I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?


Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

On Tue, 29 Mar 2005 19:32:53 +0100, Kinky Cowboy >
wrote:

>I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
>UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?

<mode="flippant">
Not if you're on a mountain bike wth 559 rims.
</mode>

<mode="stoned">
I dunno, man, which one gives you the better buzz?
</mode>

Well, it depends. Are you in a hurry? Does comfort count? Are you
breaking a sweat with the 700/37 tires where you breezed with the
700/23 previously? Is the route bumpy? Is the route entirely paved?
Will a 37 fit inside the forks? Does your tire pump inflate to 100psi
without turning the task into a week's worth of calisthenics?

There are so many unspecified possible variables (all the way down to
"will I look like Fred if I run fat tires?") that it's really hard to
make a recommendation.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Kinky Cowboy wrote:
> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?

i'm 280lbs and now run my Ultrasport 700x23c at 120psi.
running them at 80psi lead to snake-bite punctures along my commute =(
100psi is ok, but at 120psi that rolling resistance *feels* lower.
but thats entirely subjective.

not seen the SportContact range so can't comment on those.
the UltraSport are only 25$AU, handle pretty well, but i've had problems
with the Conti presta tubes ... perhaps its just the way the pump and
the fitting (don't) snapon.

cheers,

kim

Kinky Cowboy wrote:
> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
>
>

Are your legs shaved?

On Tue, 29 Mar 2005 19:32:53 +0100, Kinky Cowboy
> wrote:

>I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
>UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
>
>
>Kinky Cowboy*
>
>*Batteries not included
>May contain traces of nuts
>Your milage may vary

Dear Kinky,

While it doesn't offer quite what you're after, you may get
some idea by looking at this calculator:

http://www.analyticcycling.com/ForcesTires_Page.html

You can raise the default speed to 8.5 m/s for 19 mph, set
the slope to 0, raise the weight to 100 kg (200-lb rider,
20-lb bike), and get 19 mph power results for premium,
utility, and touring clincher tires at 80 and 100 psi.

100.0% 130.6 watts premium 100 psi
104.0% 135.9 watts premium 80 psi

108.5% 141.7 watts utility 100 psi
113.9% 148.8 watts utility 80 psi

117.0% 152.8 watts touring 100 psi
123.7% 161.6 watts touring 80 psi

For the last case of the 80 psi touring tire, 130.4 watts
produces 7.68 m/s, or 17.2 mph, about a 10% speed drop from
the premium 100 psi tire's 130.6 watt 19 mph.

But these differences are more construction than width:

"Premium Thin tread, thin high-thread count casing, thin
tube"

"Utility Thicker tread, more layers of casing under tread,
typical tube"

"Touring Thick tread, thick sidewalls, typical tube"

http://www.analyticcycling.com/ForcesTires_Page.html

Wider means more wind drag, but can mean less rolling
resistance at the same pressure--which doesn't help much,
since most people use wider for lower pressures.

Comfort, handling, tire cost, pumping up flats, and so forth
raise other issues. For example, given random hazards, a
wider tire is more likely to pick up a thorn than a narrower
one. After the flat is fixed, it requires less pressure and
less final pump effort, but more pumping because of the
larger volume.

The trick would be to find a repeatable route of some
distance and average times for a month or so with each tire.
This requires considerable patience and interest in details,
but if it actually made something like a 10% difference in
your speed, the glow of satisfaction would keep you warm all
winter.

Carl Fogel

Kinky Cowboy > wrote in
news:1112121129.b204b6245b34a1e3d0c7662000cc96d4@t eranews:
> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?

Aerodynamics of tires has very little impact on your speed. This is more a
comfort vs. performance decision. If you are happy with your ride smoothness
on 23 tires, you will likely be very disappointed with your performance on 37
tires.

