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Main
Date: 27 Oct 2007 23:35:32
From: Jim Flom
Subject: 160 psi
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Am I really faster, or do I just feel faster?
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Date: 29 Oct 2007 16:00:29
From: Marian
Subject: Re: 160 psi
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On Oct 29, 1:09 pm, Ryan Cousineau <rcous...@sfu.ca > wrote:
> ObTech: A few weeks ago I mentioned the discovery of fine, dry dirt
> inside of my tire casing after a race. After this race, I discovered the
> same phenomenon, only (urgh) inside my bike shorts.
I went riding through some absolutely fabulous mud puddles at a
mountain bike race two weeks ago. Come the inevitable time to crash
and I got road rash on the inside of my thigh. There was no question
of riding at all for most of the next week.
-M
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Date: 30 Oct 2007 09:33:35
From: Mike
Subject: Re: 160 psi
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In article <1193673629.397224.248760@i13g2000prf.googlegroups.com >, marian.rosenberg@gmail.com says...
> On Oct 29, 1:09 pm, Ryan Cousineau <rcous...@sfu.ca> wrote:
>
> > ObTech: A few weeks ago I mentioned the discovery of fine, dry dirt
> > inside of my tire casing after a race. After this race, I discovered the
> > same phenomenon, only (urgh) inside my bike shorts.
>
> I went riding through some absolutely fabulous mud puddles at a
> mountain bike race two weeks ago. Come the inevitable time to crash
> and I got road rash on the inside of my thigh. There was no question
> of riding at all for most of the next week.
>
I have had road-rash on my back, stomach, shoulders, arms, buttocks, outer thighs, and calves at various times in the
past. But the mind boggles when I try to imagine how you could land in order to get inner-thigh road-rash!!!
Mike
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Date: 28 Oct 2007 19:51:45
From: John Thompson
Subject: Re: 160 psi
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On 2007-10-27, Jim Flom <jim.flomREMOVE@telus.net > wrote:
> Am I really faster, or do I just feel faster?
Yes.
--
John (john@os2.dhs.org)
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Date: 28 Oct 2007 03:02:05
From: still me
Subject: Re: 160 psi
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On Sat, 27 Oct 2007 23:35:32 GMT, "Jim Flom"
<jim.flomREMOVE@telus.net > wrote:
>Am I really faster, or do I just feel faster?
ur fast than me - I'm just sitting in a chair.
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Date: 27 Oct 2007 22:04:40
From: Tom Sherman
Subject: Re: 160 psi
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still me wrote:
> On Sat, 27 Oct 2007 23:35:32 GMT, "Jim Flom"
> <jim.flomREMOVE@telus.net> wrote:
>
>> Am I really faster, or do I just feel faster?
>
> ur fast than me - I'm just sitting in a chair.
Is not sitting in a chair how one rides a bicycle? ;)
--
Tom Sherman - Holstein-Friesland Bovinia
When did ignorance of biology become a "family value"?
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Date: 28 Oct 2007 18:49:43
From: Steve Gravrock
Subject: Re: 160 psi
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On 2007-10-28, Tom Sherman <sunsetss0003@yahoo.com > wrote:
> still me wrote:
>> On Sat, 27 Oct 2007 23:35:32 GMT, "Jim Flom"
>> <jim.flomREMOVE@telus.net> wrote:
>>
>>> Am I really faster, or do I just feel faster?
>>
>> ur fast than me - I'm just sitting in a chair.
>
> Is not sitting in a chair how one rides a bicycle? ;)
If you ever stop posting here, I think I can replace you with a script.
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Date: 27 Oct 2007 18:14:35
From: Bill Sornson
Subject: Re: 160 psi
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Jim Flom wrote:
> Am I really faster, or do I just feel faster?
The answer is obv----KABOOM!!!!!!!!!!!!
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Date: 27 Oct 2007 18:18:26
From:
Subject: Re: 160 psi
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On Sat, 27 Oct 2007 23:35:32 GMT, "Jim Flom"
<jim.flomREMOVE@telus.net > wrote:
>Am I really faster, or do I just feel faster?
Dear Jim,
It depends on what your original pressure and route were.
If you were rolling along on smooth flat pavement at 60 psi, you're
likely to be noticeably faster. More air pressure means less
deformation of the sidewalls, with less energy lost when the sidewalls
demonstrate that they're not perfect springs.
