I think this is the fixed link HERE. Thanks. Good info.

Hmm. Must have fumbled something in iOS interface. I think it’s fixed now. Thanks!

Awesome. Supports my choices, but i was surprised it was 7w for two wheels.

I had just asked brr.com to do the same test. Not needed now...

7 watts at 45kph/28mph. Unless you're a monster, you're probably not averaging 45kph on any rides. As the relationship between speed and .crr is linear, however, you can pretty easily figure what the watt savings are for your typical average speed.

FWIW, brr.com did a similar test (without the Tubolitos) using Shwalbe tires and found ~1.8 watts* per tire at 29kph. Using extrapolation, that would be 2.8 watts @ 45kph, then double it for two tires to 5.6 watts. So the Aerocoach results, while slightly larger, are in the same ballpark and no real surprise.

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"They're made of latex, not nitroglycerin"

I "think" the discrepancies come from the size of testing surface. BRR uses a large diameter drum, whereas Xavier was using a standard roller setup. There's going to be more deflection on the rollers than the drum.

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Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook

Thank you for sharing this.

No worries. We should all probably be thanking Xavier for participating here and continuing to test things we all wonder about and then sharing the results in the public domain!

It would have been nice if they tested the S-Tubo Road race tubes for comparison. They are 23 grams and thinner. It would be nice to see if they had a crr closer to latex

Thanks for the kind words!

We didn’t test the S Tubo as they’re not rim brake compatible, so wanted to keep everything consistent across the different tubes.

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AeroCoach UK
http://www.aero-coach.co.uk

I have been running the ARC chainring and chain catcher---awesome pieces. Thanks.


Also, I don't think these speeds are crazy to test at. I average 25mph in a 70.3 and more in an Oly and way more in a TT and I'm a not particularly good 40 some. There are certainly faster riders than me out there.

Thanks for testing! Have you compared amongst latex tubes? Vittoria, Michelin, Silca, etc. or should we assume they're all effectively the same?

I do understand the reservation about 45kph, but in the UK (which is a fair proportion of our target market) that’s actually a little slower than people would prefer as lots of people are shooting for 48kph/30mph for TTs these days. So we feel 45kph is a good compromise and doesn’t inflate things too much. It’s also our standard wind tunnel airspeed for things like wheels and riders so it’s keeping things consistent as much as possible. We should probably be giving more extrapolated data at lower speeds though (like 30kph), I’ll work on that!

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AeroCoach UK
http://www.aero-coach.co.uk

We’ve not tested the Silca tube, that might be a nice comparison - Challenge as well and Vredestein too. We use Vittoria just because we find they’re fast, inexpensive and we can supply them with other Vittoria tyres that we spec on our wheels.

We don’t recommend using the Michelin tubes (I think the Bontrager latex tubes are Michelin rebadged?) as they tend to fail at the base of the valve stem. But they are also fast.

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AeroCoach UK
http://www.aero-coach.co.uk

Heya Xav

I love the testing that you do but am really struggling with something you've put in this latest report...

"At 45kph, the difference between the fastest and slowest inner tubes would equate to around 11sec over 16/km/10 miles"

How is that possible? At 45kph the time it takes to travel 16km/10 miles will be the same, every single time (21 mins 20 seconds), because the speed is the same. You've set the constant as speed, and the variable as time. They're the same thing. Whilst I know special relativity means that time is perceived differently when travelling at speed, it doesn't really apply at 45kph! As I understand it, you're saying that it will be slightly easier to travel 45kph with the fastest inner tube, or, for the same effort, you'll go ever so slightly faster than 45kph (by my calcs, based on what you've written, 45.4kph).

It just seems, to me, that if we're going down the road of precision (where you are measuring crr differences to 6 decimal places), the language used needs to be precise too. Otherwise, to me, it sounds like the kind of marketing spiel thrown out by the likes of Specialized and Zipp where, if you were believe what they write, I could have their wheels, frames and tyres and the bike would actually transfer wattage back to me to go 50kph!

