Part 3

http://silca.cc/...-invented-the-future

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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

A really terrific read! Bravo, Josh!

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AndyF
bike geek

Very cool.

Great read!

I'd like to know what they found for power vs psi on smoother parts of the road... but then I still want that pony, too...

That's a fine article - thanks for pointing it out!

Josh Poertner is one of the most perceptive and intelligent minds in cycling. Everytime he writes, I feel I'm so much closer to the action.

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AndyF
bike geek

Great article!

Fantastic! Still need to read pt 3, but so for in impressed. Also, this shows all the people asking for tire pressure advice what's what :)

Thanks everybody for all the kind words. Every time I write something like this I go back and read it and think about what a hopeless writer I am..so happy to see that the stories overcome my technical inadequacies!

I've been answering some questions over at the SILCA Facebook page, but if you have any you can post them here, I certainly don't know everything, but we work with so many teams that we know a lot and now that the race is over, can actually talk about a lot of it!!

Josh

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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

Really great read. Thanks for posting.

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I ride:
Cervelo - P-Series/R3
GT - Sensor Carbon Expert

Supporters - Flo Cycling, Mount Bikes

That was really interesting - I've a question about the experimental design, did you use multi-factorial experimental design or a single factor at a time? did you set out a methodology to work this through at the outset? I've wondered about this with bike design in general.

Great question, the answer is both! For this particular project the first year was really spent just trying to understand the problem at hand. One major issue in the bike industry is that there is little to no shared data, and very few things have test standards that are really all that meaningful. This is good and bad because on one hand it lets tiny manufacturers who are building in their garage innovate and get to market without the crushing overhead of having to meet hundreds of standards, but for something like this, there was really zero data out there on what we were facing.

So our initial approach was incredibly single factor focused: we thought that we could make a stronger rim and that would do it. That very clearly did not work, so then we re-organized to use multiple teams each looking at single factor. The reasoning was that we could more quickly build up our directionals and magnitudes in this way. One great example is the conventional wisdom that larger tires are stiffer at the same pressure, and that higher pressures make for stiffer tires, and the combination would lead to higher impact energies being absorbed before bottoming on the rim.. all seems logical, but there was literally NO data anywhere on this so while we all felt it to be true, we had no knowledge of the order of magnitude of the effects..so one team worked just on that.

Ultimately the internal three teams converged with their piecemeal data and we approached with a multi-factorial approach for final refinement and creation of the ultimate envelope of functionality.

As an industry we are struggling greatly with this because of the way things are increasingly being developed as very highly optimized systems, yet we as consumers and users still want the ability to further customize or modify as we please. Nowhere is the risk as great as in disc brakes where there have now been numerous instances of pretty bad injury resulting from people wanting to break apart a system to use a lighter disc, or performing a hardware modification without understanding how things like mass can affect temperature. This is the same way the team that first year thought, 'the wheels worked great' after successful testing with 27mm tires and thought nothing of putting on 24mm tires for Magnus, so there is a movement coming to get people thinking more in a multi-factorial way than we have previously done.

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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!
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thanks for that - its been written on here before about "blind" tests of frame materials v's tire pressures, but "this" (your experience" with PR) seems to have presented an opportunity to take the accepted wisdom and blow it out of the water, the aerodynamic properties of tire size, rim depth and pressure.

So we see the trek's (its the only one I know of) with the compound that apparently improves compliance, and the new pinarello ridden by BW and Sky, but I think your experiment shows that putting improved comfort down to a change in a single factor fails to understand the complete system and I wonder how many of the manufacturers are doing / or doing multi-factorial experimentation with changes in tech e.g. you add the compound to the frame and test against a variety of rim widths and depths and associated tire pressures and determine whether changes in compliance are measurable - and I wonder if they really are measurable.

Thats really interesting work - that and the fact that no bike pumps appear to be accurate, which could explain the loud popping sounds you hear on race mornings as it warms up and everyone thinks they've inflated to X bar.

There are realistically 5-6 companies that are really looking at system integrated design and performance, and from these, I believe we are going to continue to see a drive toward the multi-factorial design approach that you reference. The problem with this, of course, is that we will ultimately lose some of the overall customizability of the total system which might be good or bad depending on how you look at it.

