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 Highway instability from luggage?

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Thrifty2fifty




PostSubject: Highway instability from luggage?   Sat Apr 29, 2017 3:41 pm

Just picked up a beauty of a wr last weekend, and have been equipping it with lots of goodies to make it adventure capable. However my side luggage is causing a weaving/wobble at speeds of 70 plus while attached. One thing that does help is if I scoot as far back on the seat i can the wobble calms down some. So I am thinking that the luggage is somehow providing lift on the highway?

Has anyone else encountered an issue similar to this before? I have balanced both tires and the luggage isn't big at all... any advice would help

Possible make them more aerodynamic somehow?

Here's some quick pictures i took of my bike with my glorious tool boxes for panniers =)



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johnkol




PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 3:14 am

A few questions first:

  1. Have the forks been raised?
  2. What tire pressures are you running?
  3. What tires are these?

The fact that the instability goes away when you sit further back indicates that increasing caster angle has an effect, so this looks more like a geometry problem than aerodynamics.
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Thrifty2fifty




PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 5:19 am

Initially the forks had been stock height, although i did lower them a little bit to see if it helped which resulted in no noticeable change. 
As for tire pressures I'm currently running about 25 psi front and rear. The rear tire is a kenda k270, and the front is a pirelli mt21. 

The reason I suspect aerodynamics is because without the boxes on its as stable as one could expect for a 250 dual sport. However once I put the boxes on weighted or empty (they are very light) It starts weaving at speeds of 65 plus. 

My thoughts so far is that I may have them mounted at too much of an angle and they could be providing just enough lift to the rear tire to cause these problems. shifting my weight to the back may help counteract the lift i'm experiencing? 

I would hate to have to drill new holes and remount them, but I may have too.
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Von551




PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 8:46 am

Check your sag fully loaded. Should be 4 inches. Then lessen your fork compression and stiffen your fork rebound to increase stability as well as lower your fork tubes as much as possible. Try lowering your tire pressure to 15 or 20 psi. Learn about what causes speed wobbles from a chassis/suspension point of view and that'll help. Sounds like it might be all related to your suspension. Lastly, consider getting some more 50/50 tires for more stability.
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dicklane625

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PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 12:01 pm

My two cents.... If you haven't yet, check to make sure your steering stem and all swing arm/linkage bearings are tight. Maybe try droppin the rear on the stock adjustment.
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Jens Eskildsen




PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 2:07 pm

Adjust sag with the added luggage, you need to add more preload to the shock.
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dicklane625

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PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 2:38 pm

Jens Eskildsen wrote:
Adjust sag with the added luggage, you need to add more preload to the shock.

This was suggested already, not quite worded like that... I was wondering though how you would do this properly? The luggage weight would be included in bike weight, correct? So you'd want to use that as bike sag and not rider/race sag... From what I've read the bike should sag so much under its own weight and more with rider weight. Let's really confuse him heh... horse
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Thrifty2fifty




PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 7:08 pm

Von551 wrote:
Check your sag fully loaded. Should be 4 inches. Then lessen your fork compression and stiffen your fork rebound to increase stability as well as lower your fork tubes as much as possible. Try lowering your tire pressure to 15 or 20 psi. Learn about what causes speed wobbles from a chassis/suspension point of view and that'll help. Sounds like it might be all related to your suspension. Lastly, consider getting some more 50/50 tires for more stability.
well with my HDB handguard setup I can lower my front forks ALOT as the handlebars are lifted up even more, so I am a little hesitant to drop it all the way that would be like close to 2 inches an estimate. 

dicklane625 wrote:
My two cents.... If you haven't yet, check to make sure your steering stem and all swing arm/linkage bearings are tight. Maybe try droppin the rear on the stock adjustment.
I haven't, but I will check the torque on it. Although Its an 08 with a mere 2300 miles on it when I bought it so Its spent most its time in someones garage. 

dicklane625 wrote:
Jens Eskildsen wrote:
Adjust sag with the added luggage, you need to add more preload to the shock.

