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Rim Sprocket Wear - How Much Is Too Much?

Discussion in 'Chainsaw' started by SteveSr, Sep 12, 2019.

  1. SteveSr

    SteveSr Addicted to ArboristSite

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    I'll let the photos speak for themselves. How does one know when a rim sprocket is done and should be replaced?
     

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  2. cus_deluxe

    cus_deluxe Thats what she said.

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    are those all pics of same sprocket? some ive seen have an wear indicator, a little slot that cut in where the chain rides. when that slot disappears its time for a new sprocket. id say theres more life in that one still
     
  3. buzz sawyer

    buzz sawyer Addicted to ArboristSite

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    Maybe a little life left. If you use it a lot and you're putting on a new chain, I'd replace it.
     
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  4. SteveSr

    SteveSr Addicted to ArboristSite

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    Yes, OEM Stihl .325/7. Saw is MS260.

    That's what I thought until I installed a brand new Oregon 22BPX chain. This particular combo of sprocket and chain causes VERY significant chain tensioning issues. Chain is tight some times and loose other times as the sprocket rotates. Drum and bearing are new OEM. A new sprocket fixed the issue. Only thing I can figure is that the tie strap width is different between the Oregon and what was previously run (unknown) and sometimes the new tie straps are falling into the grooves on the worn sprocket (loose) and sometimes not (tight).
     
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  5. pioneerguy600

    pioneerguy600 Lost in Space Staff Member

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    Sometimes those indents are hammered in deeper on one side of the rim than the other, seems the hardening of the metal may be uneven. See it more often on AM ones but even the OEM Stihl ones are showing signs of this lately. Will also add that there was a bad run of Chinese rims that were actually bored off center and was causing a big problem properly tensioning the chains, just added this for future references, not likely the problem with the OP`s rim as its an OEM Stihl in the pic.
     
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  6. ray benson

    ray benson Tree Freak

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  7. SteveSr

    SteveSr Addicted to ArboristSite

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    I looked at the referenced Oregon manual and it mentioned 1/64" = .0156 which is what Ray quoted.

    At first I though that the tie straps might be a different width between Stihl and Oregon but Stihl is only about .004" wider than the new Oregon. The real difference is that the bottom of the Stihl tie straps is flat whereas the Oregon is indented (concave).
     
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  8. Huskybill

    Huskybill Addicted to ArboristSite

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    To me replacing rims depends on how much life is left in the chain. I don’t like to put a new rim on an old worn chain. I usually service both at the same time.
     
  9. ray benson

    ray benson Tree Freak

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    The worn chain fit nicely in the worn rim sprocket. The new chain did not fit the rim so nicely
     
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  10. ChoppyChoppy

    ChoppyChoppy Addicted to ArboristSite

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    I ususally run them till the drivers are getting close to hitting the clutch splines.
     
  11. Huskybill

    Huskybill Addicted to ArboristSite

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    A new rim is cheap a new rim and drum assembly isn’t.
     
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  12. Huskybill

    Huskybill Addicted to ArboristSite

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    That’s why I change the rim and chain at the same time. Any added friction with the used chain and new rim were defeating the gain of running a rim.
     
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  13. Mad Professor

    Mad Professor Addicted to ArboristSite

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    Another option is to have a new set of chains that get rotated with the same new sprocket. They all wear in together.

    I keep my beat rims/chains for cutting up dirty stumps/roots and such. One or two last sharpenings then they get scrapped. These go on with the worn out bars.
     
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  14. Wood Doctor

    Wood Doctor Edwin

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    I'll never forget the Stihl 460 that came into my shop three years ago. The rim sprocket was chopped in half by the chain's drive links. Not only that, the operator kept tightening the chain even more. That cut the spline almost in half and the needle bearing was shot as well. He said, "I had to get the job done, and I guess I pushed it a little too hard. I stopped when the smoke got too thick to see what I was cutting. Things seemed rather hot."
    :eek:
     
  15. Mad Professor

    Mad Professor Addicted to ArboristSite

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    Crank was O.K.?
     
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  16. SteveH

    SteveH ArboristSite Guru

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    Trying to recall, seems I bought some from Bailey's a few yr. back to have on hand. $4 each? If so, and if any doubt just replace. Might have been on sale, don't know, but not much $$.
     
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  17. Wood Doctor

    Wood Doctor Edwin

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    Just barely. That was next on the agenda as the chain continued to grind away. I explained that to him.

    Frankly, I had never seen as much damage as he caused on on the clutch side. He just kept tightening and tightening the chain loop, not realizing what was going on. The saw was trying to talk to him, but he never listened.
     
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  18. ChoppyChoppy

    ChoppyChoppy Addicted to ArboristSite

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    ~$5 for the rim, $25-30 for a drum, so not the end of the world

    The drums need to be replaced after a while as well. They get thin and crack or even break.

    I had one on a Stihl 460 come apart. No idea where the big chuck missing went, but it was working just fine with about 3/4 of the drum left.
    I only noticed it when I pulled it out to grease the bearing.
     
  19. catbuster

    catbuster Catskinner. And buster.

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    That sprocket has plenty of life left in it. I don’t run mine to failure, but I run them well past that point. Your wear markers are still there. When the sprocket starts to wear the drive teeth on the chain it’s time to replace it for sure. I usually carry an extra in the truck box with the clutch bearing, parts for the clutch and so forth. On wildland duty I carry it on my line gear, but I don’t imagine you’ll be doing that.

    As to the story told above, a lot of people bought the MS460 because they thought they needed one or were upsold, and then abused the **** out of them. I don’t know why, but during their time they may have been one of Stihl’s most abused saws. Maybe it’s because the 441 didn’t sell well or people wanted the step up from the 440, or they were upsold from a 390. I’m really not sure. I’m just not surprised about the story.
     
  20. grizz55chev

    grizz55chev Tree Freak

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    When in doubt, change it out. Takes 5 min and leaves no question.
     

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