Myth: Wide Tires Need Wide Rims:

[Calnago]

Does anyone actually experiment for real with these things. For instance, find a nice 7%+ grade, longer the better. Alpe D’Huez would do nicely. Now, throw on your nice fat 30mm tires inflated to maybe an appropriate 55-60psi max (if you’re heavy). I used to inflate my fully loaded touring bike (95lbs fully laden with gear) plus my 200lbs on top of that to around 60-65psi if I recall. So if you’re lighter, go less. Now, for comparison sake take a standard width wheel with a nice 23mm tire on it and pump it up to say, for my weight, I’d use around 110psi rear, somewhat less in the front (say 103psi). Now ride up the hill and tell me that that the 23mm tire isn’t going to be much more efficient at getting you to the top. Not talking comfort here, a big balloon is of course going to feel pretty cush. But it’s also going to be dragging you down and feel pretty mushy in comparison to the 23mm. Power transfer, road feel, etc., is going to be much better on the 23mm. On my touring bike I’ve tried bigger tires (37mm), but they were sluggish feeling. In the same sense that going much larger than a 25mm tubular on my road bikes feels. Now I do feel that you can get similar comfort, and much better handling, on a tubular tire over any clincher. I’d say comfort wise a nice 25mm tubular might compare favorably to a 28mm clincher.
I am fascinated over just how big people are willing to go in a road tire on a nice road bike before they finally say “Hey, ya know what, maybe this is too fat now and the pressures too low”. Not sure where it will end. But my personal sweet spot for my road bikes is definitely in the 25mm range. Tried the 27mm Vlanderens. Nice tires but not needed on the roads I ride and I prefer the feel of the 25mm Areeneberg/Roubaix. Gave the Vlaanderens away and replaced with the 26mm Specialized S-Works Turbo. Super supple tire, to the point I may run even slightly higher pressure in them than the 25mm Arrenberg. Current pressures in my Arrenbergs... 100psi rear/ 90psi front. So nice.

[Mr.Gib]

@calnago, I've basically done what you are suggesting. Climbed mountain after mountain on 25.mm and done it also on 30mm. The only loss is in carrying the extra weight uphill. Rate of vertical ascent is pretty constant at set power. And FWIW at 170lb on 30mm tires, I don't like to go lower then 60psi. If roads are good then 65 - 68psi. Huge gains going downhill though if the roads are bad. Worth noting that tire quality is even more important than pressure (within reasonable psi range). Supple tire is better even when a bit harder then optimum.

IMO what you need to experience is a fat 28 or 30mm high end supple clicher on a really wide rim (21 -22 mm internal). Try that set up at 70 psi on a technical rough descent and I promise you will look at tire size and pressure very differently. The feeling is so secure and the traction so good, I simply will not go to the mountains with any other setup.

[Calnago]

Exactly, and the higher the weight, the more that weight and gravity will play a roll. And going up hill, the friction between the tire and the road (rolling resistance) is not insignificant. I liken it to having your bike on a trainer where the rear wheel is tensioned against a roller. Increasing the tension of the roller against the rear wheel increase the resistance greatly, kind of like riding up hill against gravity. And the more surface area in contact the more friction. I don’t know... I’ve often thought about actually timing the difference when I had my Vlanderens but just could never be bothered. I know which tires I preferred riding on and that was all I needed for my decision. The Vlanderens have a new home. Great tires, just not for me, at lest not for the vast majority of my riding.

[Alexbn921]

Calngo, there is no free lunch and the bigger tires weight more, compress more and have a bigger contact patch.

For a pure climbing tire smaller is better, same for smooth time trails. Reducing rotational weight has the biggest difference at climbing speed and oscillations.

With that said the roads around here are rough. Road impact fatigue plays a big role after a couple hours. Coming down Mount Diablo I have heard riders yell ouch form hitting repaired sections of the road. For the most part 25’s would be “faster” overall with comfort and descending speed as the trade off.

There is no perfect size for every situation. I’m seriously considering 30’s, but don’t know if the befits outweigh the negatives.

The GP5000 TL 28’s don’t inspire the same confidence as the Pro1 28’s I had before. Looking forward to trying the corsa g2.0 tlr or specialized rapid air in 28 of course.

