how much a diff is 300grams in wheelsets



Sorry alienator, but 53-11 is mostly correct on this one, I think his verbiage was a little too strong and it may seem counter intuitive, but he is right. If you analyze the total sum of the forces involved (especially when it is you that condescendingly suggest a better grasp of physics :rolleyes: ), you will see that while reducing wheel weight (esp at the rims) will reduce the wheels inertia measurably, but the net effect is not very large at all in the whole system. That said, reducing wheel weight will have a SLIGHTY greater effect than reducing static weight on the bike and or rider(for acceleration) as Smartie pointed out, but a generic ratio is not possible because of all the variables involved. The "50% reduction of wheel weight gives .03% more power", is probably a good rough approximation but it will change depending on speed (aero drag on the rider, etc.), elevation gain/loss, and so on. It is certainly much closer than the 5:1 that those with only a high school grasp of physics subscribe to :D.

If you really want a wheel that accelerates much better, stiffness is at least as important as weight, but in terms of speed, unless you are doing a Mtn time trial, aero has much better benefits. As evidenced by the popularity of the heavy, Aero, and very stiff Cosmic Carbones in the Pro Peloton.

Call it placebo effect or whatever, but don't dismiss the psychological aspects. Seriously, if someone truly believes that their new lightweight wheels are making them faster, they probably will, and conversely if they think their heavy wheels are holding them back, they will. I know I have done many technically worthless upgrades that at the time really did make me faster because I believed they would. Sometimes ignorance truly is bliss.
 
jrstang473 said:
Im thinking os switching out my bontrager race lite wheels for a set of am 420's or some mavic ssc sl's.My race lite's are around 1750 grams and the wheels mentioned are 1500grams and below.What im trying to ponder is if i will be able to see or feel a diffrence in riding between the wheels mentioned above and the ones i already have. I weigh 160lbs and my bike is at 16.2 lbs now.I hasve alot of big hills in my area that i try to ride up alot.

The answer to your question is that there is virtually no measureable difference between the two wheels, however if you got the money to burn, and are itching for an upgrade go for it. If you get a pair of 404 Tubs, you will have something more aero (will make a small difference), and lighter (won't make much of a difference, but even knowing that, I still think lighter is always better, at least for bragging rights/bling factor).
 
As Chevy Chase once said (in a very funny SNL skit portraying then President Ford in a debate), "It was my understanding there would be no math at this debate."

Hey guys, as my very wise LBS owner once said to me, "Instead of worrying about a few grams on your bike, have a salad, go to the gym, and ride a few extra miles." Adding, "If you really want to go faster, take a few pounds off of your rear-end and see how much faster you climb and sprint. You can't buy being in better shape. You have to work hard for that."

Amen brother.

P.S. I've ridden Ksyrium elites for years. They do "feel" like I'm climbinb faster and stronger but on the flats I prefer my old Mavic Ceramics on Dura-Ace hubs. I really do think they roll faster. Sometimes, it's all a matter of perception I guess.
 
chrispopovic said:
Hey guys, as my very wise LBS owner once said to me, "Instead of worrying about a few grams on your bike, have a salad, go to the gym, and ride a few extra miles." Adding, "If you really want to go faster, take a few pounds off of your rear-end and see how much faster you climb and sprint. You can't buy being in better shape. You have to work hard for that."

We've all heard this before, and it's obviously VERY true, but what do we do once we get down to a good weight? Do we then buy the light wheels? If so, what's the difference between getting them then or getting them now? :p

By the way, I think that light wheels are overrated; give me stiff wheels any day
 
chrispopovic said:
P.S. I've ridden Ksyrium elites for years. They do "feel" like I'm climbinb faster and stronger but on the flats I prefer my old Mavic Ceramics on Dura-Ace hubs. I really do think they roll faster. Sometimes, it's all a matter of perception I guess.
Those kysriums may feel faster than regular Open pros, but it won't be becasue the rim weighs less. In fact the Kysrium Elite rim is heavier than an Open Pro by a good margin.