If you were rolling along on rougher flat pavement at 120 psi, you may
actually be slower. At 160 psi on rough pavement, you could be putting
more energy into uselessly jiggling the 150+ pound bike and its soggy
cargo than you save with air-stiffened sidewalls.
Jobst's tests of rolling resistance show that the reduction in rolling
resistance tapers off:
http://www.analyticcycling.com/ForcesTire_TireRollingResistance.html
On that graph, 3.5 kg/cm^2 = 50 psi
4.0 kg/cm^2 = 57 psi
5.0 kg/cm^2 = 71 psi
6.0 kg/cm^2 = 85 psi
7.0 kg/cm^2 = 100 psi
8.0 kg/cm^2 = 114 psi
9.0 kg/cm^2 = 128 psi
You're out here:
11.25 kg/cm^2 = 160 psi
Note that the lower the initial resistance, the less difference higher
pressure makes. The trend of the graph suggests that none of those
tires will lose much theoretical drag by raising 9 kg/cm^2 to 11.25
because the curves have already flattened out. Meanwhile, the real
world drag of useless jiggling as the over-pumped tires bang over tiny
rough spots in the road will be rising.
Cheers,
Carl Fogel
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Date: 28 Oct 2007 21:52:05
From: Jim Flom
Subject: Re: 160 psi
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<carlfogel@comcast.net > wrote in message
news:p8k7i3d50i3dua6nsdvl42er0lmlp0nqbm@4ax.com...
> On Sat, 27 Oct 2007 23:35:32 GMT, "Jim Flom"
> <jim.flomREMOVE@telus.net> wrote:
>
>>Am I really faster, or do I just feel faster?
>
> Dear Jim,
>
> It depends on what your original pressure and route were.
>
> If you were rolling along on smooth flat pavement at 60 psi, you're
> likely to be noticeably faster. More air pressure means less
> deformation of the sidewalls, with less energy lost when the sidewalls
> demonstrate that they're not perfect springs.
>
> If you were rolling along on rougher flat pavement at 120 psi, you may
> actually be slower. At 160 psi on rough pavement, you could be putting
> more energy into uselessly jiggling the 150+ pound bike and its soggy
> cargo than you save with air-stiffened sidewalls.
>
> Jobst's tests of rolling resistance show that the reduction in rolling
> resistance tapers off:
>
> http://www.analyticcycling.com/ForcesTire_TireRollingResistance.html
>
> On that graph, 3.5 kg/cm^2 = 50 psi
> 4.0 kg/cm^2 = 57 psi
> 5.0 kg/cm^2 = 71 psi
> 6.0 kg/cm^2 = 85 psi
> 7.0 kg/cm^2 = 100 psi
> 8.0 kg/cm^2 = 114 psi
> 9.0 kg/cm^2 = 128 psi
>
> You're out here:
> 11.25 kg/cm^2 = 160 psi
>
> Note that the lower the initial resistance, the less difference higher
> pressure makes. The trend of the graph suggests that none of those
> tires will lose much theoretical drag by raising 9 kg/cm^2 to 11.25
> because the curves have already flattened out. Meanwhile, the real
> world drag of useless jiggling as the over-pumped tires bang over tiny
> rough spots in the road will be rising.
Thank Carl. So yes I am (marginally) faster on a smooth road, but might be
arguably slower on a rough road.
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Date: 28 Oct 2007 18:59:21
From:
Subject: Re: 160 psi
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On Sun, 28 Oct 2007 21:52:05 GMT, "Jim Flom"
<jim.flomREMOVE@telus.net > wrote:
><carlfogel@comcast.net> wrote in message
>news:p8k7i3d50i3dua6nsdvl42er0lmlp0nqbm@4ax.com...
>> On Sat, 27 Oct 2007 23:35:32 GMT, "Jim Flom"
>> <jim.flomREMOVE@telus.net> wrote:
>>
>>>Am I really faster, or do I just feel faster?
>>
>> Dear Jim,
>>
>> It depends on what your original pressure and route were.
>>
>> If you were rolling along on smooth flat pavement at 60 psi, you're
>> likely to be noticeably faster. More air pressure means less
>> deformation of the sidewalls, with less energy lost when the sidewalls
>> demonstrate that they're not perfect springs.
>>
>> If you were rolling along on rougher flat pavement at 120 psi, you may
>> actually be slower. At 160 psi on rough pavement, you could be putting
>> more energy into uselessly jiggling the 150+ pound bike and its soggy
>> cargo than you save with air-stiffened sidewalls.
