Suspension Losses - Now Confirmed by Other Research

[Jan Heine]

In science, it's important that results are replicable - this means that anybody doing the same experiment must get the same results. I was excited to learn that recently, Joshua Poertner (formerly of Zipp, now of Silca) has replicated our results on tire pressure: Higher tire pressures don't make you faster on smooth pavement, and definitely are slower on rough surfaces. He apparently used the same rumble strip method as we did when we first quantified suspension losses. 

More about this is here:

https://janheine.wordpress.com/2016/06/14/suspension-losses-confirmed/

It's exciting that what used to be highly controversial now is entering the mainstream. And I want to thank the listmembers who were open to these ideas long before anybody else. 

Jan Heine

Editor

Bicycle Quarterly

www.bikequarterly.com

[Deacon Patrick]

Thank you, Jan! What you said about the vibrations in the body (and thus the brain) and your being sore all over after testing, got a big "Yes!" from me, as I've found my brain energy is sucked out rapidly with stiffer tires.

With abandon,

Patrick

[Shoji Takahashi]

The article referenced by Jan features a French-blue Rivendell Road with resist nomads:

http://trstriathlon.com/talking-tires-with-joshua-poertner/

(I think this is David's bike, and I hope he's compensated given the reference to photopin license. His Flickr feed shows up as no commercial use.)

I like this section (towards bottom of the article):

If wider is better, is a lot wider a lot better? And if a wider tire is what the world needs, then do we need a wider wheel to hold it? More accurately do we need wider wheels, wider forks, and wider chain and seat stays to hold them? Who is going to manufacture all this stuff, and how will the bike designer, the wheel builder, and the tire maker negotiate the new standards?

Indeed, who is going to manufacture all this stuff???

shoji

[Peter White]

I remember being told this by one of the technical people from Michelin some 35 years ago at the east coast trade show - what is now Interbike in Las Vegas. They knew back then that very high pressures gave you no advantage. So this tendency for tire manufacturers in the past 30 years to rate their tires with higher and higher pressures has always seemed odd to me. But clearly, the public has been sold on the idea that higher pressure is better, to the detriment of ride quality, performance, and the durability of rims.

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Peter White

[Lungimsam]

What role does tire pressure and width play in difficulty/ease of tire spin up?

[Peter White]

Please define spin up?

On Tue, Jun 14, 2016 at 3:51 PM, Lungimsam <john1...@gmail.com> wrote:

What role does tire pressure and width play in difficulty/ease of tire spin up?

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Peter White

[Lungimsam]

Spin-up:
Starting from a stop and getting the bike revved-up to cruising speed where one abandons standing on their pedals and takes their seat.

"Spinning-up" the tires/bike from the stop to cruising speed.

[cyclotourist]

Hey, that picture does look familiar! Thanks for the heads up, Shoji!

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Cheers,
David

Member, Supreme Council of Cyberspace

"it isn't a contest. Just enjoy the ride." - Seth Vidal

[cyclotourist]

This would be the original image: https://www.flickr.com/photos/cyclotourist/8622476729 

On Tue, Jun 14, 2016 at 11:53 AM, Shoji Takahashi <shoji.t...@gmail.com> wrote:

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[cyclotourist]

He links to the original. A heads up would have been polite I suppose.

[Peter White]

Ah! The larger tire has more mass, so it would spin up slower. Other than that, I'm not qualified to give an opinion.

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Peter White

[Lungimsam]

1. What does the higher mass do in regards to climbing? Help or hinder?

I wonder at what point the mass is nullified by hysteresis, s-losses, and planing, supple tires, etc.? One could do alot of mixed variables tests to see how it all shakes out.

2. Also, what about tire sidewall deformation under the force of the rim turning?

Wouldn't a supple tire's sidewalls deform more, lagging behind the rim to a point, though the bead stays in place, resulting in slower response and drag?

[dougP]

Kinda funny when you think about a Rivendell photo appearing on a triathlon blog.  Next we'll see moustache bars replacing aeros.  :-)

dougP

[RichS]

Doug,

Another example displaying the versatility of a Riv!

On Tuesday, June 14, 2016 at 12:51:58 PM UTC-4, Jan Heine wrote:

[Evan Baird]

I'm delighted by all the roadies buying 25c tires like they're going to have this religions experience or somthing. I just kind of sneer and explain that I never ride anything under 38mm.

[Jan Heine]

You bring up good points.

1. Higher mass will slow you down climbing, but the question is how much. Realistically, the differences are very small. We tested a 650B randonneur bike with 42 mm tires against a titanium road bike with 25s. Both were excellent bikes, and their speed was the same. Clearly, the difference in weight got lost among other, more important factors.

2. Yes, sidewall deformation is an issue - that is the start of the sidewall collapse under high cornering loads. That is why you need to run slightly higher pressures with supple tires. Even at those higher pressures, the supple tires are much faster and more comfortable.

Jan Heine

Editor

Bicycle Quarterly

www.bikequarterly.com

[Lungimsam]

Thanks Jan,

Did you test the Rando vs. Ti bikes by powering the bikes with riders? I know some of your studies have used small samples with human riders powering the vehicles.

Is it possible that a study involving a human rider powering the bike will be reliable and valid in light of the fact that the state of the engine changes moment by moment? I am by no means a scientist, so forgive my ignorance. Sometimes when I read about the studies all these other ideas pop up in my mind to explain away the findings and I don't know if they matter. I don't know if the ideas would really have any type of meaningful effect on the results.

Also all the other extraneous factors like the fact that the bikes weren't ridden exactly on the same line, subjected to different air movement patterns, minor grade changes in the different lines, different components/frames, etc.

I think it is really difficult to test bike performance because there are so many variables. And while one may be explained away as noise in the data, all the elements, taken as a whole must have a profound effect on the movement of the bikes.

Is this true or is it not so difficult to get reliable data in bike tests?

[Jan Heine]

You are right, there are many potential variables. We are lucky to have two riders who weight the same, have the same height and the same power output: Mark and me. So if we ride next to each other on identical bikes, we ride at exactly the same speed. If the bikes are different, and one is faster, then we switch bikes. If the same bike still is faster, then it's faster. If the other bike now is faster, then one of us is having a bad day.

This technique factors in wind, temperature, fatigue, etc., since it's the same for both bikes and riders. More on the Rando bike vs. Ti study is here:

https://janheine.wordpress.com/2013/02/19/laws-of-physics/

Jan Heine

Editor

Bicycle Quarterly

www.bikequarterly.com