Even though the Ksyriums are heavier in the rim than an OPen Pro they are superior aerodymnamically. That's what makes the difference (aerodynamics)- not the weight so much

In fact the trend in wheels (except on really rough surfaces) is to use a really stiff rim (usually heavier all things equal) with a lower spoke count. The weight savings you see on the spec sheet is mostly from the use of really light hubsets with these wheels and also in part to the lower spoke count.

So next time you say 1 gram off the wheel is worth 5 off the frame take a few things into consideration

1. Where is the weight reduction of this wheelset coming from?

2. How imprtant is reducing weight at the rim/tire in the grand scheme of things. That article points out that wheel inertia accounts for approximately .5% of the power requiremnets. To make any real dents in this rim/tire weight you need to switch to tubular rim/tire set-up and then you're lucky to get a 20% improvement.
 
Adam-from-SLO said:
Try riding some heavy wheels(wire beaded tires, 25C + heavier rims + 32 or 36 14g. spokes / brass nipples ), maybe a tire liner, etc. .......... then go to a lighter tire/ kevlar bead , alloy nips, butted spokes 28F, 32R , lighter rims , ................. and you will notice a chunk of difference.

The hell you will. I think I made just about the biggest change in wheel weight possible, and I can assue you there is no magically huge difference. It's a little faster, which I felt most in sudden acceleration up a short incline. The bike didn't ride like it was 10kg lighter :).

My old wheelset had 1.5kg of tire, 0.4kg of tube, and 3.2kg of rim, spoke and hub. My new wheelset Bontrager racelites, with 1.4kg of (UST) tire, and about 1.7kg of rim, spoke, and hub. The total drop was about 2kg.
 
53-11 said:
Those kysriums may feel faster than regular Open pros, but it won't be becasue the rim weighs less. In fact the Kysrium Elite rim is heavier than an Open Pro by a good margin.

Even though the Ksyriums are heavier in the rim than an OPen Pro they are superior aerodymnamically. That's what makes the difference (aerodynamics)- not the weight so much.

I have had the Elites and I have had custom built Open Pro's now and the only difference that I noticed was in my wallet with the Elites costing about $200 more. Maybe If I had more HP, the aerodynamics would come into play but....
 
wilmar13 said:
Sorry alienator, but 53-11 is mostly correct on this one, I think his verbiage was a little too strong and it may seem counter intuitive, but he is right. If you analyze the total sum of the forces involved (especially when it is you that condescendingly suggest a better grasp of physics :rolleyes: ), you will see that while reducing wheel weight (esp at the rims) will reduce the wheels inertia measurably, but the net effect is not very large at all in the whole system. That said, reducing wheel weight will have a SLIGHTY greater effect than reducing static weight on the bike and or rider(for acceleration) as Smartie pointed out, but a generic ratio is not possible because of all the variables involved. The "50% reduction of wheel weight gives .03% more power", is probably a good rough approximation but it will change depending on speed (aero drag on the rider, etc.), elevation gain/loss, and so on. It is certainly much closer than the 5:1 that those with only a high school grasp of physics subscribe to :D.

If you really want a wheel that accelerates much better, stiffness is at least as important as weight, but in terms of speed, unless you are doing a Mtn time trial, aero has much better benefits. As evidenced by the popularity of the heavy, Aero, and very stiff Cosmic Carbones in the Pro Peloton.

Call it placebo effect or whatever, but don't dismiss the psychological aspects. Seriously, if someone truly believes that their new lightweight wheels are making them faster, they probably will, and conversely if they think their heavy wheels are holding them back, they will. I know I have done many technically worthless upgrades that at the time really did make me faster because I believed they would. Sometimes ignorance truly is bliss.

People are obviously reading more into what I wrote than was there. I never claimed that rotational momentum changes were huge. I will claim that they can be noticeable. First of all, when climbing most people aren't going "fast", as implied by someone else. It's a given that when on the flats, the change in angular momentum for a wheel is not as large as it can be on a climb. Second, on a climb the angular momentum of a wheel is not constant, especially as the rider slows. So with every turn of the cranks, the wheels have to be accelerated again. When you jump out of the saddle, on a climb, there will be an even larger acceleration. These accelerations can be noticeable to the rider.

