# Classic & Vintage - How can wider-lower psi tires REALLY be that fast?

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uprightbent
02-17-11, 07:45 PM
I respect Bicycle Quarterly and love the technical articles. Their recent study of rolling resistance for wider lower psi tires seems to make sense, as many have embraced the 650 concept running 38's or 42's.

But on my rollers last night I pumped the tires (Pasela 28's) up to 90 after sitting for several weeks and was shocked by this simple change from my last ride. The resistance difference was huge, almost where I thought of dropping some air to increase my workout. I know this is no big discovery, but doesn't this simple "experiment", all sceince and technical jargon aside, demonstrate or prove that only narrower, higher psi's offer the least rolling resistance?

MetinUz
02-17-11, 08:00 PM
On a smooth surface, higher pressure equals more speed (given the same tire). That's why track tires are pumped to over 140psi. Shape of the contact patch and continuous contact with the ground is critical for speed over a rough surface.

cinco
02-17-11, 08:17 PM
As you said, it's all about rolling resistance. A stiffer tire casing resists changing shape more than a soft casing and so will take more leg power to constantly change its shape as it rolls. A soft casing will be less resistant to changing shape and therefore roll easier. But the less you change ANY tire's shape the less you'll have to worry about that and the easier it'll roll. The interesting part is the difference between skinny tires and wide ones. At an arbitrary 100psi per tire and a 200lb rider you're going to have a contact patch of 1 square inch each. On a skinny tire that contact patch is going to be elongated, effectively deflecting a greater area of the sidewall and compounding the rolling resistance of the casing over what you'd experience with a shorter contact patch on a wide tire. So higher pressure and soft tire casings will always have less rolling resistance than lower pressure and hard casings, when comparing the same widths. The reality of road conditions, though, dictates that I only ride my 170psi silk tubulars to the hospital... for a kidney transplant.

JohnDThompson
02-17-11, 09:25 PM
Rolling resistance is largely a function of tire sidewall deflection. At any given tire pressure, a wider tire will have less sidewall deflection than a narrow tire. You can achieve the same sidewall deflection in a narrow tire simply by increasing the pressure, but at the cost of rider comfort.

Captain Blight
02-17-11, 09:42 PM
Roilling resistance is only partly about the tire. The road surface plays a HUGE part in it. To get max benefit from a 19mm tire at 160 PSI, you'd also need a freshly sanded velodrome surface. Given that tiny contact patch and correspondingly high surface pressures on the skinny tire, it kind of makes sense that a larger tire, with its lower contact pressure, rolls faster than you'd think; particularly on a rougher road. I *think* the narrower and stiffer tire is suffering energy losses due to being bounced around. Vibration equals energy loss.

MKahrl
02-17-11, 10:00 PM
A 4" diameter roller cylinder is going to deflect the tire shape completely differently than a flat road surface. Some roller manufacturers use even smaller diameter rollers to INCREASE the resistance and give you a harder workout. For making tire decisions for a bike I'm going to be riding on real roads I would go with the tests that most closely resembles my riding experience.

RobbieTunes
02-17-11, 10:19 PM
I just use take-offs and whatever's on sale, but this is interesting.

lord_athlon
02-17-11, 10:30 PM
I ride Serfas Survivor 28's on my centurion, and Kenda Kwest 28's (which are bigger) on my schwinn, and the schwinn goes like a bat out of hell

Captain Blight
02-17-11, 10:38 PM
I don't believe anyone's done a really academically rigorous, quantitative/qualitiative analysis of rolling resistance vs. tire size vs. contact surface quality. I would have no idea where to start.

illwafer
02-17-11, 11:06 PM
there's some good data over in the long distance forum, but i'm too lazy to look for it.

abarth
02-17-11, 11:23 PM
"Wider tires roll faster than narrower ones: Riders have argued for years that narrower tires – especially on the road – roll faster and are more efficient than wider ones when in fact, the opposite is true. According to Wheel Energy, the key to reducing rolling resistance is minimizing the energy lost to casing deformation, not minimizing how much tread is in contact with the ground. All other factors being equal, wider casings exhibit less 'bulge' as a percentage of their cross-section and also have a shorter section of deflected sidewall." By James Huang, tech editor, in Boulder, USA

PDXaero
02-17-11, 11:50 PM
Also you must take into account the tire compound.
Comparing wider touring tires vs race tires (even negating tread pattern adjustments) are not eliminating enough variables to make a conclusion.
Proof? A ceramic tube can be filled to 100 just like a fabric one could. Would they respond the same in contact with the road? Same weight and same pressure do not equal same contact patch as material deflection will differ.
I appreciate the article but its as much a scientific study as mythbusters. Conceptually strong but not scientifically conclusive.

natzoo
02-18-11, 01:04 AM
Hey everyone,
Some of these points have been covered already, but here are some points for thought:

Rolling resistance is essentially the tire having to constantly "climb" the "bulge" and the imperfections on the ground.

