Swim Bike Run
Slowtwitch.com
  • Login >
Slowtwitch.com
Search menu
Hot Forum Topics

Poll

Comfort While Cycling
How much does comfort while cycling influence your overall race performance?
View Results


Home > Forum > Triathlon Forum > Chung testing Veloflex Records

Triathlon Forum

Back To ForumPrint Thread

Login required to started new threads

Login required to post replies

Prev Next
Tri
Classifieds
Lavender
Jobs
Notices
Chung testing Veloflex Records
Quote | Reply
Rob84
May 9, 22 16:19
Post #1 of 51 (4340 views)
Long time ST lurker here with a question & an idea…

I’ve been looking for the fastest tire to try and optimize my 40k time.

Has there been any further CRR data on the Veloflex Record vs Corsa Speed 2, since Aerocoach and BRR posted conflicting results?

BRR:
7.3 watts per tire with latex tubes, 120 psi,
94 lbs load
Also 11.4 watts at a more realistic 80psi, using less realistic butyl tubes
https://www.bicyclerollingresistance.com/...iews/veloflex-record

7.0 watts for 25mm version, latex tube
8.4 watts for butyl tubes, 80psi
https://www.bicyclerollingresistance.com/...toria-corsa-speed-g2

Aerocoach:
Records are 16.5w
23mm Corsa Speed 2 is 21.4w.
Tested at 27mph
https://www.aero-coach.co.uk/...ling-resistance-data

I’ll link to the larger discussion on this, but I don’t think any reason for the difference was resolved:
https://forum.slowtwitch.com/...a_Speeds_P7339645-4/

I have a pair of both tires in 23mm and have a great spot where I’ve been doing Chung testing for the post year. I was thinking about doing a test to compare CRR of these.

The .5 mile stretch of road with hills at either end has a variety of different road surfaces. Not awful, but lot clean either.

It would be a pain in the butt to do this test. I’d have to switch tires in between runs, probably multiple times, and also do all the things necessary to get a high precision Chung run:
- windless day
- super consistent position
- ride the same path over the pavement every time

I’d also have to confirm tire width & profile are similar… I recall a comment on Slowtwitch (maybe Xav?) that these tires had similar widths & profiles, though I can’t find it now… I’d have to measure, but assuming the widths are close I’d call this a wash… and fast/slow runs should help to see out any significant changes in CdA.

With all that said, I’ve been Chung’ing a good bit, and when everything is right I can be reliably consistent runs to capture differences of .002 CdA, or less than 2 watts at 25mph.

I’ve read the idea that that real road conditions amply tested CRRs from BRR around 30%. And I’ve done basic lo-fi Chung testing that supports this (I measured 23mm GP5000 to be .380 at 80psi, vs. .321 from BRR). So if the real world difference between the tires is anything remotely like Aerocoach measured, +20 to 30 percent, then I should definitely be able to see it, even with the challenges above.

Especially if I do both fast & slow runs to separate out CdA and CRR.

This answer is a big deal, I think, since we’re talking about the “fastest” road tire. And because people like me are spending time, money, and risking flats to ride the Veloflex when there are conflicted results about the benefits.

Looking for feedback from the community on the proposed test. And also if more data on the tires is available that I’ve totally missed. There’s other stuff I’d rather do if this isn’t necessary!

If I end up doing the test and get something usable, I’ll post the results here as a new data point on these tires.
Last edited by: Audioslave784: May 10, 22 4:34
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
realbdeal
May 9, 22 16:39
Post #2 of 51 (4324 views)
As far as I'm aware the reason for the discrepancy is pretty well settled:

The early models had a completely smooth tread and then at some point after the Aerocoach testing came out they swapped the tread design to something with more texture. I ordered a set within a few weeks of seeing aerocoaches testing and got the ones with the slower tread. Meant to complain about that to them but never got around to it. Haven't even mounted them because of that. Pretty obnoxious move on their part.
Benjamin Deal - Professional - Instagram - TriRig - Lodi Cyclery
Deals on Wheels - Results, schedule, videos, sponsors
Quote Reply
Re: Chung testing Veloflex Records [realbdeal] [ In reply to ]
Quote | Reply
IKnowEverything
May 9, 22 17:00
Post #3 of 51 (4304 views)
I’ve got a set of unused smooth tread/OG records if you are interested!

