What's the right way to pre-stretch cables on a new bike?

[polar8]

I used to work in a bike shop, and to prevent new bikes from coming back with skipping gears a few weeks after they were sold, we would pre-stretch the cables by shifting up with the wheels still. This would do a good job, but I always felt like it was stressing the shifter too much.

Is there a better way of doing this?

[deke505]

yeah ride your bike. Then take it in after a month of riding. That is the least stressful way.

[Trent R.]

the way you mentioned is the best...and only..... way to "stretch your cables"

the thing is, your cables are not really stretching...everything is just settling and getting tight.


shift it with the wheel still....don't crank the shifter down and you should be fine

[heyyall]

Teach the riders how to adjust the cable length using the barrel adjuster. Problem solved.

[shiggy]

I used to work in a bike shop, and to prevent new bikes from coming back with skipping gears a few weeks after they were sold, we would pre-stretch the cables by shifting up with the wheels still. This would do a good job, but I always felt like it was stressing the shifter too much.

Is there a better way of doing this?

Not really needed any more. I have not prestretched a cable in 15 years.

[ElwoodT]

I haven't taken a bike to the lbs since the 90's. I go to the co-op to use tools I don't own (mostly to press headsets) Learn how to fix and adjust yourself, problem solved.

[006_007]

I dont bother - but I guess you could use something like the item park offers:

Park Tool Co. » BT-2 : Cable Stretcher : Brake Tools

[mr2peak]

Pull on an exposed section of cable. This snugs down the cable ends and doesn't put any unusual stress on the deraileurs.

[Uncle Six Pack]

I used to work in a bike shop, and to prevent new bikes from coming back with skipping gears a few weeks after they were sold, we would pre-stretch the cables by shifting up with the wheels still. This would do a good job, but I always felt like it was stressing the shifter too much.

Is there a better way of doing this?

How much "stretching" do you really think you were doing with that move? I'd imagine your typical shifter cable could conservatively hold a few hundred pounds with damned near negligible "stretch" up to the point where it would begin to fail. If you really think you were doing some stretching, it is more likely you were seating the housings completely into their end caps and whatnot. Any other perceived stretching was likely due to flex in the shifter and deraileur mechanisms themselves.

Personally, I just trim with barrel adjuster as necessary. I also make sure that housing endcaps are firmly seated, housings are cut clean (not angled), etc.... no funky bends or kinks in cable. I don't think it has ever taken more than a half-turn on a barrel adjuster to straighten things out as they get settled after that.

If you really had a lot of people coming in with bikes with skipping gears from an apparent cable stretch, it is much more likely that they started adjusting things ham-fisted themselves (and perhaps wouldn't admit to it). I have seen more than one person fiddle with a barrel adjuster with several turns at a time, then wonder why the problem went from bad to worse.

[deke505]

To understand pre stretch we need to know why the cable stretches. The wire is not one piece but made up of several smaller strands twisted into on piece (see pic below). The stretch comes when the twists in the cable loosen making the cable longer. You can't make this happen just by pulling on it. It takes several pounds of pressure. The only true way of stretching is to ride the bike and the cables will stretch naturally, which is why most if not all bike shops off at least one year of free tune ups.

Like Uncle six pack said all pre stretching does is properly seats the housing in the ferrels and the barrels.

[DavyRay]

...
Like Uncle six pack said all pre stretching does is properly seats the housing in the ferrels and the barrels.

So right, both of you. Not stretching cables, but compressing sloppy housing ends and cable clamps.

[Mountain Cycle Shawn]

Cables have come prestretched for years now. If ferrels, housings and barrels are put together properly, there is no seating of them involved.

[ghettocop]

I'm at UBI right now, and the way they are instructing that it should be done is eight full cycles of shifting with the derailleurs in their slackest position without spinning the cranks, before indexing.

[GelatiCruiser]

Teach the riders how to adjust the cable length using the barrel adjuster. Problem solved.

This is actually good advice. If my LBS had tuning/cleaning/maintenance clinics, I would definitely go. The shop I bought my bike from gave me lifetime tuneups and regular maintenance, but I wouldn't have to bring it in to the shop if I could confidently do it myself. Maybe they like the foot traffic in the store...

[Ricko]

I'd say shifting the front and rear derailleurs to the position that puts most tension in the cables (front and rear in largest ring/cog) and park it like that. I don't like the idea of moving the shifters without moving the wheels to allow the chain to shift, seems like it would stress your derailleurs.

I like the idea of teaching the rider to tweak the barrel adjuster but let's face it, there are some people who are completely incompetant when making even the simplest adjustments that they will only make it worse if they fiddle with it. It's your duty to sift out the riders who have a clue...from the ones that are clueless

[karl555]

People worrying about pre-stretched cables on a new bike,I would of thought correct gear set up was more important.
Thought most bikes made these days come with pre-stretched cables?

[ncfisherman]

Turn the pedals, pull exposed cable all the way, stop turning pedals and release exposed cable. Pedal forward to return the derailleur and loosen pinch bolt to remove extra slack...done.

[Mountain Cycle Shawn]

People worrying about pre-stretched cables on a new bike,I would of thought correct gear set up was more important.
Thought most bikes made these days come with pre-stretched cables?

Cables do come prestretched now.