## Just how much difference does lighter wheels make?

ball bearing
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### Re: Just how much difference does lighter wheels make?

Philipthelam wrote:
The issue, I think, with most first hand experiences is that lighter wheels are often more expensive, higher end wheelsets. So while the lighter wheel may feel better than a heavier wheel it is not the result of weight but a variety of other factors such as stiffness, aerodynamics, better bearings etc.

Yes, exactly so. I do,however, believe that weight is a major factor when it comes to rider perceptions on how the wheels are responding to input.

ColinOldnCranky
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### Re: Just how much difference does lighter wheels make?

For the record, on a theoretical wheel where 100% of it's mass is at the outside of the rim, the linear inertia of it in motion is exactly the same as the rotational inertia. ie. In other words a kg saved at the rim is equivalent to saving two kgs on the frame or anywhere else that is just moving in a straight line.

It's been forty something years since I was an engineering student but anyone proficient in calculus can prove it themselves.
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### Re: Just how much difference does lighter wheels make?

My light shallow profile wheels feel much better than my heavy shallow profile wheels. Part of it is build quality, and I do believe there is a noticeable improvement in acceleration. As stated previously I have not noticed any dramatic improvement in climbing ability or in flat time segments. I am sure there is a benefit to climbing... but maybe not inertia. Dragging a kg less up a hill has gotta mean less energy being used.

I have never ridden aero wheels to compare, but I considered buying them but decided on light weight. My reasoning was that aero was mainly of benefit when solo riding and most of my bigger riding efforts are either climbing or riding in groups. I had made the assumption that when in a group and not leading, that any bike aero benefits would be significantly reduced as you are not in the wind. Is this a valid assumption? If I suck a wheel behind someone for an hour going 40kph, will aero wheels provide much/any benefit over non aero wheels? If the situation is such that I am battling to not get dropped off a group that includes accelerations out of corners and up climbs, am I better off with lighter wheels that enable me to catch up to the wheel I am sucking quicker to save energy, or aero wheels that may provide some small benefit the whole time? I reasoned that getting back into the group was of more value than small power savings once in the group out of the wind.

Also, in terms of overall aero benefit, are wheels the best money spent. If I have a non aero regular road bike with external cables and nothing specifically aero about it, how much different do other aero considerations such as TT helmet, tighter fitting clothers, internal cables etc compared to wheels. In my case I have nothing aero. Can I achieve a better aero benefit for less money by changing something else? Would wheels make up <5% of total aero drag? However the wheel weight is a significant % of total bike weight, so I can have a large percentage weight reduction (10+%) by going from heavy to light wheels.

BTW - I am no wheel sucker generally. I pull my turn. But the bigger the group, the higher percentage of time spent out of the wind, and I am wondering which is better for that... light or aero.

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### Re: Just how much difference does lighter wheels make?

Alex Simmons/RST
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### Re: Just how much difference does lighter wheels make?

ColinOldnCranky wrote:For the record, on a theoretical wheel where 100% of it's mass is at the outside of the rim, the linear inertia of it in motion is exactly the same as the rotational inertia. ie. In other words a kg saved at the rim is equivalent to saving two kgs on the frame or anywhere else that is just moving in a straight line.

It's been forty something years since I was an engineering student but anyone proficient in calculus can prove it themselves.

The moment of inertia is only a factor in rotational accelerations, and for bicycle wheels, is such a small factor as to be effectively insignificant.

here, brush up on your physics:
http://www.biketechreview.com/index.php ... erformance

Nobody
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### Re: Just how much difference does lighter wheels make?

thecaptn wrote:I've never had anything but mid range bikes and would appreciate some opinions
This might help.
http://www.biketechreview.com/index.php ... erformance
In summary, wheels account for almost 10% of the total power required to race your bike and the dominant factor in wheel performance is aerodynamics. Wheel mass is a second order effect (nearly 10 times less significant) and wheel inertia is a third order effect (nearly 100 times less significant). The best wheels in terms of performance are the ones that are lightweight, aerodynamic, don’t rub brake pads and are strong enough to get you to the finish line. The problem with these high performance wheels, though, is that they sacrifice on the other two key variables important in wheel selection: durability and price. High performance wheels are neither durable nor cheap. Nothing is ever easy, is it?

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### Re: Just how much difference does lighter wheels make?

Interesting to see some actual physics calculations. My conclusion from that is don't worry about it at all unless you're doing time trials and are worrying about the seconds. That is, if you want to upgrade just to have nice stuff then by all means do so, but don't kid yourself that it makes a measurable difference at all except in the most specific circumstance (ie. a TT).

Now don't even get me started on the people that think upgrading from 105 to Dura Ace will give you an extra 5km/h...

KL.
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### Re: Just how much difference does lighter wheels make?

