://www.analyticcycling.com/ have models and graphs proving you wrong.

    crikey
    Free Member

    …Anyway, enough.

    Our opinions differ, I’ll leave it there.

    amedias
    Free Member

    jeebus…

    this has been a fantastic read!

    FWIW, I would summarise as follows:

    Skywalker has quoted some mathematically correct equations which demonstrate (quite correctly), that in isolation, when considering moving a body around from one place to another, that includes a rotating mass, there is more kinetic energy involved.

    Crikey/Al have demonstrated that in the grand scheme of mountain biking over variable terrain in variable conditions the actual measurable difference is quite small. How small depends largely on all those other variable factors that have not been defined or described. In some circumstances lighter wheels may be of benefit, in others they are not so much, and in some cases a wheel with a little more mass can actually be a good thing.

    You have all demonstrated that arguing on the internet is pointless, but amusing 🙂

    ——————————————————————-

    In case anyone accuses me of not understanding or having read the articles etc. I have read all the links you guys posted, plus others, I have also conducted my own real world experiments, admittedly more for my own curiosity than to generate any usable data, and I have a masters degree in Physics, and I still wouldn’t say lighter wheels make you faster.

    crikey
    Free Member

    I like that summary!

    cynic-al
    Free Member

    Evening minnows, you’ll have to wait a little for more factual and well reasoned “big hitter” input…me phone’s running out of battery

    mdavids
    Free Member

    Right so, when I buy a new hope hoop wheelset should I go for crests or flows for general XC/trail centre riding?

    DuggieStyle
    Free Member

    Flows with dual ply tyres and DH tubes, you wont notice the difference 😆

    neninja
    Free Member

    I’ve been involved in testing on motorcycles previously. I can’t remember the exact figures but the difference between standard cast aluminium wheels vs carbon ones was striking – something like 1.5secs on a 1.10s lap. On a racing motorcycle that’s a massive difference.

    The bike accelerated quicker, stopped in less distance, was easier to turn at high speed and gave the improvement in lap times, plus the rider gets less fatigued due to less effort to turn the bike (a large amount of rider input is required to turn a motorcycle at high speed).

    It’s not just about the total wheel weight though but it’s moment of inertia. Regardless of total wheel weight, a wheel with a lower moment of inertia will require less force to accelerate and have reduced gyroscopic effect making it easier to turn. Generally this means a lighter rim and spokes (the hub weight has almost no effect).

    cynic-al
    Free Member

    POST-A-GEDDON

    neninja…interesting…cast alloys must weigh a ton tho, and the speeds, forces, gyroscopic effect are likely orders of magnitude higher than mtbs…where we are discussing 500g off a ~3.5kg wheelset, part of a 90kg rider & bike.

    skywalker – Member
    What they don’t take into account though is the effect lighter wheels have on suspension performance, handling and braking.

    None of which you have referenced any formulae or data for…so your only guessing.

    skywalker – Member
    Why do you think manufacturers try so hard to reduce the sprung and unsprung weight of downhill bikes? If you and Al were right, they would build heavier bikes to keep momentum, but like I said you are not looking at the whole picture.

    Your logic is crap, that would not follow from our argument, in fact in DH where there’s a fair bit of accelerating & change of direction, and races are very very tight, these factors may matter.

    Anyway back to your sacred article, here are the salient quotes about light wheels…

    In other words, a mass on the tire has twice the kinetic energy of a non-rotating mass on the bike. There is a kernel of truth in the old saying that “A pound off the wheels = 2 pounds off the frame.”[14]

    Another place where light wheels are claimed to have great advantage is in climbing. Though one may hear expressions such as “these wheels were worth 1–2 mph”, etc. The formula for power suggests that 1 lb saved is worth 0.06 mph (0.1 km/h) on a 7% grade, and even a 4 lb saving is worth only 0.25 mph (0.4 km/h) for a light rider. So, where is the big savings in wheel weight reduction coming from? One argument is that there is no such improvement; that it is “placebo effect”. But it has been proposed that the speed variation with each pedal stroke when riding up a hill explains such an advantage. However the energy of speed variation is conserved; during the power phase of pedaling the bike speeds up slightly, which stores KE, and in the “dead spot” at the top of the pedal stroke the bike slows down, which recovers that KE. Thus increased rotating mass may slightly reduce speed variations, but it does not add energy requirement beyond that of the same non-rotating mass.
    Lighter bikes are easier to get up hills, but the cost of “rotating mass” is only an issue during a rapid acceleration, and it is small even then.

    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.*below
    Another explanation, of course, may be marketing benefits associated with selling weight reductions.

    Many many people on here suffer from *above.

    I love how you say we don’t understand your argument. We understand it perfectly, and have showed that, whereas you’ve not even responded to points made by me 2 pages ago! If you had, you’d have some credibility.

