carbon crank scratched - concern?

On Saturday, April 25, 2020 at 5:12:02 PM UTC+2, jbeattie wrote:
On Saturday, April 25, 2020 at 1:39:51 AM UTC-7, James wrote:
On 25/4/20 10:21 am, jbeattie wrote:


I've failed two CF cranks at the pedal eyes. The threaded inserts
tend to separate from the surrounding carbon lay-up or crack or the
carbon cracks. One crank was OE SRAM Red on a Cannondale and the
other was an ISIS POS FSA that I got on sale (and regretted). I
wouldn't bother with CF cranks.


Wow you have a bad time. I pounded out another 120km today over rough
roads and climbs up to 15% with my Campagnolo UT cranks. Never been a
problem.

Do the threaded inserts come adrift when you remove or tighten pedals,
or just happens while you're riding?

The threaded insert either cracked or separated from the surrounding lay-up or both. SRAM acknowledged the problem -- which is not uncommon bonding dissimilar materials. It happened during riding an not disassembly.

I use my chain lube wax & oil mix to lubricate my pedal threads, and
only tighten them on to the crank with maybe 10 Nm of torque? They are
never difficult to remove, and don't unwind of their own free will.

I have seen pedals loosen, but only because the pedal bearings were near
seized. Not on my bike.

The problem is not with the pedal seizing. I use ordinary anti-seize on my pedals -- with washers to avoid CF damage. BTW typical torque spec for pedals is 30-40 Nm -- or even higher for some mfg.

-- Jay Beattie.

That is ridiculously high and unnecessary IMO.

Lou

On 4/24/2020 1:41 PM, Ted Heise wrote:
Hi all,

A couple of days ago I noticed a scratch on a carbon crank. Pics
are he

http://www.panix.com/~theise/IMG_7765.jpg

http://www.panix.com/~theise/IMG_7766.jpg

It's on my tandem, so I'm especially senstive to safety. The
scratch does not feel as if it has much depth to it. I think it
may have happened when I lost my balance getting off, and could
potentially have banged it with the Speedplay cleat on the bottom
of my shoe.

Should I be concerned about failure?

Yes, but not necessarily because of that scratch.

As an aside, I wasn't paying enough attention when I ordered this
bike. I specifically wanted titanlum for resistance to cosmetic
damage, but would have preferred *not* to have carbon components
(also for resistance to handling damage).

Yeah, amazing that they would put carbon fiber cranks on a tandem.

Moving to titanium would be incredibly expensive.

Something this tandem set from Rivendell
https://www.rivbike.com/collections/cranks-bbs/products/silver-tandem-crank-preorder
would be fine for only $500.

On Fri, 24 Apr 2020 17:25:27 -0500,
AMuzi wrote:
On 4/24/2020 3:41 PM, Ted Heise wrote:

A couple of days ago I noticed a scratch on a carbon crank.
Pics are he

http://www.panix.com/~theise/IMG_7765.jpg

http://www.panix.com/~theise/IMG_7766.jpg

It's on my tandem, so I'm especially senstive to safety. The
scratch does not feel as if it has much depth to it. I think
it may have happened when I lost my balance getting off, and
could potentially have banged it with the Speedplay cleat on
the bottom of my shoe.

Should I be concerned about failure?

Ask your dealer to examine the crank to see if it's merely a
cleat scratch or if it is indeed cracked. If it's cracked, ask
about warranty. Examine the other three as well (direct
sunlight and a magnifier).

Thanks for the feedback, Andrew. As it happens, I bought the bike
from a distant dealer, so having him examine it is not a very
practical option. I'm not very impressed with the shops here, but
there's a place in Indianapolis that has a pretty good reputation.
Looks like your place is more than a four hour drive, or I'd think
about bringing it to you.

To Jay's point, I should probably look at the pedal spindle
attachment points too. We are not excessively heavy (probably 325
pound team weight), but do stand a lot on hills.

--
Ted Heise West Lafayette, IN, USA

On Saturday, April 25, 2020 at 8:46:24 AM UTC-7, wrote:
On Saturday, April 25, 2020 at 5:12:02 PM UTC+2, jbeattie wrote:
On Saturday, April 25, 2020 at 1:39:51 AM UTC-7, James wrote:
On 25/4/20 10:21 am, jbeattie wrote:


I've failed two CF cranks at the pedal eyes. The threaded inserts
tend to separate from the surrounding carbon lay-up or crack or the
carbon cracks. One crank was OE SRAM Red on a Cannondale and the
other was an ISIS POS FSA that I got on sale (and regretted). I
wouldn't bother with CF cranks.


Wow you have a bad time. I pounded out another 120km today over rough
roads and climbs up to 15% with my Campagnolo UT cranks. Never been a
problem.

Do the threaded inserts come adrift when you remove or tighten pedals,
or just happens while you're riding?