The compliance changes are definitely measurable and meaningful, but only in the systems that are done right..which is to say that we still have some issues with connecting benefits to features that may or may not be present in a given design. For example, on the compliance side of things, the Canyon 'aero' bike that Kristoff won Flanders on has a rear vertical spring rate that measures out comparably to many other company's 'endurance road' bikes.. so given the choice, most people would pick the 'endurance road' bike for the comfort because nobody has published the data to say that this aero road bike is similarly compliant. In this way, we have some aero road bikes that are as comfortable as other companies endurance bikes and some company's endurance bikes that are or aero than other company's 'aero' bikes... makes things kind of difficult, no?

On the popping sounds you hear, this is due to inner tubes being pinched rather than tire pressure increases due to sun and temperature. I've studied this 100 different ways, and if I take a wheel with properly installed tube, I can put it in a refrigerator, set the pressure at 100psi, and then move it to a 350F oven and not have an issue. We have tried in the lab to replicate this many, many times and cannot do it. I'm actually working on a paper discussing this, but from experimentation, I would estimate that nearly 100% of those race morning flats are caused by pinched tubes...and some of those I would bet come from rolling bikes around on deflated tires in an attempt to solve this problem in the first place!

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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

I really appreciate your sharing all this information, Josh! So much of cycling tech is hampered by myth and legend, and it's great to see some real and thorough tests results that are made available to the public.

Did you by any chance look at the effect of tire pressure on resistance in the smoother part of the course? I know it would be a small factor and not what you were focused on, but I'm still curious.

very interesting

as an aside why would you roll a bike around on a flat tire - I don't want to appear to be an idiot, but I was taught, insert tube, partially inflate sufficient to stop pinch, tire on the other side, work you way round the tire to make sure the tubes not caught between tire / rim and then inflate - who's rolling around on flat tires

that comment about Canyon's interesting - years ago I had a CAAD 3 - horrible bright yellow thing - which I would swear was the most uncomfortable bike I'd ever ridden - with the benefit of hindsight it was far more likely it was tire size pressure related than the frame alone, but everyone swore that they were the stiffest harshest rides known to man - I wonder though.....

I also wonder then about the difference in ride between the Canyon Ultimate AL and Ultimate CF as consumers we make assumptions about the CF v's AL argument but I wonder how much water it now holds.

The industry needs a degree of accepted standardisation - historically anaesthetic machines from different manufacturers had dials which if turned left on one would change a setting and right on another would change a setting in exactly the same way - that obviously caused problems if moving between theatres and kit - it does not seem beyond the wit of man to have a degree of standardisation.

Anyway, thanks for the info

Andrew

Carbon schmarbin, give me a Nemesis rim an FMBm 28 and the extra 1,000 Euros I saved on a fancy wheel and I will ride the cobbles all year and next.

Hi Josh, truly amazing articles! And thank you for sharing those stories with us.

My question is do you mind if I translate them into Chinese and share them in Asian(Chinese speaking countries) on multiple social platforms? For sure I will give you credit!


-Simon

Interestingly, Sagan rode a Tarmac with 24 mm tires for the first 100K of this year's race and then switched to a Roubaix with 30/28 mm tires and low pressure once the cobble sections started. I don't know if other riders used the same tactic.

Because if you believe the myth that morning sun will pop your tires, you might roll into transition with the tires deflated, waiting until the sun is up before inflating.

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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

seriously, you'd (not you) believe a tire with a pressure range of 20-30 psi or more, people believe that if it had 25 psi in it, that the sun could raise that to 100 and burst it? thats nuts.......

very common belief
another one is that you have to deflate your tires before putting it on an airplane.

if you pumped your tires to 100psi and sent it into orbit the pressure would only rise to 114 =)

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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

Interestingly, Sagan rode a Tarmac with 24 mm tires for the first 100K of this year's race and then switched to a Roubaix with 30/28 mm tires and low pressure once the cobble sections started. I don't know if other riders used the same tactic.

I was thinking of later stages of the race when speed really matters, and there are often solo breaks or small groups. I guess it isn't possible to switch bikes then, but I wondered what you might be giving up on the smoother sections and velodrome by optimizing for cobbles.

Funny that you mention this. The airplane thing is one area where you'll find some disagreement. And it has nothing to do with pressure change due to altitude. 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.

Of course, on the flip side of that argument is Josh's argument that you can go from -100F -> 350F without issue, and certainly there isn't a 450F swing in the bottom of the airplane. But it can get really hot in the belly of a plane, which is actually more relevant for other things you might pack in your luggage. But this is (part of) the reason for not allowing pressurized containers - and really, it's THAT policy that causes some airlines to want (aka demand) people to deflate their tires - on planes. It's temperature change rather than pressure change - more specifically, pressure change due to temperature change rather than pressure change due to altitude - that is the culprit.

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

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

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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!