high speed wobble

[csj]

I went darkside last year, overcame odd handling issue
by increasing pressure to 40#. I like it now.

I noticed a high speed wobble (100 mph) on the first try.
Seven months and 5K miles later, nothing changed.

Has anybody else had this wobble, and did you find
any fix, like pressures, shocks, bearings?

Oh, 98 Tourer, hercules CT (205/60/16) on back, metzeler on front.
Rear shocks and front springs are original.

[roboto65]

Check your upper shock bushing they could be suspect well thats what caused mine and the Valks are known to go bad on the uppers. I went with FX6 Daryl he sells some and they have worked great!!!

[csj]

The wobble was not present just before going darkside.

Right after the Herc was on, the wobble happened.
Shock bushings?

I'll check em soon as it warms up again, goin down
to freezing tomorrow.

If I do find em worn/sloppy, is there something at a local
store i can replace em with?

[Hoser]

Darkside been known to do that above hunnert, main reason I don't use them.  Most folks don't cruise that fast, but sometimes on those long straight smooth Ks highways, I just can't help my self!    Is that a bad thing?

[cdwhit]

My experience is that high speed wobble can be a bear to track down. Sometimes it appears to be a bad or incompatible tire (since it happened right after "going to the dark side", that would be my first guess.)

A change in steering geometry, such as changing the rake.  If the new rear tire is a slightly different height than the original, you did that.  Sometimes it helps, sometimes it hurts.  If memory serves, more rake is more stable, but back cornering and less rake is more likely to wobble, but corners better. (My second guess, since this would have started when the tire was changed, but I don't think it would have enough effect to be an issue.)

Bad shocks (front or back). Conventional wisdom in the 70's and 80's when I was playing go fast was that stiffer rides increased high speed stability. A weak shock on one side can create a high speed wobble as slow as 50 or 60 MPH on a BSA!  I think this would have shown up on the old tire though.

I haven't removed the tire on my Valk, but if there is an alignment adjustment, poor wheel alignment can create some "interesting" effects at high speed.

Aerodynamics.  My BMW had an adjustable windscreen.  If the screen was all the way up, or all the way down, I had no wobble.  In the middle, sometimes I did.  My guess was that in the middle it was difficult to get both sides of the windscreen exactly the same height.

Someone mentioned tire pressure.  The rating on the car tire is for the tire on a car.  I don't know, but I would guess it's optimum pressure would be different on a much lighter vehicle like a bike.

"Notched" steering head bearing can cause a wobble in lighter bikes.  As heavy as the Valk is I don't know if I would notice notched bearings.

Good luck and let us know if/when you find the culprit.

[DFragn]

I had a high speed wobble @ about 54k. I could start to feel it at 65mph by 80mph I was uncomfortable with it. I put new tires(MC) on it - no help. Checked the head bearing torque. Alighned the forks. Replaced the head bearings. AND I still had a pretty bad issue.

I was doing 70 mph in rush traffic flow on a Chicago Expressway with Joanne following in the cage. As soon as I changed lanes the pavement transition upset the bike like nothing before. Joanne said she could see the rear wheel shifting side-to-side a total of about 6"

That's it. Replaced the swing bearings and all is fine now, even with a car tire installed later on.

My believe is since the swingarm bearings get so little movement (unlike wheel bearings) that they must not have been torqued properly from the factory. It took me almost 2 years to narrow it down.

Check all the little stuff first. If your confident it can't be anything else it just may be the swing.

[fstsix]

I bought a Falkin CT, and had took it to my friends MC shop to have it mounted, Got a call 2 hr's later said come and look at this tire it was swinging almost 1/2 inch side to side on the balance machine, Also AVON FAT Freddy from years ago bought from Honda Steeler and had them mount it on the rim installed on bike and @ 55 MPH it was jumping off the ground at rear   put a dial indicator on the tire it was 1/4 out of round, Thanks to the idiot @ the dealer for not being a professional and not caring for someones life or safety.  GoodyearTT 100+ @ 3rd gear no problems very common event daily for me.

