Steering wobbles

Discussion in 'Airheads' started by patanga, Jun 7, 2012.

  1. MightyManfred

    MightyManfred Adventurer

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    I've run Avon RoadRiders and Bridgestone Spitfires on my '87 R80RT and get over 7,000 miles on them. Between 12 and 14 k miles on the front.
    #21
  2. Beemerboff

    Beemerboff Long timer

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    Patanga - riding in Oz is not conductive to long tire life, especially in the drier and hotter states.

    Although I drag a bike out most days regardless of the weather I don't ride on wet roads much, and almost never on frost /black ice.And 3 months of the year it might be over 100f.

    Speed restriction enforcement means that most of my riding on sealed roads is on twisting back roads, on bumpy, slippery, spray seal, which of course is hard on tires.

    Our unsealed roads and tracks are crap too - most of them have a loose layer of gravel on the surface, so both wheels are permanently moving around , and spinning under acceleration.

    And its probably about time I had the rear shocks on the G/S and the /7 rebuilt too - both are well overdue, and that cant be helping things much.

    But riding style must come in to it too.

    I keep the wick up on the Beamers - I don't ride in groups so I can push on as I please, and I rarely get passed by anything.
    I ride real loose too , I usually ride on roads I know well , and I run hard up to my usually very late turn in point then chuck the bike over and into the corner and scrub my way through. I keep the bike moving around the road most of the time too.

    I inherited a set of Deathwings on my XT600, and I ride that completely different. The first time I chucked it into a corner the front 'wing stepped out a foot, so it gets ridden like it was on black ice - as near to upright as possible most of the time , and as much of the cornering done by weighting the footrests as by handlebar input. And I feed what feels like the 30 HP in real carefully too. Looks like I will be able to add another 5000 km to the 1500 km the PO put on them.

    I dont know how anyone can get 10,000 miles/16,000 km out of a tire. I try to imagine it, but all I get is a picture of a guide dog and a white stick----.
    #22
  3. patanga

    patanga BMWAirheadsDownunder

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    Hi BB & thanks for your feedback. Most of my riding tends to be day to day suburbs and city stuff, so not a lot of excitement there. I do go on week end rides at times and chuck the bike around a little, but not to the extent that I'm ever fully committed. Brisk riding yes, but I don't trust the public roads and traffic enough to step out in faith. There are too many roadside reminders for my liking. I run the pressures up at the higher end (40psi) and it's rare that I would get less than 10 - 12,000k's out of a set of tyres. I'm obviously not punting hard enough:)

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    #23
  4. supershaft

    supershaft because I can

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    Funny. Riding around suburbs wears my tires out faster than anything. At least the back tire. For how I ride, 40psi won't work. But lower pressures don't cost me any tire wear IMO. I think higher pressures wears the center of my back tires even faster but then again I don't ride to conserve tires although I do wish they would last longer!
    #24
  5. ozmoses

    ozmoses Ride On

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    It was not a contentious query at all; quite the contrary.
    My RS is only unstable at that exact speed range and after adjusting,readjusting sag,tire,tire pressure,blah,blah,blah I wonder why and, moreover, if it actually can be eliminated?
    #25
  6. supershaft

    supershaft because I can

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    And that wasn't a contentious reply! They all are! Some "gurus" claim that they can make airheads wobble free. 100% BS!
    #26
  7. ozmoses

    ozmoses Ride On

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    But what is it about that 50-30,literally, since it does not seem to occur 30-50?
    #27
  8. supershaft

    supershaft because I can

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    It's complicated physics if I remember right. The size and weight of most wheels and the rake and trail of most setups. Throw in the absolute weirdness of what our tires do. The tiniest bump and fork flex. Rider weight and so on.

