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Custom Fork Bushes, what to make them from.

Discussion in 'Downhill & Freeride' started by HardtailHack, Nov 6, 2009.

  1. HardtailHack

    HardtailHack used an iron once

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    I have yet another stupid question.

    What materials and coatings do manufacturers use in their fork bushes?

    I am looking at getting a set of custom made bushes for my Kowa 200SI, I can get Teflon coated bushes made through work but was wondering if it's the best coating to use.

    My forks have around 50hrs use total and I have just re-bushed them with a new type of bush but Kowa don't seem to have a QC facility as the bushes installed have a inside dia that is far too big causing stiction and mass amount of movement.

    Should I bother attempting to have bushes made or should I just scrap my 200SIs and my 160SS which has the same problem(and many more)?
     
    #1 -   Nov 6, 2009

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  2. Steve M

    Steve M Turbo Monkey

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    Try to make em for sure - if you've got the capability then why pass it up? I'd be looking at various grades of stainless for starters, should give you decent characteristics. Teflon coating certainly won't hurt, 99% sure that's what most of the major manufacturers use (Avalanche 99% sure, Fox and RS also pretty sure, NFI about Marz or Manitou).
     
    #2 -   Nov 6, 2009
  3. Polandspring88

    Polandspring88 Superman

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    How tight is the fit? Any chance you could hone the bushings?
     
    #3 -   Nov 6, 2009
  4. essenmeinstuff

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    Pretty sure if you read his post again, the fit is not tight, but too loose :)
     
    #4 -   Nov 6, 2009
  5. Polandspring88

    Polandspring88 Superman

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    Oops! Reading comprehension is over-rated anyway...:rant:
     
    #5 -   Nov 6, 2009
  6. Huck Banzai

    Huck Banzai Turbo Monkey

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    Hot Diggity!
     
    #6 -   Nov 6, 2009
  7. Sonic Reducer

    Sonic Reducer Monkey

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    bronze? definitely do a material that is softer than the stanchions.
     
    #7 -   Nov 6, 2009
  8. w00dy

    w00dy In heaven there is no beer

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    To my knowledge most forks use a bronze-backed teflon bushing. You want the bushing to be a much softer slick material, no metal on metal. Measure your stantion tubes with a micrometer. You want to ream the bushings to be about .001" larger than that. (after you press them into your fork of course, they will shrink when you install them) A couple extra thousandths will create rattle, but not stiction. Go for a 1:1 fit of you don't mind some break-in time.
     
    #8 -   Nov 7, 2009
  9. HardtailHack

    HardtailHack used an iron once

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    Thanks w00dy I was wondering if I should ream them after installation, the new bushes I got are both very loose on the stanchions. If you slide one bush on there is lots of movement however if you slide both bushes on(with tube assy) on they become tight which means they are crooked from the factory, Go Kowa!!!

    After installing them they felt OK for one run and then they started feeling like an XC fork with a lockout.

    So Teflon faced bushes with with .001" clearance is the go. My only question is can you ream a Teflon coated bush?
     
    #9 -   Nov 7, 2009
  10. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    You can, obviously only down to a point where there is still teflon left. TFTuned do this to stock forks that have excessively tight bushings.

    Don't mean to be the spanner in the works, but IMO fork bushings are a very finicky job best left to the manufacturer (or in this case, a manufacturer that knows what they are doing). I have seen few good results with bushing replacements even in capable hands, and personally would prefer to grab new lowers than bother trying to do a bushing swap that wasn't a miserable failure.

    If it's costing you nothing and you don't really care about the fork, then definitely give it a shot and see how it goes, hopefully it works out. But if it fails, I'd take your second option and grab a different brand of fork without known bushing problems.
     
  11. Lelandjt

    Lelandjt Turbo Monkey

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    Sorry to hear this. I was hopeful about the Kowa forks: infinite travel adjust, weight, cost...
     
