Conference noted::bicycle

	Stiffness is a function of material, tube diameter and tube
	wall thickness.  Maybe you can get your main frame tubes
	made with iron pipe (as in plumbing).  If you don't mind the
	weight you could have a frame stiffer than anything available
	off-the-shelf (except perhaps a K-mart Huffy...)

	Seriously, Serotta Cycles builds bikes with a proprietary
	tubing that flares at the bottom bracket to give stiffness
	where it counts.  See "Cycle Guide" (July 87?) magazine's 
	article on the 7-11 team bikes.  Any racing team bikes you 
	see with Huffy or Muray labels are probably built by Ben 
	Serotta... look for the Serotta "S" logo engraved in the 
	rear brake bridge.

Stiffness of the overall bike is also due in part to frame geometry, lugs,
and how many coats of paint (<=== scratch that last ...). I don't care
whose tubes you use, if you use 65 deg. frame angles, it's going to ride
like an IHOP pancake. Frame height is important too, with taller frames like
mine sort of waving in the breeze ....
                                                    ken

    
    The biggest factor in frame stiffness is THE BUILDER!
    
    Proper mitering, choice of lugs, fit of lugs/tubes, quality of brazed
    joints....these are the most important factors. A water pipe frame
    brazed with viods and matched to lugs with .020 clearances will
    be as loose as a Huffy LaGrande.
    
    Given a high quality build, the hot tubing these days is Tange
    Prestige. It's a new alloy (for bike tubes anyway) that is extremely
    strong, so that the wall thickness is very thin, like 753 but stiffer.
    
    CdH
    

    When I crank my pedals, with the bike turned over or on a stand, the
    bike does a dance (pulsates) all over the place. Assuming my bike
    is balanced and the wheels are true, etc., is this caused by frame
    flexing?
    
    					Russ  

    I'm not sure what you mean that the bike is balanced, but true wheels
    aren't necessarily balanced.
    
    True only means that the rim is in the right place.  If the tire,
    innertube, spokes and rim do not have homogeneous density, then the
    wheel may not be balanced even when true. 
    
    Of course, the VALVE STEM is the biggest non-homogeneity in the tube!
    If the bearings are good and you spin the front wheel very slowly, and
    watch it slow to a stop, it may rotate back and forth until it stops
    with the valve stem at the bottom.   NOT BALANCED, but weights may be
    added to the high side. 

    Anybody got any recommendations?
    
    Because of the freewheel, the rear wheel can't be checked this way
    unless the chain is removed.
    
    Note that if the wheels are BALANCED, their rotation will generate no
    force to flex the frame.  If the wheels are not balanced, and the bike
    bounces, that may be due to the seat or bike stand flexing. 
    
    If I ever add a reflector to a wheel, I add it to the light (high) side
    to try to keep it as balanced as possible.
    
    Hope this is what you asked for.
    
    Glen
    
    PS - ever ride or drive a car whose wheels needed balancing?

    re: -.1, On some extremely light but cheap rims, it's not the valve
    stem but the rim joint becausee the joint needs a minimal strength.
    I saw this on some Matrix ISO's.  The rim joint was 10 grams heavier
    than the corresponding opposite side of the rim -- found by taping
    two nickles to the opposite side of the rim with the wheel (no tire)
    in a truing stand.  After a tire was installed, the whole wheel
    was very nearly balanced, about 2 grams heavier on the rim joint
    side.
    
    ed

    re .5 & .6
    
    	> Anybody got any recommendations ?
    
    	This isn't exactly a recommendation, but if you want wheels
    that are balanced as well as true, here's  a way of going about
    it.
    
    	The weld opposite the valve stem more or less balances the weight
    of the valve, if the wheel is true then it will be close to being
    balanced anyway, unless you have lollipops (red, orange or white
    reflectors, as recommended by CPSC and others) stuck in your spokes,
    if you like these then get two per wheel so they more or less balance
    each other.  Spin the wheel in a trueing stand, or the upturned
    frame, and note where it comes to rest, repeat a few times to see
    if it is consistent, if not then you may already have a perfectly
    balanced wheel (GOTO .END), or a dragging hub (GOTO MAINTENANCE.OTHER).
    Having found the heavy side of the wheel (bottom, when it comes
    to rest from a slow spin) add a couple of turns of thin solder to
    the highest spoke (spoke h), if this isn't enough then do the same to the
    next spoke (lets call this h + 1), if its still not enough then
    add some to (h - 1).  The wheel/tyre combination is pretty bad if
    you need to go to (h + 2) and (h - 2), thats 5 spokes, usually the
    balance point changes by that time.
    
	I used to do this, I havn't done it for a long time, only you
    can judge if its worth your while, currently I have better uses
    for *MY* time.  It seemed to be most worthwhile when I was riding
    on cheap tubulars a *LOOOONNNGGG* time ago, I had the time, the solder
    and very little money.  I still don't have much money, have less
    time, don't use much solder, but probably ride better tyres.
    
    	Reg
    
	(Oh, don't worry about the solder flying off at 100 + KMpH due
    to centrifugal or other forces)
    

    What I'm looking for is answers about when you know you have frame
    flexing. I thought the pulsating was the frame flexing after I cranked
    it and the pedals weren't moving! Is this wrong? 
    
    					Russ

> When I crank my pedals, with the bike turned over or on a stand, the bike 
> does a dance (pulsates) all over the place. Assuming my bike is balanced 
> and the wheels are true, etc., is this caused by frame flexing?

	No.  It means that your rear wheel is not balanced (most likely)
	or your rear wheel bearings are bad (unlikely unless they also
	rattle or don't turn smoothly).

	It is not a problem of frame flex because the only force
	being placed on the frame to flex it would have to come from 
	an out of balance wheel.  A frame will not flex unless there 
	is a force (such as hard pedaling) acting on it.  A perfectly 
	balanced spinning wheel applies no force to the frame.

	To see a frame flex, stand it on it's tires and lean it away
	from you.  Put one foot on the bottom bracket and push.