Mavic x221 Tire size help

Discussion in 'UK and Europe' started by Tom, Aug 29, 2004.

  1. Tom

    Tom Guest

    Hello all,

    I had a wheel built for me with a Mavic x221 rim at my lbs. I had
    specified that it was to run a 559 x 1.9 tire but now I've got it home and
    had a good look at it, I can't believe that a 17mm rim would be able to keep
    a 1.9" (48mm) tire on properly.

    Would someone please reassure me that everything will be fine as I can't
    get back to the shop until next Saturday and I hate to be bikeless.

    Thanks

    Tom
     
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  2. Peter B

    Peter B Guest

    "Tom" <[email protected]> wrote in message
    news:[email protected]
    > I had a wheel built for me with a Mavic x221 rim at my lbs. I had
    > specified that it was to run a 559 x 1.9 tire but now I've got it home and
    > had a good look at it, I can't believe that a 17mm rim would be able to

    keep
    > a 1.9" (48mm) tire on properly.
    >
    > Would someone please reassure me that everything will be fine as I can't
    > get back to the shop until next Saturday and I hate to be bikeless.


    Rest assured, I've used everything from 1.25" Pasela road tyres to 2.1"
    knobblies on 221's.

    Pete
     
  3. davek

    davek Guest

    Peter B wrote:
    > Rest assured, I've used everything from 1.25" Pasela road tyres to 2.1"
    > knobblies on 221's.


    Perhaps you'll know the answer to this: why do so many mountain bikes
    have these ultra-narrow rims with hugely fat tyres? OK, you /can/ run a
    fat tyre on a narrow rim, but surely a fatter rim would be more appropriate?

    d.
     
  4. Peter B

    Peter B Guest

    "davek" <[email protected]> wrote in message
    news:[email protected]
    >> Perhaps you'll know the answer to this: why do so many mountain bikes

    > have these ultra-narrow rims with hugely fat tyres? OK, you /can/ run a
    > fat tyre on a narrow rim, but surely a fatter rim would be more

    appropriate?

    In a nutshell: weight!
    The narrowish 32 hole rims I have nearly always used for many moons (about
    144 IIRC) have proved up to the job bouncing down boulders, steps,
    gawd-knows-what etc whilst carrying my 80kg (more with a loaded 3litre
    Camelbak), what problem would making the rim wider solve?

    Rgds,
    Pete
     
  5. davek

    davek Guest

    Peter B wrote:
    > In a nutshell: weight!


    Should have guessed!

    > what problem would making the rim wider solve?


    I guess I assumed that wider rims would be stronger (assuming comparable
    quality of build/materials) which might be an issue for mountain bikes.
    And like the OP I also assumed that a tyre could be too wide for a rim
    and be at risk of coming off.

    I don't object to having my illusions on this subject shattered.

    d.
     
  6. Simon Brooke

    Simon Brooke Guest

    in message <[email protected]>, Peter B
    ('[email protected]') wrote:

    >
    > "davek" <[email protected]> wrote in message
    > news:[email protected]
    >>> Perhaps you'll know the answer to this: why do so many mountain
    >>> bikes

    >> have these ultra-narrow rims with hugely fat tyres? OK, you /can/ run
    >> a fat tyre on a narrow rim, but surely a fatter rim would be more

    > appropriate?
    >
    > In a nutshell: weight!
    > The narrowish 32 hole rims I have nearly always used for many moons
    > (about
    > 144 IIRC) have proved up to the job bouncing down boulders, steps,
    > gawd-knows-what etc whilst carrying my 80kg (more with a loaded 3litre
    > Camelbak), what problem would making the rim wider solve?


    FWIW my Cannondale came with rims which look remarkably narrow to me,
    but they've caused no problems. If Cannondale choose to put narrow rims
    on a fairly high-end mountain bike I'm prepared to believe they have a
    reason, and that there won't be problems (although I didn't think much
    of their choice of ultra-lightweight, ultra-puncturable tyres).

    --
    [email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/

    ;; killing [afghan|iraqi] civilians is not 'justice'
     
  7. Mark South

    Mark South Guest

    "Peter B" <[email protected]> wrote in message
    news:[email protected]
    >
    > "davek" <[email protected]> wrote in message
    > news:[email protected]
    > >> Perhaps you'll know the answer to this: why do so many mountain bikes

    > > have these ultra-narrow rims with hugely fat tyres? OK, you /can/ run a
    > > fat tyre on a narrow rim, but surely a fatter rim would be more

    > appropriate?
    >
    > In a nutshell: weight!
    > The narrowish 32 hole rims I have nearly always used for many moons (about
    > 144 IIRC) have proved up to the job bouncing down boulders, steps,
    > gawd-knows-what etc whilst carrying my 80kg (more with a loaded 3litre
    > Camelbak), what problem would making the rim wider solve?


    It would create problems. A wider rim would have less protection accorded it by
    excess tyre width, and would suffer more sidewall damage offroad.

    Of course, the weight thing is a big factor in ATBing.
    --
    Mark South, Super Genius: World Citizen, Net Denizen
     
  8. Pete Biggs

    Pete Biggs Guest

    Peter B wrote:

    > what problem would making the rim wider solve?


