Chain stretch

[LegendRider]

I received the following email (less the graphics) from Cantitoe Road.

CHAINS STRETCH!

Fort Collins, CO – While it is axiomatic that “chains don’t stretch…they wear” and that worn chains are longer than new chains because of pin and roller wear, chains actually DO stretch when loaded!

Wippermann recently tested a number of popular 10-speed chains for stretch under load. For a reference point, each chain’s length was measured under a nominal load of 10 kg. Then each chain was measured under 75kg and 150 kg loads, and the results recorded. Not surprisingly, chains with cut-out plates and hollow pins stretched more than those with solid plates and pins. And, the chains that stretched least were the Wippermann’s Connex 10 series with solid plates and pins!

How much a chain stretches under load affects how quickly the load is transferred to the driven cog. The less stretch, the more responsive the bike becomes. And, less stretch means less energy is lost to stretching the chain! Especially in sprint, time trial, or hill climb events, reducing these losses is critical.

Wippermann tested 31-link sections of chain. This is the average number of links under load between chain ring and cog. While the actual amount of stretch is small (from 1.10 to 2.15 mm) the differences are substantial. Among the various chains tested, the “stretchiest” stretched almost 100% more than Wippermann Connex!

Why does Wippermann Connex fare so well against competitors? In addition to raw material and proprietary heat-treating processes, the SHAPE of Wippermann Connex outer plate is largely responsible for its resistance to stretch. Note that chains featuring elaborate side-plate cut-outs and hollow pins are the “stretchiest” while chains with solid plates and solid pins stretch less. But even solid-plate solid-pin chains with sculpted “figure 8” outer plates stretch more than Wippermann Connex. The extra-strong rectangular outer plates on Connex chains contribute significantly to their resistance to stretch.

In summation, chains DO stretch. Stretching reduces performance. Wippermann Connex chains stretch less than any other bicycle chains on the market!

[AngryScientist]

so wipperman conducted some test where their chains won? what a surprise!

[LegendRider]

so wipperman conducted some test where their chains won? what a surprise!

I'm more interested in the idea that chains stretch measurably under load than the rankings.

[biker72]

It would be interesting to me to know which brands of chains were tested.

[jhat]

Something I do not get is how energy can be "lost" due to a stretching. If the chain is stretching during maximum load, then the energy must be returned when the load is reduced. So, perhaps, the bike is slightly less responsive, but not any slower as energy cannot be destroyed and I do not think it is going up in heat.

[oldpotatoe]

so wipperman conducted some test where their chains won? what a surprise!

They also don't fit into my Park Chaintool..not a fan.

[firerescuefin]

Some people love Wipperman chains.

I ran their SS chains...until I had one catastophically fail during a sprint....sending me over the bars and breaking my wrist and collarbone. The chain had about 500 miles on it....did not break at the master link....and no, it was not soaked in anything. LBS (after the fact) said he did not recommend the SS version for exactly that reason....they don't stretch, they fail.....at least it did in my case.
Have been very happy with Campy and KMC for Record 10 application.

[Kontact]

What kind of stretch? Permanent or elastic?

Is a 75kg load one that a chain sees very often? At the loads chains do spend most of their time under, how great was the stretch difference?


This test may demonstrate a fundamental difference between chains, or it may demonstrate the reason that light chains can get away with cut outs - because it takes forces beyond what is normal to demostrate a real difference.

If I was Davis Phinney (or insert whichever large, powerful sprinter you prefer), I'd consider the Connex. But everyone else may be spending the extra weight on strength where it isn't needed.

That said, I've been using a Connex on my SRAM stuff - good chain.

[Lifecycle]

Chain stretch or do they just get sloppy due the linking together and material wear and tear as all bearings and such man made items of this sort do as they are used over time.

what is point of their test but to push their product - which I am not saying it is a bad product. shouldn't they say and maybe did and I missed the point - that there product is the better of chain materials out there - maybe they did and I just answered my own question .. Huh.......

[Peter P.]

My chains don't stretch; they practice yoga and last much longer.

[Dave]

There's a difference between elastic deformation, which is the stretch that Wipperman is measuring and plastic deformation, that is permanent and not something that normally occurs with a bike chain.

The term "stretch" is often used to describe the elongation that occurs due to normal wear on the pins and bushings. It only takes .0025 inch of wear on each pin/bushing to add up to 1/4 inch over the full length of the chain, or .5%.

Yes, Wipperman chains are beefier and heavier, but I've also credited the lack of an hour-glass shaped outer plate for the extra noise.

I'd have to see some details of the testing to believe that there is any power loss from the minor elastic deformation.