Nobody wrote: In summary, wheels account for almost 10% of the total power required to race your bike and the dominant factor in wheel performance is aerodynamics. Wheel mass is a second order effect (nearly 10 times less significant) and wheel inertia is a third order effect (nearly 100 times less significant). The best wheels in terms of performance are the ones that are lightweight, aerodynamic, don’t rub brake pads and are strong enough to get you to the finish line. The problem with these high performance wheels, though, is that they sacrifice on the other two key variables important in wheel selection: durability and price. High performance wheels are neither durable nor cheap. Nothing is ever easy, is it?

Hi Nobody, good summary

AndrewW wrote: .. Now don't even get me started on the people that think upgrading from 105 to Dura Ace will give you an extra 5km/h...

Hi AndrewW, no, but compared to a bad choice, the right choice of wheels can
Light (< 1500g and maybe even <=1600g), aero rims and spokes, good lateral stiffness for your weight, good drive via spoke arrangement, and good hub qualities (such as Dura Ace, Record and others) are qualities that all need to be considered

thanks KL

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### Re: Just how much difference does lighter wheels make?

A related discussion in the retro section:

http://www.bicycles.net.au/forums/viewtopic.php?f=23&t=65061

ColinOldnCranky
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### Re: Just how much difference does lighter wheels make?

Alex Simmons/RST wrote:
ColinOldnCranky wrote:For the record, on a theoretical wheel where 100% of it's mass is at the outside of the rim, the linear inertia of it in motion is exactly the same as the rotational inertia. ie. In other words a kg saved at the rim is equivalent to saving two kgs on the frame or anywhere else that is just moving in a straight line.

It's been forty something years since I was an engineering student but anyone proficient in calculus can prove it themselves.

The moment of inertia is only a factor in rotational accelerations, and for bicycle wheels, is such a small factor as to be effectively insignificant.

here, brush up on your physics:
http://www.biketechreview.com/index.php ... erformance

I retire in a year or so and I have been thinking of enrolling in some maths units. In the time before the term "nerd" existed I really did enjoy maths. It has been lost in a career with little need for it outside of some not-very-sophisticated stats and business maths.

As to the authors conclusion:
So, what do all these numbers mean? It means that when evaluating wheel performance, wheel aerodynamics are the most important, distantly followed by wheel mass. Wheel inertia effects in all cases are so small that they are arguably insignificant.
It may be distanct but as to whether it is insignificant that is an opinion, no quantifiable. A lot of ridersconsider a kg on the frame as significant and spend squillions trying to rid themselves of it. So, yes, other factors may be greater. But a kg on the rims has double the effect of it beinglsewhere and if you asked the author if he would like a kg less on his frame then I suspect he would be willing to pay a significant amount to do so. And even if he isn't, many others are.

Therefore for many riders inertia of the wheel is not entirely a minimal issue. At least as much as the equivalent extra mass carried elswhere. (Note: My conclusions are not about acceleration against gravity, not climbing where a kg on the wheel is the same as on anywhere else.)

Yes, other factors are more significant, aerodynamcis for instance. But cycilsts still purse the benefits of reduced weight as it is still worth pursuing.

Interestingly and all from memory) the IOC (or cycling union or whoever) used to be very strict about team pursuit bikes having weight added to the rims. That outside weighting was seen to advantage less proficient (and tired less fit) riders that were drafting with wheels almost touching. That seemed to change at the US hosted LA84 Olympics when all sorts of rulings in favour of the lowly Yanks allowed them to race with closed in wheels - so getting past the weight loading rules as well as negating rules against aerodynamic spokes. Unfortunately the Aussies with their new plastic bikes were not allowed such favourable decisions. The totally unfavoured Yanks finished up dominating track for the two weeks after which the rest of the competition adopted the same technology.
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ball bearing
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### Re: Just how much difference does lighter wheels make?

ColinOldnCranky wrote:
Yes, other factors are more significant, aerodynamcis for instance. But cycilsts still purse the benefits of reduced weight as it is still worth pursuing.

Somehow I can't recall ever hearing anyone say they wish that their wheels were just a bit heavier.

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### Re: Just how much difference does lighter wheels make?

ColinOldnCranky wrote:It may be distanct but as to whether it is insignificant that is an opinion, no quantifiable.

It is precisely quantifiable, and is insignificant.

ColinOldnCranky wrote:A lot of ridersconsider a kg on the frame as significant and spend squillions trying to rid themselves of it. So, yes, other factors may be greater. But a kg on the rims has double the effect of it beinglsewhere and if you asked the author if he would like a kg less on his frame then I suspect he would be willing to pay a significant amount to do so. And even if he isn't, many others are.

