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  1. #1
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    Default 39mm fork tubes - interchangable?

    Just getting some new fork tubes, and the 39mm +6" ones I want are sold out from vtwin, so I was wondering if anyone knows how much the tubes differ from year to year, and if you can use pretty much any tube with any lower? mine are from a '92, and I see some from '98+ that are available... I know mine have some removable collar on the bottom, and the newer ones do not, and are filled in here. So will newer style tubes work with the lowers?

    Thanks!!

    Attached Thumbnails Attached Thumbnails forktube.jpg  
    Last edited by mikewerx; 03-07-2016 at 6:43 PM.

  2. #2

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    i always understood 88 to 99 are all the same. then i ordered some 3" over aftermarket 88 to 99 tubes.everything was hunky dory except the aluminum cups at the very bottom would not enter the tubes like they did on the old stock tubes.this would be a problem at full compression.

    went and showed my indy that i ordered the tubes from.he was kinda dumfounded then he called his used parts guy and told him to bring up any used cups he had.

    he showed up with a greasy ziplok bag of cups. ho! 3 diff sizes! picked out 2 new used ones that fit and down the road i went.

    i am not familair with the tube on the right without bushing. to new for me.id be surprised if it would work with the lowers from one that had the bushed tubes.

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    Well, after testing, I can't fit the later tubes down the lowers, jams up at the top. Damnit! Now I need to find extended tubes for a '92, or start all over and find a later 39mm fork set. Ugh..

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    First, any 39mm tubes will work for any year. The year groups that are quoted are due to the length of the tubes themselves. For example, 88-99 "stock" length is 24.25", where as 2000 up they are 25" "stock" (most models). This is the ONLY reason fork tubes are quoted by year application, simply to base a length off of "stock". A fork tube yanked off a 2015 Sportster will accept all the internals and fit right into a set of 1988 lowers and vice versa. A set of +6" fork tubes for an 80's/90's application will be 30.25". A set of +6" fork tubes for a 2015 application will be 31". There is no other difference in the tubes. There are other differences in lowers themselves for different year groups (axle sizes, etc) and slight differences in the damper assemblies but again, the tubes are functionally the same.

    Next, I have no idea why CCI and some others now sell those aftermarket fork tubes like that which do not have the collar bushing. I just checked a 2010-14 service manual I have and even those clearly show the tube having the collar bushing such as your old tube. I've never actually seen those other ones in person but have seen photos in the print/online catalogs of CCI, JP, etc.



    All that said, are you saying it is getting hung up on that section where the bushing should be? What does it measure with a caliper? What does the old one measure on the bushing when squeezed tightly?
    Last edited by boomboomthump; 03-11-2016 at 10:56 AM.

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    Quote Originally Posted by boomboomthump View Post
    First, any 39mm tubes will work for any year.
    All that said, are you saying it is getting hung up on that section where the bushing should be? What does it measure with a caliper? What does the old one measure on the bushing when squeezed tightly?
    Boom - thanks for the reply. Sometimes I put trust instead of checking myself. The guy I bought the new 39mm tubes from on here, actually shipped me 41mm tubes, so OF COURSE they won't fit! UGH>>>

    So you're saying I should be safe to buy whatever year, and they will work, as long as they are 39mm tubes? Thanks!!

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