Wipperman has alos performed exaggerated wear tests and come up with results that are totally unlike what I've found in real-world chain wear tests. I found that Campy chains elongated at a rate that was about 1/4 that of Shimano, but their tests did not.

[jlwdm]

Dave

Good to hear from you - we have missed you. Are you riding again? Is your knee (I think it was your knee) doing better?

Jeff

[John M]

I've used a few wippermans along with several SRAM, Shimano, and Campy chains over the years. I will not buy another wipperman chain.

[LegendRider]

http://www.cantitoeroad.com/uploads/images/Newsletter/2011/Elongation-Data---ConnexVcompetitors.jpg

[RPS]

I'm more interested in the idea that chains stretch measurably under load than the rankings.
Doesn’t practically everything loaded in tension stretch? The question is only to what degree, and whether one has the instruments to measure it. If you ran a motorcycle chain on a bike it would still stretch. Just not as much.

And for what it’s worth, I’m 100 percent certain Dave is correct in stating that they mean stretch in the elastic range – meaning the chain returns back to its original length when unloaded.

[RPS]

.....snipped......
Is a 75kg load one that a chain sees very often? At the loads chains do spend most of their time under, how great was the stretch difference?


This test may demonstrate a fundamental difference between chains, or it may demonstrate the reason that light chains can get away with cut outs - because it takes forces beyond what is normal to demostrate a real difference.
.....snipped.....
For what it’s worth, even a “weakling” can easily load a chain to fairly high tension loads – well above 75 KG (that’s only 165 pounds) depending on gearing. A 150 pound rider like me when climbing a steep grade can stand on the pedal and barely move up the hill; hence maximum chain load is at least proportional to crank length compared to small chainring radius. When riding 172.5 cranks and 30T granny the pedal force can create chain tension about 3 times as high as I push down (plus also pull up on opposite side) on pedal. Plus maybe a little extra from pulling up on bars right before you fall over. I can easily see 500 pounds or more of maximum chain tension.

Having said that, I don’t see how it can matter in any significant way. The numbers are too small and elastic energy is returned during the pedal stroke. I’m not saying it helps like those who have argued that frame flex can make pedaling more efficient, just that it won’t hurt enough to worry about it. In this case the amount of stored energy is so minute that it’s insignificant. Plus for the most part it’s returned as useful work anyway.

[firerescuefin]

So from the engineers out there, does it make sense that the Stainless Steel chain would be prone to more catastrophic failures? As mentioned previously, LBS as well as others on the internet had had seen similar type of failures. As a non engineer thinking about it theoretically, it would seem that the harder metal would tend to be more brittle in this application, similar to 6.4 ti tending to crack in certain applications rather than 3.2 whose properties are better for the same application. Know I may be way off.

[Jack Brunk]

OK,
I had a 32 front 20 rear set up for the Whiskey 50 off road yesterday. I had the local single speed guru change the rear cog to a 22 and add a new chain so I could change cog/chain as a package. So today after a epic race my chain is sagging when it's in a static state(in all high/low). It is longer no?

[brians647]

<snipped> Plus for the most part it’s returned as useful work anyway.

When/how is it returned?
I ask because, assuming constant load (which never happens), it would seem that the chain would only be unloaded once it's on the chain ring, and at that point any contraction just makes the rollers move on the teeth.
I'm probably off, but I'm trying to picture when the energy is returned.

[Birddog]

The SS Wipperman failures were well documented. I had one fail too. It was explained to me that Wipperman had a bad batch of stainless that led to the problem. Mine was replaced under warranty (with regular steel per my request). It was not due to any inherent problem with stainless, just a particular batch.

[Kontact]

For what it’s worth, even a “weakling” can easily load a chain to fairly high tension loads – well above 75 KG (that’s only 165 pounds) depending on gearing. A 150 pound rider like me when climbing a steep grade can stand on the pedal and barely move up the hill; hence maximum chain load is at least proportional to crank length compared to small chainring radius. When riding 172.5 cranks and 30T granny the pedal force can create chain tension about 3 times as high as I push down (plus also pull up on opposite side) on pedal. Plus maybe a little extra from pulling up on bars right before you fall over. I can easily see 500 pounds or more of maximum chain tension.

Having said that, I don’t see how it can matter in any significant way. The numbers are too small and elastic energy is returned during the pedal stroke. I’m not saying it helps like those who have argued that frame flex can make pedaling more efficient, just that it won’t hurt enough to worry about it. In this case the amount of stored energy is so minute that it’s insignificant. Plus for the most part it’s returned as useful work anyway.
Right. But I did say "load that the chain spends much time under", which isn't climbing. I'm saying that, if you're worried about overall efficiency you don't need to look at peak loads but average loads, which at 90 rpm are pretty small.


