Funny Oscillation

[h2olawyer]

On my trip to Steamboat last weekend, I noticed something different was going on with the handling / feel of the V.  In higher speed sweepers, the bike would go into a steady oscillation.  It never did this before I changed the tires.  I took those same corners over the last couple years, at similar speeds with the bike running the SuperVenoms.  Felt steady as a rock.  Now, with the RoadRiders, the bike bobs & weaves.  It's most definitely not headshake - had that & know the feel.  This is lower in both frequency and amplitude. 

There were a couple other minor differences from past rides - I had my luggage on the bike (about 40 or 50 extra pounds).  Also, I was going maybe 5 MPH faster.

With much keener concentration, I could lessen the oscillation by decreasing the amount of pressure on the handlebars.  While this would help, the oscillation would never totally go away.  Slowing to 60 MPH - the oscillation was still there, but barely noticeable.

Talked with kwells about the issue & he said his Avon shod V does the same thing.  He mentioned that since we both are experiencing this issue, we should start a thread on the subject.

I guess what I'd like to know is:

Has anyone else had a similar experience?  What tires (brand, model & size) were you running?  Did you have extra weight (luggage, passenger) on the bike when you experienced it?  Could it be something in my riding technique?

I'm stumped here and am seriously thinking the RoadRiders are the problem.  I initially thought it was just me, but remembered kwells mentioning a similar issue that started last Summer when he put his Avons on.  That's what got me started discussing it with him.  Any suggestions, hints or tips would be appreciated.

H₂O 

[YellowJacket!]

Check your fork oil to make sure both are equal.

Also, I run my Avons at higher than Yamaha recomended pressure - usually 32 to 34 for the front tire.  When I get below 32, it has a really mushy feel and does not feel like it is turning correctly.  I've not tried to experiment with anything lower than 32 just because I'm afraid of what might happen.

David

[kwells]

you don't go by the Yamaha standard but by the tire manufacture.

I have similar oscillations and my fork oil levels are exact and freshly done.  I have the 83 shock upgrade, progressive springs, and have experimented with varying pressures.  I also will get the oscillation at highway speeds around 75mph or on uneven pavement such as grooved concrete. 

I am thinking about swapping to a different tire to see if this can be isolated as a tire issue.

[h2olawyer]

Thanks, David - my fork oil may be a bit off after doing only one seal.  Not significantly, but there may be a few cc's variance.

Avon recommends 33psi front & 36 rear for the RoadRiders on the Vision.  That's where they're set.

I'll drain both forks & get some new oil this afternoon, then use my large syringe to make sure the levels are exact.

The oscillation was not scary, but definitely unsettling.  We'll see if the oil level helps.

I get the oscillation on grooved concrete surfaces as well.  I didn't feel it on asphalt straights (aging chip & seal) when I was going 80 - 85.  (even saw the 'ton' once Sunday  8) )

H₂O

[macroars]

From time to time I have felt oscillation in my rear wheel. I have found out that it is at certain places, and I have made the conclusion that it has to to with a) asphalts waves (it is said that this happens from time to time due to temperature issues when laid out) that b)fits into the carved "snake" in my rear tire that c)makes my swing arm bearings move.

So this winter it will be swing arm bearing replacement here, for due to threads here it can take a while and some swearing...

[h2olawyer]

Fairly certain it's not my swingarm bearings as it wasn't doing this until I put the RoadRiders on & replaced a fork seal.  Didn't seem to matter if I was on older chip & seal or newer pavement.  I'm leaning towards a tire issue, but want to rule out other things as well.  Appreciate the input.

H₂O

EDIT:

I drained both forks and replaced the oil this afternoon.  The volume in each fork was nearly equal.  Maybe a couple cc's difference.  There was a little air in the left fork (maybe 2 or 3 psi) - none in the right.  Will go without air for now to see if that makes a difference.  Also, I loosened the fork brace, compressed the forks a few times & tightened it back up.  It's about to rain cats & dogs here, so I can't go for a test ride this evening.  Hopefully, I can get out for a good, long ride tomorrow.

