Dura-Ace 7800 cranks are HOW strong?

Discuss light weight issues concerning road bikes & parts.
mzagorski
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by mzagorski

145lb rider... Just riding along...
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DSC06667_srm_1.jpg

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airsoft510
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by airsoft510

hmm interesting i thought shimano cranks were suposed to be strong and stiff, maybe there was something wrong with his

by Weenie


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Mads Kock
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by Mads Kock

mzagorski wrote:Just riding along...


JRA.... when hit by a train? :-)

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Amadeus
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by Amadeus

MZAGORSKI,

I am curious …..

How did this happen?

Just riding in the saddle? Sprinting? Accelerating?

Did you have some accident before?
Did you hit the ground often with your right pedal?

If this all is not the case this is awful!!!!

On your picture I also do notice quite a lot of scratches on the crank. It looks like you shifted over the big chain ring quite a few times. As you know scratches in an aluminium pipe or handlebar often lead to breaking. I don’t know if this also is applicable to the forged aluminium hollow construction of a Dura Ace crank.

Somebody else knows?
My bike is Italian so it is Nervosa and of course has Anorexia I like them thin!
GIOS "New" Carbon Ultra 2006 Campa Record+Special parts.
GIOS "New" A90 2008 Campa Record+Special parts. My winter and vacation bike.

mzagorski
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by mzagorski

Well, I'd just finished up a 60 mile training ride, and some intervals on hills. Was going through some traffic lights as they changed to green and was out of the saddle. Not a full on sprint.. then the arm just went flop! I was like WTF was that???.. and was really surprised to see the arm all bent when I tried to clip in.

Yeah, some scratches on the arm from chain overshifting a few times but nothing I've not had on other cranksets. Haven't ever had a big landing on the right arm.. pedal is in excellent condition too.

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Knut
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by Knut

First off, glad you're all right, could have been messy!

Second, shit happens - it's a production dud, no more no less... take it to the reseller and see about a warranty replacement.

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Amadeus
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by Amadeus

Well that is about the ame situation we did read about ont the breaking of the Stronglight Carbon cranks......

Odd that this happened .......

You are a lucky guy that it did not happen during a sprint interval....Could have been messy....

But you know Murphy is always riding with you so anything that can go wrong will go wrong .......

Have often seen broken cranks Shimano and Campagnolo in the old days (1980-1990). But this rarely happens nowadays ....

Get it replaced by a new ano should be a waranty problem.
My bike is Italian so it is Nervosa and of course has Anorexia I like them thin!
GIOS "New" Carbon Ultra 2006 Campa Record+Special parts.
GIOS "New" A90 2008 Campa Record+Special parts. My winter and vacation bike.

rruff
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by rruff

mzagorski wrote:145lb rider... Just riding along...


Mike, that is pretty impressive! You didn't notice anything weird before it broke?

Could you post a couple more pics from other angles?

mzagorski
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by mzagorski

I'll post an updated. The crank wasn't a plain Dura-ace 7800, it's the Dura-Ace SRM Pro. Didn't notice anything wierd before it broke.

Have spoken to SRM and so far they've been awesome and I should be getting a replacement within the next few days. Even had Shimano call me yesterday to ask me more about how it happened. It's nice to know that both SRM and Shimano care about their products and will support them.

wishIwasSponsored
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by wishIwasSponsored

After you get your replacement you should go on other forums and brag about your crank ruining 2000w sprint :D . I can see it now...."and then as I came around Petacchi..."

mzagorski
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by mzagorski

at 145lbs I doubt I'll ever see 2000watts... well, unless it's someone unleashing it and crossing the line ahead of me... or maybe some 300lb rider doing 2000w and getting dropped :)

Here's another overall photo.
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2006-6-27_snapped_srm.jpg

Squint
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by Squint

How did Shimano hear about it?

I would think that the machining process would void the Shimano warranty.

I ordered my DA SRM yesterday but I'm not concerned as I rarely break equipment.

mzagorski
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by mzagorski

Well I presume that SRM work closely with Shimano as the whole reason they made the D-ace SRM was for Shimano sponsored riders that needed a powermeter but had sponsorship obligations (namely, probably Lance)... It's the arm that broke so seemed like Shimano got involved in the mix too. I've seen plenty of d-ace SRM's but never any broken until now so I think it's just a one off defect... Will be interesting to see what they reckon was the cause of failure though.

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Amadeus
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by Amadeus

Well it is a good sign that Shimano called.

But they really should ask you for the crank and do some research (they get it from SRM probably).

The Construction is the same for DA, Ultegra and for the compact.
Hope this is not a construction failure.

Should be an incident. The cold forging process is claimed be one of the best ways to produce a strong crank arm. And the hollow construction should be very strong.

I ride for more then 25 years now and have seen cranks braking a few times but mostly in the mid 80's to mid 90's after that the products got much better (Today they forge also on a more reliable way and under higher pressure). And if they broke in the old days it was at mostly there where the pedal thread or there where the front derailleur had scratched the right crank. And in those days it was always Ofmega and Campagnolo that failed (the old types). First time I see this at a modern Shimano crank.

Maybe this website is of interest.
http://pardo.net/pardo/bike/pic/fail/FAIL-001.html
It is mostly older stuff you see.

I am curious how Shimano will take action ….just curious.

It is always scary if you realize what could have happened if it broke at a “less convenient” moment………


P.S.
I use the following crank sets: one Campagnolo record 180 and two TA Carmina 180mm and one TA Carmina 185mm and have an old TA Alize 185mm never had any problems and I am a 190cm long an >90kg rider.
My bike is Italian so it is Nervosa and of course has Anorexia I like them thin!
GIOS "New" Carbon Ultra 2006 Campa Record+Special parts.
GIOS "New" A90 2008 Campa Record+Special parts. My winter and vacation bike.

brianwchan
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by brianwchan

Wow, glad you're ok. Could have been really bad, imagine if you were in a full out sprint. :(

by Weenie


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