RandomTroll

Do stainless steel derailleur wires last longer than galvanized?

I've broken the wire of the front derailleur (triple) 11 times in the last 11 years, always at the derailleur. (I haven't broken the wire for the rear derailleur once.)

The shift levers are on the downtube. The derailleur is a Shimano 105.


Rust is not a problem.

DMF 

Stainless steel is generally more brittle than non-stainless steel, but if you don't know what's under the tin, you can't make a comparison.

Advice: Whatever you're using (and breaking), try the other one.

RandomTroll

That's what I think; then again, galvanization adds a layer of zinc: that means less steel.

I do know: Jagwire (basic and more-expensive), Clark's, Pyramid, Shimano, no-name. Unfortunately life doesn't correspond with brand, and 11 is a small sample.

fietsbob

I grease my Zn treated Die drawn Cables .. that resists the potential Rust in the Housing .

Im still using the same transverse cantilever cables on my Mafac Cantilevers as came on them when I installed them in 1976.




choose your favorite 3 anecdotes as evidence to support what ever opinion you have. It works in Politics.

FastJake

Are you tightening it down way too much? Or is it becoming bent or crimped in some weird direction? I don't think galvanized vs. stainless is the issue here.

CliffordK

I wouldn't guarantee that all cable brands are the same. Unfortunately everything is moving to China with limited QC, so it may be difficult to tell what you're getting. I did notice that the cable ends seem to be shrinking over time.

I rarely break cables, but I think they end up eventually fraying and braking at the shifter or brake levers. But they can last me for years. I think my last broken cable had rusted somewhat near the bottom bracket cable guide, but still broke at the shifter.

I'd look at what is happening at the point of breakage. Angles? Overtightening?

Also, are you using indexed shifting or friction shifting, and do you have barrel adjusters? I try to avoid repeatedly messing with the bolts on either the brakes or shifters (although sometimes it is unavoidable). Set it once, and ignore it.

HillRider

I'm with FastJake on this one. 11 broken cables in 11 years is way off the charts and I'm sure are doing something to damage the cable. Stainless or galvanized isn't the issue. I've never broken a shift cable in 30 years and 185,000+ miles using downtube, barend, and both Shimano and Campy brifters and I use cables, nearly always stainless, for a couple of years between changes so it's not like I change them often.

RandomTroll

I think I tighten it just enough. I often don't tighten it tightly enough, it slips, and I tighten it more. Is there something that could have happened to the derailleur to make it not hold unless I over-tighten?

Not that I can see.

That's what I suspect.

Strands break at the bottom edge of the attachment point. It doesn't feel sharp to my touch. Could it have worn in such a way as to cut the wire?

This wire runs in the open, not inside a cable.

I have no barrel adjusters; it's friction shifting.

FBinNY 

I'm with FastJake and HillRider here. A cable a year points to a problem, not the cables themselves.

Let's get some facts straight. If there's no obvious cause pointing to something else, cables break from metal fatigue. Te constant bending back and forth at the pinchbolt work hardens the wire until it gets brittle and begins ti break strand by strand. But this is the same for all cables, and suffering that much strain that fast isn't even close to normal.

So, some questions

1- are you routing to the right side (the left, or far side is right) of the pinch bolt?
2- are you possibly over tightening the pinch bolt, and crushing the wire? I'm not sure this is a likely cause, but listed it anyway.
3- are you adjusting the FD so that there's a material increase in cable tension when on the outer ring. This error is VERY common, and might account for short cable life. When you replace it, and adjust the FD, shift to high, then draw the bare wire away form the downtube like a bow string. The FD should move out a bit confirming that it isn't parked up against the high limit. If not, odds are you also have excess cable tension, and THAT is the problem.

BTW- to clear up some misconceptions. Galavanzing doesn't affect cable size or strength. The coating is immeasurably thin, so the amount of steel is the same as a stainless wire of the same size. As for durability, the stainless grades used work harden faster than those used on galvanized wires, and die drawing also makes this worse. Better quality wires trade smoother running for shorter life, but still shouldn't be this bad.


Lastly, if all else fails (next year) you can slip a thin stainless or brass tube over the wire at the pinch bolt and extending down about 1/4" or so. This will act as a flex zone to spread out the flex zone in a way similar to the rubber flex on the end of appliance cords. That will significantly increase the fatigue life.

Bill Kapaun

Tighten it tight enough ONCE.

JerrySTL

Well the good news is that if the front derailleur wire breaks, the gears slam down into something easy. Sure beats having the RD wire break while on a hilly ride!

I have to agree with the others. Something is causing the cable to get cut. Too tight? Maybe. FD too stiff causing extra strain? Not so likely. Maybe a burr or something sharp on the FD? Just throwing that on out there.

I usually change the cables every couple of years for preventative maintenance plus better shifting. But in your case, you'd need to change the cables every 6 months and that's way too often unless you ride mega miles or in bad conditions like muddy MTB conditions.

alcjphil

Downtube shifter derailleur cables should last a long time. The front derailleur cable that was installed on my 1972 Raleigh Professional never wore out in over 20 years of use. I only changed it when I installed indexed shifters and derailleurs

CliffordK

Are you sure that is true with friction shifters? You don't want to be throwing the chain. The pressure shouldn't be real high after shifting.

CliffordK

Is it possible to modify a 1.6mm brake cable to use as a 1.2mm shifter cable? Does it fit into the shifter? Perhaps either carefully cutting half the end off, or carefully filing it round to fit the hole. You'll know quickly enough if it doesn't work.

FastJake

I wouldn't bother modifying it at all. I'd just let the end stick out. It'll work the same, it just won't look nice.

FBinNY 

Yes, it's true, friction or index. There's room to set the limit beyond the point of perfect trim and still prevent overshifting. So, you overshift beyond where the trim position will be and settle back a hair.

So many people set the limit right about where the trim is right, and cannot overshift for a crisp shift and end up forcing the FD against the limit to get a shift.

My procedure for FD outer limit adjustment, is to shift via direct pulling on the wire, back off until I can dump the chain, then back in by degrees until I can't. Then no tighter than what's necessary to preventing the chain from dumping. That leaves plenty of room to work without forcing things.

FBinNY 

I'll save you the wasted effort. All the strength is in the larger section of the head. The extension is plain zinc and there only to prevent side exit from the fittings.

Inside the larger part of the head, the cable is frayed apart and formed into a "floret" resembling a tulip with the strands turned back to the center. When the zinc is cast around this, it forms a well supported structure than cannot be pulled apart.

There's nothing resembling this strand separating in the neck, so without the head attached, the pull out strength is minimal.

RandomTroll

I route as the instructions tell me: to the inside, the side closer to the frame.

How would I know without a torque wrench that small? The instructions tell me 5-7 N-m. I rarely over-tighten anything; as I said before I more likely get this bolt not quite tight enough. (Can the bolt bear much more than 7 N-m?) I've worried about how tight I've had to make it to get it to hold. The derailleur is at least 17 years old: could the surfaces have worn so as to cause this?

I can move the derailleur a further bit out when it's on the largest chainring; I need over-shoot to shift sometimes.

Zef

One thing to look at is where on the derailleur you are clamping the cable. Normally there is a washer/bushing on the bolt between the bolt head and the movement arm of the front derailleur....the cable should be clamped between the movement arm and the washer/bushing not between the bolt head and the washer/bushing. Clamping directly against the bolt head, in my experience, tends to lead to the bolt cutting the strands of the cable when clamping.

YMMV,
-j