Wheel upgrade - a question

Robi45

Below is a quesiton I originally posted to the Cyclling Plus office in response to their recent test on mid spec wheels. Any thoughts/guidance gratefully received.

I read with interest the mid-price wheel test in the latest issue. I was also "glad" to read in your report that the Bontrager;s you tested while decent enough wheels were sluggish climbers. This was a key point for me; that is exactly what I have discovered with the Bontrager Race wheels on my Trek 2.5, which otherwise is a bike I like very much. The bike feels cultured and comfortable and the H2 fit is perfect. It's super stable at the front end and a great descender but hit the first hill and its like cycling through treacle....It's becoming a bit of an issue on an otherwise lovely bike. Kind of curious given the Race wheel spec and R3 tyres.

The Wilier I also ride weighs in best part of a kilo heaveir overall and while is generally harsher ride with lighter Fulcrum 5 wheels which I fitted it is much more willing on the hills. It could be my legs of course, but even allowing for that the difference is significant.

So my question is how is that a bike which is clearly heavier overall can feel so much more lively when climing? Is it all down to rotating mass or are there other factors at play?

smidsy

Yes to rotating mass, spins up easier, holds speed longer/decelerates less quickly and requires less effort to maintain existing speed.

The difference is further pronounced with rotating mass as it effectively works double to that of fixed mass, giving a greater feeling of benefit per gramme lost.

MattC59

smidsy wrote:

Yes to rotating mass, spins up easier, holds speed longer/decelerates less quickly and requires less effort to maintain existing speed.
The difference is further pronounced with rotating mass as it effectively works double to that of fixed mass, giving a greater feeling of benefit per gramme lost.

Not quite sure whether that's correct.
Yes a wheel with a lighter rim, therefore lower rotating mass, will spin up to speed quicker, but it won't necessarily hold speed longer. A heavier rim, once up to speed will hold speed longer, due to the flywheel effect. More mass = more inertia, whether it's accellerating or decellerating.

Wirral_paul

On an uphill, you're effectively accelerating all the time, just to maintain speed (due to the battle against gravity which slows you down). Lighter rims are easier to accelerate and so it stands to reason that a lighter rim helps on the climbs (ignoring all other factors like lateral stiffness etc)

thescouselander

MattC59 wrote:

smidsy wrote:

Yes to rotating mass, spins up easier, holds speed longer/decelerates less quickly and requires less effort to maintain existing speed.
The difference is further pronounced with rotating mass as it effectively works double to that of fixed mass, giving a greater feeling of benefit per gramme lost.

Not quite sure whether that's correct.
Yes a wheel with a lighter rim, therefore lower rotating mass, will spin up to speed quicker, but it won't necessarily hold speed longer. A heavier rim, once up to speed will hold speed longer, due to the flywheel effect. More mass = more inertia, whether it's accellerating or decellerating.

^This.

Also on the acceleration point - although your speed will oscillate somewhat on a climb heaver wheels will smooth this out due to the flywheel effect. Any energy put into the spinning the wheels up in the power part of the stroke will be extracted again as power drops off.

The lighter bike overall should be the best at climbing. Could it be the brakes on the Trek are binding slightly on the climbs due to a bit of wheel flex?

smidsy

thescouselander wrote:

although your speed will oscillate somewhat on a climb heaver wheels will smooth this out due to the flywheel effect. Any energy put into the spinning the wheels up in the power part of the stroke will be extracted again as power drops off.

The lighter bike overall should be the best at climbing. Could it be the brakes on the Trek are binding slightly on the climbs due to a bit of wheel flex?

These two things seem to be at odds with one another.

Wirral_paul

smidsy wrote:

thescouselander wrote:

although your speed will oscillate somewhat on a climb heaver wheels will smooth this out due to the flywheel effect. Any energy put into the spinning the wheels up in the power part of the stroke will be extracted again as power drops off.

