https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

AMuzi <am@yellowjersey.org> wrote:
> https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/

Seems to give somewhat high pressures in that it’s slightly higher than my
normal go to pressure, for its lower soft range, and if anything I run my
gravel bike on the higher pressures, since I ride mixed terrain so don’t
want it to wallow.

Roger Merriman

On Tuesday, March 29, 2022 at 6:09:35 AM UTC-7, AMuzi wrote:
> https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/
> --
> Andrew Muzi
> <www.yellowjersey.org/>
> Open every day since 1 April, 1971
That showed me where I went wrong on a recent ride. I was running 60 psi in 38 mm tires on a gravel ride and by the time I got back from a 32 mile ride I couldn't walk from a painful back. Looks like 30 psi would have been more appropriate.

On Tuesday, March 29, 2022 at 11:11:29 AM UTC-7, Tom Kunich wrote:
> On Tuesday, March 29, 2022 at 6:09:35 AM UTC-7, AMuzi wrote:
> > https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/
> > --
> > Andrew Muzi
> > <www.yellowjersey.org/>
> > Open every day since 1 April, 1971
> That showed me where I went wrong on a recent ride. I was running 60 psi in 38 mm tires on a gravel ride and by the time I got back from a 32 mile ride I couldn't walk from a painful back. Looks like 30 psi would have been more appropriate.

Using the calculator it give me a reading of 40 to 48 lbs. That could be higher performance than 30 but the shock I was getting at 60 was way too much and the performance was definitely less than I would have expected.

On 3/29/2022 9:09 AM, AMuzi wrote:
> https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/

Some comments:

While the calculator does give what I consider reasonable results, I'm
not convinced it's much better than intelligent trial and error.

As stated, the calculator is only a guide, and there's no description of
what qualifies as a "smooth" vs. "rough" road. (I suspect a "rough"
California road would be equal to a "smooth" Ohio road.) It seems
obvious that the optimum pressure varies a great deal depending on road
roughness. That means, again, finding it involves trial and error.

But splicing into an adjacent thread: One disagreement I did have with
Jobst was about rolling resistance. He put great stock in rolling
resistance as measured by laboratory tests on smooth drums. I said those
were oversimplified because they ignored the "suspension losses"
involved in jiggling the bike and body, and would actually label a metal
rim or solid hard rubber tire as "best." Jobst said those suspension
losses were a separate issue, not part of rolling resistance. But they
are almost certainly much larger than the hysteresis and friction losses
that are the only things measured by a smooth rolling drum test.

So I think assigning one value of Crr to a tire is a bit simplistic.
Even the Crr vs. pressure graphs Jobst often cited are a bit simplistic.
To really understand this, we'd need a 3-D graph, with the third axis
being road roughness - if we could agree on a metric for that property.

In practice, I think nobody will ever have the budget to acquire that
data and keep it current. So we're back to hopefully intelligent trial
and error.

--
- Frank Krygowski

Frank Krygowski <frkrygow@sbcglobal.net> wrote:
> On 3/29/2022 9:09 AM, AMuzi wrote:
>> https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/
>
> Some comments:
>
> While the calculator does give what I consider reasonable results, I'm
> not convinced it's much better than intelligent trial and error.
>
> As stated, the calculator is only a guide, and there's no description of
> what qualifies as a "smooth" vs. "rough" road. (I suspect a "rough"
> California road would be equal to a "smooth" Ohio road.) It seems
> obvious that the optimum pressure varies a great deal depending on road
> roughness. That means, again, finding it involves trial and error.
>
> But splicing into an adjacent thread: One disagreement I did have with
> Jobst was about rolling resistance. He put great stock in rolling
> resistance as measured by laboratory tests on smooth drums. I said those
> were oversimplified because they ignored the "suspension losses"
> involved in jiggling the bike and body, and would actually label a metal
> rim or solid hard rubber tire as "best." Jobst said those suspension
> losses were a separate issue, not part of rolling resistance. But they
> are almost certainly much larger than the hysteresis and friction losses
> that are the only things measured by a smooth rolling drum test.
>
> So I think assigning one value of Crr to a tire is a bit simplistic.
> Even the Crr vs. pressure graphs Jobst often cited are a bit simplistic.
> To really understand this, we'd need a 3-D graph, with the third axis
> being road roughness - if we could agree on a metric for that property.
>
> In practice, I think nobody will ever have the budget to acquire that
> data and keep it current. So we're back to hopefully intelligent trial
> and error.
>
Not the only ones who use a drum to be fair,

https://www.bicyclerollingresistance.com

Who use it even with Gravel and MTB tires, realistically it’s not a good
match for such usage.

