When to replace a chain

The greatest loss of power due to friction that the bicycle will see (other than tire contact with the ground) is in the chain drive. A close look at this system is warrented by any rider looking to maximise performance.

I do not read German. If i did, I would explain THIS document from Rohloff. It is the most comprehesive study of chain wear that I encountered while researching this topic. It obviosly covers every base, but I can not read it. please contact me if you can.

Bicycle roller chains do not "strech", they wear. Each pin is surrounded by a bushing that develops some play when it wears. A chain is said to be worn out and replaced on it's own when it's average length (pin to pin) has increased by .5%. So for a half inch pitch chain, 9 links should measure 4.500 " when new and 4.523" when it is spent. If the chain's average length has increased by 1% (4.545") then the entire drivetrain gearing must be replaced. You can measure from the side plates as long as you add the increase in diameter. An artical on this subject is HERE, HERE, HERE and HERE. I am still working on the problem that worn rollers really do effect performance and wear on the system. Expect this discription to be modified once I fully understand what is going on.

Wipperman suggests that a chain has exceeded it's wear limit when the distance between 10 rollers measures 107.4mm. (4.228"), measuring using calipers angainst the inside of the first and tenth roller. Although this measure combines measurement of chain elongtion and roller wear, it is worthy of consideration since is is coming from a manufacturer. Theoretically this measure should be 106.5mm (4.194") without any wear in a perfect system. This means that either the roller IDs have worn .028", the chain has elongated .62%, or a combination of the two. We of course know that it is a combination of the two. Say Wipperman had decided that 0.5% was the limit of elongation, then the roller wear limit would be about .006". Note on the chart below that Shimano Dura-Ace exceeds this by a factor of 2. If I understood german, I could clear this up by reading THIS publication by Wipperman. (something about 3%?)

By comparison, I have a Park CC-1 Chain Checker Tool. At a reading of 3.25 where the blue zone changes to red, the measurement is 4.741", this of course based on 10 pins. This means that either the roller IDs have worn .037", the chain has elongated .74%, or a combination of the two. Again, say park had decided that 0.5% was the limit of elongation, then the roller wear limit would be about .012". An interesting note on the park tool and the numbers labeled on the face. They are marked in even segments of the dial. A student of trigonometry would realize right away that this must be a meaningless scale. This tool works from of the motion of a cam to guage distance change. If the dial had any real meaning it would be labled sinusoidal rather than evenly. It is not, casting doubt as to whether the designer actually understood what they were doing. The maximum reading on this tool is 9, where the combined elongation and roller wear is 0.148", well out of any usable range. The Park CC-2 is essentially the same type of tool as the CC-1 but designed to be easier to read and more accurate. Supposedly it reads from 0.25% to 1.00% wear, but that is impossible for this type of tool, leading to some speculation as to the validity of it's use. Funny as well, the designer has still to study sinusoidal motion.

The Park CC-3 is designed soley to measure chain elongation rather than including roller wear. It will quickly tell you if you have passed 0.75% and 1.00% elongation. This seems fine, if those are your only target points. At least it is only measureing one parameter. Their statement says that after 1.00% the chain should be replaced. I belive the rest of the drivetrain replaced at this point as well. This tool does ignore the concept of roller wear, which is fine, but I do belive that should be addressed as well as elongation.

Lots of people have been talking about Wippermann Connex Chains. These chains are amazingly expensive, but the 920 is about as cheap as they get (although the Connex 908 Nickel is probably the best). Previously I'd been running Shimano Dura-Ace/XTR chains. When the two are compared side to side, the wipperman comes out on top especially since the roller size is a little larger. Another source of Wipperman info is HERE

Chain Average Roller diameter Average Roller ID Oversize % Elongation (New) Special Features Price
Theoretical .3060" 0.000" 0%   ?
Shimano CN-7701 Dura-Ace .3015" 0.013" 0% Champhered plates $ 28.99
Wipperman Connex 920 .3030" 0.004" 0% teflon coated plates, Largest plate champher $ 39.95

General Chain Info:

Bicycle chains follow ISO 9633:2001 and JIS D 9417:1993 specifications for tolerances and specifications. US Tsubaki describes bicycle chains HERE. A quick reference to chain dimentions is HERE. Since a bicycle chain running in a derailure type configuration must allow for latteral movement, bushless chains are used. On single speed, or internally geared configurations, a bushing chain should be used.

KMC Chain Industrial Co. has a vast selection of chains. A spec chart is HERE.
SRAM/Sachs spec chart is HERE.
Rohloff's German website is HERE.
YBN Yaban Chain Industrial, Co.
ACS - Single speed chain
THC Bicycle Chains
Regina, IT
Wippermann Connex Chains

Chains for Multi-geared bikes should be bushingless type.
Chain 1/2" x 11/128" 1/2" x 11/128" 1/2" x 11/128" 1/2" x 3/32" 1/2" x 3/32"
Pin Length (mm) 6.2 6.5 6.6 6.8 6.8
Roller Width (mm) 2.2 2.2 2.2 2.2 2.2
Roller Diameter (mm) 7.75 (.306") 7.75 (.306") 7.75 (.306") 7.75 (.306") 7.75 (.306")
Gearing 10 9 9 9 9
Manufacturer Wipperman Wipperman ShimanoDura-ace Rohloff SRAM PC59

Chain 1/2" x 3/32 " 1/2" x 3/32" 1/2" x 3/32" 1/2" x 3/32"
Pin Length (mm) 6.8 7.1 7.2 7.2
Roller Width (mm) 2.2 ? 2.2 2.3
Roller Diameter (mm) 7.75 (.306") 7.75 (.306") 7.75 (.306") 7.75 (.306")
Gearing 8 8 8 6, 7, 8
Manufacturer Rohloff Rohloff SRAM PC61 Wipperman

Chains for single geared bikes should be bushing type. Sometimes used for 5 and 6 speed systems as well. Note existance of 2 major sprocket thickness applications.
Chain 1/2" x 3/32" 1/2" x 3/32" 1/2" x 3/32" 1/2" x 3/32" 1/2" x 1/8" 1/2" x 1/8" 1/2" x 1/8 " 1/2" x 1/8 " 1/2" x 1/8 "
Pin Length (mm) 7.8       9.2 10.2 12.2    
Roller Width (mm) 2.4       3.3 3.3 3.3    
Roller Diameter (mm) 7.75 (.306") 7.75 (.306") 7.75 (.306")   7.75 (.306") 7.75 (.306") 7.75 (.306") 7.75 (.306") 7.75 (.306")
Gearing 1?? 1 1?? 1?? 1 1 1 (BMX) 1 1
Manufacturer Wipperman IntraX707 ACS SRAM PC-10 Shimano
Wipperman KMC
Wipperman SRAM PC-7X SRAM PC-1

Performance single speed and BMX race bikes should run the Wipperman IntraX 707 Nickle chain or the ACS chain. They are designed for narrow type rings and sprockets, and it is a bushing style chain. The SRAM PC-10, I am not sure if it is bushing or bushless, so I cannot recomend it yet.

HERE is a nice artical on chain stiffness.

Single speed and BMX riders looking for the lightest possible setup could consider a ViKing titanium chain. At $275 it is not the cheapest chain on the market, but it is probably the lightest. Since it is not a bushingless chain, I do not think that it would be an upgrade on a derailure system.

One of my favorite chains is the KMC K810 KOOL Chain. It isn't light, but it looks like the business!

Remember that Shimano Hyperglide HG chains require the use of a special pin to connect the chain. HERE.



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