I thought we were engaging in some good natured banter but it seems I was the only one in on the joke.

Here's the long answer to what's been posted thus far.

The 'voodoo' reference is a pretty common parlance when people on BF begin discussing things like tire pressure or chain lube. The conversations go 'round and 'round and no-one has proof but everyone has an opinion. Eventually it all boils down to what you believe - voodoo.

As to the article itself and it's source anything technical published in Bicycling magazine is dumbed down to the point of being next to useless information. They are notorious for this just as Vogue is notorious for giving out some of the worst health advice imaginable.

To the point; The article talks about varying tire pressure based on the different loads each wheel is subjected to. When? Under what conditions? When sitting static on a trainer? It's certainly not under real world conditions.

In reality your weight is constantly moving around the bike: When climbing seated, when climbing standing, when accelerating out of the saddle, when cornering, when braking, when braking on a descent, when sprinting. The entire concept of a static 60/40 load is based on a false premise.

Tire sag? I've only ever heard of this when discussing the tire pressure in your car tires. I will state categorically that car tires and bicycle tires do NOT perform the same way and are NOT designed or constructed the same way. It's apples and erasers.

Again, when is tire sag measured? Under static conditions? Just as load changes under real world conditions 'tire sag' would, too.

Please bare in mind I worked for - WORKED FOR - one of the tire companies mentioned in the article. No one from any of these companies is quoted or even paraphrased in any way. He just says he talked to them. He could have talked to them about the weather and this would be true.

From what I know, tires are designed to function at their best within a certain range of pressure. The manufacturers consider rolling resistance, puncture protecting, comfort and wear as the primary factors. They then design the construction, choose materials and compounds to best meet those objectives within a certain price-point. It's a long and carefully considered process so when the various engineers involved say outright that certain tires perform best (the nexus of all 4 criteria) within a certain pressure range under almost all conditions I tend to believe them.

That would be my tire voodoo.

Now, there is variation from model to model and manufacturer to manufacturer but if we focus on the 622x13 size you've specifically mentioned then almost all brands in the marketplace, in a similar price range, have suggested inflation pressures that are pretty close to identical. Some even list the MIN inflation pressure right on the sidewall of their tires. I wonder why?

I would say to you that the body of evidence as suggested and published by the people making the products under discussion runs counter to the article posted and due to this the article requires additional scrutiny. When examined in detail the article is based on a false premise and introduces a meaningless metric but provides no other evidence in any form to back up its assertions.

That's pretty much my take on the subject at hand. Other than anecdotal evidence is there any other published data that supports this article?

I always go up to the max or near it. I have even inflated some tubular Tufo's to 175. I am lighter than the OP. Have done it since I got a road bike in the early 90's and I've lived and rode many states and some countries since and has always worked for me. I also do not wear gloves 80% of the time in the summer so that shows you that it doesn't feel jittery to me. I have 2 road bikes and a fixie/track. GP4000 120 or close to it, Pro race 3 Michelin's 115 and GP4000 tubulars 145.

We haven't even touched on the clincher vs tubular aspect of the conversation.

BTW Tufos need higher pressure to reach their sweet spot due to the stiffer casing construction. It seems like you've figured that out.

I think we've pretty much flogged this subject to death. I'm fine, not offended, it's just BSing about air pressure in bike tires, after all. But just for accuracy's sake, I'd like to point out the article is in Bicycle Quarterly, not Bicycling Magazine. Frank Berto was the person who did the research that generated the graph, and was at one time the engineering editor at Bicycling Magazine. He is also author of several books on cycling. Interestingly, he says on his website;
"I ceased writing for "Bicycling" in 1991, when they de-emphasized technical articles"

My error. I did read the article in the link posted but for some reason I thought it was a reprint from an article in Bicycling.

Interesting quote from the author. He was ahead of the curve on that one.

No, (I suspect) most people here pump to the maximum rated pressure listed on the particular tires they have. That is, they aren't doing to "avoid pinched tires".

Current tires typically have a maximum rated pressure of at-least 120 psi.

You guys are thinking too hard on this.

The tire inflation range is stamped on the tire. Something like 110-125psi. That is what the tire is engineered or designed for. The lower number will be more comfortable (and for most people just as fast); the higher number minimally less resistance. Experiment and find what you like, but stay in the range printed on your sidewall unless you have a really good reason to go outside the design parameters.

And yes, most people would likely be better off on the lower end of the spectrum.

Meh. Many tires only state a max pressure, including the tires on both of my bikes.

