McBTC

The OP is not convinced but there's quite a few details along the way--e.g., the newer bikes but not the latest) have relatively narrow wheels, to the point where going from 23s to 25s being better has morphed into newer bikes with wider rims, giving rise to whether going from 25s to 28s might be better. With that we've answered a few questions: if you've got rims made for 23/25 tires, going to 28s probably doesn't get you much as far as performance is concerned. If you got wider rims (which you migtht beginning ~2015) riding 28s at the same pressure probably will give you a better ride (assuming you don't have clearance issues) and you'll be just as fast even tho you'll feel slower because you're not getting beat up so much.

noglider 

I think [MENTION=61571]Spoonrobot[/MENTION]'s post shows that there is a point of diminishing returns as we choose wider and wider tires. Where that point is depends on the application, whether you're commuting, hauling, racing, whatever.

mletts

There is certainly a scientific, "most right" answer to whether or not bigger is better in respect to the relationship between tire size and speed but, personally, I think that whatever works best for the individual is best. Each individual has what I think of as an equation that is unique to them; the equation takes into account price, terrain, endurance, and various other variables at varying degrees. However, let's be honest, in aggregate- these differences are marginal- people are rarely ever that unique. So, perhaps, it is best to start by doing what everyone else does and experiment later? People tend to converge for a reason.

Tl;dr: Average opinions and preferences exist for a reason (usually) but, at the end of the day, do what feels right; this might mean trying out what other people are doing first, though, so that you don't waste resources. In this case, ride whatever tire you want.

Kontact

I had rather thought the point of this discussion was that people used to ride whatever they wanted, and they ended up on 20c tires at 130psi. So instead of repeating that mistake, why not apply a little science?

cdmurphy

What I've gotten out of all this reasearch into wider tires, is that suspension losses are real, and had been ignored by most of the industry until fairly recently. (Thanks to the ease of drum or roller testing). Light weight, supple, wide tires are an excellent way to deal with road irregularities, and lead to speed increases up to the point where road irregularities stop disturbing the bike/rider. (As long as they dont add.much rolling resistance compared to a skinny tire). After that, their increased width and weight isn't doing you any favors.

​​​​​​I think ideal tire width is a function of road quality. (By ideal, I mean lowest total rolling + suspension losses. Aero should factor in too, but that has a lot to do with average speeds. I'm a 13-15 mph average kind of rider, so it doesn't matter as much to me.)

Rougher roads / surfaces benefit tires with higher volumes. If all your riding is on a velodrome, or very smooth asphalt, there really isn't much to be gained over maybe 25mm. Lots of gravel, dirt roads, or crappy pavement? Bigger is better.

Anecdotally, I have one section of a mild climb where the pavement switches from good-ish, to a surface that has been seal coated / gravel topped once or twice, but it's worn away unevenly. It doesn't look very rough, but it is. (The surface has small variations of about 1/2", on the scale of 1-2"). The grade remains constant at about 5%, but every time I would hit the transition on 28 or 30mm tires, I would immediately slow down by ~2 mph. The first 2 or 3 times I looked down to see if I'd flatted, it was that abrupt. I'd guess the rougher surface cost me an additional 50-75 watts. Doing the same climb on 35mm Voyager Hypers, or 38mm Gravel Kings was a revelation. They weren't much if any faster on the smooth sections, but I would hit that transition, and nothing much would change. I'm sure it still cost a bit of energy, but nothing like before. Maybe an additional 10 watts. I'll gladly trade little bit of aero drag, and possibly a few % on the smooth stuff for almost immunity to bumps and cracks and crappy pavement. (Which is a lot of it here in San Diego, especially on the back roads.)

noglider 

Good points, [MENTION=408183]cdmurphy[/MENTION]. Very interesting about your climb.

And I think I went down to about the point of diminishing returns in my recent tire swap on my tandem. 37mm tires are wide enough, and I think wider tires won't help, at least not much. We don't go fast on it, anyway. My wife isn't very strong. On a single bike, she averages 10,5 mph, maximum. Yesterday, we rode the tandem, and our average was 11.5 mph. As a team, there isn't room to do much better than that.

63rickert

A new point not touched in these pages. New bikes come with disc brakes. Forks for disc brakes are and have to be very stiff. The bikes ride way too harsh unless you use wider tires and lower pressure. Normally I pay no attention at all to new bikes but hey, it's Tour time and they are all on discs now. The bikes are completely redesigned to sell some discs. Just read a long advertorial by Gerard Vroomen, the man responsible for inflicting Cervelo upon us. His new 3T Strada Due bicycle is designed from the beginning around tires of 27mm to 30mm. He thinks you should go for 30. Whatever you think of that guy he has his finger on the pulse and if he says we shall all shortly be riding 30 it is likely so. If the frame is a slab of rigid plastic and the wheels are slabs of rigid plastic there really is nothing to make the bike rideable but tires. This is fine with me because all my bikes were designed around wide tubulars and fatter with fenders in winter, if the pros are all on 30mm tubulars more possibilities for discounted tires that work just right on classics.

McBTC

Good point about the rigidness of modern CF forks. Unlike the Icon CF forks on my old Lemond -- which pretty much looked like cromo forks -- the CF blades on my alloy rig seem to have zero shock absorption when shoed with 25s but the forks have room for 28s which I'm happy to take advantage of even if only on the front. My hands can tell the difference.