[Ricky-D]

To say that installing a car tire on the rear of a Valkyrie will cause high speed wobble is an absurd fabrication with no basis in fact.

Just one of the many delusions used to justify an illogical stance against the "Darkside".

***

[RLD]

Check your steering head bearing also for a notch or if it's worn. Changing to a different rear tire may have been enough of a change to  make it a problem. How many miles on the bike? The higher, the more likely it's this bearing or shock bushings.

[sugerbear]

HEY RICK-D  chill out man.
that statement did NOTHING to help, only inflame.

as was stated earler, start with the little things, shock bushings, head bearings, etc.
which hercules CT do you have (style, #)?
how many miles on the bike?
play with the pressure, i've seen 28 -50 posted here

[Pete]

Anytime a NEW problem appears, its usually helpful to look at the most recent changes.
Although it may not always be a fault of the most recent changes.

If you are certain the problem did not exist before the change, it is logical to regress the last change. No matter what the change was. And it does not matter what anyone else says or thinks.

The problem with this approach is that we usually cannot accurately certify that the problem started with the latest change. Over time even slight wear patterns in tires can induce instability. And slight wear in bearings and bushings can do the same.

So check for wear patterns on tires and slight looseness in any moving parts. Wear patterns and loose fittings often show up at lower speeds by riding with only one hand on the bars with very light pressure. Be careful trying this as a fatal tank slapper can be induced easily.

Also have you added any accessories that might affect high speed air flow? Higher speed weaves often are aero initiated or stress (read flex) initiated.

Good luck

[R J]

I went darkside last year, overcame odd handling issue
by increasing pressure to 40#. I like it now.

I noticed a high speed wobble (100 mph) on the first try.
Seven months and 5K miles later, nothing changed.

Has anybody else had this wobble, and did you find
any fix, like pressures, shocks, bearings?

Oh, 98 Tourer, hercules CT (205/60/16) on back, metzeler on front.
Rear shocks and front springs are original.

Okay, what tire are you running, brand and size?   What was the air pressure, what bike ya got, Std, Tourer or I/S?     

Have you changed windshields recently?

A very soft sidewall will cause that.  You have seen dragster go down the track and the tire buckle all up, that will cause a wobble big time in a motor.

[csj]

Thanks for the replies so far, lots 'o good stuff.

The car tire is a Hercules G3000H, symetrical tread pattern.
P205/ 60R16. It was the best price CT I cold find in town.

The front and back tires were both changed together in Sept.
I started out at 32# in the rear tire, it was tougher to keep her on the road, went to 40#, totally different, much better handling. Then I got the confidence to go out on the highway and let her rip.
 Wobble about 100mph.

There are no accessories on the Tourer, 70K miles, no notch in the
steering head bearing.

This is like a classic 'instability', or oscillation that could be
smoothed out by a damper, snubber, or could I say
horizontal shock. Just sayin.

Once it warms up out there, I'll try everything that was mentioned
especially pressures, swing bearing, bushings. I'll reply in a few days
after doing some investigation

[Gryphon Rider]

Shock bushings?

I'll check em soon as it warms up again, goin down
to freezing tomorrow.

If I do find em worn/sloppy, is there something at a local
store i can replace em with?

Get the green shock bushings designed for the VTX but perfectly fit the Valk.  Much more durable than the crappy Valk OEM bushings.  Honda part # 52489-HN0-671

[1FAST6]

I went through the same thing a few years back with a Cooper Zeon.  After I cleaned out my drawers, I checked everything.  Finally went back to a MC tire (Bridgestone Battleax BT020 200/60-16).  Almost threw the bike into the ditch first time I leaned her into a turn, but got used to it pretty quick.  125+ and rock steady immediately after making the switch.  Not trying to start anything with the Darksiders, just sharing my experience.  Every bike is different, as is every rider.  No one set-up is right for every situation.  Gotta go with what makes you and your bike happy!   

