DyingAndDying

welp. Definitely my fault. Didn't see the gears at night. Cross chained or whatever, had my right on 5 and left 1. Heard like the chain make this noise. I'm just disappointed.​​​​​​

DyingAndDying

Also Chain is stuck between frame and the first gear. It's the 1-2-3 gear. Dumb gear cable ripped on me. It's Shimano. I know it'll unwind more and I have to replace it.

Maelochs

Crosds-chaining is not the issue likely .... sounds like bad derailleur adjustment. Your Low Stop screw should keep the chain from pitching off to the inside when the front cable breaks.

But, yeah. Replace the cable, adjust the derailleur properly, and after the cable stretches out in a few weeks, adjust it again, and you should be good for quite a while.

cxwrench

Cables do not stretch.

cyccommute 

Yes they do. There are even on-line calculators to calculate the stretch. There are also definitions for cable…more properly wire rope…stretch. There are two types: elastic and structural. Elastic is the elongation of the wires and structural is “caused by the adjustment of wires and strands, lengthening of rope lay, and compression of the core”. From the link


This exactly describes what occurs with bicycle cables. There is an initial increase in length and then none. The above link even says that 0.5% elongation for structural stretch is a good approximation. That’s 5mm for a meter long cable which is more than enough to throw off the indexing.

cxwrench

Here we go again...no, they do not stretch on a bicycle. This has been discussed thousands of times. If you think they do, on a bicycle, prove it. And not w/ a chart. Physical proof.

cyccommute 

You haven’t said where you see the individual strands. Most often they are at the pinch bolt and are usually caused by over tightening that bolt. If you are seen wires at the shifter, that’s a different issue and comes from the constant bending of the cable over the shift mechanism. Some shifters are worse at this than others.

I wouldn’t, however, say that a broken cable is due to cross chain shifting. That’s a problem for the chain, cogs, and chainrings but not for derailer cables.

cyccommute 

Not a chart. A table. But you do know how tables are developed, don’t you? People go out and make measurements and do calculations and make more measurements. Wire rope stretch is a known, studied, and well defined phenomena. And that not just by bicyclists. The article and calculator I linked to are not about bicycle cables. It applies to any wire rope.

As for “physical proof”, I’ll refer you all the bikes that need cable adjustments after installation of a new cable. And, no, I’m not talking about cable housing. Put a new inner cable in old housing and the cable will need adjustment for cable stretch in relatively few miles and then won’t need it again. Almost like there’s an initial stretch followed by a long time of being stable.

Snowflake6

Well, if you'll take anecdotal evidence...
1. Replaced the rear shift cable on my 105-5700 Cannondale early last year. Perfectly adjusted when installed, two rides later was shifting off-center and had to re-adjust. Haven't touched it since.
2. Built a vintage Cramerotti late last year, with Campagnolo mech and Jagwire cables. Perfectly adjusted both front and rear shift cables. Had to adjust the rear one ride later, the front two rides later. No adjustments since (but to be fair I did hang it on the wall after riding it for a month or so).
3. Built a new carbon gravel bike this fall. Chinese frame with 105-7000 series groupo and again Jagwire cables (what can I say, Shimano only offers black...). Rear hasn't needed adjusting yet, front has been adjusted once and needs one more tweak. While these cables are mostly internal, I ran housings full length for better cable protection overall on gravel.

I may accept that it's not the cable that's stretching, but there must be a mechanism that's letting the cable appear to slacken not long after it's installed. What do you say is that mechanism, if it isn't the cable stretching?

cxwrench

Since you believe so much in the 'table', use it and figure out how much stretch happens. Don't forget to accurately measure how much force it takes to move a derailleur.

kahn

Actually, it is not cable stretch - the bike is shrinking!

But I have to admit that I don't see how a rather robust item like a chain can stretch. Again, maybe the bike is shrinking!

Bmach

Snowflake6

LOL!

Read the discussion again... not CHAIN, but CABLE. Cables can, and do, stretch. Chains do as well, but by so small an amount i'd be surprised if you could measure it... And you'd never notice it when riding because the derailleur would take up the slack anyway.

Snowflake6

Since you believe so strongly that it's not the cables stretching, what is the mechanism by which new cables need to be adjusted not long after they are installed, and then usually don't need adjusting again?

DyingAndDying

Thought I just had to remove the crank or whatever to access the chain to place it back on the gear. and put the chain back in the gear. I have to adjust this limiter screw or whatever I don't even know where that is at. I heard about the limiter not letting the chain fall off in between the frame. Can I tape up the strands that loose it's at the end of the Shimano cable

SalsaShark

I believe the cable needs to form to the bends it must take within the shift levers when being used after a new cable is installed. These bends eventually are worked into the memory of the cable, and can be seen it's upon removal from service, as the cable is no longer straight when pulled from the shift mechanism. This is why an integrated shifter will seem to need more adjustment after cable replacement vs. a downtube shifter - there is less intracacy in it's routing with fewer, less aggressive bends. The cable is not really stretching, but merely forming and bending across all leverage points.

