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Discussion Starter #1
I had a tourist from the PNW in my shop yesterday afternoon. He had gone down at about 70 mph by his best guess, on a straight section of highway.
The incident was observed by a following motorist and an oncoming deputy sheriff, near Yellowstone Nat'l Park. The deputy sheriff told the rider that he was certain that he would be calling the coroner, instead of assisting the rider to pick-up his heavily loaded KLR. The front tire left numerous crescent shaped skid-marks on the highway before going flat down.

The rider said that the bike had had higher speed wobbles even on the OEM tires since new.
The rider wished for me to attempt to straighten his twisted front forks, so his barely bent handlebars were better aligned with the front wheel. The upper fairing was held together and onto the bike with Duct Tape and he was continuing on south to Colorado & beyond. The RH Tusk pannier was well bent and the lid no longer could be fitted & latched, so held sort of on with bunjie cords.

As I stepped out the door to look at the situation, I commented from 40 feet away from his bike that I did not like the scalloped look of his D606 knobby front tire. He replied they were only about 1300 miles used. I pointed out the direction of the Vee pattern of the front knobs and also asked about his tire pressures. He claimed mid 20's psi.

His bike had a center stand & the 2 of us hoisted the overloaded mule up. I loosened the upper triple clamps and the lower axle clamps and straddled the front wheel and wrench on the handlebars to un-twist the forks, several times. All while discussing various possibilities of the cause of the incident. I then loosened the front axle nut, it was no where near the 65 ft lb recommend torque. Discussed that possibility.
With a few more hearty twists I had the front tire, front fender & handlebars pretty much back in-line. I offered to rotate the front D606 to the inverted 'V' contact pattern and showed him a Shinko E705 front with Front & Rear directional arrows to help explain. But also suggested that it might be better to just install the Shinko to get rid of the severely scalloped front D606. The Rear D606 was severely 'Squared Off' also, and we lightly discussed its possible bearing on the incident.

Finally I handed him a digital tire gauge for him to check his knobby tire pressures.
18 PSI in the severely scalloped Front tire and 20 PSI in the squared Rear tire. I've no idea how much or how little dirt roads he had ridden to get to Yellowstone Park, but it is 160 miles of asphalt from Grassy Lake road in the Rockefeller Parkway between the parks (Grand Teton & Yellowstone) to Lander WY.

I suggested a minimum of 34 front & 34 rear to continue his trip to Rawlins WY, on asphalt and on into Colorado. Which he conceded to inject. We tightened all of the previously loosened hardware. We could not feel any slack in the steering bearings and the top stem nut was tight.

He suggested that he would call me from some point farther south with an update and rode across the street to the restaurant for a hamburger & fries.

I recon the he just has a 'shit happens' attitude and wish him the best. I hope that he has no more wobbles & does call me.

The moral of this story might be, higher speeds need higher tire pressures. I hope I hear from him, soon.
 

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Interesting tale. He seems to have been a lot more nonchalant about his situation than I would have been. I believe I would have been asking you if there was a store nearby where I could go get some replacement underwear while waiting on you to mount me some new tires.........

Then again, I'll admit I'm probably overly sphinctorial about tire condition and pressures. The insides of my riding gloves are probably dirtier than the outside due to putting them on uncleaned hands after spinning/inspecting tires and checking pressures.
 

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Scary sheit.. after that I’d likely stop riding bikes all together.
I’m not sure his continuing on is big balls, or stupidity.
 

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I’m understanding that he rode away on the Dunlop’s??

I have a feeling you may be reading about him rather than hearing from him.
 

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Discussion Starter #5 (Edited)
Yes, he intended to continue his journey on the Dunlop D606's.

I should have showed him the partially used dirt bike rear knobby leaning against my outside wall, worn out from the Inside. The cords are chaffed loose on the inside and that allows them to 'saw thru' the inner tubes. This is also caused by Too Low of air pressure & too much flexing.
 

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Worn D606's and low pressures sure could have been a contributing factor though I doubt it was the cause of his accident. Heavy loads, load distribution, aero, suspension setup and the rider are all more likely root causes IMO.

