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  1. #1
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    1/8" or 3/32" chain?

    I've seen a few postings in this forum posing this same question, but none of them have answered the question of whether or not running a 1/8" chain on a 3/32" drivetrain is detrimental. Does anyone know for sure? I just built my singlespeed and put a 1/8", supposedly singlespeed specific, chain on it and would hate to trash the chain ring or freewheel by using the wrong chain.

  2. #2
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    My chain rant...

    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 (7-8-9 speed) multi-speed rated (MSR) chains are designed to derail, something you don't want to happen on a SS bike. A second look however shows there had been a lot more R&D money thrown at MSR 3/32 chains by Shimano and SRAM, so most 3/32 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 1/2 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 have always been very plentiful in 1/8 inch and now available in 3/32 inch by spicercycles.com and KMC (i.e. AEBike.com).

    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 tensioner such as the early Surly Singleator a 1/8 chain may not work.

    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. 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 speed and especially the new 10 speed chains may not work with some BMX cogs and SS chainrings.

    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 1/8" over a foot, replace it.

    Also checkout http://www.63xc.com/gregg/gregchai.htm for some good chain spew.

    1G1G, Brad

  3. #3
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    I agree with Brad and would recommend running a 3/32" chain with a 3/32" drivetrain, unless some factor disallows this option (i.e. the need of a half-link to compensate for vertical dropouts, etc.). 1/8" will probably work best if both your freewheel and chainring are also 1/8".

  4. #4
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    thanks

    I appreciate the chain rant. I prefer not to take any chances on ruining my brand new white industries eno crank chain ring, so I will probably be getting a 3/32" chain to replace the 1/8" chain I have on there now. Thanks again aka brad and johnroyale for the responses.

  5. #5
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    To answer your question directly, neither chain will harm your chainrings or cogs.

    Brad did a great explanation of the differences between the chains. I'll also share my anecdotal experiences. I seemed to get a lot more life out of the one PC-7X (wide) chain than I usually do out of the PC-58s I usually use, but again this observation is based on a single chain. My experience has also been that (despite having been designed to shift) the PC-58 seems much less likely to accidentally derail than the PC-7Xs I've ridden on both mine and borrowed bikes, and seems far less sensitive to slack tension or poor chainline. You'll hear strong opinions on both sides of this issue from the board, so take that with a grain of salt - but that's my experience.

  6. #6
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    1/8" chains Look far better and are dirt cheap.
    Can't imagine they would do any damage to chainrings etc as they are the same pitch.

  7. #7
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    I contacted white industries and ACS by email and posed the question to them. Both replied that using a 1/8" chain on a 3/32" drivetrain is okay and should not cause any damage to the chain ring or freewheel. So anyone else that was wondering can put their mind at ease.
    And again, thanks to all those who responded. All feedback was appreciated.

  8. #8
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    Quote Originally Posted by ssbn742
    I contacted white industries and ACS by email and posed the question to them. Both replied that using a 1/8" chain on a 3/32" drivetrain is okay and should not cause any damage to the chain ring or freewheel. So anyone else that was wondering can put their mind at ease.
    And again, thanks to all those who responded. All feedback was appreciated.
    Thanks for the research ssbn! I'm sure everyone on this board appreciates it. It's cool to hear an answer from the source.

    BTW, does ssbn stand for, "single speed butt naked?"

  9. #9
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    No, but is does now.

  10. #10
    Am I getting too bulky?
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    Cool-blue Rhythm

    Quote Originally Posted by johnroyale
    BTW, does ssbn stand for, "single speed butt naked?"
    Even cooler SSBN = Ship Submersible Ballistic Nuclear

    I gotta roll, can't stand still, got a flame in my heart, can't get my fill.

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