[Lieblingsleguan]

Exactly, and the higher the weight, the more that weight and gravity will play a roll. And going up hill, the friction between the tire and the road (rolling resistance) is not insignificant. I liken it to having your bike on a trainer where the rear wheel is tensioned against a roller. Increasing the tension of the roller against the rear wheel increase the resistance greatly, kind of like riding up hill against gravity. And the more surface area in contact the more friction. I don’t know... I’ve often thought about actually timing the difference when I had my Vlanderens but just could never be bothered. I know which tires I preferred riding on and that was all I needed for my decision. The Vlanderens have a new home. Great tires, just not for me, at lest not for the vast majority of my riding.

If you increase the tension of the roller against your rear wheel, you do the same as increasing the weight on your rear wheel on the road. Rolling resistance is approximately normal force times the rolling resistance coefficient.
Now, additionally, the curvature of your "road" is very big in that scenario; if you compare rolling resistance measurements on different drum sizes, rolling resistance will go up the smaller the drum is and of course, your "drum" on the roller will be smaller than anything anyone would want to use for a measurement that can be compared to actual road use.

Also, do not mix up rolling resistance and friction between tire and road. Rolling resistance on a smooth road is mainly material hysteresis and only in a small part some sliding friction on the outside edges of your contact patch. Therefore, a grippier tire will not necessarily have more rolling resistance.

[Mr.Gib]

Exactly, and the higher the weight, the more that weight and gravity will play a roll.

the bigger tires are about 25 - 35 gram heavier. 50 - 70 grams for the set. I can lose that much weight by farting. Of course we count every gram here, but the comfort and safety advantage huge IMO. That's a worthwhile tradeoff.

And your bit about increased rolling resistance, well that depends on road surface. Very possible the big soft tire will roll faster if the road is rough. Silca's data suggests losses even on good surface is miniscule.

[Calnago]

Not uphill it won’t. The weight aspect was not about the tire, more the effect of total weight for a larger person having much more of an effect going up hill than for a lighter guy. Things are just harder for us. Lol.
Anyway, it’s really such a silly thing. I’m going to ride the tires I like the feel of, first and foremost. Always. I’m not racing. And seems even at the pro racing level, you’re not seeing them running larger than 25-26mm unless they’re at Roubaix. Plus, their 25mm tubulars are pretty much 25mm, still considerably lower volume than a 25mm clincher on a wider rim, let alone a 28mm or even larger clincher. I just don’t think the pros are so clueless that they would be foregoing all this “free speed” etc. if it were at all significant.

[Lieblingsleguan]

Not uphill it won’t. The weight aspect was not about the tire, more the effect of total weight for a larger person having much more of an effect going up hill than for a lighter guy. Things are just harder for us. Lol.
Anyway, it’s really such a silly thing. I’m going to ride the tires I like the feel of, first and foremost. Always. I’m not racing. And seems even at the pro racing level, you’re not seeing them running larger than 25-26mm unless they’re at Roubaix. Plus, their 25mm tubulars are pretty much 25mm, still considerably lower volume than a 25mm clincher on a wider rim, let alone a 28mm or even larger clincher. I just don’t think the pros are so clueless that they would be foregoing all this “free speed” etc. if it were at all significant.

We are talking rolling resistance here. The pros don't go much wider because of aerodynamics also. At their usual speed, even uphill, that matters.

Also, the peloton is experimenting with tubeless tires and because they are faster than a tubular, they are starting to become the norm in time trials.
Interestingly, they are not going for effective 25mm tires, they are using nominal 25mm tires that come out wider on wide rims. As long as the rim is wide enough, that's fine aerodynamically.

Some people in the business predict that tubeless tires will have replaced tubulars in the peloton in five years. I don't know if that's true, it depends on how high the teams rate the fact that you can run a tubular flat for a while and how long it takes that teams are willing to leave tried and tested technology for some Watts of rolling resistance.

[Calnago]

We are talking rolling resistance here. The pros don't go much wider because of aerodynamics also. At their usual speed, even uphill, that matters.

Also, the peloton is experimenting with tubeless tires and because they are faster than a tubular, they are starting to become the norm in time trials.
Interestingly, they are not going for effective 25mm tires, they are using nominal 25mm tires that come out wider on wide rims. As long as the rim is wide enough, that's fine aerodynamically.

Some people in the business predict that tubeless tires will have replaced tubulars in the peloton in five years. I don't know if that's true, it depends on how high the teams rate the fact that you can run a tubular flat for a while and how long it takes that teams are willing to leave tried and tested technology for some Watts of rolling resistance.

Now you’re saying the pros don’t go much wider because of aerodynamics. Ok, but if on balance, all things considered, wider is better, why wouldn’t they? Anyway, I’m not getting into the aero aspect, just something to ponder.