This was suggested already, not quite worded like that... I was wondering though how you would do this properly? The luggage weight would be included in bike weight, correct? So you'd want to use that as bike sag and not rider/race sag...  From what I've read the bike should sag so much under its own weight and more with rider weight. Let's really confuse him heh... horse
see that is difficult because luggage weight will not remain constant at all, some days I have it on with just tools and mostly empty. I suppose I will pack them full of typical stuff I would bring for a small adv ride and the set the sag according to that. But that makes me wonder once I get to a campsite and download my luggage would that make the bike suspension more stiff than with nothing on it?
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Thrifty2fifty




PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 7:11 pm

Von551 wrote:
Check your sag fully loaded. Should be 4 inches. Then lessen your fork compression and stiffen your fork rebound to increase stability as well as lower your fork tubes as much as possible. Try lowering your tire pressure to 15 or 20 psi. Learn about what causes speed wobbles from a chassis/suspension point of view and that'll help. Sounds like it might be all related to your suspension. Lastly, consider getting some more 50/50 tires for more stability.

I absolutely will be getting some 50/50 tires in the future. But I have broken the bank quite a bit as it is with my bike. I still have a cee bailey windshield and a headlight guard otw as of now.
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Thrifty2fifty




PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 7:21 pm

Also on the note of looking into what can cause instability/weaving/wobbling at high speed I have found a very interesting article and if any of you guys havent checked it out its worth a read. The problem is that there are ENTIRELY too many factors that can cause weaving. 

Most notably in this article is a really old school video explaining weaving and all of the time they fixed it by leaning forward completely. Whats odd is that when I attempted this I had no noticeable improvement in wobble. Well I guess I cant post a link until 7 days has passed  dunno
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Von551




PostSubject: Re: Highway instability from luggage?   Sun Apr 30, 2017 11:24 pm

So you're saying that your fork tubes caps are two inches above your top triple clamp? If that's the case, that's your main problem! Raising them like that is great for turning, but terrible for stability. Making your forks flush with top of triple clamps will maximize stability. I'd measure your Race Sag with you and all your gear and luggage fully loaded and then with just you with all your riding gear. I'd guess if you set it to about 4" fully loaded it might be 3.5" with just you, making it a little stiffer. Or set it to 4" with just you and then it'll be a little softer and lower in the rear fully loaded, increasing stability. There's good YouTube videos on how to measure your race sag. Also, if your steering bearings are bad or it's too loose you can tell by raising front tire off the ground and then turning the bars and seeing if you feel any unevenness (bad bearings) or push bars from center and they shouldn't fall either way easily, if they do, your steering stem is too loose. Also, if you pull your front wheel towards you and side to side while it's in the air and you feel play, your steering bearings are bad, which this bike is known for.
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dicklane625

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PostSubject: Re: Highway instability from luggage?   Mon May 01, 2017 4:08 pm

Von551 wrote:
..... Also, if your steering bearings are bad or it's too loose you can tell by raising front tire off the ground and then turning the bars and seeing if you feel any unevenness (bad bearings) or push bars from center and they shouldn't fall either way easily, if they do, your steering stem is too loose. Also, if you pull your front wheel towards you and side to side while it's in the air and you feel play, your steering bearings are bad, which this bike is known for.

That is what I meant by checking them. thumb
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dicklane625

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PostSubject: Re: Highway instability from luggage?   Mon May 01, 2017 4:12 pm

Same thing with the swing arm assembly... Raise it and check for unwanted movement. I guess this goes for axle bearings front and rear too. It's not really mileage specific, but how it was ridden and taken care of for those miles. 1000 miles of muddy wet crap with no lube or maint. over several years and you could very well have sloppy bearings somewhere...
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johnkol




PostSubject: Re: Highway instability from luggage?   Mon May 01, 2017 6:13 pm

Thrifty2fifty wrote:
The reason I suspect aerodynamics is because without the boxes on its as stable as one could expect for a 250 dual sport. However once I put the boxes on weighted or empty (they are very light) It starts weaving at speeds of 65 plus. 

Then this clearly points to your instability being an aerodynamic effect, which improves with geometry changes (sitting further back increases caster angle).

I would suggest you bring your forks back to their original position (flush with the triple clamps), since this will maximise the caster angle. In the same vein, do not stiffen the rear suspension too much (4" race sag is a good goal) because then you are effectively decreasing the caster angle.

