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Discussion Starter #1
I thought I would post here since I have not solved my problem.


I have a wobble in the front forks when accelerating rapidly around the 80-90+MPH. I have gone with a higher profile rear tire as many others have.


So far I have tried slightly stiffening the upper spring preload while also slightly increasing the rear preload. This helped but the wobble is still there.


I am not an expert and have read a lot about setting up my suspension. I do not have a second set of hands so I have not done that yet. I believe I will need to but do any of you have an idea on where I should look. At first I thought I had too little weight on the front end but then after thinking of the higher rear tire I was not sure if I now have too much rake.


Thanks to all that have some insights here...
 

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What is your weight? I see you have agt's, but how old are they? How many miles on them?

I found my agt a spec tires to be a complete motherfucker to set the bead on. It would have been very easy to not have a 100% beaded up tire.

Is this wobble there at all times, or just at that 80-90 spot?
 

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Discussion Starter #3
What is your weight? I see you have agt's, but how old are they? How many miles on them?

I found my agt a spec tires to be a complete motherfucker to set the bead on. It would have been very easy to not have a 100% beaded up tire.

Is this wobble there at all times, or just at that 80-90 spot?

The rear tire is about 6 months old and the front is about 3. I weigh 163 lbs. I have put about 1500 miles on the pair. The wobble is just on hard acceleration at higher speeds. As soon as I get off of the throttle it tracks perfect.
 

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Has this wobble always existed with these tires or did it just develop? An improperly mounted or non-concentric tire can certainly cause this problem. So too could an internal defect. If you can get the bike on a lift, spin the tires and check their run-out.

Tire pressure, tire balance (did you lose a weight?), damaged rim, looseness in the steering head, wheel bearings, or swingarm pivot.

The always-excellent Kevin Cameron just did a piece on this:
https://www.cycleworld.com/motorcycle-wobble-and-weave-making-sense-death-wobble-talk/
 

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Check air pressure, steering head bearings, check your sag front and rear!! A wobble is a symptom of something being worn or not set up correctly. The fact that it only happens under hard acceleration can also mean the front end is getting light....you are 163 pounds so that is possible. If everything checks out, install a steering damper....
 

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That sounds like real, legit headshake. A bad component will usually not appear...then go away. Usually a bad part might get worse, at speed, but if you pay attention, it will show itself at other speeds.

Now the thought is why. If you are taking these bikes up to speed, you have to know what condition the bearings are in . Wheel, swingarm, shock linkage and steering head. If a person cant do it themselves, pay someone to do it. Not doing/knowing and just hoping is foolish, stupid, and dangerous. Not directed at you. That goes for all of us.

Raising the back end, with a 190/55, tpis a great mod. However, doing so sharpens geometry and cuts into the margin of ...not safety so much, but call it set up error. Sharper geometry relies on the suspension to do its job properly, and set for you. The tire made a huge change in height. Your new taller tire, with its new, deep tread, raised the back end by at least 8mm, if not more.

The best idea would be to set up the suspension properly. Set the front and rear rider sag. If the back end is too stiff, or does not sag enough, it can cause this to occur.

A quick thing to try would be to lower the back and just leave the front as-is. This will change something. It should make it better. If it makes it worse, thats fine to, but be ready. You know what not to do. As you add preload and make the back end more stiff, you usually end up needing to add some more rebound damping in to stay as you were. Not much, try a 1/4 turn. Then reduce that 1/4 to 1/8. Raising both ends will do pretty much nothing.

A damper is a great mod, and everyone should have one. They are awesome. Much better to be able to use them rather than to "need" them. Adding one now is a band aid over something else. Hundreds of these ninjas have made this change with no issues, so its better to find out whats up with yours.
 

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That sounds like real, legit headshake. A bad component will usually not appear...then go away. Usually a bad part might get worse, at speed, but if you pay attention, it will show itself at other speeds.

Now the thought is why. If you are taking these bikes up to speed, you have to know what condition the bearings are in . Wheel, swingarm, shock linkage and steering head. If a person cant do it themselves, pay someone to do it. Not doing/knowing and just hoping is foolish, stupid, and dangerous. Not directed at you. That goes for all of us.

Raising the back end, with a 190/55, tpis a great mod. However, doing so sharpens geometry and cuts into the margin of ...not safety so much, but call it set up error. Sharper geometry relies on the suspension to do its job properly, and set for you. The tire made a huge change in height. Your new taller tire, with its new, deep tread, raised the back end by at least 8mm, if not more.

The best idea would be to set up the suspension properly. Set the front and rear rider sag. If the back end is too stiff, or does not sag enough, it can cause this to occur.

A quick thing to try would be to lower the back and just leave the front as-is. This will change something. It should make it better. If it makes it worse, thats fine to, but be ready. You know what not to do. As you add preload and make the back end more stiff, you usually end up needing to add some more rebound damping in to stay as you were. Not much, try a 1/4 turn. Then reduce that 1/4 to 1/8. Raising both ends will do pretty much nothing.

