Ferrules -- metal vs plastic
 

Hi All,

I've built up a few bikes now and have noticed that the shifting and braking seems to be be more precise when I used cable kits with metal ferrules (SRAM) vs kits with plastic ferrules (Jagwire).

I can see how plastic ferrules could potentially be more friendly to cable, but metal seems superior in terms of lack of compression.

Is it just the ferrules or is there more going on here?

I've done 3 bikes with Jaguar kits and 2 with SRAM kits. Whenever cutting a housing, I make sure that the end is squared off before installing a ferrule.

Thanks,
Bob

It's more about ferrule shape and fit than material. Ideally ferrules fit very snugly on the housing, and their OD corresponds nicely to the fitting.

The shape is also important both inside and out. For index housing the ferrule must have a flat bottom inside or the strands will be necked down at the end as they wedge into the cone, pinching on the wire. Brake housing is more forgiving because the coil can't be constricted the same way. On the ferrules outside, a slightly conical or curved bottom is preferable, for best pocketing into the fitting.

They don't look it, but quality ferrules are actually carefully engineered little bits, and the right ferrule can make a big difference.

Metal ones are brass with nickel plated, or stepped ones of aluminum.

never an issue.

You`ve got me on the SRAM stuff - haven`t personally used any of their kits. But I have used Jagwire extensively and they have a good half dozen different METAL ferrules available as individual items or included in their better kits as part of the package. Jagwire also makes the goodies that Shimano uses (cabling and ferrules so that should be some indication that the stuff works well. Plastic ferrules usually go on the smaller diameter shifter housing where stresses are less, but its becoming increasingly common to find Jagwire Ripcord compressionless housing used for both brake and shifter applications and metal ferrules are available with a variety of specialized features - O-rings, extended necks etc.

If you`re doing a careful installation any quality cable kit will do an excellent job. I`m finding people are getting fussy about other things now: "Is this available in red?"

Is it weird that I've never used the ferrules on the bikes I've built myself? And haven't had any issues braking, or replacing the housings after some years of use?

I've found that metal ferrules have a tendency to seize in the cable housing holder (don't know what it's called) after some time of non-adjustment.

Some frames have cable stops sized specifically for bare cable housing. If you've fiddled with a variety of bikes I'd be surprised if they all were, however.

One of the first design lessons I learned is that every single part, no matter how cheap or apparently insignificant, costs money. If it doesn't serve a valuable function it shouldn't be there.

Sorry that is outdated.

The latest SRAM and Shimano 10 speed 7900 series function much better with metal ferrules than with plastic. The latter of which is REQUIRED for proper shift performance. The force put through the housing results in imprecise wth standard plastic ferrules - they give under load.

A general statement that has no relevance.

On systems where using plastic leads to degradation of shift perforamnce, then yes metal is superior. Obviously.

I should qualify my last statement - this was for brake housing only. My bike has DT shifters so the only shift housing is the noddle at the RD (which came with ferrules already on it). I suspect that any slop in the brakes from not having ferrules would probably be insignificant, at least compared to slop in an indexed shifting system.

I'm also a believer in metal ferrules, but the blanket statement that they're superior to plastic because plastic gives under load is either hype or nonsense or both. The thickness of the base of the ferrule is typically 1mm or so. There isn't enough difference in the modulus of engineering plastics vs. steel or brass to create a measurable difference in compression under load.

Of greater importance is the shape of the bottom, fit, and evenness of the cut of the housing itself.

I want to be clear that I'm not saying that plastic is always as good as steel, I'm just saying that steel or brass isn't necessarily better per se.

BTW- good quality plastic index ferrules have brass thrust washers pressed into the base to provide a solid purchase for index housings, while many metal ferules have conical bottoms (inside) which causes problems.

I guess it kinda depends on the bikes and when you put them together. Those skinny chrome ferrules on spiral wound brake cable were largely cosmetic. Besides giving the cable a finished look - they had the added benifit of sealing that freshly cut wire inside the cable and provided a level of protection from rust. Ferrules on compressionless cables really aren`t usually an option. A few exceptions are the shifter ends of shifter cables where the adjuster usually doubles as a ferrule. The thing is - compressionless housing needs a precision interface to prevent strands from being squeezed through the braze-on opening. Its unusual for frame makers to go to that level of trouble.

And as FB has pointed out - theres usually more to a ferrule than meets the eye.


Maybe I should add that the biggest changes in ferrule functionality in recent years have been to address the needs of the mtb bikers and their demands for sealed cables. I guess if they didn`t insist in going out and playing in all that dirt - we wouldn`t a lot of this stuff.

Some of my clients are HEAVY/very corrosive sweaters. I will use plastic ferrules whenever possible to help keep the ferrules from binding/rusting to frame/brake adjusting barrels/in-line adjusters etc. No matter how much care you take building a bike -- in time without proper things happen. Never had a problem with brake or shifter operations as long as I used a ferrule (either metal or aluminum or plastic) as long as it fit snuggly over cable housing/cable passed thru ferrule/ ferrule fit whatever part of the bike it was put into. There are a number of people riding modern equipped bikes with non factory cable housing on their bikes.

The plastic ferrules on the down tube won't creak like the metal ones do if you ride in wet weather conditions.