response 50 of 103:

May 31 04:02 UTC 2002

Huh.  Guess I've never seen a *good* set of side-pull brakes...the ones 
I've seen never worked worth anything.  What's the advantage over 
center-pull?

response 52 of 103:

May 31 06:14 UTC 2002

Shoes are very important.
They comes in all kinds of qualities.
Generally cheap ones are wasted within a couple fo moths (intensive 
use, as I do). Expensive ones last for years and their grip is tighter.
Those are the kinds of brake shoes I use for mountain biking (5,000 ft 
and higher)

response 54 of 103:

May 31 06:38 UTC 2002

Coaster brakes still appear on children's bikes.

response 56 of 103:

May 31 14:39 UTC 2002

I think discs have a major advantage in wet conditions.  They're farther
from the road, so they don't get as wet.  Rim brakes are just about useless
when wet, as I'm sure everyone's noticed.  I think on very steep descents
there's also the possibility of rim brakes heating up the rim enough to blow
the tire, but I've never heard of that actually happening.

response 58 of 103:

May 31 18:21 UTC 2002

The handle bars drew is talking about are not the same "ram horn" 
handle bars other people are talking about.  They are more like 
"antelope horn" handle bars than "ram horn".  They were breifly in 
fashion while I was a kid, they were modeled on "chopper" motorcycles.  
I think we may have called the bicycles "chopper bikes" as kids.  They 
faded away fast because they had significant safety issues.

Once upon a time I read a lot about bicycle physics.  Let's see if I 
remember any.

The curvature of the fork is only a small part things.  Here's a kind
                                  of bad diagram of the front of the
               ()))))             bike frame.  AB is the axle around
                   ||A            which the fork rotates when you
         //=========\\            steer.  Extend that line till it
        // \\      //\\B___       hits the ground and that's point C.
       //   \\    // ,\\   `.     X is the point where the tire
      //     \\  // /  \\    \    touchs the road.  X is always behind
    (_)=======\\// (   (_)    )   C on any bicycle.  What this means
                    \        /    is that if you lean the bike left
                     `-____-'     the the steering wheel will magically
                         X  C     pivot left, causing the bike to turn
                                  left if it is moving, bringing the
wheels back under the bike and bringing it upright again.  So this 
makes the bike naturally stable.  It also makes it possible to ride 
no-handed, because leaning translates into turning.  So the XC distance 
is the factor that effects the stability of the bike.  Notice that if 
the fork is angled, as in the diagram, then a straight fork works fine.  
A curved fork factors into this too.  I think if XC was zero or 
negative, it would be a very unpleasant bike to ride.

Note that if you welded the steering on a bicycle in the straight-ahead 
position, you wouldn't be able to ride it, even in a straight line.  It 
would be just as hard as balancing a stationary bicycle (some people 
can do this, but they actually go backward and forward little bits, 
they aren't stationary).  You don't keep a bicycle upright by 
balancing, and it isn't the gyroscopic force of the wheels keeping you 
upright either.  It's the process described in the previous paragraph - 
as the bike leans, you steer the wheels back under it.  The bike is 
built to do this naturally, and learning to ride a bike is largely 
about learning to assist in this process instead of fighting it.  So 
not bicycle ever travels in an exact straight line.  They are always 
swerving back and forth to keep the wheels under the rider.  The slower 
you go, the more pronounced this action is, because you have to steer 
more to get the wheels under you fast enough.  If you ride really slow, 
you zig-zag back and forth a lot.

It interests me how easy it is to ride a bike without knowing anything 
about how a bike works.

response 60 of 103:

May 31 18:38 UTC 2002

Jim asks if anyone has tried using a notched rubber belt instead of a chain.
Can someone link this to the transportation conference?

We saw some old bikes that used metal gears on rods instead of chains.  They
were much more expensive to build but did not need the chain replaced.  It
might have been tricky to switch gears that way.

