fishboat

It's a certainty that something will change in the biking world and if a tire-size change can sort-of legitimately worked into that that, then that'll happen too. Selling something new (only perceived or actually real) to the same audience/market(that already have the last new "thing") is how it works...and will continue to do so. If we back up to the 70's and a sea of road and touring bikes were.."it"..along came rigid mountain bikes..and everyone bought them up, then hardtails front-suspension bikes made the rigid bikes old news and the same people snapped up the hardtails. Along comes full suspension bikes..the same folks dump the rigid's and hardtails for full squish..at around the same time aluminum comes in..everyone dumps old-fashioned steel..in comes carbon.."much more comfortable than the too stiff aluminum"..and everyone..the same folks as previously, dump aluminum for carbon...650b and 29ers roll in...and 26 inch wheels get dumped.............and the drum beats on.............

Naturally it all wasn't that simple, but boiled down..that's pretty much it. And it all has worked too well to stop now. If money can be made through a new wheel size..it'll be on the market and lots of folks will invent reasons why it's a game-changer..everything made previously is obsolete. And the masses will flock to buy it up.

AnthonyG

My two bobs worth on the whole wheel size saga is that yes, there are some performance advantages, even if minor, to using the largest wheel size that you can in a bike yet the performance advantages of "fit" are more important than the advantages of wheel size, so if you need a smaller wheel to make the geometry work then use a smaller wheel size. The smaller wheel size won't be an anchor that counteracts the advantages of better "fit".

Now you may wonder about how this actually applies and the answer is that it happens all around you with small size bikes having their geometries completely compromised and perverted to fit the standard 700c wheel size when they really should have been built with 650c size wheels which then allows for better frame angles.

I ride a custom built 650c wheel bike and as I posted previously, on downhill runs I have rolled away from riders on 700c wheel bikes so its not like the smaller wheel size was really a serious handicap.

WizardOfBoz

But it does occasionally get you a better seat in the restaurant sometimes. "This is Doctor Wizard. Table for two in a half-hour? Merci, Francois".

Regarding Rene, I think he may have a valid point but like Koyote his methods don't convince me. And at 6'2",. I don't think I'd find a 650 frame quite as comfortable as one for a 700c.

aclinjury

hmmm, graph shows that on good asphat, a 25mm wide tire should be run at 100-110 psi for maximum Crr benefit.
hear that guys using 25mm tires, not 75 psi, not 80,.. but 100!!

Miele Man

Fit and wanting a strong headtube junction is precisely why Georgina Terry designed bicycles with a 700C rear wheel and a 24" front wheel. This allowed smaller persons to have a good fitting bicycle whilst reducing toe overlap too.

Cheers

smashndash

Silca’s own tire pressure calculator suggests 88psi for a 190lb system with 26mm tires, which is the setup for the test in the link you sent.

And that’s for maximum speed. Which is not always the goal. Sometimes comfort and grip are more important. Even in a race. A few watts here and there won’t end your race but a slideout in the last corner will.

Kapusta

Is there a point here?

in response to my pointing out issues with drum roller testing, you posted a chart showing how drastically drum roller test results differ from those on pavement. Were you trying to prove my point or refute it?

On top of that, you seem to be under the impression that drum roller tests are designed to be used to make specific pressure recs. They are not. That asphalt test is also not intended to be used that way, unless you happen to be the same weight as the rider in the test.

I have addressed that blog post before. It occasionally gets cited as a validation of the drum roller test’s ability to predict real world results and comparisons between different tires. But in fact, it does not. It (that blog post) is interesting and useful for other reasons, but not that.)

(EDIT: In the above paragraph I am refering to the blog post where that graph was first shown. I see that what was linked to was a different blog post..... and equally irrelevant to whatever point you are making here.)

At best you have just demonstrated that a broken clock is correct twice a day.

burnthesheep

Uhm, where that chart matters for what you're trying to constantly peddle is at pressures above where most folks would run those tires anyway. The inversion in CRR (and divergence from the drum) happens above 100psi. For some aero wheels, you can't even run over 90 psi for warranty purposes (some HED's).

Either way, you keep trying to die on that cross but didn't listen to half of what people have said about it.

Drums do measure something meaningful enough for you to pick a smaller sample size for doing some real world testing. You can't hold the real world constant enough to test 10 different tires effectively. Three, maybe so. Two, you could certainly start playing the game of A is faster than B. Then another day, A is slower than C. Then another day, C is faster than D. I'm sticking with "C".

Honestly, for most TT's and triathlon.......the drum is probably good enough to ball park you to your three best choices. Then you're within 1/2 watt anyway.

We have a Kona Ironman guy local to us that does TT also. He has done a lot of roller, and on-road testing. He's stupid fast for the power he is putting out. I don't accredit that to luck of tire choice.

The rougher the road, I'd probably rely more on real world testing. Like gravel or cyclocross. Ride the course. Try stuff.

Anything smoother than chip seal or a street that has potholes more akin to mortar shell craters.......it's getting to be a bit disingenuous to claim you can't use the drum for anything.

Kapusta

To be fair, front and rear suspension really were game changers. At least once they get them sorted out.

But yeah, plenty of other things... not so much.

tyrion

Yes, if you can find asphalt that has yet to see automobile traffic, 100 psi would be a good choice.

Wanderer

I'm not scientific ---- all I know, is that it is easier to ride my Sirrus faster, over a given 30 mile loop, than my Crosstrail..... But, the Crosstrail is more comfortable.

Yes, the Sirrus uses 28mm tires at 125 PSI, and the Crosstrail uses 35 and 40mm tires at 92 PSI. (Lower pressure in the Crosstrail is slower, the same as the Sirrus.)

Case closed for me!