Cheers,
Dave
 

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Worn D606's and low pressures sure could have been a contributing factor though I doubt it was the cause of his accident. Heavy loads, load distribution, aero, suspension setup and the rider are all more likely root causes IMO.

Cheers,
Dave
I suspect all of the above made some contribution, but it is necessary to match tire pressure to load and speed. If a bike is loaded at or above the GVWR, then the tires should be pretty darn close to their maximum rated pressure also. The KLR has a very flexible frame and forks compared to other bikes I have owned (well no worse than my old 100 Kawasaki). Tires get more flexible when they are hot as anyone who changes their own tires knows very well. A heavy load with low tire pressure will get the tires quite hot and that combined with the already flexible tires due to the low pressure and the flex in the forks and chassis means that a tank slapper is just waiting to happen.
 

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I suspect all of the above made some contribution, but it is necessary to match tire pressure to load and speed. If a bike is loaded at or above the GVWR, then the tires should be pretty darn close to their maximum rated pressure also. The KLR has a very flexible frame and forks compared to other bikes I have owned (well no worse than my old 100 Kawasaki). Tires get more flexible when they are hot as anyone who changes their own tires knows very well. A heavy load with low tire pressure will get the tires quite hot and that combined with the already flexible tires due to the low pressure and the flex in the forks and chassis means that a tank slapper is just waiting to happen.
Yep; as I said, I think the tires/pressures could well have been a contributing factor and he had a bad tire choice (worn D606 front in the "backwards" direction) and the tire pressure was lower than I use even offroad......but I just don't think it's THE reason

...and while I'll concede the frame and forks are more flexible than some other bikes, I still think weak suspension (inadequate springrate AND damping) is a large contributor combined with suspension set up (sag) and loading. I personally don't think the fork diameter is as much a problem as many do.

FWIW, I rode my KLR with my D606/MT21 combo at 22PSI at 70+mph in sweeping highway turns with one hand on the bars with zero instability at the last dual sport event.

2 cents,
Dave
 

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Yep; as I said, I think the tires/pressures could well have been a contributing factor and he had a bad tire choice (worn D606 front in the "backwards" direction) and the tire pressure was lower than I use even offroad......but I just don't think it's THE reason

...and while I'll concede the frame and forks are more flexible than some other bikes, I still think weak suspension (inadequate springrate AND damping) is a large contributor combined with suspension set up (sag) and loading. I personally don't think the fork diameter is as much a problem as many do.

FWIW, I rode my KLR with my D606/MT21 combo at 22PSI at 70+mph in sweeping highway turns with one hand on the bars with zero instability at the last dual sport event.

2 cents,
Dave
I don’t think there is a THE reason, as changing almost any of the variables may well have eliminated the problem. However, tire pressure is probably the easiest one to change and thus I would consider it the primary issue as it is the one that could have most easily been changed to avoid the problem.

Springs and shocks are very unlikely to be a factor in a high speed wobble. The suspension is hardly ever moving much until things get really ugly. The issue is a resonance between the tire, wheel, fork, and frame due to their flexibility.

I have not had any noticeable instability with my KLR either, but I have had it only up to 70 or so. However, the flex in the forks and chassis is very pronounced compared to my BMW. If I do a quick swerve on the KLR, I get oscillations at both the start of the swerve and the recovery that are very unnerving. My LT on the other hand, is rock solid. It enters a swerve and exits a swerve with no noticeable oscillation at the transitions. It simply goes where it is pointed. However, it has a large casting for the main frame and the Hossack style front suspension is very rigid. And the cast wheels are more rigid than spoked wheels, so it is no surprise that it is far, far more solid during high speed transitions as compared to the KLR.
 

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I don’t think there is a THE reason, as changing almost any of the variables may well have eliminated the problem. However, tire pressure is probably the easiest one to change and thus I would consider it the primary issue as it is the one that could have most easily been changed to avoid the problem.

Springs and shocks are very unlikely to be a factor in a high speed wobble. The suspension is hardly ever moving much until things get really ugly. The issue is a resonance between the tire, wheel, fork, and frame due to their flexibility.