Jim says rubber does not rust and should have a comparable transmission loss
(torque) to chains.  

response 62 of 103:

May 31 20:43 UTC 2002

I'm not certain, but I think motorcycle drive belts actually last longer than
chains because although they wear, they dont stretch the way chains do,
because of their inherent resiliency.

response 64 of 103:

May 31 22:41 UTC 2002

Chains stretch not because the material stretches (it's steel, it
doesn't stretch), but because the wear removes material which enables
the links to move farther apart so that the chain grows in length.
Motorcycle (and bicycle) chain drives wear out because they're open
chain drives, collect dirt, and lose oil.  Enclosed oil bath chain
drives last much longer.  The original motorcycles (ca. 1900) used
leather belt drives; these were quickly replaced by longer lasting open
chain drives.  Modern motorcycles (ca. 2000) are now returning to belt
drive, because modern synthetics last a lot longer than leather or open
chain.  Also, when a belt drive breaks, it's a lot less dangerous than
when a chain breaks.

response 66 of 103:

Jun 1 00:51 UTC 2002

I'm still amused by the insistance here that side-pull brakes are cheap and
don't adjust well.  What are you basing this on, an encounter with a cheap
side-pull brake that didn't adjust well once?  Do you consider the Shimano
Dura-Ace and Campagnolo Record brakes to be cheap brakes that don't hold their
adjustment well?  They're the top of the line brakes from the major component
manufacturers, and sell for more than $200 a set.  What definition of "cheap"
are you using?  What would you call expensive?

response 68 of 103:

Jun 1 14:08 UTC 2002

Re #63:  To shift sprockets, you need to have the chain moving.  This
is done with a free-wheeling clutch (an overrunning clutch); some
bikes even move the freewheel to the pedal side in order to allow
shifts while the pedals aren't moving.  Shifting sprockets requires
a mechanism to take up the slack in the chain, which is a large part
of the derailleur mechanism.  A coaster brake requires a chain that's
taut on both sides and a way to transmit backwards torque to the
hub, which is defeated by the freewheel and the derailleur.

If you wanted to install a hub brake and activate it with a separate
cable, you could adopt a mechanism from a moped or similar vehicle.
Some of those have cable-actuated drum brakes, but they're heavy.

response 70 of 103:

Jun 1 21:15 UTC 2002

Our Schwinn 3-speeds (non-derailleur type) have two types of rear hub, a push
and a pull (with chain) type.  Two different brands of hub.

Today John and John drove over in the truck with new tires.  Little John
pointed out to me that the sidewalls of my tires were cracked and I might want
to get new ones, and he had fun looking around Jim's junk collection.  We
promised to save him a few things to take apart (electronic).  Jim pointed
out that the trail-a-bike was attached to the seatpost without enough of a
sleeve (it was fitted too loosely) so he added a bigger sleeve and the rear
bike is a lot less likely to lean now and the whole contraption is more
stable.  The bike shop put it on too loosely, it seems.

I pointed out that the extra-wide seat John had bought for comfort was the
cause of his riding discomfort as it was for upright position and he was
riding with handlebars level with the seat, so we replaced it with a road-bike
type seat.  Also raised the seat so that the distance from top of pedal to
top of seat is the 110% of the distance from ground to crotch (measuring
astride a broom).  We did the same for John III but he preferred to be lower
so he could get his feet on the ground so we lowered it back.  Jim showed the
Johns how to oil the rear brake (John III did the oiling).  We biked to lunch
and back (through the woods on a dirt trail).  Next time we may bike along
the river to Fuller Pool.  John III pedals really fast down hills.

response 72 of 103:

Jun 2 16:46 UTC 2002

Jim and I stopped by K-Mart later and found that they sell three models of
gel-type saddle with nylon (non-waterproof) cover that seem really comfortable
- the big wide variety (good for upright riding or exercise bikes), the medium
type that we provided to John (ours had not much padding) and a narrower type
with a cutout in the middle which seems to be designed to put less pressure
on men's 'soft tissue'.  Does this saddle actually function as promised or
is it an advertising gimmick?  The Nashbar catalog offered something similar
for women which I cannot figure out any purpose for since my bottom is lowest
at the sit bones, not between them.  

All the handlebar grips that they had were sticky rubber with a variety of
bumps.  I prefer smooth rubber without bumps for riding on normal roads.  What
are other people's preferences?  My favorite grips are wider across the top,
offering a ledge to rest my weight on, and are smooth enough to let me switch
my position frequently without sticking.  Do people with sweaty hands like
the sticky models?  I also cannot stand the foam ones (scratch) or the ones
with many narrow ridges (sharp).

response 74 of 103:

Jun 2 20:51 UTC 2002

If they are difficult to remove, try sticking something long and narrow under
one end and squirting in some soapy water to lubricate them.  It will dry up
after you do the switch.