    Anyway this is too easy…like eating minnows in a barrel. Night, hope you’re tucked in!

    skywalker
    Free Member

    Right so, when I buy a new hope hoop wheelset should I go for crests or flows for general XC/trail centre riding?

    It doesn’t matter mate. Buy the heaviest wheels and tires possible, it won’t make a blind bit of difference

    😆

    TandemJeremy
    Free Member

    Actually Al its all similar magnitude

    a couple of kilos off a wheel set that weighs a few kilos and a bike and rider weighing 200 kgs – thats the sort of range. speeds are higher yes but not orders of magnitude higher.

    so actually quite relevant to get some idea of the time / effort savings which in the case of the motorcycle a couple of %

    I would expect the motorcycle effects to be higher with the higher speeds but an mtb is accelerating for more of the time probably.

    so I would expect overall a similar magnitude of difference of a couple of %

    cynic-al
    Free Member

    ywalker – Member
    It doesn’t matter mate. Buy the heaviest wheels and tires possible, it won’t make a blind bit of difference

    LOL…as if I’ve said that…keep deflecting…

    TJ…speeds – 200mph vs 20mph…power is easily at least an order of magnitude higher.

    but an mtb is accelerating for more of the time probably.

    I doubt it…the race bike is pretty much accelerating all the time, bar when braking hard and briefly for corners? (and the losses are only that of rolling resistance and friction for the mtb as the mumentum is otherwise maintained)

    Northwind
    Full Member

    The steering difference with my Dymags on the motorbike (and binning a brake disk) was immense, to the extent I almost crashed first ride out. But that’s gyroscopic forces with a much heavier assembly spinning at much higher speed so really difficult to make any meaningful comparison. I can’t feel any steering difference going from my lightweight wheels and tyres on one bike to the dualplies and 721s on the other bike.

    A word on placebo effect… Don’t underestimate it. If your bike feels faster, there’s a good chance you’ll become faster.

    Still… There’s a whole industry of racers, and these days it’s a science as much as a sport. When you look at the lengths they took to lighten Steve Peat’s world champ winning bike, I think it makes sense to ask why they’d do that if it wasn’t effective- the risk they took there was huge, they lost strength, punctureproofing… And then look at every single race bike at an XC event, if there’s no meaningful difference shouldn’t at least some of those riders be on beefier rims?

    cynic-al
    Free Member

    A word on placebo effect… Don’t underestimate it. If your bike feels faster, there’s a good chance you’ll become faster.

    And I say it again to you, as I do to skywalker….evidence?

    Northwind
    Full Member

    You must be kidding? These guys might play your silly games…

    skywalker
    Free Member

    Where is your evidence Al? So far all you have done is disagree.

    TandemJeremy
    Free Member

    Yes al – you tell yourself you are always right so you don’t have to think critically. Your argument on this one is full of flaws but as usual its pointless to debate with you,

    Northwind – loosing a kilo off the front tyre on the tandem ( a very extreme case and obviously other effects such as profile as well) was an obvious difference to steering at speed.

    cynic-al
    Free Member

    skywalker – Member
    Where is your evidence Al? So far all you have done is disagree.

    No, that’s you.

    I’ve accepted much of the argument is unsupported by evidence on either side. You’ve not even commented on my 500gm = 20s on a 90min race or produced any mathematical analysis of your own.

    TJ – shame you have to reduce it to personalities so quickly, up to you, how you can say the speeds re similar is beyond me*. And I too see flaws in your arguments…your 1kg lighter front wheel…same tyre/pressure/terrain?
    the other factors would have too much influence for your judgement to be worthwhile IMO.

    And Northwind – without evidence it’s pure conjecture…as some of my points are…but at least I have some arguments/analysis to back them up.

    EDIT TJ didn’t say *!

    TandemJeremy
    Free Member

    Cynic al- shame you don’t want to think critically – two misquotes / falsification of what I said in one post. Nice

    loosing a kilo off the front tyre on the tandem ( a very extreme case and obviously other effects such as profile as well) was an obvious difference to steering at speed.

    Speeds are similar magnitude not similar speeds.

    cynic-al
    Free Member

    See my edits – apols for speed-reading.

    Night all, soft toys are waiting…

    nick1962
    Free Member

    I just put Crest stickers on my Flow rims and so everyone thinks that’s why I’m faster when in reality I am a cycling Ninja

    Northwind
    Full Member

    This thread really is the point where Al jumps a shark (on a homemade fatbike obviously). It’s hard to believe anyone has so much free time they’d choose to waste it like this… Ah well.

    bikewhisperer
    Free Member

    You’ve not even commented on my 500gm = 20s on a 90min race or produced any mathematical analysis of your own.

    I’d say that your analysis is very partial.. It doesn’t attempt to quantify the effects of unsuspended weight on rolling resistance. It’s valid on a smooth track, but not many mountain bike races are.

