Wednesday, September 9, 2015

Derailleur Cables and Why You Break Them

Recently it seems that bike crap is happening at lightning speed. I heard that bikes have disc brakes even shift electronically now.

Maybe I come from a simpler time, but I seem to remember when cables were all we had and damn it, that was good enough for us! Now they are using the Wi-Fi or whatever and it's folks like me who are becoming a rarity. That is, the mechanical stuff is still around and someone has got to know what the hell they are doing when it comes to fixing it! So rare I may be, but contrary to what the internet would have you believe, I am still very relevant. 

Making a cable actuated system "sing" is a thing of beauty and from a simplicity stand point, is field serviceable. Done correctly, it requires very little care or maintenance but perhaps once a year.

One of the most basic things that can be done on even the most expensive bicycles is changing cables once a year yet, a large majority of riders I encounter have difficulty with this simple ideal because to them it is not broken so "why fix it?"

If you have ever had a rear derailleur cable snap off inside a Shimano shifter then you have likely heard this story before. If you have not well then you are one of the lucky ones. Take notes, as the story begins like this:

A grasshopper walks up to the bar and the bartender says "you know they have a drink named after you?" To which the grasshopper replies "they have a drink named Irving?"

A Fred walks into the shop with his Fred Sled and says
"It won't shift."
I see.

Well, there's your problem. When was the last time it was in for service?  

"oh, it couldn't be more that 5 years."

Holy fuck! MORE?! It shouldn't be NEAR 5 years! 
-This is the point at which I take out my chain checker and it drops straight through the chain (which means his cassette is toast as well).

 -Now it is a very different conversation, but I digress...

 This particular Fred was lucky. I mean, he still paid for it in the end because his really expensive bike was really worn out but at least that cable head did not bust off in his shifter. That would be a more serious problem because Shimano shifters are not "serviceable," which means they cannot (or at minimum SHOULD NOT) be disassembled. 
Shimano shifters, while excellent at their jobs, are not infallible. Indeed, the industry is well aware of this particular issue and, since the earliest 7 speed STI shifters, has worked to rectify it. While they still have not yet fixed the issue entirely, they have certainly made the shifter more "approachable," that is to say that in the newer shifters, it is much easier to remove a broken cable head should you need to. 

So there's that.

The trick is catching it before it fails.


If this is happening inside you shifter you will feel it. The cable splintering like that creates massive drag and what amazes me is that people will continue to ride it like that! Sure, they might not know that it looks like that inside there, but damn it, if all of the sudden your shifting performance drops off dramatically, it's a pretty good sign that something is up. Why a rider would continue to put up with poor shifting is beyond me. But hell, when I see other, obvious cable failures, it baffles me in the same way.  

"yeah, it just stopped shifting"

I keep broken cable heads to show customers, I educate them endlessly about regular service intervals, I hold their hand through life's most difficult choices;

"What's the best tire size?"

"What pressure should I be running?"

"What would YOU choose?"

...still, they fail to listen.

As I live and breath, I shit you not;
While I was typing this very post another one came in the door...

 
 Any technician worth a piss will look this customer right in the eye and lay it out pretty bluntly:



 "This could get costly"

So first, we have to explain why this happens
 



 A) Because the cable head is being rotated on a small barrel back-and-forth and fatigue sets in, splintering a couple of the wires, they "unwind" inside the mechanism until they all break. That is where the drag comes from.

oh, and
B) Because you touch yourself at night.

Really though, even Shimano knows it was a bad design  
design flaw and has since "fixed" it with "improved cable routing"
 through the body of the shifter. Now, I call bull shit for two reasons here which are;

One) The original design had very low drag which made Shimano ten speed
(and even 9 speed) models like, Ultegra and Dura Ace shift with little effort yet still offered a crisp feel at the lever. The ONLY problem was the cable breakage. Again, a problem which can still be avoided on those older shifters by simply replacing a $3 cable.

Two) The "improved" routing may have fixed (about 90% of) the breakage issue, but added about 60% more friction (100% if it is a stupid internally routed frame) to the shift mechanism. What then? They introduce a $25 (TWENTY FIVE DOLLAR) shift cable to "reduce" drag.

They fixed nothing. 

 

...and that is why they want to sell you Di2
 

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