9 speed shifter w/ 8 speed cassette ?

Discussion in 'The Workshop' started by mtbdad, Apr 28, 2009.

  1. BoingBoing

    BoingBoing Team Sisyphus

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    What I find ironic is the fact that Sheldon Brown posted http://sheldonbrown.com/derailer-adjustment.html#alternate explaining how to make a 9speed shifter work with an 8speed cassette. I wouldn't recommend it to the OP because it will be easier to do everything at once.

    It's just funny how we can get so worked up about some of these issues. Not funny ha-ha, funny sad.

    But more to the topic, grip shifters are much cheaper than trigger shifters. If your wife likes the current set-up, you can get top-o-the-line grip shifters for the price of marginal trigger shifters.
     
  2. DISCO

    DISCO Banned

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    I've got some rallied Deore 9spd pods you can have, or some to think of it also have 8spd grip shifts that you can also have. If you have the time check out the poker ride and we can rummage the parts crate together afterward. It's funny because I am setting up the Wife's bike with an 8 spd cassette and 7 spd shifts this week.
     
  3. jeffj

    jeffj Bloated Mountain B'hiker

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    Well, I apologize if that was an uncomfortable read.

    For the record, I have tried using 9 speed shifters with an 8 speed cassette on a bike of my daughter's (1996 La Luna hardtail) that originally came with LX 8 speed stuff. When the 8 speed LX stuff broke, I replaced the shifters with newer 9 speed Deore pods.

    I had ran 8 speed XT shifters on my 7 speed GT for 10 years. That works fine. I wrongly assumed that the 9 speed shifters would be fine with 8 speed just like 8 speed had worked with a 7 speed cassette. It shifted like ass.

    I felt the OP was being misled. I would not want to have my wife riding a bike that shifted poorly. I tried to keep emotion out of the post, but I guess it may have come off a bit tense.
     
  4. SAR_boats

    SAR_boats Booze Bikes n Boomsticks

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    That is .6mm per gear. Each time you shift the difference in spacing will multiply. At best, with the derailler lined up in the middle of the cassette, when you shift up to the highest gear or down to the lowest you are looking at .6mm x 4 or x 3 (3-4 gear changes either way) for a difference of 1.8-2.4mm which is enough to get the rear gearing to slip.

    At worst (with the derailler lined up with either the highest or lowest cog) you would have to multiply the .6mm difference x 7 (8 spd casette) or x8 (9spd cassette) for a difference of 4.2-4.8mm which is one whole gear distance.

    On an extremely worn drivetrain there is more side play in the chain and cogs so the difference in spacing doesn't make for as big a problem, but once either one of the cassettes, or the chain is replaced, expect to have misshifting issues.
     
  5. bigpete61

    bigpete61 New Member

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    I have a 9 speed shimano shifter on a 8 speed cassete on my wifes bike and it shifts perfectly. It's all about having the mech skills
     
  6. DirtymikeTDB

    DirtymikeTDB Guest

    After attending Barnetts School of bikes, I still dont have the skill to make a nine speed shifter work on an eight sp cassette..... that is until I stop caring about crappy shifty, along side with ghost shifting.




    Ok so anyone looking to upgrade on a budget, here is what you will need. One rear shifter, one chain, one cassette. Your eight speed derailer will work with the nine sp system, the eight sp chain will not.

    If anyone is owrried about the price, you can always start off with a cheaper cassette, should be able to get a decent cassette for 30-35 dollars. You dont have to have the priceyest shifter either. Save yourself the trouble of trying to mickey mouse something that will shift crappy, and probably skip when you stand up and crank, and just stick with what you have, or do it right.


    Not directed at anyone....its a statement to anyone wanting to swap over from eight to nine.
     
  7. DirtymikeTDB

    DirtymikeTDB Guest

  8. b3rnard

    b3rnard Member

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    Enlighten me, .6 is "constant" spacing between the gears. If your statement says "multiply the .6mm difference" by X then the would 2nd and 3rd gear would be spaced 1.2mm and so on. Yeah that would make horrible shifting.

    Like wise apologies from this side. For the record, not trying to mislead anyone. What's there to gain if I mislead any one?

    Yes, in "theory" it should not work. But I like to think out of the box and tinker with stuff, and see if it works. It my case I got it to work just fine.

    I know we have bike mechanics on board, expert gear heads, etc. who think this set up will no way in hell will work. If it scares you, don't worry about it, it's on my bike and my components. let me worry about it :lol:. Thanks for the input it's been educational.
     
  9. SAR_boats

    SAR_boats Booze Bikes n Boomsticks

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    The 0.6mm is the difference in spacing per gear between an 8sp cassette and a 9sp cassette. (the constants are 5.0mm(8sp) - 4.34mm(9sp) = 0.66 which I conservatively rounded down for machining errors etc. thus 0.6mm difference)

    Since trigger shifters are indexed to move the derailller a set amount when you click them an 8sp trigger shifter is designed to move the derailler 5.0mm per shift so that the jockey wheels line up with the next gear. Similarly a 9sp shifter is designed to move the derailler 4.34mm per shift so that the jockey wheels line up.

    So while every time the gears change they move a constant distance, the difference in distances multiply every time because the overall distance multiplies.

    So in terms of distance (in this example it would be a 9speed shifter and 8-speed cassette):
    gear change.........8sp............9sp...............difference
    ------0---------0.0mm-------0.0mm----------0.0mm
    ------1---------5.0mm------4.34mm---------0.66mm
    ------2---------10.0mm-----8.68mm---------1.32mm
    ------3---------15.0mm-----13.02mm--------1.98mm
    ------4---------20.0mm-----17.36mm--------2.64mm
    ------5---------25.0mm-----21.7mm----------3.3mm
    ------6---------30.0mm-----26.04mm---------3.96mm
    ------7---------35.0mm-----30.38mm---------4.62mm
    ------8----------none-------34.72mm---------5.28mm


    Notice how they start and finish in roughly the same overall distance but there is one more shift in a 9 speed shifter.


    If your setup works I would bet it is because your entire drivetrain if pretty well worn. Considering that an 8-speed chain is wider than a 9 speed chain, a worn 8speed chain will be more tolerant of misaligned jockey wheels than a 9 speed. Also I am guessing that at some piont during your shifting through the cassette you have to double shift to take up the excess difference in distance between gears.

    I cannot believe that it works perfectly. I think by you saying "It works on my rig" you mean "It kinda works but I have to either adjust my barrel adjusters constantly and/or deal with mis-shifts, and/or double shift at least once in the cassette". Or your shifter is non-indexed.

    Consider yourself enlightened.
     
  10. DirtymikeTDB

    DirtymikeTDB Guest



    Absolutly excelent post.
     
  11. yamahabr6

    yamahabr6 New Member

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    very well put


     

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