A damper is a great mod, and everyone should have one. They are awesome. Much better to be able to use them rather than to "need" them. Adding one now is a band aid over something else. Hundreds of these ninjas have made this change with no issues, so its better to find out whats up with yours.
Spot on and great advice! My guess is combining the taller rear tire with additional preload in the rear may be your issue. At 163lbs. you may have to back that out. Adjust your rider sag at both ends and shoot for sag to be 30-33% of total travel and assuming you have no other issues like worn steering head bearings, it should fix your issue.
 

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Rikifumi, i should have added the Dave Moss recommend. I know you have a lot of experience. If a person signs up as watches a few videos, i believe they can make their suspension a hell of a lot better and probably learn enough to deal with problems. Although he might not deal with your specific bike (so far), a viewer will see the pattern. Ac

His videos are excellent and they dont try to upsell.

The factory settings are a compromise that will work for anyone. That never works well for any specific user.163 pounds is at the lighter end of that "average rider" CRfan1 mentioned raising the back end, and thats right on.That was the last thing you needed to do.

That is the cool part about setting up motorcycle suspension. A bad reaction is as good as a positive reaction. Knowing what not to do helps as much as knowing what to do.
 

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I would start by checking the smaller things before getting into any parts.

What front tire pressure are you running? - I've found that too low pressure can cause some shakes.

When the bike is lifted, spin the wheel and see if it is still spinning straight.
Reset the settings on your forks as well. See if it is the same.
When the bike is lifted, you can also check for the bearings if you steer it side to side/lock to lock. Slightly flick it from side to side and see if it bounces back after hits the locking point.
 

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Things like this are one of the reasons I wasn't so quick to jump on the 190/55 train everyone else was on when I got to this forum. All things considered, it's a step away from stability.

Wobble under acceleration is the most common appearance and that's almost always a chassis setup issue but it could be loose head bearings. Man I fought that a long time on my last 675R, and that bike had a 22.9 degree rake angle.

What front tire pressure are you running? - I've found that too low pressure can cause some shakes.
Generally only a cause under deceleration.

Wobble under deceleration is harder to diagnose but more commonly head bearings. Tire pressure and wear fighting with the chassis among other things. People seem to think that one thing fixes wobble, but it's like a long equation that equals wobble at the end. Change one thing and the equation might not equal wobble anymore. That's why answers are all over the place. But the most common thing is head bearings.

To the OP: I first recommend checking bearing tightness. It's not too hard once you get a 4/8 pronged spanner socket and a low value torque wrench. But I've down it by feel with a motion pro clutch holder tool. But it does need a careful hand and a good feel for low torques.

Dave Moss hates steering dampers, saying they hide problems rather than fixing them.
 

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Discussion Starter #12
Problem solved. I went back out today destined to understand the cause. A little embarrassing but here it is. I had not lowered the Puig windscreen. I had it in the highest setting today and as I broke the 100mph it started wobbling again. I pulled over lowered the shade all the way and hit it again. It tracked perfect. I am sure I could have saved the embarrassment but if this could one day help someone else I figured I would own it.

Thank you all for the advice and council!
 

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That's funny but glad you figured it out. Good thing you didn't take it to a mechanic. You could've spent big money and they probably would've never found the solution.
 

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Stability comes from the additive effects of various factors: chassis geometry, weight distribution, tires, and as you can see above, aerodynamics. The same windscreen on a different set of tires, with another rider and setup, might not wobble. But again, the effect of all of them are felt in their sum. In this particular case, aero tipped it into the negative stability regime.

From having a Puig to examine in person, I'd say it has more frontal area than stock and would have more drag in the fully upright position.
 

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Problem solved. I went back out today destined to understand the cause. A little embarrassing but here it is. I had not lowered the Puig windscreen. I had it in the highest setting today and as I broke the 100mph it started wobbling again. I pulled over lowered the shade all the way and hit it again. It tracked perfect. I am sure I could have saved the embarrassment but if this could one day help someone else I figured I would own it.

Thank you all for the advice and council!
That, actually, isn’t surprising. Aerodynamics can make or mar your ride. That logic applies to helmets as well. Anyway, I’ve found that keeping the stock screen at the highest setting on a high-speed run isn’t aerodynamic-friendly. The front end lightens up whereas if you keep it in the lowest setting and hunch over the bars you get maximum downforce. Overall, I find keeping the stock screen in the middle position gives the best result with regard to protection and stability.

I also have the Skidmarx Double Bubble screen which I use for touring only. Interestingly, the screen works very well but only in the lowest setting. Any higher and the front end doesn’t feel as glued to the tarmac as I like. It’s the aerodynamics at play!
 

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Discussion Starter #19
I am going to set the sag as soon as I can find a copilot to assist. I have been doing a lot of homework so I believe I am good to give it a go.
 

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I am going to set the sag as soon as I can find a copilot to assist. I have been doing a lot of homework so I believe I am good to give it a go.
That is where you should start! As mentioned, that windscreen really shouldn't cause this...although it's adding to it. I have the same screen and get none of that behavior. The bike is rock solid. Go back to stock damping settings and use preload to get your front and rear sag set up. With that 190/55 in the rear, I would shoot for 33% in the rear personally.
 
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