Tire Rotation

deep
a gradient lies
in the forest
no. be seriuos.
your excess to custom cycles dimmed ypur perceptions here dude!
while we folk wrestle with rear bias all you big sky lbs types are
running
mid weight low(or is that hi) polar moment custom frames.
into the trees!!
and lets not hear any bs on gary nixon

installed by...off course they can, or we can maybe! hollow pedal
shaft!
the deal is the gradient and the larch forest. the rubber next to the
carcass
is not the rubber you wanna run on the road
nor was it designed to be.
not only is a continuous effectiveness expensive
but unneccesary as most will get used to or forget about it
and remember only the zippy first grip period.
reminds me of a good new baked fresh red potato with hollandaise

Kovie wrote:
Question: even if a flat profile on the rear tire isn't a safety issue, at
what point does it become a performance issue, if at all, in terms of
cornering ability, rolling resistance, etc.?

Any article links on this?

I don't have any links, but I recall reading somewhere that the
flattening caused by wear should increase the rolling resistance
slightly... but I'm not sure why... something to do with the shape of
the contact patch. Thinner rubber would tend to decrease the rolling
resistance.

As far as cornering goes, there should be some effect there too since
you'd be riding on a ridge rather than a nice smooth profile. That is a
very good reason not to put a flattened tire on the front, I think.

Sheldon's reasoning seems pretty sound... you certainly want the front
tire to be in good shape, and if you are using the same tires front and
back, it's easy to keep a fresh one on the front.

-Ron

wrote in message
...
On Wed, 10 Aug 2005 21:55:56 GMT, "Kovie"
wrote:

"Sheldon Brown" wrote in message
...
Tom Nakashima wrote:

I recently purchased two new tires to replace my old tires which have
developed a flat profile after approximately 4000 miles. I also have
been rotating the tires from front to rear every 500 miles to prolong
the
profile (keeping it round) as the rear wears faster than the front.
I've
also been making sure the tires have been properly inflated. There
have
been articles about rotating a tire from front to rear may not be a
good
idea for safety reasons.

Right, see: http://sheldonbrown.com/tire-rotation

It seems to me if you don't rotate the tires what you'll have is a very
flat profile on the rear

That's not a problem in practice.

and not getting best mileage out of the tires.

The mileage issue would only apply if you were to replace _pairs_ of
tires. My recommendation is to replace tires one at a time, putting the
new one on the front and moving the old front one to the rear.

With this approach, you'll get the maximum wear life out of your tires,
while having the safety benefit of always having the newer tire on the
front.

Sheldon "Front To Back, Not Back To Front" Brown

Question: even if a flat profile on the rear tire isn't a safety issue, at
what point does it become a performance issue, if at all, in terms of
cornering ability, rolling resistance, etc.?

Any article links on this?

Dear Kovie,

Some pros believe that the tubulars have a rounder profile
than clinchers and that they can feel this difference as
they lean over in a corner and then lean back up.

In terms of rolling resistance, the more material removed
from the original tire, the less there is to squash, just as
an ultralight thin inner tube should have less rolling
resistance than a thick thorn-resistant tube.

Weigh the new tire, weigh it again when it's worn, and we'd
have a better idea of what's involved.

It's likely that this is a princess-and-the-pea matter, in
which people are going to "feel" an advantage or problem
according to their pre-conceptions. One test would be if a
rider could tell the difference between normal, thick, and
thin inner tubes installed by someone else.

Carl Fogel

Perhaps I used the wrong term (it's been a while since I took high school
physics), but by "rolling resistance" I meant the frictional resistance
encountered between tire and road when the bike is in motion. The flatter
the tire, the more contact area there is between both surfaces and thus the
more there is to "push" while pedaling. Obviously, you want some surface
contact or else you won't have traction, but from what I understand, the
more surface are in contact, the higher this resistance.