[Night Vision]

I guess what I'd like to know is:

Has anyone else had a similar experience? 

H₂O 

yessir... my Brother's V was porpoising after he put on a new set of Battlaxes...
they were out of round!
DK sent an exchange set that were rounder.

worth checking to see if yours are round enuf  ;)

[Lucky]

I wouldn't rule out the swing arm bearings just because you have new tires.  the way your old tires wore was influenced by the suspention system.  it's entirely possable that part of the tire wear tended to keep a lateral pressure on the bearings, making wear in them unoticable.  new tires aren't exerting that same pressure, so the excess clearance becomes evident.

or i'm wrong...  :D

[h2olawyer]

Checked the swingarm bearings when I did the forks this afternoon.  No play at all.  Rear suspension is solid as a rock.

The only time I notice the problem is in high speed sweepers & on grooved concrete road surface.  At 85 - 100, they are smooth in a straight line.  Will take a good, long ride Saturday & hit some of the same corners again to see if the fork oil change & fork brace adjustment made any difference.

kwells is experiencing the same symptoms on his red bike.  His has around 5K miles on it.  (I'm 30 miles shy of 16,000.)  He's got new Avons as well.  Since Tractor needs tires, I may order a set of Pirelli Sport Demons this month, put them on Silverbike and put the RoadRiders on Tractor - at least temporarily - if these RoadRiders don't settle down.

I'm also going to contact the tech department of American Motorcycle Tire (where I ordered them) and see if they've had similar issues with the new Avons.

H₂O

[supervision]

  try lower presure, like 28/30,

[inanecathode]

Tee hee, i bought dunlops  :D :D :P :P

[supervision]

check out these continentals tk11, tk12

[h2olawyer]

Tee hee, i bought dunlops  :D :D :P :P

Comment still applies.   ;D   ;)   :D  I do like their GT501s.  The 404s are classified as "cruiser" tires.

Was curious about the Continentals.  Just not sure I like the solid center groove on the front tire.  Heard good things about the Pirelli Sport Demons as well.  Guess I need to talk to the tire dealer's tech folks to get some more info and recommendations.  Hope my fork work this afternoon has cured the problem.  Otherwise, I'll be looking for something else soon.  (like next week  ::)  )

The Avon website recommends the higher pressure - 33 front & 36 rear for the Roadriders on the Vision.  However, they also say to use a 90/90-18 on all years.  I may try lowering the pressure on my Saturday ride if the fork work proves unsuccessful.

Keep the ideas coming - I appreciate it!  I like the tires everywhere except high speed sweepers & on grooved concrete.  I can live with the grooved concrete behavior as I don't encounter it too often nor for more than about 20 miles at a shot.

H₂O

[Night Vision]

The only time I notice the problem is in high speed sweepers & on grooved concrete road surface. 

H₂O

ohhhh.... wallowing! I thought you meant bucking  ::)

when I put my then new Avon Road Runners on 3,500 miles ago, I noticed wallowing that I did not have on some cheap mismatched tires I was trying to run the fun out of.....

try loosening your steering head bearings.. worked for me

[jasonm.]

Okay...H2O, if your issue only happened when you had luggage on...it's the luggage. Also out my way we don't have concrete grooved pavement.  That could be the other critical factor. but Avon claims this tire is better at not following gooves. I have no such oscillation issues unless I load my travel trunk with a pile of stuff. Being it's high, it has a factor on handling.  You say holding on with less grip helps..that's strange?  Avon did not tell me when I met them in person, what to set the pressure at. I run 31 or 32psi. in front.  I have done 85+ thru hiway sweepers. Bike was easy to control. Maybe my fat ars helps the handling. Yes, I like to go rather "speedy" at times. 

