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Thread: Fork clunk

  1. #1

    Default Fork clunk

    Dudes,

    Long time creeper first time poster. Recently picked up a 99 convertible, have done a few things to it including +4 tubes from TC bros. When first reinstalling I used 10oz of fluid per fork because thatís what tc broís handy little instruction kit said my model needed. Got down the road and there was a pretty mean clunk from the forks, I got back into my manual that said it needed 11.5oz fluid, so I took those devil fork caps back off and put another 2oz in bringing me to ~12oz/fork. It definitely helped but still a little clunky and itís hard to tell when it does it worst. Low speed potholes seem to get it good.
    Other info, yes Iím 100% sure I put everything back together correctly- theyíre showa forks- and Iím using bel ray 15w fluid. I know the standard for these is 5w.
    Should I add more fluid? I should also mention the springs were performing fine before I took them apart and added the tubes. Picture for funzies
    Attached Thumbnails Attached Thumbnails 74917229-A4F9-4322-953B-0DB918E9D09F.jpg  

  2. #2

    Join Date
    Feb 2015
    Posts
    259

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    you sure its coming from the sliders / suspension and not your head bearing being too loose? I had this problem once where my bearing adjuster had loosened off causing the fork neck stem to move up and down slightly until it was tightened back up correctly.

  3. #3

    Default

    I should’ve opened up by saying I had already checked the fork pinch bolts, front motor mounts, tank bolts, handlebars (solid bushings) and the nut on the neck. As I understand from the manual it’s just supposed to be snug? Then that pinch bolt is torqued too.

    Figured someone on here would’ve ran into this problem putting longer tubes on

  4. #4

    Join Date
    Feb 2015
    Posts
    259

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    might be worth jacking the front of the bike off the ground and grabbing the forks and lifting them up and down by hand to make extra sure you dont have any up/down freeplay in the neck.

  5. #5

    Join Date
    Oct 2018
    Posts
    335

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    There's a good chance that the TC Bros/Moto Iron forks are out of spec by a few thou. I had that problem with two sets of Moto Iron fork legs I got and even with brand new seals and bushings their fit within the sliders was too loose and they'd emit a loud 'clunk' when hitting even minor road irregularities or when getting hard on the front brakes. I also had issues with the supposed 'hard chrome' finish on both sets of legs which pitted and wore too easily after just a few thousand miles. What soured my experience with TC Bros even further was that they refused to acknowledge that their overseas supplier may have quality control issues and maybe they should take it upon themselves to do random quality inspections on the products they receive and sell... not indicative of a conscientious retailer.

  6. #6

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    Quote Originally Posted by Skjoll View Post
    There's a good chance that the TC Bros/Moto Iron forks are out of spec by a few thou. I had that problem with two sets of Moto Iron fork legs I got and even with brand new seals and bushings their fit within the sliders was too loose and they'd emit a loud 'clunk' when hitting even minor road irregularities or when getting hard on the front brakes. I also had issues with the supposed 'hard chrome' finish on both sets of legs which pitted and wore too easily after just a few thousand miles. What soured my experience with TC Bros even further was that they refused to acknowledge that their overseas supplier may have quality control issues and maybe they should take it upon themselves to do random quality inspections on the products they receive and sell... not indicative of a conscientious retailer.
    I’m afraid this is most closely related to my problem. I’ve found even with their unopened stuff that they make it pretty difficult to return. But if the tubes were loose in the sliders would it make them leak? Mine are dry. I guess for now I’ll just drain them and replace with a heavier weight and see if that feels any different

  7. #7

    Join Date
    Oct 2018
    Posts
    335

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    Quote Originally Posted by jmcartor View Post
    Iím afraid this is most closely related to my problem. Iíve found even with their unopened stuff that they make it pretty difficult to return...
    I had no problems with them sending me a replacement set of fork tubes, they were good in that respect but they never even bothered verifying that the replacements they sent me were within spec and free of defects because the box still had the unmolested Moto Iron factory tape sealing the box. I initially wanted to be supportive of a couple of brothers wanting to get into the biz of supplying motorcycle parts just like the Malinky brothers of Lowbrow Customs and I was willing to give them the benefit of the doubt despite their apparent inexperience but according to Tyler's Linkedin page he's the 'mechanical engineer' of TC Bros yet he failed to question that their supplier might have had quality control issues even if it was isolated to a single batch/run, something all the mechanical engineers that I know acknowledge as a possibility in the manufacturing process. Also, the replacement set of legs I received had surface pitting straight out of the box.


    Quote Originally Posted by jmcartor View Post
    ... But if the tubes were loose in the sliders would it make them leak?...
    Since we're talking about a few thou clearance it's enough slack to be structurally unsound but new pliable seals have enough flex to deter leakage, but give it time. It took about 2K miles for mine to start leaking which was about a week after installation since I was touring at the time.

    Quote Originally Posted by jmcartor View Post
    ... I guess for now Iíll just drain them and replace with a heavier weight and see if that feels any different...
    The fork oil's purpose is for rebound damping and to act as lubrication at friction points... you could go as far as putting thick grease in the tubes but it won't fix the effects of a sloppy 'metal on metal' fit.
    Last edited by Skjoll; 3 Weeks Ago at 5:39 AM.

  8. #8

    Default

    Thanks for the info man. I’ll call today and get a new set on the way unless you don’t think it’s worth it, not sure if they’d just refund me. Did your new tubes have the same problem?

  9. #9

    Join Date
    Oct 2018
    Posts
    335

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    I'm not sure they'll listen to a complaint where there's no photo evidence of a defect. I had pictures of scratches and pits that developed so they kinda had to listen but I doubt they'd be open to a complaint about a clunking noise and will assume that you're a mechanical idiot as they did with me. I wouldn't be surprised if they give you the same BS line they gave me... "we've sold hundreds of fork tubes and we've never had a complaint about this before, so...".

    The replacement set had the same problems as the first, the sections of the leg where the inner bushings sit were narrower than OEM, the orifice for the damping rod was larger than OEM and the 'hard chrome' wore and ended up scarring far worse in just a few thousand miles than forks I've seen on +40 year old bikes with over a 100K miles on them. After going back to the OEM tubes and being 'clunk-free' I was just fed up with the Cobb boys, ate the $250 and chalked up the experience as a lesson learned and will probably use the fork tubes in a scrap metal kinetic yard sculpture.
    Last edited by Skjoll; 3 Weeks Ago at 3:49 PM.

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