Re: lots of noob questions

[NYC XYZ]

Mike Jacoubowsky wrote:
>
>
> Unfortunately, a brand new bike is just as likely to get a flat as one
> that's been on the road for a long time. But did you find what caused it?
> Those are pretty tough tires... check to see if there are two adjacent
> holes, an indication of a "snake bite" flat, typically caused by hitting
> something hard, or hitting something not quite so hard with too-low
> pressure, or some combination in-between. Tire pressure is your friend. Get
> a floor pump with gauge and get religious about keeping tire pressure where
> it should be (I believe the range is 70-90psi for your tires).

I've never had any luck with air pressure gauges. Right now I have a
nice still-new Topeak Joe Blow floor pump with a built-in pressure
gauge and the dial-arm never moves unless I'm pumping -- the tube could
be at 100 PSI, but upon connection the gauge remains at zero unless I
pump some more. I'm almost tempted to see if I'll blow the tube up
pumping to 100 PSI on the gauge when it's already 100 PSI to begin
with! Wonder what happens?

> Presta valves have been around for ages. You have to remove the valve cap
> (which, when lost, is no big deal), unscrew the valve (unscrew it as far as
> it will go; it won't fall off), then attach the pump and inflate it. This
> *should* have been demonstrated at the store, but there's a tendency to
> forget that not everyone is up on such things. If you purchased it from
> Bicycle Habitat in NYC, make sure to tell Charlie, the owner, that Mike from
> Chain Reaction wanted you to give him a bad time about that!

Are Presta valves better somehow? 'Cause they're les convenient! I've
got to tote around an adapter which, luckily, doubles as a sort of
valve cap (not that Presta valves need them, right?), though it's a
slight struggle using it.

> Depends upon what's causing the flats, but if you've got durable tires,
> extra liners are probably overkill.

I'm getting Schwalbe Marathon Pluses with rim tape, too!

> That's probably something easily dealt with in a couple of minutes. If you
> bring it back into the shop, they'll probably take care of it right away.

I've got to learn how to deal with mechanical disc brakes doing
that...or do they? So annoying...but, then again, I hear that
mechanical disc brakes typically make metallic grinding or squeaking
sounds when in use.

> 90 weight oil would certainly work, but it will also attract about 90 pounds
> of crud. There are many good lubes out there; I favor Rock N Roll, but just
> about anything will work. I'm not a fan of the wax-type lubes though; seems
> like they either gunk things up or don't have much staying power.

So you don't recommend teflon-based lubes?

> Actually Treks DO come with an owner's manual, on CD-ROM. And it's not all
> that bad.

When did they start doing this? I just got a nice Trek 1000c
"hybrid-comfort" bike in September and I didn't get no CD-ROM. (Then
again, I hate my LBS...the only LBSes I've had decent experiences with
[and I've yet to have a "good" one, never mind "excellent!"] are the
chains like Metro...I've stepped into a few which seem like they'd be
good shops, though -- basically, the more upscale, the more intelligent
and sympathetic the service...in NYC, anyway, IMHO/IME.)

> You might see if the shop offers any sort of maintenance or basic-care
> classes. Many do. Lots of on-line info too, as others have pointed out.

Time's Up! offers weekly or biweekly basic bike repair classes. They
even have all-female ones lead by female mechanics!

> --Mike-- Chain Reaction Bicycles
> www.ChainReactionBicycles.com

 

[Dave Gittins]

A small tip for Presta valves. To inflate the tyre,
unscrew the locknut. Then give the stem a little tap to make sure it works
freely. Then attach your pump connection. These valves tend to stick.

--
Dave Gittins

Author of Titanic: Monument & Warning
http://users.senet.com.au/~gittins/Book.html

 

[NYC XYZ]

Dave Gittins wrote:
> A small tip for Presta valves. To inflate the tyre,
> unscrew the locknut. Then give the stem a little tap to make sure it works
> freely. Then attach your pump connection. These valves tend to stick.
>
> --
> Dave Gittins
>
> Author of Titanic: Monument & Warning
> http://users.senet.com.au/~gittins/Book.html



Thanks for the tip. But I know how to inflate Presta valved-tubes. =)
I just don't know why the dial-arm of the air pressure gauge doesn't
immediately jump to, say, 100 psi.

 

[Leo Lichtman]

"NYC XYZ" wrote: (clip) I just don't know why the dial-arm of the air
pressure gauge doesn't immediately jump to, say, 100 psi.
^^^^^^^^^^^^^^^
You have 100 psi inside the tube, and 0 (atmospheric pressure) outside. You
have zero in the hose and pump, as well. When you attach the hose to the
stem, the check valve inside the stem is still closed, so no pressure goes
to the pump and gauge. When you start pumping, you build up pressure which
shows on the gauge.

