Wheel upgrade

[Citius]

There's no "helping me understand" going on. Just your opinion. I don't appear to have seen anything quoted to back it up?

Not my opinion, as such - more like a case of the reality of science. Yellow Saddle did try to explain some of this to you earlier, but you might have missed it. Anyway, here's a pretty good summary which often gets referred to in discussions like this: http://biketechreview.com/reviews/wheels/63-wheel-performance.

If you don't agree with what's in the link though, then that's entirely up to you - but if so, I would suggest you come up with your own explanation as to why it's not the case.

 

[swee'pea99]

Interesting. I've often wondered whether there's any difference between taking 500g off your own weight, the weight of the frame or the weight of your wheels, and have tended to assume that the answer is yes - that, more specifically, if you reverse that order, it tallies with the benefits. Ie, weight off the wheels makes a bigger difference than weight off the frame makes a bigger difference than weight off me.

The article at that link seems to suggest that I've got that wrong, and that in truth there's all but zero benefit to taking weight off wheels. Aerodynamic, yes; light, no. I'm certainly not equipped to challenge the science, but I have to say it does seem very counter-intuitive to me. I've never ridden really good wheels, but having switched from heavy ones to (no more aerodynamic) light ones, I have to say my perception was that it made a massive difference. Maybe I was just kidding myself and it was all some kind of self-delusional placebo thing going on...but I find it very hard to believe.

 

[Yellow Saddle]

My analogy was somebody walking along with a bottle strapped to their leg. Doesn't matter and not going to argue the point anymore!

Do you not agree that lighter wheels save more energy than the same saving on the frame?

We debated that one in two or three threads a while back.
Have a look at this link. I did the calculations for energy required to accelerate two different wheels up to speed.

https://www.cyclechat.net/threads/road-racing-aero-wheels.173743/post-3523626

You need to decide, and make some assumptions about that weight strapped to your leg. Is it one lump of weight that pumps up and down? Is it actually not strapped to your leg but distributed evenly along a flywheel bolted to the crank? If you want to get close to a scenario where that water bottle of yours is just a bit of weight at the outside perimeter of a wheel-like leg, then you may as well change your analogy and just look at the calculations in the above posts. If you want to stick with the scenario of a bottle strapped to the leg, then you're in trouble because that weight will pump up and down (not move in a circle) and will accelerate, decelerate, stop and accelerate again with each and every pedal stroke. This is a very inefficient scenario and lot like anything found on a bike.

Right now your analogy is too vague to make calculations. Modify it and we'll start again.

 

[Yellow Saddle]

Interesting. I've often wondered whether there's any difference between taking 500g off your own weight, the weight of the frame or the weight of your wheels, and have tended to assume that the answer is yes - that, more specifically, if you reverse that order, it tallies with the benefits. Ie, weight off the wheels makes a bigger difference than weight off the frame makes a bigger difference than weight off me.

The article at that link seems to suggest that I've got that wrong, and that in truth there's all but zero benefit to taking weight off wheels. Aerodynamic, yes; light, no. I'm certainly not equipped to challenge the science, but I have to say it does seem very counter-intuitive to me. I've never ridden really good wheels, but having switched from heavy ones to (no more aerodynamic) light ones, I have to say my perception was that it made a massive difference. Maybe I was just kidding myself and it was all some kind of self-delusional placebo thing going on...but I find it very hard to believe.

We did that calculation in this link - the same one I posted to BP's post. Have a look at it. Your answer was answered to the nth degree, complete with workable values and calculations.

https://www.cyclechat.net/threads/road-racing-aero-wheels.173743/post-3523626

 

[bpsmith]

We did that calculation in this link - the same one I posted to BP's post. Have a look at it. Your answer was answered to the nth degree, complete with workable values and calculations.

https://www.cyclechat.net/threads/road-racing-aero-wheels.173743/post-3523626

I remember that post now. It was so lengthy and vague at the time that found it hard to follow, likes others.

Have gone back and read through multiple times and believe that you have it backwards possibly?

You state that the heavier wheels require Less energy based on your calculations as you have more stored energy in the wheels getting to 30kmh. Surely this actually means you have used more energy getting the heavier wheeled bike up to said speed?

If not, then the manufacturers and pro teams should surely be significantly increasing the weight of their bikes and fitting heavier wheels to take advantage of your energy "savings" from heavier kit?

 

[Yellow Saddle]

I remember that post now. It was so lengthy and vague at the time that found it hard to follow, likes others.

Have gone back and read through multiple times and believe that you have it backwards possibly?

You state that the heavier wheels require Less energy based on your calculations as you have more stored energy in the wheels getting to 30kmh. Surely this actually means you have used more energy getting the heavier wheeled bike up to said speed?

If not, then the manufacturers and pro teams should surely be significantly increasing the weight of their bikes and fitting heavier wheels to take advantage of your energy "savings" from heavier kit?

No. Read again.