Firerescuefin,

Stainless is generally thought to be less strong than carbon steel that was made purely for strength and not also for corrosion resistance. There are some great stainless alloys now days, but adding chrome does not generally make the alloy stronger, despite high hardness. But as the best spokes are SS, it can't be much of an issue for chains.

[RPS]

Right. But I did say "load that the chain spends much time under", which isn't climbing. I'm saying that, if you're worried about overall efficiency you don't need to look at peak loads but average loads, which at 90 rpm are pretty small.


Sorry, I thought you were asking a question, not making a statement. Some times it's hard to tell the difference if you word a point of view in the form of a question. May not be clear to others.

[RPS]

When/how is it returned?
I ask because, assuming constant load (which never happens), it would seem that the chain would only be unloaded once it's on the chain ring, and at that point any contraction just makes the rollers move on the teeth.
I'm probably off, but I'm trying to picture when the energy is returned.
I’m glad you are thinking in transient terms instead of limiting your thought process to steady state. :beer:

If the chain stretches in the elastic range, it’s mostly proportional to pedaling forces which are intermittent throughout the pedal stroke. As an example, think in terms of cyclist pedaling the small 39T ring. Loads go up to higher end of range while pedal is near the 3-oclock range, but then decrease to low end of range by time pedal nears the 6-oclock position. But that quarter revolution represents about 10 teeth, right? Of the 30+ chain links between the cassette and chainring, most will be “stretched” and then relaxed while in mid air. Any stored energy associated with chain stretch (which is very small in the first place) of all the links in mid air will be returned like when a spring is stretched and then the load is reduced. I’ll try to estimate magnitude later if I have time to kill but I’d bet it’s pretty small.

Additionally, the amount of stretch on a per link basis is even smaller than numbers in report. If I recall correctly, the first few teeth of a chain carry the vast majority of the load, so there is always some relative elastic deformation between chain and sprocket anyway. In the case of a stiffer chain, does that inherently make the drivetrain more efficient? Maybe slightly, but in my opinion only if it could reduce friction between the chainring sprocket teeth and chain compared to what would have occurred due to greater elongation. Whether that happens or not I’m not sure, because in theory the differences can be absorbed within the elastic range of deformation of the aluminum ring. And as long as there is little sliding friction which consumes energy, elastic deformation returns most of the energy just like a spring does.

We should also remember that in theory a small amount of stretch is not necessarily a bad thing. It may (or can) make the drivetrain run smoother.

[Kontact]

Sorry, I thought you were asking a question, not making a statement. Some times it's hard to tell the difference if you word a point of view in the form of a question. May not be clear to others.
Well, it was a question. And you partially answered it by saying that it only happens when out of the saddle. Do you think that happens very often that it would effect the net efficiency of the system?

[RPS]

Well, it was a question. And you partially answered it by saying that it only happens when out of the saddle. Do you think that happens very often that it would effect the net efficiency of the system?
I didn’t state or mean to imply that it only happens when out of the saddle. I used that as an example to demonstrate that even a “weakling” like me can stress a chain higher than in the tests. I’m sure professional sprinters can stress the chain pretty high too even when pedaling a 53T big ring. The thing to keep in mind is that normal chains are capable of handling even higher loads than most of us can exert even when riding a triple up a 20 percent grade. For example, I know a fairly heavy couple who rides a tandem with a small ring under 30T in size, and when they climb +/- 20 percent grades the chain doesn’t snap in two. That tells me that chains normally have a yield point much higher than what I, or even professional riders, can apply.

As to efficiency, I expect the affect of chain stretch is fairly consistent and therefore approximately the same most of the time. At light loads stretch is proportionally less but keep in mind that the amount of power being transmitted is also less, so its affect on efficiency (on a percent basis as normally measured) would be somewhat similar. If you look at the data you’ll see that stretch approximately doubled when loads were doubled. That’s completely expected.

As I stated in post above (or at least tried), I'm not completely certain if chain elastic stretch will necessarily decrease efficiency at all. I am, however, certain I’m not going to personally consider the efficiency angle when buying my next chain. I see it as a non-issue. I’d bet that other factors like chainline and sprocket sizes make a bigger difference than whether a chain is a little stiffer or not. Unless I’m wrong. ;)

[ergott]

I think this would be most important to cassette and chainring wear. The more they stretch under load, the more the chain is hitting the teeth instead of the valley in between.

Just a thought.