QUOTE=Bob Dopolina;13061044]That's pretty much my take on the subject at hand. Other than anecdotal evidence is there any other published data that supports this article?[/QUOTE]

Bicycle Quarterly did a great test of rolling resistance in tires on pavement and in repeated tests (about 150 runs) were able to see clear differences. As many here have already observed increasing pressure would lower resistence only up until a point, then it increased slightly, tire size (width) and pressure mattered less than quality of tire construction, older thinner tires rolled better than new ones, and tubulars rolled better than everything.

Most interesting of all was that the testers on the bikes did not know what tires and pressures they were running but were asked if the tire felt 'fast' or 'slow'. Their subjective feelings did not correspond at all to whether the tires were actually more resistant or less resistent.

The Performance of Tires. BQ Vol. 5, No. 1, p. 1.

One of the reasons Bicycle Quarterly published Frank Berto's chart was that the editor found it corresponded closely to his own test results.

For anyone not around in the 1980's Bicycling used to be a pretty decent magazine. Frank Berto's brutally honest tests of derailleurs probably gave the advertising manager a new heart attack with each issue.

I have three sets of tires in regular rotation (no pun intended):

Conti Contact Extra Light - 700x42c (measures 37mm on 23mm rims)
Vittoria Randonneur Hyper - 700x35c
Vittoria Randonneur Hyper - 700x32c

For paved roads, I run anywhere from 50f/60r to 60f/70r. For un-paved riding, I'll drop down as low as 35f/45r (but usually 40/50). In 3K miles, I've only pinch-flatted once (large pothole that I didn't see), and punctured once. That 3K includes a good number of after-dark winter commuting miles.

Clearly I'm some sort of mutant.

Uh...dude...we're talking about 622x13 (or 700c to you).

Of course your 622x32, 622x35 and 622x42 tires will run at much lower pressures.

Roll of eyes.

I think I remenber those tests. They were done by guys rolling down a hill and they measured time. Is this this same article?

If so, there are some serious problems with it.

First off, they were measuring speed over a fixed distance outside with bikes and riders. The drag on the riders bodies is significant enough (as in the largest componant) to really mess up the data. There's no way you can get a rider to hold exactly the same postion 50 or 60 times repeatedly (IIRC they used more than 1 rider which is also a problem). You also have changing wind conditions over the course of the test period that would also skew the data.

The only way to measure pressure and rolling resistance is in watts in a controlled enviroment such as the tests done in Korbach that serve as the basis for the often cited article from...(I hate posting before I finish my morning coffee - the brain is still running on friction)...the French guys...someone help me out with the link here...

If it is the article I recal it was the best attempt at that time to come up with hard data, so kudos for that, but they obviously didn't have the resources to do a study that was repeatable and verifiable.

Another point is that tire construction and compounding have gone through several generations and so the data supplied by both tests is now pretty much meaningless.

I do agree that the subjective part regarding the riders impression of which tires/pressure was faster is pure gold.

I don't know anyone named, "dude."

And who rides a 622x13 tire?

Really, I know quite a few guys named dude.

Typo on the '13'. It should be 622x23c. That is a standard road bike tire and what is being discussed in this thread.

This:
"So we recommend you buy the best tyres you can afford and pump them up hard. Even on our test bikes we will fit cheap tyres that say 110 psi max pressure. We always pump them up to 150 psi minimum without problems."

You can vary it a little, but well over 100 lbs on 23's isn't too much - it is pretty much standard. I ride 28's these days, as I prefer them. But I go to 110 as a matter of course.

As for a pump, haunt yard sales, freecycle, the campus bulletin boards and so on. I use a 2 gallon Black and Decker compressor rated at 125 psi



I paid $20 for it, used.

Dont give up so darned easy.

I went back and reread the test and I do not see any serious problems with it. They used one rider wearing the same tight fitting clothing, tested at the same time each morning with the same barometric pressure, and on the one day that a light wind came up they curtailed testing. Most importantly, throughout the test they made reference runs using the same tire and the times were consistent. If changing aerodynamics were skewing the results the times would have been spread out.

Bicycle Quarterly has used power meters to measure tire rolling resistance in an interesting test. On a smooth road the rider maintained 16 mph. At a certain point he moved to the right and rode on the rumble strip while maintaining 16 mph. The test was repeated with wider tires at a lower pressure. Data from the power meter was downloaded afterward. As you might imagine, riding on the rumble strip required more power. For wider/lower psi tires it required a little more power, for narrower/higher psi tires it required nearly TWICE as much power. On smooth pavement there was little power difference between the two tires.

