Well, think about it this way.......
fasteddy001 said:
I found many answers at that link including the hub vs rim issue. Many post-ers seem to think wheels weigh vs frame weigh is a big difference, but of course everyone has there opinion. Some also think the issue is overblown, I guess it depends on the situation. In my world, my speed is constantly changing when in a race so I think it would make a big difference- I mean each person has to define what acceleration is. If your speed varying at all even by 1/4 to 1/2 mph, which mine is, you're constantly accelerating or decelerating. I think it may be a mistake to think of acceleration only in terms of what you do at a drag strip or waht happend at the start of a race. IN MTB world I think its any time your pace changes even by a minor degree
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Well, I think you had better think about it this way.......
Boj said the following....
Here are the actual numbers where a gram saved is worth this much on a particular part (and only for cases of acceleration):
hub 1.0007
spokes 1.2043
rim 1.7006
tube 1.8723
tire 1.8723
wheel overall
front 1.563
rear 1.467
Now, he is good on the math part......but as he said those number are for only those time of acceleration...
So look at your riding.. You think you are constantly going 1/4 or 1/2 mph faster or slower all the time..... But think about it. Do some real math. If you are even doing mini accelerations that also implys you are also doing mini decelerations and unless you are the most unusual rider, you are also having some time spent neither doing acceleration or deceleration. In the maximum case I doubt a rider is spending more than 1/3 of his time in acceleration, with another 1/3 in either deceleration or coasting and probably another riding at a steady state.. I think you would agree it would be almost impossible to get much beyond 33% in acceleration because you also must slow down or coast.....and if you take a good look at your riding on many flat sections you are doing neither.
So just using that 1/3+1/3+1/3 =1 type of riding you then will have to take Boj's figures and devide by 3 for the weight ratio to use in your decision making process.
Look at his figures for tubes, tires and rims and they go from 1.70 to 1 to 1.87 to 1 but only "during" acceleration. So if you are spending only 1/3 of your time in actual acceleration then you have to divide those figures by 3......ending up with about a range of 1.23 to 1 ....to 1.29 to1. Thus you are less than 1.3 to 1 under any circumstances.
Nowhere near the 2 to 1 or even 3 to 1 you often hear cited.
So maximum, the the 100 grams saved at the rim-tire-tube is equal to 130 grams at the hub...
AND, in actual riding under scientifically measured conditions, I seriously doubt it it that high. I think it would be almost impossible to be accelerating 33% of the time....certainly anything beyond that is simply impossible... The theoretical maximum I am thinking would be 50%....and that is if you are never riding at a steady pace but instead only accelerating and then decelerating or coasting.
Pay attention to how you really ride next time and I think you will see that even on lots of your climbs you speedo is just switching a tenth of a mph back and forth and much of that is just due to minor undulations in the terrain as well as a speedo that isn't precisely accurate... For all practical purposes going from 8.9 mph to 9.0 mph and back to 8.9 mph is not acceleration and hardly even counts as part of the 1/3 I am talking about. Even a little rock or rut can push the computer back and forth a tenth of a mph.
I stick with my orginal estimation that the difference between rim-tire weight versus hub weight is only about 1.1 to 1 ...or maximum 1.25 to 1........over a typical cross country course.....AND remembering that the grams involved are only a very tiny part of not only the bike weight, but an even smaller part of the entire rider-bike weight.
As I said, the rolling resistance of the tires probably is a 100 times more important consideration in final lap time.