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Dead weight v/s rotating weight

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Dead weight v/s rotating weight

Old 04-17-03, 08:47 PM
  #26  
danr
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Thanks for the replies. I definitely learned something here.

Originally, I thought wheel weight was critical. After reading posted links and finding a little info on my own, I learned that wheel weight and aerodynamics do not matter as much as I thought they did.

Once again, it definitely matters if you're a racer, where every little bit counts. However, for my purposes of solo riding and occasional group riding, I feel better about sticking to my $170 wheelset.
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Old 09-01-05, 05:06 AM
  #27  
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This is obviously a very old topic, but since I am fairly new to the sport of cycling (mountain biking) - it is something to look at.

I understand all the arguments, for and against the idea that ligther wheels makes a difference. It is also understood that acceleration is where rotational weight has the biggest influence.

Still I want to add the following, in mountain biking, the only constant thing is change. So, you are acceleraing and decelerating all the time, the weight of the wheels in that case must make a difference - the harder it is to accelerate the rotation of the wheel, the more enery is required. That implies that your legs must provide more.

What I am saying is: assuming that lighter wheels will accelerate better when the same force is applied. If you do a 40km race once, with heavy wheels and once with lighter wheels you should be able to do the race faster with the lighter wheels. SO, to say that lighter wheels will not really make is difference is NOT true.
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Old 09-02-05, 05:53 AM
  #28  
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And since we are looking at old threads.....

Change is the constant in road riding too. You just don't always notice that you are changing.
Every time there is an outside influence on your wheels, eg. a bump in the road, the lighter the wheel is, the intertia will resist the change less. Energy from the bump will be transferred into the frame as you'd expect and from there into you. But you are better able to absorb that energy. The bike can only dampen it or transmit it. If it's being dampenend, who knows where it's going to?
IMO, a lighter wheelset is more responsive and easier to ride than a heavy one.
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Old 11-03-08, 02:39 PM
  #29  
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As the friction between road and wheel is dependent on total downward force on the road, a lighter frame, wheel, or rider definitely helps whatever be the condition. But whether it is relatively significant or not is the question.
For normal biking for limited period, other factors are more important lke riding comfort, finish & color, tyre pressure, bearing, etc., mass reduction may not be that much affordable as they use costly superior material mostly.
For racing in stadium, on custom-built tracks, everything is important that reduces friction like light frame, well designed frames, low friction bearings, aerodynamic helmets and everything, low weight wheels and spoke design, body-hugging suit of smooth material, etc.
For some cases like cross-country racing or such, a rugged frame and special tyre, etc. is more important. Air resistance and mass reduction are not so much important in this case, I feel.
I think the distribution of mass over the frame is also important in case of balance and performance, not only the mass. But again, in high speed with a lighter frame and wheel, u have to have the right technique to ride.
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Old 11-04-08, 04:32 PM
  #30  
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The last time I read through a thread like this, everyone seemed to agree that rotating mass on the outside of the wheel was twice as important as mass on the frame. Strange how now lots of people are saying 3 times as important...the twice as important theory was that the weight traveled twice as far (1x horizontally, 1x up and down with the wheel) which made a certain amount of sense to me.

Every time there's a thread like this, someone writes a post about how rotational mass "doesn't matter" which is think is absurd - obviously something that you're pushing forward + up and down is going to take more work to move than something that you're just pushing forward.

That being said, it's all about a cost/performance balance. The high end Mavic Ksyrium ES wheelset that came with my bike costs about $1,000 and is roughly 1500 grams (so I've read) for both wheels. A set of Mavic Open Pro wheels, which everyone seems to recommend on the bike forums, costs about $300 for a wheelset and weighs about 2000 grams for the entire wheelset. That's 500 grams difference.

So let's be optimistic about rotational weight and say that it matters 3 times as much as non-rotational weight. According to google's unit conversion tool, 500 grams is rougly 1.1 lbs, and 3x500 grams = 1500 grams, and 1500 grams is roughly 3.3 lbs. So the question is - is it worth it paying an extra $700, which is over 300% more, to lose 3.3 lbs off your bike?

As everyone has said, unless you're racing or doing a lot of riding with people with really high end bikes (just to even things out for you), probably not. On the other hand, maybe you're Donald Trump and $700 is pocket-change for you, in which case spending the money is just not a big deal. :-)
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Old 11-08-08, 11:53 AM
  #31  
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I won't bother with physics, but the 32mm tires I just got on my 48x16 motobecane messenger are a hell of a lot harder to turn.

On the other hand, when I commute on my 18 pound fuji ... I FLY!!
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