[R J]

Going Darkside, from my experience with them.   Been there now for over 100,000 miles.

SIDEWALL...  If it is too flexible, you have to run at least 50# in it to stop this flex.   When the tire is worn out, get a stiffer sidewall one.

Best one I have found so far is a GoodYear Triple Tread.   I run 32# and MGM will set a little over 100 and hold the road like he was glued there.   I tried a Dunflop CT, and that one is to damn stiff......

I'd say just find one with stiffer sidewalls and go for it........

[wizard -vrccds#125]

CHECK THE SPEED RATEING ! Not all are Z rated, even with the sane name and brand. Tried a Falken that was not a Z. It almost killed me at 135 mph !

[Hoser]

HEY RICK-D  chill out man.
that statement did NOTHING to help, only inflame.

as was stated earler, start with the little things, shock bushings, head bearings, etc.
which hercules CT do you have (style, #)?
how many miles on the bike?
play with the pressure, i've seen 28 -50 posted here

Not down grading the Darkside, Just happy with the light side,  Some folks are just to sensitive, not trying to offend nobody, just  joining the discussion. Chill.   some of my best friends are darksiders.  hoser

[Farther]

I run 32# and MGM will set a little over 1K and hold the road like he was glued there.

  That's some serious speed there.

[Larry]

Haven't had a good flame job here for awhile. Nothing like a spirited Darkside/Lightside discussion to bring out the flame throwers. 

Regarding the topic, IMHO the flat wide CT with "square " edges will tend to follow road cracks and irregularities more which would tend to bring out any weak spots in the suspension and/or steering.  I wonder how the wheel balance is? That could influence a wobble too.

[SPOFF]

To say that installing a car tire on the rear of a Valkyrie will cause high speed wobble is an absurd fabrication with no basis in fact.

Just one of the many delusions used to justify an illogical stance against the "Darkside".

Not to start a firestorm here, but I believe something in the the Valkyrie geometry is sensitive to this. Remember the 1st generation Metzlers about 10 years ago? A lot of people were getting dangerous high speed weave from them. Metzler even redesigned the tires. (My bike showed no such tendency with Metzlers.) Some of the early Avons--the same thing--although a lot less frequently. So I wouldn't be surprised if some combinations of car tires could cause high speed wobbles on some Valkyries.  Again, I've got a $70 BF Goodrich on the back of my Valk, and it could care less. Seems to handle better than any bike tire I've put back there.

[Valker]

Mine has a high speed (110+) 'wandering'. I figured it was the car tire I run, but I really don't care as it's stable as a ship up to that speed. I really need to stay under that anyway. Of course, it might just be that I have 100K on my Progressive shocks, all the bearings in the forks and swingarm, and a leaking fork seal... Like I said, as stable as it is at all other times, I don't care.

[alph]

P205/ 60R16. It was the best price CT I cold find in town.

please, no offense meant, but it's better to spend the money and be safe then to save a buck and risk injury.

please, please, please!!!  don't skimp out on safety. 

[daytona]

Has anyone been happy with this size?

Quote from: csj on March 26, 2010, 01:29:29 PM
P205/ 60R16. It was the best price CT I cold find in town.

[MP]

I would suggest getting a "good" CT, not the "cheapest" thing you can find that will fit!  They last a long time!  Most negative comments about CT's come from those who put the cheapest car tire on they could find, in case they did not like it.  Guess what?  They did not like it!

Get a Goodyear or a General Altimax 205-60-16.  Use a good tire, your life depends on it!

MP

[fstsix]

Cost of tire sure wasn't what i was after, i went off the old tech board to get some referrals when i purchased the Falken Ziex......i guess maybe this should be updated. 2003, not flaming anyone just agree that word of mouth and trial and error, is the best advise. so.......what is the best CT as far as if ya want to spend a lot of money? http://www.valkyrieriders.com/shoptalk/CarTire/home.htm