Some thoughts/data:
http://www.trainingandracingwithapowermeter.com/2010/11/aero-tires-and-wheels-skinny-vs-fat.html
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For me, comfort and puncture resistance improvements means 23s are the narrowest I would go.
A: VFR
B: CSS
C: BTTAW
or what I’d like to see:
A: VFR
B: BTTAW
C: CSS
.
Would you say that for pursuit races where yaw is basically 0deg, narrow is king?
Would you say that for pursuit races where yaw is basically 0deg, narrow is king?
Well, on the one hand the faster you go (in a straight line) and the less wind there is, the lower the yaw angle will tend to be.
On the other hand, even on an indoor track the yaw angle may approach 10 deg in the turns. Also, rolling resistance will be higher than you might think due to the increased centripetal force in the turns and the scrub angle on the straights.
The bottom line is that if I were, e.g., the Director of Marginal Gains for British Cycling, I’d want to do some careful modeling reflecting the specific conditions before deciding what width wheels/tires to recommend for pursuiting.
I would imagine aero/drag testing would be fairly easy to do on a velodrome? Is there a reason you don’t use a velodrome for your aero testing?
I would imagine aero/drag testing would be fairly easy to do on a velodrome?
It depends on the velodrome, actually. At some places it is hard to get access at a time when no/few others are on the track stirring up the air, etc. Furthermore, on some outdoor tracks wind can be more of a problem than when testing on the open road. However, at least on a track you don’t have to worry about cars or deer, as I do.
Is there a reason you don’t use a velodrome for your aero testing?
I’ve actually done aero testing at T-town, Indy, and ADT, and if I lived near a track (especially an indoor one) would probably do more. We don’t have a track suitable for this purpose in St. Louis, though.
very interesting read. I’d love to see something similar with a new C2 or Firecrest (on a good mating tire for them) vs. the old Shamal or a narrow zipp/hed rim.
Can you say what tire A,B, and C were?
I’d love to see something similar with a new C2 or Firecrest (on a good mating tire for them) vs. the old Shamal or a narrow zipp/hed rim.
Some independent testing would indeed be interesting. However, since the purpoted benefit of the new designs is primarily, if not entirely, evident at higher yaw angles, you’d have to take a different approach to testing them than I did.
Can you say what tire A,B, and C were?
I could, but I won’t. 
I’m trying to keep the focus on the more general question of tire/wheel width, in part due to the fact that the testing I do only reflects what happens at/near 0 deg of yaw.
As the owner of a 2007 808 i am wondering what tire c is?
I could, but I won’t. I’m trying to keep the focus on the more general question of tire/wheel width, in part due to the fact that the testing I do only reflects what happens at/near 0 deg of yaw.
If you are testing at 0, I’d suggest throwing in a Deep V rim as well. In ‘Keyboard theory’ it would would seem it should test better than anything… (what kind of rim is the Shamal on for that matter… I suppose it may be a deep v)
If you are testing at 0, I’d suggest throwing in a Deep V rim as well. In ‘Keyboard theory’ it would would seem it should test better than anything… (what kind of rim is the Shamal on for that matter… I suppose it may be a deep v)
If you follow the link in my blog post, there is a pic of the wheel…but in any case, yes, the Shamal is a very deep V.
As the owner of a 2007 808 i am wondering what tire c is?
Come to the next TT that I do and you’ll see (unless I find something even faster first). 
even on an indoor track the yaw angle may approach 10 deg in the turns
Hi Andy:
Can you please elaborate on how you got this?
I’ve given this topic some thought and have calculated very small yaw angles. My calculations were based on the fact that a bike pivots about its rear contact patch. If the front and rear contact patches were both on the same radius (eg the black line) the angle can be calculated based on the radius of the track’s curve and the bike’s wheel base (which would be the cord length). Based on that rationale I have calculated around 2.5 degrees. But that assumes that the bike is not leaned over all. Once the bike does lean the angle of attack (yaw) should be reduced. The extreme would be a circus performer riding essentially horizontally in a barrel.
Please let me know if my rationale is flawed in some way. Its all theoretical as I have not collected actual yaw angle data during track riding.
Cheers,
Jim
This begs the question, is Bontrager planning on discontinuing the Aerowing tt 19mm tire any time soon? Carl?
I thought the R4 was *replacing" the old aerowing.
Glad I stocked up (They are on closeout at Bonty dealers right now) already.
There’s still the SuperSonic and the S-Works Open Tubie if they do stop making them though
even on an indoor track the yaw angle may approach 10 deg in the turns
Hi Andy:
Can you please elaborate on how you got this?
I’ve given this topic some thought and have calculated very small yaw angles. My calculations were based on the fact that a bike pivots about its rear contact patch. If the front and rear contact patches were both on the same radius (eg the black line) the angle can be calculated based on the radius of the track’s curve and the bike’s wheel base (which would be the cord length). Based on that rationale I have calculated around 2.5 degrees. But that assumes that the bike is not leaned over all. Once the bike does lean the angle of attack (yaw) should be reduced. The extreme would be a circus performer riding essentially horizontally in a barrel.
Please let me know if my rationale is flawed in some way. Its all theoretical as I have not collected actual yaw angle data during track riding.
Cheers,
Jim
Just quoting Chet Kyle from his chapter in Ed Burke’s High Tech Cycling:
http://i55.tinypic.com/mmpl5j.jpg
(Note that although the legend refers to a 150 m track, the text states that the track was 250 m, which makes more sense since as you undoubtly know much of the on-track testing that Broker and Kyle did for Project 96 was performed at the Superdrome in Adelaide, Australia.)
If I understand correctly, these data were obtained by attaching some sort of angle indicator just behind the stem, and videotaping its movement using a camera mounted further back on the top tube (at least that is how they measured the steering angle data shown in Figure 1.10). As others have pointed out, no object is completely w/o mass, so the “tell” would be expected to swing outward in the turns regardless of the air flow. It is hard to imagine, though, that whatever they used would have sufficient mass that this effect would overcome the aerodynamic forces acting upon the object.
Perhaps the AIS should revisit the issue?
Glad I stocked up (They are on closeout at Bonty dealers right now) already.
I’ve got a pair for sale if anybody is interested (see the Classifieds).
(Jim: you’ve got first dibs if you still want to replace those Continentals.)
Andy,
This is excellent and very interesting. Was there any noticeable difference in the tread of the tyres or the tread/sidewall interface?
Cheers
If I understand correctly, these data were obtained by attaching some sort of angle indicator just behind the stem, and videotaping its movement using a camera mounted further back on the top tube (at least that is how they measured the steering angle data shown in Figure 1.10). As others have pointed out, no object is completely w/o mass, so the “tell” would be expected to swing outward in the turns regardless of the air flow. It is hard to imagine, though, that whatever they used would have sufficient mass that this effect would overcome the aerodynamic forces acting upon the object.
Perhaps the AIS should revisit the issue?
This sounds like a job for…“Chung on a Stick!”