"Streched' Gear Cables

[Greg29]

Why is it that every time a bike goes for a service the gear cables have to be replaced? Do cables stretch that much or is it just LBS BS???? As a kid I replaced (brake and gear) cables every 2-3 years.

[TNT1]

Bike shop BS. I only replace cables when they break.

 

Get a new bike shop, or learn how to do a basic service yourself.

[ThePubSA]

Its L..BS..

[RacerX]

Cables dont stretch, the casing is wearing in on the inside causing more movement then it should have. Metal cannot stretch, it will snap.

 

I work at a bike shop.

Cables do stretch, especially when they are new. You should not be working at a bike shop

[BLACKvoodoo]

All good answers

 

 

I think what is mistaken for 'stretch' is only the individual strands pulling tighter together.

Edited May 3, 2012 by BLACKvoodoo

[covie]

Cables dont stretch, the casing is wearing in on the inside causing more movement then it should have. Metal cannot stretch, it will snap.

 

I work at a bike shop.

 

Cables do stretch actually, but generally will stretch in the first week or two of new cables being put on. Then you just retention them and you should be good to go. I only use teflon cables as they stretch less and last a lot longer, and its only slightly more expensive than normal cables.

 

That said, new cables makes your bike easier to setup and tune, and thats why your LBS wants to put new cables on each time. It also forces you to come back to re-setup once they have stretched. So its double the business for them.

[Red Zone]

Most cables get replaced due to worn housing or dirt in the housing. Normally it is the portion of housing where the cable enters the rear derailleur that picks up the most dirt and also has the most extreme bend, and thus needs to be replaced. Easy to do it yourself, buy a coil of gear housing (it is different to brake housing) just remove the cable from the RD, whip off the old housing, wipe the cable with a dry rag to clean the cable, use the old housing as a guide, cut a new piece and slide it back over the cable. easy peasy and save yourself some cash.

[Minion]

Cables do stretch, especially when they are new. You should not be working at a bike shop

Cables do stretch. And then immediately return to their starting length once the load is removed. This isn't what causes the gears to slip.

The cables bed in to the housings, and the housings settle in to the stops.

[CBS]

So how much does your LBS charge for the new cable?

[ibruegge]

I have cycled since I was 8, had about 15 different bikes so far - and to this day I am still to see a cable snap. anything attached to it, bolts, etc yes, but have never had a cable break. I would say your LBS "is very careful to avoid that disappointment of a break down...". Too careful in my eyes.

[Mr SingleTrack]

here we go again, the cable stretch debate!

I am just interested to know which LBS the OP uses as in my experience there is a LBS in JHB that change cables like it's nobody's business. perhaps PM me so that this is not mentioned on the forum

[TNT1]

here we go again, the cable stretch debate!

I am just interested to know which LBS the OP uses as in my experience there is a LBS in JHB that change cables like it's nobody's business. perhaps PM me so that this is not mentioned on the forum

 

Bugger that. Tell us all, so we know to avoid the place.

[Christie]

Permanent stretch or lengthening of the cables is a BS story. How much load is exerted on a shift cable? I would guess around 1 kg at most (its thumb actuated, after all.) I'm pretty sure you could hang 20kg on a shift cable for a week/month/year and not change its length permanently by even a microscopic amount.

Shifting goes out because cables wear into new housings, and dirt accumulates in the openings of the housings over time, causing more friction when the cable moves.

[Eugene]

Cables dont stretch, the casing is wearing in on the inside causing more movement then it should have. Metal cannot stretch, it will snap.

 

I work at a bike shop.

Metal does stretch.

 

Take a piece of wire and bend it, it doesn't snap. The outside of that piece of wire is stretching, or getting longer. If it wasn't able to get longer, the wire would not bend.

Edited May 3, 2012 by Eugene

[Johan Bornman]

Cables don't become longer. They may stretch elastically and if yoiu're on a long cable, like a tandem's rear brake, you can actually feel it. However, like an elastic band, they return to their original length as soon as you let go of the brake/gear lever.

 

However, it is not the inner cable's length that is important, but it's length in relation to the length of its housing. The housing turns around corners and the inner works a shortcut on the corner insides. The housing has a plastic liner that eventually erodes, making the inner cable appear longer that it is supposed to be - to the "system" that is. In other words, your brakes require more travel to take or, your gears don't work as supposed to.

 

Further, dirt and eroded plastic makes the inner move with more friction, causing difficult gear shifts and on long rides, even tendonitis, if you are prone.

 

The practice of changing cables nilly-willy is one fuelled by greed.

 

However, you should change them if they don't move freely anymore. Only an experienced hand will know whether or not this is necessary. I say you should learn to assess your cable health for yourself.

 

Also, it makes sense to replace cables as a preventative measure. They do start to break inside the shifters due to sharp bends. If they break off, say in a Campy shifter, it is major surgery to remove it. If it breaks off in some STI shifters, it could mean a new shifter, as labour would cost a lot.

 

Healthy cables make your riding experience so much nicer.

 

Cables do not stretch or even settle in its windings. This is easy to prove since there is no lever on your bike or body long enough to take them into permanent stretch (yield). The science of winding cables has been perfected over the last 100 years and the windings are perfect, with no room for tightening.

 

Cables to avoid: Gore Ride On, Alligator and Jagwire coated cable and all other plastic coated cables. They're all rubbish and based on frying pan science.

[BLACKvoodoo]

Cables to avoid: Gore Ride On, Alligator and Jagwire coated cable and all other plastic coated cables. They're all rubbish and based on frying pan science.

 

Teflon DOES reduce friction, FACT