I think you're referring to the inertial resistance of a body at rest to
being put in motion, in this case rotationally. The heavier the wheel,
whether due to a heavier rim, spokes, tube, tires, etc., the greater this
resistance, making acceleration harder. I believe this is why racers prefer
lighter wheels (except in certain situations such as time trials, in which,
I think, too-light wheels are bad, because they tend to lose rotational
momentum faster than heavier wheels, but I may be wrong about this). In any
case, I believe that the two resistances are different, but I may have used
the wrong terms here.

--
Kovie
zen

It has been suggested than one of the reasons Continental produced
their "Attack & Force" combination (different front and rear tires) was
really to prevent tire rotation as opposed to producing a performance
benefit.

On 11 Aug 2005 01:47:20 -0700, "Rik O'Shea"
wrote:

It has been suggested than one of the reasons Continental produced
their "Attack & Force" combination (different front and rear tires) was
really to prevent tire rotation as opposed to producing a performance
benefit.

Nice anonymous dig on the company. Way to go.

JT

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Tom Nakashima wrote:

I recently purchased two new tires to replace my old tires which have
developed a flat profile after approximately 4000 miles. I also have
been rotating the tires from front to rear every 500 miles to prolong
the profile (keeping it round) as the rear wears faster than the front.
I've also been making sure the tires have been properly inflated.
There have been articles about rotating a tire from front to rear may
not be a good idea for safety reasons.


"Kovie" wrote in message
k.net...
Question: even if a flat profile on the rear tire isn't a safety issue, at
what point does it become a performance issue, if at all, in terms of
cornering ability, rolling resistance, etc.?
Any article links on this?
Kovie
zen

I don't have a link either or even tired to search for one. My results are
based on actual riding.
Let me try to clear this up:
After pilling on the miles, my tires had developed a square profile from the
original round radius, which is slightly more pronounced on the rear. I've
heard when this happens, it's time to change tires, as it could be
dangerous to ride on this profile on the front....and there is also a slight
performance loss, which the experts call "rolling resistance".
I've been riding the same weekday training ride just about everyday for the
last 9 years, so I know the road well and speed checks along the whole
route. There's one section on the descent that I gauge as my maximum speed
of 33-35mph before the tire change. When I put on the new tires (yes I
purchased 2 and the same size and brand, same air pressure) with the
rounded profile my speed increased to 39-41 mph on the descent....averaged
checked over 10 rides as I reset my cyclometer before I begin each ride.
On the flats my speeds have increased 1 to 2 mph, but on the climbs I see no
difference in speed.
In cornering ability, the bike feels the same.

About that test rolling resistance test, I have a few questions:
1. Are the results the same after the profile of the tires starts to
change?
a. perhaps a check of the rolling resistance right out of the box, then
at 500 miles, again at 1000 miles, and once more at 2000 miles.
2. The test only applies to flat roads and descents and not ascents?
a. I feel no difference in rolling resistance on the ascents and if it
is there, it's ever so slight.
-tom

"Kovie" wrote in message

Question: even if a flat profile on the rear tire isn't a safety issue, at
what point does it become a performance issue, if at all, in terms of
cornering ability, rolling resistance, etc.?

Tom Nakashima wrote:

After pilling on the miles, my tires had developed a square profile from the
original round radius, which is slightly more pronounced on the rear. I've
heard when this happens, it's time to change tires, as it could be
dangerous to ride on this profile on the front....and there is also a slight
performance loss, which the experts call "rolling resistance".

I'm not convinced of this. I would expect worn tires to have _less_
rolling resistance, because as they get thinner they get more flexible.

The reason for replacing worn tires is that the thinnest part becomes so
thin that it takes a smaller and smaller sliver of glass or whatever to
poke through to the tube, so you start getting more flats.