There, also, assumptions that are made being in error by some around here. If you want to assume that power output is constant over some interval....well, that's a dodgy assumption to make for most riders. Others use an argument that a person's overall "time" won't change much. So what? What's being ignored are several considerations: 1. A person does not have an infinite energy supply; therefore, people do not perform at a constant power output. 2. No machine is perfectly efficient, and with the human body this is definitely the case. Each person has an optimum efficiency at which they do work. Complicating this is the fact that as fatigue sets in, blood glucose levels change, and so on...as these things happen a person's efficiency changes. But the situation is even more complicated than that. A person's efficiency can go back up.....throw back some GU.....start metabolizing glycogen stores....etc. So what all of this means is that at different times in a ride some change in angular momentum might be even more noticeable.

Mentioning that mass reduced in a wheel is much less than the rest of the mass in the bike/rider system is really pointless. Is the implication supposed to be that a human can't resolve any change in momentum smaller than the impulse needed to accelerate the whole system?

Plugging numbers in to a website calculator does not provide an accurate answer if you don't plug in the right numbers or if the calculator does not use a complete model. Such a calculator can make general conclusions, but those general conclusions don't resolve finer details....like what a given rider will experience or sense.

I'll not make claims about what the minimal acceleration is that person can sense. I'll bet, though, that it's alot smaller than people think. EX: a person going into space for the first time on a visit to the ISS might get nauseous (pretty common for astronauts). The consensus right now on the cause of that nausea is the difference in the acceleration of gravity at the person's feet and at their head. For a 6 ft astronaut in the ISS at nominal orbit radius, the difference in the accel. of gravity between his feet and head is a whopping 0.00008%. Now someone will say that astronaut won't feel the accleration difference, and their right. BUT what this shows is that the body is pretty pretty damned sensitive sensor. It'd be reasonable to say that hypothesize that a person could actually feel an acceleration change on the order of 0.01 or 0.001%.

Raw numbers, as given by others here, mean nothing without knowing the assumptions made, the initial conditions of the system, and what the unknowns are.
 
alienator said:
It'd be reasonable to say that hypothesize that a person could actually feel an acceleration change on the order of 0.01 or 0.001%.
LOL.....Are you serious?

a 1/100th to 1/1000th of a percent?

We are talking bicycle wheels here not astronaunts floating in space.
 
53-11 said:
LOL.....Are you serious?

a 1/100th to 1/1000th of a percent?

We are talking bicycle wheels here not astronaunts floating in space.

Acceleration comes in all kinds of forms, not necessarily just those that make you go forward.

Perhaps you're in love with numbers or are afraid of something violating some deeply held/revered sense of scale that you have. Fact is, you, as well as the website you referenced, explicitly and/or implicitly claimed that certain bicycle component accelerations were too small to be detected. This was done as if there is some law that dictates what limits there are to human sensory perception. Without doubt, there are limits to perception. However, there is evidence that those limits are very low (i.e., they allow finer sensory discretion) or at least lower than people might guess. As I said before, I am not claiming to put a lower limit on the ability of a person to detect small accelerations. I posted the space example as an example at the extreme end of acceleration sensing, an example of the body to sense some very discrete accelerations. Of course it's not like bicycle wheels or the like, and of course it's not relevant in magnitude. It just shows that the truth lies somewhere between the minute and what people blindly claim is impossible.

Maybe you should try trotting out some nerve sensivity numbers instead of numbers from a very general model from some third party website.

It'd be stupid to say that someone could absolutely feel the acceleration difference between a wheel that is 300 g lighter in the rim than another. It's just as stupid to say that someone can absolutely NOT feel the difference. I don't know what the real answer, but I am not so presumptious, so stupid, or so completely lacking in critical or scientific thought skills to proclaim something impossible.
 
alienator said:
Acceleration comes in all kinds of forms, not necessarily just those that make you go forward.