    I'm not sure I agree with it but here is Sheldon Brown's view:

    "If you use a very wide tire on a narrow rim, you risk sidewall or rim
    failure. This combination causes very sloppy handling at low speeds.
    Unfortunately, current mountain-bike fashion pushes the edge of this. In
    the interest of weight saving, most current mountain bikes have
    excessively narrow rims. Such narrow rims work very poorly with wide
    tires, unless the tires are overinflated...but that defeats the purpose of
    wide tires, and puts undue stress on the rim sidewalls."
    - www.sheldonbrown.com/tire-sizing.html

    and from rec.bicycles.tech:
    --------------------------------------
    Imagine two similar tires,
    one of which is 2 inches wide from bead to bead, the other 4 inches.
    We'll suppose them to be inflated to the same pressure, lets say 100
    psi, though this wouldn't be appropriate in practice.

    Imagine a 1 inch length of tire/rim. The section of tire fabric in this
    length is 2 square inches for the narrow tire, 4 square inches for the
    wide one. Thus, at 100 psi, the narrow tire is withstanding 200 pounds
    of force, while the wider tire will be withstanding 400 pounds. This
    represents the difference in "hoop stress" between them.

    As a practical matter, tire width varies more than rim width, so narrow
    tires tend to assume more of a "U" profile, while wider tires tend to
    assume a profile like a capital omega. The narrow tire pulls up nearly
    straight outward from the bead, since the rim is nearly as wide as the
    tire.

    The wider tire, on a similar rim, will bulge out, so, where it contacts
    the edge of the rim, there's a strong sideways component to the force.
    This places a high stress on the cords that are in contact with the rim
    edge (also a high spreading stress on the rim.) Normal working of the
    tire as you ride can cause the cords to rub against the rim and be
    abraded by it. This is a common failure mode of wide tires. Using
    thicker cords helps resist this sort of damage.

    Sheldon "Does That Help Clarify?" Brown
    --------------------------------------

    ~PB
     
  9. Tom

    Tom Guest

    "Peter B" <[email protected]> wrote in message
    news:[email protected]
    >
    > Rest assured, I've used everything from 1.25" Pasela road tyres to 2.1"
    > knobblies on 221's.
    >
    >


    Thanks Pete,

    I've fitted the tyre and had a little test ride and everything seems to
    be ok. Still looks weird though.

    Tom
     
  10. Peter B

    Peter B Guest

    "Pete Biggs" <pblackcherry{remove_fruit}@biggs.tc> wrote in message
    news:[email protected]
    > Peter B wrote:
    >
    > > what problem would making the rim wider solve?

    >
    > I'm not sure I agree with it but here is Sheldon Brown's view:


    <snipped>

    Well I'm a great admirer of Sheldon but......
    In practice I've never heard of, let alone witnessed an mtb rim bursting for
    any reason other than the sidewalls being worn away by rim brakes, based on
    Sheldons argument a wider rim may delay this failure mode whearas disc
    brakes will prevent it. And as it happens without much warning I'd sooner
    prevent it.
    Regarding the narrower rim altering the tyre footprint due to the "U"ness of
    the tyre: this is something that struck when I first started using narrower
    rims in the days when Panaracer Smokes were state-of-the-art. Because the
    Smokes were superior to the tyres I previously used the benefit of them
    would have masked any detriment caused by the narrower rim. I'd also
    assume, perhaps incorrectly, that high performance tyres are designed to be
    used with high performance rims which by default are narrow.
    Regarding sidewall wear and tear and bead abrasion again IME performance mtb
    tyres are scrapped because the tread is worn, the sidewall damaged by trail
    debris or simply because the rider is a fashion victim. Mtbers paying circa
    25 quid for a tyre that lasts perhaps a year are no more bothered by this
    overhead than roadies whose tyres manage 2000 miles (and I fall into both
    camps).

    Regards,
    Pete
     
  11. "Peter B" <[email protected]> wrote:

    > In practice I've never heard of, let alone witnessed an mtb rim
    > bursting for any reason other than the sidewalls being worn
    > away by rim brakes, based on Sheldons argument a wider
    > rim may delay this failure mode whearas disc brakes will
    > prevent it. And as it happens without much warning I'd sooner
    > prevent it.


    Rim failure isn't always instant: the rim walls may begin to crack or splay
    long before any separation takes place. Disk brakes certainly solve the
    problem of rim wear, but to disk-equip a diskless bike might cost several
    hundred pounds.

    > I'd also assume, perhaps incorrectly, that high performance tyres are
    > designed to be used with high performance rims which by default are
    > narrow.


    There are a lot of broad, high-performance rims on the market, assuming
    you're not limiting your definition of performance to XC racing. The Sun
    Rhyno Lite is one example, and the trend is toward both broader rims and
    broader tyres. A Nokian Gazzaloddi tyre and a Snowcat rim are both
    high-performance (if extreme) products in their fields.

    That many people use fairly broad tyres on narrow XC rims shows that this
    isn't a big problem, but broader tyres handle much better at lower
    pressures on broader rims.

    James Thomson
     
  12. Peter B

    Peter B Guest

    "James Thomson" <[email protected]> wrote in message
    news:[email protected]
    > There are a lot of broad, high-performance rims on the market, assuming
    > you're not limiting your definition of performance to XC racing.


    I must admit I was for two reasons:
    1) I based my comments on my own experience of long trail rides, often quite
    rugged (Peaks, Lakes, Welsh purpose built trails, enduros etc) and to a
    lesser extent XC racing which to me is a refinement of the former.
    2) Outside of the above I have little knowledge but assume weight isn't a
    factor for downhilling and certain types of playbikes designed for getting
    air-time etc.so yes, I can't see a detriment with wider rims and those bikes
    generally have even wider tyres than XC racing and trail bikes.

    Pete
     
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