Slowman wrote:
marcag wrote:
Slowman wrote:
i don't want to appear abstruse or argumentative. i'm just going to tell you how i approach this. the chart you present is from a slowtwitch article from about 3 years ago and, as well as i remember (from memory) relies on drum testing. what we know - what i think i know - is that drum testing has a problem, but that this problem is generally overlooked because while drum testing is not reliable at telling you a tire's optimal pressure on a given (or any) course, the relative values are reliable. meaning, it can't tell you what pressure your conti 5000 should run at, but it's reliable at telling how that tire stacks up against a schwalbe pro one tt. is that fair? are we agreed on that?actually the article was quoting a Silca article that was showing data on the road in real world conditions. BTW, this data lines up perfectly with my experience of testing on the road, hence why I believed it to be correct.
It showed trends in rolling resistance on different surfaces at different tire pressures.
It showed that on rough surfaces CRR trended up or flat like the trends Zipp shows with it's red lines
It showed that on good surfaces CRR dropped. We don't see this on the Zipp charts
It showed that on good surfaces at higher pressures, the CRR saving is as substantial as the improvements Zipp shows in it's charts .
Maybe, the data on the zipps are simulations of rough roads only. I don't know.
The real question for me is "are these wheels faster on a given course (say Kona)" ? I have never been to Kona, but if the roads are good, it's really not obvious these wheels are faster.
let's stipulate that the chart you show reflects accurately the Crr on existing surfaces. that's a big assumption, because you have al morrison data, tom anhalt data, drum testing, field testing, all showing up on the same charts. still, these are smart folks (al, tom, josh) so let's just assume all of that is more or less accurate.
i don't see that in the data i presented in my article that zipp discusses variable road surfaces. perhaps i just still don't get your point. show me in the article i wrote where zipp is arguing road surface texture was even broached. for sure, the morrison test showed a higher optimized pressure. but let's stipulate it's accurate. that was a 23mm tire, tubed, on morrison's drum. it was not a 25mm or 28mm tire, tubeless, on a different surface using a different test rig paradigm.
all the testing zipp did was on one surface, that zipp considered representative of a typical event (triathlon or road race). what i would say - and did say - is that ideal pressures on zipp's chart seem curiously low for the 858 NSW. as i noted above, i'd like to know why that is. but we've come a long way since 100psi was the optimal pressure. we're not running 23mm tires anymore, many of us have moved past 25mm tires, and the pro peloton in europe went from completely-anti tubeless to "you must provide us tubeless!" in 1 year (from last year to this).
i would make these points:
1. did you ride 28s in your real world testing? it might be my imagination, but i get the impression that the things-that-roll cogniscenti are biased against that tire size, just as they were at one time (not that long ago) biased against 25mm, wider inner bead widths, disc brakes, clincher, then tubeless, then hookless. (but they weren't dumb; they were very obviously right about one thing: lower pressures.)
2. throw off any bias you might hold against 28mm tires, and embrace the possibility that this tire width in concert with tubeless, hookless, new well designs might conspire to create a system that reacts differently than what you're used to.
3. your say that your real world testing backs up drum testing, as i understand it. zipp says its field testing validates its rider-on rolling road Crr testing. i don't where that leaves us, except with more testing to do.
as i said in the beginning yes, there are some things that don't make sense to me, that need explanation, and i listed what those were. you think those inconsistencies make this an uncompelling wheel for kona. i find the data compelling, and believe the wheel ideal for kona. what accounts for the space between us?
i recognize both the apparent inconsistencies in rolling road testing and in drum testing, and i try to make sense of them both; and glean what's of value out of each. the experts minimize, gloss over, or reject the inconsistencies in drum testing. i look forward to the conversation we might have when we throw it all out there on the table and deal with the data we like and the data we don't like.
Let me try this another way. When I read the article I look at the red line (old wheels, 25mm tires). This should be my reference, something I can relate to.
Then I look at the improvements with the new system.
My reference is the red line and the improvements are in the yellow/orange lines
The problem is the red line does not compute for me. If I cannot wrap my head around the "reference" I cannot appreciate the possible improvement
The reason the red line does not compute is that it doesn't match data I have seen from Tom, Silca or my own experience. So I try to understand it.
Then I realized the trend Zipp was showing matched the trend Silca showed for bad road surfaces. So maybe (I don't know) their data is based bad/rough surfaces. I don't know, but it's the only way I can make sense of the trend they see for the red line (my reference)
Maybe their data is valid for Paris Roubaix, but not my local formula 1 track.