Largest tire size on a Mavic Open pro rim?
Bike Camano
Once again I come to this vast pool of knowledge in seek of answers. I'm
putting together a TREK 520 and the only 36h wheel I have is a Mavic Open Pro.
How big of a tire can I put on that?
Also, anyone have a favorite touring tire recommendation? I plan to build up a
T217 rim (or ?) once my finances allow.
Thanks again!
-Mo Miller
Riding Beautiful Camano Island, WA, USA
http://ourworld.cs.com/homesofquality/bikecamano/index.htm
Mike Jacoubowsky
narrow at the base that you might get rim cuts etc from the angle the tire
exits the rim). For tires, the Conti Top Touring are very tough.
--Mike-- Chain Reaction Bicycles
http://www.ChainReactionBicycles.com
"Bike Camano" <bikec...@cs.com> wrote in message
news:20001025230718...@ng-cc1.news.cs.com...
Wayne Lim
rim, it's not much wider and they often run 2+ inch (50+ mm) tires.
There may be some slight differences in the hook bead profile between
road and MTB rims, but I tried prying off my 38c tire when I had about
30 PSI in it and couldn't get it off, so I felt pretty confident about
it staying on when I had 75 PSI in it.
Wayne Lim
In article <20001025230718...@ng-cc1.news.cs.com>,
Sent via Deja.com http://www.deja.com/
Before you buy.
Mike Jacoubowsky
the rim, and possibly the fact that the profile's going to be a bit screwy.
Where is Jobst? I'm sure he'd be able to tell us why, or even if, a wider
tire needs a wider rim for any particular reason.
Of course, the original super-light mountain bike rims were simply road rims
that guys like Keith Bontrager cut down and re-pinned to a smaller diameter.
So maybe I should go ask Keith....
--Mike-- Chain Reaction Bicycles
http://www.ChainReactionBicycles.com
"Wayne Lim" <wl...@my-deja.com> wrote in message
news:8t8lcd$sgl$1...@nnrp1.deja.com...
> I've used a 700X38c with no problems. If you look at a mountain bike
> rim, it's not much wider and they often run 2+ inch (50+ mm) tires.
> There may be some slight differences in the hook bead profile between
> road and MTB rims, but I tried prying off my 38c tire when I had about
> 30 PSI in it and couldn't get it off, so I felt pretty confident about
> it staying on when I had 75 PSI in it.
>
> Wayne Lim
>
> In article <20001025230718...@ng-cc1.news.cs.com>,
> bikec...@cs.com (Bike Camano) wrote:
B.C. Cletta
"...Mavic Open Pro. How big of a tire can I put on that?"
i've tried both 43-mm (BG Happe-whatevers) & 45-mm (Panasonic
Smokes). it work (sorta, the tire rolled around on the rim, no
sidewall stability, so the ride was spooky.)
Tony Szurly
mm tires for the T519 and T221
Mike Jacoubowsky
due to sidewall strength vs the tire. A bigger tire with the same air
pressure as a smaller tire exerts much greater force on the rims, making a
sidewall failure more likely. (But don't ask me for the math to prove it
etc...it's been done many, many times by people pretty good at this stuff,
and I'm out of my league trying to explain it myself).
Of course, wider tires typically have lower pressure ratings than skinny
tires, so it's possible that either the overall sidewall force is relatively
constant. As I said, I'm out of my league here.
--Mike-- Chain Reaction Bicycles
http://www.ChainReactionBicycles.com
"Tony Szurly" <szu...@rcn.com> wrote in message
news:39F8A375...@rcn.com...
HajajŽ
wrote:
>Hello,
>Once again I come to this vast pool of knowledge in seek of answers. I'm
>putting together a TREK 520 and the only 36h wheel I have is a Mavic Open Pro.
>How big of a tire can I put on that?
>
>Also, anyone have a favorite touring tire recommendation? I plan to build up a
>T217 rim (or ?) once my finances allow.
>
Panaracer Everride 700x32c on a Mavic CXP-30 works fine for
me. Wore out a rim without any trouble with the tire.
HajajŽ
ha...@worldonline.dk
I do not have diplomatic immunity
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Damon Rinard
of tire minor diameter and rim width is:
F(h) = p/2 * sqrt(d^2 - w^2) .
where
F(h) is the horizontal component of the tensile force per unit
circumferential length,
d is the minor diameter of the tire, and
w is the width of the rim between hooks.
You can see that a wider tire at the same pressure increases the force
on a given rim by a large amount (the d^2 term). The difference is
approximately the same as the difference in the recommended tire
pressures on tires of different widths that are otherwise the same.