The lighter bike overall should be the best at climbing. Could it be the brakes on the Trek are binding slightly on the climbs due to a bit of wheel flex?

These two things seem to be at odds with one another.

Indeed, and by the logic applied, every pro would fit heavier rims for the mountains. Strangely, they dont - they fit lighter rims!! The UCI minimum weight limit still applies so it isnt to lighten the bike overall.

A heavier rim will have the flywheel effect yes, and so great for typical time trials once up to speed where its more important to maintain high speed than to sprint out of corners (and climb big hills) but counter-productive on a climb - where lighter rims are the norm.

thescouselander

smidsy wrote:

thescouselander wrote:

although your speed will oscillate somewhat on a climb heaver wheels will smooth this out due to the flywheel effect. Any energy put into the spinning the wheels up in the power part of the stroke will be extracted again as power drops off.

The lighter bike overall should be the best at climbing. Could it be the brakes on the Trek are binding slightly on the climbs due to a bit of wheel flex?

These two things seem to be at odds with one another.

I don't think they are - the flywheel effects of the wheel rims are pretty negligible in theory anyway (although plenty will say they can feel the difference). I was just pointing out that the idea that heaver rims will require more power to keep spinning is false as any energy put in will always come out again at some point.

At the end of the day the amount of energy required to get up the hill is proportional to the all up weight of the bike and rider so the lightest setup should require the least energy - thats why lighter rims are better going up hill.

unixnerd

On an uphill, you're effectively accelerating all the time, just to maintain speed (due to the battle against gravity which slows you down). Lighter rims are easier to accelerate and so it stands to reason that a lighter rim helps on the climbs (ignoring all other factors like lateral stiffness etc)

+1. As someone who climbs things like Cairngorm mountain's ski road on a regular basis I can assure you that light wheels and tyres have far more than a placebo effect.

On the flat if you put a bit more effort in it translates into extra speed far more easily with lighter wheels. This was very noticeable going from a 1900g to a 1500g set.

P_Tucker

unixnerd wrote:

On an uphill, you're effectively accelerating all the time, just to maintain speed (due to the battle against gravity which slows you down). Lighter rims are easier to accelerate and so it stands to reason that a lighter rim helps on the climbs (ignoring all other factors like lateral stiffness etc)

+1. As someone who climbs things like Cairngorm mountain's ski road on a regular basis I can assure you that light wheels and tyres have far more than a placebo effect.

On the flat if you put a bit more effort in it translates into extra speed far more easily with lighter wheels. This was very noticeable going from a 1900g to a 1500g set.

Why rely on anecdotes? Some nice people with A-levels in physics have done the sums - from Wikipedia

Advantages of light wheels

The advantage of light bikes, and particularly light wheels, from a KE standpoint is that KE only comes into play when speed changes, and there are certainly two cases where lighter wheels should have an advantage: sprints, and corner jumps in a criterium.[15]

In a 250 m sprint from 36 to 47 km/h to (22 to 29 mph), a 90 kg bike/rider with 1.75 kg of rims/tires/spokes increases KE by 6,360 joules (6.4 kilocalories burned). Shaving 500 g from the rims/tires/spokes reduces this KE by 35 joules (1 kilocalorie = 1.163 watt-hour). The impact of this weight saving on speed or distance is rather difficult to calculate, and requires assumptions about rider power output and sprint distance. The Analytic Cycling web site allows this calculation, and gives a time/distance advantage of 0.16 s/188 cm for a sprinter who shaves 500 g off their wheels. If that weight went to make an aero wheel that was worth 0.03 mph (0.05 km/h) at 25 mph (40 km/h), the weight savings would be canceled by the aerodynamic advantage. For reference, the best aero bicycle wheels are worth about 0.4 mph (0.6 km/h) at 25, and so in this sprint would handily beat a set of wheels weighing 500 g less.