Two sets actually, but thinking I’ll keep one. But who runs 23mm these days?
___________________________________
MS: Exercise Science
Your speed matters a lot, sometimes you need to be very fast, where sometimes you need to breakdown your speed.
Quote Reply
Re: Chung testing Veloflex Records [IKnowEverything] [ In reply to ]
Quote | Reply
realbdeal
May 9, 22 17:51
Post #4 of 51 (4273 views)
Hmm I may be. I mostly picked them up for races like Daytona or Miami where the surface is predictably smooth. On my 25mm wheels the 23s are still a good match!
Benjamin Deal - Professional - Instagram - TriRig - Lodi Cyclery
Deals on Wheels - Results, schedule, videos, sponsors
Quote Reply
Re: Chung testing Veloflex Records [realbdeal] [ In reply to ]
Quote | Reply
Rob84
May 9, 22 18:19
Post #5 of 51 (4247 views)
Somewhere in the 5 page linked thread, Xav says he tested the new version and updated his page with the new test results. So both tests are with the latest version.
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
Rob84
May 9, 22 18:23
Post #6 of 51 (4244 views)
Found it, see page 4 of 5:

https://forum.slowtwitch.com/...a_Speeds_P7339645-4/

Xavier:
“Update:

The difference between the smooth Veloflex Record and the textured is ~0.000063 Crr, in favour of the smooth Record. Both are still significantly faster than Corsa Speed, Michelin Power TT etc., as the gap between the Record and the Corsa Speed is ~0.000475 Crr. At 45kph for a 75kg standardised rider therefore a pair of textured Records is around 0.6w slower than smooth (a pair of Corsa Speeds is nearly 5w slower). So IMO no need to worry which version you have, but if you have a smooth one then happy days. “
Last edited by: Audioslave784: May 9, 22 18:25
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
MTM
May 10, 22 1:51
Post #7 of 51 (4151 views)
It would be an interesting test for sure. I think the Records are 1-1.5mm narrower than the Corsa Speed 23mm, so you'd also have to find out what kind of pressure to choose for each to make it a fair comparison. Aero drag differences on a low wind day will probably be close enough to be considered negligible. I'd probably just stick to testing at a reasonable speed that isn't too far off race speeds. CdA is not unlikely to vary with speed, and I wouldn't be surprised if Crr also has a bit of a speed and torque related component, so with tyres so close in performance I'd focus on whatever is fastest at the target speed.
Quote Reply
Re: Chung testing Veloflex Records [MTM] [ In reply to ]
Quote | Reply
Rob84
May 10, 22 7:30
Post #8 of 51 (4045 views)
MTM wrote:
It would be an interesting test for sure. I think the Records are 1-1.5mm narrower than the Corsa Speed 23mm, so you'd also have to find out what kind of pressure to choose for each to make it a fair comparison. Aero drag differences on a low wind day will probably be close enough to be considered negligible. I'd probably just stick to testing at a reasonable speed that isn't too far off race speeds. CdA is not unlikely to vary with speed, and I wouldn't be surprised if Crr also has a bit of a speed and torque related component, so with tyres so close in performance I'd focus on whatever is fastest at the target speed.



That’s a good point. Portions of the test at very different speeds shouldn’t be combined and compared against one another.

The issue with just doing race speed runs however is that at higher speeds, you have a poor signal-to-noise ratio when looking at CRR. Lower speeds amplify the effect of CRR vs aero.



I’ll aim to do a set of runs at specific speed profiles. One profile will be slow speed to aplify CRR differences, and the other at race speed to validate the result in a realistic use case. Hopefully the % difference holds, but if not, that’s important to know and try to explain.

