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Front wheel offset with dual disc

Discussion in 'The Garage' started by WideAWAKE, Apr 6, 2021.

  1. WideAWAKE

    WideAWAKE Single Fins and Twin Cylinders

    I proposed this question in my build thread but got crickets, thought maybe a specific general thread may bring about an answer.

    Ok so I’ve run into a little bit of a snag when mounting up my dual discs.

    It seem the front wheel sits about .050 further to 1 side than the other.

    Now that doesn’t seem to be any real concern to me BUT it does mean that one disc sits to the inside of the caliper and has a slight rub and the other sits to the outside and has a slight rub.

    this can be easily solved if I run a little thicker shims on one side and a little thinner ones on the other (currently they both have shims that measure .245)

    the forms are an 81 and the wheels are in pretty sure 74.

    I’ve ran both the axle and speedo gear from the 74 and the ones off the 81 and it seems to make no difference where things line up (although the speedo gears do measure .100 different on their retaining sections where they contact the fork stop but bodies measure the same distance and that’s what seemsimportant)

    the axles themselves seem to be slightly different too but they both seem to end up in the same place when it’s all said and done.

    is there something glaring obvious that I’m missing here or is it just a simple fix of adding .050 to one side and taking it away from the others?

    first photo is the right side (when sitting on the bike) second photo is the left.

    Any words of wisdom would be greatly appreciated.

    C7469EBD-C09F-4670-9BAA-3037AD28AF23.jpeg E5846EAE-EBA9-425B-80E0-67BA963DFABD.jpeg 912F55CC-5280-4EFE-A802-4D1D8341FA20.jpeg 126A2DB6-94CC-4841-89CF-FE450BAD427E.jpeg FB85557F-E72D-4C39-AB7D-AF3E4B8CFB9C.jpeg 9626F8F8-6AED-44AB-8AFA-DD28AEA9EC63.jpeg
     
  2. RustiePyles

    RustiePyles Semper Fortis XS650.com Supporter Top Contributor

    I don't think you have an offset issue, I think you need to clearance your caliper bracket. The Stock XS Caliper bracket was not meant to work with floating rotors.
     
    Team Junk likes this.
  3. Machine

    Machine Race the wind Top Contributor

    "Crickets" but seen. I agree that the floating rotor disc hardware there may require a wider channel in the caliper hanger bracket.
    It does look to me like you could loosen the left axle pinch bolts and pull that left fork leg "out" a few more thousandths, like .020 more would even help center the caliper.
    XS caliper hangers I've mounted were correct in position with no shimming.
    -R
     

    Attached Files:

  4. WideAWAKE

    WideAWAKE Single Fins and Twin Cylinders

    I appreciate the replies.

    I don’t think I have a problem either, beyond adjusting the shims but the fact it’s pretty much all my stopping power and well life quite possibly depends on it, I just wanted to make sure I wasn’t clearly missing something that was blatantly obvious.

    And the more I think about it, I think only one is off.

    the disc should slightly touch/skim the inside pad correct?? Since it doesn’t have movement? Only the piston side moves.
     
  5. WideAWAKE

    WideAWAKE Single Fins and Twin Cylinders

    and yes I did that but didn’t like the idea of alignment by “force” because if for some reason it walked back the disc would clip the caliper and lock up.

    wouldn’t be a problem on a stock disc though.
     
  6. RustiePyles

    RustiePyles Semper Fortis XS650.com Supporter Top Contributor

    Your going to need to cut a radiused clearance channel in your caliper bracket here to allow the rotor spools to pass through.
    E5846EAE-EBA9-425B-80E0-67BA963DFABD.jpeg
     
    Team Junk and Machine like this.
  7. WideAWAKE

    WideAWAKE Single Fins and Twin Cylinders


    That is the disc with the offset in the wrong direction (using the shims provided with the calipers)

    if I take .030 - .050 off the caliper spacers it will provide good clearance and have it just skimming the inside brake pad. Which was my initial thought and solution.

    I got 74 rims and hubs in an 82 fork and I know it should be a straight swap but just needed to make sure I wasn’t missing something.

    I will reduce the shims on the caliper and I should be good to go.

    thanks for the help!
     
    Team Junk and RustiePyles like this.
  8. 5twins

    5twins XS650 Guru Top Contributor

    20,889
    13,600
    813
    It appears the whole wheel needs to be shifted to the right a little bit. I think the simplest solution would be to acquire another right side axle spacer and shorten it by a MM or 2.
     
    arcticXS likes this.
  9. Team Junk

    Team Junk XS650 Guru XS650.com Supporter Top Contributor

    Those do look awfully close. Anything that could stop the front wheel from turning going down the road would have me worried. Even with the proper spacing on the caliper that seems really close to a potential bad day.
     