I also think that 25 PSI in front is too much, especially for a MT21. Try lowering the pressure to 18 PSI and see what the effect is.
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Thrifty2fifty




PostSubject: Re: Highway instability from luggage?   Mon May 01, 2017 9:20 pm

Von551 wrote:
So you're saying that your fork tubes caps are two inches above  your top triple clamp? If that's the case, that's your main problem! Raising them like that is great for turning, but terrible for stability. Making your forks flush with top of triple clamps will maximize stability. I'd measure your Race Sag with you and all your gear and luggage fully loaded and then with just you with all your riding gear. I'd guess if you set it to about 4" fully loaded it might be 3.5" with just you, making it a little stiffer. Or set it to 4" with just you and then it'll be a little softer and lower in the rear fully loaded, increasing stability. There's good YouTube videos on how to measure your race sag. Also, if your steering bearings are bad or it's too loose you can tell by raising front tire off the ground and then turning the bars and seeing if you feel any unevenness (bad bearings) or push bars from center and they shouldn't fall either way easily, if they do, your steering stem is too loose. Also, if you pull your front wheel towards you and side to side while it's in the air and you feel play, your steering bearings are bad, which this bike is known for.

No my forks tubes are only about 1\4 inch above the clamps. But I will be putting them back to stock height tomorrow. And I actually have checked all bearings for play correctly to make sure they aren't worn out or anything. Although I should probably pack them with grease it being a 08. 

johnkol wrote:
Thrifty2fifty wrote:
The reason I suspect aerodynamics is because without the boxes on its as stable as one could expect for a 250 dual sport. However once I put the boxes on weighted or empty (they are very light) It starts weaving at speeds of 65 plus. 

Then this clearly points to your instability being an aerodynamic effect, which improves with geometry changes (sitting further back increases caster angle).

I would suggest you bring your forks back to their original position (flush with the triple clamps), since this will maximise the caster angle. In the same vein, do not stiffen the rear suspension too much (4" race sag is a good goal) because then you are effectively decreasing the caster angle.

I also think that 25 PSI in front is too much, especially for a MT21. Try lowering the pressure to 18 PSI and see what the effect is.

Okay I will try lowering the psi to 18 for the MT21, and will be raising forks to max height again. On an interesting note I found a contributor to my high speed weave, I believe its the HDB Handguards in general. Although I know for a fact that the mirrors once folded out so I can use them instantly reduce my stability, I would assume this extends to the entire handguard plastic it's self. 

Tomorrow I'm going to remove the plastic off the hand guards and use stock mirror's and see if that fixes it. 

My thoughts is that although my luggage being attached causes the instability, The root of the cause is these hand guards at high speeds. That along with the fact that I have a Cee Baileys Windshield coming in the next few days are giving me high hopes I wont have to drill more holes and remount my luggage boxes. 

If you don't know about the HDB Handguards these are the ones I have that are definitely contributing to my highway weave. 

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johnkol




PostSubject: Re: Highway instability from luggage?   Tue May 02, 2017 2:09 am

Thrifty2fifty wrote:
On an interesting note I found a contributor to my high speed weave, I believe its the HDB Handguards in general.

The HDB handguards are very popular with the WRR crowd, and I have never seen a comment about the handguards adding any instability to the bike, with or without the mirrors.

Having said that, it would be instructive if you were to remove the handguards, keep the cases on, and see what the effect is.

And remember, only one change at a time in order to isolate the problem.
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Von551




PostSubject: Re: Highway instability from luggage?   Tue May 02, 2017 3:51 am

Ditto johnkol, my buddy has hdb guards on his wr and no issues. I have Barkbusters Storm on mine, no issues. Instability is always with tires, chassis and/or suspension.
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Thrifty2fifty




PostSubject: Re: Highway instability from luggage?   Tue May 02, 2017 10:58 am

johnkol wrote:
Thrifty2fifty wrote:
On an interesting note I found a contributor to my high speed weave, I believe its the HDB Handguards in general.

The HDB handguards are very popular with the WRR crowd, and I have never seen a comment about the handguards adding any instability to the bike, with or without the mirrors.

Having said that, it would be instructive if you were to remove the handguards, keep the cases on, and see what the effect is.

And remember, only one change at a time in order to isolate the problem.


Von551 wrote:
Ditto johnkol, my buddy has hdb guards on his wr and no issues. I have Barkbusters Storm on mine, no issues. Instability is always with tires, chassis and/or suspension.

That's interesting. It's most likely a combination of the tires\luggage with the hdb's adding onto it. I believe you guys when you say you have never heard of them causing this problem, but I can tell you for a fact I was riding down the highway while still weaving I folded my mirrors in and the weave instantly almost went away.

An article I was reading on bmwmotorcycletech about weaving said he did a bunch of testing and the majority of weaving on most motorcycle's he experienced had saddlebags, or fairings directly attached to the handlebars. Flat spots in the rear tire also was a big contributor if you don't turn enough.