  12. HardtailHack

    HardtailHack used an iron once

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    Sorry, I've been nice up until now about my Kowa forks- My 160SS has had three steerers spin in the crown, also has scores on the air spring from stupid amounts of bushing play causing the air spring to hit the inside of the stanchion. The lowers are painted without masking the sealing area meaning bushes are pressed in through paint which causes paint to flake and end up in your oil. Another problem is that any oil that is fed through the damper is shot straight to the top of the forks meaning you have to run very high oil levels to keep some damping through sucessive hits.
    These forks were so sticky I could put my 100kg of fatness on the bars and the forks stayed at full travel.

    My 200si also has scoring on the air spring however it is much worse than on the 160SS, I'll grab some pics soon.

    Why Avalance would even make a damper for this fork I'll never know.
    Kowa-FTB(For The Bin).

    I will try and rebush them as I think it will be impossible to do a worse job than those at Kowa have already done. One good thing about the new bushes is they come in a sleeve that is pressed into the lower leg. This should mean I can ream them very slightly oversize and then insert them into the lowers and have a good fit.

    Ahhh, the joys of being different.
     
  13. MrPlow

    MrPlow Monkey

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    Bloody hell S you sure about your Stainless reccomendation?? I would say alloy. And if you wanted to get really flash get them teflon coated. OR Get some oil impregnated nylon and machine it, might be too thin though (the finished bushing I mean)
     
  14. TomBo

    TomBo Monkey

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    Myself being an 4th year apprentice machinist. I replaced a set of bushigns in my 3 year old Fox 40. Once I removed the old bushings, I checked the size and roundness of the lowwers. I couldn't believe the amount of slop, there was about .008" out of roundness / one side to the other. If I recall correctly. No this may not have a huge impact on the bushings once installed. But it sure as heck can't help. The reamer ( I'd guess ) they used on the castings, must bounce around like crazy and or be rather dull. The walls were scored quite bad IMO. The replacement and original bushings were both split (the split was about 1/16" once installed) ring and aluminum backed. Having some kinda nylon or teflon type coating. That fork never felt great, sicky, blah. I was the original owner. After replacing the bushings and riding for about 5 hours. Things hadn't gotten better. Now someone else is dealing with it, but for only a 1/8th of the cost I payed. I wish I'd moved on along time ago!

    Good luck with your fork.
     
  15. DirtyMike

    DirtyMike Turbo Fluffer

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    Get in touch with Drake Thomas, he owns Isotuned suspension down in San Diego. He has ev erything needed for custom bushings, does excellent work as well. HIs Handle is Drakethomas over on Socaltrailriders
     
  16. HardtailHack

    HardtailHack used an iron once

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    Sorry guys I am yet to get photos of the scored air spring, I was told I couldn't get bushes made for my forks as the manufacture needed an exta 1mm OD to machine them up.
    So I ordered a set of 2010 Totem DH coils, the importer said there wasn't much difference between 2009-2010 forks, ordered 2010 got 2009, they got sent back. The day after I ordered the Totems I was told by a supplier he had bushes off the shelf, turns out they are the same brand as the ones Kowa use. I grabbed two bushes to test with which were strangly the same Dia inside and out as the Kowa bushes but longer overall.
    I pressed the original Kowa bushes out of the retainer sleeve and checked the fit of the new ones, very tight. I ended up spreading the bush slightly and filing the join down so the bush had a smaller ID when fitted into the sleeve. I checked fit in both the sleeve and around the stanchion many times and believe I now have a fit that is many times better than factory.

    I know this all sounds very crude but when you realise how poorly Kowa forks are assembled it makes my work look very tidy indeed. After five hours of riding on the genuine Kowa bushes the forks wouldn't compress with my 230lb directly on the bars and there was about 1/4" movement fore/aft at the axle.

    Never have I been so dissatisfied with any product I have ever bought, biking or otherwise, why I bought 2 Kowa forks I will never know.
     
  17. w00dy

    w00dy In heaven there is no beer

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