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Lowering forks

Discussion in 'The Garage' started by rmal, Dec 13, 2010.

  1. rmal

    rmal XS400 Member

    Hey Hardtailed - I cut the front springs of my '78 xs400 about 2 1/2" to lower the front end. I read your comment here about adding spacers. I didn't add spacers - should I? I haven't ridden the bike yet. What should I make the spacers out of? thanks... rmal
     
  2. rmal

    rmal XS400 Member

    here's the bike...
     

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  3. Spacers are needed to make up the cut-off length of your springs. I can't remember how much I cut off. I actually had to cut mine twice to get exactly what I wanted. My spacers are made of simple PVC pipe. I have put around 1500 miles since doing the forks, and have had no problems. I would buy a few feet of PVC and cut a few different lengths. Try one, and see how your fork compression looks.
     
  4. rmal

    rmal XS400 Member

    On those front spring spacers - stupid question - but are they meant to take up the space between the cut-down spring and the retainer at the top of the fork?

    Should the spacer be long enough to compress the spring a little, or just to be touching the uncompressed spring. I'll try the pvc route like you suggest.

    Here's a paint scheme I'm playing with. I shot the bike with gloss rustoleum using a compressor and a $30 Lowes gun. Did it outside on a sunny calm day and it came out pretty good - I'll buff it a bit in spring. I read some things about rustoleum not being resistant to gas, but I painted a small piece of metal and have spilled gas on it a lot to see if it softens - and it doesn't. The black tape is giving me a sense of some stripes I'm considering.

    The rear fender is the stock one, rotated up into the frame and the holes filled with epoxy and bolted to some fabricated mounts. I'm too cheap to buy a new fender.
     

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  5. Travis

    Travis Staff Member Staff Member

    rmal,

    on most bikes, you want a little bit of preload on the fork springs so you can get the proper sag. That means the spacer (if you need one) and fork cap on the top of the spring should compress the spring a little like you said in the post above. If you shortened your forks by cutting the spring, you’ll need to add a spacer to the damper rod to limit the travel by the amount you intended to shorten the forks. Don’t worry about the spacer on the top of the spring until you’ve done this. After you add the spacer to the damper rod, you can then check to see if you need to add a spacer or lengthen the spacer on the top of the spring to get the preload you want. If you just add a spacer to the top of the spring and not to the damper rod, you won't lower them at all, you will have just increased the spring rates for a stiffer suspension.

    Also, when you shorten the forks by limiting travel, you want to increase the spring rate so you don’t bottom out. Luckily, cutting the springs does just that. You can increase the spring rates even more by cutting more off the springs and making the top spacers longer (or adding them if you don’t have any), all while keeping in mind the pre-load you are shooting for. I hope that helps! :bike:
     
  6. rmal

    rmal XS400 Member

    Great advise, Travis - really appreciated. I understand that I will pre-load the spring a bit with (if needed) a spacer between the fork cap and the top of the spring AFTER a spacer is added to the damper rod to limit the travel by the amount I want to lower the suspension. The spring-to-fork cap spacer I can envision. I'm having some trouble imagining the damper rod spacer.

    I didn't remove the damper rod when I cut the springs (by 2" BTW) so I can't envision the configuration of the damper rod spacer. Is it a tube that slips over the rod somehow? If so, and assuming I'd like 2" of lowering which was the amount I cut from the springs, would I make a 2" spacer tube? Should the material be a steel tube or PVC?

    My (bad) intuition tells me I should be reducing the damper rod by the same 2" that I cut the spring? I'm sure that's not correct.

    sorry for all the questions and really, thanks, for the info.
     
  7. rmal

    rmal XS400 Member

    After digging around I found a few pic's of damper rods. It looks like I have to remove the rods and make a PVC (schedule 80) spacer. I assume the spacer goes under the damper spring (if there is a spring in mine). Is this correct?

    I photoshop-ed (poorly) a spacer onto the damper pics I found.

    Maybe I'm off base here, but just trying to get a visual of what I need to do.

    Again - Thanks for the advise!
     

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  8. Travis

    Travis Staff Member Staff Member

    I would think that PVC would be fine. The spacers could go under or over the springs on the damper rods. You might want to drill a couple holes in your spacers if there is any chance it will cover any of the holes in the damper rod. That will allow fluid to pass though the holes as it should. To start, I would make those spacers the same length as the amount you cut off the spring. Instead of using a spacer on the damper rod, I've read about people using the chunk of spring they cut off.
     