Miele Man

A few years ago on a long ride, on t he return loop, we came to a section of road that had been recently repaved. That LONG stretch of new pavement was ROUGH. We ended up reducing our tire pressures so the jarring would be reduced. Once past that section we topped up our tires again.

Cheers

aclinjury

On the contrary, newly paved asphalt becomes a bit smoother with some automobile traffic. Auto traffic squish down the surface and make all the micro holes evel smaller, and thus making the asphalt smoother.
In my riding area, Socal from Irvine down to San Diego, smooth asphalt is the norm. Asphalt is good here that I've had only 4 tubular flats within the last 2 years of using them regularly on the road.
And when sprinting almost all out at each corner in a crit, there is nothing that can compare to a tubular pumped up to sky high psi. Sprinting with a 25mm tire on 80-90 psi... feels like waddling thru sponge, you'll lose a couple positions each corner alone, do this in a course of a crit and you've burned all your matches

cannonride15

Sorry John, but according to Coppi:“Age and treachery will overcome youth and skill.”

— Fausto Coppi

tyrion

I suppose that could be the case with some roads, but Josh Poertner's testing suggests that brand new asphalt is faster when fresh and degrades after it sees traffic.

Tire Pressure - Stop Guessing And Read The Science | TRS Triathlon

dsb_mac

great info. learned a lot!

70sSanO

Well if nothing else comes from this thread, I've learned that I have overcome...
...myself.

John

ofajen

Yeah, I’ve been enjoying running low pressure for the last few years. I’ve got Ultra Sport 32s on my Schwinn and I run no more than 55 psi and on occasion found out I’d run a ride down near 40 psi. Starts to feel squishy at that point! 😊

Otto

slenten

Thanks for posting the trstriathlon link! It's much more informative than the Silca blog post.

F308

As a 65 year old rider who has progressed from 23 to 25 to 28 over the years, I might add safety as a reason for wider tires. Comfort, without a doubt, but on a lousy and/or wet road, I'm far happier with 28s.

Thomas15

Agree.

It is my goal to put a new bike, with 32s on the rims, in my stable on my 65th birthday, which is a little less than three years from now. Not only will I be more comfortable and safer, I'm really looking forward to the conversations on group rides where I get to nod my helmet clad head (with MIPS) in forceful agreement when the conversation turns towards tire size and the statement is made that only newbs and holdovers from the 1980s ride on 23s or 25s. It is with fervent prayer I hope to survive the next three years!

Good times ahead!

ofajen

It wasn’t posted as a myth, but at the start of the year, Jan did a blog post about predictions for the future. He made several, one being that road bikes will continue to move towards wider tires, with 38mm eventually becoming quite common and normal as a road tire.

https://www.renehersecycles.com/pred...for-the-2020s/

If I manage to fit 38s on my Schwinn road frame it may just about eliminate the ride time for my other bike, the 26er MTB turned gravel bike.

Otto

tomato coupe

I'd bet against that.

Kapusta

Huh? What is it I am trying to peddle? And what on Earth is your crucifixion analogy referring to?

You need to be careful when responding on behalf of another forum poster. Your explanation has little to do with aclinjury's post which I was taking to task. That chart used in aclinjury'sresponse to my post which challenged the usefulness of roller drum testing (I was quoted initially, but it has since been edited out) only demonstrated my point. Further, his point he seemed to be trying to make was about tire pressure, which had nothing to do with what I was being quoted for. Thus my question "what is the point?" was appropriate (and still unanswered).

As far the usefulness of drum roller testing.... can you show me any studies demonstrating that results from roller drum tests used to compare tires are consistent with real world results? I am not aware of any. The guy who does the roller drum testing says they are, but I've never seen evidence.

The fact that the RR figures in that chart for the drum test are significantly different from the real world measurements is - in and of itself - not necessarily a deal breaker, IMO. In practice, I don't think knowing the true RR value of a tire is the most important reason for testing. What people REALLY want is some standardized way to compare tires (like you point out). So the fact that the drum results differ from real values measured on the road is acceptable IF (and this is a crucial "if" ) that differential is consistent with all tires and types of tires.

But this critical assumption (that the differential between drum testing and real world RR is consistent from one tire to the next) has - to my knowledge - never been demonstrated to be valid.

Is there a reason to think there COULD be inconsistency in the drum/real-world differential from one tire to the next? IMO, yes. For slick tires, RR is almost all about the losses due to deformation of the casing. The problem is that a roller drum and a flat surface deform the tire casing differently. A roller drum bends the casing under the tread more sharply and in a different manner than a flat surface does. My concern about this is that it over-emphasizes the stiffness of the tread in the RR measurement.

This issue occurred to me when the Bon Jon Pass (which anyone who has ridden will tell you is fast-rolling as hell), got a lackluster RR score. When I looked up some other tires with similar RR scores, one was a Marathon touring tire which I also had a lot of personal experience with, and which felt a LOT slower than the Bon Jon. The difference was NOT subtle. Well, it turns out that the Bon Jon Pass is actually pretty thick under the tread. It gets its speed from the sidewalls. But on the roller drum, that thick tread is hard to bend.

So, I have a theoretical concern that is born out in my subjective experience. Until I see some experimental evidence to validate otherwise, I take the roller drum results with a grain of salt.

And to be clear, I don't think roller drum tests are useless, but I do think people put too much blind faith in their accuracy. My initial snarky comment about them was in response to a post suggesting that the roller drum generated database could be used to settle the questions being discussed scientifically.... it can't.

And one final point: that chart also shown that roller drum tests are not good at determining which pressure yields the lowest RR.

Germany_chris

I ride on 44 Snoqualmie Pass w/endurance casing and the only tires that are possibly faster are some Dugast tubies