The take away from that test was that if you only ever cycle on smooth roads, go with high pressure tires, they have a slight advantage. If your rides sometimes take you onto rough roads, go with lower pressure tires for their large performance advantage on rough pavement because the penalty for lower pressure tires on smooth roads is slight. A good example of a smooth road/rough road race course is Paris Roubaix that Fabian Cancellara won on 28mm tubulars.

I'm working from memory regarding these tests and yes, these are the ones I remember.

Here's the problem I have with these tests:

1. ANY variation in rider position will have SOME affect on the data. There is no way to control this. The rider needs to be removed entirely otherwise the margin of error is just too high.

2. The technology tested in these tests is generations behind what is being produced now. It's like reading a hot rod mag from the 60's and trying to use the info to tune your car.

Casing constructions and materials have changed. Breaker materials have evolved. Compounding has changed and improved vastly and become much more sophisticated.

In short the data provided in those tests is no longer valid because the tires tested no longer exist.

Remember when the difference between tubulars and clinchers was night and day. Not so much any more. The test data on clinchers is very near to what contemporary tubular test at. In fact, some clincher test better than some tubulars.

As a side note I think it would be really interesting to find some NOS of the old tires and test them head to head with current model products. That would be some interesting data.

Maybe this will help - info from those french guys. The germans (Conti) have similar pressure ranges defined for their tires. Most (obviously not all) put this on their sidewall.

https://www.michelinbicycletire.com/m...rpressure.view

I would go with what the manufacturer (engineers) designed the tire for rather than just about anything posted on the internet (unless you have reason to put your trust into the source). With of course the realization that most people can run lower tire pressure than they think without loosing too much in efficiency.

For that matter, bigger tires (all other things being equal) have less rolling resistance than small tires. When not racing (i.e. riding under 25mph) I use as big a tire as I can (typically 28mm). When racing (i.e. riding over 25mph) the aero benefits of smaller tires outweigh the increased rolling resistnace of a 23mm tire.

Conti's suggestions are pretty straight forward:

Most importantly - Tyre pressure. Inflate your tyres to the recommended pressure in this guide. Carrying a heavy load? If so, then increase the pressure up to and including the maximum shown in this guide.

An example:
Tire - size - recommended -Maximum pressure
Gatorskin - 700x23 - 110 - 120
Gatorskin - 700x25- 95 - 120

Sound Familiar?

I'll stick with Berto's chart and my own personal experiences until the tire manufacturers actually publish something more substantial on the subject. Interesting that the link you give contains these quotes:
" the most important variable that affects what the proper pressure should be is the load your tires are asked to carry"
" Michelin engineers have found that there's a certain amount of deflection in the tire profile that's optimal for balancing grip, efficiency, comfort and durability"

Deflection is NOT tire sag. Tire deflection is a commonly used industry word that describes how are tire casing reacts to an obstacle. It is the principal componant in rolling resitance.

Read a little bit about the Black Chilli compound. It describes how the smaller molecules used in Black Chiki lower rolling resistance by altering casing deflection. You might find it interesting.

The design criteria are the same ones I listed earlier. Tires are designed to have the best combination of all four for the price point and intended use of the particular tire.

I notice the OP never mentioned tire size and only a few in this thread are confining the discussion to 23s. All of the testing new & old, lab & in-the-field, show tires larger than 23 have lower rolling resistance, yet many will not let go of skinny tires despite the body of evidence pointing to wider tire advantages. Just an example of focusing on a singular aspect of test results, without considering variables (like TT context)

All testing new and old state there are trade-offs with increased tire pressure, all agree tire construction has a role in optimum pressure ranges, and all say high tire pressures decrease rolling resistance up to a point of diminishing returns. Despite the harping on the fallibility of the old tests, new testing does nothing to debunk any take away messages from the old testing. A couple more tech/semi-tech links for those interested. https://www.bikeradar.com/news/articl...he-myths-29245 , https://rouesartisanales.over-blog.co...e-1503651.html My poke at lab testing; road surfaces on which I ride look nothing like those drums.

I think the important message in the entire discussion is variability, "it depends".

That is true. My 23mm clincher clincher wheel/tire combo is rated at 145psi. I don't ride like that on the street (maybe at the velodrome). At 110 psi, there is still a fair amount of deflection.

It does depend on the road surface. If your tires are skipping alot over the surface, they are likely too stiff. I've seen this some on a road course. But if your route is reasonably smooth - there are not that many bumps to slow you down (it does rather depend on where you choose to ride though).