The threaded insert either cracked or separated from the surrounding lay-up or both. SRAM acknowledged the problem -- which is not uncommon bonding dissimilar materials. It happened during riding an not disassembly.

I use my chain lube wax & oil mix to lubricate my pedal threads, and
only tighten them on to the crank with maybe 10 Nm of torque? They are
never difficult to remove, and don't unwind of their own free will.

I have seen pedals loosen, but only because the pedal bearings were near
seized. Not on my bike.

The problem is not with the pedal seizing. I use ordinary anti-seize on my pedals -- with washers to avoid CF damage. BTW typical torque spec for pedals is 30-40 Nm -- or even higher for some mfg.

-- Jay Beattie.

That is ridiculously high and unnecessary IMO.

Lou

Shimano specs 35-55 Nm. https://si.shimano.com/pdfs/dm/DM-RAPD001-00-ENG.pdf
(p. 13) I doubt I do better than 25 Nm hand tightening with a standard pedal hex wrench.

-- Jay Beattie.

On 4/25/2020 11:46 AM, wrote:
On Saturday, April 25, 2020 at 5:12:02 PM UTC+2, jbeattie wrote:
On Saturday, April 25, 2020 at 1:39:51 AM UTC-7, James wrote:
On 25/4/20 10:21 am, jbeattie wrote:


I've failed two CF cranks at the pedal eyes. The threaded inserts
tend to separate from the surrounding carbon lay-up or crack or the
carbon cracks. One crank was OE SRAM Red on a Cannondale and the
other was an ISIS POS FSA that I got on sale (and regretted). I
wouldn't bother with CF cranks.


Wow you have a bad time. I pounded out another 120km today over rough
roads and climbs up to 15% with my Campagnolo UT cranks. Never been a
problem.

Do the threaded inserts come adrift when you remove or tighten pedals,
or just happens while you're riding?

The threaded insert either cracked or separated from the surrounding lay-up or both. SRAM acknowledged the problem -- which is not uncommon bonding dissimilar materials. It happened during riding an not disassembly.

I use my chain lube wax & oil mix to lubricate my pedal threads, and
only tighten them on to the crank with maybe 10 Nm of torque? They are
never difficult to remove, and don't unwind of their own free will.

I have seen pedals loosen, but only because the pedal bearings were near
seized. Not on my bike.

The problem is not with the pedal seizing. I use ordinary anti-seize on my pedals -- with washers to avoid CF damage. BTW typical torque spec for pedals is 30-40 Nm -- or even higher for some mfg.

-- Jay Beattie.

That is ridiculously high and unnecessary IMO.

Our Bike Friday folding bikes require removing their pedals to pack in
their suitcases for airline flights. The pedal wrench that came with the
bikes is roughly 6" or 15mm long. (It's cut out of flat steel, maybe
1.5mm thick, and has a headset wrench on the other end.)

I was skeptical about using it on pedals, because its small size limits
toque. But it's installed and removed pedals many, many times with no
problems. (The cranks are fairly low end Shimano aluminum.)

Those bikes don't get used for high mileage, but given that ordinary
pedaling tightens pedals instead of loosening them, I don't think more
mileage would make a difference.


--
- Frank Krygowski

On 4/25/2020 10:12 AM, jbeattie wrote:
On Saturday, April 25, 2020 at 1:39:51 AM UTC-7, James wrote:
On 25/4/20 10:21 am, jbeattie wrote:


I've failed two CF cranks at the pedal eyes. The threaded inserts
tend to separate from the surrounding carbon lay-up or crack or the
carbon cracks. One crank was OE SRAM Red on a Cannondale and the
other was an ISIS POS FSA that I got on sale (and regretted). I
wouldn't bother with CF cranks.


Wow you have a bad time. I pounded out another 120km today over rough
roads and climbs up to 15% with my Campagnolo UT cranks. Never been a
problem.

Do the threaded inserts come adrift when you remove or tighten pedals,
or just happens while you're riding?

The threaded insert either cracked or separated from the surrounding lay-up or both. SRAM acknowledged the problem -- which is not uncommon bonding dissimilar materials. It happened during riding an not disassembly.

I use my chain lube wax & oil mix to lubricate my pedal threads, and
only tighten them on to the crank with maybe 10 Nm of torque? They are
never difficult to remove, and don't unwind of their own free will.

I have seen pedals loosen, but only because the pedal bearings were near
seized. Not on my bike.

The problem is not with the pedal seizing. I use ordinary anti-seize on my pedals -- with washers to avoid CF damage. BTW typical torque spec for pedals is 30-40 Nm -- or even higher for some mfg.

-- Jay Beattie.




Yes, I've seen pedal inserts achieve liberation from carbon
cranks in SRAM and Campagnolo (both rarely).