In a criterium race, a rider is often jumping out of every corner. If the rider has to brake entering each corner (no coasting to slow down), then the KE that is added in each jump is wasted as heat in braking. For a flat crit at 40 km/h, 1 km circuit, 4 corners per lap, 10 km/h speed loss at each corner, one hour duration, 80 kg rider/6.5 kg bike/1.75 kg rims/tires/spokes, there would be 160 corner jumps. This effort adds 387 kilocalories to the 1100 kilocalories required for the same ride at steady speed. Removing 500 g from the wheels, reduces the total body energy requirement by 4.4 kilocalories. If the extra 500 g in the wheels had resulted in a 0.3% reduction in aerodynamic drag factor (worth a 0.02 mph (0.03 km/h) speed increase at 25 mph), the caloric cost of the added weight effect would be canceled by the reduced work to overcome the wind.

Another place where light wheels are claimed to have great advantage is in climbing. Though one may hear expressions such as "these wheels were worth 1–2 mph", etc. The formula for power suggests that 1 lb saved is worth 0.06 mph (0.1 km/h) on a 7% grade, and even a 4 lb saving is worth only 0.25 mph (0.4 km/h) for a light rider. So, where is the big savings in wheel weight reduction coming from? One argument is that there is no such improvement; that it is "placebo effect". But it has been proposed that the speed variation with each pedal stroke when riding up a hill explains such an advantage. However the energy of speed variation is conserved; during the power phase of pedaling the bike speeds up slightly, which stores KE, and in the "dead spot" at the top of the pedal stroke the bike slows down, which recovers that KE. Thus increased rotating mass may slightly reduce speed variations, but it does not add energy requirement beyond that of the same non-rotating mass.

Lighter bikes are easier to get up hills, but the cost of "rotating mass" is only an issue during a rapid acceleration, and it is small even then.

http://en.wikipedia.org/wiki/Bicycle_performance

unixnerd

As an engineer I have respect for the maths. I also know from experience the bike feels much easier to climb on with my lighter wheels. So to me that suggests that whoever did the maths didn't take all the variables into consideration, just because something looks complex mathematically it doesn't mean it's correct. It's only right given the input parameters used to formulate the theory.

thescouselander

What other variables could there be? If heavier wheels somehow rob energy causing power to be diverted from moving the bike forward then where has that energy gone?

I can see how lighter wheels help to a certain extent as you are lugging less metal (or carbon) up the hill but this rotating mass idea doesn't make sense to me.

Wirral_paul

unixnerd wrote:

As an engineer I have respect for the maths. I also know from experience the bike feels much easier to climb on with my lighter wheels. So to me that suggests that whoever did the maths didn't take all the variables into consideration, just because something looks complex mathematically it doesn't mean it's correct. It's only right given the input parameters used to formulate the theory.

Absolutely - and taking the sums from someone with an A-level in Physics?? Really?? Come on now be serious!! I have grade A's at that level in Maths, Physics and Chemistry but wouldnt get close to calculating all the variables. Lighter wheels have been used by the Pro's in the mountains for years and years - so no 18 year old with an A-Level is going to prove they're right and the Pro's wrong

Wirral_paul

thescouselander wrote:

I can see how lighter wheels help to a certain extent as you are lugging less metal (or carbon) up the hill but this rotating mass idea doesn't make sense to me.

Gravity?? Next time you're on a hill, get up to 15mph and stop pedalling - and see how long it takes you to stop. Try the same on the flat and obviously you go a lot further. The wheel rotation speed starts off exactly the same and so given the same wheels/tyres - the Kinetic energy is the same. Assuming road surface is comparable, the difference is gravity.

So to maintain speed on a hill you have to pedal harder than you would do on the flat and simple physics says that to maintain the same speed, you need to accelerate forwards at a rate equal to the force slowing you down (ie air resistance, friction and when going uphill - gravity). You're therefore constantly putting in an accelerative effort to maintain speed - and the calculation therefore needs to be made about which is greater - the extra potential energy stored in a heavier rim, or the energy input required to accelerate that extra mass. The A-level mathematicians havent taken this into account - they only did some basic sums based on static (non rotating) mass by the looks of it.

thescouselander

Yes I agree that, with everything else being equal, a heavier wheel set will require more effort to get up the hill as there is more mass gaining altitude.