You say that tubeless is “starting to become the norm in time trials”?? Hmmm. What do you define as the norm... 80%?... 50% certainly isn’t the “norm” and I don’t think, even in time trials that tubeless at this year’s Tour de France was anywhere even “starting” to become the norm. Maybe you can tell us what percentage of the teams used them in TT’s. But sure, it may be in the future, it’s a time trial, handling characteristics don’t really matter so much as they would in a mountain stage.
Also, the nominal size of a tubular, is in fact very very close to the actual size as it’s not dependent on the size of the internal bead with of a clincher rim, which is all over the board. And the requirements of a tire in a time trial are quite different than what one would want in the twisty mountain descents. Yet they seem to still prefer the 25mm tubulars. They could just as easily run 28mm tubulars if they chose to do so, but I think you’d be hard pressed to find any teams running 28mm tubulars in any of this year’s Grand Tours.
And as far as what “people in the business” are predicting goes, well while it is true that they ultimately make the decisions to produce what they want to produce, 10 years ago they were predicting that there would be only disc brakes in 5 years, yet at this point the only pros running disc are those that don’t have a choice due to sponsor demands (with Specialized and Trek leading that charge). Not to start a disc discussion but just pointing out an example of predictions by the Marketing folks that didn’t really hold water.
So, it’s fine if you want to run fat tires etc, tubeless, tubed or tubular. I’m not trying to say you shouldn’t. If they meet your needs and you prefer them then by all means you should. And same for me, I know what meets my needs and what I prefer. That’s all.

[Lieblingsleguan]

We are talking rolling resistance here. The pros don't go much wider because of aerodynamics also. At their usual speed, even uphill, that matters.

Also, the peloton is experimenting with tubeless tires and because they are faster than a tubular, they are starting to become the norm in time trials.
Interestingly, they are not going for effective 25mm tires, they are using nominal 25mm tires that come out wider on wide rims. As long as the rim is wide enough, that's fine aerodynamically.

Some people in the business predict that tubeless tires will have replaced tubulars in the peloton in five years. I don't know if that's true, it depends on how high the teams rate the fact that you can run a tubular flat for a while and how long it takes that teams are willing to leave tried and tested technology for some Watts of rolling resistance.

Now you’re saying the pros don’t go much wider because of aerodynamics. Ok, but if on balance, all things considered, wider is better, why wouldn’t they? Anyway, I’m not getting into the aero aspect, just something to ponder.

You say that tubeless is “starting to become the norm in time trials”?? Hmmm. What do you define as the norm... 80%?... 50% certainly isn’t the “norm” and I don’t think, even in time trials that tubeless at this year’s Tour de France was anywhere even “starting” to become the norm. Maybe you can tell us what percentage of the teams used them in TT’s. But sure, it may be in the future, it’s a time trial, handling characteristics don’t really matter so much as they would in a mountain stage.
Also, the nominal size of a tubular, is in fact very very close to the actual size as it’s not dependent on the size of the internal bead with of a clincher rim, which is all over the board. And the requirements of a tire in a time trial are quite different than what one would want in the twisty mountain descents. Yet they seem to still prefer the 25mm tubulars. They could just as easily run 28mm tubulars if they chose to do so, but I think you’d be hard pressed to find any teams running 28mm tubulars in any of this year’s Grand Tours.
And as far as what “people in the business” are predicting goes, well while it is true that they ultimately make the decisions to produce what they want to produce, 10 years ago they were predicting that there would be only disc brakes in 5 years, yet at this point the only pros running disc are those that don’t have a choice due to sponsor demands (with Specialized and Trek leading that charge). Not to start a disc discussion but just pointing out an example of predictions by the Marketing folks that didn’t really hold water.
So, it’s fine if you want to run fat tires etc, tubeless, tubed or tubular. I’m not trying to say you shouldn’t. If they meet your needs and you prefer them then by all means you should. And same for me, I know what meets my needs and what I prefer. That’s all.

Of course, aerodynamics is important when you want to understand why pros choose what they choose. They are not going by rolling resistance alone, they are going by overall performance for their needs. I never claimed anything else.
There are few tubular wheels that form a good aerodynamic system with a 28mm tub, but there are quite a few that do with a tubeless tire coming out at 26-27mm.

I wrote "starting to become the norm" so we are far away of 50%. If we were at 50% or more, we'd be deep in the process of it "becoming the norm". Cyclingtips had a nice piece about tubeless tires at this year's TdF:
https://cyclingtips.com/2019/07/tubeles ... de-france/

Please show me a source where someone claimed 10 years ago that disc brakes would be the norm in 5 years. I don't buy that. Maybe 3-5 years ago someone said that (and wouldn't be totally wrong). When were you even able to buy a roadbike disc brake group?
Also, the comparison isn't perfectly chosen as tubeless tires give an (albeit small) performance benefit above tubulars, disc brakes don't make you faster.

