Tire Pressure

On Saturday, January 2, 2016 at 1:26:28 PM UTC, AMuzi wrote:
On 1/1/2016 10:04 PM, John B. wrote:

The question then is, "is there any definitive study that shows/proves
what tire pressure is ideal?"

There isn't because besides rider weight and tire casing
characteristics, road surface varies significantly.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

It has been known for years that the correct inflation in almost all cases in which a tire has been competently designed, especially as to sidewall stiffness, is a pressure that with a particular rider and his luggage aboard wil cause a drop of 15% of the tyre height. See the table at http://www.bikequarterly.com/images/TireDrop.pdf and elsewhere Jan Heine and Frank Berto reported on their tests.

Andre Jute
QED

ah tire drop super !

TD quantizes for the MOTS, relationship tween pressure/road surface/grip....grip is a combinative of style attitude ability strength ...

thee contact surface grip on road surface is for twisty...endure...straight on smooth surface...

a softer tread attack for twisty beats a hard pressure contact meant for straight ahead....as the softer lower pressure and higher TD fits down into the road surface for grip.

while this is obvious, most would not think or bother fiddling with pressures for each ride. Do you tune your violin ?

off course not yura moron

actually just not as compulsive as the tuner.

the time spent fiddling is a PITA.

I doahn no as I never group up.

On Sat, 2 Jan 2016 11:19:26 -0000, "Graham"
wrote:


"John B." wrote in message ...

I've been fooling around with tire pressure on the new (Old) bike.
Like (probably) most people I've always pumped bike tires up to
somewhere close to the maker's maximum recommended pressure, but in
Bangkok many of the roads I ride over aren't exactly smooth and 100+
psi tires are hard :-)

With the uneven roads in mind I've been running a bit lower tire
pressure and have done some research, on the Web, concerning optimum
tire pressure and it seems that simply pumping tires up to the maximum
recommended pressure may not be the way to go and that tire pressure
above a certain level (depending on tire make and size) actually are
not as efficient then they would be at lower pressures. One site has
an article by Frank Berto, from the Bicycle Quarterly (I believe),
showing that with a 165 lb. total weight (bike and rider) and 23mm
tires the optimum tire pressure is in the 85 - 85 psi range.
Another site http://clublongo.com/psi/
has an on line calculator that shows that a 140 lb. rider with a 22
lb. bike should use 75 psi(F) and 94 psi (R) with 23 mm tires and
62/79 psi with 25 mm tires.

I even came across a site with a chart that demonstrates that
increasing pressure above a certain level actually increases the power
required to ride at a certain speed.

I also came across a site that (very authoritatively) states that
with 23mm tires the proper pressure is 110 psi front and 120 psi rear.

The question then is, "is there any definitive study that shows/proves
what tire pressure is ideal?"
--
cheers,

John B.


I think you will find that there is no "ideal" single pressure but there are optimum pressures for different tyre, rider, road condition and use combinations. I usually start with the Vittoria calculator and fine tune from the

http://www.vittoria.com/itire/

You will notice quite a variation depending on your input to the calculator and how wide the weight range is. The only variablle that appears to be missing in the road version is tyre size whereas there is quite a range of sizes in the mtb version. Here I can only assume that Vittoria believe road tyre size has only a limited effect compared to the other variables.

Graham.

Yes. I used a graph that was posted in Bicycle Quarterly that requires
one to weigh the bike and rider, weight on front and rear wheel, and
then select the pressure for that wheel weight by the tire size. It
seems intended to provide a "middle of the road" pressure.

I've also got a hand phone utility that apparently assumes a fixed
percent of weight on the front and rear wheel based on the total bike
and rider weight and calculates a pressure based, then, based on tire
size.

They both suggest a pressure substantially lower then the old rule of
thumb - 100 on the front and 110 on the back :-)
--
cheers,

John B.

On Sat, 2 Jan 2016 09:42:29 +0000, Nick wrote:

On 02/01/2016 04:04, John B. wrote:

I also came across a site that (very authoritatively) states that
with 23mm tires the proper pressure is 110 psi front and 120 psi rear.

The question then is, "is there any definitive study that shows/proves
what tire pressure is ideal?"

I did a study which shows that if I pump my tyres up to 120 psi a couple
of weeks later they are at 80 psi.

Being lazy this seems to provide me with the optimal range.

I also figure I'm risking pinch flats if I go much below 80.


A couple of weeks? You must be using those thick, heavy, ugly, inner
tubes. Switch to the ultra thin and lightweight "racing" tubes and
you will be down to 80 PSI in a day or so :-)
--
cheers,

John B.

On Sat, 02 Jan 2016 07:26:14 -0600, AMuzi wrote:

On 1/1/2016 10:04 PM, John B. wrote:

I've been fooling around with tire pressure on the new (Old) bike.
Like (probably) most people I've always pumped bike tires up to
somewhere close to the maker's maximum recommended pressure, but in
Bangkok many of the roads I ride over aren't exactly smooth and 100+
psi tires are hard :-)

With the uneven roads in mind I've been running a bit lower tire
pressure and have done some research, on the Web, concerning optimum
tire pressure and it seems that simply pumping tires up to the maximum
recommended pressure may not be the way to go and that tire pressure
above a certain level (depending on tire make and size) actually are
not as efficient then they would be at lower pressures. One site has
an article by Frank Berto, from the Bicycle Quarterly (I believe),
showing that with a 165 lb. total weight (bike and rider) and 23mm
tires the optimum tire pressure is in the 85 - 85 psi range.
Another site http://clublongo.com/psi/
has an on line calculator that shows that a 140 lb. rider with a 22
lb. bike should use 75 psi(F) and 94 psi (R) with 23 mm tires and
62/79 psi with 25 mm tires.

