Re: [CR]Predicting/preventing NR/SR crank breakage


Example: Component Manufacturers:Avocet

Date: Tue, 3 Sep 2002 06:55:03 -0700 (PDT)
From: Tom Dalton <tom_s_dalton@yahoo.com>
Subject: Re: [CR]Predicting/preventing NR/SR crank breakage
To: classicrendezvous@bikelist.org
In-Reply-To: <071401c250f6$31803d60$efddfea9@mooshome>


Jerry & Liz Moos wrote: That might be true in the tiny world of U.S. racing, but in the wider cycling world I suspect that up until the mid-80's when Stronglight sales began to decline badly, there were probably a lot more miles put on Stronglight every year than Campy.

It also holds true in the far less tiny world of racing world-wide. As I recall, the point was that we tend to see Campy crank failures because we tend a lot of Campy cranks. In my narrow experience of working in bikeshops between 1984 and 1994 and racing since 1981, I rarely saw Stronglight cranks, but "everybody" used Campy. So, if I lived in France in the early 60's and I was a tourist, I'm sure my experience would be different.

Jerry & Liz Moos wrote: I suspect that laboring up a mountain pass with 50 lbs of gear stresses a crank as much as a Cippolini sprint.

Sure, and the crankshaft in my Chevy Nova gets just as much stress as the crank in Michael Schumacher's Ferrari... Ugh!

Jerry & Liz Moos wrote:I would differ with the assessment that Campy cranks have seen more miles than Stronglight. That might be true in the tiny world of U.S. racing, but in the wider cycling world I suspect that up until the mid-80's when Stronglight sales began to decline badly, there were probably a lot more miles put on Stronglight every year than Campy. How many loaded touring bikes have you ever seen with Campy cranks? In the classic era, these were alway equipped with Stronglight, as the smaller bolt circle allowed a reasonable choice of chainrings, which Campy did not. Maybe you don't consider that "hard-ridden", but I suspect that laboring up a mountain pass with 50 lbs of gear stresses a crank as much as a Cippolini sprint.

Although I don't have the equipment or knowledge to perform hardness tests on cranks, I'm pretty sure that Stronglight cranks are softer than the Campy alloy, which usually translates into less brittle as well. I believe this is the main reason Stronglight never had nearly the Campy problems with cracking. The downside is that softer cranks are more likely to seize up on the crank axle than harder ones. I've personally had the unpleasant experience of trying to remove a Stronglight crank arm that had virtually welded itself to te axle. That's why I always apply at least a slight touch of grease when installing crank arms. I've never seen a Campy arm seized that tightly to an axle, and never personally experienced a seized Campy arm at all.

Regards,

Jerry Moos
Houston, TX


----- Original Message -----
From: "Tom Dalton"
To:
Sent: Wednesday, August 28, 2002 10:05 AM
Subject: Re: [CR]Predicting/preventing NR/SR crank breakage



>
> I suspect the fact that you have never seen or heard of a Stronlight crank breaking is a reflection of the reality that in the last 30 years, there has probably been one hard-ridden Stronglight crank for every several hundred Campy. Campy's reputation for durability used to (and may still) lead people to use their parts way, way beyond the reasonable service life. Back in the day, people use to buy and use third and forth hand Campy stuff with no knowledge of previous use. It may be a good thing that modern equipment doesn't function after a certain amount of wear, or becomes unservicable due to incompatibilities. If old Campy cranks broke, what is going to happen to all these sub- 200g handlebars?
> As to predicting... there is almost always some sort of visible, incipient crack before an arm (or frame) breaks. Inspect those cranks.
> Tom
> PBridge130@aol.com wrote:
>
> Has this subject been done to death prior to my arrival?
>
> I went down very hard once, when my N/SR crankarm snapped, a couple inches up
> from the pedal. I was going fairly fast at the time. In addition to the
> normal rash, I had a helmet that was crushed on one side, and only the
> slightest of headaches (there's gotta be a lesson in there somewhere).
>
> I think it's understandable that my enthusiasm for riding hard on similar
> cranks has been dampened, perhaps explaining my enthusiasm for
> Stronglight-equipped bikes (I've never heard of one of those breaking, and if
> they do, I don't think I want to know about it).
>
> I just measured the broken end. Break occurred two inches from center of
> pedal, straight across the arm, 172.5 arm, "11" in a square.
>
> So. What do I watch for? How do I anticipate catastrophic failure, and
> avoid it? Hanging the bike on the wall and admiring it while quaffing a
> brewski and smoking a cigar might be an acceptable strategy, but probably
> isn't the ideal one.

>

> Thanks y'all,

>

> Peter Bridge

> DenCO