Conference noted::bicycle

	Did you adjust seat height before you checked for knee-over-
	pedal-spindle?  The two settings will interact.

	Here is some data from USENET:

Path: decwrl!...!ohio-state.edu!husc6!uwvax!speedy!shekita
Subject: fitting a bike
Posted: 30 Mar 88 22:06:27 GMT
 
Frame Size
----------
Guimard recommends using a frame that is .65 of your inseam length.  Note that 
this is for a frame measured center of seat lug to center of bottom bracket. 

In this measurement, inseam length is taken standing up, facing a wall, on a 
hard floor, shoes off, socks on, feet together, with riding shorts on. 
(Got all that!) Insert a hardcover book between your legs and bring it up 
firmly against your crotch, squaring off its edge against the wall. The 
book is simulating your bicycle seat so press it against your crotch pretty 
hard. (Whoa, don't get carried away!) The place where the top edge of
the book binder meets the wall is what you should use to measure your inseam. 
 
If you can't get the exact sized frame, always try to fit into a smaller 
frame before going to a larger one.  
 
Seat Height
-----------
According to Guimard, seat height should be set at .883 of your inseam,
where seat height is measured from the center of the bottom bracket to the 
lowest point on the center line of the seat.  Guimard warns against changing 
your seat height more than .6 cm (1/4") at a time; too drastic a change could 
lead to injury. 
 
If you have Look style pedals, tack on another 3mm to the seat height;
the pedal cleats are thicker than most.
 
Seat Fore and Aft Positioning
-----------------------------
As far as fore and aft positioning goes, Guimard follows the school of 
thought that says the seat should be positioned so that the tip of your 
kneecap is in line with the center of the pedal axle when the crank arms 
are horizontal. This can be varied slightly depending on the type of riding
-- back a little for more power and less spin, forward a little for more spin.
The measurement can be made by running a plum line from the bump under your 
knee to your pedal axle. You'll need a friend to check that your cranks
are horizontal. If you don't have a plum line, then just tape a string to 
the tip of a pencil that is sharpened at both ends. 
 
Incidently, note that this differs from the school of thought that says that 
your pedal axle should line up with that little bump under kneecap. I
personally believe that Guimard's method causes less strain on your knees.
Although I may be wrong, I think that low seat height and seats that are 
too far forward, are to blame for a lot of sore knees out there. If
you don't believe me, try walking down some stairs and contrast 1) a fairly 
deep knee bend with weight far forward, verses 2) a slight knee bend and 
less weight forward.
 

    re .0	Another possibility is the season.  You may have just
    started road riding again after indoor training, running, or whatever
    for the winter.  This could just be a spring time  "use"  pain,
    only you can figure that out.  We often get selectively stronger
    in the off season and some of that strength can cause real
    problems in the bicycling specific and now relatively weaker, areas.

    	Reg
    

    Your knee pain is probably caused by your cleats being out of
    adjustment.  This is a major cause of knee pain in riders.  I
    suggest that if you walk with a canter(sp?) you adjust your pedal 
    the oppisite direction of your canter.  The adjustment should be 
    in small increments and then try riding.  If the pain persists,
    get off the bike and adjust them more.  You will be surprised how
    once you get them adjusted correctly the pain will stop getting worse
    and will disappear.
    
    On your fore/aft seat adjustment.  I have always gone by the bone/bump
    under the knee cap should be plumb with the center of the pedal axel.
    This adjustment has always been a rough adjustment depending on the
    type of riding you do.  A crit rider will position their seats more 
    forward and a road racer will position their seat a little more back.
    This is to accomodate the spinning of a crit racer and the leverage
    needed for a road racer for climbing.  Usually if you can't position
    the seat to the neutral position it means the frame is too small for
    you.  Make sure when you take this measurement that your cranks are
    parellel with the floor. 
    
    Seat hight is a matter of your spinning technique.  If you ankle alot
    when you spin that you seat will need to be higher than whatever rule
    of thumb you use  suggests.
    
    What I am trying to say is that no rule is perfect for bicycle fit.
    Your bicycle fit depends on you and your style of riding, spinning,
    leg proportion, etc.  You also cannot fit your bike by yourself.
    I suggest a professional fit.  By professional fit I do not mean some
    chart like the Fit Kit.  Find someone who knows what they are doing.
    
    Good luck!!
    
    don
    

    
    
    	Sounds like you should try RAD, Rotational Adjustment something
    I was at Cat I in Tyngsboro when Paul Randazzo was doing a RAD to
    a customer. He did all the adjusting that was covered in this notes
    file, then he has you take a 10 mile ride to see how it feels. He
    keeps adjusting until its right. When my Marinoni comes in I will
    sure do it, buy the way, it costs $30.
    