I have not had any noticeable instability with my KLR either, but I have had it only up to 70 or so. However, the flex in the forks and chassis is very pronounced compared to my BMW. If I do a quick swerve on the KLR, I get oscillations at both the start of the swerve and the recovery that are very unnerving. My LT on the other hand, is rock solid. It enters a swerve and exits a swerve with no noticeable oscillation at the transitions. It simply goes where it is pointed. However, it has a large casting for the main frame and the Hossack style front suspension is very rigid. And the cast wheels are more rigid than spoked wheels, so it is no surprise that it is far, far more solid during high speed transitions as compared to the KLR.
I'm familiar with other bikes; I've had 41 so far. I still say the suspension, setup and loading are more likely "primarey" causes than tires or spindly forks but I concur that a number of "weak links" add together to manifest the problem and I agree that I would start on this particular bike by changing the tires and increasing pressure to try to reduce the effect.

FWIW, my standard wobble post:

Way too many people think that addressing the symptoms by dealing with handguards, fenders, fork braces, etc. are the answer rather than dealing with the real issue which is related to suspension setup and loading. I'm not convinced that the KLR is any more susceptible to instability than any other bike with long travel, lightly damped suspension and the Owner's have a propensity for severe and uneven loading.

There are some problems that need to be checked;
- bad/lose head bearings
- condition of wheel bearings and suspension bushings
- wheel and tire condition and appropriate tire pressures.

.....beyond that, It's settings;
- proper sag settings and adequate damping
- proper bike loading
- avoiding inappropriately un-aerodynamic loads

addressing the symptoms rather than the cause can help but IMO shouldn't be done until all the aforementioned items are checked and corrected if necessary. Nonetheless these can help stability;

- fork brace
- smaller fender or lowered fender (I use a polisport as I hate both the supermoto and low mounted fenders)
- consider tank bags instead of putting everything in huge panniers which affects both weight loading and aerodynamics.


My 2001 had some high speed issues that went away as soon as the sag was set properly....and after my Cogent suspension was installed, both my KLR's have been rock steady.....even with full knobbies and low tire pressures (20 - 22PSI). Lastly, as others have mentioned, the rider also plays a part; keep a relaxed light grip on the bars and don't tighten up. Changing your position (move forward/lean forward) can help too.

2 cents,
Dave
 

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I'm familiar with other bikes; I've had 41 so far. I still say the suspension, setup and loading are more likely "primarey" causes than tires or spindly forks but I concur that a number of "weak links" add together to manifest the problem and I agree that I would start on this particular bike by changing the tires and increasing pressure to try to reduce the effect.

FWIW, my standard wobble post:

Way too many people think that addressing the symptoms by dealing with handguards, fenders, fork braces, etc. are the answer rather than dealing with the real issue which is related to suspension setup and loading. I'm not convinced that the KLR is any more susceptible to instability than any other bike with long travel, lightly damped suspension and the Owner's have a propensity for severe and uneven loading.

There are some problems that need to be checked;
- bad/lose head bearings
- condition of wheel bearings and suspension bushings
- wheel and tire condition and appropriate tire pressures.

.....beyond that, It's settings;
- proper sag settings and adequate damping
- proper bike loading
- avoiding inappropriately un-aerodynamic loads

addressing the symptoms rather than the cause can help but IMO shouldn't be done until all the aforementioned items are checked and corrected if necessary. Nonetheless these can help stability;

- fork brace
- smaller fender or lowered fender (I use a polisport as I hate both the supermoto and low mounted fenders)
- consider tank bags instead of putting everything in huge panniers which affects both weight loading and aerodynamics.


My 2001 had some high speed issues that went away as soon as the sag was set properly....and after my Cogent suspension was installed, both my KLR's have been rock steady.....even with full knobbies and low tire pressures (20 - 22PSI). Lastly, as others have mentioned, the rider also plays a part; keep a relaxed light grip on the bars and don't tighten up. Changing your position (move forward/lean forward) can help too.

