On 11/29/2020 6:16 PM, Mark J. wrote:
On 11/29/2020 12:27 PM, Frank Krygowski wrote:
On 11/29/2020 1:03 PM, Tom Kunich wrote:
On Sunday, November 29, 2020 at 8:51:59 AM UTC-8, AMuzi wrote:
On 11/29/2020 10:28 AM, Frank Krygowski wrote:
On 11/29/2020 10:28 AM, Duane wrote:
N8N wrote:
Good afternoon all,

was just cleaning up when I picked up my bike helmet and
one of the
plastic bits just cracked in my hand. Guess it's time
for a new one;
especially when I look at it and see a 2008 manufacture
date (do as I say
not as I do.) Pretty sure it's a Trek "Vapor".

What to buy? It's not like I can just run down to my LBS
and start
trying them on, although if I knew what I wanted, I'm
sure I could get it
from them to toss them a little bit of business, but it's
all curbside
pickup and by appointment now.

Would like something well ventilated as I'm a damnyankee
living south of
the Mason-Dixon, so most of the year it's warmer already
than I'd prefer.
Affordable is a plus.

thanks for any advice.



First advice is “duck!â€

Second is if the helmet that you had lasted 12 years and
you can’t try new
ones, maybe the same model?

Vaguely related: When should you replace your helmet?
https://www.yahoo.com/news/really-re...110001066.html


It's interesting that the only bit of the article alluding
to relevant data says this:

"... you don’t necessarily need to replace a well cared
for helmet for safety reasons alone, according to Swart.
That recommendation is largely based on research conducted
by engineering firm MEA Forensic, which found in tests of
hundreds of helmets that age did not significantly affect
the performance of the protective foam in helmets up to 26
years old."

And yet the article gives much more ink to "every five years."

(P.S. My cycling caps are holding up very well for much
longer than that.)

I don't know anything about age degradation and impact
resistance in helmets.

But plastics to indeed outgas and also degrade under UV[1]
such that while the manufacturer's "3 to 5 year" life may be
overly cautious, ten years is about it for buckles, visors etc.

Compare to vintage machines (bicycles in particular but cars
& motorcycles too) which may look fine and have
smooth-feeling bearings but the lubricants are shot and will
self-destruct in short order. Bicycle hubs do that as well
as classic car rear gear sets when run, after 40, 50, 60
years, without sufficient lubrication.

[1] and, I assume, other factors besides

A friend has a Trek Madone that appeared to get water into the BB90
and impact the rollers. He never directly washed it with a hose and
he never had it out in the rain. The seals appeared to be intact but
the rust was over the entire bearing surfaces.

Changing temperatures can cause nearly-enclosed spaces like bottom
bracket to expel air, then inhale air; and with it, moisture. I wonder
if that could have been the mechanism at work in his case.


If the Madone is anything like my Domane, the BB is *far* from nearly
airtight.Â* The FD cable exits the frame under the BB, and there's plenty
of "breathing space" around it to avert any pressure differential.

When I said a nearly enclosed space, I didn't mean to imply it's almost
airtight. That isn't required for the problem to occur. All that's
really required is a suitable volume of air enclosed and a suitable
temperature difference. The presence of liquid water at a suitable inlet
hole helps a lot, but isn't absolutely necessary if temperatures, etc.
are right.

If the bike (or other air container) is warm, the air inside it will be
warm. When that inside air cools it contracts and sucks in outside air.
If there's a drop of water it can inhale, it will do that. Once inside,
it's hard for that water to evaporate.

Even without liquid water, under some conditions the contracting inside
air can inhale humid outside air. That humidity can condense on cool
inner surfaces. Again, that liquid can have a hard time evaporating and
leaving through a small hole.

When we added a balcony to our house, I designed and welded up the
ornamental steel rails. I forgot to leave weep holes in the 1" square
vertical corner posts. In a few years they had accumulated water several
inches deep, which froze and bulged the bottom of the posts. The caps on
those posts were not airtight, but they did overhang the top, so rain
didn't drip in. The water was inhaled.

--
- Frank Krygowski