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700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.



 
 
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  #11  
Old November 9th 11, 12:13 AM posted to aus.bicycle
John Henderson
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Posts: 413
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.

F Murtz wrote:

What about the fact that the skinny tyre is often run at over 100 PSI
and the fat tyre at 40 PSI


Run the wide tyre at its rated maximum instead of 40 PSI. It'll
be more comfortable, stable and faster than a narrow tyre run at
the same pressure. There are 2"/50mm tyres with 65, 70 and even
85 PSI ratings.

Thare's no doubt that your 40 vs 100 PSI comparison favours the
narrow tyre for rolling resistance.

Aerodynamics also favours the narrow tyre for lower drag, but not
at commuting speeds.

John
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  #12  
Old November 9th 11, 12:57 AM posted to aus.bicycle
Theo Bekkers[_2_]
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Posts: 46
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.

"John Henderson" wrote
F Murtz wrote:


What about the fact that the skinny tyre is often run at over 100
PSI
and the fat tyre at 40 PSI


Run the wide tyre at its rated maximum instead of 40 PSI. It'll
be more comfortable, stable and faster than a narrow tyre run at
the same pressure. There are 2"/50mm tyres with 65, 70 and even
85 PSI ratings.

Thare's no doubt that your 40 vs 100 PSI comparison favours the
narrow tyre for rolling resistance.

Aerodynamics also favours the narrow tyre for lower drag, but not
at commuting speeds.


We've had this discussion before and there's no argument that the
rolling resistance of a wide tire and a narrow tire are the same when
both are at the same pressure. However, the narrow tire will
invariably have a higher recommended tire pressure, so when a wide and
a narrow tire are inflated to their recommended pressures, the narrow
tire will have a smaller contact patch and a lower rolling resistance.

The argument that a wide and a narrow tire have the same rolling
resistance is therefore spurious.

Theo


  #13  
Old November 9th 11, 03:07 AM posted to aus.bicycle
TimC[_2_]
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Posts: 46
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.

On 2011-11-09, Theo Bekkers (aka Bruce)
was almost, but not quite, entirely unlike tea:
We've had this discussion before and there's no argument that the
rolling resistance of a wide tire and a narrow tire are the same when
both are at the same pressure. However, the narrow tire will
invariably have a higher recommended tire pressure, so when a wide and


Not quite invariably. I upgraded one of my early bikes by replacing
the stock 45PSI tyres with 80PSI ones. Same dimensions, but heck of a
lot better to ride on! Stupid kmart bikes --- BTH bait.

a narrow tire are inflated to their recommended pressures, the narrow
tire will have a smaller contact patch and a lower rolling resistance.

The argument that a wide and a narrow tire have the same rolling
resistance is therefore spurious.


And for the wider tyre, pumped to the same pressure, because there is
a larger radius, it will take a lower deflection before the wider tyre
ends up with a wider contact patch. I am skeptical that this will
lead to a lower resistance.

--
TimC
I've told them and told them: Temporal anomalies are different from
spatial anomalies. But the kittens know better. They laugh at my
feeble attempts to fool them. -- barbara in ARK
  #14  
Old November 9th 11, 04:36 AM posted to aus.bicycle
John Henderson
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Posts: 413
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.

Theo Bekkers wrote:

We've had this discussion before and there's no argument that the
rolling resistance of a wide tire and a narrow tire are the same when
both are at the same pressure. However, the narrow tire will
invariably have a higher recommended tire pressure, so when a wide and
a narrow tire are inflated to their recommended pressures, the narrow
tire will have a smaller contact patch and a lower rolling resistance.

The argument that a wide and a narrow tire have the same rolling
resistance is therefore spurious.


It's by no means certain that:

1) a narrower tyre will invariably have a higher recommended
maximum pressure, or

2) a narrower tyre will be inflated to a higher pressure.

The argument in favour of wider tyres stands on its merits.

John
  #15  
Old November 9th 11, 05:42 AM posted to aus.bicycle
Rob
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Posts: 107
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.

On 9/11/2011 9:35 AM, John Henderson wrote:
Rob wrote:

Its true wider tyres will have a higher rolling resistance. Even just a
small increase.


That's a myth, and a false one at that. See eg:

http://preview.tinyurl.com/3suok2f

John


It is my experience that I quote, can't help that.

Both the same pressure. my 27" rim bike had a narrow tyre which I
couldn't replace unless I used a wider tyre. The size is think it went
from 3/4 to 1" and it did make a difference.
  #16  
Old November 9th 11, 06:41 AM posted to aus.bicycle
Tomasso[_8_]
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Posts: 33
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.


