Ryan Cousineau wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
>
>>Ryan Cousineau wrote:
>>
>>>In article <[email protected]>,
>>> jim beam <[email protected]> wrote:
>>>
>>>
>>>
>>>>Ryan Cousineau wrote:
>>>>
>>>>
>>>>>In article <[email protected]>,
>>>>>"Zix" <[email protected]> wrote:
>>>
>>>
>>>[REI Novara]
>>>
>>>
>>>
>>>>>>I was looking at their Strada racing bike which has an
>>>>>>aluminum frame and Shimano 105 components in 5 places,
>>>>>>and I was curious if anyone had any experience with this
>>>>>>bike. Here is a link:
>>>>>>http://www.rei.com/online/store/ProductDisplay?storeId=8000&catalogId=4000
>>>>>>0008000&productId=47968697&parent_category_rn=4500865
>>>
>>>
>>>>>>Personally I am not sure that an Alu frame is for me,
>>>>>>having experienced for a year the Alu stiffness factor in
>>>>>>my previous bike, but I'm responding to the components
>>>>>>and sale price and trying to be practical.
>>>>>
>>>>>
>>>>>Behold the Approved Standard rbt answer:
>>>
>>>
>>>>>-the feel of "stiffness" is best tuned by adjusting your bike's tire
>>>>>pressure in 5 psi increments. There are only a few exceptions, most
>>>>>notoriously the infamously whippy Vitus 979 frames. The second most
>>>>>important factor in the ride of a bike is probably frame geometry,
>>>>>followed by the type of bar tape you use.
>>>>
>>>>that's parody, right? tire pressure has absolutely ZERO effect on a
>>>>frame's mechanical properties or a wheel's mechanical properties, both
>>>>of which are significant factors in ride quality. it may be ok to joke
>>>>about this stuff once in a while, but it's dangerous here on r.b.t.
>>>>because repetition means people start to believe the most outrageous
>>>>b.s. as "fact".
>>>
>>>
>>>Jim, I hope I'm not misrepresenting others here, but my impression is
>>>that one regular in this newsgroup who makes his living designing and
>>>selling titanium frames (Mark Hickey) and one regular in this newsgroup
>>>who literally wrote the book on bicycle wheels (Jobst Brandt) have both
>>>basically said that given the relative amounts of flex in an inflated
>>>tire (significant by design) and virtually any bike frame or wheel
>>>(magnitudes smaller), the chance of the frame or wheel's "ride quality"
>>>being discernible to any sensible degree is virtually nil.
>>
>>well, i wouldn't call hickey a "designer". he merely parrots anything
>>brandt says, has no interest in data acquisition and doesn't know what
>>modulus is. brandt otoh uses deliberately misleading examples to try to
>>convince either himself or others that he knows what he's talking about.
>> if a bike had /no/ tires, it would still react to loading based on its
>>structure. the fact that loading still ends up being transmitted to the
>>bike via the tires cannot be avoided - a 200lb person sitting on a bike
>>still exerts a 200lb load regardless of tire pressure.
>
>
> Jim, broadly tarring a guy who has a pretty good reputation for building
> Ti frames that work properly and another guy who has spent considerable
> years in engineering and the bike industry is not gaining you debating
> points.
but ryan, nothing personal, but having a frame built in china and
sticking your name on it is no science. and if i sold you a book saying
the earth was flat, would that change the shape of the planet? there
are a number of fundamental engineering errors in brandt's book. i
don't care how long he's been selling/telling his stories - time doesn't
make those errors go away.
>
> The tires flex. Heat is generated. those loads are damped. Sic transit
> gloria mundi. How do you think pneumatic tires work?
how do you think air pressure affects the bike's structure?
>
>
>>>I would treat geometry considerations separately: angles and dimensions
>>>affect how a bike feels in interesting ways, but most bikes exist within
>>>fairly small variations on these parameters.
>>>
>>>I know you disagree, but I judge the "tire-supremacist" arguments as the
>>>most reasonable explanation. My own experience has been that frame
>>>materials are not very important to bike feel, but I would not put
>>>myself forward as an expert.
>>>
>>
>>i don't know much about tires either, but i know a bit about materials
>>and their application, and i can say with certainty that the structural
>>attributes of a bike are /not/ affected by tire pressure. and it's the
>>structural attributes that affect the way a bike reacts to you riding it.
>
>
> Frames flex. But not that much unless you've built a Rinard beam bike.
> The diamond frame design has pretty much evolved because it's the
> stiffest, lightest structure that will fit a human body and two wheels
> (and because the UCI has deemed further evolutions improper...).
>
> I would really like to see a blind test of a steel vs. al or Ti frame,
> where they had the same geometry, but if there are any differences a
> rider can feel between the steel and aluminum frames, we can fix that
> with tire pressure, different bar tape, and a new seat.
>
> To get an idea of how much frame materials matter to feel, or damping,
> or whatever, note that both the most notoriously flexy frame (I nominate
> the Vitus 979) and the most notoriously stiff frames (choose your
> favourite year of Cannondale) are made of aluminum.
ok, this is not a test. if you want to specify all tubes be of the
exact same dimensions, anyone could tell the differences because the
modulus of those materials is so different. but once we allow the
dimensions of those tubes to change, all bets are off. i have two
aluminum frames. with the same pair of wheels/tires/air pressure, one
will jolt you till your teeth rattle, the other is so comfy, it's like
grandma's sofa. now, do you want to discuss materials again?
>
> Frame material is a specification of a bicycle that I think most buyers
> should not stress about:
we agree.
> it may be determined by other factors, most
> notably a desire for, oh, extreme light weight or the ability to carry a
> frame repair kit with you on the road or the ability to stick magnets to
> your frame. But attributing special damping properties to frame
> materials without regard for frame design, especially given the much
> more important contributions to "ride" and "feel" made by things like
> wheelbase and tire size and pressure, is not reasonable.
>
eh? who mentioned "damping properties"? metal frames/wheels don't do
that - they essentially have no hysteresis loop. and we haven't yet
discussed carbon composites, which /do/ attenuate force transmission
depending on rate of application, but that's a whole different debate.
getting back to the original point, we agree, tires affect the magnitude
of road force transmission to the structure, but where we don't seem to
agree is recognition of the fact that once this road force has been
transmitted /to/ the structure by the tire, the way the structure reacts
to that force will entirely determine "feel".
this recognition is like brandt's bogus argument about "deflection is
equivalent to riding over a sheet of paper". now, a purely radial load
does indeed deflect a rim in that order of magnitude. but, that
deflection is irrespective of tire pressure. and deflection requires
the application of force. would anyone seriously argue they can't feel
the force necessary to deflect a rim that much? they should; it's over
100 lbs.