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Bad steering wobble at 70mph and above

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I did a lot of mods to my DRZ400s all at once. A couple of those mods were putting Dunlop D606's on front and rear and adding a Bajaworx windshield. Now when I hit right at 70mph the handle bars start to shimmy back and forth and increases the faster I go (very scary). Never did that before so I am in the process of trying to see what is causing it. Its either the windshield causing it from it either being a little off center (I measured it several times so I don't think it is that) or it is just a characteristic of that windshield or when mounting my front wheel I guess I could have got something out of alignment or it may be just a characteristic of that D606 tire.

First I am going to remove the windshield and give it a test run. I had seen a video on the bajaworx windshield of this same complaint and the fix was to put spacers between the windshield and the front cowl. But I have also seen the same complaint about the D606. I am running about 23 PSI in the front tire.

Thoughts? Comments?

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It is your tires. They are an offroad, knobby... I run them. They are loud and vibrate on the street. My wobbles happen around 80 mph

 

 

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Oh wow I do not like that. Guess after I test it without the windshield and if it still does it, I will be going to more of a street tire on the front. Plan on doing some road trips and will be on the highway a lot to get where I am going.

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There are a lot of tires that are more street friendly. I want to get a more street friendly tire soon, as I have put 500 miles on my mine already, all street.

I have heard their lifespan isn't very long.

 

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Well, it may or may not be the D606. However, I've run mine to about 1/2 life now and they have never wobbled, not even the slightest, not at any speed. And I've also run them off-road including high speed, with a torn tube, for at least 40 km with zero issue.

I would suggest windshield removal as a first step.

Edited by shuswap1
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I could check, but I use the thumb gauge and I would guess less than 18#

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I really appreciate the flat-run ability, saved my butt and allows me to run lower pressure when far from help. Wish the back end was as helpful, a flat there requires repair before running another 100'

Edited by shuswap1
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I'm sympathetic to wobble issues, trying to sort a nasty wobble on the wife's seriously-lowered EXC-F 350 that begins at about 60mph and worsens the faster you go.

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So, I have doubts its the tire, but you never know without some tests. Is the suspension stock? Normal sag?

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just for added info, when i put sm rims on my S and was moving faster on a regular basis on the street i noticed alot of shimmy from the front end simply from the S fender .. i put a factory sm fender on and it helped alot, 'factory' being the key word - the sm fender covers pretty good, i wouldnt recommend one of those weeny little aftermarket ones if your going offroad, even on, they'll allow alot of crap to flip in your face and all over your bike ..

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11 minutes ago, cowpie said:

just for added info, when i put sm rims on my S and was moving faster on a regular basis on the street i noticed alot of shimmy from the front end simply from the S fender .. i put a factory sm fender on and it helped alot, 'factory' being the key word - the sm fender covers pretty good, i wouldnt recommend one of those weeny little aftermarket ones if your going offroad, even on, they'll allow alot of crap to flip in your face and all over your bike ..

...as in cowpies?

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Well I removed the windshield and took it up to 80 mph with no issues! It was steady as a rock! I did notice that if you sit a little too far back on the seat it lightens the front too much and you get a little shake but still nothing compared to what I was getting.

I will be trying the spacers under the windshield next to see if that fixes it.

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Look to the angle the shield is mounted on as well, if the spacers don't sort the issue

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It's probably more than one thing causing it the most . With different tires you may not have any issues with the windshield as it is , street tire grip better holding straight but knobbies don't . You probably need to find what angle stabilizes the frontend , may even need to raise or lower the forks on the triples some . I put a set of Kenda Big Blocks on my TE510 and I couldn't go 65mph with them , but with the other knobbies it never had a hint of wobble . Those same tires didn't cause any wobbles on my KLX though . It comes down to tuning the bike to the setup . You don't want it to be right on the edge of wobbling , even if it isn't doing it at the moment , all it takes is to be hit by a crosswind or whatever when going fast and it'll bite you.

I had a '91 DR650 that got "loose" at 85-90mph but it was manageable , one day sort of racing a buddy I was going 86-88mph and came past a length of woods to where a big hayfield was and hit a crosswind following the woodline , and it instantly went into a tankslapper . I left 3 long "U" shaped black marks on the blacktop and have no idea how I held on . Between slowing down and the crosswinnd slowing because I got past the woods edge it suddenly went smooth. I really, really, pay attention to how easy any of my bike feel like they want to wobble at whatever speed and do whatever I can to give some extra leeway , usually changing tires or suspension setup. I also can't hardly ever get myself to got above 80mph on any of my DS bikes with knobbies anymore .

 

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Edited by jjktmrider
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bead locks ? tires balanced ?

 

no doubt knobs on the street are less friendly than trailwings, ive had a bunch of different knobs on my bike w out issues like you describe, but i balnce them and run around 18-20psi fr 14-16 rear

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Mefo Explorer tires. Run my kLX250 off road a lot but mostly forest roads and Jeep trails. Not quite a dirt tire off road but very good. Excellent on the street as well even in twisties in the rain. 90 mph no problems.

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