danallen

If you asked 100 random people, "Which came first, landing on the moon and flying back to Earth, or discovering that the fastest road bike tire setup is fat/soft vs. thin/hard?"

I know that over simplifies, the faster tire setup is not ALL fatter/softer is faster than anything thinner/harder, but the fact remains, until a few years ago, everybody thought the fastest ride would involve the thinnest/highest pressure and it was a surprise to basically everyone that is not the case. I would have thought optimal tire setup would have been known way before Neil and Buzz made their trip in 1969.

Can you explain why the discovery of something so basic happened so late in the game?

seypat

Because in general, most cyclists are weight weenies. They will spend thousands of dollars to pare a couple of pounds from the bike. The thinking used to be everything lighter will be faster. I'm not "that guy."

Spoonrobot 

Problem is, it's not true.

Here's the real world breakdown for what is generally considered paved riding.

19mm tires are slower than 21mm tires are slower than 23mm tires, many of which are slower than some 25mm tires, many 25mm tires are faster than 28mm tires, most 28mm tires are faster than 32mm tires, 32mm tires are faster than 35mm tires, 35mm tires are faster than 38mm tires, etc.

Fiddle with the dial for rating the roughness of riding surface and the center point can be shifted left or right. Indoor wood track? 21mm tubulars. Wretched streets of Boston? 28mm. There's no free lunch; weight, aero and hysterisis all have an effect that cannot be hand-waved away in the real world.

Nobody who has won any major titles related to speed uses anything but narrower and higher pressure tires. ITT? TT? RAAM? PBP? Hour Record? Even gravel events like DK200 the riders (most interested in speed) are now using the narrowest and highest pressures they can get away with.

Where is the plucky upstart on 35s who figured out he could ride Snake Alley faster than anyone else for an advantage great enough to win? There is a massive cornering advantage for wider tires, and yet there is not a criterium in the entire United States where a rider is on larger than 28mm tires. Where's the triathlon champion who found the increased comfort with no speed loss a huge benefit for the 112 mile bike ride that happens before the marathon run? The comfort advantage of wider tires is huge, but so are the aero losses. How is there not an arms race for every single group ride in the country, ignited by one guy showing up on 38s and crushing the group that was formerly so much faster than he?

Grab bag of responses:
Racers don't know (they do)
Racers are bound to contract equipment use (not if they'll win on something else)
Racers are dumb (not about how to win)
Let's redefine "fastest" (no)
Here's a graph I didn't make that has data I didn't record (what happens in the lab should stay in the lab)
Here's another graph from a different company (see above)
Here's a regression analysis (do you ride through the cells of a spreadsheet?)
Here's a rider who won a 5 rider criterium in South Dakota on 32mm tires (exception can prove the rule)
Here's a rider who finished PBP on 48mm tires (60+ hours)
Here's a rider who finished RAAM on 32mm tires (15th percentile completion place)
Reference to misinterpreted tank study (find the study, read it yourself and see how much it applies to what happens with bike tires)
Reference to rumble strip study (how much of any given ride do you spend riding over anything that comes close to resembling a rumble strip?)
Bike Fake News Media personality post (every single one of these guys has something to sell)

This specifically; many, many riders knew 19mm and 21mm tires were not as fast as 23/25, there just wasn't an outlet for their comprehensive voice like there is now. Just like now, many, many riders know 28mm tires are not as fast as 23/25.

Trsnrtr

I feel part of it is improvements in clincher tire construction. I’m in my 38th season and clincher tires in general are way better than the stiff carcasses of several decades ago. A 32c clincher tire in the 80s weighed a ton and was stiff as hell, so we compensated with hard, skinny tires that rolled better on smooth surfaces.

The tubulars, on the other hand back then, were generally rounder and wider and rolled great. Modern clinchers have narrowed that gap quite a bit, imho.

one4smoke

If you want to go faster ...pedal faster.

(Don't ya hate when people give responses like this?)