It is similar with a guitar string and tuning machines / bridge assembly. I will always 'stretch' the strings manually to help with tuning stability on a new set of strings, but am well aware that the strings are not actually getting longer, only settling into position as more tension is applied than what is typical during playing, thus expediting the settling process, and increasing tuning stability.

VegasTriker

Unless you simply hate picking up a tool or two and doing your own maintenance there are few excuses for doing it wrong these days with all of the YouTube videos out there, Look for the one that matches the type of shifters on your bike, example: Gripshift gear cable replacement (the most difficult one to replace) My bar end shifter cables are much easier and take about 10 minutes max.
The two websites that are most often cited for elementary maintenance are the Park Tool site already mentioned by Maelochs and the Sheldon Brown website https://www.sheldonbrown.com/ Both will teach you how to adjust the limit screws on derailleurs so the chain doesn't get wedged between the frame and the wheel or go off the chainrings (your "1,2,3 gears"). Buy a cable and fix it yourself as that will a lot less expensive and will get it fixed right away versus taking the bike to a shop, leaving it for a time, and returning to pick it up. You can buy expensive cables but in my experience the standard stainless steel gear cables are just fine since I usually get around 3K miles between replacements. If you intend to ride a lot and replace cables over the years it pays to buy them in lots of 10 for under $10 with free shipping on eBay https://www.ebay.com/itm/402262687206 versus buying just one for $6. No bike shop can match the online prices.

kahn

Oh, I knew we were talking about CABLES. But my comment was directed at CHAINS since they seem made of much stronger materials and, I guess, according to some, cables stretch was their windings can kind of, well, unwind. But chains are linked together pieces of metal. And, I understand, chains to stretch since they sell gauges to measure them before they damage the cassette.

dedhed

Chains do not actually "stretch" but wear on the pins and rollers lengthens them.

dedhed

This is probably a more realistic cable stretch calculator for bicycles than the link.

https://www.spaceagecontrol.com/calc...bmit=Calculate

Maelochs

Maybe no one else has ever had their cables seem to stretch. And i don't care what vocabulary people choose to describe it.

Whenever someone says, "Trust me, not your lying eyes" I know either the speech or the speaker is a joke.

denaffen

Next you’ll tell me guitar strings don’t stretch either.

cyccommute 

Okay. Using Loos & Co table of constants and the formula, a 1.2mm cable has an elastic stretch of 0.17mm with a 2 pound pull and 0.8mm with a 10 pound pull. I don’t believe that derailer pull is as high as 10 lb but I think 2 lb is a bit low. Elastic stretch of almost a millimeter would probably be too much for the precision required for index shifting.

Loos & Co also says in that link

1% of, let’s say, a meter of 1.2mm cable would be 10 mm. I’m not saying that cables on bicycles stretch 10mm and most modern bicycle cables will claim that they are “prestretched”. Bethlehem Elevator Rope actually gives some information on construction stretch for elevator cables. Unstretched cables have construction stretch from 4” to 6” per 100 feet for a 6 strand rope (close to the same construction of a bicycle cable but much larger). Prestretched cables have construction stretch of 1.5 to 3” per 100 feet. A quick calculation shows that is a high of 0.5% for the latter and 0.25% for the latter.

Applying that to a meter of 1.2mm derailer cable give 2.5mm for a prestretched cable and 5mm for unstretched cable. Taking up 2 to 2.5 mm of slack out of a new cable isn’t out of the ordinary.

The TL;DR is that both elastic and construction stretch are well known, well documented, and, in the case of elastic stretch, easily calculated.

cyccommute 

First…and this will likely drag the discussion further off topic…you don’t need to adjust the limit screws. Did the chain fall off the smallest gear and get stuck behind the crank or is the chain stuck between the chainstay and the crank? If the former is the case, it is likely that the angle of the chain in the combination you were using caused the chain to miss one of the teeth which knocked the chain off to the inside.

If it is the latter, it is likely that you suffered “chain suck” which is when a burr on the smallest chain ring doesn’t allow the chain to release smoothly on the bottom of the gear and “sucks” the chain upward where it jams between the crank and the chainstay. In both of these scenarios, you can’t stop pedaling fast enough to prevent the chain from jamming. It has nothing to do with the cable nor does it have anything to do with the limit screws.

Often you can get the chain unstuck by pulling on it but sometimes it can get jammed enough that crank removal is required. Pulling the crank isn’t the hardest job to do but it does require some tools. If you have the tools and you’ve pulled a crank before (or seen it done on video or in person) and you can’t get the chain out any other way, pull the crank. Alternatively (and perhaps easier) see if you can loosen a chainring bolt or two which will loosen the grip the gear has on the chain.

No. No you can’t. Did the end of the cable fray or did strands break on the shifter side of the pinch bolt on the derailer? If the cable just frayed, you may be able to wind the strands back into place by twisting the end of the cable so that they lay down again. If there are loose strands on the shifter side of the pinch bolt, the cable is broken and needs to be replaced.

Pictures would help.

dedhed

Like most quality cables 300 series SS, pre stretched.

1.2mm dia/33 length/5# pull

Elastic stretch - 0.23mm, 0.027%

​​​​​​https://www.spaceagecontrol.com/calc...bmit=Calculate