Tire Pressure

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.

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.

"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.

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.

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

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.

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

--
- Frank Krygowski

Per John B.:
The question then is, "is there any definitive study that shows/proves
what tire pressure is ideal?"

I would think that the riding surface and rider weight would have to be
considered - and riding surface seems like an elusive thing to define.

Visualizing it, it seems like it takes more energy to climb over
something than to envelope it and ride across it without changing
altitude - assuming the tradeoff of energy to flex the tire vs the
energy to elevate bike/rider was favorable.

So it would seem that a very high pressure tire would roll more easily
on a super-flat/smooth surface and a squishier tire would roll more
easily on a surface where there is, say, frequent gravel or other
irregularities.
--
Pete Cresswell

On 1/2/2016 10:46 AM, (PeteCresswell) wrote:
Per John B.:
The question then is, "is there any definitive study that shows/proves
what tire pressure is ideal?"

I would think that the riding surface and rider weight would have to be
considered - and riding surface seems like an elusive thing to define.

Visualizing it, it seems like it takes more energy to climb over
something than to envelope it and ride across it without changing
altitude - assuming the tradeoff of energy to flex the tire vs the
energy to elevate bike/rider was favorable.

So it would seem that a very high pressure tire would roll more easily
on a super-flat/smooth surface and a squishier tire would roll more
easily on a surface where there is, say, frequent gravel or other
irregularities.


Right. In practice, competitors on hardwood tracks run 18mm
tubulars at 140+psi and for Paris Roubaix some of those same
riders run 27mm tubulars at 80~90psi. And they empirically
discovered those solutions 100 years ago.

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

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?"
--
cheers,

John B.

Only my own brilliance, which is unquestionable.

Bicycle people don't know jack squat about tires.... Or rather, they do
things with tires that nobody does with any other vehicle. Such as,
always inflating them to the maximum pressure, all the time. And
mounting a tire on a rim when the tire is ~5 times the width of the rim.
But anyway....

1) (From non-bicycle references) tires should be inflated proportional
to the loads they are carrying and the relative tire widths (with
respect to each other), provided that none are inflated over their
maximum pressure.

1a) What this means is if you had a bike that has 50/50 F/R weight
distribution, and 30mm wide tires on front and rear, then both tires
would be inflated to the same pressure.

1b) If your bike has 50/50 weight distribution but a 20mm wide front
tire and a 30mm wide rear tire, then the front tire should be inflated
to a higher pressure than the rear (about 33% greater pressure, since
both carry the same weight, but the front tire is one-third narrower).

1c) If your bike had 33/66 F/R weight distribution and both tires were
the same width, then the front tire should only be inflated to a
pressure about 50% of the rear (since the rear is carrying twice as much
weight as the front is).

1d) If your bike had a 33/66 F/R weight distribution and the tire widths
are 20mm/30mm F/R, then the front would be inflated to about 66% of the
the rear (the rear is carrying twice as much weight, but the front is
only 2/3 as wide).

Upright bikes don't have a great deal of weight distribution but many
long-wheelbase recumbents do (33/66 F/R isn't unusual) -- and who rides
upright bikes anymore? It is common for recumbent owners to get
front/rear tires the same widths (same tire model, so they match) and
then inflate them both to the maximum pressure, and then complain that
"the front wheel washes out in turns, these tires are no good". And that
isn't the problem at all... The problem in this instance is that the
front tire is inflated to around twice what it should be.

2) I have also seen it argued that--on a bicycle--you should still use a
slightly lower front-tire pressure than what the method given in point
(1) directs. The reason is that if you go around a turn and either of
the tires begins to slide, you can possibly recover if the rear tire
slides first--but it's very unlikely to recover if the front tire slides
much at all. Since the tire that is inflated softer (lower) will tend to
"bounce" less and maintain traction better, then your front tire should
always be a tiny bit under-inflated from its ideal pressure--say, 3-5
lbs perhaps.

2a) If the [MTB] bicycle has full suspension, then it may be possible to
tune the rebound dampening to accommodate for this matter rather then
get so picky with the tire pressures.

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.
--
Pete Cresswell

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.

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