>>
>> Jobst's tests of rolling resistance show that the reduction in rolling
>> resistance tapers off:
>>
>> http://www.analyticcycling.com/ForcesTire_TireRollingResistance.html
>>
>> On that graph, 3.5 kg/cm^2 = 50 psi
>> 4.0 kg/cm^2 = 57 psi
>> 5.0 kg/cm^2 = 71 psi
>> 6.0 kg/cm^2 = 85 psi
>> 7.0 kg/cm^2 = 100 psi
>> 8.0 kg/cm^2 = 114 psi
>> 9.0 kg/cm^2 = 128 psi
>>
>> You're out here:
>> 11.25 kg/cm^2 = 160 psi
>>
>> Note that the lower the initial resistance, the less difference higher
>> pressure makes. The trend of the graph suggests that none of those
>> tires will lose much theoretical drag by raising 9 kg/cm^2 to 11.25
>> because the curves have already flattened out. Meanwhile, the real
>> world drag of useless jiggling as the over-pumped tires bang over tiny
>> rough spots in the road will be rising.
>
>Thank Carl. So yes I am (marginally) faster on a smooth road, but might be
>arguably slower on a rough road.
Dear Jim,
You can get a rough idea of just how marginal the difference is with
this calculator:
http://austinimage.com/bp/velocityN/velocity.html
Judging by the trend in Jobst's roller-drum tests, you'd be lucky to
reduce the rolling-resistance drag 10% by increasing inflation from
120 to 160 psi.
The calculator lets you reduce the 0.0050 rolling resistance 10% (or
anything you like) to 0.0045 and compare the details side-by-side.
For the defaults, that raises speed for 300 watts from 37.178 to
37.400 km/h, a rather marginal 0.222 km/h, and improves the time for
10 km from 16.138 to 16.042 minutes--a little less than 6 seconds.
For comparison, it's the same effect as a 0.35 km/h tailwind.
Cheers,
Carl Fogel
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Date: 29 Oct 2007 02:13:15
From: Jim Flom
Subject: Re: 160 psi
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<carlfogel@comcast.net > wrote...
>
> Dear Jim,
>
> You can get a rough idea of just how marginal the difference is with
> this calculator:
>
> http://austinimage.com/bp/velocityN/velocity.html
>
> Judging by the trend in Jobst's roller-drum tests, you'd be lucky to
> reduce the rolling-resistance drag 10% by increasing inflation from
> 120 to 160 psi.
>
> The calculator lets you reduce the 0.0050 rolling resistance 10% (or
> anything you like) to 0.0045 and compare the details side-by-side.
>
> For the defaults, that raises speed for 300 watts from 37.178 to
> 37.400 km/h, a rather marginal 0.222 km/h, and improves the time for
> 10 km from 16.138 to 16.042 minutes--a little less than 6 seconds.
>
> For comparison, it's the same effect as a 0.35 km/h tailwind.
>
> Cheers,
>
> Carl Fogel
Mind you, I'm not just doing it for fun. 160 is the prescribed psi for the
new tires my LBS sold me. I asked for Continentals (120 psi) but he
suggested (had in stock?) Vredesteins Fortezza SEs, which are I guess one
rung down from the one's he rides on (not that he's terribly strong).
Thanks Carl.
Jim
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Date: 29 Oct 2007 02:48:23
From: Ryan Cousineau
Subject: Re: 160 psi
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In article <%kbVi.45894$G25.35822@edtnps89 >,
"Jim Flom" <jim.flomREMOVE@telus.net > wrote:
> <carlfogel@comcast.net> wrote...
> >
> > Dear Jim,
> >
> > You can get a rough idea of just how marginal the difference is with
> > this calculator:
> >
> > http://austinimage.com/bp/velocityN/velocity.html
> >
> > Judging by the trend in Jobst's roller-drum tests, you'd be lucky to
> > reduce the rolling-resistance drag 10% by increasing inflation from
> > 120 to 160 psi.
> >
> > The calculator lets you reduce the 0.0050 rolling resistance 10% (or
> > anything you like) to 0.0045 and compare the details side-by-side.
> >
> > For the defaults, that raises speed for 300 watts from 37.178 to
> > 37.400 km/h, a rather marginal 0.222 km/h, and improves the time for
> > 10 km from 16.138 to 16.042 minutes--a little less than 6 seconds.
> >
> > For comparison, it's the same effect as a 0.35 km/h tailwind.