The energy is dissipated when the rubber and the casing has to flex to climb the bulge.

as abarth pointed out, a wider tire has less of a bulge than a skinny tire.

Not only is there a "bulge" caused by the weight of the rider, but also, there are bumps that the tire has to climb when it travels over a bumpy road.

A lower psi tire has the ability to float over the bumps in the road. Imagine a soft tire hitting a rock. It will basically conform to the rock, and energy is not wasted trying to climb over the rock. Now imagine an incompressible tire. When it hits the rock, it has climb over it.

A softer compound rubber will have a very very small deflection. This probably adds to the rolling resistance.

Common misconception: The tire does not actually slide on the ground! I (unless you skid) The tire merely touches the ground at single point, then the point rotates out, and another point contacts the ground.

So basically, on an ideal perfectly smooth surface, an incompressible tire would have the lowest rolling resistance.

But in real world conditions, the resistance is a function of the unevenness of the surface, tire pressure, tire casing flexibility, and tire width.

02-18-11, 01:11 AM
:thumb:

I just use take-offs and whatever's on sale, but this is interesting.

iab
02-18-11, 05:57 AM
Yet another article supporting wide tire = lower resistance.

http://www.cyclingnews.com/features/tech-feature-the-work-of-wheel-energy

irwin7638
02-18-11, 07:41 AM
I don't believe anyone's done a really academically rigorous, quantitative/qualitiative analysis of rolling resistance vs. tire size vs. contact surface quality. I would have no idea where to start.

I was a liberal arts student, know nothin' 'bout this science stuff, but I have been riding for nearly 40 years as an adult. I feelthe 38mm Conti tires on my Hunqapillar roll just as fast as the 25mm Panaracer tires on my Trek. Like I said, that's just how it feels.

Marc

David Newton
02-18-11, 08:21 AM
Next years TDF winner will be riding "Fat Franks". The year after that, the world changes.

XR2
02-18-11, 08:28 AM
I believe you're missing the weight of tire/wheel when comparing wider tires to racing tires. I imagine dragging that fat azz 650X42 plus attendant hardware around the French countryside for 3 weeks would take it's toll.

late
02-18-11, 08:33 AM
I believe you're missing the weight of tire/wheel when comparing wider tires to racing tires. I imagine dragging that fat azz 650X42 plus attendant hardware around the French countryside for 3 weeks would take it's toll.

The weight makes acceleration harder.

Bicycle Quarterly did rolling tests. There wasn't a big difference,
and what difference there was seemed to be mostly a question of how stiff the tire was.

Eileen
02-18-11, 08:52 AM
Next years TDF winner will be riding "Fat Franks". The year after that, the world changes.

Last night I rode with the front group on my Thursday night ride -- on my Retrovelo. Even passed some people on the hill. When they asked me how I did that I said "It's a fast bike." "How can it be with those huge tires?" Then I told them I had 35psi in those Fat Franks.

I'm not a fast rider, and most of them can easily leave me in the dust when they want to. But the only advantage that I *feel* riding my Shogun with 27" 1 1/4" higher psi tires is the lower center of gravity, which has nothing to do with the tires and everything to do with the frame geometry.

I love the Retrovelo -- it makes the roadies think I am superwoman.

Captain Blight
02-18-11, 08:58 AM
I believe you're missing the weight of tire/wheel when comparing wider tires to racing tires. I imagine dragging that fat azz 650X42 plus attendant hardware around the French countryside for 3 weeks would take it's toll.Awesome, more opportunity to fuel up on cassoulet, Brie and red wine!

Zaphod Beeblebrox
02-18-11, 09:17 AM
on my rollers last night I pumped the tires (Pasela 28's) up to 90 after sitting for several weeks and was shocked by this simple change from my last ride. The resistance difference was huge, almost where I thought of dropping some air to increase my workout. I know this is no big discovery, but doesn't this simple "experiment", all sceince and technical jargon aside, demonstrate or prove that only narrower, higher psi's offer the least rolling resistance?

