Bike frame tests

[David Storm]

I'm not sure what I'm starting here, but haven't seen this kind of discussion since I started
reading here. I hope I'm not stirring up a previous, laid-to-rest discussion. I found some
surprising results of some torture fatigue tests for various road frames at:
http://www.efbe.de/defbefrm.htm (go to public reports) where Ti and steel were some of the first to
fail and some Al and carbon frames survived the test.

I've been thinking about buying a high end Ti bike soon, having seen first-hand failures of carbon
(mainly drop-outs pulling free of chain-stays) so I'm not sure what to make of the tests which
didn't appear to address such potential failures.

It would be interesting to hear of some opinions of the reported test results from knowledgeable
riders and those with some experiences with frame failures.

 

[Steve Blankensh]

Been dealt with before here - note the date of the test: 1997. As to failures of different kinds of
frames, each has its particular problem areas, be it overheating of weld zones, weld contamination,
poor bonding etc., but these are more manufacturing QC issues than material ones. A well-designed
AND built frame of Steel, AL, Ti or Carbon is very unlikely to fail under normal use. But if you're
looking for cutting-edge light weight, then expect to pay a price in durability and reliability, no
matter the material.

Thus was it ever -

SB

"David Storm" <[email protected]> wrote in message
news[email protected]...
> I'm not sure what I'm starting here, but haven't seen this kind of discussion since I started
> reading here. I hope I'm not stirring up a previous, laid-to-rest discussion. I found some
> surprising results of some torture fatigue tests for various road frames at:
> http://www.efbe.de/defbefrm.htm (go to public reports) where Ti and steel were some of the first
> to fail and some Al and carbon frames survived the test.
>
> I've been thinking about buying a high end Ti bike soon, having seen first-hand failures of carbon
> (mainly drop-outs pulling free of chain-stays) so I'm not sure what to make of the tests which
> didn't appear to address such potential failures.
>
> It would be interesting to hear of some opinions of the reported test results from knowledgeable
> riders and those with some experiences with frame failures.
>
>

 

[Mike Jacoubowsk]

There really isn't anything in that test to refute the fact that it's not the material, it's what
you do with it that makes the difference. There is no frame material that guarantees the builder
cannot make a dangerous frame, including titanium (which, if pushed too far by the builder, can fail
in a catastrophic manner that's truly impressive... been there, done that). And the data from that
test is all over the map in terms of how recently each was tested, including my beloved OCLV that
dates back to 1997.

If a manufacturer feel comfortable giving a long warranty, that *might* (but isn't always) be an
indication that it's well-designed. At the very least it gives you some peace of mind down the road.
Another thing to look for are those qualities that are going to make you want to ride the bike more.
I used to think that only had to do with how it actually rode & fit you and, while those certainly
should be the top criteria, I have many customers who put in lots of miles and love their bikes
simply because they love the way they look. Hey, whatever it takes to get someone out riding.

--Mike-- Chain Reaction Bicycles http://www.ChainReactionBicycles.com

"David Storm" <[email protected]> wrote in message
news[email protected]...
> I'm not sure what I'm starting here, but haven't seen this kind of discussion since I started
> reading here. I hope I'm not stirring up a previous, laid-to-rest discussion. I found some
> surprising results of some torture fatigue tests for various road frames at:
> http://www.efbe.de/defbefrm.htm (go to public reports) where Ti and steel were some of the first
> to fail and some Al and carbon frames survived the test.
>
> I've been thinking about buying a high end Ti bike soon, having seen first-hand failures of carbon
> (mainly drop-outs pulling free of chain-stays) so I'm not sure what to make of the tests which
> didn't appear to address such potential failures.
>
> It would be interesting to hear of some opinions of the reported test results from knowledgeable
> riders and those with some experiences with frame failures.
>
>

 

[Jon Isaacs]

>It would be interesting to hear of some opinions of the reported test results from knowledgeable
>riders and those with some experiences with frame failures.
>

This data has been discussed here many times.

Do a google search.

Some things to consider:

The loads: 1300 newtons is about 300 lbs.

The number of cyclic loadings: 100,000 cycles is the equivilent of about 200 miles of riding at
15mph and 60 rpm.

My conclusion is that the loads are too high, the number of cycles too few, a good test if you are
designing track frames for Marty Nostein.