Perhaps you're in love with numbers or are afraid of something violating some deeply held/revered sense of scale that you have. Fact is, you, as well as the website you referenced, explicitly and/or implicitly claimed that certain bicycle component accelerations were too small to be detected. This was done as if there is some law that dictates what limits there are to human sensory perception. Without doubt, there are limits to perception. However, there is evidence that those limits are very low (i.e., they allow finer sensory discretion) or at least lower than people might guess. As I said before, I am not claiming to put a lower limit on the ability of a person to detect small accelerations. I posted the space example as an example at the extreme end of acceleration sensing, an example of the body to sense some very discrete accelerations. Of course it's not like bicycle wheels or the like, and of course it's not relevant in magnitude. It just shows that the truth lies somewhere between the minute and what people blindly claim is impossible.

Maybe you should try trotting out some nerve sensivity numbers instead of numbers from a very general model from some third party website.

It'd be stupid to say that someone could absolutely feel the acceleration difference between a wheel that is 300 g lighter in the rim than another. It's just as stupid to say that someone can absolutely NOT feel the difference. I don't know what the real answer, but I am not so presumptious, so stupid, or so completely lacking in critical or scientific thought skills to proclaim something impossible.
You need to get out of the box and start thinking big picture.

You are so hopelessly bogged down with worrying about tiny little accelerations that don't amount to a hill of beans.

Even if I could feel .001 % why should I even care? Give me a heavier stiff rim (damn the extra 40 grams of wheel inertia) so I can lower my spoke count anyday. In fact that's what manufacturers do with most high end wheels . Unless you are climbing at some rediculously low speed constantly (what race course is always go up at a huge % grade?) the aerodynamics will play a greater role.

Even in a very low climbing gear 39-27 you are still going 10mph at 90 rpm. THe wind resistance at the spokes is going to be 25% of what it is at 20 mph, but it will still amount to drag. Your better off with a deeper profile rim so the velocity of the spokes out at the ends of the rotating mass is lower. You are also better off lowering the spoke no. to reduce drag further.

I haven't plugged in any numbers, but's the overall concept, "the big picture" you fail to grasp. You off thinking about astronaunts floating in space when you should be thinking of how a bicycle wheel really acts.
 
53-11 said:
You need to get out of the box and start thinking big picture.

You are so hopelessly bogged down with worrying about tiny little accelerations that don't amount to a hill of beans.

And you've assumed too much about what I've written. It was put forward by you and others that it is nigh impossible for someone to sense the difference in acceleration between wheels with different moments of inertia. I only refuted that point. Nowhere did I say that this sensation was critical. Nowhere did I allege that there weren't more important factors to consider. No, you presumed that is what I said. You said I need to think of the big picture, but I only said that the big picture is not necessarily the complete picture.

There is alot of good advice, at times, doled out in this forum, but unfortunately alot of it is mixed up with some really stupid assertions that have no basis in fact. One of the most popular topics about which people make stupid assertions is the effects on power/speed/time and what people can feel/do. These assertions are seemingly made on the basis of whatever the writer feels is right or makes them feel comfortable, not on the basis of empirical data or studied of any sort. Often, painfully simple models are used to support such claims, and said models are usually constructed so that they can't even resolve whether or not the claim can be addressed. When you do a simplified analysis....i.e. you hold power constant, your answer has to note that. You can't make other claims that exceed the initial conditions of a simplified model. And if you're going to use a "calculator" to buttress an argument and make claims, then you better know how the "calculator" defines and constrains the model. That is the least that any engineer or scientist that was worth a $hit would do. Hell, most freshman in college can do that much.

You really are not in a position to determine whether or not someone needs to think of the bigger picture, especially when you are assuming things that have not been stated.
 
alienator said:
There is alot of good advice, at times, doled out in this forum, but unfortunately alot mixed up with some really stupid assertions that have no basis in fact.
Case in point - 1 gram off the wheelset is worth 5 grams off the frame.

This is complete and utter nonsense. You can't compare wheelsets to eachother based on total weight because the weight distrubution (rim/spokes/hubs) is going to be dramatically different from wheelset to wheelset.

