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Calculating value of shaving off weight
The thread below on sprung/unsprung weight inspired me to calculate the
cost - and to speculate on the value - of my latest weigh saving investment. I thought I would share my results with you. After having to give up on the third mountain in the Ötztaler Radmarathon two weeks ago, I realized I had to loose a lot of weigh before my next attempt.So I bought new very slim spokes ( 2.0-1.5-2.0 mm) to replace the plain gauge (2.0) that the bike shop had put in, because they considered me a heavy rider . i.e. 86 kg = 187 lbs. But Jobst Brandt's great book on wheels has told me, that heavy riders don't need heavy spokes - just very tight spokes and strong rims. So that's what I got. The weight saved on the two wheels is 368 g.- and the price for the spokes & nipples is exactly 50 US $. This gives a price per saved kg of 136 $. Is it worth that money? The following considerations tell me it is: I figure, that if I want to make it over all four Alp mountains next year, I will have to loose 7 kg - going back to what I weighed, when I was 40, - gee! thats 15 years ago. Loosing 7 kg is worth 7*136 = 951 $ - and though that's a lot of money to me, it is also a lot of work to drop 7 kg of body weight and stay there. I mean, I do a LOT of cycling already. So would I be willing to pay almost a thousand dollars for a weight loss of 7 kg, that would last for - say 7 years? Yes, definately, I think it is more than fair - it is cheap, considering the effort of carrying that load up 5.500 meters in the Alps. So saving weight by putting in butted spokes IS good value for money. But I still need to find the limit for how much I would be willing pay? Chosing between two different Shimano derailleurs, 105 or Ultegra, the weigh difference is a mere 13 g and the prise difference is 14.29 $ - making the price of one saved kg: 1099 $. Or 7,700 $ for loosing 7 kg. At that prise, I would rather do the hard work or suffer the privations needed to loose 7 kg of body weight and keeping it down. Unfortunately I bought the Ultegra Group already. What a waste! So I look for my limit somwhere between those two exambles. I guess I would be willing to pay 50 $ pr month to be 7 kg. lighter without really trying (besides what I do allready) So if the weight saving parts lasts for 7 years, I guess 600 $ pr. kg saved weight is still a fair deal. Now I have the rule of thumb I need, when I consider buying lighter parts for my road racer: 60 cents per gram saved weight is my limit. Although I think, that's a lot of money to be willing to spend, and wouldn't telle my wife about it, there probably aren't many lighter parts available at that price for my 10 kg middle level road bike. Maybe a saddle, maybe shoes. But that will be it. Ivar of Denmark |
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#2
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On Thu, 16 Sep 2004 00:39:01 +0200, Ivar Hesselager wrote:
After having to give up on the third mountain in the Ötztaler Radmarathon two weeks ago, I realized I had to loose a lot of weigh before my next attempt.So I bought new very slim spokes ( 2.0-1.5-2.0 mm) to replace the plain gauge (2.0) that the bike shop had put in, because they considered me a heavy rider . i.e. 86 kg = 187 lbs. I _wish_ that were my weight. But Jobst Brandt's great book on wheels has told me, that heavy riders don't need heavy spokes - just very tight spokes and strong rims. So that's what I got. The weight saved on the two wheels is 368 g.- and the price for the spokes & nipples is exactly 50 US $. This gives a price per saved kg of 136 $. How do you compute that weight saving? Did you have steel rims previously? That is a huge difference for just changing spokes. OTOH, I don't see the advantage of using straight-gauge spokes. I claim there is no advantage in overall strength between staight-gauge and butted spokes. Conversely, I*would not use 2/1.5/2mm spokes, since that center section would be a RPITA in terms of wind-up. A more conservative 2/1.8/2 or 1.8/1.6/1.8 would give a more resiliant, and thus stronger wheel, without making it impossible to build. So saving weight by putting in butted spokes IS good value for money. No way are you saving 368 grams by switching spokes. For even 36-spoke wheels, that is supposedly a nearly 10g/spoke saving. DT reports that its 1.8/1.6/1.8 spokes weigh 311g for 64, and the 2.0/1.8/2.0 weigh 382g/64. Plain 2.0 weigh 444g/64. So, the difference between lighter than yours and the heaviest spokes in general use, is less than 150g. At that prise, I would rather do the hard work or suffer the privations needed to loose 7 kg of body weight and keeping it down. You're fussing about grams, versus dropping 7kg for "free". You know what is the best bet. -- David L. Johnson __o | Some people used to claim that, if enough monkeys sat in front _`\(,_ | of enough typewriters and typed long enough, eventually one of (_)/ (_) | them would reproduce the collected works of Shakespeare. The internet has proven this not to be the case. |
#3
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"Ivar Hesselager" wrote in message ...
