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Thread: Classic 1984 R100CS with High Speed Sway

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    Classic 1984 R100CS with High Speed Sway

    I have a 1984 R100 with 15,000 miles. I am the second owner and bought the bike in 1999 with 3,500 miles.
    For years I have been running Metzeler Lasertec tires with no problems or swaying at high speed (75 mph +).
    Two weeks ago I changed out my Lasertecs that were put on last fall with less than 1,000 miles to try out the new Continental Classic Attack Radial Tires. I am experiencing swaying at above 75 mph. Logic would say check the head tube bearings. They have been replaced years ago and still feel good.
    The new Conti Radials do have a more rounded profile than the Lasertecs.

    Has anyone had a similar problem and solution to swaying at high speed?

    Ted
    Richmond VA.

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    Administrator 20774's Avatar
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    Ted -

    These tires are pretty new and I haven't heard much experience with them. What tire pressures are you running? Are you running metric sizes or inch sizes. There may be an issue that the pressures need to be different than what you might normally run in a bias ply tire.
    Kurt -- Forum Administrator ---> 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!

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    I have the 100/90-19 on the front and 120/90-R18 on the rear. I put 34 lbs in the front and 38lbs in the rear.

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    I wouldn't hesitate to up the air pressure in the front at least a couple of pounds and retry your road test...see what happens. What's the cold inflation pressure on the side of the tire?

    I looked at Continental's website and of course they don't mention any specifics. On their FAQ page they list recommendations for their racing tire. 2.1 BAR (cold) and 2.25 BAR (hot). That's 30 and 33 in psi. Not really what I would have expected.

    I guess my recommendation is to try pressure a couple of psi either side of what you run now...see what happens.

    Could also be that the new tires have unmasked a differet problem, like weak springs in front, worn rear shocks, slop in the swingarm bearings.

    When you have the front tire off the ground and gently push the handlebars to one side or the other, do the bars move slowly by themselves to the stop. Or do they clang off the stops (too loose) or stay where you put them (too tight)?
    Kurt -- Forum Administrator ---> 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!

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    By "swaying" do you mean a gentle back and forth that feels mildly disconnected or do you mean a fast oscillation?

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    The handlebars move smoothly from side to side while up on the center stand. Not too fast and not too slow.
    The front forks have Race Tech Gold Valve Cartridge Emulators and Springs that were installed three years ago. At the same time the rear Ohlins shocks were overhauled.
    I will play with the pressure and check out the swingarm for any play.

    Is there a way to check for alignment of the wheels?

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    The swaying is fast enough to be unnerving but not fast enough to have the handlebars slapping the tank. I did have my steering dampener on max just to make sure!

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    I have heard it called "weaving." It is what often occurs if the steering is adjusted too tight therefore impeding smooth motion. Perhaps the Continental radials have revealed a problem that was masked by the Metzeler bias ply's? I would try it without any damping to the steering since that could very well be the easiest solution.

  9. #9
    Jim Carr
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    You have checked that the new tire is seated evenly around the rim?

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    Do you have loaded saddlebags on the bike, or a top case? If so, take them off and try the bike that way. On my R100GSPD I found certain tires would allow that kind of sway when I had weight on the back of the bike.
    Anton Largiader 72724
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    Anton, the saddlebags were on! I had them on going up to Bob's BMW on Saturday. All my previous high speed runs have been without saddlebags. I will try running the bike up to speed this weekend without the bags to see if that makes a difference. The swaying/weaving did seem to be induced by dirty air from cars/trucks as I was passing them. I added the damping to reduce the sway.
    I will also recheck the beads on both tires.
    The majority of my rides over the years have been off highway in the mountains of VA/WVA. Heading up to Staunton on Oct 8th for four days of riding in the mountains and would like to have this problem figured out.

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    "Weaving" as I call it, often feels like you are running along a seam in the road, or a tar strip on a hot day, even like grating on a bridge surface. There is not a rhythmic pulse or modulation at certain speeds as in a head-shake due to bad swing-arm bearings or bad steering stem bearings. It is definitely a creepy feeling.

    I had a brand new Harley Road Glide that was set up ****ty. I bought it from a dealership that I sub-contract for doing wheel balancing/truing/building when their "A" guy is out of town. When I installed a top box it developed an oscillating head shake between 36 and 45 mph. Since it was new and under warranty I took it to a dealership closer to my home. The tech was sooooo completely clueless and over-confident that I decided to fix it myself. I eventually wound up tightening the steering bearings past the factory recommended "fall away" settings. What I got was weaving. What eventually fixed the problem was pitching the Dunlop 402's with big white letters that say "Harley Davidson" and put on some Metzeler ME880's.

    Similarly, my son had a Yamaha RD350 that developed weaving. When you put the front end in the air the front end would "catch" right in the middle. This is because the loose ball bearings wore themselves a groove where straight ahead was. Turning it off of that groove at speed became difficult resulting in that weaving or swaying feeling that you describe. Disassembly, cleaning and re-packing was all it needed.

    It doesn't sound to me that any of the suspension and chassis components suffer from neglect or abuse. The steering damper by definition makes it harder to turn the bars. Maybe with better, more sensitive, easier rolling tires you don't need any damping?

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    Wobble or weave?

    In the old days we concluded that an Airhead would wobble if the steering head bearings were too loose, characterized by a fluttering back and forth of the bars, especially on deceleration at modest speeds. We concluded that an Airhead would weave if the steering head bearings were too tight, characterized by the bars being reluctant to return to center, and a swaying of the entire bike as the rider attempted to stabilize a straight line.

    It strikes me that the OP may be experiencing weave because the steering damper is set so tight that it is creating the same result as overtightened steering head bearings.

    Radial tires or not?

    Radial tires respond differently to the interface between the road and the wheel than bias ply tires. Generally speaking the sidewalls are more compliant. For cars this is desirable because it holds the tread section flatter on the road as the tread offsets slightly left or right as side loads are imposed.

    On bikes that are designed for radial tires this is accounted for in the tire design, the wheel shape, tire pressures, and the rest of the suspension and steering geometry. I have always heard that radials on a bike designed for bias ply tires was a no-no. I don't really know about that because I never tried it. I do know of some K75 riders who use radials that like them, but ....

    Trying to sort out handling issues can be scary - so caution and baby-steps in making changes is the way to go. My first try would be to progressively loosen the damper in small increments to see what changes.

    Then I would do the same thing, slightly increasing inflation pressures in small increments.
    Last edited by PGlaves; 09-26-2013 at 08:03 PM.
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    On the tire pressure -- the old general rule was to shoot for a 10% increase from cold to hot. If the increase was less than that, lower the cold pressure. I had an '84 R100 and the pressures you list sound too high to me.
    61 Gold Star, 76 R90S, 03 CBR600RR, '13 690 Duke, '14 Street Triple R

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    Quote Originally Posted by ccolwell View Post
    On the tire pressure -- the old general rule was to shoot for a 10% increase from cold to hot. If the increase was less than that, lower the cold pressure. I had an '84 R100 and the pressures you list sound too high to me.
    The operative words here are "old general rule". I don't believe this works anymore with the changing stiffness of sidewalls. I had a Dunlop 491 on the rear of my /7. I began to experiment to find the 10% point. The cold inflation pressure was going to be much higher than the max pressure listed on the sidewall. IMO, it just doesn't apply anymore.
    Kurt -- Forum Administrator ---> 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!

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