On Wed, 30 Mar 2005 00:13:00 GMT, Werehatrack
> wrote:

>On Tue, 29 Mar 2005 19:32:53 +0100, Kinky Cowboy >
>wrote:
>
>>I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
>>UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
>
><mode="flippant">
>Not if you're on a mountain bike wth 559 rims.
></mode>
>
><mode="stoned">
>I dunno, man, which one gives you the better buzz?
></mode>
>
>Well, it depends. Are you in a hurry? Does comfort count? Are you
>breaking a sweat with the 700/37 tires where you breezed with the
>700/23 previously? Is the route bumpy? Is the route entirely paved?
>Will a 37 fit inside the forks? Does your tire pump inflate to 100psi
>without turning the task into a week's worth of calisthenics?

I wouldn't mind some more comfort, but not at the expense of speed. I
haven't got the 37c tyres yet, just wondering if I should. It's all
paved and not too rough. The 37c will not only fit, but it will
probably look better because it will fill up big empty the spaces :-)
Pumping is no problem, I have a good track pump.

>There are so many unspecified possible variables (all the way down to
>"will I look like Fred if I run fat tires?") that it's really hard to
>make a recommendation.

On Tue, 29 Mar 2005 18:59:06 -0700, wrote:

>Dear Kinky,
>
>While it doesn't offer quite what you're after, you may get
>some idea by looking at this calculator:
>
>http://www.analyticcycling.com/ForcesTires_Page.html
>
>You can raise the default speed to 8.5 m/s for 19 mph, set
>the slope to 0, raise the weight to 100 kg (200-lb rider,
>20-lb bike), and get 19 mph power results for premium,
>utility, and touring clincher tires at 80 and 100 psi.
>
>100.0% 130.6 watts premium 100 psi
>104.0% 135.9 watts premium 80 psi
>
>108.5% 141.7 watts utility 100 psi
>113.9% 148.8 watts utility 80 psi
>
>117.0% 152.8 watts touring 100 psi
>123.7% 161.6 watts touring 80 psi
>
>For the last case of the 80 psi touring tire, 130.4 watts
>produces 7.68 m/s, or 17.2 mph, about a 10% speed drop from
>the premium 100 psi tire's 130.6 watt 19 mph.
>
>But these differences are more construction than width:
>
>Wider means more wind drag, but can mean less rolling
>resistance at the same pressure--which doesn't help much,
>since most people use wider for lower pressures.
>

That's the point at the centre of my question; the two tyres are of
somewhat similar quality, so the width is probably the greatest
determinant of rolling resistance differences. From Schwalbe's
marketing material, it looks likely that the wider tyre would have
lower rolling resistance at 80psi than the narrower one at 100 all
other things being equal. (This speculation based on their statement
that a 60c tyre at 2 bar has the same rolling resistance as a 37c tyre
at 4 bar)

>Comfort, handling, tire cost, pumping up flats, and so forth
>raise other issues. For example, given random hazards, a
>wider tire is more likely to pick up a thorn than a narrower
>one. After the flat is fixed, it requires less pressure and
>less final pump effort, but more pumping because of the
>larger volume.
>
>The trick would be to find a repeatable route of some
>distance and average times for a month or so with each tire.
>This requires considerable patience and interest in details,
>but if it actually made something like a 10% difference in
>your speed, the glow of satisfaction would keep you warm all
>winter.
>
>Carl Fogel

This is actually what I'm interested in, but I wondered whether I
could get the answer without spending $60 on some extra tyres; I
already have two pairs of identical wheels, and a Polar S720 HRM with
cycle computer functions so the data logging aspect is covered. Looks
like I'll have to alternate wheelsets until a favourite emerges :-)




Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

Kinky Cowboy > wrote in message news:<1112121129.b204b6245b34a1e3d0c7662000cc96d4@terane ws>...
> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
>
>
> Kinky Cowboy*
>
> *Batteries not included
> May contain traces of nuts
> Your milage may vary

I would say that if you are cruising at 18 to 20mph you would fall
into the category of fast recreational rider. Any faster and you move
into the racing category were aerodynamics and position on the bike
become a limiting factor.
At the speed you are riding at (assuming on the tops, brakehoods)
rolling resistance is still a major contributor. Assumin you are
outputting on average 190W, here's a guide to what you could expect
with each set of tires when riding a distance of 30 km:

