Eric F 

You’re making assumptions about my feeling of “sluggish”. I ride road bikes, MTBs, and gravel bikes. I’m familiar a wide variety of feels and responses. The heavy and slow feeling of the Thundero 48s on my gravel bike was like a big ‘70s Cadillac. It’s a feeling that turned me off for a bike that I want to have a more agile response. My MTB with 2.35s feels more responsive on pavement. As I said before, maybe I need to try again.

vespasianus

Thanks. I got mine from https://www.bike-discount.de/en/.

They don't have the HD versions or the bigger stuff (only 44mm) but great prices.

Fentuz

You are correct, like many data, a screenshot without context is meaningless. The thing which is interesting in the video (the screenshot in from), they clearly say they do not know why the larger race king is better than the cinturato H.
They mentioned the road setup with the 105 aero estimation for narrow tyres and then go toward the turbulence cleaning effect and give some hypothesis but the big thing they keep repeating is that they do not know why and they say they got lucky. The results are applicable to the race king but are not a general rule and they do not know why? hypothesis, results have to be analysed and V & Ved (until there is real financial interest into that, it s unlikely it will happen).

One of the thing Dylan mentioned in his videos is that Aero and rolling resistance are the thing to look for. So as many said, it is about selecting the tyre that will favour these rather than a short distance of mud...

Spoonrobot 

Aero and rolling resistance are the two primary focus items, right now, because they are the easiest to express as simple numbers.

Suspension losses are harder to measure and much more difficult to present in a simple manner.

This is a very old graph (6-7 years?) and has been supplemented by more recent data, but it presents the basic idea.


https://silca.cc/blogs/silca/part-4b...-and-impedance

Spoonrobot 

The context is self-contained in the conversation. What more could possibly be needed, he made a statement that was false. I provided evidence with source of why it was false. What is the missing "context"?



"Wider and knobbier tires will always add to aero drag"

False, here is where it has recently been disproven

"Uh.....context please"



As I said before, significant information asymmetry. Demanding a discussion standard of me, that nobody else is even attempting to meet.

Spoonrobot 

Watch the video, watch other videos. Go on JSTOR and see what you can find and read it all. I will continue to be your tutor, but there is only so much I can do.

The tone of this thread is set by the people in the conversation. You re-started the thread yesterday with a sarcastic insulting response, why are you surprised when the tone is matched? If you don't like the tone, do not respond in such a way to others.

What did your power meter show? What did your timed test segments show? What did the stopwatch show?

"Feel" is a means to an end, not the thing itself.

StanSeven

I cleaned up some posts that border on insulting others. Let’s keep the discussion civil or we will issue infractions and close the thread.

Fentuz

No, you took a screenshot and did not give the full picture which is in the video. They do show that for a given tyre, as you up in size, you loose Watts.
Then they explained they tried something different, a different system which is giving better results by luck and they don't know why.
Eric F comment is in line which what is expected however, in this very specific situation, there is something lucky. So does a one off anomaly enough to refute conventional wisdom?
They clearly say the data are repeatable and not explainable; a single set of data for a single product does not make EricF's statement false. That said, more work should be done to understand the data and therefore develop better large volume tyres with good aero and low rolling resistance.

Spoonrobot 

The full picture was contained in my original response. Your additional context has added no relevant additional information.

Wider and knobbier tires will not always have more aerodynamic drag. This is the result of the experiment, it has upended what was previously known and what was once a true statement is false. that's the whole point of such work. Tire width and design are not constrained by "conventional wisdom" - as if that phrase had any relevance to aerodynamics in the first place.

We also don't need to appeal to "luck". There is a very small pool of XC size tires that have ever seen the inside of a wind tunnel. We don't have the data to say if the Race King is an anomaly or not. It's entirely possible that as tires pass a certain width, and with certain knob design, the knobs act as turbulator strips (or perhaps vortex generators) and keep air separated from the sidewall (and possibly the tread), effectively reducing both frontal area and cross section density and thus reducing drag. Close to, or perhaps the same as sailing effect. We know that mathematical models of fenders do something similar and theoretically provide similar benefits, within the model speed bounds.

For anyone really keyed in, this wind tunnel experiment argument is basically a re-hash of the wide tire argument. Think back to all the arguments about how and why wide tires couldn't be as fast as narrower tires and how that turned out. Lesson there.

Koyote

It seems to me that most of this thread's participants are here to learn. Thirty five years as a college professor taught me a few things about the learning process: people don't learn when they're regularly reminded of their ignorance. (Or of the information asymmetry.) When approached by a closed mind, others' minds tend to close, too. And I learned to be less dogmatic -- because that dog has a tendency to come back and bite you in the ass.

