What is the rim width?
I am using Evo CX 20mm wide tires on a ZIPP rim (I think 19mm wide). While it may not be perfect, I think better than 23mm tire on a 19mm rim. Just a thought.
ehhhh doubt it. marketing hype
ehhhh doubt it. marketing hype
“Real world” measurements indicate that your speculation is incorrect…
What real world measurements are you referring to- besides the top piece? Do you think that gap is worth 5-6 watts? HED gets some of their bread buttered by Bontrager with their business relationship, but will only say the gap (that the bonty fills) is worth 2 watts/20 grams. And the data above includes Crr- so, it’s pretty interesting to see a tire that has 120 tpi to have such a low rolling resistance against some of the low rolling resitance leaders at MUCH higher TPI. It also goes against AL’s list, too (I’m assuming the veloflex is the record model). Also- on a different note- HED will say no difference between H3 Clincher and H3 tubular- yet- they test their H3C with the bonty TT tire- and a tubular won’t have as nice of an interface- so that doesn’t seem to fully fly. Another thing about the bonty data is that it says advantage is at 17mph or higher with a 10 mph HEADWIND- that’s a perfect zero degree yaw… pretty much non-existant in most real world TTs/Triathlon legs- hence why most people emphasize the 5-15 yaw range.
And the data above includes Crr- so, it’s pretty interesting to see a tire that has 120 tpi to have such a low rolling resistance against some of the low rolling resitance leaders at MUCH higher TPI. It also goes against AL’s list, too (I’m assuming the veloflex is the record model).
Bontrager has taken some weight out of the TT tire. I have some data on both wattagetraining and BTR showing much better Crr on the new tires. I’ve got a tire which weighed in at 181 grams which first tested at Crr = 0.00297 but is now down to Crr = 0.00264 after ~ 40 minutes on the rollers. I also bought a second tire at the same time which weighed 194 grams which first tested at Crr = 0.00297 - haven’t run anymore tests on it. One of Tom’s tires first tested at 0.00270 - it weighed 176 grams. The aero advantage should be present with each of these tires. The new data will be included in Rev 9.
What real world measurements are you referring to- besides the top piece? Do you think that gap is worth 5-6 watts?
Umm…my own 
At basically zero yaw, on 2 occasions (once on my old TriSpoke brand trispoke wheel, and another time on a borrowed 808) I apparently measured a reduction in CdA of ~.004-.008 m^2 as compared to a VF Record, after “correcting” for the Crr difference between the tires. So…that would equate to ~4-8W. However, I don’t know if the entire reduction can be attributed to the gap or at least partially just to it being a better width match to the narrow rim sections on both of those wheels. It IS narrower than the VF Record.
HED gets some of their bread buttered by Bontrager with their business relationship, but will only say the gap (that the bonty fills) is worth 2 watts/20 grams. And the data above includes Crr- so, it’s pretty interesting to see a tire that has 120 tpi to have such a low rolling resistance against some of the low rolling resitance leaders at MUCH higher TPI. It also goes against AL’s list, too (I’m assuming the veloflex is the record model).
Actually…it doesn’t go against Al’s list. If you look at some of his latest data, the “light” samples of that tire get their Crr down pretty close to the VF Record territory. Dunno why Hed is downplaying any gains for that…I guess it all depends on what tire they’re comparing it to…oh yeah, don’t forget that some of this goes against their “wider is better” philosophy of late, so there may not be much incentive to play up things if they look really good for that wheel. They don’t have a “C2 H3”…
Also- on a different note- HED will say no difference between H3 Clincher and H3 tubular- yet- they test their H3C with the bonty TT tire- and a tubular won’t have as nice of an interface- so that doesn’t seem to fully fly.
I think it may be a case of the tubular version not necessarily having a straight-sided brake track (as compared to the clincher). That said, with as little and conflicting information about the actual test protocols for the latest HED data, I’m not really sure what to make of all of it…
Another thing about the bonty data is that it says advantage is at 17mph or higher with a 10 mph HEADWIND- that’s a perfect zero degree yaw… pretty much non-existant in most real world TTs/Triathlon legs- hence why most people emphasize the 5-15 yaw range.
Ummm…it’s not clear to me that the chart of drag vs. apparent wind speed included the 10mph headwind…I think that’s in reference to the time savings quoted in the text, not necessarily for the chart.
The aero advantage should be present with each of these tires.
and this, of course,*is* the big question. There are so many questions WRT to the 'aero advantage' that I don't even know where to start--but I'll try anyway:
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why is the tire more aero, the ‘lip’ or the width? There’s no comparison to another 19mm tire, so who’s to say it’s not width alone (it’s nothing new to note that a tire that mates well to the width of the rim is ‘faster’. The VF20 (if it’s a record) is 21.7 or so (doesn’t sound like much, but it’s 10% wider than the Bonty).