    	Joe

    
    OK, there's one thing I'm missing here.  As I see it the seat fore/aft
    position is more related to the seat tube angle than the size of
    the frame!  Right now I have a 54 cm frame. If I had a 56 cm frame
    it would have the same seat tube angel, the seat post would be lower
    and I still wouldn't be able to adjust the seat..  Am I right???
    
    Stew
    

> As I see it the seat fore/aft position is more related to the seat tube 
> angle than the size of the frame!  Right now I have a 54 cm frame. If I 
> had a 56 cm frame it would have the same seat tube angle, the seat post 
> would be lower and I still wouldn't be able to adjust the seat..  
> Am I right???

	Correct.  As long as the seat tube angle and crank length remain
	the same, the seat will not change fore-aft adjustment for different 
	sizes of frame.  The crank, your calf, your thigh and the seat
	height adjustment form a quadrilateral where all four sides
	and one of the angles (the seat tube angle) is fixed.  Shortening
	the seat tube requires lengthening the seat post by the same
	ammount (to maintain adjustment) so nothing moves.

	Tilting	the seat tube more upright will move your knee forward so
	you would have to move your seat back to get you knee over
	the pedal spindle again.

	One thing that WILL change is the top tube length...  If you
	get a frame that is too small and just put in a long seatpost
	and stem (stem long in height, not extension) you may end up
	banging  your knees against the handlebars.

	The Fit-Kit measuring system will recommend a seat tube angle
	for each recommended frame size.

    If the seat angle remains the same and the size of the bike changes,
    your fore/aft position will also change.  The reason being as you
    increase bike size, the seat tube gets longer.  This means it is
    pulling you away from the front of the bike more.  Therefore if you
    keep the seat tube angle the same and increase the frame size, you have
    to adjust your seat more aft.
    
    don
    

< Note 607.8 by KOALA::PICARD >

>    If the seat angle remains the same and the size of the bike changes,
>    your fore/aft position will also change.  The reason being as you
>    increase bike size, the seat tube gets longer.  This means it is
>    pulling you away from the front of the bike more.  Therefore if you
>    keep the seat tube angle the same and increase the frame size, you have
>    to adjust your seat more aft.
    
	Not really because to make the larger frame fit you, you must lower
the seat till it gets to your proper height therfore eliminating the
distance gained.
    

    
    So, frame size really becomes a ball park figure then.  I now ride
    a 54, and buy jacking the seat post up, and putting on a longer
    stem I have made a bike that would seem to be too small for me
    fit me.  
    
    Does anyone know if for a given manufacturer if the seat tube angle
    changes as the frame size changes?  If it does then I'd agree that
    frame size is important when fitting a bike.  If it doesn't then
    it seems you can change enough about the bike to make a smaller
    frame fit!   
    
    Stew
    

< Note 607.10 by NACAD::CAMPBELL >
                                -< Frame size? >-
    
>    Does anyone know if for a given manufacturer if the seat tube angle
>    changes as the frame size changes?  If it does then I'd agree that
    
I'm always looking for frame geometry specs across the range of frame sizes 
when I look at bikes, because the angles do change, esp as the frame gets 
smaller.  If the angles remained the same as the frame got smaller, you'd 
ultimately have a problem the your toe and the front tire interfering with 
each other when you turn.  Not a good situation.  The CPSC (Consumer Product 
Safety Commission) actually has laws governing such things.  So when the frame 
gets smaller than about 52cm, the head tube angle gets shallower, and 
sometimes the seat tube gets steeper.  Don't know why the seat tube would get 
steeper, but on some bikes it does.  I'm not sure if anything changes as frame 
size increases.  In general, I think frames are designed for some 'normal' 
size, probably around 56cm, and then the design is changed if necessary at 
both ends of the size spectrum.

I ride a 50-52cm frame, which is why I've always looked carefully at this.

Kevin

>If the angles remained the same as the frame got smaller, you'd 
>ultimately have a problem the your toe and the front tire interfering with 
>each other when you turn.  Not a good situation.  
    
    I rode a 4 or 5 year old Bianchi, about a 52cm that did exactly
    that.  The front wheel actually hit the pedal cage about two inches
    back behind my big toe.  You have to turn pretty far to create the
    contact though.  Didn't bother me at all, actually, I had a good
    race on it.
    
    So it does happen, and the bike we're talking about is a Bianchi...

>    So, frame size really becomes a ball park figure.  I now ride
>    a 54, and by jacking the seat post up, and putting on a longer
>    stem I have made a [too small] bike fit me.  

	We have shown that the frame size (length of seat tube) does
	not affect the seat fore/aft adjustment.  What DOES change
	is the position of the head tube relative to the seat...

	If you use a smaller frame and just extend the seat post and
	stem, the handlebars will be closer to the seat.  If you try
	to compensate by getting a stem with a longer extension, the
	handlebars will be at the right distance but they will still
	pivot further back then normal.