SkepticalOne

Not only are narrow tires lighter, but they have a lower frontal area, reducing aerodynamic drag, all else being equal. These concepts are fairly intuitive to most and would lead one to a narrower tire (requiring high internal pressure).

Rolling resistance on the other hand is far less intuitive and is variable depending on road surface condition - in fact narrower, higher pressure tires provide lower resistance on smooth laboratory conditions. It would seem that the real research as to its effect on real-world has only been undertaken more recently. It really is a little counterintuitive, even to the those technical trained. Concepts like 'contact patch', 'deflection', and 'hysteresis' come into play to unlock a rigorous understanding. So it's not completely shocking how adoption continues to lag.

Many cyclists I bump into still notice and comment on my 28c (31mm) tires and 31mm wide carbon rims...they are often shocked to hear I'm running them at 65psi.

sfrider 

The problem is it's only true when running the tires at the same pressure. The moment you lower the pressure in the larger tire to get any additional comfort out of it it's no longer true. The reason it's true at the same pressure is the larger tire has to deform proportionally less.

rosefarts

Spoonrobot nailed it.

This "revolution" was enough to get a lot of us to try 25s and 28s. Not really slower and come with a little added confidence.

I don't miss my 20s or 23s but I'm not going overboard.

Steve B.

Agree with this,

OmegaWolf

The answer is simple. Apollo 11 did not get to the moon on pneumatic tires.

seedsbelize 

Vindicated! I never stopped riding 23 and 25mm tires. I'm it a similar category with trainsnorter. Old.

smashndash

Here’s are some good rules of thumb, imho. If the reason you won’t ride at a lower pressure is that the tires feel sluggish when climbing, or riding in general, then going with wider tires will probably not help - you’ll just be lugging around more rubber.

If the reason you won’t drop your pressures is that you’re afraid of pinch flatting (with tubes) or damaging your rims (tubeless), you are a good candidate for bigger tires.

If the reason you won’t drop pressures further is that the tire feels vague when cornering, you are a good candidate for wider rims.

Optimal pressures and tire sizes will vary depending on priorities, tire construction, body weight, road surface etc. I am personally in the “afraid of damaging rims” camp with 25mm race tires. But with more reinforced 25mm tires, I run them at a high enough pressure that pinching isn’t as big of an issue, because the tire feels mushy at lower pressures. So the more supple your tire, the more likely a wider tire is to be of a benefit. Look at the extreme end of this spectrum: if you use a solid steel tire, the size doesn’t matter. It’s gonna be harsh regardless, so you may as well use the smallest one you can.

jpescatore

Just as things are different for rocket powered cars setting 200 mph+ land speed records in the Bonneville salt flats vs. the general public driving their old Pontiac Bonneville at 60 mph on commuting and vacation rides, the optimal setups are very different for pro racing and general bike riding. In the past the science tended to focus on the former - rolling resistance tests on smooth dynamometer rollers and wind resistance testing at 20+ mph. Very different science on typical road surfaces and at 15 mph and below.

But, the bike and car industries know that people will spend more if they can feel like they will be able to 200 mph if they happen to be on a salt flat, or climb a mountain in their car if they ever happen to actually go off road, or do 60mph downhill if they ever happen to be biking down the Alpe d'Huez! There wasn't much financial incentive for anyone to do the tests to point out the cost/gain ratio that the pros get on a 200km race at 24 mph didn't really add up for a 100km club ride at 17 mph.

big john

Top fuel dragsters hit over 330 mph in less than 4 seconds with 4 psi in the rear tires. You can buy production cars that will hit 200 mph.
The land speed record is 760 mph.

Spoonrobot 

Faster tires are more beneficial for slower riders (especially those riding alone) as the effect of the marginal differences are magnified at lower wattages. 10w at 150w ftp v. 10w at 300w ftp.

Caliper

I don't think that is true.