I’d assume that hill repeats at a set power (using a power meter) with
differing pressures, and or tires ideally on same day or close enough
wind/temperatures would give more useful results.

This said in my experience isn’t much difference between similar tires.
Certainly with road tires.

Gravel/MTB tires grip/puncture wear rate can in many ways be more
important.

Roger Merriman

On Wednesday, March 30, 2022 at 3:12:08 PM UTC-7, Roger Merriman wrote:
> Frank Krygowski <frkr...@sbcglobal.net> wrote:
> > On 3/29/2022 9:09 AM, AMuzi wrote:
> >> https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/
> >
> > Some comments:
> >
> > While the calculator does give what I consider reasonable results, I'm
> > not convinced it's much better than intelligent trial and error.
> >
> > As stated, the calculator is only a guide, and there's no description of
> > what qualifies as a "smooth" vs. "rough" road. (I suspect a "rough"
> > California road would be equal to a "smooth" Ohio road.) It seems
> > obvious that the optimum pressure varies a great deal depending on road
> > roughness. That means, again, finding it involves trial and error.
> >
> > But splicing into an adjacent thread: One disagreement I did have with
> > Jobst was about rolling resistance. He put great stock in rolling
> > resistance as measured by laboratory tests on smooth drums. I said those
> > were oversimplified because they ignored the "suspension losses"
> > involved in jiggling the bike and body, and would actually label a metal
> > rim or solid hard rubber tire as "best." Jobst said those suspension
> > losses were a separate issue, not part of rolling resistance. But they
> > are almost certainly much larger than the hysteresis and friction losses
> > that are the only things measured by a smooth rolling drum test.
> >
> > So I think assigning one value of Crr to a tire is a bit simplistic.
> > Even the Crr vs. pressure graphs Jobst often cited are a bit simplistic..
> > To really understand this, we'd need a 3-D graph, with the third axis
> > being road roughness - if we could agree on a metric for that property.
> >
> > In practice, I think nobody will ever have the budget to acquire that
> > data and keep it current. So we're back to hopefully intelligent trial
> > and error.
> >
> Not the only ones who use a drum to be fair,
>
> https://www.bicyclerollingresistance.com
>
> Who use it even with Gravel and MTB tires, realistically it’s not a good
> match for such usage.
>
> I’d assume that hill repeats at a set power (using a power meter) with
> differing pressures, and or tires ideally on same day or close enough
> wind/temperatures would give more useful results.
>
> This said in my experience isn’t much difference between similar tires.
> Certainly with road tires.
>
> Gravel/MTB tires grip/puncture wear rate can in many ways be more
> important.

One of the problems with rolling resistance tests like these is that they never test the effects of the sidewall stiffness properly. I took the C50 out yesterday and with a headwind and a crosswind most of the way I had a higher than usual average speed than using the Michelin tires. Even though the Vittoria Corsa graphene is claimed to have the lowest rolling resistance, I have never found that to be true except maybe on new tires for a very short time.

On Friday, April 1, 2022 at 8:40:57 AM UTC-7, Tom Kunich wrote:
> On Wednesday, March 30, 2022 at 3:12:08 PM UTC-7, Roger Merriman wrote:
> > Frank Krygowski <frkr...@sbcglobal.net> wrote:
> > > On 3/29/2022 9:09 AM, AMuzi wrote:
> > >> https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/
> > >
> > > Some comments:
> > >
> > > While the calculator does give what I consider reasonable results, I'm
> > > not convinced it's much better than intelligent trial and error.
> > >
> > > As stated, the calculator is only a guide, and there's no description of
> > > what qualifies as a "smooth" vs. "rough" road. (I suspect a "rough"
> > > California road would be equal to a "smooth" Ohio road.) It seems
> > > obvious that the optimum pressure varies a great deal depending on road
> > > roughness. That means, again, finding it involves trial and error.
> > >
> > > But splicing into an adjacent thread: One disagreement I did have with
> > > Jobst was about rolling resistance. He put great stock in rolling
> > > resistance as measured by laboratory tests on smooth drums. I said those
> > > were oversimplified because they ignored the "suspension losses"
> > > involved in jiggling the bike and body, and would actually label a metal
> > > rim or solid hard rubber tire as "best." Jobst said those suspension
> > > losses were a separate issue, not part of rolling resistance. But they
> > > are almost certainly much larger than the hysteresis and friction losses
> > > that are the only things measured by a smooth rolling drum test.
> > >
> > > So I think assigning one value of Crr to a tire is a bit simplistic.
> > > Even the Crr vs. pressure graphs Jobst often cited are a bit simplistic.
> > > To really understand this, we'd need a 3-D graph, with the third axis
> > > being road roughness - if we could agree on a metric for that property.
> > >
> > > In practice, I think nobody will ever have the budget to acquire that
> > > data and keep it current. So we're back to hopefully intelligent trial
> > > and error.
> > >
> > Not the only ones who use a drum to be fair,
> >
> > https://www.bicyclerollingresistance.com
> >
> > Who use it even with Gravel and MTB tires, realistically it’s not a good
> > match for such usage.
> >
> > I’d assume that hill repeats at a set power (using a power meter) with
> > differing pressures, and or tires ideally on same day or close enough
> > wind/temperatures would give more useful results.
> >
> > This said in my experience isn’t much difference between similar tires.
> > Certainly with road tires.
> >
> > Gravel/MTB tires grip/puncture wear rate can in many ways be more
> > important.
> One of the problems with rolling resistance tests like these is that they never test the effects of the sidewall stiffness properly. I took the C50 out yesterday and with a headwind and a crosswind most of the way I had a higher than usual average speed than using the Michelin tires. Even though the Vittoria Corsa graphene is claimed to have the lowest rolling resistance, I have never found that to be true except maybe on new tires for a very short time.
change that to WHILE using the Michelin tires.