Factors that affect weight distrubution and "wheel inertia"

1. Weight of rim
2. No of spokes and weight of each spokes
3. Weight of Hubs (really light hubs like DT 240s can make a wheelset with heavy spokes and heavy rims look light becasue they weigh so much less than factory hubs. I think a set of DT 240's can shave off 350 grams compared to a factory set of hubs in some cases).
 
53-11 said:
Case in point - 1 gram off the wheelset is worth 5 grams off the frame.

This is complete and utter nonsense. You can't compare wheelsets to eachother based on total weight becasuse the weight distrubution (rim/spokes/hubs) is going to be different from wheelset to wheelset.

Besides manufacturers today have realized wheel inertia is less important than other factors.

You're right, that's a silly claim. There is no argument there.

And as far as wheels go, again, you're right I reference the moments of inertia for a given body (in this case a wheel). Weight w.r.t. a rotating body is irrelevant--in terms of energy, momentum, etc-- unless you know how the weight is distributed across that body...and that is why I referenced moments of inertia.
 
Removing mass off the wheels of a bike on its own may have little effect on the performance improvement on a bike and would best be taken as part of an overall package to give minute performance gains over the whole bike.

Granted, the average (and possible well above average) cyclist may not feel the gain but in a sport where track racing is timed to the thousandth of a second these gains are vital to translating the riders power into forward thrust.
 
The funny part about reading this whole thread is that if 53-11 would not have tried to understate the value of lighter wheels in order to prove his point that it makes little to no difference, and alienator wouldn't have acted like such a pompous ass, there wouldn't be much to debate. I agree that if you just use a calculator without understanding the fundamentals behind the calculator it can lead you to make false assumptions, but even if you understand the fundamentals, misapplication can result in the same. The whole tiny accelerations while climbing, made a lot of sense to me when I first heard it, but the fact is when you look at the whole system it is again meaningless (or even non-existent).

Last time I went for a ride, my wheels stayed connected to my bike the whole time, so again it doesn't matter whether we are talking about climbing or track racing the % of total energy exerted required by the wheels to accelerate is the same (not quite, but lets keep it simple and neglect wind resistance, etc.). Now out of that tiny % that we have already all agreed upon roughly, what about the effect of those acceleration peaks you put down while climbing... well how about we take a rider with a terrible pedal stroke to be worst case scenario and use low gearing to really exacerbate the peaks, say a 39-25 (1.56 O/A ratio) and he is only able to maintain a cadence of 60 (roughly 7mph if using a 700x23). He only puts down power for only 120deg of crank rotation, each leg (yes the amount will change dynamically through the stroke, but again keep it simple). So he is "accelerating" (everything, not just his wheels) for .52 sec, followed by .17 sec of deceleration... .52, .17, and so on the whole way up the hill. Yes many many many accelerations, very true. The problem with this is that unless you make the grade really freaking steep you are not really decelerating (in terms of speed) in the .17 seconds where you "coasted" .3M or about a foot, therefore the only acceleration you are performing is to maintain the climb against G (and nothing changes in your speed, which is the only place those very tiny accelerations would have any effect on wheel inertia). If you are ambitious do the calculations for yourself (I am a big enough dork I did, and I will try to find the spreadsheet I used...IIRC it was well over 30% grade where these accelerations were even measurable, if you use a faster cadence, bigger gears, and a more accurate pedal model you can forget about justifying those lighter wheels analytically anyhow). Before I get flamed by someone for a lack of mathematical rigor of this post, it is like Zeno's paradox interpretation between a mathematician and an engineer: There is a beautiful woman is on the other side of the room from you, and to get to her you must advance only 1/2 the current distance at a time, the mathematician will argue you will never reach her, the engineer will say he can get close enough (ladies just reverse the genders and this will be a PC post, or modify the genders to match your preferences, whatever they may be).



Yes theoretically there is energy to be saved (and you will save a small amount for sure), but the amount has been WAY overstated by marketing types and bike rag journalists. If you want to argue about how big the infinitesimal savings is, go for it, it does exist. Me I will just wish that I didn't know just how small the difference was so I wasn't upset by how flimsy my light 303's tubulars are (relative to my "super heavy" Nucleons, that are about 300 grams more but stiffer and with better bearings).

