niterider Posted February 21, 2008 Share poena...just using this as an example....if this would help you I will change it....nice long hill (5km)....light bike maybe 7sec to 10sec........as to 1min to 2min to what people expect a light bike should do....so there is adiff but not a lot. just love it when people get so technical! No problemo. My point is that most people over-estimate the effect of weight-savings, when they'd be far better off investing in some deep sections to get more aero. Link to comment Share on other sites More sharing options...
fandacious Posted February 21, 2008 Share No problemo. My point is that most people over-estimate the effect of weight-savings' date=' when they'd be far better off investing in some deep sections to get more aero. [/quote'] They'd be even better off actually training on that hill 4 times a week insted of sitting here fighting about weight vs aero vs carbon fibre. look at mampara's signature Link to comment Share on other sites More sharing options...
niterider Posted February 21, 2008 Share They'd be even better off actually training on that hill 4 times a week insted of sitting here fighting about weight vs aero vs carbon fibre. look at mampara's signature Eggzacktly Link to comment Share on other sites More sharing options...
carlo_sg Posted February 21, 2008 Share http://img210.imageshack.us/img210/1368/49957262my4cs1.jpg SILENCE, I KILL YOU!!! Link to comment Share on other sites More sharing options...
The_Break Posted February 21, 2008 Share See you boys and girls been thrashing it out. I like it!!! Ok, Craig, you are right, I knew that but few people do. Reciprocating parts use twice as much energy to keep travelling at a constant speed due to the energy it takes to keep it moving in a straight line as well as the energy it takes to rotate it. Will check out the equation tomorrow in one of my books. Ok, all in all you have gotten nearly the same answer I did. Aero is nearly always better as this is the greatest components of force most of the time. When it comes to weight, which does make a big enough difference for those 2kg to be enough for you to get dropped from the group, it is best to take weight off of rotating components rather than non-rotating. Stiffness is important because it makes your pedal to wheel efficiency better and makes for better handling and rolling resistance should be reduced by better tyres, bearings and a clean chain. So to answer the original question, a frame is too light, when your bike weighs 6.8kg and you can still find the money and reciprocating parts that will make it even lighter. Now, where did I put that Vumaquad BB tool?.......... Link to comment Share on other sites More sharing options...
Wolweseun Posted February 22, 2008 Share mmmm So what you are saying is that the perfect bike will weigh 6.8kg be aerodynamic as possible have the lightest most aero wheels and lightest crank and pedals as possible. "Some people just dont get it" Then I am afraid you can not upgrade your frame there are no options Zipp CrankSpeedplay pedalsKCNC BrakesSL-C2008-02-22 00:51:32 Link to comment Share on other sites More sharing options...
Christie Posted February 22, 2008 Share Er, energy only more when accelerating heavier parts. On a road bike, the % of time spent accelerating is small, compared to total ride time. So saving weight on rotating parts does not win you much. Ons a road bike, weight is weight, it does not matter where you put it. Link to comment Share on other sites More sharing options...
The_Break Posted February 22, 2008 Share Hi Christie You are right and you are not right. Rotating parts are always accelerating as they accelerate in order to change direction as they rotate if that makes sense. Force = mass * acceleration and hence you need to keep applying a force in order to keep the mass rotating. You are right in that the rotating part is not speeding up though, but parts are changing direction and thus accelerating in order to do this. Linear motion has an energy of E = 1/2m *v^2. Rotating motion has a similar equation I can't remember. Will have a look for it. The Vuma quads are sweet though hey. Already got myself the Look Keo Ti 95g. They are nice as their cleats pedal combined weight is I think a bit lower than that of the sppedplay pedals. Link to comment Share on other sites More sharing options...
Gumpole Posted February 22, 2008 Share Please' date=' please, please while we are on the topic of light frames - can someone tell me: I ride a Trek WSD Aluminium frame. I weigh 53kg and go better up the hills than down, understandably. How much difference would it make to my cycling if I got hold of a Solis carbon frame considering my weight. Could I really be blown over by JHB wind? Currently my Treki with all the components weighs about 10kg or more. [/quote'] lets say that helmet, shoes, water bottles etc etc all weigh 4kg + 53kg + 10kg bike = 67kg total. Weight of old frame is 1.4kg - medium alu frameWeight of old frame is 1.0kg - lightweight carbon frame so 67kg vs 66.6kg, on a STEEP hill (for you that is, lets say 15km/h, could be any gradient) (67/66.6) *15km/h = 15.1km/h - ie after riding this STEEP 15km long Grand Tour Hill for an hour you will have gained 100m...not much, on flatter gradients this figure will reduce drastically. So maybe for 99% of hills in SA, the advantage of upgrading a Trek 1000 to a R20,000 superlight frame will gain you less than making sure that you get to the bottom of the hill at the front of the group!!! Link to comment Share on other sites More sharing options...