I think I’ll use power and timing to get relatively consistent runs.

The high speed test might look like: roll down the first hill from Point A, pedal around 200 watts until Point B, cruise until turnaround on the second hill at point C, etc.

The low speed test would probably use a shorter duration 200 watt impulse.

Note: CRR seems to vary somewhat consistently at speed per a newer BRR test, around 10% between 9 and 22.5 mph… the GP5000 was an outlier at 6% CRR change but it all may be within test error.
https://www.bicyclerollingresistance.com/specials/crr-speed-test

So I think I’d plot VE at the higher speed run using CRR of +X% based on the average speed of the higher vs lower speed run. X would be a percentage based on assuming linear 10% increase in CRR between 9mph and 22 mph. There will be some fudging here, but hopefully correcting by this rough order of magnitude will be “good enough”. Especially since we’re looking for precision in comparing 2 tires and not accuracy in absolute CRR.
Last edited by: Audioslave784: May 10, 22 9:00
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
grumpier.mike
May 10, 22 9:17
Post #9 of 51 (3998 views)
If you are really only interested in Crr then you could do all the testing on a pair of rollers. The simplest test is to put the different tires on similar front wheels and ride at a constant speed on the rollers. You can then compare the average wattage for each tire, after you let each tire warm up. The nice thing about rollers is that they exaggerate the wattage difference between tires (I think the difference is a factor of 3ish), so it is pretty easy to pick the tire with the lowest Crr.
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
MTM
May 10, 22 12:17
Post #10 of 51 (3939 views)
Why not just lock CdA at some roughly correct value and solve for Crr for all runs? Best not to include and/or assume any stuff in the calculations. Check assumptions afterwards in the results.

If you want to know Crr by itself a better way than varying speed would be adding weight (without adding aero drag).
Quote Reply
Re: Chung testing Veloflex Records [grumpier.mike] [ In reply to ]
Quote | Reply
MTM
May 10, 22 12:20
Post #11 of 51 (3938 views)
grumpier.mike wrote:
If you are really only interested in Crr then you could do all the testing on a pair of rollers. The simplest test is to put the different tires on similar front wheels and ride at a constant speed on the rollers. You can then compare the average wattage for each tire, after you let each tire warm up. The nice thing about rollers is that they exaggerate the wattage difference between tires (I think the difference is a factor of 3ish), so it is pretty easy to pick the tire with the lowest Crr.
While roller testing is great, it doesn't give the complete picture. My hunch is that is a big part of why we're seeing discrepancies in the Veloflex Record results.
Quote Reply
Re: Chung testing Veloflex Records [MTM] [ In reply to ]
Quote | Reply
Rob84
May 10, 22 13:00
Post #12 of 51 (3915 views)
I’m thinking that too. Aerocoach blog states that rollers & velodrome were used, so I’m assuming all the testing was on a smooth surface. But I don’t know the details here, more detail on the test world certainly be useful.

BRR has a textured drum. It’s not a road but they seem to be rigorous and I imagine there’s some validation off ok method. They use butyl for some tests, which is always a confounding factor. But they did put a latex tube in the Record for one test at 120psi. Not that anyone rides one them at that pressure, especially outside of a perfect surface.

Chung testing on a mixed road surface at typical pressures is a unique data point among these other tests.

It’s also a test with far more transparency into the method. For myself, I’ll personally have witnessed the test, understood the process, and thought through any shortcomings. But I also want to be as open as possible when documenting the test publicly. It feels like a good thing to bring to the community and it’s helpful to crowd source feedback on the method & results.
Quote Reply
Re: Chung testing Veloflex Records [MTM] [ In reply to ]
Quote | Reply
Rob84
May 10, 22 14:17
Post #13 of 51 (3875 views)
MTM wrote:
Why not just lock CdA at some roughly correct value and solve for Crr for all runs? Best not to include and/or assume any stuff in the calculations. Check assumptions afterwards in the results.