"John Henderson" wrote in message
...
Theo Bekkers wrote:

We've had this discussion before and there's no argument that the
rolling resistance of a wide tire and a narrow tire are the same when
both are at the same pressure. However, the narrow tire will
invariably have a higher recommended tire pressure, so when a wide and
a narrow tire are inflated to their recommended pressures, the narrow
tire will have a smaller contact patch and a lower rolling resistance.

The argument that a wide and a narrow tire have the same rolling
resistance is therefore spurious.


It's by no means certain that:

1) a narrower tyre will invariably have a higher recommended
maximum pressure, or

2) a narrower tyre will be inflated to a higher pressure.

The argument in favour of wider tyres stands on its merits.

John


You could try 700-18 tyres and a 13 mm rim width, inflated to 160 psi of
Helium.


  #17  
Old November 9th 11, 10:00 AM posted to aus.bicycle
Dave Hughes
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Posts: 228
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.

On Wed, 09 Nov 2011 16:42:01 +1100, Rob wrote:

Both the same pressure. my 27" rim bike had a narrow tyre which I
couldn't replace unless I used a wider tyre. The size is think it went
from 3/4 to 1" and it did make a difference.


There are other factors - trad, construction, thickness, bead and material
- which all contribute to what for want of a better word I'll call a
tyre's "ride". As a general rule, and by no means absolute, wider tyres
are aimed at more casual riders. They're cheaper, so use lower grade
rubber that is less elastic, might have tread that looks good but does
bugger all but absorb energy, and quite probably weigh a truckload more.
All of that contributes to a much slower tyre.

If you can find a high quality 38mm tyre you can chuck 100psi in and have
a pretty good ride that'll be marginally faster than a 23mm tyre of
similar quality and construction at 100psi. This is a good option for the
back wheel of a commuter which tends to be harder to unweight due to
panniers, etc. Maxxis do something in that size, because I've got one on
the back of my commuter right now [1]. Anecdotally, the day I put it on is
the first day I've broken 20 minutes for my commute in both directions in
a single day in ages. That would have nothing to do with traffic lights,
feeling OK, wind, load, or any other conditions, of course.

Narrower tyres are probably quicker up hills by a similar margin as the
fatter tyres are quicker down and along the flats though, due to their
lighter weight. In all cases the difference is going to be 3/5 of bugger
all though!

[1] well, the width is probably a touch greater, and the height a touch
lower at this exact moment. Bloody bogan droppings!

--
Dave Hughes -
We are, in fact, at the cutting edge of cocking about
- Richard Hammond, Top Gear

  #18  
Old November 13th 11, 12:03 PM posted to aus.bicycle
[email protected]
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Posts: 3
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.

John Henderson wrote:
Feeling that a narrow tyre is quicker is so often all in the
mind. Just like all those motorists who swear that their car
runs better after an oil change.


Well... that depends on how long it's been since the oil was last changed.

I can remember performing an oil change where we had to remove the sump and pull globs of grease-like "oil" out by hand, because the owner of the vehicle in question had only ever "topped up".the oil. For 100,000km.


BTH
  #19  
Old November 13th 11, 12:06 PM posted to aus.bicycle
[email protected]
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Posts: 3
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.

TimC wrote:
On 2011-11-09, Theo Bekkers (aka Bruce)
was almost, but not quite, entirely unlike tea:
We've had this discussion before and there's no argument that the
rolling resistance of a wide tire and a narrow tire are the same when
both are at the same pressure. However, the narrow tire will
invariably have a higher recommended tire pressure, so when a wide and


Not quite invariably. I upgraded one of my early bikes by replacing
the stock 45PSI tyres with 80PSI ones. Same dimensions, but heck of a
lot better to ride on! Stupid kmart bikes --- BTH bait.


Oh I agree Tim, kmart bikes ARE rubbish! You have to go to BigW to get a good one! :-)


BTH
  #20  
Old November 13th 11, 11:03 PM posted to aus.bicycle
Tomasso[_8_]
external usenet poster
 
Posts: 33
Default 700/38 vs 700/23 tyres on a "comfort" hybrid commuter bike.


wrote in message
news:[email protected]9...
TimC wrote:
On 2011-11-09, Theo Bekkers (aka Bruce)
was almost, but not quite, entirely unlike tea:
We've had this discussion before and there's no argument that the
rolling resistance of a wide tire and a narrow tire are the same when
both are at the same pressure. However, the narrow tire will
invariably have a higher recommended tire pressure, so when a wide and


Not quite invariably. I upgraded one of my early bikes by replacing
the stock 45PSI tyres with 80PSI ones. Same dimensions, but heck of a
lot better to ride on! Stupid kmart bikes --- BTH bait.


Oh I agree Tim, kmart bikes ARE rubbish! You have to go to BigW to get a
good one! :-)

BTH


But I believe you can still buy 27 inch tyres at K-Mart...

T.


 




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