Either way I wish I wish I had a camera I could record it with. Ill take the plastics off and try it again today and let you guys know if it went away

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Thrifty2fifty




PostSubject: Re: Highway instability from luggage?   Tue May 02, 2017 11:03 am

This is taken from the article on "bmwmotorcycletech motorcycle tank slappers, weaving, wobbling, instabilities" I can't post the link to it but if you google search that it will pop right up.

"Bikes with larger diameter fork tubes tend to be more stable. That is because they are stiffer, and any small bending from road irregularities is minimized, and does not easily go into a looping oscillatory mode. That is, bending, however slight, does not get very oscillatory.
So, while the bearings need to be adjusted correctly, & shocks & springs, ETC., not worn out....what else can be a problem?...:

1. Saddlebags, rear tour trunks (scoot boots), large fairings.

2. Every additional pound in the saddle bags will lower the speed at which fun stuff begins....even fairly small weight increases. Yes, this conflicts with the information about RIDER weight, which is opposite, and helps.

3. Weight in tour trunks is especially vicious in its effects. Just HAVING a backrest or tour trunk (even empty!) can greatly influence tendencies towards instabilities.

4. TRY REMOVING handlebar weights if you have installed them. They might reduce vibration, but INcrease potential instability. Do this only experimentally, as there ARE some bikes that were designed to have them in the first place, & in SOME instances they do help; but usually with vibration, not stability.

5. Handlebar or front fork mounted fairings, especially large ones (tiny fly screens are vastly less of a problem) can be a HUGE problem. Such fork-mounted windshields & fairings were THE big problem with the short wheelbase /5 bikes; and, when, worse yet, you coupled with a squared off rear tire, & maybe a trunk or whatever on a rear rack, and saddlebags, you are surely asking for serious problems. You COULD have a diverging high speed wobble. The biggest problems are handlebar/fork mounted fairings, heavy bags, and having a big backrest or touring trunk, and squared off rear tire.

6. What was the biggest bad effect, if one was careful to have one's suspension in reasonably good condition, bearings adjusted reasonably well, and not excessive aft weight ????.....

You may be surprised to find out that a well-worn, flatted area rear tire was a HUGE cause for instability.....and high speed scary results are possible. Yes, even in just about a straight line, or slow curves. This was exactly what Gordon Jennings found out....and I duplicated his testing and I TOTALLY AGREE. I can take this a bit further, perhaps you won't like this interpretation! If you tend to make very mild turns, and ride straighter roads a lot, that rear tire will square off...guess what happens then, in, for example, a downhill sweeper at medium to higher speed?? Guess what happens in an uphill hot-dogging and curved top hill?"
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johnkol




PostSubject: Re: Highway instability from luggage?   Tue May 02, 2017 7:55 pm

Thrifty2fifty wrote:
This is taken from the article on "bmwmotorcycletech motorcycle tank slappers, weaving, wobbling, instabilities" I can't post the link to it but if you google search that it will pop right up.

This article does not mention handguards as sources of instability.

Incidentally, I disagree with their claim that a squared-off tyre leads to instability; I've taken my CBR with a squared-off rear tyre to numerous trackdays (speeds of 140 mph) and there was barely any difference compared to a new tyre.

Having said that, a mis-cast tyre could lead to instability, but that kind of instability is detectable at all speeds, and does not go away when one removes the luggage from the bike.
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dicklane625

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PostSubject: Re: Highway instability from luggage?   Wed May 03, 2017 12:25 pm

Given what's been said, seems to me like the course of action should be... Set proper race sag. Raise the triple tree back up on the forks, possibly lower the rear in the stock adjustment. Seems that would change the castor angle mentioned the most... And if neither works try to make the cases more aerodynamic. I agree the squared tire shouldn't matter. It didn't for me on the stock deathwing or d606s I've ran down. N I maxed my r2 out at roughly 104mph on the stock tire worn down 1/2 way... I had to do it at least once... I don't recall the op saying his tire was worn so this seems irrelevant to his issue even if it did cause death wobble... Better yet just get tanked before you ride... You won't know if it's you or the bike wobbling. dutch Note I do not actually suggest doing this... :nono:
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dicklane625

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PostSubject: Re: Highway instability from luggage?   Wed May 03, 2017 12:28 pm

Oh n most bikes don't use handgaurds so they wouldn't really be suggested... What is suggested is large fairings, other sources of wind catchers. The book I have mentions this too. The bike reacts differently when they are attached to the forks by some means... Besides for crosswinds and gusts it shouldn't cause wobble tho according to it....
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