This is good, because it allows you to connect without losing air from the
tube.

 

[NYC XYZ]

Leo Lichtman wrote:
>
> You have 100 psi inside the tube, and 0 (atmospheric pressure) outside. You
> have zero in the hose and pump, as well. When you attach the hose to the
> stem, the check valve inside the stem is still closed, so no pressure goes
> to the pump and gauge. When you start pumping, you build up pressure which
> shows on the gauge.
>
> This is good, because it allows you to connect without losing air from the
> tube.

It seems I have a different conception of what that air pressure gauge
does and/or how it acts...the gauge measures air pressure in the
tube...I hook it to the tube, and flick that little "lock" which opens
up the pump to the tube...so why is the gauge still at zero? How come
when I start pumping it starts from zero, despite the air already in
the tube?

Sorry, but I'm not getting the physics of it yet....

 

[[email protected]]

That "lock" doesn't open the valve between the tube and the pump. It
just seals the pump head to the valve. Presta valves operate solely on
air pressure. You've got to increase pressure in the pump (and hose)
until it's the same as the pressure inside the tube. Once the pressure
in the pump exceeds that in the tube, the valve opens and admits air
until the pressures in the tube and pump are equal. Then, as the pump
slowly leaks down, the valve closes because the pressure in the tube is
greater than that in the pump.

When you remove the head from a presta valve tube, the air you hear
escaping is exclusively in the pump--not the tube. Removing the pump
head from a schraeder-valve tube imperfectly causes air to leak from
the tube through the valve, which is a bad thing.
The fact that presta-valve tubes do not lose air as the pump head is
removed is one of their great advangages over schraeder-valve tubes.
The max pressure you see on the pump is the pressure you get in the
tube, which is not often the case with a schraeder-valve tube.

Schraeder valves operate mechanically and are indeed open the whole
time the pump head is attached.

Does that clarify things?

Jason

 

[Paul O]

NYC XYZ wrote:
<snip>
>
> I've never had any luck with air pressure gauges. Right now I have a
> nice still-new Topeak Joe Blow floor pump with a built-in pressure
> gauge and the dial-arm never moves unless I'm pumping -- the tube could
> be at 100 PSI, but upon connection the gauge remains at zero unless I
> pump some more. I'm almost tempted to see if I'll blow the tube up
> pumping to 100 PSI on the gauge when it's already 100 PSI to begin
> with! Wonder what happens?
>
<snip>

> Are Presta valves better somehow? 'Cause they're les convenient! I've
> got to tote around an adapter which, luckily, doubles as a sort of
> valve cap (not that Presta valves need them, right?), though it's a
> slight struggle using it.
>
<snip>

NYC-
You can probably throw your adapter caps away because most newer bicycle
pumps have convertible heads that can be configured to attach to either
Presta or Schraeder valves.

Most Topeak pumps come with what they call a "SmartHead" that automatic
adjusts to both Presta and Schraeder valves. Read the instructions that
came with the pump.

Good Luck,
paul d oosterhout
from SAIC

 

[NYC XYZ]

[email protected] wrote:
> That "lock" doesn't open the valve between the tube and the pump. It
> just seals the pump head to the valve. Presta valves operate solely on
> air pressure. You've got to increase pressure in the pump (and hose)
> until it's the same as the pressure inside the tube. Once the pressure
> in the pump exceeds that in the tube, the valve opens and admits air
> until the pressures in the tube and pump are equal. Then, as the pump
> slowly leaks down, the valve closes because the pressure in the tube is
> greater than that in the pump.
>
> When you remove the head from a presta valve tube, the air you hear
> escaping is exclusively in the pump--not the tube. Removing the pump
> head from a schraeder-valve tube imperfectly causes air to leak from
> the tube through the valve, which is a bad thing.
> The fact that presta-valve tubes do not lose air as the pump head is
> removed is one of their great advangages over schraeder-valve tubes.
> The max pressure you see on the pump is the pressure you get in the
> tube, which is not often the case with a schraeder-valve tube.
>
> Schraeder valves operate mechanically and are indeed open the whole
> time the pump head is attached.
>
> Does that clarify things?
>
> Jason


It certainly does! So that's what I saw -- a Schraeder valve in
action! That's what I'd seen when the pressure gauge jumped on my pump
-- it was a Schraeder valve!

Thanks a bunch...now, time for Spring Break!

 

[Hank Wirtz]

Here's a tip- switch to long-stem tubes. like they sell for deep aero
rims.. When you have a longer stem, it can bottom out on the back of
the pump head, and will give you the instant reading you want. That
will release a small amount of air from the tube, but will give you the
baseline you want.