Worn Freewheel - Choose 5 or 6 Speed Replacement?

Eugbug
Eugbug Posts: 13
edited May 2016 in MTB workshop & tech
The freewheel/rear sprocket set on my old bike is worn from not changing the chain soon enough. I replaced the chain but its slipping on the 4th and 5th gear because of the wear. So should I go for a 5 or 6 speed replacement freewheel? As I understand it, 5 speed freewheels are "extinct" but clones are still available on eBay. However 6 speed freewheels seem to be more abundant and cheaper. The existing freewheel is a 14 to 28 tooth Shimano MF Z015. So would there be any issues using a 6 speed replacement? If I don't change the shifter, is it simply a case of just setting the L stop so I don't drop down into the lowest gear? (Lowest gear would then be the 2nd one with 16 teeth)

Comments

  • keef66
    keef66 Posts: 13,123
    According to Sheldon Brown the sprocket thickness and spacing are the same for 5 and 6 speed freewheels, so the 6 speed is wider overall. So you'd be OK as far as the shifter / cable pull, but it may not fit with your axle / dropout spacing. The smallest sprocket could be hitting the dropout / chainstay.
  • Eugbug
    Eugbug Posts: 13
    edited May 2016
    keef66 wrote:
    According to Sheldon Brown the sprocket thickness and spacing are the same for 5 and 6 speed freewheels, so the 6 speed is wider overall. So you'd be OK as far as the shifter / cable pull, but it may not fit with your axle / dropout spacing. The smallest sprocket could be hitting the dropout / chainstay.

    I'll measure to see if that's likely to happen.
    Can I choose whether the largest or smallest sprocket will be unused? I'd like to be able to use the smallest sprocket and forget about the lowest gear, but will the derailleur, when it's in its relaxed state, allow the chain to drop onto the small sprocket?
  • The Rookie
    The Rookie Posts: 27,812
    Yes, you'll be able to choose which gear to not use when you set it up. The dérailleur has stops and you'll have to adjust those for a new freewheel (even if you got another 5), so you just set them to span the gears you want to use.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Eugbug
    Eugbug Posts: 13
    The Rookie wrote:
    Yes, you'll be able to choose which gear to not use when you set it up. The dérailleur has stops and you'll have to adjust those for a new freewheel (even if you got another 5), so you just set them to span the gears you want to use.
    Sprocket spacing seems to be about 6mm / 1/4 inch (is it metric or imperial?) The chain stay/seat stay seem to spread easily enough and I can push a 6.5 mm drill bit in between the outer face of the existing freewheel and inner side of the dropout so that isn't an issue. The chain will head out at at a greater angle from the plane of the bike frame in order to mesh with the 6th gear (is that correct?) so I might have to adjust the front derailleur slightly to avoid the chain rubbing off it?
  • The Rookie
    The Rookie Posts: 27,812
    If you have to bend the frame to get the drill bit in, it will catch with a freewheel filling that gap!

    If that works out OK, then yes you may have to tweak the front mech slightly, but most likely won't.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Eugbug
    Eugbug Posts: 13
    The Rookie wrote:
    If you have to bend the frame to get the drill bit in, it will catch with a freewheel filling that gap!

    If that works out OK, then yes you may have to tweak the front mech slightly, but most likely won't.

    Sorry, I should have said that I can get a drill bit between the inside of the dropout and the outer surface of the cone (rather than the face of the freewheel). I don't have to bend the stays in the sense of permanently deforming them, they return to their original positions when I let go. The cone on this freewheel seems to project a good bit, unlike the one on my other bike which is almost flush or slightly recessed into the freewheel (7 speed). So I reckon there should be enough clearance between the sprocket and dropout (unless 6 speeds are completely different with the cones ending up inside)

    WP_20160510_003.jpg
  • The Rookie
    The Rookie Posts: 27,812
    By Cone I presume you mean the locknut which should be the furthest out part, on most freewheels the cone is a long way further in with a large spacer in there as well.

    Sounds like you'll be fine then.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • Eugbug
    Eugbug Posts: 13
    The Rookie wrote:
    By Cone I presume you mean the locknut which should be the furthest out part, on most freewheels the cone is a long way further in with a large spacer in there as well.

    Sounds like you'll be fine then.

    Sorry, yes I meant the locknut.

    Thanks for the help! Will post a photo if it all works out ok!
  • penguin_of_death
    penguin_of_death Posts: 219
    If you're in the UK walk into Halfords with £15, walk out with 5 speed freewheel
  • Eugbug
    Eugbug Posts: 13
    Penguin of Death wrote:
    If you're in the UK walk into Halfords with £15, walk out with 5 speed freewheel

    Just had a look at that and will keep it in mind.
    Thanks for the suggestion!

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