In article <ZN2K5.9649$NP.7...@news.flash.net>,
--
Damon Rinard: dri...@yahoo.com
Bicycle Tech Site:
http://www.damonrinard.com/
Mike Jacoubowsky
physics behind such questions as this and rotational weight and whether
aerodynamics matter etc. Or maybe it should be a place that people meet for
drinks? Non-alcoholic, of course.
--Mike-- Chain Reaction Bicycles
http://www.ChainReactionBicycles.com
"Damon Rinard" <da...@damonrinard.com> wrote in message
news:8tb0cr$q4o$1...@nnrp1.deja.com...
James Thomson
> The horizontal force per unit circumferential rim length as
> a function of tire minor diameter and rim width is:
> F(h) = p/2 * sqrt(d^2 - w^2) .
[snip]
Could you give a brief derivation of this? I think I see the
geometrical source of the expression (Pythagoras on a right triangle
of hypoteneuse d/2, side w/2).
James Thomson
Wayne Lim
does what hit the rim?
The profile of the tire casing will still be almost entirely round for
the portion of the tire that is above the rim, so tread thickness will
determine how out of round the tire appears to be. It will have more
curvature than when mounted to a wider rim, but I've never noticed that
this causes any effects I can detect.
Wayne Lim
In article <QGXJ5.9418$NP.7...@news.flash.net>,
Damon Rinard
"James Thomson" <Sna...@jcet.freeserve.co.uk> wrote:
> "Damon Rinard" <da...@damonrinard.com> wrote:
>
> > The horizontal force per unit circumferential rim length as
> > a function of tire minor diameter and rim width is:
>
> > F(h) = p/2 * sqrt(d^2 - w^2) .
>
> geometrical source of the expression (Pythagoras on a right triangle
> of hypoteneuse d/2, side w/2).
>
> James Thomson
A road tire may be approximated as a cylindrical pressure vessel. The
tire casing is the wall of the cylinder. Pressure in a cylinder causes
both circumferential and axial stress in the cylinder walls. In a
bicycle tire, it is the circumferential stress that tends to pull the
rim side walls apart. Circumferential stress is calculated according to
the formula for cicumferential stresses in a cylindrical pressure
vessel [from Mechanics of Materials, by Gere & Timoshenko]:
sigma = (pr) / t
where
sigma is the circumferential stress in the wall,
p is the pressure,
r is the cylinder's radius (or the tire's minor radius), and
t is the thickness of the cylinder's wall (or of the tire casing).
Multiplying both sides by t gives the tensile force on the tire casing
per unit circumferential length of the tire:
F = pr
This is the tensile force in the tire casing due to internal inflation
pressure. A component of this force tends to pull the rim side walls
apart. The component of this force depends on the angle of the tire
casing as it leaves the rim, and consequently depends on the geometry
of the tire and rim, namely the interior width of the rim and the minor
diameter of the tire. The horizontal component of this force is what
we're after.
See http://damonrinard.com/images/tensile_pressuregeom.gif
To find the horizontal force as a function of tire and rim geometry and
pressure, solve for F(h). Using like triangles, recognize that the blue
triangle is like the red one:
F(h)/pr=a/r , so F(h)=pra/r or
F(h)=pa , equation [1] .
F(h) is desired and p is known, so a is the only unknown. To find a use
the Pythagorean theorem to say
a^2 + (w/2)^2 = r^2 .
Solving for a and recognizing that the radius is half the diameter gives
a = sqrt{(d/2)^2 - (w/2)^2} .
Substituting a into equation [1] above and simplifying gives the
horizontal force per unit circumferential length as a function of tire
minor diameter and rim width:
F(h) = p/2 * sqrt(d^2 - w^2) .
where
F(h) is the horizontal component of the tensile force per unit
circumferential length,
d is the minor diameter of the tire, and
w is the width of the rim between hooks.
So for a given pressure, larger diameter tires (larger d) and narrower
rims (smaller w) create higher forces on the rim. This is powerful
information: knowing the tire and rim dimensions and the pressure in
the tire allows us to calculate the horizontal force tending to pull
the rim side walls apart, per unit length.
For example, a typical 20 mm wide tire inflated to 8 kg/cm^2 (118 psi)
mounted on a typical rim of about 13 mm inner width exerts a force of
6.1 kg on every centimeter of the rim's circumference (13.4 pounds per
inch). But simply changing to a 23 mm wide tire (with every other
variable the same) increases the force on the rim from 6.1 to 7.6
kg/cm, a 25% increase! To match the rim force of the 20 mm tire, the 23
mm tire would have to be inflated to a lower pressure: 6.4 kg/cm^2 or
94 psi.