I know it's nitpicky, but that's kind of the point!

No problems here with Michelin tubes but since they come with a slightly shorter valve stem they make for an easier pump adapter fit inside the front AEOX 75 that I've got...

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ZONE3 - We Last Longer

Yes quite right - but people like to hear time savings rather than speed increases, so you have to set a rough speed at which you're going to see those time savings. Appreciate the language being not as precise, it is a valid point :D

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AeroCoach UK
http://www.aero-coach.co.uk

I think "base of stem" failures are mostly caused by not pushing (or pulling) the stem tight to the rim before inflation. If you don't the tube can sneak into the gap. At least I stopped having those failures with any tube when I started being more careful; that was probably 8 years ago.

Years ago I had some very thick Vredestein latex tubes that weighed ~120g as well as their 50g ones. I couldn't tell a difference between them on rollers. I think the latex material is so good at returning energy that the loss is nil, even with a thick tube.

Can you expound on this? The only time I get failures on latex tubes is at the valve area...

I used to get Stan’s Babies failures after a long time but I stopped using sealant in training and now don’t have that problem.

Thanks
Eric

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Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”

If you check out the results from the Montreal Esprit, you'll find people well over 40kph average in the 50+
So 7 watts might be usefull.

This would be an old monster. 40 K record.

60+51:54.47Gary PainterLoyalton, Calif., 6/12/16

wow ... is that for real? i used to be a pretty serious tt'er. most courses i've seen in races have enough elevation, crappy pavement, sketchy turns, etc, that 48 requires massive talent. but you say in the UK that's fairly normal? do you mean for pros?

To be clear, I wasn't trying to be critical of the chosen speed. Given your primary target audience (TT racers) and the fact that it's your standard aero testing speed, it makes perfect sense. I was simply saying that the "7 watts difference" needs to be understood in that context, and that you adjust to your personal average speed. And let's not kid ourselves, 45kph for triathletes is way out there on the pointy end of the bell curve. There were almost 2300 finishers at the USAT Olympic Distance National Championship, and I couldn't find one who averaged 45kph.....even taking out the wonky first 1.1 mile split (which appears to have included T1).

To go from 40kph to 45kph requires somewhere in the neighborhood of 35-38% more power. 5kph difference in speed, gigantic difference in the athletic capacity necessary to achieve it....especially on the bike leg of a triathlon. For those of you who are there, congrats, you're monsters in my eyes. For those that are close, you're damn fine athletes, too. Far from the norm. But even if you can hold 43kph, you're still 12-13% short of the power needed to hold 45.

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"They're made of latex, not nitroglycerin"

Failures IME are caused by the tube getting stuck under the valve (the reinforced part around the valve), because this area isn't tight to the rim when you first start to inflate. The weaker part of the tube (next to the reinforced area at the base of the valve) will fill that gap and get stuck under there, and stretch and distort.

If you've properly installed the tube then it should have enough pressure for shape (it won't be completely deflated). Make sure you don't have wrinkles or folded spots in the valve area before you put the last bit of bead on the rim. After you attach the air chuck to the stem, pull it down so that the base of the stem is tight against the inside of the rim, as you give it a few squirts of air. Once there is a few PSI in the tube, you don't have to hold it anymore.

This for me exactly. I have had 3 latex flats in my lifetime of latex. 2 were in my house during initial tube & tire installations, in which the tubes blew at the edge of the stem reinforcement. Then, I figured out that I was shoving the tube into the rim at inflation and creating that gap that leads to failure. The third was on a mega descent when I had VeloPlugs instead of rim tape.

If the VeloPlugs are loose at all then you can have issues. I ended up putting a little crazy glue on the edge of each veloplug to keep it in place and no issues after. Just depends on the hole diameter in the rim vs veloplug size. I was using yellow and they were still just a touch too small.

Always latex for racing and Conti Race28 light for training. Works for me.