    Excitebike82 likes this.
  9. gentlemanjim

    gentlemanjim More Wrenchin than Ridin

    To lower the front suspension the spacers go under the damper rod springs which allows the fork tube to sit lower in the fork leg. I've done this twice and it works great. If your spacer is 1" I would cut about 1/2" from the springs (or roughly 1/2 the amount of the spacer) to provide additonal preload as Travis suggested.
     
  10. rmal

    rmal XS400 Member

    Thanks. I should have done more checking before I cut the springs. I have already cut the springs 2" (also lowered the rear 2") and the clearance and the travel all seem ok. I'm fender-less. Maybe I'll space the damper rods 2" and pre-load the spring with another spacer at the top between the spring and the fork-cap.

    What have you used for damper rod spacer material - PVC? I don't have the cut-off's from the spring cuts or I'd use them as Travis suggested.
     
  11. gentlemanjim

    gentlemanjim More Wrenchin than Ridin

    That should work fine. I've used copper pipe and PVC pipe, what ever fits over the damper rod.
     
  12. robbie c

    robbie c XS400 Member

    Hey guys i just got my first bike an 81 and am interested lowering the rear end .. any tips ?

    Im pretty new to this so any help at all would be great thanks.
     
  13. captinamazin

    captinamazin XS400 New Member

    This is a really great thread!

    I've been wanting to lower my forks for a while. For the time being I've just dropped my forks in the triple clamps and experimented with different heights. Now that I'm comfortable with the height/clearance/look, it occurred to me that when cutting the spring will impact the spring rate.

    Each wind of the spring coil will be required to defect a greater amount to give the same overall deflection.

    So, what is an appropriate change in dampening to compensate? The stock forks are pretty flimsy as it is (by modern standards).

    Has anyone found what heavier weight oil works?

    I dont have the adjustable forks, but is there a way to change damper rod springs from a bigger bike? or maybe a way to swap in/tighten down the washer stack?
     
  14. Pawl

    Pawl Arctic chop & bob

    Years ago on my RD400 that had sagged out springs (too many wheelies) I used a couple of 1/2" drive sockets of the same diameter as the springs for preload spacers, they are sturdy enough, and sure as shit, they brought the rebound back to life.
     
    Last edited: Aug 25, 2011
  15. Pawl

    Pawl Arctic chop & bob

    Can you weld, or know someone who can?, see the attached pics of what I did to mine. The second and third pictures show the new shock location on the bolt with the nut on it, and the old location has no nut on it. The before/after pics are both taken after I did a similar treatment to the front end to lower it. . but that is another story. I think I even scanned the plates (with a small ruler beside them) into the computer so that if I wanted to do it again I would spend less time grinding, If you go this route let me know, and I'll dig around for the scan. This bike is now my daily driver, and I love it, you can really lay it over in the corners at speed.
     

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    Last edited: Aug 24, 2011
  16. frwinks

    frwinks XS400 Addict

    those look great Pawl. If you don't mind posting the plate dims, I'm sure a few of us could use the "shortcut" and save a few mm of the grinding wheel:laugh:
    I'm planning to extend the swinger by about 3-4" this winter. By looking at things, even after the extension, I still might need more lean on the shocks and those plates might be the ticket:thumbsup:
     
  17. Pawl

    Pawl Arctic chop & bob

    Found It ! . . . Here is the scan of 1 plate just before I bevelled and welded it on. The scan is the original size I scanned it at (I reduced the file size to 30% using Photoshop save for web feature). The ruler should help when printing out, as it was next to the plate when I scanned it. I'd recommend printing it out on an 8.5"x11" label, cut it out and stick it on to cardboard, (a beer box should work) then cut that out, and see how it fits. Travis . . . Do you think I should upload this to the Tech section If so, do I write an article to go with it, or just post the pic?
     

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    Last edited: Aug 29, 2011
  18. frwinks

    frwinks XS400 Addict

    good stuff Pawl..thanks:cheers:
     
  19. Looks great, Pawl! I bet you've seen a significant difference in the way they behave. I have been thinking of putting softer shocks on my rear to make up for the lousy condition of Interstate 94, but now I will probably just steal this idea :D (I just need to get better at welding first!)
     
  20. Travis

    Travis Staff Member Staff Member

    Pawl, this whole thread is already in the tech section. You could create a new thread just for the plate or leave it here.
     

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