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13. Chains #4025 . Top

In my discussion of cassettes, I outlined that the chains are different sizes as you increase the number of cogs. For a 7-8 speed cassette, you need a corresponding chain. This chapter goes into the details of chains.

  1. Replacement
     When replacing a chain, you need to know the number of cogs on the rear cassette. The number of cogs determines what width of chain you need, because as you increase the number of cogs, the cogs get thinner and closer together. So chains are specified in terms of number of cogs. The most standard size is the 6,7,8 speed chain, which works on any one of those cassettes. 9 speed, 10 speed and 11 speed cassettes each have their own width of chain.

  2. Measurement Summary
     This is more detail of the above. It gets into what exactly is different about the different "chain speeds". First, as background, all chains have 1/2" pitch. The 1/2 refers to the length of each link, pin to pin. However there are three main widths. 3/32, 11/128 and 1/8. The 3/32, 11/128 and 1/8 refer to the width of the space between the inside sideplates. (called "Inner Width"). What makes a 9 speed different than a 10 speed chain is not the inner width, it is the construction and thickness of the side plates.

     - Multi speed chains from 5 to 8 have inner width of 3/32" (2.38mm)
     - Multi speed chains from 9 to 12 speeds have a width of 11/128 = 2.18mm

     6,7,8 speed 2.38 mm
     9-12 speeds 2.18 mm

    From BikeGremlin: Chains for one and multiple speeds differ from each other by the outer width. The more "speeds" a chain is designed for, the thinner the outer plates and shorter the pins are (and they protrude less) so the outer chain width is smaller (i.e. chain is narrower). Inner width of all the multi speed chains is almost the same with only single speed chains having a significantly larger inner width.

    See https://https://bike.bikegremlin.com/3555/bicycle-drive-chain-dimension-standards/] BikeGremlin Drive Chain standards[/a]

  3. Chain Widths and Pin width
     From the KMC and SRAM websites, you can see the pin width varies with the number of speeds. The thing that you want to know is the "pin width". There are a lot of sloppy specs on the web. The KMC Z51 box says pin width is 7.1mm and the KMCX8.93 is 7.3mm. When I measured the width with my vernier caliper it was .1 mm wider, the 7.1 measured 7.2 and the 7.3 measured 7.4. The boxes specify three things: Pitch 1/2 inch, roller width 3/16, and pin width 7.1mm.

    Below is a table summarizing the specs given on the KMC website.


      Sprockets Pin Length Weight 116) ---------------------------------------
     6,7,8 Speed 7 mm 330g
     9 speed 6 mm 272g
     10 speed 5 mm 257g
     11 speed 5 mm 243g

    From the above, you can clearly see that the more sprockets you have, the narrower the chain. A chain for an 11 sprocket cassette is only 5mm wide. Each increase in number of speeds increases the price by 50% or so. And above 8 speed, you can't reuse the master link. So you can't just take off your chain to clean it.

  4. Master Links
     Before 8 speeds, chains did not have a master link, you just pushed out the pin from any link with a chain breaker tool. However this often resulted in "stiff links" so with the 7 and 8 speed chains, they now include a "master link". The master link has special side plates such that when the adjacent rollers are pulled together, the pin comes out of the plate. To remove a 7-8 speed chain there is a special tool you want called master link pliers. The tool is Park MLP-1.2 which cost $25. (MLP is Master Link Plyers). On 7-8 speed chains the master link is reusable, so you can take the chain off and clean it if you want.

  5. Plating (What about SRAM chains)
     At MEC, I bought the PC870 for $28, but then when I checked my journal, I noticed I had only paid $15.95 for a a SRAM PC730 at Bike Doctor. What's the difference between PC870 and PC730? The answer is on the SRAM website: The PC870 is nickel plated, and with chrome hardened pins. Whether this makes much difference in lifetime I don't know. I guess nickle plated looks better, and might prevent rust, but I ride my bike often enough I don't have a rust problem. So why pay more?