 

[bpsmith]

No. Read again.

Your words:

"Conclusion: it requires 0,4 percent more energy to accelerate a bike with tyres weighing 400 grams less than a bike of equal weight but with heavier tyres."

 

[Cyclist33]

Your words:

"Conclusion: it requires 0,4 percent more energy to accelerate a bike with tyres weighing 400 grams less than a bike of equal weight but with heavier tyres."

he was called on that small but v confusing typo later in the thread. youre right it should read "less" but the observation would remain that it makes diddly squat real world difference.

 

[Yellow Saddle]

As Cyclist33 said and I acknowledged it. However, I've now edited it to reflect the correction, I wanted to preserve the conversation but I suppose making the correction would save confusion such as this.

Point is, a large difference in weight on the wheel requires very little (insignificant) energy to accelerate the wheel just once, which is all it needs for the entire ride. Strapping it to your leg would require energy per pedal stroke. Hence my claim that your analogy is inappropriate.

 

[bpsmith]

he was called on that small but v confusing typo later in the thread. youre right it should read "less" but the observation would remain that it makes diddly squat real world difference.

Going back on topic to the question about it being better to save the weight on wheel or on frame/components, Any gain is better, however small? Reality is that it's a small gain, I agree, but it still exists.

Taking figures out of the equation, when I swapped the standard Defy 1 wheels for Zonda's the difference was obvious and immediate. The ride was transformed and my times improved on same regular route in same conditions. If we're talking real world then they were well worth the spend. I don't think I am alone there?

 

[Yellow Saddle]

Going back on topic to the question about it being better to save the weight on wheel or on frame/components, Any gain is better, however small? Reality is that it's a small gain, I agree, but it still exists.

Taking figures out of the equation, when I swapped the standard Defy 1 wheels for Zonda's the difference was obvious and immediate. The ride was transformed and my times improved on same regular route in same conditions. If we're talking real world then they were well worth the spend. I don't think I am alone there?

Going back to your analogy: strapping a weight to your ankle....

 

[bpsmith]

As Cyclist33 said and I acknowledged it. However, I've now edited it to reflect the correction, I wanted to preserve the conversation but I suppose making the correction would save confusion such as this.

Point is, a large difference in weight on the wheel requires very little (insignificant) energy to accelerate the wheel just once, which is all it needs for the entire ride. Strapping it to your leg would require energy per pedal stroke. Hence my claim that your analogy is inappropriate.

The analogy was a poor one and I have not commented on that since if you notice. Let's put this to rest then?

Quantifiable speaking, you now admit that there is an energy saving from lighter wheels over the same saving on the rest of the bike. Albeit a small saving.

In the real world, many of us have swapped wheels and noticed the difference straight away.

 

[Yellow Saddle]

The analogy was a poor one and I have not commented on that since if you notice. Let's put this to rest then?

Quantifiable speaking, you now admit that there is an energy saving from lighter wheels over the same saving on the rest of the bike. Albeit a small saving.

In the real world, many of us have swapped wheels and noticed the difference straight away.

I've always acknowledged it but also always attempted to quantify it. If you read the whole thread (I don't really expect you to, it is long), you'll see that I preamble it with a request for perspective. I also showed a way of calculating the difference which I kinda hoped people would use to plug in some real figures to get to a percentage difference but I think the point is missed by most, including again in this thread.
We are talking, when comparing real-life wheels, a couple of joules of energy once per ride - literally nothing and certainly not noticeable as you suggest. The main point of my calculation is to provide a worst-case scenario and calculate for that. Wheels are complex and their mass is not concentrated at the rim or tyre and to calculate the energy required to spin them up is extremely complex and even if I do it, someone will come and say that their wheel is different because the nipples are smaller than standard and therefore..... Or, they would say that they accellerate faster than that and therefore.....That's why I simply lumped all the weight at the worst possible place - the tyre and designed a simpler way of getting to an answer, as well as just calculate the energy for the end state. In real life the difference would be even smaller than 0.4% for the wheels I chose as an example.

The ultimate point I want to make is that it is silly to make wheel upgrade suggestions based on wheel weight. There are more important considerations.

 

[Cyclist33]

The analogy was a poor one and I have not commented on that since if you notice. Let's put this to rest then?

Quantifiable speaking, you now admit that there is an energy saving from lighter wheels over the same saving on the rest of the bike. Albeit a small saving.

In the real world, many of us have swapped wheels and noticed the difference straight away.

hmm, i didnt think thats what he modelled, personally. rather, that its irrelevant where you reduce the weight. am i wrong?

 

[Citius]

• Lighter wheels make the bike lighter - which is a good thing. For all kinds of reasons.
  
• Aside from a small initial benefit in acceleration, there is no significant benefit is losing weight from the wheels, comapred to any other part of the bike.
• Any disadvantages from accelerating heavier wheels will be returned in the form of slower decelleration

I think that's pretty much it - in a nutshell.