Therefore for many riders inertia of the wheel is not entirely a minimal issue. At least as much as the equivalent extra mass carried elswhere. (Note: My conclusions are not about acceleration against gravity, not climbing where a kg on the wheel is the same as on anywhere else.)

What riders might believe and what's actually real are two different things. I go with the latter.

A kg on the rim doesn't have double the effect.

i. Acceleration rates in cycling are small.

ii. The difference in the actual moment of inertia of wheels of a variety of masses/types when compared to the total inertial load of the bike+rider system is very very small.

ColinOldnCranky wrote:Yes, other factors are more significant, aerodynamcis for instance. But cycilsts still purse the benefits of reduced weight as it is still worth pursuing.

No-one is saying not to pursue it, but for the majority of riding, if performance is the objective, then wheel aerodynamics trumps weight considerations by a large margin. For steep climbs then reduced weight is advantageous.

If you are not convinced about relative impacts of wheel aerodynamic and wheel weight during accelerations, see this example:
http://alex-cycle.blogspot.com.au/2013/ ... parts.html

ColinOldnCranky wrote:Interestingly and all from memory) the IOC (or cycling union or whoever) used to be very strict about team pursuit bikes having weight added to the rims. That outside weighting was seen to advantage less proficient (and tired less fit) riders that were drafting with wheels almost touching. That seemed to change at the US hosted LA84 Olympics when all sorts of rulings in favour of the lowly Yanks allowed them to race with closed in wheels - so getting past the weight loading rules as well as negating rules against aerodynamic spokes. Unfortunately the Aussies with their new plastic bikes were not allowed such favourable decisions. The totally unfavoured Yanks finished up dominating track for the two weeks after which the rest of the competition adopted the same technology.

The UCI have never required weight to be added to rims for team pursuit or otherwise. Disk wheels are solely an aerodynamic aid.

USA team pursuit performances in 1984 were aided by blood doping run by USAC coaching staff.

USA used a rear disk with a standard spoked low profile front wheel, and aerodynamic helmets.
Aussies had standard low profile spoked rims front and rear and helmets (not sure about aero design).

Neither team had plastic bikes, they were standard steel tubed frames. USA frames may have been alu but definitely not carbon. The bars on both team's bikes were "bullhorns". There were no aerodynamic bar extensions in those days.

You might be thinking of the 1996 Atlanta Games where Australia used the "superbike", complete with the awful steerer that was a 'mare to use.

Australia won the 1984 Team Pursuit gold medal in the ride off with the USA team, largely due to the US rider who pulled his foot at the start and so they only had 3 riders for the entire 4km.

Aussies time in the final was 4:25.99

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### Re: Just how much difference does lighter wheels make?

ball bearing wrote:
ColinOldnCranky wrote:
Yes, other factors are more significant, aerodynamcis for instance. But cycilsts still purse the benefits of reduced weight as it is still worth pursuing.

Somehow I can't recall ever hearing anyone say they wish that their wheels were just a bit heavier.

Yes, you are right - tyou won't see to many riders seeking to increase inertia or weight.

However increased inertia was a boon for team pursuit where you only had to accelerate that weight once, then it was maintaining velocity for a long as possible but also staying as close as possible to the wheel in front. That inertia meant that riders could draft closer for a given skill level. Small changes in a riders effort at a given moment could result in wheels coming together. the extra inertia dampens that so that it takes longer to happen. Rules were in place to stop teams from adding weight to introduce that inertia. AFAIK there may still be restrictions of a similar nature, notwithstanding the LA84 olympics.
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### Re: Just how much difference does lighter wheels make?

Poor quality video of the 1984 team pursuit is at

the gear looks to be as Alex says. Also you can see the US rider droping out right from the start.
The 1996 were not dissimilar Australian superbike

US Bike

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### Re: Just how much difference does lighter wheels make?

KL. wrote:
Nobody wrote: In summary, wheels account for almost 10% of the total power required to race your bike and the dominant factor in wheel performance is aerodynamics. Wheel mass is a second order effect (nearly 10 times less significant) and wheel inertia is a third order effect (nearly 100 times less significant). The best wheels in terms of performance are the ones that are lightweight, aerodynamic, don’t rub brake pads and are strong enough to get you to the finish line. The problem with these high performance wheels, though, is that they sacrifice on the other two key variables important in wheel selection: durability and price. High performance wheels are neither durable nor cheap. Nothing is ever easy, is it?

Hi Nobody, good summary
Hi KL, sorry but it wasn't mine but the end of the link I quoted. Also didn't realize that Alex had posted the same link a few hours before. I should have read more carefully.

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### Re: Just how much difference does lighter wheels make?

ColinOldnCranky wrote:
However increased inertia was a boon for team pursuit where you only had to accelerate that weight once, then it was maintaining velocity for a long as possible but also staying as close as possible to the wheel in front.