UltraSport 700x23c at 100psi on pavement, Crr ~ 0.0065

Results
=======
Velocity [km/h] ........................ 30.239

Time [hour:min:sec] .................... 0:59:31
Time [sec:msec] ........................ 3571.496

Power Total [W] ........................ 190.0
Power Air Resistance [W] ............... 130.9 68.90%
Power Rolling Resistance [W] ........... 54.3 28.60%
Power Drive Train [W] .................. 4.7 2.50%


Conti SportContact 700x37c at 80psi on pavement, Crr ~ 0.0090

Results
=======
Velocity [km/h] ........................ 28.835

Time [hour:min:sec] .................... 1:2:25
Time [sec:msec] ........................ 3745.456

Power Total [W] ........................ 190.0
Power Air Resistance [W] ............... 113.5 59.73%
Power Rolling Resistance [W] ........... 71.8 37.77%
Power Drive Train [W] .................. 4.8 2.50%


So if you want to ride ~ 3 minutes faster for 30 km stick with the
700x23c.

On 30 Mar 2005 08:06:10 -0800, (Rik O'Shea) wrote:

>Kinky Cowboy > wrote in message news:<1112121129.b204b6245b34a1e3d0c7662000cc96d4@terane ws>...
>> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
>> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
>
>At the speed you are riding at (assuming on the tops, brakehoods)
>rolling resistance is still a major contributor. Assumin you are
>outputting on average 190W, here's a guide to what you could expect
>with each set of tires when riding a distance of 30 km:
>
>UltraSport 700x23c at 100psi on pavement, Crr ~ 0.0065
>
>Conti SportContact 700x37c at 80psi on pavement, Crr ~ 0.0090
>
>
>
>So if you want to ride ~ 3 minutes faster for 30 km stick with the
>700x23c.

How did you arrive at these numbers? Assuming your first one is
correct, I should get <0.0065 at 100psi for the SportContact, ignoring
any differences in construction method, so a jump to 0.0090 at 80 psi
seems steep. As previously stated, Schwalbe consider a 60% increase in
section width combined with 50% drop in pressure maintains the same
rolling resistance, so my 60% increase in section width with only a
20% pressure drop should mean a lower Crr for the wider tyre.


Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

Kinky Cowboy wrote:

> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?

700 x 23c. The point where aerodynamics become more important is
generally held to be about 15mph.

Kinky Cowboy > wrote in message news:<1112201545.5103a4cd575fb18b3a28b2fa71ebdff4@terane ws>...
> On 30 Mar 2005 08:06:10 -0800, (Rik O'Shea) wrote:
>
> >Kinky Cowboy > wrote in message news:<1112121129.b204b6245b34a1e3d0c7662000cc96d4@terane ws>...
> >> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
> >> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
> >
> >At the speed you are riding at (assuming on the tops, brakehoods)
> >rolling resistance is still a major contributor. Assumin you are
> >outputting on average 190W, here's a guide to what you could expect
> >with each set of tires when riding a distance of 30 km:
> >
> >UltraSport 700x23c at 100psi on pavement, Crr ~ 0.0065
> >
> >Conti SportContact 700x37c at 80psi on pavement, Crr ~ 0.0090
> >
> >
> >
> >So if you want to ride ~ 3 minutes faster for 30 km stick with the
> >700x23c.

>
> How did you arrive at these numbers? Assuming your first one is
> correct, I should get <0.0065 at 100psi for the SportContact, ignoring
> any differences in construction method, so a jump to 0.0090 at 80 psi
> seems steep. As previously stated, Schwalbe consider a 60% increase in
> section width combined with 50% drop in pressure maintains the same
> rolling resistance, so my 60% increase in section width with only a
> 20% pressure drop should mean a lower Crr for the wider tyre.
>
>

Its not as simple as you point out. Assuming the contact surface is a
constant, then Crr depends on thread thickness, compound, casing
(TPI), and inner tube.
The very best, "top-of-the range" clincher with ultra light tubes on
smooth asphalt pumped to max recommended inflation pressure will give
a Crr between 0.0040 and 0.0050.