> >
> > Cheers,
> >
> > Carl Fogel
>
> Mind you, I'm not just doing it for fun. 160 is the prescribed psi for the
> new tires my LBS sold me. I asked for Continentals (120 psi) but he
> suggested (had in stock?) Vredesteins Fortezza SEs, which are I guess one
> rung down from the one's he rides on (not that he's terribly strong).
>
> Thanks Carl.
>
> Jim
Jim you poser! Run 'em at 120, unless you're at the velodrome.
-RjC.
--
Ryan Cousineau rcousine@sfu.ca http://www.wiredcola.com/
"My scenarios may give the impression I could be an excellent crook.
Not true - I am a talented lawyer." - Sandy in rec.bicycles.racing
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Date: 29 Oct 2007 02:57:36
From: Jim Flom
Subject: Re: 160 psi
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"Ryan Cousineau" <rcousine@sfu.ca > wrote...
>
> Jim you poser! Run 'em at 120, unless you're at the velodrome.
Dude, stick to your 'tub. How'd that go, anyway?
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Date: 29 Oct 2007 05:09:14
From: Ryan Cousineau
Subject: Re: 160 psi
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In article <A_bVi.45896$G25.36929@edtnps89 >,
"Jim Flom" <jim.flomREMOVE@telus.net > wrote:
> "Ryan Cousineau" <rcousine@sfu.ca> wrote...
> >
> > Jim you poser! Run 'em at 120, unless you're at the velodrome.
>
> Dude, stick to your 'tub. How'd that go, anyway?
Not yet. Next weekend. It's ordered though, so there's no backing out
now. You should totally drop by just to watch:
http://www.escapevelocity.bc.ca/crossquitlam
But speaking of CX, this weekend was a doubleheader. Hardly messy at all
on Saturday in Surrey, followed by very, very messy in Maple Ridge on
Sunday.
Hilariously messy! My race was punctuated by a huge fall-down on this
bizarre, mucky little off-camber hump of a corner about 100m from the
start. It worked out great for me, because I used my freaky-looking
running start to shoot from the back of the start grid up to about fifth
wheel at the corner. That wasn't close enough to be ahead of the
accident, but it was close enough to be able to ride around the accident
without stopping. Well, a little dab.
That meant I went into the next corner in an unprecedented 6th place, at
which point I tormented an unusually large selection of riders by,
despite numerous attempts by the ground to change things up, not falling
down. Well, a few dabs.
Of course, most of them passed me regardless. But it was hard work! I
got passed by one of the Cat 2s on my club (very powerful on the road,
hilariously unskilled in CX) only on the last lap. If I had known it was
him, I would have put him in the weeds (Hi, Axel!).
The course was so sloppy that eventually riding around corners with the
rear wheel in powerslide-oversteer on corner exit stopped being a
mistake, and started being a technique. I just routinely ran it into
corners where the front wheel would simply not control the direction of
travel for a few seconds.
ObTech: A few weeks ago I mentioned the discovery of fine, dry dirt
inside of my tire casing after a race. After this race, I discovered the
same phenomenon, only (urgh) inside my bike shorts.
--
Ryan Cousineau rcousine@sfu.ca http://www.wiredcola.com/
"My scenarios may give the impression I could be an excellent crook.
Not true - I am a talented lawyer." - Sandy in rec.bicycles.racing
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Date: 30 Oct 2007 01:41:09
From: Jim Flom
Subject: Re: 160 psi
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"Ryan Cousineau" <rcousine@sfu.ca > wrote in message
news:rcousine-9B76C2.22091828102007@news.telus.net...
> In article <A_bVi.45896$G25.36929@edtnps89>,
> "Jim Flom" <jim.flomREMOVE@telus.net> wrote:
>
>> "Ryan Cousineau" <rcousine@sfu.ca> wrote...
>> >
>> > Jim you poser! Run 'em at 120, unless you're at the velodrome.
>>
>> Dude, stick to your 'tub. How'd that go, anyway?
>
> Not yet. Next weekend. It's ordered though, so there's no backing out
> now. You should totally drop by just to watch:
I'm actually planning to be in Vancouver Friday night to crack of dawn
Sunday. we should meet in real life. Let's work this out on Facebook, if
you don't mind being interrupted in your musings about your hilariously
muddy weekend (which, evidently you don't).
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Date: 29 Oct 2007 15:10:49
From: A Muzi
Subject: Re: 160 psi
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>> "Ryan Cousineau" <rcousine@sfu.ca> wrote...
>>> Jim you poser! Run 'em at 120, unless you're at the velodrome.
