23mm 100psi faster on short climbs?

[madmacca]

I'm using Robino Pro's and they corner better than GP4000s and were only $23 each. Never been a fan of wide tyres, even when I was in the State Squad for the Track as a young bloke. Train on heavy, race on light.

Foo

Well, track is the one place where narrow hard tires still rule. Not many suspension losses on a velodrome.

[foo on patrol]

You still need to train on the road.

Foo

[kenwstr]

While the testing shows that rolling resistance increases with tyre widths < 25mm, rolling resistance isn't everything. For example, a lot of people use sealed bearings despite the very obvious fact that properly adjusted cones have lower resistance.... Rolling resistance is very small and constant at all speeds. aero drag on the other hand is proportional to the square of speed. That is, doubling speed quadruples aero drag. So 40 kmph is 64 times the aero drag of 5 kmph. For this reason, aero drag is far and away the most major drag consideration. Thinner tyres means less area for that drag to act upon = less aero drag. This is something to keep in mind generally though if you are talking climbing, the speed and aero drag are presumably less than on a flat road. Another consideration here in rotational momentum. Wider tyres and tubes means higher rotational mass and momentum, so tends to smooth out deceleration and acceleration with small terrain variations. This seems to fit with the OPs observations. So far, my preference remains with 23mm but I'm a light weight. It seems to me that these things jump around in fad cycles in most every sport but eventually settle down to a relatively stable perceived optimum.

Ken

[HausFinch]

Jan Heine believes some bike frames (thinner walled, more flexible tubes) take and return rider energy in a manner that increases power output compared to very stiff ones. This is most noticeable on climbs. Bicycle Quarterly ran an interesting test of this theory using four identical bikes that only varied in the flex character. More flexible frames averaged 12% higher power output by the test riders, and two of three testers we're 100% accurate in identifying what tubeset they were on.
https://www.google.com/url?sa=i&source= ... 8611547146

[g-boaf]

Jan Heine believes some bike frames (thinner walled, more flexible tubes) take and return rider energy in a manner that increases power output compared to very stiff ones. This is most noticeable on climbs. Bicycle Quarterly ran an interesting test of this theory using four identical bikes that only varied in the flex character. More flexible frames averaged 12% higher power output by the test riders, and two of three testers we're 100% accurate in identifying what tubeset they were on.
https://www.google.com/url?sa=i&source= ... 8611547146

Who needs a hidden motor, everyone will just be riding spaghetti bike frames. I'm not buying it.

[HausFinch]

If you read the article and the responses from readers and editor replies Heine is very clear that it's a matching of rider to frame stiffness that results in an efficient synchronicity. He makes no blanket claim about more flex being unequivocally better. One tester couldn't discern a difference, possibly because they were less powerful and not benefiting from a frame spring effect. We do acknowledge that all bodies are different and riding styles and positions vary as well. Why would we assume all frames match all bodies/ styles?

[g-boaf]

So how powerful in watts must one be to benefit from this spring effect, and based on that, work out what this 12% works out to be in watts (and tell me that number) and finally then tell me if you really, truly believe that.

He makes no blanket claim about more flex being unequivocally better.

Sounds like John Howard's core and non-core promises. No, I don't believe a word of it.

[foo on patrol]

I would be more inclined to say that it is power to weight to frame ratio. Just like I don't abide by the tyre size and pressure chart.

Foo

[mikesbytes]

Show me the data.

While there is plenty of data out there on rolling resistance and aero, I have pondered what difference (if any) there is in power loss resulting from a softer inflated wider tyre over a narrower harder inflated tyre

==================

In regards to the frame flex, I suspect the flex is more about how the energy is distributed from the bottom bracket/chainring to the rear axel/cassette. If the rear of the frame is too stiff it causes the rear tyre to 'skip' with each pedal stroke

[singlespeedscott]

I know I prefer a more flexible bike over a ridged one when riding for longer than a few hours. When I don’t have the energy to climb out of the saddle anymore the more flexible frames I have ridden seem to climb better whilst seated.

[Alex Simmons/RST]

When testers were blinded to the bikes they were riding (supposed “compliant” and “stiff” frames that had frames covered), they were no better than random chance at picking the frame type when tyre pressures were controlled. The primary correlation for what frame type they thought they were riding was all down to the experimenter changing tyre pressure, not the frame.

