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How does a lighter wheel increase performance?

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How does a lighter wheel increase performance?

Old 08-29-06, 09:02 AM
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noahjwhite
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How does a lighter wheel increase performance?

Quick question? A lighter wheel should decrease the amount of effort it takes to spin the wheel... correct? So this would obviously be beneficial during sprints ect... but would a lighter wheelset really make that much of a difference once already in motion? Say... over the coarse of a non-stop 50 mile run?
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Old 08-29-06, 09:12 AM
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You are constantly accelerating the bike as there is always friction and wind resistance slowing you down so it is always a benefit over a heavier wheel of the same design. The issue comes when you are looking at a slightly heavier but more aero wheel. Since aero drag is such a significant effect in acceleration the more aero wheel will be a greater benefit...but if you can get a light AND aero wheel then you are in buisness.
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Old 08-29-06, 09:24 AM
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Aerodynamics is much more important than weight on fast flat courses. If there are long slow climbs, then weight becomes more important.
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Old 08-29-06, 12:24 PM
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Lighter wheels help not just in overall weight, but in rotational weight. Lighter wheels have less rotational weight, which gives you more performance "bang for your weight buck" than weight savings anywhere else on the bike. Yes, losing body weight is important, etc.....but for bike weight, lighter wheels help a fair amount.
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Old 08-30-06, 01:29 AM
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lighter wheels are also better handling wheels, this is due the the gyro effect, less weight means less of this gyro effect and this means easier to steer.
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Old 08-30-06, 03:12 AM
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^^^ This one I honestly haven't noticed.

The increase in effort to steer is neglible, but the change in rotaional weight in a wheel when climbing a steep hill is somewhat noticable.
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Old 08-30-06, 05:29 AM
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Originally Posted by Grasschopper
The issue comes when you are looking at a slightly heavier but more aero wheel. Since aero drag is such a significant effect in acceleration the more aero wheel will be a greater benefit...but if you can get a light AND aero wheel then you are in buisness.
Yup... rotational weight is pretty trivial even in sprints... reasonable improvements in aero drag or Crr have a greater benefit. In all other conditions rotational weight is no different than weight anywhere else.
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Old 08-30-06, 05:47 AM
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How important is strength for a sprinter. In time trialling you are simply spinning up once then maintaining the rotations so strength is not a big priority. Sprinters hammer down on the cranks, twist the bars, jig around for position so there are a lot of lateral forces on the wheels.
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Old 08-30-06, 06:04 AM
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Once you drop all the coin on a new set of lightweight wheels, you are then determined to get your money's worth out of them, so you go out and ride more. Also, you may feel that you are unworthy to ride said wheelset, causing you to push yourself to ride harder. The combination of these two factors makes you ride much faster.

The same works for expensive frames, groups, and whole bikes. It is in fact the best way to become a highly motivated, skilled, and in-shape rider. If it does not work for you, then there is always ebay.
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Old 08-30-06, 06:14 AM
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Originally Posted by jamiewilson3
Once you drop all the coin on a new set of lightweight wheels, you are then determined to get your money's worth out of them, so you go out and ride more. Also, you may feel that you are unworthy to ride said wheelset, causing you to push yourself to ride harder. The combination of these two factors makes you ride much faster.

The same works for expensive frames, groups, and whole bikes. It is in fact the best way to become a highly motivated, skilled, and in-shape rider. If it does not work for you, then there is always ebay.
This is the best advice given in this thread. The search function here is temporarily disabled for now but this has been discussed many times. There's a lot of really good information available on this subject, and also a lot of misleading and non-factual as well. Do a google search and you should come up with some of the studies/data.

The bottom line is weight only matters on climbing and the impact is rather small. There are lots of factors involved, but they all are small and tend tyo cancel each other out. However aero is something to consider and is an important factor in almost all conditions.
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Old 08-30-06, 09:03 AM
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Originally Posted by drdhsimon
Lighter wheels help not just in overall weight, but in rotational weight. Lighter wheels have less rotational weight, which gives you more performance "bang for your weight buck" than weight savings anywhere else on the bike. Yes, losing body weight is important, etc.....but for bike weight, lighter wheels help a fair amount.
The "bang" you get for your buck is still so so small. Try a true double-blind test sometime (the guy swapping wheels doesn't talk to you, and you don't get to look at them). You will NOT notice a difference.

I know a guy at a shop who does a blind test with customers. He lets them ride with one of two identical pairs of large water bottles, one pair is full of water, and the other pair is empty. He's never had a customer who could tell which bottles were on the bike while pedalling seated. This is true of everyone from grandmas on cruisers to Cat 2 racers on carbon frames with full race components. Granted, water bottles aren't rotating weight, but they are a lot more weight than different wheel variances.

I have a heavy-ish pair of 36H Deep Vs on Ultegra hubs that I ride every day. I swapped out for a week with some American Classic Sprint 350s (among the absolute lightest aluminum clinchers made). I couldn't feel a difference on hills, sprints, or intervals. I saw no performance change at all on known courses with consistent efforts. None. They are round, just like the Deep Vs.
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Old 08-30-06, 09:18 AM
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I can definately feel the difference when accellerating up hills with ligher rims, especially when you switch from 2000 to 1500 gram wheels. The difference may be less noticeable when you become a stronger rider.
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Old 08-30-06, 11:52 AM
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Originally Posted by rruff
Yup... rotational weight is pretty trivial even in sprints... reasonable improvements in aero drag or Crr have a greater benefit. In all other conditions rotational weight is no different than weight anywhere else.
agreeamundo!!

