Fixed front calipers

Discussion in 'Hacks' started by transalpian, Mar 20, 2012.

  1. transalpian

    transalpian Over, Across, and Through

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    Greetings all! My hack rig has regained the status of "moving under its own power"!!!!!

    All in all, I'm pleased. But with all things, not yet "done". Here is an old picture. (Progress has been made since then)

    [​IMG]

    As you can see, she has leading link forks with fixed calipers. Other than coverting to floating calipers, what can I do to minimize rise under braking? More front shock spring preload? Less? Other options?

    Thanks in advance!
    #1
  2. Bobmws

    Bobmws Curmudgeon At Large

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    I'm curious as to why you consider the rise to be an issue? My old Earles fork BMW braked that way, didn't seem to upset anything. Is it something you just have to get used to? I would think keeping the chair level and reducing front dive would make handling under braking more stable.
    #2
  3. claude

    claude Sidecar Jockey

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    Floating calipers will make a difference. The rise, in simple terms, is actually a battle taking place between braking and suspension action. It will limit traction a lot in most cases under braking and is not nearly as desirable as otherwise.
    #3
  4. BeeMaa

    BeeMaa Hack Pilot

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    OK Claude, I'm a bit lost.
    If I'm understanding correctly, the floating calipers can limit traction under braking.
    Wait that doesn't make sense to me either.
    Do you mean the combination of the LL front end AND the floating calipers could be a bad combo?
    Help me understand please.
    And thank you in advance.
    #4
  5. outfit

    outfit Been here awhile

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    Look's to me as though those caliper's are floating.
    My eye's are getting a bit advanced though.

    Best way to minimize lift when braking is to place caliper above swingarm. Sort of like below.

    [​IMG]
    #5
  6. transalpian

    transalpian Over, Across, and Through

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    This

    and this

    I guess I understand the advantages of floating and with unlimited funds for this project would have incorporated them into the front end. However, I don't and didn't.

    If I had to do it again, I probably would go a different route (i.e. buy a completed HPS rig :D:D:D). I've learned a lot though, and she is a good ride now.

    Probably something I'll just need to get used to on this rig, I guess.
    #6
  7. transalpian

    transalpian Over, Across, and Through

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    Not really. When the brakes are applied, the torque generated is transferred into the horizontal element of the leading links. Since I'm talking about braking going forward, the torque is counter-clockwise (looking from the left side, like your picture). This CCW torque has to go somewhere so it is "converted" into a force couple, one "up" force behind the axle, a matching (but opposite direction) "down" force in front of the axle. These are the forces that cause the shocks to compress and the front of the bike to rise under braking.

    With a floating caliper:

    [​IMG]

    The torque (and resultant forces) are transferred into the vertical element of the leading links. Sure, this force is trying to bend the vertical element, but its not likely going to bend, and there is no "up" force to compress the shocks and lift the bike.

    Having the caliper above or below the axle has other benefits, but the torques and forces don't know (or care) where the calipers are. the magic is the ability for the caliper mounts to rotate (float) around the axle and the strut that connects the floating caliper to the vertical leading link element.

    The mounting approach you posted is sort of a hybrid. It looks like the caliper can float on the axle, but the connecting strut goes to a bit on the horizontal element. It probably has "some" lift, but I'd guess WAY less than my system.

    All being said, a floating caliper has a more complex mounting system than I have. And I'm not that talented of a fabricator (yet). I'm also cheap.
    #7
  8. claude

    claude Sidecar Jockey

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    I was trying to say just the opposite of that. Floating calipers ARE best!!
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  9. outfit

    outfit Been here awhile

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    With a floating caliper:

    [​IMG]

    I am highly sceptical of this brake set-up as the torque arm is fixed to the down fork. Which I would think compromise's both braking and suspension.
    I know EML et all have this arrangement so 'it must be right'. Not on my watch though.
    The brake torque arm on a motorcycle equiped with a rear caliper is attached to the swingarm, where both move in tandem. I'm not seeing that on the above set-up.
    Just my thought's. No offence to anyone.
    #9
  10. Ducatiparts.110mb