The calculation doesn't need to consider the rotating energy stored in the rim as that will be recovered when the rider stops pedalling when the fly wheel effect will cause the bike to slow down slightly slower than the bike with the lighter wheels.

Effectively the wheels are acting as an energy store. They absorb energy as the speed builds up causing acceleration to be slower but during deceleration that energy comes out again causing deceleration to be slower.

P_Tucker

Wirral_Paul wrote:

unixnerd wrote:

As an engineer I have respect for the maths. I also know from experience the bike feels much easier to climb on with my lighter wheels. So to me that suggests that whoever did the maths didn't take all the variables into consideration, just because something looks complex mathematically it doesn't mean it's correct. It's only right given the input parameters used to formulate the theory.

Absolutely - and taking the sums from someone with an A-level in Physics?? Really?? Come on now be serious!! I have grade A's at that level in Maths, Physics and Chemistry but wouldnt get close to calculating all the variables. Lighter wheels have been used by the Pro's in the mountains for years and years - so no 18 year old with an A-Level is going to prove they're right and the Pro's wrong

If you actually read the article, it agrees that lighter wheels will get you up the mountains quicker - it just says that the difference isn't that much. Obv if youre racing up alpine cols then the small benefit is important - if you're a fat dentist its not.

P_Tucker

Wirral_Paul wrote:

thescouselander wrote:

I can see how lighter wheels help to a certain extent as you are lugging less metal (or carbon) up the hill but this rotating mass idea doesn't make sense to me.

Gravity?? Next time you're on a hill, get up to 15mph and stop pedalling - and see how long it takes you to stop. Try the same on the flat and obviously you go a lot further. The wheel rotation speed starts off exactly the same and so given the same wheels/tyres - the Kinetic energy is the same. Assuming road surface is comparable, the difference is gravity.

So to maintain speed on a hill you have to pedal harder than you would do on the flat and simple physics says that to maintain the same speed, you need to accelerate forwards at a rate equal to the force slowing you down (ie air resistance, friction and when going uphill - gravity). You're therefore constantly putting in an accelerative effort to maintain speed - and the calculation therefore needs to be made about which is greater - the extra potential energy stored in a heavier rim, or the energy input required to accelerate that extra mass. The A-level mathematicians havent taken this into account - they only did some basic sums based on static (non rotating) mass by the looks of it.

This is priceless, keep digging. After a few more posts demonstrating how you've forgotten everything you learnt at A-level, you might finally realise that the sums weren't actually done by A-level students

Wirral_paul

Trolling again Mr Tucker?? So tell us your qualifications then seeing as you clearly disagree (but cant demonstrate why - like usual)!!

P_Tucker

Wirral_Paul wrote:

Trolling again Mr Tucker?? So tell us your qualifications then seeing as you clearly disagree (but cant demonstrate why - like usual)!!

Where did I state that I had any? I merely posted the work of those that do.

Wirral_paul

P_Tucker wrote:

Wirral_Paul wrote:

Trolling again Mr Tucker?? So tell us your qualifications then seeing as you clearly disagree (but cant demonstrate why - like usual)!!

Where did I state that I had any? I merely posted the work of those that do.

Just a PhD in trolling then. That figures

Wirral_paul

P_Tucker wrote:

Wirral_Paul wrote:

Trolling again Mr Tucker?? So tell us your qualifications then seeing as you clearly disagree (but cant demonstrate why - like usual)!!

Where did I state that I had any? I merely posted the work of those that do.