I've been riding the same weekday training ride just about everyday for the
last 9 years, so I know the road well and speed checks along the whole
route. There's one section on the descent that I gauge as my maximum speed
of 33-35mph before the tire change. When I put on the new tires (yes I
purchased 2 and the same size and brand, same air pressure) with the
rounded profile my speed increased to 39-41 mph on the descent....averaged
checked over 10 rides as I reset my cyclometer before I begin each ride.
On the flats my speeds have increased 1 to 2 mph, but on the climbs I see no
difference in speed.

I can't believe that this is due to the use of new vs old tires.

Rolling resistance is such a small percentage of total retarding force,
especially at high speeds like that that even if you installed totally
frictionless tires I don't believe it would give you half a mph of speed
improvement. I think there's some placebo effect involved here.

Sheldon "Skeptic" Brown
+-----------------------------------------+
| Well, the truth is usually just |
| an excuse for a lack of imagination... |
| --Garak, DS-9 |
+-----------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

"Kovie" wrote:

Perhaps I used the wrong term (it's been a while since I took high school
physics), but by "rolling resistance" I meant the frictional resistance
encountered between tire and road when the bike is in motion.

Right, that's what we all mean by the term. I don't recall this being
covered in my high school physics class, but that was a looooong time ago.

The flatter
the tire, the more contact area there is between both surfaces and thus the
more there is to "push" while pedaling. Obviously, you want some surface
contact or else you won't have traction, but from what I understand, the
more surface are in contact, the higher this resistance.

Not exactly. The contact area is mainly determined by the air pressure
in the tire and the weight load on that wheel.

Rolling resistance comes from the hystertic losses involved in bending
the tire from its round shape to the flat shape the part incontact with
the road has. The thicker the rubber, the stiffer the tire and the more
energe is requried to re-shape the tire as the contact patch rolls along.

With modern road tires, properly inflated, rolling resistance is so low
as to be virtually insignificant compared with aerodynamic friction
except at very low speeds.

Sheldon "Rolling Resistance" Brown
+-----------------------------------------+
| The wind and waves are always on the |
| side of the ablest navigators. |
| --Edward Gibbon |
+-----------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

"Sheldon Brown" wrote in message
...
"Kovie" wrote:

Perhaps I used the wrong term (it's been a while since I took high school
physics), but by "rolling resistance" I meant the frictional resistance
encountered between tire and road when the bike is in motion.

Right, that's what we all mean by the term. I don't recall this being
covered in my high school physics class, but that was a looooong time ago.

Well, it was AP physics (mock condescensing emphasis on "was" ;-) ), but it
was a pretty long time ago for me, too. I think it was covered under
mechanics, specifically energy and friction. Glad to see that my memory
hasn't completely failed me...yet.

The flatter the tire, the more contact area there is between both
surfaces and thus the more there is to "push" while pedaling. Obviously,
you want some surface contact or else you won't have traction, but from
what I understand, the more surface are in contact, the higher this
resistance.

Not exactly. The contact area is mainly determined by the air pressure in
the tire and the weight load on that wheel.

Rolling resistance comes from the hystertic losses involved in bending the
tire from its round shape to the flat shape the part incontact with the
road has. The thicker the rubber, the stiffer the tire and the more
energe is requried to re-shape the tire as the contact patch rolls along.


Not sure this is what I was taught, but again it was a while ago. ;-)

With modern road tires, properly inflated, rolling resistance is so low as
to be virtually insignificant compared with aerodynamic friction except at
very low speeds.

Sheldon "Rolling Resistance" Brown

I seem to recall that there were at least 4 different kinds of friction
involved here. One, the static friction between tire and road--the "good"
friction, because it provides necessary traction. Two, the rolling
resistance discussed here. Three, the air resistance as the bike/tire move
forward (trainers need not be concerned about this one). And four, the air
resistance as the tire rotates. And I imagine that each of the latter two
also has a "turbulence" component that becomes more pronounced as speed
increases. So I can see how rolling resistance is just a part of a much more
complex picture, and a small one at that. Now if I can only find my old
physics textbook...

--
Kovie
zen