That's a reprint of the original article from a few years ago and I'm suggesting that tires have changed in response to such articles over the years meaning that new data is required.

I am probably guilty here. We were discussing road tires (...'cause this is the road forum...) and since the vast majority of road tires currently on the market are 23c I wanted to stay focused on this segment of the market (with 25c thrown in) to avoid getting into MTB tires, 29ers, hybrid tires, XCross tires...

I think if you read the article, and consider the point I have been making about tire design and performance not being solely linked to rolling resistance but being a combination of factors then a 23c tire is faster than a 25c (especially in TT conditions) because the weight and aero advantage out weigh the slight increase in rolling resistance.

I mentioned how changes in tire design and construction have rendered all previous data obsolete, here is a concrete example:

The article correctly states that using a breaker strip decreases tire deflection and thereby increases rolling resistance (with the benefit of increased puncture protection). They mention Nylon and what appears to be a reference to Kevlar specifically. They suggest that the rigid (somewhat) nature of the breaker strip is the cause of the decreased tire deflection. It stands to reason that with a slightly larger tire casing (25c) that the breaker strip (which is the same size for both 23c and 25c tires) is less, as a percentage of casing size, in a 25c tire than in a 23c tire thereby decreasing it's affect of deflection.

Furthrmore, The smaller dia of the 23c tire creates a situation where the breaker is in a higher state of tension magnifying it's detremental effect of deflection if only by the slightest degree.

The logical conclusion is that the detrimental effects of the breaker strip with regards to rolling resistence are even greater in a smaller dia tire.

Since, as I mentioned several times by now, tires are designed to achieve the best combination of four criteria for a given pricepoint and a given application, racing tires use Kevlar as opposed to Nylon because of superior puncture resistence even though Nylon out performs Kevlar when it comes to rolling resistence because its suppleness has a less detrimental effect of rolling resistence.

Now, here's where all of the data supporting those 'facts' gets thrown out the window: Vectran.

Vectran has become the new breaker material of choice because it is lighter, far more supple and requires a much lighter and thinner breaker strip to provide not only comparible puncture resistence, but increased puncture resistence.

So what does this mean? It means that the differences in the detrimental effects of a breaker strip between a 23c tire and a 25c tire have become less than what is perceivable by human detection.

Now lets talk about compounding.

Up until a few years ago the molecular structure of compounds used by various tire manufacturers were similar in size. Similar enough that the effects of deflection were pretty much equal.

Along came Black Chili.

With it's significantly smaller molecular structure the compound had a greater ability to fold and bend around irregular surfaces (anything we ride on). This means that less energy is lost in deflection and rolling resistence is thereby decreased.

If you don't believe me look at what happened with the first generations of dual compound tires. Why did they delaminate?

Two reasons:

1. Bonding different compounds is harder than it seems.

2. The fact that dissimilar compounds, with dissimlar molecular structures deflect, well...differently, meant that eventually the bonding would break down at the molecular level and the tire would fall apart. I was a victim of this fact when a Vittoria tire delaminated on me right after a sprint. Down I went for no apparrent reason at all.

So, again, we are back to a point where the smaller molecules used in contemporary compounding means that the effect these compounds have on tire deflection has been decrease narrowing the gap between 23c and 25c to a point less than that of human detection.

Where most of us seem to agree is that increased pressure is not always faster because, at some point that its partially dependant on materials and construction and thereby varies from tire to tire, tire deflection increases at higher pressures thereby increasing rolling resistence.

Regarding the testing in the lab on steel drums I understand how some might wonder about the validity of tests conducted under those conditions vs tests on the road but I believe that it is most important to remove all other possible factors (like a rider, wind, humidity, barometric pressure, gravel, slime, squirrel bits etc) from the testing so that the factors being tested can be isolated and measured.

The problem I have with the older, roll down the hill and lets see which tire is faster tests is that these things can't be controlled with the very narrow range of the data being collected.

Skip to the bottom part.

Due to changes in construction, materials and compounds being used in the latest generation of tires new testing is required to compare the performance of various tires, tire sizes and optimal pressure for a given condition.

I would run a drop between the rear and front, but what concerns me isn't then "normal" in-the-drops position, but when I some out of the saddle on a climb. On some hills, and on a hard sprint I feel like 70% of my weight is probably over the front wheel. I would be afraid of flats in those situation. My front tire looks smashed enough at 100 PSI, I may air it up to 110 on the next ride and see how it feels.

What say you on these situations?