Unstable at High Speed. Has Anybody Fixed This?
Thread Starter
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Road Captain
Joined: May 2021
Posts: 504
Likes: 271
From: Anywhere, USA
Unstable at High Speed. Has Anybody Fixed This?
Hello people 2021 FLHTK 8500 easy miles.
This bike is awful at high-speed.
I recently had work done but prior to that I had these symptoms.
The bike felt like it was wagging/flexing, like a snake going around corners at 80mph+ (highway).
But straight line high-speed was OK though controllable handlebar shimmy started at around 100mph.
Recently while having the new SE oil pump installed, I found out I had a bent crank so I rebuilt the motor, 131 166hp
To improve the handling, I installed the Tru-trac frame stabilizer.
This meant I had to swap out the Fullsac header (no clearance) for a Jackpot xxx.
I also swapped out the tires for new Metzler Cruise Tec. The bike has Ohlins Nix 22 front fork tubes and Ohlins Black line rear shocks.
I mentioned to the HD tech the bikes handling issues and it was suggested I Not use urethane bushings since vibration would be bad.
Now going straight, the bike starts to wag/shimmy at 90-100mph almost every time. It is controllable, but I have little confidence going any faster.
Going around corners I do not trust it at high speed +80mph.
The HD tech is top notch and he went through everything prior to reassembly.
He thinks it's turbulence from my fairing and rear top case.
I do not have a detachable top case and honestly love the storage. I have also balanced the weight in the saddle bags.
Anybody got any ideas other than don't ride so fast? Steering stabilizer? I have spent all the money and the bike is not fun with these symptoms.
This bike is awful at high-speed.
I recently had work done but prior to that I had these symptoms.
The bike felt like it was wagging/flexing, like a snake going around corners at 80mph+ (highway).
But straight line high-speed was OK though controllable handlebar shimmy started at around 100mph.
Recently while having the new SE oil pump installed, I found out I had a bent crank so I rebuilt the motor, 131 166hp
To improve the handling, I installed the Tru-trac frame stabilizer.
This meant I had to swap out the Fullsac header (no clearance) for a Jackpot xxx.
I also swapped out the tires for new Metzler Cruise Tec. The bike has Ohlins Nix 22 front fork tubes and Ohlins Black line rear shocks.
I mentioned to the HD tech the bikes handling issues and it was suggested I Not use urethane bushings since vibration would be bad.
Now going straight, the bike starts to wag/shimmy at 90-100mph almost every time. It is controllable, but I have little confidence going any faster.
Going around corners I do not trust it at high speed +80mph.
The HD tech is top notch and he went through everything prior to reassembly.
He thinks it's turbulence from my fairing and rear top case.
I do not have a detachable top case and honestly love the storage. I have also balanced the weight in the saddle bags.
Anybody got any ideas other than don't ride so fast? Steering stabilizer? I have spent all the money and the bike is not fun with these symptoms.
Road Warrior
Joined: Sep 2012
Posts: 1,253
Likes: 482
From: MA
Pretty common issue, though you have addressed most fixes - shocks and true track -
Check the tire sidewall. It should have an 81h on it...NOT a 74w. If its a 74w its too soft a sidewall for a touring bike and it will cause a wobble. I just went through that.
If that checks out, id do the fall away test to check the tightness of your neck. Too loose or too tight will cause a wobble. A lot are too loose from the factory.
Jack up the rear and try to move the swing arm side to side. With that few miles the bushings should be good but who knows. Any side to side movement will cause a wobble.
Double check your suspension settings, maybe play with them a bit and see if stiffening some things up helps.
The top case probably isnt doing you any favors so you can try taking that off, but it should be able to handle it.
Check the tire sidewall. It should have an 81h on it...NOT a 74w. If its a 74w its too soft a sidewall for a touring bike and it will cause a wobble. I just went through that.
If that checks out, id do the fall away test to check the tightness of your neck. Too loose or too tight will cause a wobble. A lot are too loose from the factory.