You should write to Team Sky (and every other cycling team in the world) then - and tell them that lightweight wheels make no difference. You can also disprove the following article which quotes "an ounce off the wheels is worth a pound off the frame" and so prove 100 years of practical experience wrong!!

http://www.cycling-inform.com/equipment/177-cycling-equipment-to-help-you-climb-hills-faster

thescouselander

There's a very good write up based on some good measurements here:

http://www.rouesartisanales.com/article-15988284.html


It seems there is some advantage to be had but the difference between the best and the worst is quite marginal. The difference between the normal sorts of aluminium rimmed wheels that are so common is practically none existent.

Wirral_paul

thescouselander wrote:

There's a very good write up based on some good measurements here:

http://www.rouesartisanales.com/article-15988284.html


It seems there is some advantage to be had but the difference between the best and the worst is quite marginal. The difference between the normal sorts of aluminium rimmed wheels that are so common is practically none existent.

Be careful drawing conclusions from the above link - their assumptions are based on short accelerations on the flat and while the energy differences are small (edit - actually the differences are big when viewed as a percentage), a long hill will multiply that energy consumption

Of relevance to wheels for climbing is 3/4 the way down here under "Interpetations"....

http://www.rouesartisanales.com/article-4934445.html

"Then the stiffness/moment of inertia ratio will translate the ability of the wheel to climb or accelerate. In mountain or hill, while accelerating after a
corner or in the peloton, the cyclist stands on the bike from the left to the right transmitting an important and irregular torque. Therefore he needs stiffness and low inertia to be the least
tired."

And further up is stated that weight has the biggest influence on inertia - ie low weight = low inertia. Hence lighter rims with lower inertia accelerate or climb better

thescouselander

I dont see how a hill will multiply the energy consumption - the only difference will be the additional energy that is needed to account for the increase in potential energy of the bike and rider due the the change in height. Accelerations on the flat will yield the biggest differences because that is where the largest changes in speed occur. In any case the measurements they took demonstrated the differences were very small.

I could believe stiffness might make a difference though as a spongy wheel might well be noticeable and could result in brake rub.

Wirral_paul

thescouselander wrote:

I dont see how a hill will multiply the energy consumption - the only difference will be the additional energy that is needed to account for the increase in potential energy of the bike and rider due the the change in height. Accelerations on the flat will yield the biggest differences because that is where the largest changes in speed occur. In any case the measurements they took demonstrated the differences were very small.

I could believe stiffness might make a difference though as a spongy wheel might well be noticeable and could result in brake rub.

Just the length of your average hill is a much longer effort than an acceleration out of a corner.

Potential energy? I dont see the real relevance? A cyclist at the top of a hill will have potential energy (Potential Energy = Mass x Gravity x Height) that is released on a descent, but its of no relevance to a rotating wheel (but is on overall mass)

P_Tucker

This really does serve as a warning to us all – if you absolutely must make a tit of yourself on the internet (and we all do from time to time), whatever you do don’t pompously state your A-level results beforehand. I will keep my A-level results secret, as I’m doubtlessly going to make at least one f*ck up in the following condescending tirade.
Dealing with each of your misunderstandings in turn:

1. For once, I wasn’t trolling. I posted a useful response showing the relatively simple physics (which will have been reviewed by hundreds of people with physics degrees) behind the question that was asked. That you failed to grasp that my A-level comment was merely a reference to how simple the physics is doesn’t make it trolling.
2. No-one has said that light wheels don’t make a bike go up hills faster – they do, because they lower the overall weight of the bike. Team Sky already know this. Everyone knows this. Try actually reading what people have written FFS.
3. An article which is basically some guy stating his opinion doesn’t require disproving. Science or GTFO.
The exam question here is not “does having a lighter bike make me go uphill faster?” – it trivially does (albeit not by a material amount unless you’re riding a cast-iron frame or racing in the TdF) – its “does it matter where the weight is on a bike?”. So imagine two bikes, identical in every way except that one has a 200g seatpost and 1000g rims (pair) and the other has a 400g seatpost and 800g rims.