I even came across a site with a chart that demonstrates that
increasing pressure above a certain level actually increases the power
required to ride at a certain speed.

I also came across a site that (very authoritatively) states that
with 23mm tires the proper pressure is 110 psi front and 120 psi rear.

The question then is, "is there any definitive study that shows/proves
what tire pressure is ideal?"
--
cheers,

John B.


There isn't because besides rider weight and tire casing
characteristics, road surface varies significantly.

Well, there is. I've got a hand phone utility (from Vittoria)
http://www.vittoria.com/itire/
that takes into consideration the material and thread count, whether
clincher or tubular, weight of bike and rider and road condition -
smooth, bumpy, mixed.
--
cheers,

John B.

On Sat, 2 Jan 2016 10:02:20 -0500, Frank Krygowski
wrote:

On 1/2/2016 8:26 AM, AMuzi wrote:
On 1/1/2016 10:04 PM, John B. wrote:

I've been fooling around with tire pressure on the new (Old) bike.
Like (probably) most people I've always pumped bike tires up to
somewhere close to the maker's maximum recommended pressure, but in
Bangkok many of the roads I ride over aren't exactly smooth and 100+
psi tires are hard :-)

With the uneven roads in mind I've been running a bit lower tire
pressure and have done some research, on the Web, concerning optimum
tire pressure and it seems that simply pumping tires up to the maximum
recommended pressure may not be the way to go and that tire pressure
above a certain level (depending on tire make and size) actually are
not as efficient then they would be at lower pressures. One site has
an article by Frank Berto, from the Bicycle Quarterly (I believe),
showing that with a 165 lb. total weight (bike and rider) and 23mm
tires the optimum tire pressure is in the 85 - 85 psi range.
Another site http://clublongo.com/psi/
has an on line calculator that shows that a 140 lb. rider with a 22
lb. bike should use 75 psi(F) and 94 psi (R) with 23 mm tires and
62/79 psi with 25 mm tires.

I even came across a site with a chart that demonstrates that
increasing pressure above a certain level actually increases the power
required to ride at a certain speed.

I also came across a site that (very authoritatively) states that
with 23mm tires the proper pressure is 110 psi front and 120 psi rear.

The question then is, "is there any definitive study that shows/proves
what tire pressure is ideal?"
--
cheers,

John B.


There isn't because besides rider weight and tire casing
characteristics, road surface varies significantly.

Exactly. Seems to me that if you were riding on some super-smooth
surface like flooring tiles in a building's hallway, the optimum
pressure would be the highest the tire could stand. At the other
extreme, I remember one mountain bike ride that ended with several
hundred yards of railroad ballast. That was rocks probably 4" to 6"
diameter. I dropped my tire pressure down to maybe 20 psi and it felt
much, much better. Typical roads will be somewhere in between, and I
suppose trial and error is the only way to judge.

Well of course one tire pressure cannot accommodate any and all
surface conditions, but one can certainly find a meaningfully "base
pressure".

Incidentally, I came across sites that state that measuring power
input, or roll down, showed that tire pressure above a certain figure,
depending on the tire of course, actually increased the effective
rolling resistance.
https://janheine.wordpress.com/2015/...a-and-details/

I suspect that most avid riders tend to use too much air pressure.
Especially in the front tire, which carries far less load.

I've measured "wheel" weight on several of my bikes, all with ~ 1
meter wheelbase, and they pretty much have a 55/45 (back/front)
ratio.
--
cheers,

John B.

On 1/3/2016 2:17 AM, John B. wrote:
On Sat, 2 Jan 2016 10:02:20 -0500, Frank Krygowski wrote:


I suspect that most avid riders tend to use too much air pressure.
Especially in the front tire, which carries far less load.

I've measured "wheel" weight on several of my bikes, all with ~ 1
meter wheelbase, and they pretty much have a 55/45 (back/front)
ratio.

I just double checked two of my bikes. Both gave 57% / 43%, so that's
1/3 more on the rear than the front. I had thought the difference was
even greater.

--
- Frank Krygowski

On 02/01/16 21:35, AMuzi wrote:
On 1/2/2016 2:51 PM, (PeteCresswell) wrote:
Per AMuzi:
and for Paris Roubaix some of those same
riders run 27mm tubulars at 80~90psi. And they empirically
discovered those solutions 100 years ago.

Wow.... 28mm's are my *skinny* tires.... and I usually avoid them
because they beat me up too much even on fairly well-paved surfaces.


And how did you do against Eddy on the cobblestones?

http://25.media.tumblr.com/tumblr_m1...v9zo1_1280.jpg

I was peaking of competition. Commuting or casual sport riding may have
different parameters of course.


I did commute on 28mm's for a while. Rougher than a badgers arse.

back to front sifts front under braking

higher pressures ...rubber doesn't climb over the mega number of crack edges as the wheel rotates and moves forward...lika slinky..

but worser...BOUNCES BACKWARDS.

now letus consider CLING...

Cling is a function of Sloth...

On Sun, 3 Jan 2016 12:58:26 -0500, Frank Krygowski
wrote:

On 1/3/2016 2:17 AM, John B. wrote:
On Sat, 2 Jan 2016 10:02:20 -0500, Frank Krygowski wrote:


I suspect that most avid riders tend to use too much air pressure.
Especially in the front tire, which carries far less load.

I've measured "wheel" weight on several of my bikes, all with ~ 1
meter wheelbase, and they pretty much have a 55/45 (back/front)
ratio.

I just double checked two of my bikes. Both gave 57% / 43%, so that's
1/3 more on the rear than the front. I had thought the difference was
even greater.

It probably depends on how large your butt is :-)
--
cheers,

John B.