    Although I don’t pretend to know any maths to show the significance of the effects, I’d certainly say that the following points are true:

    1. Having less unsuspended weight (or less unsuspended inertial mass, as it’s spinning) will allow the suspension to react quicker to bumps.. So less deformation of the tyres and wheel, less energy transfered to the ground, and less rolling resistance… So less slowing down over bumpy ground.
    2. Having more reactive suspension (because of the above) will have the effect of sticking the tyres down better, giving the wheels greater grip on the corners.. So carrying more speed. After all, suspension is about traction, not comfort.

    These could each be equally as significant as the accelerative effect that you mention (well, actually they’re the same effect!) so if 20s became 60s over 90 minutes.. what then?

    Last thing..
    If the wheels are constructed the same, then the lighter ones will be less stiff.. So might deform more due to pedalling forces and losing energy that way. Most light wheels aren’t built like that though.

    Kevevs
    Free Member

    lose some weight. You’ll ride faster. oh, and ride more, further, faster. I think that’s it. and cut out the pies and beer. oh, and your expensive wheels will wear out. sorry it’s not about the wheels.

    cynic-al
    Free Member

    I’d say that your analysis is very partial.. It doesn’t attempt to quantify the effects of unsuspended weight on rolling resistance. It’s valid on a smooth track, but not many mountain bike races are.

    Why not look into the data on rolling resistance and see if it helps? Schwalbe published some research IIRC.

    Northwind…shame no one can match my big hit stamina or analytical skills….

    BruceWee
    Full Member

    One thing that is confusing me is the fact that everyone seems to be saying that they can tell when they are on a bike with heavier wheels but with some saying it makes no difference to speed while others are saying it does.

    I guess they best way to test this (since as far as I can tell there have been no tests done on technical off road trails) would be to fill the tyres with water for one run then do the same run without the water in the tyres but with an equivalent weight added to the frame taking care to keep weight distribution the same for both.

    Ideally the bikes and riders should be fitted with full data acquisition systems measuring heart rate, cadence, torque input, wheel speed, GPS speed, and suspension velocity.

    This test should be repeated using at least 10 different riders with five doing the increased wheel weight first and the others doing the increased frame weight first. The test should also be blind so the rider doesn’t know whether he or she is riding the bike with increased frame weight or increased wheel weight. Comments from riders should also be taken into account and all riders should have similar fitness and technical ability.

    Anyone out there doing a Masters degree in sport science or engineering and looking for a thesis?

    BruceWee
    Full Member

    Actually, my original thought when I decided to post was about the sprung weight vs unsprung weight. I’ve been thinking a lot lately about how important unsprung weight is for mountain biking. Obviously in motorsport it is very important since the majority of the suspension is provided by the shocks.

    In mountain biking you have at the most 8 inches of travel provided by the suspension plus 12 inches provided by your arms and legs effectively turning the entire bike into unsprung weight.

    I’ve had a look but I can’t find much information on this on the net, anyone read anything that talks about this?

    jameso
    Full Member

    What goes round in circles more easily, a light wheel or an internet argument?

    (Amedius, well said)

    jameso
    Full Member

    In mountain biking you have at the most 8 inches of travel provided by the suspension plus 12 inches provided by your arms and legs effectively turning the entire bike into unsprung weight.

    Fair point.. your body can’t react as fast over repeated impacts in the way a damper can, so the whole bike’s not really suspended in the same way. You want suspension to free your arms and legs to simply control / steer the bike, or pedal, more of the time. But you’re right that a lighter bike is easier to hop and float over the trail too, it is unsprung then. Certainly is if it’s a rigid bike.

    Lowering unsprung weight is probably more easy to show as a benefit than lowering wheel weight, as unlike the wheel weight point, it assumes the suspension is working ie you’re not on the lab-conditions smooth surface. But it assumes you already have dampers and pivots that are sensitive enough to react faster if the wheel and swingarm is lighter (ie Propedal would cancel out a lot of that I think)

    A low pressure tyre deforming over a rock should reduce momentum less than a damper allowing the wheel to move over the rock, and certainly has less reduction in momentum that the impact lifting the weight of (a rigid, high pressure tyred) bike and rider over the rock. This is why a heavy fat-bike tyre can have suprisingly low rolling resistance – in this area it has super-low unsuspended mass – but it won’t pedal up the hill so easily.

    This is why I think rolling resistance and grip / comfort are worth considering even at the expense of reduction in weight. There’s a balance point somewhere but I won’t pretend to understand the maths there.

    amedias
    Free Member

    oh my god, are you lot still at it?

    the thread that keeps on giving….

    bigsi
    Free Member

    I think its about time for………

    😆

    TandemJeremy
    Free Member

    two hundred!

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