    RustiePyles likes this.
  10. Machine

    Machine Race the wind Top Contributor

    SR500 rotors are 5mm thick, darn near as light and just bolt on very easily. And the spacing is correct.
    20201206_180650.jpg
    Just sayin, again..
     
    arcticXS and Team Junk like this.
  11. gggGary

    gggGary When a whole one is just too much. XS650.com Supporter Top Contributor

    I'd start here;
    not crickets but birds chirping. :rolleyes:

    been running this for years, first with a mag and drilled stock rotors
    madness front wheel mag org rotors.jpg
    then with FJ rotors on a spoke hub. I custom made the rotor spacers to set the offset.
    madness front.jpg

    No matter how tempting don't try to "spread" the tubes apart with the axle/clamps it'll create horrible stiction in the sliders.
     
    Last edited: Apr 6, 2021
    Team Junk, arcticXS and Jim like this.
  12. Jim

    Jim Beyond the edge is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    thumbsup.gif
     
    arcticXS and gggGary like this.
  13. WideAWAKE

    WideAWAKE Single Fins and Twin Cylinders

    thank you all for helping me better think through the situation

    I’ve pulled it all apart and found some discrepancies between my two calipers.

    I will post more on that when I get a second later tonight.

    in the meantime...

    Can anyone confirm this dust cover measurement?



    B4D3FE1A-A25C-4525-953E-C07F020285AA.jpeg
     
    gggGary likes this.
  14. arcticXS

    arcticXS XS650 Guru Top Contributor

    That is pretty much bang on 20 mm. When measuring parts on a japanese bikes, using metric measurements makes a lot more sense. Things like fasteners, bearings, axles, spacers, pistons, and so on, are mostly in whole millimeters. Pistons being the exception, as next oversize generally is 0.25 mm up.
     
    RustiePyles, Jim and gggGary like this.
  15. gggGary

    gggGary When a whole one is just too much. XS650.com Supporter Top Contributor

  16. WideAWAKE

    WideAWAKE Single Fins and Twin Cylinders

    Ok...

    so after measuring every dimension I could find to measure here is what I’m lookin at.

    the distance from the caliper mounts on the fork tube to the hub are about 4mm off set. They do measure the same thickness though.

    Everything on the hub itself measures correctly and looks lined up correctly when bolted together.

    the gap between the insides of the fork lowers at the axle through measures just under 150mm which makes sense as to why we have a little gap between the speedo gear and the fork when the dust cover + hub + speedo drive is 148.

    AAB2B0C6-1E4C-4C68-992B-F6C563E34B8D.jpeg

    D52941FC-3398-4ACD-9A32-A81C96C797EC.jpeg

    CAF3170A-8C85-4C9F-85EA-EA87AF81BCDF.jpeg


    5mm is pretty much the distance between having my rotor touch and having it sit at a nice clearance where it should.

    so with the off set mounts, this leaves 1 mm to go.

    when I took a look at my calipers - it turns out they are different and actually measure just about 1mm different. The thicker one being the left side which means it’s pushed an additional 1mm closed to the rotor.

    733F6609-C239-4E60-AE8A-BEC32469421D.jpeg

    AB717019-4A3B-4861-8858-CBB529896EAC.jpeg

    C737BA7E-61F3-4776-B852-A9AD4EC87E62.jpeg

    I know my forks are straight so my initial thought is to just slim down my shims and call it a day.

    Am I missing something??? The more brains the better.
     
    Machine likes this.
  17. Machine

    Machine Race the wind Top Contributor

    Just a mention. Measuring to the spoke head per side can be a "reference" but what really needs to be measured is the distance to the brake disc mount surface. That is the machined feature which controls the discs positions side to side.
     
    WideAWAKE likes this.
  18. 5twins

    5twins XS650 Guru Top Contributor

    20,889
    13,600
    813
    Wouldn't you need to slim down the shims on the left but increase the width of the ones on the right? That's why I suggested shortening the 20mm axle spacer a little. Instead of having to modify 4 shims, you'd just have to re-work one spacer. That would shift the whole wheel to the right a little bit and center both discs for you.
     
    WideAWAKE likes this.
  19. WideAWAKE

    WideAWAKE Single Fins and Twin Cylinders


    Yes, I did that, but for the purpose of visuals so people could see what I was talking about and the ease of capturing a photo with one hand and clearly showing a measurement...

    the actual measurements I got were from the inside of the mount tab on the fork to the mount face on the hub.
     
    Machine likes this.
  20. WideAWAKE

    WideAWAKE Single Fins and Twin Cylinders


    The disk on the right side(sitting on the bike, the stock placement) sits in the rotor with the max amount of clearance between the rotor and the caliper which is good.

    it’s the other one that sits too close and yes, your suggestion would work but it would also push the other rotor closer to the caliper which would leave me adjusting the shims on that side after.

    Reducing the shims on the left caliper by 5mm would leave me with both rotors at max clearance in relation to the calipers.
     
    gggGary likes this.

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