Darkside wobble, wind, or preload?

JoeP

JoeP

Joined
Sep 5, 2011
Messages
580
Location
Frisco, Texas
Bike
2015 BMW K1600GT
I joined the Darkside a month or so ago and have been happy so far with one exception.

I've not had the bike up to any high speeds (above 80) until a week or two ago.

Each instance below occurred after rolling onto the throttle while changing lanes (from left lane to middle lane - 3 lane highway) to pass and staying on the throttle (except the 3rd time). I've noticed the significant buffeting with my old tires with the top box on but honestly never got up to high speeds with those tires so never experienced the oscillations as described next. The old rear tirre was severely cupped when I got the bike so it had a pretty good vibration above 80. I decided I'd go darkside when that tire wore out. I have a the Hankook on the back and a brand new PR2 on the front, both are balanced. I'm running 42psi front and back.

[1st time] I took it up to about 110 where I got a pretty good wobble. I believe the oscillations would've continued, if I had continued with the throttle, until the handles bars would've been slapping the tank. I back off, dropped about 20 mph and rolled back into it. I had a significant quartering tail wind. All was fine after I rolled back into it.

[2nd time] I repeated the above but with a significant quartering head wind. The results were the same. I did not roll back into the throttle.

[3rd time] I had a long straight away with a quartering headwind and nothing happened. I was not changing lanes or passing anyone. Smooth as glass.

[4th time] I repeated the above with no wind this afternoon with the same results/oscillations. I did not roll back into the throttle.

I've never touched the preload or spring adjustment(s) at all. I twisted the adjuster today and felt no clicks. I believe I need to clean out and add new fluid as prescribed here (thanks Mellow for the link!):

https://www.st-owners.com/forums/showthread.php?106715

So after I change the pre-load fluid, and before I make any adjustments, any suggestions or comments?
 
Joe, was this before or after you put the new front tire on? As I said in the PM, I think it's more rear-suspension related but I just remembered you needed a front tire.
 
The Yamaha V-Max had a similar problem...Usually after the tire had some wear. Burnouts were leaving the tire flat in profile down the center. The transition between flat and side caused the rear to search, or weave. Sometimes getting into a tank slapper so severe that it would take itself and the rider down. Tires on motorcycles are designed to work a certain way. Tires on cages are not designed to lean. Maybe some people are smarter than the engineers that designed these tires(who are paid pretty good for their extensive knowledge.) but, even though a hammer is made of metal and has a handle, you cant slice bread with it. Oh I'm sure someone will find a way to do it, but it is not the recomended way to do it, and someone will get hurt or break something before they figure it out. Just sayin':soapbox
 
JoeP_Dallas said:
I've never touched the preload or spring adjustment(s) at all. I twisted the adjuster today and felt no clicks. I believe I need to clean out and add new fluid as prescribed here So after I change the pre-load fluid, and before I make any adjustments, any suggestions or comments?
Click to expand...

+1 on checking the damping and preload... changing preload def changes how the front feels.

watch this vid; http://www.youtube.com/watch?v=CAhksxRCIik&lr=1

read this ; http://www.ntnoa.org/suspension_preload.htm

read thread; https://www.st-owners.com/forums/showthread.php?109248-Why-does-my-front-end-feel-lighter/page2
 
mean13 said:
but, even though a hammer is made of metal and has a handle, you cant slice bread with it.
Click to expand...

Thanks for the comment but I think I'm still gonna try to slice the bread with a hammer a while longer until I'm absolutely convinced the hammer is faulty. I'm not giving up on the dark side yet. Hard headed as I am, I don't believe the tire is causing an issue. So far, I'm digging this tire. It grips like none else and is smooth as glass and corners great too. If I can't solve the issue, I'm not too concerned either. Who cruises around above 100 anyway? I'll just keep it at legal speeds and be just fine.

Thanks for the suggestions guys and the links Tom! My steering head bearings are new and I feel they're adjusted fine. I believe my wobble may be more likely due to the rebound dampening. I'm going to experiment with it over the next few days. It may take me a while to prove/disprove the adjustments and post. I'm working a ton of overtime over the next few weeks so I won't be able to tinker with it too much. Today, I'll adjust the dampening a little and try it for a day or two back and forth to work. Of course, I'll have a screw driver with me in case I make too aggressive of an adjustment and have to back off immediately.
 
So if I understand it you fitted a car tire and want to know if it's the suspension or the wind causing a wobble :confused:
 
I'm unsure of what is causing the wobble, but feel it is most likely due to the dampening now. I'll be able to tell more after a adjust it to my liking. Time will tell......
 
If I read the original post correctly...the bike is fairly new to you; your previous rear tire was cupped, so you had never had the bike up to high speeds (the area where you are getting the wobble) before installing the CT; so the only tire you ever used when the bike was at higher speeds was the Hankook. I would say that there isn't any direct evidence its caused by the tire (though I won't say it ISN'T the tire either...we have no evidence either way). I know some have had wobble issues at those speeds even with MC tires, caused by a misadjusted rear shock, so I would start there. I also know my Hankook has been well into the triple digits, running between 110-125, several times with no wobbles.

