Car tire/ Darkside options for BMW K75T

Discussion in 'Hacks' started by GHO100, Nov 5, 2013.

  1. GHO100

    GHO100 George

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    Hey folks,

    I'm looking for option to put some car tires on my 1987 K75T sidecar.

    <del>Front wheel is currently the stock 130/90-17, which is on the original rim, but using a leading link.</del>

    Front: 100/90-18

    Rear is currently a 120/80-18

    I'm having trouble finding options, other than compact/spare or temporary tires.

    Thoughts? I know the Germans get Beringer wheels, but in the US, I can't find anything equivalent.
    #1
  2. Melrone

    Melrone Long timer

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    Give Claude @ Stanley Motors a call he'd have what you need...They have car tire setups..You won't be sorry its the smart way to go for a sidecar setup...
    #2
  3. Steve In Ireland

    Steve In Ireland Been here awhile

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    Haven't you got that backwards? It is an 18 inch front wheel and 17 inch back wheel as standard.

    What I did was get an adaptor machined up and fitted a Smart car front wheel to the back of the bike

    [​IMG]

    [​IMG]
    #3
  4. GHO100

    GHO100 George

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    Changed to reflect the correct sizes

    Front 100/90 - 18
    Rear 120/80 - 18

    I like the idea of a spacer, but the Smart for2 wheels are expensive around here (at least from what I can find).

    Any idea if something like a honda civic wheel will work? I'm assuming that'll need a customer spacer.

    If I could get something without needing to make a custom part, I think that would suit my wallet best
    #4
  5. GHO100

    GHO100 George

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    Sent 2 PM's and an email...no response

    #5
  6. DRONE

    DRONE Dog Chauffeur

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    Steve in Ireland, your K75 is awesome looking! Can hardly believe it's a K75--looks bigger! You should post up some more pics of that in the Sidecars-Let's See 'Em thread.

    GHO100, you call yourself Crazy George, so this is a little crazy but guys have chopped off the rim then welded a car rim in its place. HERE Otherwise, then yeah an adapter and a car wheel.
    #6
  7. davebig

    davebig Another Angry Hun !

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    Claudes neighbor Harry Tarzanian will cut and reassemble motorcycle centers on automotive rims as well as Stroker may be able to do that also, I'd call Freedomsidecars.com they can put you in touch with either.DB
    #7
  8. gusanito

    gusanito Mindless Wonderer

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    I used a 15x4 Sport Star Drag Racing 4 lug wheel with an adapter. You'll have to make the adapter but the wheels are available for less than $100 shipped on e-bay.

    [​IMG]

    [​IMG]
    #8
  9. GHO100

    GHO100 George

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    Looks great! Do you use one of these on the front as well?

    What size tires?

    Thanks again, think I will go this route

    #9
  10. halflive

    halflive Been here awhile

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    I have had a Beringer wheel on my K75 but I changed it for an Smart rim with an aluminium adapter. The Beringer wheel is an assembled wheel, I had trouble keeping the air inside. Instead of a Smart wheel you can also use a wheel from a VW Bug. 14" is also possible, but you are limited by the with of the frame, in my case the panniers. Most 14" rims are to wide.
    See the lower part of this page
    #10
  11. gusanito

    gusanito Mindless Wonderer

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    Thanks.
    The tire is a 145/65/15. My front wheel is stock.
    #11
  12. GHO100

    GHO100 George

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    I used this little tool for a comparison of tire sizes:

    http://www.tacomaworld.com/forum/tirecalc.php


    I get the following results comparing the current 120/90-18 (had to use 85)
    http://www.tacomaworld.com/forum/tirecalc.php?tires=120-85r18-145-65r15

    [​IMG]

    This seems like a hefty difference. Did you notice it? I know there's also a 165/80-15 available which would yield the following:

    [​IMG]


    But I'm not sure the 6.5" width makes all the clearances. Did you test anything else? just checkin


    #12
  13. Steve In Ireland

    Steve In Ireland Been here awhile

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    There is a very noticable drop in the gearing, but all to the benefit of driveability and giving the clutch and easier time. Makes the speedo read a bit high, but no big deal. Are you sure your back wheel is an 18 inch? The original rear wheels on my K75 and K100 were both 17 inch.
    #13
  14. warkshop

    warkshop uncbob Supporter

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    Some 'devils advocate' thoughts . First, in my experience the radial car tire with its flexible sidewall tend to make the outfit feel like it has a flat back tire, sloppy. They say you get used to it, i'd rather not. The rather high cost of special wheels/spacers and such mean you have to drive your outfit a zillion miles to actually have saved any money over using bike tires. Yes, car tires last a long time and are cheap plus give a bigger footprint. Premium brand name bike tires do a pretty darn good job though,,no 'squirmys,,,but sadly :freakyno 'show and tell' points.
    #14
  15. gusanito

    gusanito Mindless Wonderer

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    Like Steve in Ireland say, you notice the difference, particularly when you're carrying a heavier load, but it's an improvement. The clutch doesn't have to be ridden from a dead stop to get you moving. I like it and on the speed, there's ~14% difference from stock.

    I just measured the distance from the tire to the swingarm and it comes out to a bit over 20mm. There's plenty of room on the muffler side, so according to your chart, you should be able to put on the larger tire.

    As far as the spacer being costly, it may be, if you have a machinist make it for you. It took me a few hours to make my spacer on my small mill/lathe and I'm not a trained machinist. Don't ask for measurements or drawings, I cannot find them anywhere. Next time I do a tire change, I'll measure everything and keep a record of it.

    [​IMG]

    [​IMG]

    [​IMG]
    #15
  16. GHO100

    GHO100 George

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    This is all awesome information fellas. Can't thank you enough!

    I have a friend with a lathe who is looking for projects to get his skills up, so there's that, but I do understand the common argument to go with the simple option.

    A conversion would cost me:
    Machining (at least materials cost)
    A new wheel
    Car tire.

    I think very frugally, that would push me to about $250.

    For about $110 shipped, I can get new MC tires for the front and rear.

    I did confirm the front is a 100/90-18, rear is a 120/90-18 (the rear seems to be a sort of goldish color, so i don't know if this is the original wheel)
    #16
  17. AL-58

    AL-58 BMWs make good landfill

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    With a 120/90-18 rear you should have a drum rear brake. You will notice all the bikes with adapters and 15" wheels bolted on have disk brake rear ends. As the drum for the brake is actually part of the back wheel I don't think you can do this.

    You can convert to a disk brake rear end, but that is a fair bit more expense.

    Al
    #17
  18. GHO100

    GHO100 George

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    Now that would have been really helpful before information to know before I bought a wheel and a tire.
    #18