rydabent

A few year ago Greenspeed did research on tire roll down. Contrary to all expectations a 20" wheel had the best roll down.

The thing is on a glass smooth road which there never is, a narrow very high pressure tire would have the best roll down. But on a road that has the usual bumps and other imperfections, a wider lower pressure tire has better roll down.
The reason is an ultra high pressure tire does not "give" and therefore causes the whole bike and rider to lift. That lift results in lost forward motion, because speed is sacrificed to lift the bike and rider, and thus a slower speed and roll down.

ClydeClydeson

my belief/experience is that the faster you go on smooth asphalt, the more advantage/less disadvantage you get from narrow HP tires. When I went from 700 x 30 to 700 x 35, I was the same speed or faster most places, except for on downhills. Maybe a tiny bit slower on climbs because of the tiny bit of added weight.

I don't know if I can actually tell this for certain, but it seems like the aerodynamic resistance of the fatter tires is noticeable at higher speeds.

wphamilton

That's a lot of discussion so it's probably already been said but there isn't really a myth about it. Larger diameter wheels have certain benefits for speed in some conditions, with drawbacks in weight and handling in some conditions. I think we've always known this.

njkayaker

Most of the discussion here was about tires.

Years ago, people routinely bought road tires that were 20 mm (even narrower). Now, it seems like 25 mm is the norm.

So, something has changed.

It seems that people thought that narrow tires with high pressure were significantly faster. What it seems that was learned is that that isn't true in an practical sense (how people typically use the tires).

Moulton in the UK appears to be the only concern advocating small wheels for "regular" riding.

https://www.moultonbicycles.co.uk/

In mountain biking, there was a big interest in going larger (to 29') from 26' but no one appears to be interested in going smaller.

tomato coupe

Yes, but a lot of people seem to live in a world defined by "xx is always better" or "everyone should use what I use."

wphamilton

What changed for me was higher quality larger tires got cheaper, or at least the more affordable ones got easier to find. I had gradually dropped from 32 to 20 looking for that extra speed, realized that the tire's construction made more difference than its width, and now back to 28's.

People being hard core about the small high-pressure tires was before my cycling time I guess, because I don't ever recall any general agreement about that.

njkayaker

Among the thing Heine talked about and promoted.

The change from the standard being 23 mm to 25 mm is fairly recent. And that was just continuing the trend.

Many road bikes didn't even have room for wider tires. Now, it seems most of the current ones can take 28 mm.

philbob57

One big change is that local roads have gotten worse in the parts of the US that I know in the last 40-50 years. *** Political statement removed by author. ***

Miele Man

I ran into that problem with a Fiori Venezia I was rebuilding for a friend. I tried putting 28mm tires on it but the rear was tight against the brake bridge. thus I was forced to use 25mm tires.

Cheers

smashndash

I don’t think Jan Heine predicts that WT pros are gonna be rockin 38s... ever. But it’s probably fair to say that most people who ride bikes do not compete. Thus, safety, comfort and versatility are all higher priorities than outright speed. Even today’s race bikes can take 32mm tires. New endurance road bikes can clear 35s. It’s probably not a stretch to assume that in 10 years, non-racers will choose to run 38s.

50PlusCycling

Tire size, like frame shape, has perhaps more to do with fashion than practicality. Very often, form comes at the cost of function. A great example of this was the 70's Chevrolet Corvette sports cars. They features curvy, aerodynamic bodies, yet in a wind tunnel, the lowly Chevette was more aerodynamic and stable. Cannondale avoided the sloping frame design for years because no matter how they engineered a sloping frame, they could not make it lighter or stronger than conventional frame, but in the end they produced them because the market prioritized fashion over function.

The same is true in the case of tires. You only need as much tire contact as is necessary for safe cornering and efficient braking, any more than that you add rolling resistance. As for myths about wheel and tire sizes, as the economist Milton Friedman said "You have to be careful with figures, anyone came make them say anything they want." Friedman worked in statistics during WW2 studying the efficiency of different bullet and shell designs, and few people knew more about the vagaries of statistics than he did. In time things tend to evolve to their most efficient form, more or less, though fashion trends from time to time have an effect on efficiency, such as the baggy clothes popular in the 90's in mountain biking and winter sports. These certainly slowed riders and athletes down, but once again, "fashion" reared its ugly head, and being fashionable was more important than being fast.

I like larger tires because they are more comfortable. However, that comfort always comes at the expense of increased weight and rolling resistance. Road bike tires used to be quite large, and over time, as bikes got faster, tires became narrower. A 60kg rider on a 10kg bike does not need a lot of rubber on the road, and on a weight-per-rubber basis, a narrow bicycle tire has a larger contact patch than a motorcycle or most cars. Bigger is cooler, but is not faster. On the other hand, smaller is also not better. A 20" bike might have broken speed records, but that is because the entire bike was less than 36" tall, and aerodynamic drag is a greater problem than the rolling resistance the wheels, and becomes ever greater as speeds increase.

pdlamb

When you average hundreds of millions of X-mart bikes running 2.25" wide tires, tens of millions of hybrids running 2" wide tires, and a few million road bikes averaging 28, maybe 32, mm wide tires, I think you're already wider than 38s (on average).

70sSanO

Which also suggests that bikes should be 25lbs or more based on the millions of heavier ones out there in use. After all the numbers support that position.

And you can take it even further and suggest technological advances have failed since low technology dominates the industry. The sheer magnitude of low end bikes dwarf the rest.

Even the pandemic suggests that manufacturers have squandered an opportunity by not focussing entirely on less expensive offerings.

It is so easy to point to something to support a position, regardless of its validity.

John

70sSanO

One thing I’ll add which is OT. This bike boom has shown it has absolutely nothing to do with the professional aspect of the sport.

