The whole multivariable testing aspect is funny. Michael Hall is carrying it on in good stead in your absence.

The latest example is that I'm doing a bunch of testing on the new Tangente tires. Michael won't tell me whether or not 25mm or 23mm is faster (aerodynamically) though. Because he doesn't want knowing to bias my feedback on other aspects of the tire. Clearly, I'll want the more aerodynamic tire to also feel better. But it might not. So to keep me from being biased, I don't get to know.

I thought that was interesting. Albeit frustrating too... [:D]

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

I remember doing some rudimentary PV = nRT calculations, just guestimating the volume of a bike tire and figured that even a 70 degree swing in temperature (40 degrees in the AM, and 110 during the race) would only have about 15psi of pressure gain.

.

You sure it isn't *cold* in the belly of the plane?

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

The cargo bays are insulated, or at least all the ones I have been in. The temperature is just not as tightly controlled as the cabin. Sure if you are sitting for a long time in Dubai it will get very warm in there. I would bet big money your tire sees higher temperature on a ride on a hot day during hard braking.

Not on the ground... Sorry for not being specific.

Again, I'm not sure I agree with this. As Chaparral said, I bet you see higher swings on hot days under heavy braking. Just throwing out there that it's generally believed - rightly or wrongly - to be a temperature issue as opposed to an altitude issue when it comes to pressurized containers (or tires).

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Gotcha.
Yeah I think temperature too can expose installation errors independent of the resulting pressure increase by softening the rubber.

Anyway, I've not deflated my tires and not had problems =)

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Me neither. But Cote does, specifically because he has had problems. Maybe he just sucks at installing tires. Typical engineer...

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

maybe angry TSA guys stab them!

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

avy back packs and full cylinders are permitted under IATA rules as checked baggage - bike cylinders are not permitted, they don't have a fail safe and therefore need to be shipped as Haz Mat, declared and packaged appropriately - just like Li-ion batteries. all of this is detailed in CFR 49 - and there is or was a fairly senior DOT lurker knocking about here who could give you the long and short of it, its been 10+ years since i worked on package testing

Great articles Josh!

The part about the 3 pumps on the team truck reading so different is interesting.

Other than getting a new Silca SuperPista Ultimate pump and bringing it with you wherever you go, do you recommend any specific gauge that could be used with any pump to get accurate (or at least repeatable) measurements?

I recently got a Accu-Gage 30psi gauge for mountain biking, and it seems pretty good, but of course reads differently than all my pumps. ;-)

Also, is there a preferred procedure for pumping up your tires? Overinflate then bleed down to desired pressure, etc?

.

All 3 tires of my Bob Stroller blew when I inflated them to the max pressure and then my garage got hot in the summer. I thought the furnace blew, 3 times. I'm an idiot.

well if the max pressure really is the max, that would make sense.

usually isn't, though.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

We found that 180 pounds of pressure in a tubie:
1) will turn you into a tricep he-man
2) is a good cardio workout
3) will blow the valve off before popping the tire
4) will inherently get someone to walk over and tell you don't need that much pressure
5) will jump off a wheel if you look at it the wrong way

efernand,
the interesting things about gauges is that they are more accurate in the middle of their range than at the extremeties and in general, as I found out back in 2008, bicycle pump gauges are of a very low accuracy and precision specification. It is also notable that inexpensive digital gauges are also generally not terribly accurate, though at least they can be more precise than similar accuracy mechanical ones.

The problem on the team truck was a combination of pump gauges being +/-5% accuracy from the factory, and they are then subject to wear and tear, not to mention any mechanical gauge will be subject to fatigue as the needle is moved by the deformation of an internal component (either a diaphragm or a Bourdon tube). Inexpensive digital gauges are generally +/-3% but they experience less fatigue and are usually more precise (if accuracy is how close you are to the bullseye, precision is how close each dart is to the previous dart..so you might be less than accurate, but you are very repeatable at it..it's an important distinction) due to lack of internal friction of any mechanism.

An auto tire gauge that goes to 30 is great for Mtn and CX tires and will have good repeatability for you. In that case I recommend overinflating slightly and bleeding back to pressure. Just be sure to always use that same gauge. We had a team at Cape Epic this year using 1% SILCA LP gauges that for some reason didn't want to take their 8lb SILCA pump all the way to South Africa...but then found that the pressures on the support pumps there were all over the map and as you know, with tubeless 1psi is a BIG deal. We made the best of it by having them put a piece of hot-pink duct tape on one of the neutral pumps so that they were at least using the same one every day and by day 3 they were mostly sorted out!

