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700/23 vs 700/25 tires ?



 
 
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  #21  
Old January 29th 09, 08:43 PM posted to rec.bicycles.tech
Nick L Plate
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Posts: 1,114
Default 700/23 vs 700/25 tires ?

Wired on tyres, 25mm+ on rear perhaps 22+on front, anything less is
painful if you're 3+ hours in the saddle. Rider fatigue caused by
constant road shock will slow you more over a long ride, than a less
than optimum aero tyre/rim combination.
If you 'need' narrow tyres, use tubs, a 23mm tub is more comfortable
and grips better in the corners(than 25mm wired) due to a longer
contact patch at an appropriate riding pressure. Steering response
will also become less jittery with a short trail set up. Confidence
in cornering over rough surfaces improves reducing rider tension and
improves speed through corners.

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  #22  
Old January 29th 09, 09:31 PM posted to rec.bicycles.tech
[email protected]
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Default 700/23 vs 700/25 tires ?

On Thu, 29 Jan 2009 18:21:50 GMT, John Forrest Tomlinson
wrote:

On Thu, 29 Jan 2009 10:12:44 -0800 (PST), Chalo
wrote:


The faster you ride, the more you need in terms of rim protection,
shock absorption, wear resistance, pinch flat resistance, and
traction. So the faster you go, the more you can benefit from a wider
tire.


I can see that for traction, though very few people go near the limits
of traction on moderatley narrow tires.

But why do you need more for rim protection when going fast?


[snip]

Dear John,

The faster the hammer hits the nail, the deeper the nail goes into the
wood.

More rim protection is needed at higher speeds because impact roughly
corresponds to kinetic energy, which is half the mass times the square
of the velocity--it rises even faster than the speed.

At 20 mph, a rider hits a chunk of gravel (oops!) with an impact of
20^2 whomps, or 400 whomps.

At 25 mph, the same rider hits the same chunk of gravel at 25^2
whomps, or 625 whomps.

At 30 mph, he hits it at 30^2 whomps, or 900 whomps, more than twice
as hard.

That's why drivers slow down on rough roads and why faster riders get
more pinch flats on bicycles.

Cheers,

Carl Fogel
  #23  
Old January 29th 09, 09:48 PM posted to rec.bicycles.tech
Jay Beattie
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Posts: 4,322
Default 700/23 vs 700/25 tires ?

On Jan 29, 10:21*am, John Forrest Tomlinson
wrote:
On Thu, 29 Jan 2009 10:12:44 -0800 (PST), Chalo

wrote:

The faster you ride, the more you need in terms of rim protection,
shock absorption, wear resistance, pinch flat resistance, and
traction. *So the faster you go, the more you can benefit from a wider
tire.


I can see that for traction, though very few people go near the limits
of traction on moderatley narrow tires.

But why dod you need more for rim protection when going fast? *Or
shock absorbtion? *Or wear resistance?

And more to the point, do people trying to go fast care about a little
extra shock absorbtion?

When I'm going fast there's more weight on my legs and less on my
hands and butt, so I notice shocks less than when just rolling along
slowly. *

And Chalo - I have a couple friends who weigh 100-105 lbs. *In your
scheme of things, are they allowed to ride 23s or woudl you tell them
they'd be better off riding 25s or larger? *Not knowing them or their
riding goals. *Well?


It's funny. I remember when 23mms were considered fat. We were
racing on 19mm and 20mm clinchers or on sewups (my racing weight
187-195). When I switched to 23s, it made a difference, but that was
probably because I changed over to team supplied Conti 23s that were
probably 25s. They were squishier, and I didn't like them (yah, I
know that is impossible if both tires had the same inflation pressure
-- but it was squishier).

Also, the difference between 23mm and 25mm is sometimes just a label
-- being that nominal sizes are often wrong. I have found differences
in tires of the same size, though. For example, a 23mm kevlar belted
bomb-proof tire like a Bontrager Hardcase will not roll as well as a
23mm ProRace. Whether that affects your result in a race is hard to
say.

I use big fat tires during winter (28-35mm) because they give me
better traction on wet pavement and more float in the post-snow
gravel. They do not ride like 23mm ProRaces, and the penalty is
significant IMO -- particularly slogging through the hills. I would
not ride them in a race except maybe a cross race on packed dirt.- Jay
Beattie.
  #24  
Old January 29th 09, 10:32 PM posted to rec.bicycles.tech
Keiron[_2_]
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Default 700/23 vs 700/25 tires ?

On Wed, 28 Jan 2009 19:38:42 -0800, Chalo wrote:

jeffreybike wrote:

Is there any real difference between 23mm and 25mm tires as far as
speed. Will 2mm make you that slower or faster?


There is no significant difference in speed between those two sizes of
tire. Too narrow a tire will slow you down quite a lot when you get a
pinch flat and have to stop and repair it.

Instrumented tests have shown that for tires of equal construction,
wider tires have slightly less rolling resistance at the same pressure.

--snip--
According to Sheldon this is rather moot as generally speaking wider tyres
at the same pressure are over inflated or narrow tyres at a same pressure
to wider ones will be under inflated (and so not being used optimality
presumably). As I understand it anyway. Might not be that relevant with
the 2mm difference but just throwing out there.

Having said that: in reality little difference in speed I suppose.
  #25  
Old January 29th 09, 10:51 PM posted to rec.bicycles.tech
John Forrest Tomlinson
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Posts: 6,564
Default 700/23 vs 700/25 tires ?

