Friday, August 24, 2007

The Single Speed Chain FAQ

Traditionally single speeders used 1/8 inch BMX chains, since most single speed (SS) bikes are just 26" wheel BMX bikes anyway. Other reasons include the fact that SS track bikes and old BMX bikes had 1/8 inch cogs and chainrings and since 1/8 inch chains looked bigger than 3/32 chains they must be stronger. Also 3/32; 7-8 speed (or 11/128; 9-10 speed) multi-speed rated (MSR) chains are designed to derail, something you don't want to happen on a SS bike. It is also a misconception the 9, 10 and A second look however shows there had been a lot more R&D money thrown at MSR chains by Shimano and SRAM, so most MSR chains meet or exceed the tensile or "pull" strength of 1/8 inch chains. Since most single speed components available today come in 3/32, it seems logical to use 3/32 chains. On the other hand, while some claim that 1/8 inch chains on 3/32 gears cause more noise and wear than 3/32 chains, the jury is still out on this matter as many more use prefer this set-up. In the real world, it would seem the use of 1/8 inch chains work fine on 3/32 components and some, such as the SRAM PC-7 and KMC Kool chains are stronger.

One issue that comes up from time to time is the use of 1/2 links. The use of a ½ link allows you to vary the chain length by 1/2 inch intervals, rather than one inch with a standard link. This comes in handy when you are trying to convert a bicycle with vertical dropouts.

1/2 links come in two generic sizes, 1/8 and 3/32; they tend to be weaker than a standard link, so if strength is a major issue, you may want go with a half link chain. They add about 100 grams over a standard but they do not add a weaker link and they look kinda cool.

So do you need a single speed (non MSR) over a MSR chain? No, not really. Is there any advantage to a 1/8 inch chain? Yes, there can be if you have chainline and/or derailing problems, a SS chain can help; and as I said before some are stronger. However if you are using a spring tensioner such as this early Surly Singleator, an 1/8 chain may not work, as pretty much all tensioners are designed to work with 3/32 chains. Additionally if you're are having a problem with your Singleator skipping, they work best in the push-up mode, and with the addition of a zip-tie connecting the Singleator arm to the chainstay. The Singleator is the only tensioner with a push up "mode" (it requires a second spring that needs to be switched out). If you have another Singleator type tensioner, you can still use the zip ties but there will be no way to tension the spring (again they only work in one direction). Also, with the exception of the Paul Melvin, most tensioners are not designed to work with different size cogs using the same chain length. The Singleator manual says to shorten the chain as much as possible when using the tensioner (I would recommend using a half link if necessary). These tentioners skip due to a lack of chain wrap and tension, so anything you can do to increase either will help. Also make sure you have a cone wrench so you can tighten the spring as tight as possible.

The tensile strength of a SRAM PC-7 is about 2500 ft lbs and only come in 1/8 inch (and pimp gold); all other MSR SRAM chains (including the PC-58) are around 2023 ft lbs. The KMC Kool chains rate at 2860 ft lbs and come in both 3/32 and 1/8inch. The KMC Z chains (with an H in the model number) also come in both sizes (i.e. the 3/32 Z610H; my choice of chain), rate at 2640 ft lbs and are a bit lighter than the Kool chains. KMC ranks most if their MSR chains at 2314 ft LBS; I have not seen and published data for Shimano chains.

So what chain should you buy? There is a plethora of 1/8 inch chains out there; one of the favorites is the SRAM PC-7. On the other hand there has been considerable anecdotal information on the SRAM PC-1 (1/8) chain; the nickel plated version seems to hold up well but the non-plated version does not hold up well and should be avoided. KMC also makes a line of 1/8 inch (or 3/16 inch if you dare) and 3/32 SS chains. They come in various weights and strengths so you pay your money and make your choice. As far as MSR 3/32 chains go SRAM PC-58 seem to be popular with the anti-Shimano crowd as are the KMC chains. Shimano wise any of the better 7/8 speed HG or IG chains will work; The 9-10 speed chains may not work with some 3/32 cogs and chainrings. As elluded to before, they are slightly smaller than 3/32" @ 11/128".

As a final caveat there is the question of longevity aka "streaching". Regardless of what you hear, all chains get longer with use (I'd call that stretching). There are so many factors that go into this "lengthening", that it's futile to try and rank one chain over another. Just try and keep your chain clean and lubricated and when it has stretches 3/32" over a foot, replace it.

Also checkout and for some good chain spew.


? said...

3/32", Bushing-less, shifty chain is; flexy, sloppy, crap! Use it where it belongs, on bikes with dancing chainlines, and away from your SS!

Wearing My Tinfoil Hat said...

Great information, I have used as suggested the KMC Z610H. I use it on my internal gear equipped commuter and now on my singlespeed cross bike. The chain holds up well and I have never had a problem with skipping teeth. I also only use singlespeed cogs which have longer teeth. I use single and multispeed chainrings with no problem.