Buy lighter wheels for the bling factor, motivation to train harder, a reward to yourself, just because you are bored with your ride and need some more spice, etc., but don't buy them to shave 3 minutes off your club's hill climb time trial (unless of course you REALLY believe they will save 3 minutes, in which case you may indeed have some psychosomatic improvements, again ignorance is bliss).
 
Adam-from-SLO said:
Its a free country, believe what you want to believe. Try riding some heavy wheels(wire beaded tires, 25C + heavier rims + 32 or 36 14g. spokes / brass nipples ), maybe a tire liner, etc. .......... then go to a lighter tire/ kevlar bead , alloy nips, butted spokes 28F, 32R , lighter rims , ................. and you will notice a chunk of difference.

Sorry bud, too many variables involved with this comparison to have any value. The one thing that stands out, is the tire. You upgrade from a crappy tire to an awesome one and you will see a huge diffence, with all other things remaining the same. Tires are one of the most overlooked performance upgrades out there.
 
wilmar13 said:
Now out of that tiny % that we have already all agreed upon roughly, what about the effect of those acceleration peaks you put down while climbing... well how about we take a rider with a terrible pedal stroke to be worst case scenario and use low gearing to really exacerbate the peaks, say a 39-25 (1.56 O/A ratio) and he is only able to maintain a cadence of 60 (roughly 7mph if using a 700x23). He only puts down power for only 120deg of crank rotation, each leg (yes the amount will change dynamically through the stroke, but again keep it simple). So he is "accelerating" (everything, not just his wheels) for .52 sec, followed by .17 sec of deceleration... .52, .17, and so on the whole way up the hill. Yes many many many accelerations, very true. The problem with this is that unless you make the grade really freaking steep you are not really decelerating (in terms of speed) in the .17 seconds where you "coasted" .3M or about a foot, therefore the only acceleration you are performing is to maintain the climb against G (and nothing changes in your speed, which is the only place those very tiny accelerations would have any effect on wheel inertia). If you are ambitious do the calculations for yourself (I am a big enough dork I did, and I will try to find the spreadsheet I used...IIRC it was well over 30% grade where these accelerations were even measurable, if you use a faster cadence, bigger gears, and a more accurate pedal model you can forget about justifying those lighter wheels analytically anyhow).
I always figured that a small increases in weight at the rim would only come into play at extremely steep grades myself. Like you said, it depends on how choppy the pedal stroke is too.
 
wilmar13 said:
The funny part about reading this whole thread is that if 53-11 would not have tried to understate the value of lighter wheels in order to prove his point that it makes little to no difference, and alienator wouldn't have acted like such a pompous ass, there wouldn't be much to debate.

Wow. If you think I was being a pompous ass then either you were reading too much into what I wrote, you have a bias against certain verbage, or you really don't like anyone that enjoys discussing the scientific end of things.
 
alienator said:
Wow. If you think I was being a pompous ass then either you were reading too much into what I wrote, you have a bias against certain verbage, or you really don't like anyone that enjoys discussing the scientific end of things.

Well quotes like:
I suppose you'll find comfort in the Flat Earth Society. You obviously don't have a grasp of physics. Try to follow along.....

and a few other phases came across as a little harsh especially when the guy was more or less correct and you were not. I understand maybe you were kidding, and when I said "pompous ass", I wasn't trying to insult you either(although in retrospect that was harsh of me as well), more to describe the strong condescention that was coming across to another cyclist for no reason (well OK the clutch comment was out there a little but still...). Trust me I have issues with condescention too, but it isn't something that is condusive to having a good discussion forum.

Scientific discussions are great, just not while insulting others, if you read my posts I doubt you would judge me as someone with disdain for contemplating, arguing, or debating the theoretical or practical aspects of anything. I am still waiting for someone to pipe in on the effects of ambient temperature and power potential, but no one is biting if you would like to change subjects...
 

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