Paydays? I love Paydays as ride food... :-)

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http://bikeblather.blogspot.com/

Do tell... picking off the little molding nubs?

ever since i started gravel and mountain biking more, i bought a topeak smartgauge (https://www.amazon.com/...Gauge/dp/B0051LQ0X4/) since i can feel a difference in traction with just a few psi difference and now i use it to verify the pressure on my road and tri bikes too. i would've never considered having an independent gauge before then and i'm surprised more roadies and triathletes don't use one given the usually poor resolution of bicycle pump gauges. of course i don't really know if it's accurate but at least it's been consistent for me

I completely agree that finding a pump on race morning would be hard. But you can build a small gauge with a bleed to keep in your race bag. Then setting your pressure is as simple as over inflating, connecting your gauge, and bleeding to the right psi.

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Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

Popular tires are made in such high volumes that they need more than one mold to hit production volumes. Let's assume there are 5 molds that are used to produce a specific tire. You'd think that two brand new tires from different molds would produce the same result... but they don't. In some cases, one mold is considerably faster than the others.

During our tire study we found one tire in particular that was faster than other identical make/model tires. We weren't sure why but after a few phone calls we learned that we had a tire from the best mold.

So to my earlier point about being careful with your protocol. Let's say you are testing two bikes. In order to save time—because wind tunnels aren't cheap—you get the bikes ready before going to the wind tunnel and buy 4 brand new tires—two for each bike. If you happen to put two tires from the fastest mold on Bike A and two tires from the slowest mold on Bike B, then Bike A has an unfair advantage. Add setting your pressure with a standard floor pump and you introduce potentially hundreds of grams of error.

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Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

This seems a little backwards, but does highlight an avenue for optimization.

With pressure loss throughout the race (especially with latex tubes), temperature variation, leakage when removing the gauge etc... It's a fair assumption that the PSI won't be bang on throughout the race. Beyond that as the tire rolls down the road it's going to deform a bit, which I suspect will again have an impact on what the best PSI is.

So it would seem what I really want from a set of wheels is minimal areo sensitivity to pressure.

I find it ridiculous to throw numbers like 0.1 psi precision and hundreds of grams of drag errors. It's rubbish.

How much does tire pressure change while riding, braking and changes in envinronmental conditons?

I think if the aero drag changes that much with tire pressure, there is a problem with your selection of tire/wheel combo.

Do you think that or do you have data to prove it?

That would suggest opinion and not fact based on data. The data says it changes quite a bit. Again, we are trying to maximize very small differences. Again, it makes it so that you can only test what you are working with directly and not take any other test data beyond what it is. You need to test your stuff in a tunnel to maximize it, or at least do some virtual elevation testing to prove what works.

Don't forget, you need to set pressures based on ride start temperature, not temperature at 5:30 AM. Know your pressure rise versus at various temperatures. Gas laws help you here.

On my race cars, we tune to 0.1 psi. You can feel 0.2-0.3psi in handling differences. The tire shape changes with that small of a pressure difference.

Differences of 0.1psi are not resulting in large changes in drag, but 5psi changes do. Not everyone needs a $2,000 pressure sensor, but most can do better than a floor pump that is +/- 8psi.

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Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

Yes, PV=nRT. Doesn't take a genious to realize pressure will change quite a bit.

Do you also come up with optimal pressures for various tire wear levels?

No. I change them every couple races after seeing some data. They become crit tires instead

Appropriate screen name

Zing!

Personally that's what I do.

With regards to tire selection and tire pressure, it occurred to me when you first released all of your carbon rims and the related information about their development, that a better design process would be to do exactly what you did but for 3-5 different tires at 3-5 different pressures. Basically, you'd be looking at ~25 possible "leading edges" that you'd have to optimize the rest of the rim for. Undoubtedly it wouldn't be an optimum shape for a given tire but it might be a better shape the range of tires and pressures your rims would likely see in the real world.

To this end, Cannondale/Hed's new Knot 64 wheels intrigue me as it appears they are mostly tire/width agnostic up to ~28mm measured.

BTW what ever happened to your casing tension study?

I agree with you on this point. With wide forks, perhaps wheel only testing is sufficient. With narrow clearances I can't imagine that doesn't change and there's been some wind tunnel tests out there that show as much. I *believe* Grill did some testing with a P5 and an 808 front which showed the whole system was surprisingly picky with regards to tire selection... more so than wheel only testing would suggest.