You haven't demonstrated what the B~Q article was getting at. You took 28mm Paselas, tried them at 90psi, and tried them at something less than 90psi. Its the same width tire, same casing, same everything except you tried different pressures.

The B~Q article is talking about a comparison between a narrower tire run at a higher pressure versus a wider tire run at a lower pressure than the narrow tire. Here's the example they cite in the article:

An alternative to sturdier casings is
running the wider tires at lower pressures.
by some track riders, who run their 25
mm tires at 10 bar (150 psi) instead of
the 14 bar (200 psi) used for narrower
track tires.

those 25mm tires they're talking about are in comparison to what they claim is the "standard" racing tire width of 23mm.

If you want to do the same comparison at home you'd want to try a pair of 28mm Paselas at Some psi as a reference (call it 90 if you like), and then try a pair of 32mm Paselas at the Same psi, and at a lower Psi and see what you think the difference is.

USAZorro
02-18-11, 09:28 AM
You haven't demonstrated what the B~Q article was getting at. You took 28mm Paselas, tried them at 90psi, and tried them at something less than 90psi. Its the same width tire, same casing, same everything except you tried different pressures.

The B~Q article is talking about a comparison between a narrower tire run at a higher pressure versus a wider tire run at a lower pressure than the narrow tire. Here's the example they cite in the article:

those 25mm tires they're talking about are in comparison to what they claim is the "standard" racing tire width of 23mm.

If you want to do the same comparison at home you'd want to try a pair of 28mm Paselas at Some psi as a reference (call it 90 if you like), and then try a pair of 32mm Paselas at the Same psi, and at a lower Psi and see what you think the difference is.

B Q has done tests looking at things both ways. Tires can have too much, or too little inflation (Captain Obvious would be proud of me :) ). A lot more needs to be done to be able to quantify all the variables, but the old notion that "fat tires are slower" does not always hold true.

bbattle
02-18-11, 10:08 AM
When I see Andy Schleck or Mark Cavendish line up with 700c x 32's, then maybe I'll consider it. My wife does with her Trek FX but I'm rolling along with 25's or 23's. Or, in the case of the Paramount, 7/8's

bobbycorno
02-18-11, 10:59 AM
When I see Andy Schleck or Mark Cavendish line up with 700c x 32's, then maybe I'll consider it. My wife does with her Trek FX but I'm rolling along with 25's or 23's. Or, in the case of the Paramount, 7/8's

When Andy and Mark start doing the kind of riding I do, I'll start paying attention to what they use. I don't cruise at 30mph, weigh 130lb or have a team car following my every move. Based on experience, I'm riding 650x38b's (35mm really) at 50 and 60 psi, and they're plenty fast, exceedingly comfortable on what passes for pavement around here, and feel much more secure than hard skinny tires. But what do I know? I've only been doing this since before the Schleck bros, Contador, et al were born. And I stopped drinking the "racerboy" kool-aid a long time ago.

SP
Bend, OR

bobbycorno
02-18-11, 11:01 AM
I believe you're missing the weight of tire/wheel when comparing wider tires to racing tires. I imagine dragging that fat azz 650X42 plus attendant hardware around the French countryside for 3 weeks would take it's toll.

And getting pounded to death by 700x23's at 120psi wouldn't?

SP
Bend, OR

triplebutted
02-18-11, 11:33 AM
Just ride

bobbycorno
02-18-11, 11:46 AM
Just ride

Yep. And don't assume that because someone else isn't using what you're using that they're wrong. There's more than one way to be right.

SP
Bend, OR

old's'cool
02-18-11, 12:46 PM
If you want to do the same comparison at home you'd want to try a pair of 28mm Paselas at Some psi as a reference (call it 90 if you like), and then try a pair of 32mm Paselas at the Same psi, and at a lower Psi and see what you think the difference is.

I don't know what the psi rating is on sidewall of the 32mm Paselas, but do be careful about exceeding that by any appreciable amount. The forces trying to separate the tire from the rim increase with pressure but also with cross-sectional diameter.

noglider
02-18-11, 12:47 PM
I think the reason narrow tires ride better is that they had more supple sidewalls. Until recently, it wasn't possible to make a wide tire with a supple sidewall. But it is now. Now that it's possible, people are saying they're the bee's knees.