I think what James meant is that a binding or failed pedal
bearing is hard on that joint (not the thread between pedal
and crank) and he's right.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Friday, April 24, 2020 at 1:41:10 PM UTC-7, Ted Heise wrote:
Hi all,

A couple of days ago I noticed a scratch on a carbon crank. Pics
are he

http://www.panix.com/~theise/IMG_7765.jpg

http://www.panix.com/~theise/IMG_7766.jpg

It's on my tandem, so I'm especially senstive to safety. The
scratch does not feel as if it has much depth to it. I think it
may have happened when I lost my balance getting off, and could
potentially have banged it with the Speedplay cleat on the bottom
of my shoe.

Should I be concerned about failure?

As an aside, I wasn't paying enough attention when I ordered this
bike. I specifically wanted titanlum for resistance to cosmetic
damage, but would have preferred *not* to have carbon components
(also for resistance to handling damage).

Thanks for any advice!

--
Ted Heise West Lafayette, IN, USA

Ted, that scratch is insignificant but it appears to have a crack in the crank arm. If that is actually what it is you MUST throw that out immediately.

On Friday, April 24, 2020 at 2:01:03 PM UTC-7, Joerg wrote:
On 2020-04-24 13:41, Ted Heise wrote:
Hi all,

A couple of days ago I noticed a scratch on a carbon crank. Pics
are he

http://www.panix.com/~theise/IMG_7765.jpg

http://www.panix.com/~theise/IMG_7766.jpg

It's on my tandem, so I'm especially senstive to safety. The
scratch does not feel as if it has much depth to it. I think it
may have happened when I lost my balance getting off, and could
potentially have banged it with the Speedplay cleat on the bottom
of my shoe.

Should I be concerned about failure?

As an aside, I wasn't paying enough attention when I ordered this
bike. I specifically wanted titanlum for resistance to cosmetic
damage, but would have preferred *not* to have carbon components
(also for resistance to handling damage).

Thanks for any advice!


I'd be more concerned about that apple-shaped outline above the scratch,
very visible in the 2nd photo link.

Personally I do not like carbon components where structural failure
could cause a lot of grief. I'd get new metal cranks, even if it's just
for peace of mind.

I guess this guy was lucky:

http://www.bustedcarbon.com/2009/02/...falls-off.html

--
Regards, Joerg

http://www.analogconsultants.com/

I agree and that is why I'm using Ultegra cranksets now. They are so light that the savings of carbon is minimal at best. I also discovered that my aluminum Cannondale stem and Specialized bars are LIGHTER than my single piece integrated carbon bar. Wondrous things having a scale - when you look at the so-called claimed weights and actually measure them you discover large differences.

On Sun, 26 Apr 2020 08:55:14 -0700 (PDT),
wrote:
On Friday, April 24, 2020 at 1:41:10 PM UTC-7, Ted Heise wrote:
Hi all,

A couple of days ago I noticed a scratch on a carbon crank.
Pics are he

http://www.panix.com/~theise/IMG_7765.jpg

http://www.panix.com/~theise/IMG_7766.jpg

It's on my tandem, so I'm especially senstive to safety. The
scratch does not feel as if it has much depth to it. I think
it may have happened when I lost my balance getting off, and
could potentially have banged it with the Speedplay cleat on
the bottom of my shoe.

Should I be concerned about failure?

Ted, that scratch is insignificant but it appears to have a
crack in the crank arm. If that is actually what it is you MUST
throw that out immediately.

Thanks, Tom, but I'm not seeing what you may be calling a crack
separate from the scratch. Could you describe the location? I'm
thinking it may be an artifact of the (crappy) photography.

--
Ted Heise West Lafayette, IN, USA

On Sunday, April 26, 2020 at 6:24:53 PM UTC+2, Ted Heise wrote:
On Sun, 26 Apr 2020 08:55:14 -0700 (PDT),
wrote:
On Friday, April 24, 2020 at 1:41:10 PM UTC-7, Ted Heise wrote:
Hi all,

A couple of days ago I noticed a scratch on a carbon crank.
Pics are he

http://www.panix.com/~theise/IMG_7765.jpg

http://www.panix.com/~theise/IMG_7766.jpg

It's on my tandem, so I'm especially senstive to safety. The
scratch does not feel as if it has much depth to it. I think
it may have happened when I lost my balance getting off, and
could potentially have banged it with the Speedplay cleat on
the bottom of my shoe.

Should I be concerned about failure?

Ted, that scratch is insignificant but it appears to have a
crack in the crank arm. If that is actually what it is you MUST
throw that out immediately.

Thanks, Tom, but I'm not seeing what you may be calling a crack
separate from the scratch. Could you describe the location? I'm
thinking it may be an artifact of the (crappy) photography.

--
Ted Heise West Lafayette, IN, USA

We need better photo's. The scratch is clear all the other is a wild guess.

Lou