    Ducatiparts.110mb Adventurer

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    please read more and speak less
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  11. val. h.

    val. h. On the wrong planet

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    This is in the main a floating caliper, or it would be if the tie rod was attached to the vertical part of the forks with an articulated joint. As it is it will work in the same way as the OPs Unit forks above. IE all the braking forces are directed into the direction of the wheel. Therefore forcing the front axel down and the bike up. This causes the front tyre to loose traction much sooner than with a floating caliper, as it will lock up and start to bounce each time maximum extension of the forks is reached. Once reached the tyre will then flick back upwards into the air, momentarely leaving the ground, where it can do no good at all.

    It doesn't matter where the caliper is situated. Above, behind or below, the same forces will have the same end cause.






    If you look closely at the ends of the tie rod that fixes the caliper to the vertical fork leg, you will see that they are rose/rod end type joints. These allow the caliper to move up and down vertically as the axel moves up and down.

    Because of this the tyre is able to continue to stay in contact with the surface of the road, soaking up any bumps or dips under braking in the same way as it would when rolloing freely. This gives the tyre much more grip under braking and it therefore much safer to use.

    Which would you preffer. Braking all the time or just part of the time the leaver is pulled? Maybe a little more reasearch needed?


    Val.
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  12. outfit

    outfit Been here awhile

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    val. h. - That Lockheed caliper set-up is mine and it is fully floating in that picture. It was fully floating for 15 yrs.

    I have now made it a fixed set-up and have been running like this for 2 yrs.

    I can testify that there is no difference in performance. The front end hardly rise's, the tyre stay's in contact with tarmac and breaking presure is constant, otherwise it would fail it's M.O.T.

    When the caliper's were positioned below the LL swingarm I had alot of front end lift.

    So yes, reasearch was indeed ventured on all front's and I feel I have the experience to speak out on my set-up.

    I cannot relate to one word you've wrote. But hey, mine is only seat in the pant's experience:lol3

    And as a foot note - perhap's floating caliper's are so to eleviate uneven surface pressure on the disc, much the same as floating disc's help in the prevention of warped disc's.
    #12
  13. BeeMaa

    BeeMaa Hack Pilot

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    Thanks Val.


    Thanks Claude.
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  14. val. h.

    val. h. On the wrong planet

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    Val.
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  15. outfit

    outfit Been here awhile

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    Struth...............your having a laugh or your not plugged in. It's okay I've a good sense of humour:wink:

    What does the front wheel run on? and what is that attached to?

    You've got the mechanic's of this all wrong.

    :huh Re-read your first paragraph.

    I'll substitute the word float for slide (no I'll not go there).
    #15
  16. claude

    claude Sidecar Jockey

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    Somewhere in the Hacks section there is a thread on leading links. Maybe someone can find it and post a link?
    #16
  17. cleatusj

    cleatusj Dirt floor engineer

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    I just moved my calipers to a fixed mount behind shocks from floating in front and the lifting stopped.
    #17
  18. Salsa

    Salsa Been here awhile

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    Back when I was building shocks (about 35 years ago), I had a customer who liked to hillclimb, but hated to come down. He had leading links put on his bike to make it rise when he but the front brakes on. No floaters here.

    I built a leading link front end for my 4130 sheet metal framed bike in 1969. I made a parallel linkage because I wanted it to be like a conventional set of forks.

    Now the whole message is that you can design the front end to lift or dive when you put the brakes on. With an equal sided parrallelogram for the linkage you get a neutral no rise or dive bike.

    If you move the linkage from parallel to closer to the swing arm pivot, the bike rises with brakes. In the limit the linkage goes to the pivot and makes a fixed caliper setup.

    If you move the linkage from parallel up from the pivot, the bike dives with brakes.

    Suit yourself.

    Don
    #18
  19. claude

    claude Sidecar Jockey

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    Good post!!
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  20. pops

    pops Long timer

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    Great post .:clap:clap
    I even undestood what you were saying :1drink

    Leading Link Designs

    http://www.advrider.com/forums/showthread.php?t=308801

    Cheers Ian
    #20