2015 KLR650, Tourist down at 70 mph from speed Wobble! - Page 2 - Kawasaki KLR 650 Forum
KLR & Other Motorcycle Related Discussion Grab a seat and discuss whatever you like about the KLR or other related topics. Within reason.

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post #11 of 22 Old 06-26-2019, 10:44 AM
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Originally Posted by DPelletier View Post
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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Lots of things come into play, but I believe, as apparently does pdwestman, that tire pressure is a key factor and everything Iíve 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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post #12 of 22 Old 06-26-2019, 11:20 AM
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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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post #13 of 22 Old 06-26-2019, 12:29 PM Thread Starter
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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.

pdwestman
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post #14 of 22 Old 06-26-2019, 01:57 PM
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Quote:
Originally Posted by pdwestman View Post
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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post #15 of 22 Old 06-26-2019, 05:31 PM
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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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post #16 of 22 Old 06-27-2019, 07:23 AM
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Quote:
Originally Posted by DPelletier View Post
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 doesnít 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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post #17 of 22 Old 06-27-2019, 10:35 AM
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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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post #18 of 22 Old 06-27-2019, 08:48 PM
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This thread made me so paranoid that I went and aired up my tires.
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post #19 of 22 Old 06-28-2019, 02:32 AM
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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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post #20 of 22 Old 06-28-2019, 10:03 AM Thread Starter
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Quote:
Originally Posted by timberfoot View Post
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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