If you want to know Crr by itself a better way than varying speed would be adding weight (without adding aero drag).

Let’s see, I’m going to try and work out this out…

If CdA is off, then any error in grams calculated vs actual is then assumed to be due to rolling resistance.

So if a CdA is chosen that’s slightly lower than actual, then the CRR will read high, because VE will account for those grams of drag to rolling resistance.

The additional grams of drag allocated to CRR in error would be equal for the Corsa & Record tires… ASSUMING that the runs were done at the same speeds.

Normally VE is handy because if you have all your variables, you can do each run at any speed. But because CdA is such a big contributor to total drag, small errors in CdA will have a big impact on the CRR result. And the delta is not consistent between runs unless speed is controlled for, because grams of drag is exponential with speed while CRR is linear.

So back to your comment - I think that a ballpark CdA will work if speeds are consistent (ballpark) on each run. This will keep the error in CRR consistent between runs using Corsa and Record.

It’s a different thought process than when determining CdA, where you can just have a ballpark CRR and not care about speed, because CRR is a much lower portion of the total drag than aero.

Though I’m far from sure, I’m feeling like low speed runs will be the main source of good CRR data. At lower speeds CRR will not be dwarfed by CdA, so errors from ballparking the CdA will not blow up the results as much.

Though as you pointed out, high speed runs will be more representative of real world use. And I can get a pretty good high speed CdA estimate using Chung method with known tires (I usually set Corsa Speeds to .320), whereas low speed CdA is more guesswork.

At the end of the day, I’m thinking I’ll control for speed, run separate high and low speed tests, and see which data is more useful.
Quote Reply
Re: Chung testing Veloflex Records [MTM] [ In reply to ]
Quote | Reply
Rob84
May 10, 22 14:47
Post #14 of 51 (3852 views)
MTM wrote:
Why not just lock CdA at some roughly correct value and solve for Crr for all runs? Best not to include and/or assume any stuff in the calculations. Check assumptions afterwards in the results.

If you want to know Crr by itself a better way than varying speed would be adding weight (without adding aero drag).

I may be over-thinking all this. What if we assume CRR of one tire (e.g. Corsa Speed at .320), then determine CdA from that, then use that CdA for the Record. Keep speed relatively consistent between runs so that any errors due to any one variable being off are consistent between runs. That way we get a good delta CRR even if the Corsa Speed CRR guess is off and/of the estimated CdA is off.

Hmm, how would one calculate CRR by adding weight? It makes sense but I’m not sure of the math.
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
MTM
May 10, 22 15:04
Post #15 of 51 (3842 views)
Audioslave784 wrote:
MTM wrote:
Why not just lock CdA at some roughly correct value and solve for Crr for all runs? Best not to include and/or assume any stuff in the calculations. Check assumptions afterwards in the results.

If you want to know Crr by itself a better way than varying speed would be adding weight (without adding aero drag).


I may be over-thinking all this. What if we assume CRR of one tire (e.g. Corsa Speed at .320), then determine CdA from that, then use that CdA for the Record. Keep speed relatively consistent between runs so that any errors due to any one variable being off are consistent between runs. That way we get a good delta CRR even if the Corsa Speed CRR guess is off and/of the estimated CdA is off.

Hmm, how would one calculate CRR by adding weight? It makes sense but I’m not sure of the math.
That sounds like a good approach.

If you add only weight, the VE curve should look exactly the same if you just adjust the weight in the calculations between the setups. If it doesn't, the Crr is off (assuming everything else is kept the same of course). Probably need a good bit of weight, though. Guessing at the very least 10+ kg.
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
marcag
May 11, 22 13:11
Post #16 of 51 (3735 views)
Try to avoid big temperature swings, make sure you measure temperature frequently and remember to warm up the tire before testing.
Quote Reply
Re: Chung testing Veloflex Records [marcag] [ In reply to ]
Quote | Reply
Rob84
May 11, 22 13:56
Post #17 of 51 (3716 views)
marcag wrote:
Try to avoid big temperature swings, make sure you measure temperature frequently and remember to warm up the tire before testing.