Jack up the rear and try to move the swing arm side to side. With that few miles the bushings should be good but who knows. Any side to side movement will cause a wobble.
Double check your suspension settings, maybe play with them a bit and see if stiffening some things up helps.
The top case probably isnt doing you any favors so you can try taking that off, but it should be able to handle it.
Thread Starter
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Road Captain
Joined: May 2021
Posts: 504
Likes: 271
From: Anywhere, USA
That was helpful.
Stellar HDF Member
Joined: Jun 2017
Posts: 2,322
Likes: 1,145
From: Oklahoma
Not withstanding everything in post #3, I'd also look at suspension settings. My 16 RGU always "wiggled" in long sweepers at 90+. I did SuperShox 14" with 1" lowering blocks, and it didn't really change anything. I did Legends up front... at first the wiggle seemed worse. Most notably on long concrete sweepers, where you get that "rhythm" bounce going concrete section by concrete section. So I went back out, without saddle bags, to a 3 mile stretch that is right by my house, that has 3 long lazy "S" sweepers in that 3 miles. I'd hit them at 90+, stop & stiffen the rear up a little, then hit them again... stop and tweak a little more. After 3 adjustments it was almost completely gone. I believe all I did was "tune" the back to match the front, basically getting the "bounce rate" the same in the back as the front, so they were in rhythm with each other.
With the new rear shocks, I could adjust them so they were really too soft, but still absorbed most of what the road threw at them... but mine just needed to be stiffened up.
With the new rear shocks, I could adjust them so they were really too soft, but still absorbed most of what the road threw at them... but mine just needed to be stiffened up.
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,419
Likes: 6,367
From: Honah Lee
At 8500 miles, the tires have a pretty good worn flat. As you roll over the edge, depending on speed and turn, it's one side or the other.
Fills like crap in turns just like you say.
And you also need the face the fact cruiser are not intended to be doing 80 in turns.
Slow down, and they say, smell the roses. Leave that silly high speed to the cage.
Bet a new set of Michelins would fix it but only for a short while.
That tire shimmies at 100 is tire balance and your guardian angel's knees knocking from fear.
Fills like crap in turns just like you say.
And you also need the face the fact cruiser are not intended to be doing 80 in turns.
Slow down, and they say, smell the roses. Leave that silly high speed to the cage.
Bet a new set of Michelins would fix it but only for a short while.
That tire shimmies at 100 is tire balance and your guardian angel's knees knocking from fear.
Last edited by Jackie Paper; Apr 26, 2023 at 01:20 PM.
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From: Pennsylvania
Along with looking at your steering head bearings, look at your swing arm bearings and set up.
Also any changes affecting your rake & trail (length of shocks/weight changes) will cause things to happen.
Front & Rear wheel alignment.
Front forks alignment in the triple trees, make sure they are not bound up and there is no stiction when the lowers move up and down on the fork tubes.
Damping and rebound of both front & rear shocks can affect handling also.
Most Harley Davidson motorcycles were not made to be Sport Bikes, that is why they are called Touring bikes.
I see you also have a Krauss Vector One axle adjuster on the rear, make sure it is set correctly and not causing any out of alignment issues.
http://www.thompsonchoppers.com/rake...il-calculator/
https://www.motorcycle.com/features/...and-trail.html
Also any changes affecting your rake & trail (length of shocks/weight changes) will cause things to happen.
Front & Rear wheel alignment.
Front forks alignment in the triple trees, make sure they are not bound up and there is no stiction when the lowers move up and down on the fork tubes.
Damping and rebound of both front & rear shocks can affect handling also.
Most Harley Davidson motorcycles were not made to be Sport Bikes, that is why they are called Touring bikes.
I see you also have a Krauss Vector One axle adjuster on the rear, make sure it is set correctly and not causing any out of alignment issues.
http://www.thompsonchoppers.com/rake...il-calculator/
https://www.motorcycle.com/features/...and-trail.html
Last edited by CoolBreeze3646; Apr 26, 2023 at 02:27 PM.