I'm not saying that I've learned these lessons well enough to always abide them...But they are aspirational.

prj71

Should have been closed a while ago once it got polluted by a couple of people...

Eric F 

I'm not making any claims about faster or slower. How my bike responds to my input, and how it responds in different terrain conditions, matters to me. Feel might not be "the thing", but it is "a thing". Maybe not to you, but it is to me. No tires were going to turn my 91st place into 50th...or even 90th, probably. However, despite my feeble result, I spent a little over 5 hours riding a bike that did everything I wanted, exactly as I expected, in all of the conditions I experienced that day - fast and slow, smooth and chunky. That matters to me.

Eric F 

Yep. This is what I was referencing before. I would love a BRR-type database for this kind of testing. Harder is faster...until it isn't

Eric F 

Always check www.lordgun.com. I've bought a lot of tires from them over the last few years, and have always been pleased with pricing and delivery speed.

Pendergast

In spite of the acrimony, I think this has been an informative thread. I was already aware of the Dylan Johnson wind tunnel video. The 50mm Cinturato is a tire I was considering for one of my bikes and still am. The 2.2" Race King is a tire I was also considering and still am. Other factors are very much more important to me than aerodynamics in my decision for that bike, but the wind tunnel results were still interesting. Seems to me that there are quirks of aerodynamics that are difficult to pin down. Is it the tire itself that makes the 2.2" Race King more aero than the 50mm Cinturato or is there some sort of synergy with the Lauf fork and/or the wheels in the video that makes it more aero. Would the Race King still be more aero than the Cinturato in my Niner fork? With my wheels? I don't know. I don't expect to ever know. I'm not a racer, so that level of minutia doesn't matter much to me.

Eric F 

Dylan’s video showed testing of just the tire and wheel. No bike. It was also at 20mph, which is a bit optimistic for a lot of folks.

t2p

respectable - very respectable

most of the competitors in an event like that are fairly respectable - and you finished ahead of a significant number of them

and it’s not like you don’t do / have other things going on

Eric F 

Thanks. I found out that doing a 70mi gravel race is difficult when you are averaging less than 70mi per week for the two months before the event. Life got in the way. I underperformed compared to how I've been for other races, but it was anticipated. That said, I'll never be a top competitor. Even when life cooperates, a "good" week for me these days is around 100mi, with maybe one ride over 3 hrs.

Eric F 

Estimates on increased cRR and aero drag put Thundero 48s at a ~6W disadvantage compared to Thundero 40s. This gap narrows a bit with a Swampero 40 on the front.

I understand Silca's article about impedance, but it's limited to road tires. Where can I find similar info on gravel-size tires to make comparison estimates?

Spoonrobot 

Make sure you correctly factor the marginal values for tires individual front and rear. Aero/Hysteresis are slightly different for each, small number but relatively large.

Bicycle Quarterly back issues, Tour Magazine back issues. Most of the online stuff that is public facing is from Jan Heine and high level compared to the magazine. He provides several different estimates over time but I can't recall off the top of my head.

I don't believe I've seen anything nicely packaged for consumption in a graph or chart. There's lots of discussions but almost no hard data. I have my own set of estimates but I'm not interested in sharing. Not sour grapes, but recognition that being one of the first to put forward a model isn't beneficial. I'll see if I can make a simple estimate and explanation.

Eric F 

I included only the aero drag increase for the front tire. I estimate the rear is likely to be fairly inconsequential due to the turbulent air it's swimming in. The wheel depth is probably more of a factor than tire size. Although there are cRR differences between front and rear due to unequal load distribution, for the purposes of my estimates, I used the BRR values, adjusted for tire pressure.

I have no argument that a softer tire is going to be faster as the surface gets rougher (but also slower on smooth surfaces - the gravel compromise). Being able to put some sort of rough value to that would help my brain connect the dots. I understand the amount of variables involved makes things complex.

Why does this matter for a sh!++y, mid-pack, old guy? Because this is how my semi-engineering brain works, and despite my lack of watts, I'm still interested in a bike that gets the most out of what little I have. However, the other part of my brain is sensitive to the tactile experience (my previous comments about feel). I also know that if my engineering brain can resolve the "why", it's easier for my tactile brain to make adjustments to accept it as "better".

In another direction...How much do you feel tire/wheel weight matters for slow-speed climbing (sub-10mph, no flywheel effect)? Particularly when I'm scrambling over uneven terrain, but even on pavement, it feels like a lighter tire/wheel is easier to turn over. Knowing that climbing is my biggest weakness, lighter weight was another part of my decision for 40s.

Koyote

Hmm. Jan Heine's data? I tend to agree somewhat with the poster who wrote this: "...at this point it's obvious he gave up scientific credibility to sell product. Classic marketing methodology, boost the signals that align with your product, denigrate and dismiss those that don't."