It may seem like these are reasonable tests but from a materials science view point, it is good to
note that some materials, noteably steel and titanium have endurance limits. This means as long as
the stresses are kept below the endurance limit, then no fatigue occurs.

Thus steel and titanium are more vulnerable to a poorly conceived test scheme because if the loads
are unrealistically high, then they may fatigue where they would not under normal riding conditions.
Since aluminum has no edurance limit, an aluminum frame needs to be over designed from a strength
standpoint in order to handle everyday fatigue issues. CF has neither of these issues but has other
issues, catastrophic failure modes and hidden damage evaluations.

So, from my point of view, these tests have some value but really are not appropriate to accurately
estimate the fatigue life of bicycle frames.

jon isaacs

 

[Mark Hickey]

[email protected] (Jon Isaacs) wrote:

>This data has been discussed here many times.
>
>Do a google search.
>
>Some things to consider:
>
>The loads: 1300 newtons is about 300 lbs.
>
>The number of cyclic loadings: 100,000 cycles is the equivilent of about 200 miles of riding at
>15mph and 60 rpm.
>
>My conclusion is that the loads are too high, the number of cycles too few, a good test if you are
>designing track frames for Marty Nostein.

Jon hit it on the head. The tests might be valid for the proverbial 800 pound gorilla, but the
results don't resemble those in the real world in terms of failure mode and relative frequency (the
ultimate test validator). Unfortunately, doing a truly real-world correlated test would require
literally months of test time for each frame. It's not hard to see why they chose to try to compress
the testing into a very short period.

Mark Hickey Habanero Cycles http://www.habcycles.com Home of the $695 ti frame

 

[David Storm]

Thanks for responses. I'm going to test ride a carbon loaner from local bike shop soon, but right
now lean towards Ti in spite of test results.

"David Storm" <[email protected]> wrote in message
news[email protected]...
> I'm not sure what I'm starting here, but haven't seen this kind of discussion since I started
> reading here. I hope I'm not stirring up a previous, laid-to-rest discussion. I found some
> surprising results of some torture fatigue tests for various road frames at:
> http://www.efbe.de/defbefrm.htm (go to public reports) where Ti and steel were some of the first
> to fail and some Al and carbon frames survived the test.
>
> I've been thinking about buying a high end Ti bike soon, having seen first-hand failures of carbon
> (mainly drop-outs pulling free of chain-stays) so I'm not sure what to make of the tests which
> didn't appear to address such potential failures.
>
> It would be interesting to hear of some opinions of the reported test results from knowledgeable
> riders and those with some experiences with frame failures.
>
>

 

[Jon Isaacs]

>Thanks for responses. I'm going to test ride a carbon loaner from local bike shop soon, but right
>now lean towards Ti in spite of test results.

It is also important not to associate the results of a frame not tested with one that was tested
just because they are of the same material. Fatigue is a design issue.

Clearly the frames that are most suspectible to fatigue are the "Stupid-Lite" aluminum frames. These
frames are designed with the understanding that that the weight saved is important and that the
resulting poor fatigue life is part of the bargin.

Jon Isaacs

 

[Mike Jacoubowsk]

> Clearly the frames that are most suspectible to fatigue are the
"Stupid-Lite"
> aluminum frames. These frames are designed with the understanding that
that
> the weight saved is important and that the resulting poor fatigue life is
part
> of the bargin.

The problem is that the general public doesn't understand that the exact same material, used two
different ways, can result in one bike with an extremely impaired fatigue life, while another would
last a lifetime. People need to understand that the unique properties of a given frame material
(steel, ti, carbon, aluminum) have little, if anything, to do with durability... if the material is
used correctly.

--Mike-- Chain Reaction Bicycles http://www.ChainReaction.com

"Jon Isaacs" <[email protected]> wrote in message
news:[email protected]...
> >Thanks for responses. I'm going to test ride a carbon loaner from local bike shop soon, but right
> >now lean towards Ti in spite of test results.
>
> It is also important not to associate the results of a frame not tested
with
> one that was tested just because they are of the same material. Fatigue
is a
> design issue.
>
> Clearly the frames that are most suspectible to fatigue are the
"Stupid-Lite"
> aluminum frames. These frames are designed with the understanding that
that
> the weight saved is important and that the resulting poor fatigue life is
part
> of the bargin.
>
> Jon Isaacs