Now, as scouselander has patiently tried to explain to you, this is really really simple. Potential energy gained by climbing is very relevant – two identical riders of say 80kg (bike, kit and rider) gaining the same height have the same potential energy regardless of how the weight is distributed on their bikes. If we assume that they climb at the same speed, then they’ll have spent the same amount of energy moving air out of the way too.

Now, assuming that the law of conservation of energy holds for cycling as well as the rest of the observable universe (a stretch, I know):

Energy used = potential energy gained + energy used moving air out of the way + small rolling resistance (drivetrain, tyres etc)

Which is clearly the same for both. So if you’re climbing at a constant speed, it matters not where the weight is on your bike.

Now, for acceleration. Unless you are using your brakes on a climb, any energy you use accelerating a heavy rim will be returned in the form of slower deceleration. This is called the “conservation of momentum” and should have featured in your A-level in which you achieved a grade A. Now, if you start from rest and climb at say 12kmh, the lighter rims WILL save you some energy during this initial acceleration. And by “some”, I mean “really not very much at all in the grand scheme of things, about the same as a gnat tap-dancing for 2 minutes”. After that, its entirely* the same, because you’ll be travelling at a constant speed.

But wait – what if the gradient isn’t constant and you travel at different speeds for the same power output? Or you’re in a race and there are attacks and such? Lets say you’re travelling along a nice 5% section at 15kmh and happen upon a 10% section. Now, because the bike weight is the same, it takes no more energy to climb said wall due to total weight being equal – however the heavier rims have more energy stored so – wait for it - the heavier rims will release this energy as you decelerate and will actually get you to the top of the 10% bit ever so slightly sooner. I KNOW, RIGHT? However, once you get to the top of the 10% section it’ll take more energy to spin your rims back up to 15kmh. These effects will largely cancel each other out.

The only time when momentum is lost is when you use your brakes. A crit is the obvious example of something that requires constant accelerations and braking, but the wiki page calculates this and it turns out to be rather small. The other time it might be relevant is when Contador attacks and you’re scrabbling to accelerate onto his wheel and 2cm may well be the difference between winning the Tour or not – but I’m pretty sure that doesn’t apply to any of us on here FFS.

* As has been noted, because of dead spots in the pedal stroke you’ll actually be accelerating and decelerating constantly. Because of the conservation of momentum as outlined above, this is largely immaterial – but if we must cross the t’s, heavier rims will act like a flywheel and keep the speed ever so slightly more constant than lighter rims. Since air resistance varies as a function of speed SQUARED, lighter rims will actually take fractionally more energy to climb at a “constant” pace because during the power phase of the pedal stroke you’ll achieve a marginally higher speed. That said, I worked out the figure, multiplied it by the number of “what bike?” threads on BR and it was still less than the square root of bugger all.

There. Please print this out and put in on your wall in place of your soon to be rescinded Physics A-level certificate.

thescouselander

Yeah, I concur with p_tucker - I just couldn't be bothered to type all that out. Great explanation by the way.

Wirral_paul

P_Tucker wrote:

If we assume that they climb at the same speed, then they’ll have spent the same amount of energy moving air out of the way too.

Wrong. If we were talking about static mass then it would hold up - but we're not, we're talking about rotating weight and given how you now agree that lighter wheels are faster uphill - how do you think that this can be the case? You're over-simplifying Physics to suit your argument. Pro's are riding bikes that are generally pretty much all bang on the UCI minimum weight limit regardless of how they set them up, so why would they fit lighter wheels for the mountains and then add static balast to meet minimum weight, given that there's no overall weight reduction.

As for the trolling - your problem P_Tucker is that you do it so often that many will automatically assume you're doing it - even if you try to make a serious post!!

I'll leave you to it anyway!! I'm sure the regulars on here will be well aware of your trolling

Just for those who agree that lighter wheels help acceleration, but cant see how this translates to climbing

http://www.active.com/cycling/Articles/Do-Lightweight-Wheels-Really-Make-a-Difference.htm

"Climbing wheels are built extra light because when the grade becomes steep, the bicycle slows and then accelerates slightly between each pedal stroke. The extra energy that this pulsing motion eats up can be considerable, so reducing the mass of the wheels—especially the rims and tires—can save a lot more energy than removing considerably more mass from the bicycle or rider."