The thread below on sprung/unsprung weight inspired me to calculate the cost - and to speculate on the value - of my latest weigh saving investment. I thought I would share my results with you. After having to give up on the third mountain in the Ötztaler Radmarathon two weeks ago, I realized I had to loose a lot of weigh before my next attempt.So I bought new very slim spokes ( 2.0-1.5-2.0 mm) to replace the plain gauge (2.0) that the bike shop had put in, because they considered me a heavy rider . i.e. 86 kg = 187 lbs. But Jobst Brandt's great book on wheels has told me, that heavy riders don't need heavy spokes - just very tight spokes and strong rims. So that's what I got. The weight saved on the two wheels is 368 g.- and the price for the spokes & nipples is exactly 50 US $. This gives a price per saved kg of 136 $. Is it worth that money? The following considerations tell me it is: I figure, that if I want to make it over all four Alp mountains next year, I will have to loose 7 kg - going back to what I weighed, when I was 40, - gee! thats 15 years ago. Loosing 7 kg is worth 7*136 = 951 $ - and though that's a lot of money to me, it is also a lot of work to drop 7 kg of body weight and stay there. I mean, I do a LOT of cycling already. So would I be willing to pay almost a thousand dollars for a weight loss of 7 kg, that would last for - say 7 years? Yes, definately, I think it is more than fair - it is cheap, considering the effort of carrying that load up 5.500 meters in the Alps. So saving weight by putting in butted spokes IS good value for money. But I still need to find the limit for how much I would be willing pay? Chosing between two different Shimano derailleurs, 105 or Ultegra, the weigh difference is a mere 13 g and the prise difference is 14.29 $ - making the price of one saved kg: 1099 $. Or 7,700 $ for loosing 7 kg. At that prise, I would rather do the hard work or suffer the privations needed to loose 7 kg of body weight and keeping it down. Unfortunately I bought the Ultegra Group already. What a waste! So I look for my limit somwhere between those two exambles. I guess I would be willing to pay 50 $ pr month to be 7 kg. lighter without really trying (besides what I do allready) So if the weight saving parts lasts for 7 years, I guess 600 $ pr. kg saved weight is still a fair deal. Now I have the rule of thumb I need, when I consider buying lighter parts for my road racer: 60 cents per gram saved weight is my limit. Although I think, that's a lot of money to be willing to spend, and wouldn't telle my wife about it, there probably aren't many lighter parts available at that price for my 10 kg middle level road bike. Maybe a saddle, maybe shoes. But that will be it. ROTFLMAO! Sorry, nothing personal. DR |
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So would I be willing to pay almost a thousand dollars for
a weight loss of 7 kg, that would last for - say 7 years? Yes, definately, I think it is more than fair - it is cheap, considering the effort of carrying that load up 5.500 meters in the Alps. Ivar, this is the stuff of a weight-loss product marketer's dream. -- "Bicycling is a healthy and manly pursuit with much to recommend it, and, unlike other foolish crazes, it has not died out." -- The Daily Telegraph (1877) |
#5
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"David L. Johnson" wrote How do you compute that weight saving? Did you have steel rims previously? That is a huge difference for just changing spokes. OTOH, I don't see the advantage of using straight-gauge spokes. I claim there is no advantage in overall strength between staight-gauge and butted spokes. Conversely, I would not use 2/1.5/2mm spokes, since that center section would be a RPITA in terms of wind-up. A more conservative 2/1.8/2 or 1.8/1.6/1.8 would give a more resiliant, and thus stronger wheel, without making it impossible to build. So saving weight by putting in butted spokes IS good value for money. No way