2 cents,
Dave
http://dl.vdocuments.mx/download/3c73ca8d95d2896c0b1808877ccf6ff90beca07dce3c6dd58530970be155fbe20c23ead210c63bb276a19a9de1419ecaf66ac88a69f015b94ef714b9b2d3a1f5D892e+EMJZKtwTsDR5Rm/pApp1tSY3mdA2hVFVzJ8DY+6/mQ9HHJP6S+44PzOYorF5A3Gw+VJg1iHzOykVOqkKovTL9lfErn/0n8OA5BW8n42lebEGe1LrgtEiCdOuUn

Lots of things come into play, but I believe, as apparently does pdwestman, that tire pressure is a key factor and everything I’ve ever read on the subject agrees with that, assuming that there is no other play in the system from worn wheel bearings or steering head bearings.

Loading of the bike is a secondary factor.

Suspension setup is a tertiary factor.

So, if you have a high speed wobble, I would troubleshoot in this order:

1. Play in the steering/frame (front wheel bearings, steering head bearings, loose spokes, etc.)
2. Front tire pressure and sidewall stiffness (need to have the right tires)
3. Vehicle load and load distribution
4. Suspension if all else fails, but this is very unlikely to be a contributing factor to high speed wobble unless something is grossly out of whack.

Lack of stiffness in the front frame and forks is a huge issue, but not one that we owners can generally address in any meaningful way. A KLR is simply flexible and this is the nature of the beast.
 

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IME; my KLR's exhibited instability only when the suspension wasn't set up properly, once that was done they've both been rock stable......even with full knobbies at 22PSI or so....ridden in all condtions including high speed pavement for extended periods....even with the lack of stiffness in the frame and forks.

In the end, your troubleshooting order is almost identical to my "wobble post" ;-)

Tom and I both agree that the KLR's suspension setup is an important item when it comes to KLR instability; apparenly you and Paul think the tires play a bigger role than I believe they do.....though all of the above has a cumulative effect. At the end of the day, I reject the notion that the use of knobbies automatically means a KLR will be unstable; that doesn't mesh with my experience. As I said in a previous post, in this case, these particular knobbies, in the configuration they were installed, given the wear and extremely low tire pressures could have been a bigger contributing factor than tire selection normally would be.

Cheers,
Dave

ps. whatever that link was, I couldn't get it to work.
 

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Discussion Starter #13
Being as the bike was a 2015, the suspension was probably not near the contributing factor as could have been on 2014 and earlier models with substantially softer standard springs.

I would have liked to simply rotate his severely worn/scalloped Front D606 tire so as to have the tread contacting the roadway in the inverted vee direction '/\', or better yet to have installed the new Shinko E705 that I used to demonstrate the influence of the vee direction.

I do feel that severely LOW tire pressure was the largest contributing mechanical factor on this bike and the pile of cargo on the rear Amplified the issue.
 

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Being as the bike was a 2015, the suspension was probably not near the contributing factor as could have been on 2014 and earlier models with substantially softer standard springs.

I would have liked to simply rotate his severely worn/scalloped Front D606 tire so as to have the tread contacting the roadway in the inverted vee direction '/\', or better yet to have installed the new Shinko E705 that I used to demonstrate the influence of the vee direction.

I do feel that severely LOW tire pressure was the largest contributing mechanical factor on this bike and the pile of cargo on the rear Amplified the issue.
1) true; it goes Gen1 (soft and longer travel), Gen2 2008 - 2014.5 (still soft, shorter travel; Gen2 2014.5+ (stiffer and shorter travel)......the 80%/60% stiffness increase in springrate and damping can only help.

2) Yes, I would have tried to talk him into a tireswap and increased pressure as well.

3) Largest?.....maybe, maybe not but I certainly agree with the heavy rear load playing a big part due to weight distribution (and the associated affect on the suspension!) as well as aerodynamics. Obviously there were a number of issues with his tire choice, wear, direction and pressure as well. statistically the vast majority of instability complaints come from bikes heaviliy loaded with panniers, top boxes, etc.


Anyhow, at the end of the day we can quibble over what percent of the problem was related to;

- the tire type
- the tire brand/model
- the tire orientation
- the tire pressure
- the tire wear
- the load
- sag settings and other adjustments,
etc. etc.