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http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

it does sound like an opportunity for a little gauge R&R study - it was always the case that we had problems getting consistent repeatability in manufacturing and then we couldn't reproduce it when operators changed - one shift invariably varied significantly from another and within shifts there was significant variation - I'm guessing the same applies to pumping up tires

Mark Cote of Specialized firmly advocates deflating your tires just a bit before flying. It's a temperature issue. Your luggage is sitting in the un-insulated belly of a giant aluminum tube sitting directly in the sun often for quite a long time.

Don't rims and tire beads exceed 200F (maybe 300F?) in sustained hard braking? They can easily get over 150F just sitting in the sun if it is calm. It's hard to believe the cargo hold on a plane would be worse. It's in the belly, not in direct sun. There are no windows, so no greenhouse effect, unlike a car. Plus they are usually painted white.

I'd guess a little warmth combined with lower air pressure and a pinched tube could push a tire over the edge. At any rate, the airline wouldn't like to have things exploding in their plane.

So the temperature/pressure effect is very real, but also pretty small. The rule of thumb I always use is 2psi per 10deg F, some people say 2% per 10 deg F.. in reality it varies from like 1.6 to 2.4% over the range of pressures we are talking about here, but again, not enough to actually do damage. Clincher rims can see sustained temperatures over 300F under heavy braking in the mountains, so well beyond what they will see in the sun at transition or in the belly of a plane.

Either way, the problem is pretty much always installation related from my experience.

Like Mark I always deflate mine to about 60-70psi when I fly with the bike because that's what I was taught and it's always worked for me..but at the same time, I have no evidence of causation as to why it works or what it's doing! Sort of an outlook of 'It's never not worked, so I'll keep doing it.'

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http://www.SILCA.cc
Check out my podcast, inside stories from more than 20 years of product and tech innovation from inside the Pro Peloton and Pro Triathlon worlds!
http://www.marginalgainspodcast.cc

Recently I flew with my bike and I remembered as I was boarding the plane that I did not deflate my tires as I would normally do and was concerned at first, then after a minute I was like, "What am I concerned about again?" I went through the math in my head to convince myself that it was not an issue, but my first gut reaction was concern because normally I deflate them.

I am SOOO disappointed in both you and Mark... :-/

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http://bikeblather.blogspot.com/

actually, I deflate them for a simpler reason: baggage handling. If I happen to pack up a tire with any owner-induced damage from use, rough handling could possibly cause the tire to rupture. This, as we all know, can be a loud experience. Depending on where such an event might occur, I'd expect that the result of a large "bang!" occurring in the luggage area of an airport (in the airport or in the plane) would result in my bike case being not-so-carefully disassembled...

Huh? The only way to get a loud rupture is if the tube "escapes the containment vessel"...and if rough baggage handling is causing that, I'm thinking you're going to have bigger problems with the state of your equipment than anything security could do :-/

Heck, if anything...having air in the tires is going to help protect the rims from rough handling...

Anyway, maybe everyone who likes to perform this airing-down ceremonial ritual should just use latex tubes and not bother? Just so long as you don't top them off before packing, you should be good ;-)

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http://bikeblather.blogspot.com/

During my last trip overseas with my bike, I got two big digs in the frame from the baggage handlers going through my bike case. I did air the tires down to about 40 psi before the flight, and at the time they were butyl.

Josh, those are a great series of articles, thanks for writing them.

Question for you - I thought I read that some years ago, the ProTour teams had switched from air to noble gases because of the leakage issue. True or not?

Brian

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Brian

Gonna buy a fast car, put on my lead boots, take a long, long drive
I may end up spending all my money, but I'll still be alive

I remember Josh posting an anecdote on another thread about how, when Zipp wheels first came out, the pro tour teams were filling the tires up with helium to like 200psi or more for TTs. Dudes were crashing left and right, naturally, and so they were scarred for life thinking it was the Zipp wheels, and not the ridiculous air pressure. I think this was back when people were first trying to get the old school mechanics to let go of the old ways and teach them about the low Crr benefits of 100psi or so. I think it took a lot of teeth pulling to get them to change if I remember the story right.

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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.”

Found the post, they actually filled it to 280 psi resulting in the rims swelling and getting jammed between the fork legs, really great story:

http://forum.slowtwitch.com/...post=5091482#5091482

Josh had to negotiate them down to 220psi!