are you saving 368 grams by switching spokes. For even 36-spoke wheels, that is supposedly a nearly 10g/spoke saving. DT reports that its 1.8/1.6/1.8 spokes weigh 311g for 64, and the 2.0/1.8/2.0 weigh 382g/64. Plain 2.0 weigh 444g/64. So, the difference between lighter than yours and the heaviest spokes in general use, is less than 150g. At that prise, I would rather do the hard work or suffer the privations needed to loose 7 kg of body weight and keeping it down. You're fussing about grams, versus dropping 7kg for "free". You know what is the best bet. You are right David, the wight saving can't be that much. I checked the figures I found on the www.sapim.be homepage, and I have to admit, I misinterprited it. The weight saving was only half i.e. 184 grams - making the price per saved kg twice as high: 272 $ per kg. I'm not proud of that mistake, and it is no longer cheep. But it is still a fair price for the weight saving, Chosing very slim spokes - 1. 5 mm - is logical, since thin spokes (as Jobst Brandt tells us) is not a problem for a 85 kg rider, as long as the wheel I build is real tight. I also e-mailed the manifacturer, Sapim in Belgium, and they said "no problem" wiht the slim spokes for a heavy rider. So I oiled the spokes and the nipples at every joint to ease the tightening, and the wheels are now so tight that I really must depend on the strength of the Mavic CPX 33 rim. So far it seems to work allright - and I count on that it will last for at least seven years. I still like the idea of relating the cost of weight savings to the suffering and privation of loosing the 7 kg of body weight necessary to cross the four mountains of the Ötztaler Radmarthonh. To evaluate it, you need to relate it to something, and I have a very concrete aim - and experience, that I can relate it to. The alternative to buying lighter bicylcle parts is dropping body weight, but I don't accept the idea of that being "free". It's a lot of effort and a lot of privation to a man, who is cycling a lot already. So to estimate, if buying lighter parts for my road racer is worht the money, I need to relatate it to 1) the impact on the mountain riding, that I aim at, and 2) to my perception of what my time and effort is worth in dollars. I will stick to a max of 600 $ pr. kg saved weight - still maiking the slim spokes a good investment - but not justifying Shimano Ultegra in stead of Shimano 105. This calculation will be a marketer's NIGHT MARE, since it shows, that it is a waste of money to buy the high class group - even for well to do riders that are willing to pay 600 $ to get rid of one kg. If I had made this calculation before, I would not have bought the Ultegra group for my road racer. I know that some will be rolling on the floor laughing of what I'm willing to spend, to cross those mountains. But very many bicycle enthuthiasts have been spending at whole lot more, never knowing how to evaluate if it was worth their money. Ivar of Demark |
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IMO, it is not the actual numbers that matter here--it is the kind of
thinking which can affect your behavior. What to take along and what to leave behind--how much water to carry--what to wear, etc. It points up the silliness of comparing the gram weight of two cyclometers, and then throwing in a few extra tools "just in case." |
#7
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"Leo Lichtman" wrote in message ...
IMO, it is not the actual numbers that matter here--it is the kind of thinking which can affect your behavior. What to take along and what to leave behind--how much water to carry--what to wear, etc. It points up the silliness of comparing the gram weight of two cyclometers, and then throwing in a few extra tools "just in case." And "Should I wear a 3/4 pound (340 g) helmet?" After all it's very rare that it is actually needed and you'll be SO much faster without it. DR |
#8
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