It does make one wonder why manufacturers, or even sponsors, are even involved in professional cycling. It has an obvious appeal, but most likely to a very small segment of the industry.

John

tomato coupe

Yeah, why are auto companies involved in auto racing? Or ski companies involved with ski racing? Most importantly, why are Nike, Adidas, Wilson, and Reebok involved with any professional sports that use athletic shoes or athletic clothing? It's a mystery ...

Trevtassie

All I know is that my fastest ever downhill run was on a kids bike with 12 1/2" x 2.00 tires on it, pumped up to an indeterminate pressure. I passed a couple of roadies who were in the tuck...much to their surprise. I think if I paid more attention to tire pressure and drank more beer I could go faster. Mind you, being pretzelled up on that little bike meant I walked around like a 120 year old the next day, eventually my back straightened out.

70sSanO

Huh???

Air Jordan’s ring a bell?

John

Trakhak

The person at the other end of the phone may not have an unmixed reaction to the "This is Doctor . . ." gambit. I remember getting the occasional similar call when I worked at bike shops:

"This is Doctor Smith."

"Yes, Doctor?"

"How late are you open?"

I would answer the question politely and hang up, having resisted the temptation to say, "Ordinarily, we close at 6 p.m., but for you, Doctor . . . ."

tomato coupe

You were asking why bike manufacturers are involved with professional cycling. Ask yourself why Nike is involved with professional basketball, and you will have your answer.

WizardOfBoz

Trakhak, you may enjoy this true story. The story's a bit self indulgent and a trip down memory lane - please humor me. When I was growing up, my Mom and Dad's best friends were Dorothea and Eldon S. Great people. Wisconsin farm kids. Eldon owned an office equipment supply company, but had been in the Army Air Corps in WWII and was a bomber pilot. Thirty five missions over the Ploesti oil fields. That gives you a certain disdain for pretense, I guess. I remember Dad (a baritone with perfect pitch) and Eldon and Dorothea (both beautiful voices) singing around the player piano. Good memories.
Anyway, the four are down in Chicago to see a show. Beforehand, they end up at a really popular restaurant. The Maitre'd was like "Table for four? An hour an a half", and the offer of twenty didn't move things. So they put their name in and go to the saloon. Both Dad and Eldon, uh, knew their way around a bar stool. But Dad gets an idea. This is like the late 60s, eh? Dad goes out of the restaurant, to a drug store next door, one with a quiet phone booth. Calls the restaurant.
"Hello, Pump Room"*.
"Hey der. Mayor Daley's office calling. May I speak to the manager?"
"Uh, yes sir"
"Hello, this is John Ratzinger, how may I help you?"
"John! This is Joe Dembowski from the mayor's office! I was calling because we understand that some friends of the mayor are coming by your restaurant, and the mayor wanted me to ask you to extend a real Chicago welcome to them. Their names are Eldon S. and Bob B."
"Well, thank you for calling, Joe - we'll take care of it!"
"That's just great John! I'll tell the mayor - he'll be thrilled about this!".
My dad walked out of the phone booth, crossed the street, walked in the saloon door, and saw the Maitre D' walk in from the foyer.
"Table for four? Please come with me!"

Anyway, sometimes titles and associations work.

70sSanO

You can’t be serious comparing Nike, especially Air Jordans, to professional cycling.

Probably 95% or more of the US population can only name 1 professional cyclist, and we all know who that is.

But you are correct comparing it to skiing, well, cycling will never fall down to the level of skiing.

John

Edit Added: And I shouldn’t just bring up Nike and Jordan, maybe just move on to Tiger.

tomato coupe

It's not all about the U.S. As a reminder, the U.S. accounts for only 4% of the world population.

70sSanO

Fair enough.

John

Kapusta

The difference between the bicycle industry’s myopic obsession with pro road bike racing and athletic footwear companies’ affiliation with professional basketball is that the latter did not result in the industry pushing sneakers that were uncomfortable and ill-fitting for the 99% of the population that were not professional basketball players.

I honestly think that the professional road racing did more harm than good for cycling in the US. Thankfully this has begun to change in the last ten years, and we are finally seeing a lot of high quality bikes designed for the 99% of the population that are not pro racers.

The best thing to happen to mountain biking was the declining influence of XC racing in the late 90s and early 00s. Once designers started focusing on something other than what will win an XC or DH race, MTBs got much, much better.

What is happening in the road world is kind of similar, but to a lesser degree. Racing still has an outsized (and IMO unhelpful) influence.

wphamilton

Your post was informative and well written so I don't want to seem deprecative by singling this out but I think it's interesting because it's a common opinion and we are talking about myths after all.

Rolling resistance is not increased due to the size of the tire contact. Neither is friction. There are some factors increasing (or decreasing) rolling resistance which also alter the size of the contact patch. I think that's mainly where this comes from, but it's really not hard or complicated. The size of the contact depends on weight on the pneumatic tire and the air pressure inside it. Not on the size of the tire, and only a tiny bit on the construction of the tire.

More weight can cause more rolling resistance, and also makes a larger contact area. Lower pressure can cause more rolling resistance (on a very smooth surface) and also makes a larger contact area. In both cases, it's not the contact area causing rolling resistance - it's the weight, or the bend in the tire around it (more bend with lower pressure).

That's pretty simple, and concerning friction - grip - it isn't more complicated. Generally speaking friction does not depend on the size of the contact. I say "generally speaking" not as a weasel, but only because this is not a physical law derived from basic principles. It's what we've found to be true for almost all materials in normal conditions. A bigger contact area can result in more grip, but because the tire doesn't bounce as much at lower pressure and not because of the contact area. Again, it's something else that affects both things.