I'm in agreement with you on this as well. Considering all of the testing Flo has done, it would have been rather trivial to compare their wheels to a 303/404/808 or Enve's equivalents. Just send them an email and ask them what tire they recommend.

Disc brakes may die but I'm going to hold on to my rim brake wheels for quite a while. Hearing the rotor go "ting, ting, ting..." while riding to the pool isn't the end of the world but it would drive me absolutely nuts on my TT bike. Given how baggage handlers treat bike cases, it seems like a guaranty that you'd have to true your rotors if you flew to a race.

Hundreds of grams is huge! If the mold the tire came out of and a few PSI makes that big of a difference, then we are kinda screwed. We'd need to take each individual tire to the wind tunnel and test it.

Aerosticks, the Cloud and Big Data are our answers.

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Amateur recreational hobbyist cyclist
https://www.strava.com/athletes/337152
https://vimeo.com/user11846099

Except that, it's going to be few years before, A: they're working reliably, and B: people use them properly. There's going to be a ton of crap data out there for awhile.

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Jim Manton / ERO Sports

Oh I know, I was half joking because there are a lot of optimistic assumptions in there. But in theory, this could be the answer. Lots of (good) data, aggregated together, then the data analytics software sifts through it and teases out the answers.

Until then, we can head to Carson and see you!

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Amateur recreational hobbyist cyclist
https://www.strava.com/athletes/337152
https://vimeo.com/user11846099

Just a general comment - not directed at you.

When I was testing wheels and tires to decide what we would specify on the Tactical I initially relied on the testing protocol that the tunnel operator/experts proposed. After all, they had years of experience and worked with many wheel and bike companies.

We wanted to determine tires after we had selected wheels.

They had us doing three sweeps at various yaw angles with different tires.

The sweeps don’t take long and you do them one after the other - then change tires and do it again. To save time you move quickly through the testing.

We were 3 hours into a total of 12 hours of testing when I saw a strange number pattern within the data sets. I decided that the data was not reliable.

I changed the protocol to include spinning up the wheel/tire until the tire temperatures stabilized at 30 mph and then we did each sweep - totally different outcomes. We did these at 95 Psi without rider weight so I still think we only got acceptable data - not great data but better data.

I think that the different tire pressures - due to heat changes in the initial sweep runs changed the tire shape on the wheel which affected the numbers - but I never worked to formalize that issue - I just tried to normalize another input to get the data that would help support a decision on tire specification.

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Dan Kennison

facebook: @triPremierBike
http://www.PremierBike.com
http://www.PositionOneSports.com

The author has been on weightweenies discussing his test and protocol. thread here.

https://weightweenies.starbike.com/forum/viewtopic.php?f=113&t=153138&start=60


Thing I notice is he's used yaw from a control tower for his yaw values, which may not be representative of ground effects?
he's called BS on the pressure thing though.


would Canadian and some of he other more technically esteemed members of this forum be interested to have a chat with him?


He is actually a knowledgeable guy (he is an aerospace engineer by training) so this might be an interesting exercise from all. I'm sure everyone could learn from each other.

Thanks for posting!

Interesting yaw sweep. Granted at 30km/hr yaw will be higher than at greater speeds, but that is still very high yaw. I'm ok with the "pulsing". By their own statement, most of their test points will be in excess of stall angle.

I would have answered quicker but I had to go through the validation process.

1. We are not affiliated with Yoeleo at all. We are just a bunch of Engineers who build aeroplanes and race TT/Triathlons
2. I'm uploading data to show how tyre width effects overall aero performance. I will do this over the weekend.
3. The rider position was set with a laser to 10mm (FARO systems)
4. Tyre pressure was 8.25barG

Thanks

Hambini

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HELLO HAMBINI FANS!!!

Thanks Hambini!

Would love to see CdA for each wheel vs time added to the graph above.

Hi Chris,

I have eight of your wheels in the garage, so consider me a supporter. Your sincere interest in creating a quality product, evidence based approach to development and related transparency are a big part of what made me a customer. Your tire studies are a great example of providing value to customers by empowering us to make decisions that optimize your product.

You can control the narrative related to studies like this one by putting an optimized Flo 60 up against an optimized Zipp (or equivalent). Even better, put it on a control bike such as the popular Cervelo P3 and show us the integrated relationship. Easier said than done, I know.

Apologies to the thread if this is OT. Just wanted to take the opportunity to address some of the Flo related chatter on the thread.

Scott