[h2olawyer]

When I put the tapered steering bearings in, I had them too loose initially - went for a ride & got headshake.  Came back to the house, tightened them a little - second test ride, still some headshake but better.  A third tightening and the headshake is gone.  I think that if I loosen them at all, my headshake will return.  But I appreciate the idea.   ;D

My luggage is all soft bags.  I put all the heavy stuff in the saddlebags.  The laptop bag (just computer & external drive) & tail trunk (which held just my cordura riding jacket & spare gloves) was the tallest item, maybe 14 inches above the seat total.  Total luggage weight 40 or 50 pounds.  It could have been the issue.  This was the first trip I've made with the luggage in years.  This was the first long ride with the RoadRiders - they now have about 650 miles on them.

I'm not small, myself (220 - 225 lbs) and am riding faster than I used to.  What I noticed wasn't so much using less grip, but taking pressure off the handlebars, that decreased - but did not eliminate the oscillation.  The grips I have are sticky & I can ride with my hands relaxed & still turn the throttle without slippage.  Now, it could be that since I'm riding faster & approaching (but not yet exceeding) the upper end of my comfort level, I may be fighting the bike a bit.  Entirely likely.

The cornering oscillation is an entirely different feel than the squirming on the grooved concrete surface.  It actually settles down in the corners on the grooved concrete - but those corners are gentler & the speeds are a little slower as there's normally a heavier LEO presence.  The cornering oscillation has a very regular rhythm - the squirming is not rhythmic at all.  Like I said, I can put up with that since it is only a generally straight 20 mile or so section of US HWY 287 between Loveland & Longmont, CO.  I ride it whenever I'm headed to see Tanno or going to the track.

As for tire size / inflation info:

www.avon-tyres.co.uk/motorcycle/?page=fitment&method=fitments&manufacturer=66&id=1544&model=550&year=1983

Maybe they're right about their tire size needing to be a 90/90-18 front.  The skinny Vision rim may be distorting the profile too much.  However, if I do end up getting new tires, they won't be RoadRiders.  I liked the things they had to say about them, but with the rubber cracking issue & the issues kwells & I have experienced, I'll look elsewhere.  Sure wish they still made the SuperVenom.   >:(

H₂O

[h2olawyer]

Well, just returned from a fun ride.  Did a few sweepers at 70 - 75 with absolutely no oscillation or wallowing.  Couldn't get it any faster - lots of State Patrol & traffic on the roads I chose.   ::)  So, I'll have to take a weekday ride back up to where I experienced it initially & see if the problem is really fixed @ 80 - 85.  That's OK - I don't mind running up to Steamboat for lunch.   ;D  This time I won't have any luggage - except for the tank bag.

The front has a better 'feel' to it.  When I changed the oil, I added an extra half ounce per leg to stiffen things up a little.  It seems to have worked.  I also changed from Bel-Ray 15 wt fork oil to Spectro 15 wt.  (the only 15 wt the Yamaha dealer had in stock)  That may have made a little difference as well.  Even with no air, it didn't bottom out when I turned in to my driveway.  It's always bottomed there without air before.  I may try an additional click of preload on the rear as well.  (it is an 83 shock - both settings @ 3 currently)  Won't play with that setting until after I see how it does in the same corners I had the problems last week.

H₂O

[The Prophet of Doom]

I had wallowing with #1 on long sweepers at high speed.  Sounds similar - nothing too scarey, but enough to loose confidence in ploughing into a bend at 120kph. Michellin tyres if I remember correctly.  I had the wheels re-balanced and although the bearings seemed OK I replaced them any way.  Fixed my problem - it was like riding a new bike.

[h2olawyer]

Thanks roro.  The bearings are something I was considering.  I have a homemade version of the balancers most shops use (static balancer).  I might take them back off the bike & try a rebalance.  May even break the beads & spin the tires around to see if I can decrease the amount of weight it took to balance the tires this time.  All that extra weight may be an indication of a tire flaw as well.

H₂O

[inanecathode]

So what'd you end up doing to correct it?