On Friday, April 1, 2022 at 10:40:57 AM UTC-5, cycl...@gmail.com wrote:
> On Wednesday, March 30, 2022 at 3:12:08 PM UTC-7, Roger Merriman wrote:
> > Frank Krygowski <frkr...@sbcglobal.net> wrote:
> > > On 3/29/2022 9:09 AM, AMuzi wrote:
> > >> https://www.renehersecycles.com/the-science-behind-the-tire-pressure-calculator/
> > >
> > > Some comments:
> > >
> > > While the calculator does give what I consider reasonable results, I'm
> > > not convinced it's much better than intelligent trial and error.
> > >
> > > As stated, the calculator is only a guide, and there's no description of
> > > what qualifies as a "smooth" vs. "rough" road. (I suspect a "rough"
> > > California road would be equal to a "smooth" Ohio road.) It seems
> > > obvious that the optimum pressure varies a great deal depending on road
> > > roughness. That means, again, finding it involves trial and error.
> > >
> > > But splicing into an adjacent thread: One disagreement I did have with
> > > Jobst was about rolling resistance. He put great stock in rolling
> > > resistance as measured by laboratory tests on smooth drums. I said those
> > > were oversimplified because they ignored the "suspension losses"
> > > involved in jiggling the bike and body, and would actually label a metal
> > > rim or solid hard rubber tire as "best." Jobst said those suspension
> > > losses were a separate issue, not part of rolling resistance. But they
> > > are almost certainly much larger than the hysteresis and friction losses
> > > that are the only things measured by a smooth rolling drum test.
> > >
> > > So I think assigning one value of Crr to a tire is a bit simplistic.
> > > Even the Crr vs. pressure graphs Jobst often cited are a bit simplistic.
> > > To really understand this, we'd need a 3-D graph, with the third axis
> > > being road roughness - if we could agree on a metric for that property.
> > >
> > > In practice, I think nobody will ever have the budget to acquire that
> > > data and keep it current. So we're back to hopefully intelligent trial
> > > and error.
> > >
> > Not the only ones who use a drum to be fair,
> >
> > https://www.bicyclerollingresistance.com
> >
> > Who use it even with Gravel and MTB tires, realistically it’s not a good
> > match for such usage.
> >
> > I’d assume that hill repeats at a set power (using a power meter) with
> > differing pressures, and or tires ideally on same day or close enough
> > wind/temperatures would give more useful results.
> >
> > This said in my experience isn’t much difference between similar tires.
> > Certainly with road tires.
> >
> > Gravel/MTB tires grip/puncture wear rate can in many ways be more
> > important.
> One of the problems with rolling resistance tests like these is that they never test the effects of the sidewall stiffness properly. I took the C50 out yesterday and with a headwind and a crosswind most of the way I had a higher than usual average speed than using the Michelin tires. Even though the Vittoria Corsa graphene is claimed to have the lowest rolling resistance, I have never found that to be true except maybe on new tires for a very short time.

???????????
Tommy, I am assuming you started and finished your ride at the same location. How do you have "a headwind and a crosswind most of the way"? On most round trip rides, you have equal headwind and tailwind. Despite the very common perception that the headwinds were twice as strong and twice as long as the tailwinds. That is simply the imagination playing tricks with you. And with crosswinds, unless the wind is at a true 90 degrees perpendicular, there will be a little head or tail affect. Or did the wind change on you throughout the ride? GOD himself was looking down upon you Tommy, and God sayeth "Make thee suffer!" "Keep the winds bloweth against thee!"