This I hadn’t considered. I’ll have to be extra careful with temps since they’ll impact not just drag measurements (rho) but also CRR. Have to consider:
- sun loading
- changing air temps
- heat from rolling?

I’ll be doing this in the morning to minimize wind so maybe I’ll go even earlier to avoid sun (and hopefully cars) altogether. Air temps will be recorded carefully, hopefully they don’t drift much.

I have a cheap IR thermometer that should help with all this. I’ll take a tire surface reading before each run.

Do you (or anyone) know to what extent road tires warm up when ridden? Hopefully this is negligible.
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
marcag
May 11, 22 14:07
Post #18 of 51 (3702 views)
Audioslave784 wrote:
marcag wrote:
Try to avoid big temperature swings, make sure you measure temperature frequently and remember to warm up the tire before testing.


This I hadn’t considered. I’ll have to be extra careful with temps since they’ll impact not just drag measurements (rho) but also CRR. Have to consider:
- sun loading
- changing air temps
- heat from rolling?

I’ll be doing this in the morning to minimize wind so maybe I’ll go even earlier to avoid sun (and hopefully cars) altogether. Air temps will be recorded carefully, hopefully they don’t drift much.

I have a cheap IR thermometer that should help with all this. I’ll take a tire surface reading before each run.

Do you (or anyone) know to what extent road tires warm up when ridden? Hopefully this is negligible.

A member recently did a similar test to what you are trying. He used this to capture wind, temp, humidity, baro pressure.

I always warm a tire up 15min from cold, and 5min if I stopped for an equipment change
Quote Reply
Re: Chung testing Veloflex Records [marcag] [ In reply to ]
Quote | Reply
Rob84
May 11, 22 14:30
Post #19 of 51 (3692 views)
marcag wrote:
Try to avoid big temperature swings, make sure you measure temperature frequently and remember to warm up the tire before testing.

I dug up a few details on temps & tires:

Flo blog says that tire pressure increases 1.8% for every 10 degrees F. I doubt runs will be more than 30 minutes apart, which (assuming minimal sun loading) should be
https://blog.flocycling.com/...ure-and-temperature/

Velo News interviewed Oliver Kiesel, tire designer and product manager for Specialized about temps & tires, some relevant points:

“We never worked on this extensively, but we did a short study today and came to the conclusion that the air temperature doesn´t change the tire pressure crucially.

…

Tires on bicycles don´t heat up too much. They are not heavily loaded and don´t run with high speeds.

There is also cooling air all the time. They mainly run just with the regular air temperature; even if they would run 10°C [18°F] higher, the pressure increase is not crucial to the ride quality or performance.“

Also, a couple of sources have said CRR increases 6-8% for each 10 def F (though they don’t cite their sources).
https://ridefar.info/...nmental/#temperature
https://fitwerx.com/...in-the-cold-weather/

I don’t expect air temps will differ by more than 1-2 def F max between runs, assuming no more than 1/2 hour between runs so both CRR and pressure changes due to temp should be minimal.

I think temps should be sufficiently controlled by:
- IR tire temp readings on the tires before each run
- a few minutes ride after mounting a pair of tires to generally get things settled in
- recording air temperature before each run
- doing both runs in the morning with minimal sun loading
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
marcag
May 11, 22 14:37
Post #20 of 51 (3686 views)
I assume you'll do some type of A B A test and if temp does impact you will see it. IME it does. Pressure is only part of the equation. I have heard many opinions that ambient was best, others say road temp is best, others say tire temp is best. Ambient is the easiest to measure.

Tom A had a chart at one point. IIRC 4 deg C swing in ambient temp was a 5% difference in CRR (by memory)
Last edited by: marcag: May 11, 22 14:39
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
MTM
May 11, 22 14:50
Post #21 of 51 (3679 views)
Maybe also measure tarmac temperature. You will also have some kind of indication on temperature changes on your head unit file. I would think tyre temperature tracks decently close to air after riding a short while.