greatwhite Posted February 22, 2008 Share Hi Christie You are right and you are not right. Rotating parts are always accelerating as they accelerate in order to change direction as they rotate if that makes sense. Force = mass * acceleration and hence you need to keep applying a force in order to keep the mass rotating. You are right in that the rotating part is not speeding up though' date=' but parts are changing direction and thus accelerating in order to do this. Linear motion has an energy of E = 1/2m *v^2. Rotating motion has a similar equation I can't remember. Will have a look for it. [/quote'] As long as velocity is constant, rotating mass (wheels, cranks etc) has no more effect than static mass (frame etc) - its ONLY when you accelerate that you get an advantage in lighter rotating mass. On a bike, this relates almost exclusively to the rims, tyres and tube because the have the largest velocity changes AND the largest radius of gyration. The change of direction you refer to in actually does not apply as acceleration in this discussion. Link to comment Share on other sites More sharing options...
fandacious Posted February 22, 2008 Share So maybe for 99% of hills in SA' date=' the advantage of upgrading a Trek 1000 to a R20,000 superlight frame will gain you less than making sure that you get to the bottom of the hill at the front of the group!!![/quote'] Except that a Solis frame doesnt cost 20k... I paid 7k for mine.. and it weighs in at exactly 1kg, incl fork... Link to comment Share on other sites More sharing options...
NotSoBigBen Posted February 22, 2008 Share You can never be too light or to wealthy - Oh no sorry a different discussion with my wife last night ........... Link to comment Share on other sites More sharing options...
Gumpole Posted February 22, 2008 Share So maybe for 99% of hills in SA' date=' the advantage of upgrading a Trek 1000 to a R20,000 superlight frame will gain you less than making sure that you get to the bottom of the hill at the front of the group!!![/quote'] Except that a Solis frame doesnt cost 20k... I paid 7k for mine.. and it weighs in at exactly 1kg, incl fork... Ok so you only wasted 7k, The 1000g doesn't include the fork, else it is the lightest frame in the world.(seriously, I think it is a nice frame though) the other BIGGER cycling weight myth is that losing body weight is good for performance!! ie, Big Joe weighed 85kg, did a 4 hour argus, trained for a year, now weighs 80kg, did a 3 hr argus... so 5kg drop in weight saved him an hour - haha Link to comment Share on other sites More sharing options...
Christie Posted February 22, 2008 Share You are right and you are not right......... Trust me on this one. Rotating mass = negligable saving. This point has been extesively debated. If you do the math right' date=' that is the answer you get. Best let sleeping dog lie, if Johan Bornman gets on you case, HE will kill you (Achmed the terrorist [in the pic carlo sq posted'] has no chance) ..........The Vuma quads are sweet though hey. Already got myself the Look Keo Ti 95g. They are nice as their cleats pedal combined weight is I think a bit lower than that of the sppedplay pedals. As MWNN would say, them Vumaquads = sweet pumpkin Agree on the Keos, pedal+cleat are lighter than speedplay Zero ti pedal+cleats, but not lighter than the new Speedplay nanograms (R4900 per set)Christie2008-02-22 04:12:18 Link to comment Share on other sites More sharing options...
FlyingCheetah Posted February 22, 2008 Share Train with added weights on your bike. Take them off when you have a race. See, it's easy as pie! Link to comment Share on other sites More sharing options...
GreyOwl Posted February 22, 2008 Share To be honest, I have never been one to go nuts over a light bike. Its all good and well that the bike is teetering on the verge of the weight limit...but will it make it to the finish? You guys all go on about how your Cervelo is a balls hair heavier than the weight limit, and how its just like the pro's bikes...but when you are riding in "A"group, through to "ZZ" you do not have a back vehicle behind you, and in my honest opinion your more likely to pick up problems with those super bikes. Spinnekop and his mates can pull it off, due to their low body weights,and support on the road. But for the rest I would say just get a decent bike, and put on good wheels...forget about the weight limit. Coz thats the bike that will get you to the finish quickest. Carlos_I hope to god you rode that moron off?! Link to comment Share on other sites More sharing options...
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