On Thu, 29 Jan 2009 11:43:01 -0800 (PST), Nick L Plate
wrote:

Confidence
in cornering over rough surfaces improves reducing rider tension and
improves speed through corners.


Good point.
  #26  
Old January 30th 09, 01:02 AM posted to rec.bicycles.tech
pm
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Posts: 344
Default 700/23 vs 700/25 tires ?

On Jan 29, 1:32*pm, Keiron wrote:
On Wed, 28 Jan 2009 19:38:42 -0800, Chalo wrote:
jeffreybike wrote:


Is there any real difference between 23mm and 25mm tires as far as
speed. Will 2mm make you that slower or faster?


There is no significant difference in speed between those two sizes of
tire. *Too narrow a tire will slow you down quite a lot when you get a
pinch flat and have to stop and repair it.


Instrumented tests have shown that for tires of equal construction,
wider tires have slightly less rolling resistance at the same pressure.


--snip--
According to Sheldon this is rather moot as generally speaking wider tyres
at the same pressure are over inflated or narrow tyres at a same pressure
to wider ones will be under inflated (and so not being used optimality
presumably). As I understand it anyway. Might not be that relevant with
the 2mm difference but just throwing out there.


Additionally, at equal pressures a wider tire will give a _worse_ ride
than a narrower tire. (consider how the size and shape of the contact
patch varies with the amount of compression)

-pm
  #27  
Old January 30th 09, 01:04 AM posted to rec.bicycles.tech
Frank Krygowski[_2_]
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Posts: 7,511
Default 700/23 vs 700/25 tires ?

On Jan 29, 3:48*pm, Jay Beattie wrote:

Also, the difference between 23mm and 25mm is sometimes just a label
-- being that nominal sizes are often wrong. *I have found differences
in tires of the same size, though. *For example, a 23mm kevlar belted
bomb-proof tire like a Bontrager Hardcase will not roll as well as a
23mm ProRace. Whether that affects your result in a race is hard to
say.


I think it's well documented that Kevlar belts increase rolling
resistance significantly. It's something I noticed and disliked. In
fact, I gave away a set of belted tires because they felt so dead to
me.

- Frank Krygowski
  #28  
Old January 30th 09, 02:17 AM posted to rec.bicycles.tech
Chalo
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Posts: 5,093
Default 700/23 vs 700/25 tires ?

John Forrest Tomlinson wrote:

Chalo wrote:

The faster you ride, the more you need in terms of rim protection,
shock absorption, wear resistance, pinch flat resistance, and
traction. So the faster you go, the more you can benefit from a wider
tire.


I can see that for traction, though very few people go near the limits
of traction on moderatley narrow tires.

But why dod you need more for rim protection when going fast? Or
shock absorbtion? Or wear resistance?


Because the energy contained in bumps goes up as the square of the
speed. It's four times easier to pinch flat or flat spot a rim at
30mph than at 15mph.

And more to the point, do people trying to go fast care about a little
extra shock absorbtion?


Why wouldn't they? Every watt of muscle power they spend absorbing
bumps is a watt that doesn't make them go any faster.

http://www.canosoarus.com/08LSRbicycle/LSR%20Bike01.htm
http://davesbikeblog.squarespace.com...ge/Speed04.jpg
http://www.fredrompelberg.com/upload...cord_fiets.JPG

These are bikes which went very fast indeed, for which rolling
resistance was a primary limiting factor in the speeds they reached,
and which used both fat tires and front suspension even though they
rode on one of the smoothest, least blemished surfaces available
anywhere.

And Chalo - I have a couple friends who weigh 100-105 lbs. In your
scheme of things, are they allowed to ride 23s or woudl you tell them
they'd be better off riding 25s or larger? Not knowing them or their
riding goals.


If they ride on the streets I ride on, the smallest I could recommend
is 28mm. That's what my wife uses, and she rides about as slowly and
sedately as any able-bodied person could. For much smoother and
better maintained streets, perhaps a narrower tire would be
acceptable.

Chalo

  #29  
Old January 30th 09, 02:29 AM posted to rec.bicycles.tech
John Forrest Tomlinson
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Posts: 6,564
Default 700/23 vs 700/25 tires ?

On Thu, 29 Jan 2009 17:17:50 -0800 (PST), Chalo
wrote:

And Chalo - I have a couple friends who weigh 100-105 lbs. In your
scheme of things, are they allowed to ride 23s or woudl you tell them
they'd be better off riding 25s or larger? Not knowing them or their
riding goals.


If they ride on the streets I ride on, the smallest I could recommend
is 28mm. That's what my wife uses, and she rides about as slowly and
sedately as any able-bodied person could.


OK I have to say it - you're a dogmatic idiot on tire size. To make
such a suggestion based on your wife, w/o knowing them. The correct
answer to my question is some other questions: "What kind of riding
are they doing? On what roads? What are their goals." Not some huge
boy dogma.

Why TF should people who weigh 100 pounds and compete in some of the
toughest bike races in the US use 28s? It's absurd. It's saying "I
want to do worse than I can."


  #30  
Old January 30th 09, 02:30 AM posted to rec.bicycles.tech
John Forrest Tomlinson
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Posts: 6,564
Default 700/23 vs 700/25 tires ?

On Thu, 29 Jan 2009 17:17:50 -0800 (PST), Chalo
wrote:

But why dod you need more for rim protection when going fast? Or
shock absorbtion? Or wear resistance?


Because the energy contained in bumps goes up as the square of the
speed. It's four times easier to pinch flat or flat spot a rim at
30mph than at 15mph.


Bumps have only a horizontal component? Interesting.


 




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