Temperature does indeed affect Crr.
Quote Reply
Re: Chung testing Veloflex Records [MTM] [ In reply to ]
Quote | Reply
Rob84
May 11, 22 19:56
Post #22 of 51 (3618 views)
I’m thinking more and more that I’d be best of doing this at some ungodly hour in the morning. Like starting at 3 or 4 AM. You can get really consistent air temps (often unchanged hourly forecast), really low wind (under 3 mph reported), and perfectly consistent sun (zero).

No cars or pedestrians is a bonus. I’m sure so can find places to mount lights.

It’s a suburban street lined with houses, so anyone who’s up might reasonably wonder what in god’s name someone is up to riding a weird looking bike in the middle of the night, wearing a skin suit, in an aero tuck, rolling back and forth on their half mile street at 10 mph.

But all in the name of science, right?
Quote Reply
Re: Chung testing Veloflex Records [IKnowEverything] [ In reply to ]
Quote | Reply
Ohio_Roadie
May 11, 22 20:48
Post #23 of 51 (3607 views)
Hmm 23mm works perfectly on an outdoor 333m concrete track for nationals. If you want to sell one, I know a guy looking for a fast tire.
Quote Reply
Re: Chung testing Veloflex Records [Audioslave784] [ In reply to ]
Quote | Reply
marcofoils
May 12, 22 0:59
Post #24 of 51 (3561 views)
Attached a plot as incentive to ride the same line every time to the best of your ability. This is not some extreme example with chunks of asphalt missing by the way. In a blind test, you would need to concentrate to feel the difference, yet it clearly shows in the FFT of the acceleration signal.


Last edited by: marcofoils: May 12, 22 1:02
Quote Reply
Re: Chung testing Veloflex Records [marcofoils] [ In reply to ]
Quote | Reply
Rob84
May 12, 22 7:48
Post #25 of 51 (3494 views)
marcofoils wrote:
Attached a plot as incentive to ride the same line every time to the best of your ability. This is not some extreme example with chunks of asphalt missing by the way. In a blind test, you would need to concentrate to feel the difference, yet it clearly shows in the FFT of the acceleration signal.


Interesting. I’m assuming the “Raw accelerometer output” is voltage (mv?) with a linear correlation to Gs.

To me this chart raises the question: how do these vibration differences correlate to differences in average CRR over the courses? Do these 2 paths reflect a 0.1% difference in total tire-ground losses or a 10% difference?

I’m thinking the magnitude of CRR difference between those courses depends on whether or not the bike was in a tire pressure / surface roughness zone where impedance / vibration losses are significant compared with losses from hysteresis.

The attached chart (from https://silca.cc/...=e25396f57&_ss=r ) shows how impedance losses are insignificant, until psi rises to a certain point; and suddenly they matter a lot.

So maybe the takeaway here is that the test should be run using the a lower pressure to minimize the magnitude impedance losses, and thus minimize the difference in impedance losses between runs.

I had been planning to run ~88 psi, as that’s what I usually race at. But maybe I’ll go with the value recommended by the HED chart (here: https://www.slowtwitch.com/...e_Pressure_7410.html ), which I know has been criticized for being too low for optimal speed compared with other guides, but I’m sure they had their reasons (comfort, grip, etc.). I’m 155 lb so their chart has a 23mm tire at 72 psi.

That should do the trick as far as controlling differences impedance losses.

Also, a more straightforward control, I’ll be marking waypoints using chaulk to try and get each run as consistent as possible.

Keep the input coming!
Last edited by: Audioslave784: May 12, 22 15:19
Quote Reply
Prev Next
Back To ForumPrint Thread

Our Partners

transition-DOT-area-AT-slowtwitch-DOT-com

Advertise with us

©1999-2024 Slowtwitch, Inc., and Slowtwitch.com
Reproduction of material from any Slowtwitch.com page
without written permission is strictly prohibited.