Jump to content

Broken Chain Again


DuncanCT

Recommended Posts

What make? It's always nice to have a powerlink on your chain - good to keep in tubby bag too!

 

I'll find out in a few minutes

Link to comment
Share on other sites

Re the chain breaking - just be sure to eliminate chain suck on the middle chain ring as the cause.

 

I always use speed links to connect my chains. Most 10 speed are reusable (YBN or KMC) but the Sram 10 speed does not have the indents on the side plates for the connecting pin to seat into and they do not recommended reusing them. If you use the Shimano pin to connect be sure to follow the instructions that come with the chain viz the direction. Check for any previously connected links and make sure that you keep the chain direction the same. A Shimano chain with a pin connection becomes uni directional.

Link to comment
Share on other sites

Re the chain breaking - just be sure to eliminate chain suck on the middle chain ring as the cause.

 

I always use speed links to connect my chains. Most 10 speed are reusable (YBN or KMC) but the Sram 10 speed does not have the indents on the side plates for the connecting pin to seat into and they do not recommended reusing them. If you use the Shimano pin to connect be sure to follow the instructions that come with the chain viz the direction. Check for any previously connected links and make sure that you keep the chain direction the same. A Shimano chain with a pin connection becomes uni directional.

This point has always confused me. Surely tension is tension, and acts equally in both directions?

 

(JB and Edman, your phones are ringing...)

Link to comment
Share on other sites

This point has always confused me. Surely tension is tension, and acts equally in both directions?

Yip, but Shimano chains now seem to have different outer plates with different profiles (as I found out when installing one the other day). I don't think it makes a difference to the strength, but putting it on the wrong way round could affect the shifting.

Link to comment
Share on other sites

If I am breaking my chain under incorrect shifting can someone please explain the mechanics of what happens?

Link to comment
Share on other sites

Also needed some advice please

 

I broke my chain twice in 3000km and, yes I’m pissed about it.

First time it broke on around 1800km and the second time on about 2900km.

 

After the first break, the shop fitted a SRAM quick link and to my surprise it broke the second time four links behind the quick link.

 

The first time when it broke I was on the small blade in front and on the second one nearest to the spokes, standing at the robot waiting for the green light, as soon as it turn green I pulled away and on the second peddle I almost hit the deck when it broke.

 

The second time I was riding slightly up hill, in the same configuration as the first time and then suddenly I hear this cluck-cluck sound and I thought it was my BB, I stop and inspect but couldn’t find anything wrong, climb back on and as I gave the first stroke it snapped, as I mentioned it broke 4 links from the first time.

 

The chain is 105 10 spd brand new out of the box and was fitted by the shop.

What chain should I get(any recommendation), and what do you guys and girl think(maybe a **** chain)

 

Rudi

Link to comment
Share on other sites

I haven't come across any chain that has just broken under load 'though I'm sure it can happen. Usually there is some underlying cause. It could be a poor pin connection. When the chain is joined with a pin the chain effectivly becomes uni directional as the direction of the pull should be such that the the outer plates on the link pull the connecting pin towards the chainwheel. If put on in reverse the and the roller pulls the pin towards the chainring the outer plates have more chance of splaying under force and the pin popping out. If you have to rejoin the chain at some later stage you should never replace the original pin but brake the chain somewhere else for the new pin. Be sure that the chain direction is correct for any existing joining pins if you decide to use a speed link later. Some chains have pins that can be reused if you need to remove the chain for servicing. This is often done at service. The effectiveness of this depends on how the chain was made in the first place but I wouldn't do it. It then becomes impossible to see where joins have been made. With the simplicity and reliability of speed links it is just not worth it.

 

It is easy to identify which is an added link pin by the marks on the pins from the manufacturing process or the chain tool used. If you know how many, if any, link pins are in your chain it makes the analysis of such damage easier. For me, speed links all the way. Makes for quicker and more accurate gear setting and cleaning/service.

Link to comment
Share on other sites

If I am breaking my chain under incorrect shifting can someone please explain the mechanics of what happens?

 

I may be wrong, but, the normal rule is not to change gears when putting strain on the drivetrain, ie, slack off a little and then do the chain.

 

The mechanism of the derraileur that does the shifting work is a parrallelogram(sic?????) As it moves left and right it keeps the jockey wheels aligned with the gears on the cassette. The chain is effectively "bent" to make the directional change. If this happens whilst pedalling with full effort the chain may get damaged and eventually break.

Link to comment
Share on other sites

When the chain is joined with a pin the chain effectivly becomes uni directional as the direction of the pull should be such that the the outer plates on the link pull the connecting pin towards the chainwheel. If put on in reverse the and the roller pulls the pin towards the chainring the outer plates have more chance of splaying under force and the pin popping out.

I'm not convinced that this is the reason.

 

A 105 chain link consists of two bushes that are press fit into the two inner plates, a roller that rotates freely on the outside diameter of these bushes, a pin that rotates freely on the inside diameter of the bushes and two outer plates that are press fit onto the pin.

 

In the top free length, the chain is under pure tension. The rollers carry no load and the force transmission (with outer plates leading) goes Outer Plate -> Pin -> Bush + Inner plate. With outer plates trailing, the direction is reversed, but the relative forces and stresses remain the same (Newton's 3rd Law).

On the free length section, direction does not have an effect.

 

At the top of the chainring (assuming all load is coming from one tooth), with the outer plates leading, the force transmission goes chainring tooth -> Roller -> bush -> inner plate. There is no force in the outer plate or pin (actually there will be some force since the load is spread across multiple teeth, but it will be less than the free length forces.

 

At the top of the cassette, with the same assumptions, the transmission goes outer plate -> pin -> bush -> cassette tooth. The reduced force benefits that the outer plate and pin gain at the crank are reversed when it reaches the cassette.

 

Overall, the net drive forces that the outer link and pin experience are the same regardless of direction.

 

If there is a valid reason for having the outer links leading, I suspect it has something to do with what happens to the chain when it passes through the derailleurs and under shifting.The FD in particular applies a sideways force onto the top free length section that is carrying all of the tensile load. If the shift plate is no symmetrically profiled, it might produce greater force in a leading link than in a trailing link.

Link to comment
Share on other sites

Just broke my second chain on my 3x10 XT group set. Both chains broke while pedaling uphill so i assume its to do with bad shifting.

 

I weigh 100kg but I have not had a chain break on my road bike so i assume it's not my weight.

 

What is best practice from changing gear and gear choice?

 

i think a couple of question have been forgoten about..

1) how often do you clean your chain?

2) how old is the chain?

3) how often do you oil your chain.. been mtb i assume it runs dry quickly like mine does.

4)do you keep your chain line as straight as possible

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Settings My Forum Content My Followed Content Forum Settings Ad Messages My Ads My Favourites My Saved Alerts My Pay Deals Help Logout