	The bottom line is that you can't vary the frame without
	something going out-of-whack.

    It's fashionable today to have a small, "tight" frame, with long
    seatpost and stem extensions, but I wonder sometimes if riders 
    are giving up something there.  All your weight sitting on six
    inches of angled, unsupported seatpost (with only 2" insertion in the
    seat tube) can't be stiffer than the same weight atop 2" of 
    unsupported seatpost, with 6" insertion in the seat tube.  The
    proximity of the top tube and chain stays to the weight the bike
    supports ought to make the second setup stronger, no?
    
    MATT

    re .14	No.	The frame itself gets whippy, there isn't (shouldn't
    be) a whole heckuva lot of bending forces on the seat post and its
    junction with the seat tube.  OTOH (on the other hand, there's always
    another one) the frame's main triangle (OK it's a quad, we know)
    gets a lot of bending and twisting forces in a sprint or out of
    the saddle hill climb when there's not much for the seatpost to
    do.  Hence the trend toward smallest frame that fits vs the fashion
    a few years ago, which seemed inherited from parental buying during
    childhood, "You'll grow into it Lennie".  The geometry works out
    pretty well, i.e. raise the seat either by having a longer seat
    tube or by having the seat post further out of it, either way you
    only do this for a long legged rider and if their upper/lower leg
    proportions are anywhere in the normal range the knee will come
    pretty much over the pedal spindle at 3 o'clock, use saddle fore/aft
    adjustment to get it "perfect", though preferences come into it too.
    Oh yeah, 29 inches * Tan (coupla degrees)  ~=~  not much.

    	What probably matters more and it paid less attention to is
    the seat_tube/top_tube ratio and its relationship to
    upper_body/lower_body proportions.  If you know your legs are
    relatively long for your height, look for a top tube that is an
    inch or two (OK, 2 - 5 cm) less than the seat tube, supposedly most
    women are proportioned this way, though my experiences with long
    legged wo<oops, > conversely for relatively short legged people.
    Deficiencies here can't be accomodated with stem length without
    affecting handling.  Having said that I can't remember the  "Optimum"
    ratio for stem/top_tube length, but supposedly there is one and
    the bike gets twitchy on fast decents if its wrong in one direction
    and wanders on climbs if its wrong in the other direction.

    	Reg	{Oh yeah, sure, I design frames too, in addition to
    			my beautiful job here}
    

    I don't get it, then; why don't road frame designers take a hint
    from the mountain bike makers and use a sloping top tube and 
    a foot-long seatpost?   That would tighten up those triangles...

    re .16	It would also help to tighten up the rear triangle too,
    i.e. shorter seat stays.  Butcha can't tell 'em, they just won't
    listen.  Besides, tradition sez the top tube has to be parallel to
    the ground coz that's how the original designs were done by people
    whose geometry was ~, and that was before CAD tools, and lug
    sets (I know, they don't HAVE TO use them, but traditi<etc.> ) only
    come in a few angles with not much opportunity to play around more
    than a degree or two.  Until fairly recently foot long (or 300 mill,
    doesn't THAT sound lonnnnnggggg ?) seat pins weren't available.
    Anyway, it has to sell....
    
	R
    

    
    Last night I went to Category 1 to get fit kitted.  According to
    the Fit kit I should be riding a 59 cm frame.  You may recall that
    from previous notes the one I'm riding is a 54 cm.  A small problem
    Also, My seat was much too low!  I had just raised it and thought
    that it was too high due to some bouncing when I rode.  Paul said
    that the bouncing was due to my lousy technique and not to the seat
    height.  Naturally I disagreed so we raised the seat on another
    bike ( My seatpost wouldn't go up high enough) and what a difference!
    I felt alot more stretched out and my stroke clean up a little....
    
    So I stand corrected!!  Frame size does matter!  I also take back
    all the things I have been thinking about the fit kit.  I like the
    way it "would" setup a bike for me.  That brings me to my next point.
    
    I now have a Bianchi Trofeo (Campy super record comps) with a
    54 cm frame that is useless to me.  Anyone out there want to buy
    it????   Make me an offer.....  I may not refuse......
    
    Thanks for the replies.....
    Stew

    
    Oh, by the way....  I meant to say does anyone want to buy the frame.
    Not the whole bike.  I'd like to keep the comps....
    
    S
    

    RE:  .18
    
    	I had a similar experience when I first got fit kitted, and
    had some knee problems until my body adjusted.  My fit kit didn't
    change the frame size by 5cm either!
    	You may not want to change your seat height so radically in
    one jump.  Instead, try changing the seat height in smaller 
    increments as your body adjusts until you get to the fit 
    kit/desired height.
    
    /Nick