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Thread: Fork alignment

  1. #1

    Fork alignment

    Hi, I have posted about a fork saga in the past - I had a persistent clunk that never went away, after several rebuilds. I still have that - but that's not the question I have today.

    I just came back from a 1300+ ride - bike is a '72 R75/5, it was awesome and drove great! But at lower speeds (slowing down) the bike felt slightly unstable, wobbly, I thought I must be pushing on the handlebars in a diff way or I'm fatigued... At speed it felt fine.

    I just took a closer look as my front brake needed some R+R and I suspect my forks/sliders could be not aligned, or off a bit. I just put a straightedge across my sliders - and they have the two ridges on each and they don't line up, it seems that one is turned out a bit and the other is turned in...I haven't done anything to these after 'rebuildgate' so wonder if that could cause the unsettling feeling?

    thanks for reading.

    Chuck
    C R NY
    1972 R75/5
    1969 2002
    1982 528e

  2. #2
    The fork tubes themselves are likely mildly bent from miles of service. Up until they were removed, they were bent symetricaly and lined up. Once you pull them from the yokes and replace them, the bends go in different directions. Getting them lined back up will be a bit of work.

    What sort of ridges?

    I had a similar problem on my R90S and managed to correct it but I don;t remember just how. These days, I'd be tempted to replace the tubes but I imagine that's pricey.
    '13 690 Duke, '13 Daytona 675R, '18 Street Triple RS, 2020 R1250R, '19 Ninja 400 (track bike), '21 Duke 890R (gone but not forgotten: '61 Clubman's Gold Star, '76 R75/6, '84 R100, '76 R90S)

  3. #3
    Liaison 20774's Avatar
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    Ridges? I think he's talking about the early ribs that were part of the front facing portion of the sliders...see the left slider in this image:

    https://www.realoem.com/bmw/enUS/sho...diagId=31_0309

    If you get into rebuilding the front forks, Brook has a good page on that:

    https://brook.reams.me/bmw-motorcycl...-fork-rebuild/
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  4. #4
    Registered User STEVENRANKIN's Avatar
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    Other thing

    You could well have misaligned forks. However, there are other things to consider as well.

    What is your maintenance schedule for changing fork oil? when was it done last? When was the steering head bearings checked/greased/adjusted? Loose steering head bargains will cause high speed wobble or far worse a tank slapper. Over tight bearings or dry/shot grease bearings can cause duck walking at low speeds.

    Duck walking is a noticeable side to side weave at speeds below 20 or 30 mph. It can be caused by overtightened steering head bearings and dry or solidified grease.

    Another problem is sticking or notchy steering caused by worn bearings and races in the steering head. The bearings in the steering head don't spin like other bearings and get hammered over time by riding causing flat rollers and notched races. Dry grease (BMW had a period where the grease they used would solidify) can speed this up.

    A quick test of the bearings is get the bike up on the center stand with the weight off the front end and turn the forks side to side. There should be mild, no sticking resistance and they should fall moderately easily to one side or the other when released. Sorry, it is not easy to write about a "feeling". But the thing is to check for sticking, meaning the bearings are too tight or worn, or real fast drop from side to side meaning they are too loose.

    In all matters, it is most important they be tight, not loose, better to have a bit of duck walk than to have high speed tank slapper. Anyway, this is my experience, if you are near Rochester, stop in and I would be happy to chat and take a look. St.

  5. #5
    thanks for replies.
    - yes, the early ridges are what I was referring to - one twisted more than the other. I had to pull my wheel off to R+R the brakes and I couldn't get the axel back in, that's what alerted me to something is wrong.

    - I took off my fender and twisted them back so the axel would fit and spin freely. All seems okay - I am able to lift up the sliders and there is little resistance, of course from the springs...but they go up and down okay

    - I just changed my fork oil 3 wks ago - using Duane A's write up - perhaps when I tightened them up I caused the misalignment? Or they were like that from previous shops work (see next bullet)

    - Two years ago MAX rebuilt my entire front end from steering head bearings to every seal and buffer and springs in the forks. They did something wrong (a terrible consistent knock and metal shavings in the oil were symptoms) and it took over a year of going back 3 - 4 times to rectify...I still get a knock over the worst road imperfections, but they seem to work fine / excepting the recent 'wobble'

    - I have 'tested' the front end using the center-stand-flopping-from-side-to-side and they seem fine, and Duane A's other tests and they seem to pass...

    - So, I am left with my next step of putting the brake / hub / wheel / cable back together this week and take it for a spin to see if the sliders being off was an issue.

    - and the next - next step is to take it all apart myself and see if there is another issue...

    thanks again for thoughtful points.
    I'll keep you posted.

    Best, Chuck

    P.s. St, I WAS near Rochester last week!!! I'll reach out if I find myself in your neck of the woods again this summer
    C R NY
    1972 R75/5
    1969 2002
    1982 528e

  6. #6
    Registered User STEVENRANKIN's Avatar
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    Further information

    Further information always helps.

    I am sorry to hear Max didn't do things as should be done. This of course opens a whole new can of worms as to what can be happening now and if it can be related to their work.

    Duane' web site is A1 along with Brook Reams, Boxer two valve and Anton Largidare's.

    So, considering what you have just written, you are probably going to find misaligned forks or something worse causing the problem. Metal shavings in the fork oil is not a good thing they shouldn't be there. The fact they are leads to the first place I would look besides the misaligned fork legs you noticed and are correcting.

    Good luck, let us know how you make out. St.

  7. #7
    Hi St. For sake of clarity, MAX found the shavings - after repeatedly going back - they gave me my full money back AND then 'fixed' that issue...So they had a lapse but made good. The issue could be related to their work, but in general I'm fine with Max, it was not the most trouble free exercise.

    However, I try to do my own work now. I did align the sliders and will button it up and report back. If it doesn't fix it, I'll take the next step. Thanks for the notes.

    Chuck
    C R NY
    1972 R75/5
    1969 2002
    1982 528e

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