I would be very surprised if a 700x37c sports tire @ 80psi would give
a Crr below the 0.0090 (+/- 0.0010)

The main point is that a fast recreational cyclist tends to ride in a
relatively un-aero postion or at least semi aero position (with an
estimated Cd in the range 0.90 +/- 0.05, compared to say a
time-trialist with full kit in an aero position, estimated Cd in the
range 0.70 +/- 0.05). And because of this fact the
power requirement to overcome rolling resisteance for a fast
recreational cyclist tend to amount to ~30% of overall power output.
So if you want to stay at the same speed for the same power stick with
the with the 700x23c. If you dont care about average speed then go
with the fatter tyres.

On 31 Mar 2005 05:46:48 -0800, (Rik O'Shea) wrote:

>Kinky Cowboy > wrote in message news:<1112201545.5103a4cd575fb18b3a28b2fa71ebdff4@terane ws>...
>> On 30 Mar 2005 08:06:10 -0800, (Rik O'Shea) wrote:
>>
>> >Kinky Cowboy > wrote in message news:<1112121129.b204b6245b34a1e3d0c7662000cc96d4@terane ws>...
>> >> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
>> >> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
>> >
>> >At the speed you are riding at (assuming on the tops, brakehoods)
>> >rolling resistance is still a major contributor. Assumin you are
>> >outputting on average 190W, here's a guide to what you could expect
>> >with each set of tires when riding a distance of 30 km:
>> >
>> >UltraSport 700x23c at 100psi on pavement, Crr ~ 0.0065
>> >
>> >Conti SportContact 700x37c at 80psi on pavement, Crr ~ 0.0090
>> >
>> >
>> >
>> >So if you want to ride ~ 3 minutes faster for 30 km stick with the
>> >700x23c.
>
>>
>> How did you arrive at these numbers? Assuming your first one is
>> correct, I should get <0.0065 at 100psi for the SportContact, ignoring
>> any differences in construction method, so a jump to 0.0090 at 80 psi
>> seems steep. As previously stated, Schwalbe consider a 60% increase in
>> section width combined with 50% drop in pressure maintains the same
>> rolling resistance, so my 60% increase in section width with only a
>> 20% pressure drop should mean a lower Crr for the wider tyre.
>>
>>
>
>Its not as simple as you point out. Assuming the contact surface is a
>constant, then Crr depends on thread thickness, compound, casing
>(TPI), and inner tube.
>The very best, "top-of-the range" clincher with ultra light tubes on
>smooth asphalt pumped to max recommended inflation pressure will give
>a Crr between 0.0040 and 0.0050.

But the Conti UltraSport is a long way from being a top-of-the-range
tyre. I've got GP Supersonics on my TT bike, which really do roll.

>I would be very surprised if a 700x37c sports tire @ 80psi would give
>a Crr below the 0.0090 (+/- 0.0010)

And the SportContact is sold as being the fast rolling tyre in this
section, and it has a much finer casing than the UltaSport, albeit 4
ply instead of the 3 on the narrower tyre. So it might not be as
simple as you point out, either.

Anyway, you've answered my question on the source of your figures,
which is that you made them up. I have a feeling this can only be
settled by actual measurement.





Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

>Kinky Cowboy > wrote in message news:<1112201545.5103a4cd575fb18b3a28b2fa71ebdff4@terane ws>...
>> On 30 Mar 2005 08:06:10 -0800, (Rik O'Shea) wrote:
>>
>> >Kinky Cowboy > wrote in message news:<1112121129.b204b6245b34a1e3d0c7662000cc96d4@terane ws>...
>> >> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
>> >> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?

>Anyway, you've answered my question on the source of your figures, which is that you made them up. I have a feeling this can only be settled by actual measurement.

OK, now I have the wide tyres, I need to do the tests. I'm thinking
flat road (the one across the flood plain is handy) and accelerate to
about 22mph, stop pedalling when I cross some kind of preset start
line, coast down to about 15mph and measure dV/dt from the resulting
graphs obtained from my Polar S720 computer. Do it in both directions,
swap the wheels a couple of times, try to pick a calm day etc.