I'm about to try some 32mm Paselas. The sidewalls are very thin. If I could justify spending on the Grand Bois tires, I'm sure I'd love them, but the Pasela is still a darned nice tire.

Zaphod Beeblebrox
02-18-11, 12:50 PM
I don't know what the psi rating is on sidewall of the 32mm Paselas, but do be careful about exceeding that by any appreciable amount. The forces trying to separate the tire from the rim increase with pressure but also with cross-sectional diameter.

On hooked rims I haven't had any issues running the 32's at 90 or 100psi, but I have blown them off of some old non-hooked rims at those pressures.

ColonelJLloyd
02-18-11, 12:55 PM
As an aside: I mounted another pair of 700c x 32mm Pasela TGs last night. This time they went on CR-18s. The actual width was the same as the 32s on the VO Diagonales. ~29-29.5mm wide.

Hydrated
02-18-11, 12:56 PM
I don't believe anyone's done a really academically rigorous, quantitative/qualitiative analysis of rolling resistance vs. tire size vs. contact surface quality. I would have no idea where to start.

Maybe the bicycle industry hasn't done this kind of anlysis... but rest assured that auto and aircraft designers have. And the physics all apply to bikes too.

This thread reminds me of one that I read a couple of years ago in which a guy was wondering why he couldn't keep up with the roadies on his loaded mountain bike. The debate turned to tires... wide vs. narrow... and I had to chime in. I have deleted some of the thread specific information, so pardon me if the post seems a little schizophrenic in places:

Ahhhhh... As an engineer, I love these threads! There are many factors that impact your speed, but you have to make concessions to get there.

For decades aircraft designers have known that a tire's contact patch size is a function of effective load and tire pressure. Lighter loads or higher pressures yield a smaller contact patch... Tire width has NOTHING to do with contact patch size. Width determines shape of the contact patch, but not size.

The rotational weight of the tire won't impact top speed once the rider has overcome the tire's inertia and gotten it rolling at speed. That's why a heavier tire makes it difficult to accelerate quickly to grab the tail of that group... inertia puts the brakes on you. But that extra tire weight is far from irrelevant. More weight enlarges that contact patch and makes it harder to maintain speed, even on a flat stretch. Why?

We know that tire width has nothing to do with the SIZE of the contact patch... so where is the difference? It's in the SHAPE that the difference lies. A wide tire will have a short but wide contact area, and a skinny tire will use a thin but loooong patch. And both tires will deflect and squish down to put that rubber on the road lengthwise. In other words, the sidewall has to deflect and bend enough to let that tread patch touch enough of its length to complete the contact patch. The thinner the tire, the more the sidewall has to deflect along its length. So a thin tire with heavy loads (more weight) or low pressures will be very inefficient because that sidewall deflection eats up energy like crazy. That's why most thin tires run high pressures... to minimize contact area and consequently minimize energy wasted overcoming tire deflection.

This sounds counterintuitive, but: A wide tire will be more efficient than a thin tire running AT THE SAME PRESSURE.

This works because the wide contact patch of a wide tire requires less sidewall deflection along its length in order to create a given size patch. Less energy wasted. The problem is that wide tires normally run at much lower pressures... and what do low pressures give us? Bigger contact patches... and more sidewall deflection. As a matter of fact, most heavier riders will be able to ride faster and longer on 25's or 27's than on those 20 or 23C's that the high zoot racing bikes come equipped with.

If we could find 2 inch wide tires running at 140PSI we'd be in business. They wouldn't accelerate for crap, but you could push those babies at speed all day long!

So to sum it all up:

It's all about the weight and tires on your bike. The rotating weight prevents you from accelerating to catch onto the group... and then those fat low pressure tires suck your tanks dry trying to keep up at speed. And that heavy mountain bike frame creates big contact patches to suck away even more energy.

due ruote
02-18-11, 01:13 PM
If you want to do the same comparison at home you'd want to try a pair of 28mm Paselas at Some psi as a reference (call it 90 if you like), and then try a pair of 32mm Paselas at the Same psi, and at a lower Psi and see what you think the difference is.

While you're at it, repeat the test on one of these and see how your results vary.
http://www.bikecult.com/works/rollers/1900rollers.jpg

XR2
02-18-11, 01:16 PM
Now there's some rollers I could stay on.

Just ride
Now where would BikeForums be if we did that?

