Very Old Shimano 7 speed replacement- Mtbr.com
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  1. #1

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    Very Old Shimano 7 speed replacement

    Greetings all,

    I have the need to replace my 7 speed drivetrain on my 15 year old Nishiki. What, if any, will be my options? Acera, Alivio????

    Thanks in advance,
    NFields

  2. #2
    tjl
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    Shimano 7-speed compatibility

    General rules with old Shimano indexed 7 or 8 speed:

    All Shimano components for the same number of speeds will match up index-wise, except for 7 or 8 speed Dura Ace. All Shimano indexing rear derailleurs move the samea mount for a given cable pull, except for 7 or 8 speed Dura Ace.

    If you have Shimano IG cassette or chainwheels (found on some 7 speed groups in the mid 1990s), use a Shimano IG chain, or a Sachs or SRAM chain that is listed as IG compatible.

    Shimano 9 or 10 speed chains are narrower than those used for 7 or 8 speed, so some combinations of 9 or 10 speed components and 7 or 8 speed components may not work so well.

    8 speed uses a slightly different sprocket spacing from 7 speed, but some people manage to get 8 speed shifters to work on 7 speed cassettes, using the floating top pulley in the rear derailleur to make it work. It is also possible to change the spacers on some Shimano 7 speed cassettes to match the 8 speed spacing for more exact shifting if you use an 8 speed shifter.

    Changing a 7 speed rear wheel to 8 speed involves replacing the freewheel body as well as the cassette, and redishing the wheel.

    Some SRAM parts are Shimano compatible, but SRAM shifters and rear derailleurs listed as having 1-1 actuation ratio are not Shimano compatible.

    Currently, Shimano only offers 7 speed shifters in Altus and Tourney. SRAM offers 7 speed shifters in its 4.0 and 3.0 lines; these are 1-1 shifters that require SRAM rear derailleurs.

    Loose Screws offers older bicycle components that may be of use in replacing worn out parts on older bicycles. Many bike shops that have been around for a while have older components in the dusty corners of their shops.

    Web sites:

    http://bike.shimano.com
    http://www.sram.com
    http://www.loosescrews.com

    If you only need to replace a worn out chain and cassette, you should be able to find a 7 speed Shimano cassette from Loose Screws or a bike shop, and a 7 or 8 speed chain from most bike shops. If your existing Shimano 7 speed shifters are ok, they will work; if you need to replace the rear derailleur, any Shimano indexing rear derailleur (except 7 or 8 speed Dura Ace) should index with them. If your shifters are worn out, and you cannot find Shimano 7 speed shifters, you may have to use an SRAM shifter and rear derailleur setup.

    If your worn out sprockets are UG (Uniglide) rather than HG or IG, Sheldon Brown's web site ( http://www.sheldonbrown.com ) mentions that you can just flip the gears over and they will work like new. Actually, you probably want to go to this web site and read all about what he has to say about Gears and Drivetrain before buying stuff for your older bicycle.
    Last edited by tjl; 11-26-2004 at 11:39 PM. Reason: add mention of Sheldon Brown's web site

  3. #3

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    Thanks for the very detailed information. My new shifter/brake lever combo are Acera as the old ones bonked out this year. I went ahead and updated the old canti brakes to the Deore "V" brake and they have much better stopping power. I was figuring the next thing to go would be the chain, cassette, crank, but my LBS owner used a tool to measure wear on the chain and pronounced it good to go. So, in light of all my gained recent knowledge, I shall continue to ride until the drivetrain rears it's ugly head in shiftability. BTW, the ders are the GS 200's, the cassette is hyperglide, and the cranks are biopace, as this was an entry level, recreational bike bought in 1990.

    Thanks again,
    NFields

  4. #4
    tjl
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    Measuring chain wear and other issues with old drivetrains

    Quote Originally Posted by NFields
    I was figuring the next thing to go would be the chain, cassette, crank, but my LBS owner used a tool to measure wear on the chain and pronounced it good to go. So, in light of all my gained recent knowledge, I shall continue to ride until the drivetrain rears it's ugly head in shiftability. BTW, the ders are the GS 200's, the cassette is hyperglide, and the cranks are biopace, as this was an entry level, recreational bike bought in 1990.
    The easy way to measure chain wear is to measure a part of the chain that does not have any slack in it with an inch ruler. 12" of chain should be measurable exactly pin to pin. If the pin at one end is lined up to zero on the ruler, the pin on the other end should be lined up to exactly 12". If it is 12 + 1/16" or more, replace the chain. If you ride on a worn chain too much, it will cause the sprockets and chainwheels to be worn to match the worn chain (and will not work properly with a new chain).

    Your current gears are probably non-compact drive -- i.e. something like 46/36/26 chainwheels, and sprockets starting from 12. In the mid-1990s, many Shimano components moved to compact drive -- i.e. something like 42/32/22 chainwheels, and sprockets starting from 11. Compact drive chainwheels require front derailleurs made for compact drive. Cassettes with 11 tooth sprockets may have some issues fitting on freewheel bodies made before 11 tooth sprockets were made. http://www.sheldonbrown.com has more on these issues. If you change the gears on one end of your drivetrain to compact drive, but leave the other end alone, you'll change your gearing range. If you want to change to round chainwheels without going to compact drive or changing your gearing range, you may be able to use a late 1990s Shimano RSX road triple crank with 46/36/26 chainwheels.

    If 7 speed parts ever become truly impossible to find, Sheldon Brown's web site does mention that it is possible to put a 9 speed cassette on a 7 speed freewheel body by leaving off one gear; used with 9 speed chain and shifters, it will work (but provide only 8 speeds).
    Last edited by tjl; 11-27-2004 at 11:13 PM. Reason: correct threshhold for chain wear is 1/16" "stretch", not 1/8"

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