So P_Tucker - you explain how i'm wrong when I say that a climb is essentially one long acceleration to counter the force of gravity slowing you down and is why light rims are better for climbs (nothing to do with overall bike weight)

P_Tucker

Wirral_Paul wrote:

P_Tucker wrote:

If we assume that they climb at the same speed, then they’ll have spent the same amount of energy moving air out of the way too.

Wrong. If we were talking about static mass then it would hold up

Remember that reading thing we talked about? Well, try reading my CLEAR STATEMENT again and telling me how the mass of something solid affects how much air it moves out of the way.

Wirral_Paul wrote:

- but we're not, we're talking about rotating weight and given how you now agree that lighter wheels are faster uphill - how do you think that this can be the case?

Simple - lighter wheels are faster because they lower the weight of the system as a whole. I STATED THIS CLEARLY at the top of my post. The question, again CLEARLY STATED, is whether where the mass is located matters. The answer is yes, but not very much at all

Wirral_Paul wrote:

You're over-simplifying Physics to suit your argument.

Please clearly explain where my physics is materially incorrect. You've got an A at A-level which you're clearly very proud of, this should be easy for you.

Wirral_Paul wrote:

Pro's are riding bikes that are generally pretty much all bang on the UCI minimum weight limit regardless of how they set them up, so why would they fit lighter wheels for the mountains and then add static balast to meet minimum weight, given that there's no overall weight reduction.

Dunno. You'll have to ask them. Probably for the attacking scenario I CLEARLY STATED, or perhaps because they're paid to advertise "climbing wheels" to the public. Or perhaps their bikes aren't bang on the 6.8kg limit for flat stages, given that they all ride bog standard groupsets and SRMs.

Wirral_Paul wrote:

Just for those who agree that lighter wheels help acceleration, but cant see how this translates to climbing

http://www.active.com/cycling/Articles/Do-Lightweight-Wheels-Really-Make-a-Difference.htm

"Climbing wheels are built extra light because when the grade becomes steep, the bicycle slows and then accelerates slightly between each pedal stroke. The extra energy that this pulsing motion eats up can be considerable, so reducing the mass of the wheels—especially the rims and tires—can save a lot more energy than removing considerably more mass from the bicycle or rider."

This guy has a physics degree, does he? Or is he just a bike journalist? Posting instances of people who hold the same opinion isn't evidence. Proving that my physics is wrong is evidence.

Wirral_Paul wrote:

So P_Tucker - you explain how i'm wrong when I say that a climb is essentially one long acceleration to counter the force of gravity slowing you down and is why light rims are better for climbs (nothing to do with overall bike weight)

I have. Try reading it. The extra energy used when climbing is perfectly described by the increase in potential energy by the formula: work done = force * distance. If you believe that the rotational weight makes a difference, first state where you think the energy goes (or does cycling not obey the laws of the universe) then calculate it.

Wirral_paul

P_Tucker wrote:

Remember that reading thing we talked about? Well, try reading my CLEAR STATEMENT again and telling me how the mass of something solid affects how much air it moves out of the way.

Huh?? What on earth has this got to do with anything. As for proving YOUR physics - you dont have any of your own. You clearly just copy article and dont understand whats written - and so you cant translate that to the point!! You say yourself that lighter wheels are faster uphill, but then try and claim that heavier rims conserve energy better.

I really do give up. Believe what you want - i'm not rising to any more of your desperate attempts to cause yet another argument. You're famous for it.

Bye bye

Mikey23

Only O level physics here and many years ago....

So are we to conclude then that for those of us who Pootle along at 15 mph average on our entry level road bikes there is no point whatsoever in spending our hard earned dosh on an expensive set of wheels?