Zaphod Beeblebrox
02-18-11, 01:43 PM
Is that some sort of competition going on with those rollers?

bobbycorno
02-18-11, 02:40 PM
I think the reason narrow tires ride better is that they had more supple sidewalls. Until recently, it wasn't possible to make a wide tire with a supple sidewall. But it is now. Now that it's possible, people are saying they're the bee's knees.

I'm about to try some 32mm Paselas. The sidewalls are very thin. If I could justify spending on the Grand Bois tires, I'm sure I'd love them, but the Pasela is still a darned nice tire.

I'm thinking the problem's been more of a perception that there's no market for fast, wide tires. From what I understand, back in the early post-WWII period there were high-performance 650b's (including hand-made ones!) available in France. Those went away with the wholesale move to 700c in the intervening years. Fortunately, Grand Bois, Pacenti and SOMA ignored the "common wisdom", and started making high-performance, big, cushy tires. And, voila! There IS a market!

And I agree wholeheartedly with your evaluation of the Pasela. One of the most underrated tires out there, especially in the wider sizes. I recently replaced the 700x35c Paselas on my Kog P/R with 32s, because they were available. What a disappointment! They feel harsh and slow by comparison. Soon as those wear out, it's back to 35's for me!

As an aside, I've got "650x38b" (really 35.5-36mm wide) SOMA B-Lines on my brevet bike. They look like a 650b, folding bead Pasela (non TourGard, thank the tire gods!). Dunno why, but they impress me as significantly faster than my 700x35c Paselas. A lot of that could be the bike they're on, tho' (a Reynolds 531cs Trek vs a Kogswell P/R). Whatever the reason, they've got me thinking seriously of eventually ditching 700c all together.

SP
Bend, OR

bobbycorno
02-18-11, 02:55 PM
Oh and just to demonstrate that wide tires are not necessarily slow, the fastest North American finisher in PBP 2007 covered the 1200k (750mi) in 50 hours flat. On a 30+ year-old steel bike. With 700x30c tires, metal fenders, a canvas handlebar bag and dynohub lighting. Does anyone honestly think the bike was holding him back? He (Jan Heine) doesn't.

(And before anyone states the obvious, yes, I know the motor makes a HUGE difference. I'm just sayin' that "whatever the pros are using this week" isn't always the best choice.)

SP
Bend, OR

Zaphod Beeblebrox
02-18-11, 03:07 PM
As an aside, I've got "650x38b" (really 35.5-36mm wide) SOMA B-Lines on my brevet bike. They look like a 650b, folding bead Pasela (non TourGard, thank the tire gods!). Dunno why, but they impress me as significantly faster than my 700x35c Paselas. A lot of that could be the bike they're on, tho' (a Reynolds 531cs Trek vs a Kogswell P/R). Whatever the reason, they've got me thinking seriously of eventually ditching 700c all together.

This comment got me thinking about the comment Jan Heine has about the 650x38 Grand Bois "Ourson"

To bring this tire to market quickly, without the investment for a new mold, Grand Bois decided to use the molds for the Panaracer “Col de la Vie” 584 x 38 mm (650B) tires. As a result, the Grand Bois “Ourson” has the same “micro-knob” tread pattern as the “Col de la Vie”, but it uses the more supple Grand Bois casing (my emphasis)

Leads me to assume that while Grand Bois Tires are being made by Panaracer, and in some cases share molds (for the rubber) they are not using the same casing as the Pasela. Perhaps the same is true for the SOMA B-Lines...maybe they saved a little money and used the Pasela molds but with a better casing.

Bobby, if you haven't had the good fortune to try the Grand Bois "Cypres" in 700x32 (they actually measure more like 35's) I'd highly recommend you give it a go if you ever really decide to ditch 700c....sort of a "last Hurrah" if you will :thumb:

USAZorro
02-18-11, 03:19 PM
Maybe the bicycle industry hasn't done this kind of anlysis... but rest assured that auto and aircraft designers have. And the physics all apply to bikes too.

This thread reminds me of one that I read a couple of years ago in which a guy was wondering why he couldn't keep up with the roadies on his loaded mountain bike. The debate turned to tires... wide vs. narrow... and I had to chime in. I have deleted some of the thread specific information, so pardon me if the post seems a little schizophrenic in places:

This is the most succinct, and plausible reasoning I've seen on the topic. :thumb:

randyjawa
02-19-11, 03:12 AM
It seems to me if wider, fatter tires are faster, then every participant, in the Tour de France would be running them. But they don't. Did anyone ever wonder why? Perhaps because they are not faster:-(

tcs
02-19-11, 05:38 AM
But what if you had really light, flyweight tires/wheels, pumped up tight, and to keep the weight of the bike+rider from having to lift up and over pavement irregularities there was, I dunno, some way to handle it other than sidewall flex?