    The slowing down part has to do with effective rake and trail, weight bias and engine gyroscopics. Something like that?
    #28
  9. ozmoses

    ozmoses Ride On

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    I don't know for certain, but that sound reasonable...
    #29
  10. supershaft

    supershaft because I can

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    Somethings I just accept for what it is. We all have bikes with that danger zone. It's easy to fall into coming into a stop sign or whatever and taking your hands off the bars to fool with your tank bag or what have you. BTDT!
    #30
  11. backroadbob.com

    backroadbob.com Roads Scholar

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    Before you do anything, check your wheels and wheel alignment. Almost no factory motorcycle has its wheels perfectly aligned and most, if ridden for any distance, have wheels bent beyond spec. Shaft drive bikes require computer laser alignment and the rack and jigs to align the front to the back wheel. Chain drive bikes can use tools like the old Hentner wheel aligner and use the chain adjuster to align the back wheel to the front wheel. Bent cast wheels require cold bending if you don't want to buy a replacement that's possibly worse than the one you have.
    #31
  12. JonnyCash

    JonnyCash turd polisher

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    I'm glad to read this thread. My swb/5 will shake if I take my hands off the bars, and I always thought I must have something slightly off in the front end. It never does anything creepy, as long as I don't take my hands off the bars. My RD seems like you couldn't make it shake for anything, which I think is counterintuitive, as it is tiny and weighs about 290, and is much quicker steering. Thanks everybody.
    #32
  13. supershaft

    supershaft because I can

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    That's another thing funny about wobbles JC. Some people swear there airheads are rock solid. I have never been on a rock solid airhead and I have ridden a LOT of airheads. Your RD is. I have heard other people cuss a RD up and down for tank slapping. Sure a lot of it is setup, etc. but a lot of it isn't. A lot of it is how you ride. If you are a hard and fast rider, you can be as smooth as glass and still get into a tank slapper now and then. If you are a hard and fast rider and you are not smooth as glass. Lookout and invest in a real good steering damper! It's weird science. Rest assured that it isn't just your SWB that does that. There might be something wrong with it and there might not.
    #33
  14. patanga

    patanga BMWAirheadsDownunder

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    Hey ozmoses; Please forgive me if you already know the answer to what I'm about to ask; Re your RS; There's a lot of extra weight up front as you know. What is everything like condition wise?.. (Eg; forks, springs, fluid, head bearings, bearing adjustment etc etc).. I just tweaked the head bearings on my S faring R80 with the result = significant improvement.

    Regards tyre pressures; I only run them up at 40psi as that is where I have got the best results on Battlax BT45's. I do enough varied condition riding and turns not to have the rear tyre suffer too greatly from the flat top syndrome.
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    #34
  15. ozmoses

    ozmoses Ride On

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    Patanga-

    Tire is well w/in spec in terms of tread & air, fluid changed annually, forks in good repair. Head bearings have not/ do not seem to require adjustment so I haven't. But perhaps I should.

    With the steering damper on "0" it is minimal, "1" or "2" really exacerbate it, oddly.

    Springs-really this began when I replaced the originals w/ Progressive brand. The same exact spring which makes my /7 "rock-solid"!
    #35
  16. patanga

    patanga BMWAirheadsDownunder

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    osmoses; Maybe the head bearings need a little tweak?.. I replaced a set on mine a few thousand K's ago and even though the steering felt ok, over time the bike developed the shakes. I knew the bearings had settled a little and adjusted them up slightly. It made a big difference. Obviously can't say with any certainty that's your fix but for what it's worth...

    I used to see similar issues a lot on 4x4's with swivel hubs on solid axles.. As the bearings wear they develop small divets (due to the constant straight line hammering they receive) in the centre position. These marks obviously grow over time and the shakes get worse as well. What I suspect happens to a lot of airheads is that the bearings get replaced when they are trashed but the real damage started a long time before with lack of maintenance adjustment. The slightest mark on the outer race might be enough to trigger the symptom. Combine that with all of the other issues that contribute to the shakes and it's any wonder it's an issue.
    ____________________
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    #36
  17. chasbmw

    chasbmw Long timer

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    Wobbles deaccelerating from 50-30 are almost always head bearings that are too loose.

    Just tighten a few Mm at a time until the wobbles go away.

    If you change headbearings you will need to readjust them after 500 miles as they settle into position.

    I would also add that if you are doing a full rebuild of a thirty year old bike, then new wheel, headstock and swinging arm bearings are a relatively cheap way of helping ensure decent handling and stability when you get to use the thing, better than obsessing over fork alignment to the last 1/10 of a
    #37
  18. supershaft

    supershaft because I can

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    I agree with all the above advise but I know from experience that you can have the whole thing brand new and set up this way OR that way, RS fairing or not, and they will sometimes still do it. Just about any bike with a conventional fork will under the right circumstances. There are definitely things that make it worse but making it completely disappear is impossible.
    #38