> "Jim Flom" <jim.flomREMOVE@telus.net> wrote:
>> Dude, stick to your 'tub. How'd that go, anyway?
Ryan Cousineau wrote:
> Not yet. Next weekend. It's ordered though, so there's no backing out
> now. You should totally drop by just to watch:
>
> http://www.escapevelocity.bc.ca/crossquitlam
>
> But speaking of CX, this weekend was a doubleheader. Hardly messy at all
> on Saturday in Surrey, followed by very, very messy in Maple Ridge on
> Sunday.
>
> Hilariously messy! My race was punctuated by a huge fall-down on this
> bizarre, mucky little off-camber hump of a corner about 100m from the
> start. It worked out great for me, because I used my freaky-looking
> running start to shoot from the back of the start grid up to about fifth
> wheel at the corner. That wasn't close enough to be ahead of the
> accident, but it was close enough to be able to ride around the accident
> without stopping. Well, a little dab.
>
> That meant I went into the next corner in an unprecedented 6th place, at
> which point I tormented an unusually large selection of riders by,
> despite numerous attempts by the ground to change things up, not falling
> down. Well, a few dabs.
>
> Of course, most of them passed me regardless. But it was hard work! I
> got passed by one of the Cat 2s on my club (very powerful on the road,
> hilariously unskilled in CX) only on the last lap. If I had known it was
> him, I would have put him in the weeds (Hi, Axel!).
>
> The course was so sloppy that eventually riding around corners with the
> rear wheel in powerslide-oversteer on corner exit stopped being a
> mistake, and started being a technique. I just routinely ran it into
> corners where the front wheel would simply not control the direction of
> travel for a few seconds.
>
> ObTech: A few weeks ago I mentioned the discovery of fine, dry dirt
> inside of my tire casing after a race. After this race, I discovered the
> same phenomenon, only (urgh) inside my bike shorts.
"mucky little off-camber hump "
I think r.b.t. has a concurrent thread about that. Or a bike like it.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971
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Date: 30 Oct 2007 02:42:05
From: Ryan Cousineau
Subject: Re: 160 psi
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In article <13icivpp5p5lp47@corp.supernews.com >,
A Muzi <am@yellowjersey.org > wrote:
> >> "Ryan Cousineau" <rcousine@sfu.ca> wrote...
> >>> Jim you poser! Run 'em at 120, unless you're at the velodrome.
>
> > "Jim Flom" <jim.flomREMOVE@telus.net> wrote:
> >> Dude, stick to your 'tub. How'd that go, anyway?
>
> Ryan Cousineau wrote:
> > Not yet. Next weekend. It's ordered though, so there's no backing out
> > now. You should totally drop by just to watch:
> >
> > http://www.escapevelocity.bc.ca/crossquitlam
> >
> > But speaking of CX, this weekend was a doubleheader. Hardly messy at all
> > on Saturday in Surrey, followed by very, very messy in Maple Ridge on
> > Sunday.
> >
> > Hilariously messy! My race was punctuated by a huge fall-down on this
> > bizarre, mucky little off-camber hump of a corner about 100m from the
> > start. It worked out great for me, because I used my freaky-looking
> > running start to shoot from the back of the start grid up to about fifth
> > wheel at the corner. That wasn't close enough to be ahead of the
> > accident, but it was close enough to be able to ride around the accident
> > without stopping. Well, a little dab.
> "mucky little off-camber hump "
> I think r.b.t. has a concurrent thread about that. Or a bike like it.
This was more of a...group thing...
--
Ryan Cousineau rcousine@sfu.ca http://www.wiredcola.com/
"My scenarios may give the impression I could be an excellent crook.
Not true - I am a talented lawyer." - Sandy in rec.bicycles.racing
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Date: 28 Oct 2007 22:21:00
From: Paul Myron Hobson
Subject: Re: 160 psi
|
Jim Flom wrote:
> Mind you, I'm not just doing it for fun. 160 is the prescribed psi for the
> new tires my LBS sold me. I asked for Continentals (120 psi) but he
> suggested (had in stock?) Vredesteins Fortezza SEs, which are I guess one
> rung down from the one's he rides on (not that he's terribly strong).
Oh. You *definitely* do not have to run the sidewall pressures of a
tire. My 28 mm tires recommend 115 psi with a max of 125 psi. I'm a
light guy, so at 90 psi they feel quite harsh. And pretty comfortable
at about 75 psi.
\\paul
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