Again...I'm not saying it isn't the Hankook, I'm just saying don't blame the tire for a problem just because its a CT. Some on here are quick to blame any problems on CTs...
 
A high speed wobble is a common issue with the bike, regardless of the tires...
 
I adjusted the dampener prior to driving to work. The wobble is much less but still there. My first adjustment was to rotate the dampener adjust screw until it stopped rotating it clock-wise. I backed it off 1 and 3/4 turns.

I'll see what a little more adjustment does tomorrow, weather permitting. We're supposed to have some huge storms here tomorrow so I'll ride home nice and easy and won't be testing any high speed wobble.

Interesting info regarding the wobble experience by the UK Police:

http://www.ridethatbike.com/ST1300/ST wobble.htm

A BMW rider writes...

Greetings, I ride a '04 RT as my own bike and a ST1300P for work. The ST is a nice bike for big roads and speeds...although it is very noisy and yes there is a wobble at 110+ depending on where the pre-load is set, how much you weigh and how much kit you have in the panniers. This wobble won't go away and can be quite alarming. It is due to a torque problem between the engine and frame. That's from Honda who came down to speak to us after we complained so much. 'P' spec bikes in the UK have had an aftermarket fix from Honda to try and minimize this but it still wobbles in the three figure region. If you have the screen up then the, wobble is worse and if you have the screen down then you can wave goodbye to hearing the radio.

... rear preload settings again but combined with rider weight, side bag weight and reference to the Honda European recall.
 
I've never ridden Darkside on my ST but I have for several years on my Triumph Rocket.

You say you are running 42 psi front & back. Have you tried varying the pressure in the rear, only that seems a little high to me. I run 28 to 30 in my Rocket rear, from a standard 42 with a mc tyre. You need less pressure in the car tyre to get the side wall flexing a bit.
 
1. I adjusted the dampener.

2. OK, rebuilt the preload adjuster for the back shock. It was nasty!

3. I left the tire pressure at 42 front and back.

My high speed wobble is pretty much gone. There's just a very very ever so slight wobble at about 140. I'm going to adjust the dampener just slightly over the next few days but believe my problem is solved. I won't be pushing the speeds much if ever again (never say never).
 
Glad to hear you're making progress.
The damper may well need that adjustment as you changed the unsprung mass a bit with the hancook.
 
DaveM said:
e: Darkside wobble, wind, or preload?

Quote Originally Posted by wjbertrand View Post
So if I understand it you fitted a car tire and want to know if it's the suspension or the wind causing a wobble
That's what I was going to say!!
Click to expand...

What I meant was, as hinted to in the title:

1. Did the dark side cause the wobble?

2. Is the wind causing the wobble?

3. Is the suspension causing the wobble?

I believe it was a little of all 3; however, think the wind had the least to do with it. I didn't change anything with the tire but adjusted the suspension to the tire's "unsprung mass a bit with the hancook" as ST1300R stated.
 
It sounds like the suspension adjustment was off, and the darkside tire made it more noticeable...though, to be fair, you didn't run at the speed where you had the wobble with the MC tire, so we can't be sure there wouldn't have been a wobble with the MC tire.

Wider tires, on any vehicle, require more precise suspension adjustment. I can't count how many times I've dealt with cage drivers who put on wider tires, then complained that they handled worse than the narrow tires. An alignment always fixed the problem. The alignment problem was there with the narrow tires, it just wasn't noticeable until the wide tires were put on.

If your wobble is gone now, obviously the ct wasn't the problem, because its still on the bike and there is no wobble.

Jim

Sent from my PB99400 using Tapatalk
 
Thanks for this thread Joe ! There are MANY of us that have not tried the car tire yet, but follow these threads with GREAT interest and anticipation that one day this will be my ticket to a
long distance ride without stopping mid point to change out tires. Really appreciate your input !

:plus1:
 
Tom Mac 04a said:
I personally don't think I be going over 140, so IMHO it's fixed!
Click to expand...

Agreed completely! I probably won't see 100 again, but I feel so much better now that it is smooth.

DaveST said:
Would you consider trying a MC tire just to see if it does the same thang?
Click to expand...

I'm staying with the CT for now. I am completely happy, satisfied, and convinced I made the right choice. It took a great deal of reading, research, and comtemplation before crossing over to the dark side, but I'm glad I did. I won't say I will not go back to a MC but for now I'm good with the CT.

One thing I will add is that I'm very concious of the splines, shaft, and u-joints. I'm paying particular attention to them. I've not seen a whole lot spoken about the extra pressures put on those components so I'm keeping a watchful eye on them. Time will tell how it turns out.

I'll extend an offer to you guys who would like to drop by and take mine for a ride and see for yourself how it handles, rides, and feels.
 
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