Never been on a track. I'm a road-warrior one-on-one type of rider - at least I used to be. Now, I have endless hill challenges.

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### Re: Just how much difference does lighter wheels make?

Currently running stock PR-2 on my Defy 1. I read they are 1900 gms overall. Do you guys think getting something sub 1500 gms will make a noticeable difference or improvement?

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### Re: Just how much difference does lighter wheels make?

ColinOldnCranky wrote:
ball bearing wrote:
ColinOldnCranky wrote:
Yes, other factors are more significant, aerodynamcis for instance. But cycilsts still purse the benefits of reduced weight as it is still worth pursuing.

Somehow I can't recall ever hearing anyone say they wish that their wheels were just a bit heavier.

Yes, you are right - tyou won't see to many riders seeking to increase inertia or weight.

However increased inertia was a boon for team pursuit where you only had to accelerate that weight once, then it was maintaining velocity for a long as possible but also staying as close as possible to the wheel in front. That inertia meant that riders could draft closer for a given skill level. Small changes in a riders effort at a given moment could result in wheels coming together. the extra inertia dampens that so that it takes longer to happen. Rules were in place to stop teams from adding weight to introduce that inertia. AFAIK there may still be restrictions of a similar nature, notwithstanding the LA84 olympics.

There's always one:
http://autobus.cyclingnews.com/news/?id=2005/jul05/jul19news6

In his attempt, Sosenka was using a 3.2 kg wheel and 190 mm cranks, with his bike weighing a total of 9.8 kg. The reason for the heavy wheel was that although it was harder to get up to speed, it was easy to maintain it.

I seem to recall that Moser's 1984 bike had extra weights incorporated into the rim of his revolutionary (pun intended) wheels.

However in a bunch race the difference of a wheel length in acceleration might make the difference between getting into the wake of a passing rider or not and the missed opportunity could cost the race.

I'm more interested in whether there is a benefit to aero wheels in dirty air.

I ride my retro style wheels and let the bloke in front worry about being aero.

Cheers,

Cameron

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### Re: Just how much difference does lighter wheels make?

ironhanglider wrote:However in a bunch race the difference of a wheel length in acceleration might make the difference between getting into the wake of a passing rider or not and the missed opportunity could cost the race.

And is precisely why aero matters more than weight, especially when the sprint starts from speed. Taking typical differences in weight and aerodynamics between a quality low profile spoked wheel and a quality aero wheel, the aero wheel will accelerate faster and provide greater speed for the power available.

ironhanglider wrote:I'm more interested in whether there is a benefit to aero wheels in dirty air.

Most definitely. Indeed not only in the single case acceleration, but in the sum total if you are able to get to the final stages of a race have done a lot less work, then the extra freshness is very important for your ability to sprint. Or if that's not your game, then your ability to generate, reach and remain with a race winning break.

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### Re: Just how much difference does lighter wheels make?

you guys make out as if you can't get aero wheels that are light.
yes, I'm an overweight weight weenie

Alex Simmons/RST
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### Re: Just how much difference does lighter wheels make?

pawnii wrote:you guys make out as if you can't get aero wheels that are light.

I don't think anyone has said that. Opening statement from my blog post linked earlier:

A perennial favourite argument on cycling forums is the cost-benefit of choosing a wheelset with superior aerodynamics vs a wheelset that is lighter (or an aero vs a lighter frame).

It is of course a false dichotomy that one must chose only one or the other. But that does not stop people having fun arguing the merits of each, or of holding onto beliefs/myths/folklore handed down through the generations.

The issue is what do you choose when your budget is limited, because light and aero and sufficiently durable and strong for racing = expensive.

Alex Simmons/RST
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### Re: Just how much difference does lighter wheels make?

On on the subject of what people should choose to race on - my simultaneously serious and tongue in cheek answer is "race what you can afford to crash".

Alex Simmons/RST
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### Re: Just how much difference does lighter wheels make?

Just dragging up an older thread as I did an update on my post about wheel weight vs aero and modelling acceleration scenarios.

This time I used realistic power profile for a standing start acceleration and for a sprint starting from speed. I also added a scenario of a hot dog crit turn at bottom of a hill.

The sum of the parts II

Pretty much the same conclusion as before (unsurprisingly). Wheel aero trumps wheel weight, unless your racing consists of sprints from very low speeds lasting only a handful of seconds, or riding up very steep gradients.

And before anyone goes on about ignoring other factors involved with wheel choice, please read the item and the earlier one where I go through this.

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### Re: Just how much difference does lighter wheels make?

I dont know if people are aware of reddit, but a physicist and and avid cyclist threw in his 2c one day about the rotational mass of rims, an interesting read.