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Thread: 1/8 vs 3/32

  1. #1
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    1/8 vs 3/32

    so. what is deal with using a 1/8 chain on a standard chainring?

    i have a 1/8 rear fixie cog, a derailleur style chain, and a road chainring. what is the best way to get this all working - just going to a 1/8 chain?

    if they make 1/8 and 3/32 cogs, why don't they make 1/8 and 3/32 chainrings, or do they?

    thanx!

  2. #2
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    With the 1/8" fixie cog your going to have to run 1/8" chain because 3/32" chain will bind on the cog. I've had no problems running a 1/8" PC-7 on my fixie and SS using 3/32" rings and cogs.

  3. #3
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    My 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 (7-8-9 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 ˝ links. The use of a ˝ link allows you to vary the chain length by ˝ 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 are very plentiful in 1/8 inch and very rare in 3/32 inch.

    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 a 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. Shimano and KMC ranks most if their MSR chains at 2314 ft LBS.

    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.

    1G1G, Brad
    Last edited by aka brad; 02-10-2004 at 08:06 AM. Reason: clarity

  4. #4
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    whoa. nice.

    altho, you could have stopped after the "pimpy gold and it will work with your chainrings" bit.

    so then, a quick and lame=ass search for a gold PC-7 online nets me zippo. where can a fellow get such a beast from a friendly on-line seller?

    thanks again. tim

  5. #5
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    Listen! Here ya go for gold chains

    Quote Originally Posted by mon t
    whoa. nice.

    altho, you could have stopped after the "pimpy gold and it will work with your chainrings" bit.

    so then, a quick and lame=ass search for a gold PC-7 online nets me zippo. where can a fellow get such a beast from a friendly on-line seller?

    thanks again. tim
    That would be <a href="http://www.webcyclery.com/.docs/product_id/741/pg/product_details.html"> Webcyclery </a>.

    Brad

  6. #6
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    what size chain should I run on with a King cog and Jerricho Suffering up front? currently it's a Sram PC-1. let me know if I'm good, thanks.
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  7. #7
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    Nice-needs to be on SS FAQ!

    Quote Originally Posted by aka brad
    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 ˝ links. The use of a ˝ link allows you to vary the chain length by ˝ 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 are very plentiful in 1/8 inch and very rare in 3/32 inch.

    So do you need a single speed (1/8 inch) chain 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 a 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. Shimano and KMC ranks most if their MSR chains at 2314 ft LBS.

    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 MS 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.

    1G1G, Brad
    Nicely stated Brad and I hope Craig adds it to the FAQ.

    Tim
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