I suspect the difference people feel with their "better/lighter" wheels is just smoother hubs and/or more rigidity. Hub quality is underrated. Even for repeated accelerations, stiffness is more importatnt than light weight

I'm not giving up until this rotational weight myth dies.

this is one of the fastest wheels available because it's stiff and obviously aero in most conditions, and guess what; it's heavy. Even Mavic's (no doubt) underestimated weight for one wheel is 1285g


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Old 08-30-06, 12:28 PM
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In order to understand the forces at play here you have to understand the concept of "angular momentum". It's a little complicated, and requires a little bit of advanced math, but Wikipedia has a good explanation: https://en.wikipedia.org/wiki/Angular_momentum

The short answer is that it does require more force to spin something in a circle than it does to move it in a striaght line at the same velocity. And, when friction is present, more force is required to keep something spinning in a circle as opposed to keeping it moving in a straight line.

So you would see a greater benifit by reducing the weight of your tires as opposed to the weight of anything else on your bike which doesn't spin. To understand how much of an advantage you'd get, and whether or not it's noticable, you'd have to work through the equations on the page linked above, which I'm not willing to do right now.
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Old 08-30-06, 12:43 PM
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Originally Posted by gmiller
friction.
but a bike wheel stuck firmly to the road by 170+ pounds of bike and rider isn't a freely spinning flywheel or gyrscope!! AAAAAGh!!! All this flywheel and gyroscope stuff, which has just come out of some year 9 physics text has very little to do with a fat guy riding a bike

FRICTION, FRICTION, FRCITION!!

The friction on the bike tyre is ENORMOUS!! The only way a bike wheel would suddenly 'spin up' faster with 100g less external weight, would be if there was no friction at all on the tyre, like, lifting the rear wheel off the ground.

The main force that has to be overcome when a rider accelerates is the 200 odd pounds of person and bike, which is SO much bigger than a couple of hundred grams on a tyre, especially when the wheel is spinning so slowly, anyway

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Old 08-30-06, 01:06 PM
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Originally Posted by Grasschopper
You are constantly accelerating the bike as there is always friction and wind resistance slowing you down so it is always a benefit over a heavier wheel of the same design. The issue comes when you are looking at a slightly heavier but more aero wheel. Since aero drag is such a significant effect in acceleration the more aero wheel will be a greater benefit...but if you can get a light AND aero wheel then you are in buisness.
And for that you need $$$.
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Old 08-30-06, 04:52 PM
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Originally Posted by SSC
I can definately feel the difference when accellerating up hills with ligher rims, especially when you switch from 2000 to 1500 gram wheels.
You could "feel" those full water bottles, too... that is because you are swinging your bike back and forth. Your actual speed difference will be ~0.4% due to that wheel change... plus the placebo effect of course.

Originally Posted by gmiller
To understand how much of an advantage you'd get, and whether or not it's noticable, you'd have to work through the equations on the page linked above, which I'm not willing to do right now.
I have, for the worst case scenario of a full power sprint at the end of a race... and it's trivial. Small improvements in Crr or aero drag have a much bigger effect even then.
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Old 08-30-06, 04:56 PM
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For what it's worth, I just slapped on a set of tires that weigh 200 grams more than my old set, and I can't tell the difference.
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Old 08-30-06, 04:58 PM
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I beleive its as much of a mental thing as anything else. With that being said, I really love my SL's.
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Old 08-30-06, 05:07 PM
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Originally Posted by waterrockets
The "bang" you get for your buck is still so so small. Try a true double-blind test sometime (the guy swapping wheels doesn't talk to you, and you don't get to look at them). You will NOT notice a difference.
Yeah, you can spend more on a new set of wheels than you did on the bike and it'd give minimal performance difference. Yes, if you shave off 1500-2000gm from your stock wheelset by going to tubulars, lightweight tyres and hubs, you can measure some speed-increases. But these would be a matter of seconds on a 20K hillclimb of 40K flat-TT. Yes, if you're a pro and your paycheck depends upon placing high in the rankings, yes, expensive lightweight wheels will give you a slight edge, a couple seconds here and there. But if you're a weekend-warrior riding less than 250-miles/week and don't race, it won't make one bit of difference to you.
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Old 08-30-06, 05:20 PM
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I just built up a set of wheels weighing over a pound less than my previous set, and I climbed most hills in a smaller cog or two, but I think this is mostly due to what jamiewilson3 said (mental) and very little to do with actual weight impact. Of course, now that I built these wheels up, I moved to a flatter area and only clib on my longer rides where I get out of this huge valley.
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Old 08-30-06, 05:26 PM
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Originally Posted by Patriot
^^^ This one I honestly haven't noticed.

The increase in effort to steer is neglible, but the change in rotaional weight in a wheel when climbing a steep hill is somewhat noticable.

I agree, and the reason lies mostly in the fact that we dont really "steer" to make turns. Most of the turning is accomplished by leaning, there is very little "steering" movement of the wheel.
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Old 08-30-06, 05:39 PM
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Several have commented here that perhaps an aero rim might be of more benefit after all is said and done, even if it weighs a hundred or two grams more. When the term "aero" is used here, are we referring to a typical aero rim type wheel or, one of the full aero type wheels as in the picture posted by "531Aussie"?
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Old 08-30-06, 05:45 PM
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I think in this case anything with a V shape and somewhere around 30mm or deeper will suffice. But I know some hardcore people will mention that those aren't "aero wheels"
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Old 08-30-06, 07:04 PM
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Originally Posted by urbanknight
I think in this case anything with a V shape and somewhere around 30mm or deeper will suffice. But I know some hardcore people will mention that those aren't "aero wheels"

Some people have qouted anything under 38mm is not giving an aero advantage

A good web site to read about aero wheels is the zipp site.. but then again they are trying to sell you their wheels!

https://www.zipp.com/Technology/Aerod...7/Default.aspx

Here is another resource OP
https://www.ultracycling.com/equipment/wheels.html
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