Any comments on the protocol welcome, and I'll post the graphs on my
website after the tests.


Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary

Kinky Cowboy > writes:

>>Kinky Cowboy > wrote in message news:<1112201545.5103a4cd575fb18b3a28b2fa71ebdff4@terane ws>...
>>> On 30 Mar 2005 08:06:10 -0800, (Rik O'Shea) wrote:
>>>
>>> >Kinky Cowboy > wrote in message news:<1112121129.b204b6245b34a1e3d0c7662000cc96d4@terane ws>...
>>> >> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
>>> >> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
>
>>Anyway, you've answered my question on the source of your figures, which is that you made them up. I have a feeling this can only be settled by actual measurement.
>
> OK, now I have the wide tyres, I need to do the tests. I'm thinking
> flat road (the one across the flood plain is handy) and accelerate to
> about 22mph, stop pedalling when I cross some kind of preset start
> line, coast down to about 15mph and measure dV/dt from the resulting
> graphs obtained from my Polar S720 computer. Do it in both directions,
> swap the wheels a couple of times, try to pick a calm day etc.
>
> Any comments on the protocol welcome, and I'll post the graphs on my
> website after the tests.

No suggestions, but looking forward to seeing the results!

On Tue, 05 Apr 2005 22:43:36 +0100, Kinky Cowboy
> wrote:

>>Kinky Cowboy > wrote in message news:<1112201545.5103a4cd575fb18b3a28b2fa71ebdff4@terane ws>...
>>> On 30 Mar 2005 08:06:10 -0800, (Rik O'Shea) wrote:
>>>
>>> >Kinky Cowboy > wrote in message news:<1112121129.b204b6245b34a1e3d0c7662000cc96d4@terane ws>...
>>> >> I'm a 200lb rider cruising at 18 to 20mph. Should I be on Conti
>>> >> UltraSport 700x23c at 100psi or Conti SportContact 700x37c at 80psi?
>
>>Anyway, you've answered my question on the source of your figures, which is that you made them up. I have a feeling this can only be settled by actual measurement.
>
>OK, now I have the wide tyres, I need to do the tests. I'm thinking
>flat road (the one across the flood plain is handy) and accelerate to
>about 22mph, stop pedalling when I cross some kind of preset start
>line, coast down to about 15mph and measure dV/dt from the resulting
>graphs obtained from my Polar S720 computer. Do it in both directions,
>swap the wheels a couple of times, try to pick a calm day etc.
>
>Any comments on the protocol welcome, and I'll post the graphs on my
>website after the tests.
>
>
>Kinky Cowboy*
>
>*Batteries not included
>May contain traces of nuts
>Your milage may vary

Dear Kinky,

It will be interesting to hear whether your test shows a
difference.

To do it both ways, you may need to take a few runs to find
a mark from each direction so that the coasting area is the
same stretch of road.

I hear that the wind is usually calmest at dawn, but don't
wake me up for it.

Have fun,

Carl Fogel

On Tue, 05 Apr 2005 17:00:33 -0600, wrote:

>On Tue, 05 Apr 2005 22:43:36 +0100, Kinky Cowboy
> wrote:
>>swap the wheels a couple of times, try to pick a calm day etc.
>>
>>Any comments on the protocol welcome, and I'll post the graphs on my
>>website after the tests.
>>
>>
>>Kinky Cowboy*
>>
>Dear Kinky,
>
>It will be interesting to hear whether your test shows a
>difference.
>
>To do it both ways, you may need to take a few runs to find
>a mark from each direction so that the coasting area is the
>same stretch of road.
>
>I hear that the wind is usually calmest at dawn, but don't
>wake me up for it.
>
>Have fun,
>
>Carl Fogel

Dawn here (UK) will be 11pm there, so it shouldn't be a case of waking
you up so much as keeping you up late :-)

Kinky Cowboy*

*Batteries not included
May contain traces of nuts
Your milage may vary