high speed tank slappin wobbles

[dale_1]

The other day coming home from work I had the first handle bar wobble of my XS11 career..... I have heard of many folks having this interesting occurence, but had never been in that situation. Once it started I tried a few ways to correct them and nothing worked..... I didn't want to just slow 'til it stopped I wanted to learn how to correct them at speed and safely. I tried braking evenly, fronts and rears separately..... no change...... slight acceleration: no better..... hard throttle twist: no help there either..... beginning to get worried about not being able to straight up cure it and learn something, I eased closer to the center line (the high spot that did it to me in the first place while passing) did a good strong hard counter steer to the white line then back to the yellow line...... all wobble was gone immediately. My rear tire is just getting to the wear bars and my front is about halfway on tread. I am due rear tire soon..... very very soon. So with this information in my skull, I have come to a realization. "When confronted by the wobbly goblin, a good hard front end countersteer torquing is just what she needed." The next time I get one I will try it again just to double check, but for those of you who find yourselves in a situation such as this, give it a shot and let's add to the arsenal against these nasty creatures. It sure worked for me. And like I said I was searching for a cure without just flat out stopping and pissing off the guy I just passed. It's better than getting plowed into from behind, just because my mistress wanted to mess my whole day up. Sometimes she is a bit jealous when she sees me staring at a XVZ or some of the V-maxs........

Ya'll give me some input here and let me know what you think. Remember I have just about 45000 on this one with me as the rider. We tend to think as one most days. I know there are far more XSives who have been in their particular saddle for longer, so feed me input.

[Pat Kelly]

How fast were you going?
The only time I've experienced this is from 125 to 129 MPH. I'm not going to do any hard steering inputs at this speed. I seldom go over 100 anymore anyway.

[John]

That must have been a pucker factor of about 10! Glad you're ok.

[dale_1]

approximately 90 as I was going back into my lane after passing someone......

rough center line and dry conditions..... one of very few here lately.

[oseaghdha]

Got the Wobbles Once

I used to lay down on the Virago, set my feet on the passenger pegs and put my left arm across the tank in front of my chin. (I found it was good for about 10MPH but mostly just to get out of the wind)

Anyway, one night twxt Ft Worth and Dallas, it got the death wobbles on me at about 85. I clapped on with my left hand and scooted back off the tank and it quit. I thought it was the added weight from me laying on the front end that caused it, but I dunno. Had good rubber and the steering bearings were tight. Kinda freaked me out a little.

I do think the road surface contributed to whatever was happening, because it never happened before or since even though I continued to "get down on the paint".

Can't lay down on my Special with these idiot Sting-Ray bars.

[trbig]

Try putting the bike on the center stand and see if you have any play back and forth on your rear tire and swing arms, but a bald back tire will make the bike do some funny things sometimes. Unfortunately, I know this for a fact! lol. Glad you're OK.

Tod

[prometheus578]

Harley had a similar problem several years back with similar lawsuits arising. Can't recall exactly what it was, but for some reason, "motor mounts" stick in my mind.
Hey GNEPIG... you out there?

[Erik the Red]

I had 'em once doing 45-50 on my Honda. It was coming into a tight curve too hot (to the right), and downhill to boot. It started as a little wobble, but progressed to full on thumb-mash for a couple hits. Thought for sure I was going to end up in the ditch. I managed to strong-arm it back into obedience as I slowed more. It was fortunate that there was no oncoming traffic, as I only managed to reign it in on the far shoulder. I drove a touch more reasonably the rest of the way home.

Only thing I can think of that may have caused it was possibly a panic-brake, causing the from to lock up momentarily. Since I was coming downhill in a curve, that *might have* lead to the rest of the bike trying to overtake the locked front. Front wheel gets pushed to the side, I push against the handlebar too much, sending it the other way, and it just teeters back and forth about that balance point due to a combination of momentum and adrenaline fueled over-correction until you manage to not overcorrect.

I have no idea if this could've been the reason or not, but seems plausible. I still like to push it, but I do so on roads I at least know a little better. -It's a good thing I didn't start on an 1100.

[oseaghdha]

Bad Wobbles
Looks like the rear is as much an issue as the front in that case.