[Thoglette]

When testers were blinded to the bikes they were riding (supposed “compliant” and “stiff” frames that had frames covered), they were no better than random chance at picking the frame type when tyre pressures were controlled. The primary correlation for what frame type they thought they were riding was all down to the experimenter changing tyre pressure, not the frame.

Cite please?

The following article had two of three testers able to tell the difference in a double blind test.
Myth 4: Stiffer Frames Are Faster

The results confirmed our previous impressions: Two of our three testers could identify which frame they were riding with 100% accuracy, just based on how the frames performed under hard pedaling.

[uart]

So how powerful in watts must one be to benefit from this spring effect, and based on that, work out what this 12% works out to be in watts (and tell me that number) and finally then tell me if you really, truly believe that.

He makes no blanket claim about more flex being unequivocally better.

Sounds like John Howard's core and non-core promises. No, I don't believe a word of it.

Hi g-boaf. It's not really a matter of you missing out on some kind of magical extra power if you have a stiffer frame, quite the reverse actually. The argument is simply that the power "lost" due to frame flex is not necessarily lost in reality, and in some cases much of it may be returned at a different part of the pedalling cycle.

When a frame flexes under pedalling pressure, some of the power delivered to the pedal during that time is not transferred to the drive train - it instead goes into flexing the frame. The amount of energy that gets "diverted" into flexing the frame is proportional to the product of the pedal force and the frame displacement, so for any given pedaling force this flex energy is directly proportional to the amount of frame flex.

The traditional view was that this energy is largely lost, and hence the desire for stiffer frames as they would lose less energy. The above research doesn't actually suggest that there is true energy boost to having a flexible frame, it instead only suggests that much of the "flex energy" may not actually be lost, and that the previously perceived disadvantage of frame flex may not be as much as thought.

Given this view of flex energy possibly being returned, they postulated that the amount of frame flex desired might be more a matter of what suits a particular rider's style (or even just what they are accustomed to) rather than some kind of "hard and fast" rule that stiffer is always better.

[uart]

When testers were blinded to the bikes they were riding (supposed “compliant” and “stiff” frames that had frames covered), they were no better than random chance at picking the frame type when tyre pressures were controlled. The primary correlation for what frame type they thought they were riding was all down to the experimenter changing tyre pressure, not the frame.

Cite please?

The following article had two of three testers able to tell the difference in a double blind test.
Myth 4: Stiffer Frames Are Faster

The results confirmed our previous impressions: Two of our three testers could identify which frame they were riding with 100% accuracy, just based on how the frames performed under hard pedaling.

One issue that I have with any research that shows riders unable to detect differences in frame flex when tyre pressures were "blindly" altered by the researches, is that it would only prove (if true) that tyre pressures have a stronger influence on the ride feel and performance compared to frame flex.

It wouldn't actually prove that frame flex had no effect or that it was truly undetectable. It would only prove that the confounding variable (in this case tyre pressure) had a stronger effect.

[mikesbytes]

.....

When a frame flexes under pedalling pressure, some of the power delivered to the pedal during that time is not transferred to the drive train - it instead goes into flexing the frame. The amount of energy that gets "diverted" into flexing the frame is proportional to the product of the pedal force and the frame displacement, so for any given pedaling force this flex energy is directly proportional to the amount of frame flex.

The traditional view was that this energy is largely lost, and hence the desire for stiffer frames as they would lose less energy. The above research doesn't actually suggest that there is true energy boost to having a flexible frame, it instead only suggests that much of the "flex energy" may not actually be lost, and that the previously perceived disadvantage of frame flex may not be as much as thought.

Given this view of flex energy possibly being returned, they postulated that the amount of frame flex desired might be more a matter of what suits a particular rider's style (or even just what they are accustomed to) rather than some kind of "hard and fast" rule that stiffer is always better.

That's how I understand it. I was wondering if there were any articles that explain how much of the flex energy gets transferred into forward motion

[Thoglette]

That's how I understand it. I was wondering if there were any articles that explain how much of the flex energy gets transferred into forward motion

Not that I know of: there's some armchair theorising in the article I linked earlier.