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Skldmark wrote:As you specify: if you do not change speed/velocity(accelerate,decelerate,or change direction/turn), it really doesn’t matter.
Volsung wrote:It's about acceleration and climbing. Everyone knows aero tops weight when riding flat or downhill.
Skldmark wrote:Yea, I only read “maintain same speed”. So are you just saying that the added weight of heavier tires is similar to any other weight you might add to the bike frame/fork?
clarksonxc wrote:and here we go again....
I'll never understand why some people cant understand that every pedal stroke, every wheel rotation is a (small) acceleration. That study has been posted here before. If the metric you are measuring yields a result like "reducing the wheel weight by 50% only save 0.5W" than the right metric is not being measured. But please, keep buying heavy wheelsets, you have every right to do so. I'll keep riding light ones and continue to enjoy my life.
Your other question is, does (Tire)weight matter as much as we think it does, and why do we focus on it so much?
To that I’d answer, that the biggest reason is we can all, easily and accurately measure weight.
Rolling resistance and aerodynamics are probably the biggest energy loss for most gravel riders, but they are very hard to measure, and very conditions dependent (the tire and pressure that is fastest on hard smooth clay might not be on chunky gravel or deep sand).
That leaves weight as the easiest aspect to look at.
Then, although @ljsmith is correct, that a model is not proof, it does seem likely that those models are fairly close. In other words, for most riding and racing, upgrading to a 100g lighter tire or 10mm deeper aero rim, won’t make a noticeable difference to your total time.
But at the same time, the only way to get to a total bike weight that is so low that it makes a noticeable difference, is by lightening up every single part. And for that, tires are your cheapest option, since unlike most other bike parts, lighter tires are not much more expensive than heavier ones.
The other thing is that bike inertia is something we can perceive quite well. So a bike with lower inertia (where tire and rim weigh matters more than frame weight), will feel more lively and fun. The models above are all talking about total energy to complete a ride, so they use total system weight. But a rider is not welded to his or her bike, so we do notice the difference.
Here is a good example from GCN. The rider using a power meter was a bit faster on the lighter bike at the same power, but the rider going by feel had a bigger difference!
Slim wrote:
Then, although @ljsmith is correct, that a model is not proof, it does seem likely that those models are fairly close. In other words, for most riding and racing, upgrading to a 100g lighter tire or 10mm deeper aero rim, won’t make a noticeable difference.
Defintely agree with that part about tires @ljsmith!
(And I did mention that in my first post about tire weights, also those two models do take rolling resistance into account, so you are correct, you’d have to adjust that as well).
Perhaps I should have said ‘heavier rims’ instead of ‘heavier tires’.
I guess my position can be summed up as follows:
ljsmith wrote:
I disagree that the models are "fairly close". Here is where assumptions come into play. The model assumes that for two given tires of different weight that they are identical apart from one weighing more than the other. That is where this mathematical model fails. Because in the real world a tire is heavier because its construction is different. It is physically impossible for two identically constructed tires to have different weights. A good example is in my basement, I have two 27.5 x 2.0 Schwalbe G-One Speed tires, they use the same rubber compound and tread pattern. One weighs 450g, the other weighs 530g. These mathematical models would suggest that there is a negligible difference between these two tires as far as speed. However The 450g tire is a liteskin tire and the 530g tire is a Snakeskin tire. The liteskin is 127 TPI and the Snakeskin is 67 TPI. What this results in is the liteskin is a thinner more supple tire with lower rolling resistance. So because of its construction it weighs less and its rolling resistance is lower. The point being that a lighter tire isn't just lighter, its more supple. This is not accounted for in the model. This is why you need to actually test this stuff rather than just bust out pie charts and calculations. The real world often reveals variables that were not accounted for. If a tire is heavier, it must be thicker or denser, both of which make it less supple and slower. There is no getting around this. You can't have a thinner more supple tire be lighter than a thicker one, you don't even need calculations for this, its common sense. However there are cases where a heavy tire may use a superior rubber compound and could be faster than a lighter tire. But comparing two tires with the same rubber compound like with my G-Ones, the lighter tire is going to be faster.
I have read and heard (with the math) that weight has been over emphasized. I understand and agree it might be oversold. But that does not make it irrelevant.
However, If I throw 10lbs on my bike, it makes a huge difference in acceleration and climbing (but not steady state). So yeah, I “believe” that saving a pound or two on my wheel sets can make a difference. My gravel bike weighs 17lbs, and it is a blast. Climbs like it has a motor (compared to my other bikes).
What I think is odd is that people here worry about aero. Unless I’m riding in a pack or competing, I’m not riding fast enough for aero to matter. Besides, I know that what I wear makes a larger difference than anything my wheels or tires can do aero wise (and is a lot cheaper to change). On gravel, I’m wearing baggy comfortable clothing, and don’t have my bars slammed. 15mph is a pretty brisk pace for me on gravel. Contrasted to the velodrome where I do care about aero, have Aero wheels, skin tight clothing, low bar height etc. as I’m sprinting close to 40mph. Anything sustained over 20, and I’m feeling the aero difference.
I did find it interesting to hear conti’s tire designer say they were comparing their tubular tires with the GP5000 clincher. The tires were unmarked, but everyone wanted to be on the GP5000 because they rolled so much faster than the much lighter conti tubular tires.