    To get the chain page, use google "SRAM Chains" and go to https://www.sram.com/sram/mountain/component/chains, then scroll down to the 8 speed, then click on "Specs".

    Comparison Table

    Model     USD          Outer plate   Inner plate  Pin Treatment
    ------------------------------------------------------------
      PC 830 10.00 grey grey Standard
      PC 850 14.00 grey grey Chrome Hardened
      PC 870 19.00 nickel grey Chrome Hardened
      PC 890 33.00 nickel nickel Chrome Hardened

     

  6. Chain Lubrication
     Keeping your chain lubricated is essential. I notice a huge difference in how easy it shifts after lubrication. So we used to use oil. Yet oil picks up grit and quickly turns into heavy black grease. The gunk builds up between the sprockets, and in the derailleur, and even on your tires. The "experts" talk about wet lube and dry lube. Wet lube is for wet weather and sticks better. More like oil. It also picks up more dirt. Dry lube is "wax based". It doesn't pick up dirt as much, but has to be reapplied more frequently. Both of them are equally smooth when applied.

    I'm not a lube perfectionist. Mostly I'll just put a bit of lube on the chain, spin it a couple of times, shift gears to spread it around, and then go riding. The crudest lube strategy is to just use regular oil and take your chain off and clean it periodically in solvent. But taking it off is too messy and time consuming. So people look for ways to clean the chain without removing it. This is done using a chain cleaner tool. These have a clear plastic basin into which you put the solvent. Then you push the chain down into it and little brushes remove some of the gunk. (Search MEC.ca for "chain cleaners"). But that is still messy and I only did it a few times.

    The final solution is to lubricate with wax, not oil. This is called "dry lube" and comes in a squeeze bottle. In the past year, I did an experiment: I put on a new chain, and used "dry lube" entirely rather than oil. It is a wax based lubricant that doesn't pick up dirt. After a year, there has been zero buildup of black gum, and the chain runs as smooth as with oil. However, I tend to have to relube the chain every 40 km or so. Oil sticks much better, and Betsy went back to oil during the rainy season. But I intend to continue to use the wax lube. However, the inexpensive $12.00 chains I use tend to get cosmetic rust on the outer sideplates if the bike is out in the weather for days. My chain turned rusty looking. But once I applied more lube, it ran as smooth as ever. If I don't like the look of the rust, I could buy a slightly more expensive chain that is zinc plated.

    Here is a video where the guy makes his own wax based lubricant from candles, paraffin oil, and Xylene or mineral Turpentine. Oz Do It Yourself I'm not sure I'd go to the trouble, because the little $16 bottle I got at MEC lasted more than a year.

  7. Chain stretch
     Chains "stretch" and then wear out the cogs more quickly. The metal in the chain doesn't actually stretch, what happens is the road grit wears away the pins joining the links, allowing the links to stretch out in the space. Park tools makes a simple metal bar called a "chain wear indicator which tells you if your chain should be replaced. (Park tools CC-3.2) I've read articles that say the oil conveys the road grit into the chain links, which I suppose is another argument for the dry lube.

  8. How often to replace
     Most experts always say you should replace the chains as soon as they become stretched, and thus reduce wear on the cassette. Typically, you'll go through 2 or 3 chains before you need to replace the cassette. Never the less, what many people do is wait for the whole system to wear out so much the chain starts to skip, then have a shop replace the whole thing. This can be about $300. But that worn chain wears the cassette faster. As the chain stretches, it is being supported by fewer and fewer teeth. The cassette will last longer if you replace the chains more frequently. The notion that a worn cassette will wear a new chain faster is false because it is the grit that stretches the chain, not worn cassettes. So you can afford to change the $12.00 chain and stick with the old cassette if it still works.

  9. How much stretch
     In a year of commuting, Betsy's all season bike stretched her chain a whole link. The Park tool CC3.2 Chain Checker indicated the chain needed replacing for some time. But we ignored it, just intending to replace the whole drive train. But when I discovered inexpensive chains, we changed the strategy and started replacing just the chain as soon as the tool says.