Kontact

And the advocates of discs will tell you they don't ride any different than bikes designed for rim brakes, but that's only when comparing rim brake bikes that also have virtually no fork based suspension. Fat tires are the new fix to a non-problem.

chelvel

I tried to measure frequency of loaded tires (loaded by me) at home with the help of video recording at different pressures (1bar and 2bar - both with front and back). Every time it was 3Hz.

After some thinking I came to this: this is a frequency of the heaviest part - me, pushing the handlebar hard, standing on the pedals. Tire frequency still have to be measured somehow. Ideas?

Kontact

What is the source of the frequency you are looking for? A particular rough surface the tire is riding on? Does a material that acts a bit like a fluid have a frequency?

chelvel

Air in the tire is a spring. I want to measure it's frequency loaded by the rider.

Kontact

If a spring's spring rate is "faster" than the frequency of whatever is acting on it, does it have a frequency to measure? You can tap a spring/tire with a hammer and measure that frequency, but when you preload either and keep them in constant contact with a lower frequency preload, I don't think there's going to be anything to measure.

63rickert

It's a non-problem if you have good forks. Since one and all have abandoned any pretense of designing good forks we have a problem. Heine says he can feel the difference between a disc fork and a rim fork even when shod with 48mm extralight tires of his own design.

Lots of bike design problems are non-problems if you just leave out one or two factors. I have no problem fitting moderately wide tires on any of my bikes .They were all designed when design vernacular assumed riders wanted to put a wheel in there and before anyone saw a virtue in bikes with severely limited function. The Gerard Vroomen bike mentioned above will in fact function if you go and do something crazy like putting a 700x25 tire in it. But it is not meant to work well that way. A 700x32 simply will not fit.

'Disc advocates' are just shills. The hardware is getting better, the new brakes do work adequately. Five years ago that was just not the case and it made no difference at all to 'advocates'. The limits on braking are still available traction/pavement friction and pitchover. Bikes stop at 0.5 to 0.6g and have for a long time. It ain't getting any better. In most circumstances wide tires will get you a hair closer to the higher end of the spectrum but that's not a big thing.

prathmann

Sure, any spring that's being driven by a force at a given frequency will just oscillate at that frequency. But the 'spring frequency' is the natural frequency when the spring is initially displaced and then left free to vibrate. A tire is a pretty heavily damped spring so the vibration will quickly die out. But one could ride the bike off a short drop (say an inch, like a short curb) and measure the frequency at which it vibrates immediately after the impact. As I indicated in post #195 , this natural frequency should be about
f = [sqrt(g/x)]/(2 * pi) where g is 9.8m/s^2 and x is the vertical distance (in meters) by which the tire is compressed by the weight of the rider+bike.

tashi

The point of discs on road and CX bikes isn't to increase the total braking force available at the tire/road contact point, that's easily achieved with a quality road caliper. Discs are good for consistent performance under all weather conditions, better modulation/easier application (less force at the lever), less wear on rims and, if integrated into fork design, lighter and more compliant forks. A more powerful brake isn't required for road bikes, but a more powerful brake is easier to control with less effort from the rider. The benefits of discs aren't readily apparent if you always ride flat terrain in good weather, but big descents, rough terrain and poor weather make their advantages far more apparent.

chelvel

Me too. So I'm asking: Ideas?

chelvel

I like that idea. Thanks!

Kontact

But the forks and bikes aren't lighter - they are heavier because of the increased load on the fork blades and having a redundant set of brake tracks.

If there isn't anything to measure, why try to measure it? Tires are used under constant load, so why would you want to record their unloaded frequency?

tashi

I may be wrong about the frame and fork weights, I haven't bothered to research it. I doubt that the difference is significant however, and some weight gains have proven to be worth it, somethimes even paying off in speed.

Disc rims don't have brake tracks, as a result they can actually be designed to be lighter.

Kontact

But they aren't, because brake tracks on normal rims don't add any weight.

Whether discs are better as brakes or not, they require poor riding, stiff forks, a loss of fast wheel changes, more overall weight on the frame, fork, brake parts and wheel, and increased risk of brake fade. They are a compromise.

tashi

You are simply incorrect regarding many of these statements. If this were 2015, than I'd agree, but things are changing rapidly.

I suggest that riders interested in road disc brakes read some reviews, compare weights (ex: I use light-bicycle rims when I want carbon. The disc version is lighter.) and decide for themselves.

Cyclist0108

Of those listed, loss of fast wheel changes is the only one I have found to be significant, and it can be addressed with a $0.20 shim. The rest is purely imaginary. Lots of rims are made specifically for discs.

63rickert

What on earth? Yes, brake tracks have weight. And they need to be thick enough to allow for wear. Disc rims omit the brake tracks and are lighter. They can also be made to shapes that simply cannot be built when brake tracks are required.
Tires do not operate under constant load. Front tire comes off ground on limiting uphill, carrying zero weight. Downhill the front tire carries near 100% of combined weight of bike and rider. Then the brakes are applied and the front tire carries 150% of combined weight of bike and rider. G-forces on deceleration are real. So are the constant shock forces in any ordinary riding
Fast wheel changes? Fixed with a shim? I've seen industry spokesmen fail utterly at this task. If someone trained for the job on a bike totally set up to make the job look easy can fail at this one....
On and on. No wonder they sell us fantasies.

At least someone above understands that a tire is a heavily damped spring. Yay.

Spoonrobot