I know. Crazy talk (http://www.moultonbicycles.co.uk/heritage.html).

Chris_in_Miami
02-19-11, 07:21 AM
This is the most succinct, and plausible reasoning I've seen on the topic. :thumb:

+1, that was the best explanation I've seen to date, and easily understandable to a non-engineer. Thanks Hydrated!

iab
02-19-11, 08:16 AM
It seems to me if wider, fatter tires are faster, then every participant, in the Tour de France would be running them. But they don't. Did anyone ever wonder why? Perhaps because they are not faster:-(

Why did Coppi and Bartali ride with steel cranks when lightweight, indestructable aluminum cranks were available?

Why did Cinelli only produce steel stems until 1960 when he personally rode with an aluminum stem in the 1930s?

Product development 101: Perception = Reality

andychrist
02-19-11, 09:44 AM
Quite aside from the issues of rolling resistance and acceleration, there is yet another real world difference between wide and narrow tires: wind resistance. A narrower tire will slice through the air more easily than a wide one. Perhaps that advantage, in combination with the easier acceleration gained from the lowered mass, is greater than any that might be gained though optimized rolling resistance. Dunno, but this could at least partially explain the general preference for skinny tires among racers if such were the case. Anyway, you certainly wouldn't notice as much of a difference indoors, working out on rollers, as you would out on the road, against the wind.

triplebutted
02-19-11, 09:53 AM
My head is spinning with all this information! I think I'll just take a bigger dosage of EPO today and wing it!

repechage
02-19-11, 10:21 AM
a long time ago now, I was on my Ritchey mtb. on the road, fitted with Scott mtb. bars and Tom Slicks. I was climbing a nearby hill, and two cat 3 guys turned in from a cross street about 100 yards ahead, always fun with pacers in front, they were working, and soon realized I was gaining, the race was on, within 2 miles, they were toast, and as I passed they mumbled about how a guy on a mtb. was killing them. They were quite demoralized, especially considering my bike was 6 to 8 lbs. heavier.

tru
02-19-11, 10:36 AM
Quite aside from the issues of rolling resistance and acceleration, there is yet another real world difference between wide and narrow tires: wind resistance. A narrower tire will slice through the air more easily than a wide one. Perhaps that advantage, in combination with the easier acceleration gained from the lowered mass, is greater than any that might be gained though optimized rolling resistance. Dunno, but this could at least partially explain the general preference for skinny tires among racers if such were the case. Anyway, you certainly wouldn't notice as much of a difference indoors, working out on rollers, as you would out on the road, against the wind.

then why are the pros going from 23s to 25s as of late?

here's the thing: the pros ride whatever stuff their sponsors give them. give them wider tires and a reason to do so, they're going to use them.

StanSeven
02-19-11, 11:27 AM
then why are the pros going from 23s to 25s as of late?

here's the thing: the pros ride whatever stuff their sponsors give them. give them wider tires and a reason to do so, they're going to use them.

Rims are getting wider. You don't want the tires to be significantly smaller or larger than the rim. So wider tires are used with wider rims.

iab
02-19-11, 11:31 AM
Quite aside from the issues of rolling resistance and acceleration, there is yet another real world difference between wide and narrow tires: wind resistance. A narrower tire will slice through the air more easily than a wide one. Perhaps that advantage, in combination with the easier acceleration gained from the lowered mass, is greater than any that might be gained though optimized rolling resistance. Dunno, but this could at least partially explain the general preference for skinny tires among racers if such were the case. Anyway, you certainly wouldn't notice as much of a difference indoors, working out on rollers, as you would out on the road, against the wind.

My guess, since you aren't offering any real data either, is that going from a 23 mm diameter to 25 or 27 mm tire isn't going to change wind resistance by any significant amount. The increase in cross-sectional area is miniscule when compared to the remaining bike and human on it. In a peloton, I'll guarantee it makes absolutely no difference.

Rotational mass only matters under acceleration. So if you are doing a lot of climbing, heavier tires could pose a penalty. On the flats, not a chance.

Bottom line, it is all speculation without real data.