Op dinsdag 18 mei 2021 om 10:37:14 UTC+2 schreef Ade:
On 18/05/2021 02:23, Frank Krygowski wrote:
On 5/17/2021 2:53 PM, Ade wrote:

Making bikes light is one thing, making them last is another.

My last allow bike was a Specialised Allez. The frame was light
enough, about 1.5KG (3 lbs in old speak). I weighed it when I stripped
it for return, it had cracked due to fatigue. It was a thing of
beauty, much nicer than the horrid oversized carbon frame they
replaced it with.

My previous alloy Trek failed at about the same distance, ~10,000 miles.

I thought the benefit of titanium was that like steel it had a fatigue
limit, meaning it wouldn't inevitably eventually fatigue like
aluminium. I know aluminium bikes can be made so the fatigue failure
takes a long time, but I suspect this adds weight.

Well, as we've mentioned, steel and titanium alloys can and do fail by
fatigue - specifically, when a local stress exceeds the fatigue limit.
The way to prevent that is usually to make things heavier.

The difference with aluminum alloys is that at least in principle, every
aluminum bit subject to fatigue loading will _eventually_ fatigue. But
if it fails after enough billions of fatigue cycles, the original
designer usually doesn't care.

I reckon 10,000 miles is in the region of only 6 million stress cycles.
Assuming stress cycles are predominantly from pedalling.

In my case that was about 4 years, not really enough.

My suspicion is that very few bikes get ridden 10,000 miles. They either
get ridden occasionally or replaced regularly. It is probably cheaper to
give lifetime guarantees and quote fantasy figures for fatigue cycles,
rather than engineer light aluminium frames that do last a lifetime

Every road bike I have/had has or will be ridden 10000 miles/16000 km.

Lou