Hi,



If we agree that we're testing roling resistance and nothing else then let me tell you with 100% absolute certainty that there is 100% correlation between the results as found in the lab and in the real world.

IOW a tyre that does not show good rolling resistance figures in the lab won't roll well in the real world either and vice versa.

I personally do not object to the methodology used in that test it's just that some of the conclusions they draw from the outcome are completely off the wall.

Anyway, pls reread my previous post and maybe you'll understand it better.



Papers, what papers?
All it does is confirm (once more) what every engineer (and everyone with a bit of common sense for that matter) already knows for at least a century.
I'd be happy with that if it were not that they just had to add some complete nonsense which does nothing for their credibility, quite the opposite.

Ciao,

_________________
Being a snob is an expensive hobby.

Agreed. But did you read the study to see how they controlled for these variables, or are you just hypothesizing? Take the time to read the study and then make up your mind, but don't comment on something you haven't read.

The problem here is that people prefer to rely on anecdotal evidence rather than the best available data. Are there flaws in BQ's methodology? Sure. But it is the best analysis we have right now of the relationship between real-world riding conditions and tire brand, width, and pressure.

And the funny thing is all these tests were done years ago, but nobody paid attention to the benefits of wider tires until Specialized contracted out a study that basically confirmed the results of the BQ analysis.

Anyway, all of this has been argued ad infinitum on various internet boards, in some cases for years. If people prefer to rely on anecdote over evidence, more power to them!

_________________
Riding the Catskills

There is only a moderate correlation between rolling resistance results as found in the lab and in the real world, contrary to what you've said. Drum tests may be relevant for track racers, but not for anyone who rides on an actual road.

And regarding the papers, several studies were published in Bicycle Quarterly, which isn't a peer reviewed journal but they do provide detailed information on their methodology and results.

_________________
Riding the Catskills

Hi,

Obviously you do not seem to get it:





Maybe if you had you would not need to retort with such poor arguments?

Read this first as well while you're at it:

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

Ciao,

_________________
Being a snob is an expensive hobby.

We are clearly not arguing about the same thing. Perhaps take a moment to consider whether your argument is even remotely related to the issue at hand. In any case, this has been rehashed thousands of times elsewhere. Please do take a moment to read the studies. Wikipedia is not a valid source.

The last word is yours.

_________________
Riding the Catskills

Hi,



I see. Someone must be moving the goalposts then?

So, in a nutshell: rolling resistance has been redefined since I last went to college, I read studies but clearly not the right ones and Wikipedia is not a valid source even when all it takes is a simple law of physics.

Excuse me for trying to mingle with brighter minds than my own.....

Now if you would be so kind to let the rest of the world know what you are talking about, what it is that has been rehashed a thousand times before and what on earth "the studies" are, we'd all be much obliged.

Thank you for posting,

_________________
Being a snob is an expensive hobby.

The argument made by Heine against roller testing is that dissipation in the rider (by transmitted vibrations) is an important component of rolling resistance (an energy dissipation term proportional to speed and roughly proportional to weight). Therefore roller tests would tend to over-estimate optimal tire pressure, since a cost of high pressures, which is increased damping in vibrating the rider, would be neglected.

By shifting the preference to lower pressure, that shifts the preference to wider, thinner tires.

This has been debated on BikeTechReview's forum.

A curious conclusion reached by Bicycle Quarterly is that latex tubes are slower. But I suspect this was an artifact of their particular choice of tubes. Al Morrison @ BikeTechReview clearly shows better results from latex.

_________________
http://djconnel.blogspot.com/
Fuji SL/1
Send your data to Weight Weenie listings!

Hi,



If that is true it has nothing to do with the rolling resistance of the tyre as such but everything with the rolling resistance of a bicycle, his rider, his wheels and the damping factors of all of these combined.
Therefore the measured rolling resistance will vary with the impact of any of the above factors and it will change continously whilst moving from one piece of road to the next. Hell even the airpressure level surrounding the rider will effect the rolling resistance.

Now tell us, should we cover our bikes in sorbothane? Should we lose or gain weigth? Should we use saddles with or without padding? Back to steel or titanium frame?

I could be wrong but IMO the bulk (as in 95% or more) of the dissipation of energy is happening at the suspension end of the bicycle, IOW the tyres.
So, and I say this with respect, if mr. Heine wasn't measuring tyre rolling resistance but rolling resistance in general he should not have stopped at just measuring tyre rolling resistance either, wouldn't you agree?

I think they also forgot to measure the rolling resistance of the road they did the testing on as that too is a variable which can vary against yet another pile of variables as well....

For clarity's sake, I'll repeat it once again, Crr, in casu tyre rolling resistance, is a relative value allowing you to compare what can reasonably be compared. IOW it will allow you to create a picking order of preference from the testresults.
A tyre with a low rolling resistance relative to another tyre tested on a drum, in a lab, at a constant speed, constant load, is going to keep this low rolling resistance relative to that other tyre no matter what testing protocol you throw at it unless you bias that protocol to favour one outcome over the other. E.g. wildly overinflate, underflate, whatever.

Throwing in a road (which is only going to modulate reaction force R) and replacing W, a dead weight serving as a constant load, by a highly absorbant mass such as a human body, is not going to change the relative rolling resistance of one tyre to another.
Anything else, as described above, has nothing to do with rolling resistance but has everything to do with trackability.
Much in the same way a phonograph cartridge can track a groove thanks to its (electrical) load and suspension if you like.
In a similar vein a bicycle frame, wheel, you name it, can be optimised by applying well understood physics. Vertical compliance, choice of layups, variable wall thickness, pipe shapes, asymetry, etc. etc. can all be varied to obtain a particular sought after result.

The list is endless but to give one example: the current reversion to the old 27.2mm standard for seatposts because it is perceived as being more comfortable is not a mere incident. It is just applied physics nothing more, nothing less.
It too contributes to making a bike "roll" better.....

Ciao,

_________________
Being a snob is an expensive hobby.

No one uses roller tests to determine optimal tire pressure.



Every real test shows latex is better. BQ's different result is due to a poor test protocol.

5 years ago I analyzed BQ's test and determined that a 1 mph difference in wind was equivalent to changing Crr by ~.004... which is the total Crr for a good tire! In other words we are looking at +-100% error for 1 mph wind!. And there are a bunch of other errors to boot.

_________________
formerly rruff...