[Mr.Gib]

Now you’re saying the pros don’t go much wider because of aerodynamics. Ok, but if on balance, all things considered, wider is better, why wouldn’t they?

Why wouldn't they? If you're racing on good roads there is no reason to go above 25mm. But elite level athletes racing on bad roads do go wider. Why ignore Strada Bianchi, Paris Roubaix, etc. ?

[Calnago]

...There are few tubular wheels that form a good aerodynamic system with a 28mm tub, but there are quite a few that do with a tubeless tire coming out at 26-27mm.
...

If you define a “good aerodynamic system” as one where the tire juts straight up from the rim wall, then there will probably never be a tubular wheel that meets that requirement without negating the benefits of a tubular. Tubulars have a round profile, always have always will. In order for that performance sapping “non aero” gap between tire and rim to be eliminated in a tubular, the sides of the rim would have to come up half way around the tubular to it widest point, basically burying the tubular in the rim and taking away much of its ability to “move” with the ever changing conditions of the road/tire interface. May as well ride clinchers (tubed or tubeless) in that case. Yet, despite the inherent non-aeroness of tubulars they remain the overwhelming choice at the pro level, still. And the reason goes far beyond that they are unquestionably safer etc., and is more about how they handle. And that’s why I prefer them too. They just feel oh so nice. And I’ll choose ride quality all day long over all else for my personal riding experience, especially since it’s something I can actually feel and discern a difference from the alternative. Whether a tire has an aero interface with the rim is something I’m afraid I can only discern if someone’s showing me a chart from some lab test that seems to indicate a minuscule difference in whatever. That’s nice, but give me something I can actually feel on the road any day over something on a chart that I can’t.
Ok, that’s all I got. We all get to ride what we like and choice is still available. That’s what I like most... choice.

[Calnago]

Now you’re saying the pros don’t go much wider because of aerodynamics. Ok, but if on balance, all things considered, wider is better, why wouldn’t they?

Why wouldn't they? If you're racing on good roads there is no reason to go above 25mm. But elite level athletes racing on bad roads do go wider. Why ignore Strada Bianchi, Paris Roubaix, etc. ?

I didn’t ignore Roubaix, I even called it out as the exception. So yes, where the roads warrant it, go bigger, for sure. But then you get into a subjective discussion as to how rough is rough enough to warrant going bigger so you’re back to discussing individual preferences.

[Lugan]

IMO what you need to experience is a fat 28 or 30mm high end supple clicher on a really wide rim (21 -22 mm internal). Try that set up at 70 psi on a technical rough descent and I promise you will look at tire size and pressure very differently. The feeling is so secure and the traction so good, I simply will not go to the mountains with any other setup.

I discovered exactly that this year. Got a new bike and spec'd it with Enve 3.4 Disc (21mm internal width) and Schwalbe Pro One 28c tires. I weigh 81kg and run them usually at 60f/70r, which makes the tires a little over 30mm actual width. They are simply amazing going downhill, especially when it's steep and rough.

@Calnago, IIRC you and I live near each other in the Seattle area. For reference, steep and rough descents like the Cougar Mountain Zoo road and others around Issaquah and the Sammamish plateau are what I am talking about.

Whether I am faster or slower on those wheels is more difficult to measure, but my sense from a season of ride data is that I am actually overall slower on that bike and those wheels/tires than my more aero and narrow options. But with multiple factors different between the bikes, it is hard to pinpoint whether it's true.

[Calnago]

Fair points, for sure. There’s nothing worse than descending at a speed where you know that hitting an unforeseen rough patch on narrow hard tires and rims is going to cause havoc. If I don’t know the road I’m always erring on the side of caution, and even when I do know the road, I’m too old to end up in a hospital again. Not sure if you know the Old Blewitt Pass road heading east, but we used to do that at least once a year (instead of the main Highway) and for sure I would have preferred nice fat tires on the backside of that, and would still use caution. But for the rest of the 3 day ride I would want my normal 25mm’s. If we could only have a set of changeable wheels and tires at our disposable on any given ride. One for going up slowly, one for coming down fast, maybe one for aero on the flats etc. but usually bike rides are some combination and we ride the art of wheels on our bike when we left. So let the differences exist I say... it gives us all something to talk about at the coffee shop.