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Damon’s tests shown earlier were done on a 19mm rim. How does the tire compare to a 21mm tubular on a 26-28mm (at it’s widest point) rim?? When you look at Hed’s data on it’s new wheels, it still appears that a 22mm tubular is quite a bit faster than the H3/Bontrager setup, at least at the yaw angles which concern me.
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the individual tire’s fit on the individual rim
-what is the actual aero advantage claimed by Trek on the Bonty Aero tire? While I understand the desire to make the data easily digestible, it would be a lot more helpful to know what the actual drag differences are among the different tires. Being that they’ve intentionally maximized the differences with a 10 mph headwind??, I wonder what other obfuscations are involved.
-how does a wheel with the gap ‘filled in’ compare?
As far as ‘real world data’, I have to confess that I’m pretty suspicious of trying to isolate a tire’s aerodynamics via field testing–for several reasons, first among those being the accuracy of the measuring devices themselves.
Anyway (and really Al, these questions aren’t directed to you!), as I said earlier–the chart really seems to ask more questions than it answers.
-how does a wheel with the gap ‘filled in’ compare?
http://www.sheldonbrown.com/rinard/aero/aerodynamics.htm says you save 2 seconds over 40km at 37km/hr. That’s only 1 watt- HED will say it’s 2 watts or 20 grams of drag- if you ask them via phone. It would have been good if they tested other true 19mm tires.
The aero advantage should be present with each of these tires.
and this, of course,is the big question. There are so many questions WRT to the ‘aero advantage’ that I don’t even know where to start–but I’ll try anyway:“snip”
Anyway (and really Al, these questions aren’t directed to you!), as I said earlier–the chart really seems to ask more questions than it answers.
I’ve had some/most of the same questions myself. Poor choice of words on my part - what I was trying to point out is that the aero performance of the tires would be the “same” regardless of weight - I think ??
How are the Bonty aero wings any different than a wheel/tire combo with the gap filled? Why would the Bonty setup be any faster? Isn’t it just a matter of convenience between the two as opposed to performance?
How are the Bonty aero wings any different than a wheel/tire combo with the gap filled? Why would the Bonty setup be any faster? Isn’t it just a matter of convenience between the two as opposed to performance?
yes that’s the point- but the bonty data shows 5 watt plus difference… per tire- or 2.5x what HED would say with their aero findings- and I’m sure HED has tested their wheels with many different combos- and the actual H3 clincher data on HED’s site is with the Bonty TT. Of course HED’s data is a little more ‘independent’.
-how does a wheel with the gap ‘filled in’ compare?
http://www.sheldonbrown.com/...ero/aerodynamics.htm says you save 2 seconds over 40km at 37km/hr. That’s only 1 watt- HED will say it’s 2 watts or 20 grams of drag- if you ask them via phone. It would have been good if they tested other true 19mm tires.
What depth wheel was that Kyle data taken with?..I’m thinking any benefit is greater the deeper the wheel.
As far as ‘real world data’, I have to confess that I’m pretty suspicious of trying to isolate a tire’s aerodynamics via field testing–for several reasons, first among those being the accuracy of the measuring devices themselves.
You are confusing the stated accuracy with the actual precision.
what’s the bottom line for people that don’t pay a whole lof of attention to this tire/wheel madness?
will i be better off with HED3’s mounted with bonty tt tires? time to ditch my zipp 909 tubulars with veloflex record?
what’s the bottom line for people that don’t pay a whole lof of attention to this tire/wheel madness?
Bontrager released their ad a day early?
what’s the bottom line for people that don’t pay a whole lof of attention to this tire/wheel madness?
will i be better off with HED3’s mounted with bonty tt tires? time to ditch my zipp 909 tubulars with veloflex record?
First, my tire mates way cleaner on my hed 3 than the picture Greg posted. I don’t know if it has to do with a change in construction or size of tire vs. rim but when i run my hand over my Bonti TT tire to the rim it indeed feels fairly smoothe.
Second, 909s with record tires are probably equivalent in speed to a set of Hed 3s with the bonti tt tires.
what’s the bottom line for people that don’t pay a whole lof of attention to this tire/wheel madness?
I’m thinking the take-away is: run a tire that matches your rim width, and get out the silicone. 
“I’m thinking the take-away is: run a tire that matches your rim width, and get out the silicone.”
Of course that is provided you pick a tire that ALSO has a low Crr…like maybe a VF Record.
But then, if you’re buying a set of VF Records…you’re spending more than you would on the Bonty TTs…
So why not just pick the purpose-designed tire?
How about keeping our current tires, but filling in the gap?
What you would you fill the gap in with? i was thinking about putting some sort of caulk or silicon in the gap, spreading it in with my finger to smooth it?
questions:
a) what material would not eat the tire?
b) what material would be not too sticky, and owuld let you change the tire easily?
Im thinking along the lines of silicon caulk or something like that?
One thing that i have found on other forums is using “RTV silicon”- ill try it, why not.