Look at the origin of a 700C wheel. C specified the tire width and 700 the rolling diameter. The 700C system used the same 622mm BSD rim that we use today. So, if you work out the math, the tire size that gets a 622mm rim to a 700mm tire diameter is 39mm. Hmmm, that's basically what works great on gravel bikes today. It worked great on dirt roads then as now.

I wonder if what happened is that after WWII, the western world made a lot of infrastructure. Lots of freshly paved roads that were laid down well and maybe didn't have all the cracks and frost heaves that we see today. Fresh, quality pavement is amazing on a 23mm tire and there is zero penalty inflating the tires to their limits. The surface is flat and smooth and the bike just sings. But, we have many other diversions for our tax dollars today and the roads don't get maintaned so now the roads that used to be great aren't so much anymore and as the surface gets bumpier, wider tires become more useful.

noglider 

All things being equal, the wider tire is faster. But all things are never equal. Using the same construction, the wider tire is heavier. One recent breakthrough is thin sidewalls which alleviate a bit of the problem of them being heavier and stiffer at lower pressures. Also, a narrow tire will feel faster because of the way it responds to steering inputs, so there is some illusion at play. Another factor which is extremely difficult is rider fatigue. A narrow tire at higher pressure, even if it is more efficient, will fatigue a rider more on a long ride than a wider tire. So the efficiency of the motor is affected by tire choice, but how much? Who can say?

So the optimum width depends on a lot of factors, including your own comfort, how far you ride, and how quickly your body fatigues. Oh, and a huge factor is how fast you ride and how windy and hilly the conditions are. That's why there is no ideal width even if we could measure all the factors, which we can't.

ThermionicScott 

If you go back even further, 700C is just a French repackaging of the wired-on version of the original 28"x1-1/2" wheel from the very end of the 19th century. Hmm, 1-1/2" is pretty darned close to 39mm.

I think you're right that better roads enabled skinnier tires. In the 1960's, Cino Cinelli even tried to move the industry to smaller-diameter wheels since he felt large-diameter wheels were obsolete.

Seattle Forrest

How many angels can dance on the head of a pin?

zjrog

Fixed that for you...

TiHabanero

I just love this thread!

seypat

Spoonrobot 

This is boilerplate and has probably been written hundreds of time by dozens of adherents to a modern myth, mostly driven by the preferences of a small group of cyclists. Your main point does not follow conceptually, there is no ceteris paribus for tire width comparison - if all things are equal, save tire width, the wider tire is always going to be slower. Much of the current wide tire testing has been designed to obfuscate this fact. Furthermore, if the gains for comfort/fatigue from wider tires are there, they're at a distance so extreme as to only benefit a minuscule group of cyclists. The rest of the body does so little on a bike, fatigue from harder or softer tires is a non-factor - for road bike riding. I and many riders I talked to have not noticed any significance in fatigue on rides up to 200 miles, certainly the vast majority of extremely long road bike rides are done on tires less than 28mm wide.

There is an ideal width for speed, we can't handwave away the main contention of this thread:
There is an ideal fastest road bike tire setup, it's 25mm.

Psimet2001 

This always gets old. I'll stop back in 10-20 years when we go back to thin.

You ever been around an organisation long enough to see it go through the cycle of thinking they are too big and need to lean down? Then they lean down and see gains. They continue and think they can continue on that path and reach business nirvana. Then the problems start creeping in. Then in 15 years they start coming out with corporate programs that are the opposite of leaning down but are there to address the problems that their initial efforts caused.

It's almost as if there actually isn't a surefire answer. It actually does always depend on a ton of variables. Last I checked we were still riding narrow tires at high pressure on the track. Also last time I checked some dude won a crit somewhere on 32 spoke box section wheels and downtube shifters with 30mm tires.

Having good tires and wheels you can rely on that give you the confidence to race the way you need to race is the fastest combination out there. Everything else is a bunch of Freds and posers who think someone's made up data is somehow meaningful in the real world.

Seattle Forrest

Last two responses are dead on. Soon we'll use razor blades for tires because they weigh less and are more aero.