[blkryno]

wobble

years back I was racing a crotch rocket with my 81 11 Special I don"t have a fairing or anything . When we got up over a 100mph
( even though my speedo says my bike will only do 85 ) I got this wobble and it scared the ---- out of me I thought the front
end was coming apart. I was able to keep it straight and ease it down using my back brake only. Gave me enough of an adreniline rush to last a few days. It seemed to me at the time that it was an air-foil type effect maybe the air rushing under that wide engine. Don't know, I just don't do that anymore.


81 11 SH

really.... ( don't fall down )

Keith

[TopCatGr58]

Yeah, my vote is partly the aerodynamics involved! I have a moderately modified 81SH, my trail is only about 2.5" instead of the stock 6" due to a front end collision 20 years ago that bent my steering neck directly inwards, but the Dealer/Shop didn't notice it when they repaired it! Have driven it that way ever since, turns very easily! And that's with 4" over length upper fork tubes as well!

But I've experience the wobble as well, with new rear shocks, tire, regreased steering bearings properly set, TKAT FB. I have a handlebar mounted windscreen! I did some welding reinforcing of the swingarm thinking that flex there was contributing to the problem!

But after that mod, I still experienced the wobble at 90+mph going over mild hills or such! Then I realized that the very square edged toolbox saddlebags I have mounted onto the rear probably have added to the reduced airstream! I removed them, and the speed that the wobble occured shifted up 5-10MPH, but I still had the homemade windscreen!

I'm sure I'll figure it out eventually, but for now, I just don't go over 90! T.C.

[wingnut]

I don't know TC. Last weekend I decide to air my 81SH out a little on a long stright road. No wind or grade. My bike is naked except for the TKAT FB. At +85, haven't found a real speedo yet, I started to get this wobble in the front end. I guess the mph was about 90- 100, new Dunlop E3s, and I've been thru this thing with a fine tooth comb. Only thing I noticed was the road was crowned a bit more than say a freeway and the surface was tar and chip so not really smooth. I've been that fast on other roads and not experanced this wobble. My solution for now is to not go fast there any more, but I'll keep looking also.

[malber]

Originally posted by oseaghdha
Bad Wobbles
Looks like the rear is as much an issue as the front in that case.

There is a phenomenon in flight called Pilot-induced oscillation where repeated over corrections are the cause of a crash. In that video it looks like the rider was trying to counter the wobble which only made it progressively worse until control was lost.

[dale_1]

remembering that this was at 20+ mph less than me and trbig were running in dallas a week or so back. On the way home from work yesterday I found that exact stretch of highway and made it do it again........ I was running just about 80 and it was very slight. Definitely caused by that particular high spot in the middle of the road. Right on the yellow line. I did a single hard counter to the right line and it evened up. So, that leads me to believe I didnt necessarily have to go from line to line and torque the forks both ways. Just one hard tweak was sufficient. I'm beginning to think that the most important thing is not to panic. I was expecting this one and the first one I was "learning something" so my mind was already made up both times to fix it. I have tried to induce it in other places but can't unless there is a major ridge at the center line. This particular spot brings it about better than any other. Oh, and for the record..... no T-Kat forkbrace. less than 100 under 60K on the clock. Everything still in stock configuration plus a windshield (not homemade) steering bearings reset at 40 grand. All rear components inspected thoroughly at 40 also. Like I said though I do have 1/2 life on front tire and 10 grand on rear that is now on the wear bars. New rear on order and I will try again when I swap rear tires. And.... in another 10 grand when it's time to put on new front and rear I will try it again. I believe I will find it to be tire related as well as road conditions.

I will try it without the windshield and see if there is any difference.

OK now for the pilot induced oscillation / porpoising: When I did correct it with input I only had to input two solid turns the first time and one the second, both with a predetermined destination. It makes me think that as long as you make a solid change in direction it will cure it. (rather than trying to correct the wobble) I never tried to correct it but left it going each time......

Until I get new rear rubber I will just not pass anyone at that particular stretch.

[trbig]

Until I get new rear rubber I will just not pass anyone at that particular stretch.

Mark Mark Mark.... the comments I wanna make on this one... lol. I'll be good... for now!