....but I think we all would have looked at the bike and made similar suggestions.

cheers,

Dave
 

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I bought the cheapest 130/80/17 90/90/21 on eBay. I ride 70 mph on ruinsheng Chinese/Alibaba tires. 105 with shipping. Looks like the rear will last 2k.
 

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IME; my KLR's exhibited instability only when the suspension wasn't set up properly, once that was done they've both been rock stable......even with full knobbies at 22PSI or so....ridden in all condtions including high speed pavement for extended periods....even with the lack of stiffness in the frame and forks.

In the end, your troubleshooting order is almost identical to my "wobble post" ;-)

Tom and I both agree that the KLR's suspension setup is an important item when it comes to KLR instability; apparenly you and Paul think the tires play a bigger role than I believe they do.....though all of the above has a cumulative effect. At the end of the day, I reject the notion that the use of knobbies automatically means a KLR will be unstable; that doesn't mesh with my experience. As I said in a previous post, in this case, these particular knobbies, in the configuration they were installed, given the wear and extremely low tire pressures could have been a bigger contributing factor than tire selection normally would be.

Cheers,
Dave

ps. whatever that link was, I couldn't get it to work.
It doesn’t work for me now either. Apparently, it is a temporary link and it has expired. It was a link to a PDF study done on motorcycle dynamics, specifically wobble and weave. They define wobble as originating in the front of the bike (front wheel bearings, tire, wheel, forks, steering stem bearings, and front of frame) and weave as originating in the rear (rear wheel bearing, rear tire flex, rear wheel, swing arm flex, swing arm bearings, rear frame flex). Wobble is usually higher frequency (I think they said 4-10 Hz or basically tank slapper style motion) and weave was lower (1-3 Hz).

The showed through both analysis and testing that the dominant issue is flexibility/slop in the aforementioned components that allow conditions to exist where the damping due to friction is overcome by the resonance. Suspension spring rates and damping were not factors. Suspension setup is only a factor to the extent it affects geometry (rake and trail), but was not a factor otherwise.
 

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probably picking nits now but;

- proper sag setting is a big part of what I was talking about when I speak of having the suspension set up properly. Ultimately sag and loading affects geometry which is at the root of the issue.

- like all the other conditions that allow the wobble to occur or get worse, I believe that inadequate damping exacerbates the problem by failing to help reduce the severity at the very least.


Soooo, we agree that geometry (rake and trail) are root issues and we know that suspension setup (sag in particular) affects the geometry. You think damping makes no difference while I believe it's a factor in the severity (if not the onset) of "death wobble/tank slappers".

I'm OK with that


Dave
 

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Hello Guys

I will add my little bit to this thread;
I always keep my tyre pressure at the maximum pressure recommended by Kawasaki. That is 21 psi on the front and 28 psi in the rear. I have never experienced any bad bike behavior at highway speeds.

That is my experience...

Thanks Guys

Matthew
 

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Discussion Starter #20
Hello Guys

I will add my little bit to this thread;
I always keep my tyre pressure at the maximum pressure recommended by Kawasaki. That is 21 psi on the front and 28 psi in the rear. I have never experienced any bad bike behavior at highway speeds.

That is my experience...

Thanks Guys

Matthew
Matthew,
I recon one can use what ever works for them. But I will always urge people to run 2 psi higher in the skinny front tire with even a solo rider. Or same pressures if heavily loaded like this guy was.

If one would attempt to count the difference in square inches of road contact between the skinny front & the fatter rear and using 2 scales, measure the load on each tire, one might see the reasoning.
Then consider how much more loading is placed on the skinny front tire during proper braking, ie 70% front / 30% rear. That puts about 70% of the entire bike / rider / cargo weight onto the front tire during braking, which can severely scallop most front tires if running low end of tire pressures.

Now add down-hill and heavy braking, how much more loading does that place on an under-inflated skinny front tire?
The more the tire flexes the warmer the tire runs & the faster the tread wears.
Too much heat from too much flexing is what causes actual blow-outs of tires, not too much pressure. The cording & rubber gets weaker from extreme excess heat.
 
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