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What causes high speed wobble?

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Hello all,

Prior to changing out my tires from deathwings to knobbies, I had shortened the spring height by turning the adjuster, I had also reset the rear shock to 1 click from being full hard, and had changed the top settings on the front forks to one click from being full hard on the top adjuster. I could ride at 70 - 75 without any high speed wobble, but I was still bottoming out on jumps from time to time. So in the process of putting mt 18's on the front and terra flex on the rear, I also adjusted the bottom setting on the front shocks to 1 click from full hard.

Now when I get the bike going 70 to 75 on the interstate, I get high speed wobble from time to time. Sometimes it seems as I am getting dirty air from trucks, or cars in front of me, and other times I have clean air.

Is going to knobbies the problem, or is the setting of the bottom shock screw to one click from full hard the problem, or is something else going on that I do not yet understand.

Thanks in advance,

Bill

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Knobbies are certainly part of the wobbles you're getting. Just look at them compared to 50/50s.

Imbalance in your suspension also contributes to wobbles. Since suspension setup is almost an art, I'm a big believer in finding a suspension pro you trust and having him setup up the bike for your weight, riding ability, and terrain. Real suspension tuning involves more than just spring rates. Valving and springs are designed to work together, so re-valving is a must in my opinion. Then there's balancing the bike front to rear and getting the sag right.

But even with the perfect suspension, you're going to get the wobbles with knobbies, whether it's offroad in the sand at 55 mph or on the highway at 75. At that point, a steering stabilizer might be what you want.

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William1,

I didn't have high speed wobble issues until I changed to knobbies and did the final setting to 1 click hard on the bottom of the front shocks.

Which one is causing the high speed wobble, changing to knobbies, or hardening the bottom settings on the front forks to one click from full hard?

Or is it something else? With all the other setting adjustments, and still riding deathwings, I had no high speed wobble.

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I suppose it is matter of what you consider high speed. High speed on my DRZ is over 85. Knobbies typically cause vibrations, unless they are extremely agressive ones (big knobs, big gaps between knobs). Another thing you did not mention is wheel balance.

The easiest thing to do would be to return the suspension settings back to where they were before the wobbles. Better or worse?

What tire pressures did you run with the Deathwings? What tire pressures are you running now?

There are so many variables, no one can catagorically state exactly what is causing the problem. Start with the cheapest and quickest fix. Make sure you keep notes on each change. Also, do one change, then test.

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steeper rake, after i put an RM triple on my DRZ-SM it wobbles and shakes at speeds above 90mph. little sketchy but i just lean forward and hang on......

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Usually the biggest issue for any wobble on the front is the sail front fender. Which fits per your dirty air statement.

Second is that knobbies are inherently less stable than the more moderate tire.

So adding the knobby to the original issue it is more noticeable. The suspension likely contributes, but I would bet less than the former 2 issues.

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My bike has balancing weights on the spokes. Still have the DeathWings on. did you rebalance after installing your new tires? The compromised road-worthiness of knobbies will have an impact, but an out-of-balance situation would have the biggest impact on high-speed wobble.

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I had an XR650 on the street for a while, and ran dirt-only tires occasionally when I was too lazy to switch them back.

The big issue with true dirt-only knobbies and wobble is the design of the knobs themselves. If they are widely spaced and alternate, that's a major recipe for straight-line wobble as it feeds slight de-stabilizing off-center loads continuously. However, that design will do slightly better in turns.

If you have a central row of knobs, it'll run straight on the road, but when you lean over to turn, it's a squirming, wobbly nightmare.

Also, dirt-only tires wear out hella-fast on the street. You're throwing money away when you do it.

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Regarding the balancing question - After the tires were installed by the dealer, and I went to pick up the bike, I noticed that the lead weights that were on the spoke from the previous deathwings were gone, and no new weights to balance the tires. I asked the dealer if they balanced the tires. He indicated that with the knobby tires, they had put them on the balancer and discovered that they were too far from being balanced that it would require more lead than they were comfortable putting on the spokes to balance either tire. They also said that that was common on knobby tires, that the tires are too far from spec to be propperly balanced.

Since this is my first experience in changing the tires, I do not know any better. Is the explanation he gave correct, or was he trying to get out of work he should have done? Do most mechanics balance knobby tires?

Thanks,

Bill

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Well, that is most likely the culprit. As speeds increase, so do the effects of unbalanced tires.

Most do not balance knobbies as soon as you go in the mud, the wheels are out of balance so what is the point. What you should do is find the heavy point. That should go opposite of your rim lock. Then try a regular balance again and see where you are.

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Slight suspension damping changes won't be making the front wobble at speed, it'll be the knobbies but while that's probably where the wobble's being generated you can minimise the effect it has. Don't expect the knobbies to ever feel as "planted" as dual-sport tyres on the road, soft terain knobbies in particular squirm noticably even at low speed, at high speed they can get into a sort of harmonic cycle. It's normal to feel that but if a bad wobble develops you can tune it out. First big thing is to check rider (or "race") sag, if the back end's riding higher than it should then your forks are raked in too much (too steep) which makes for more steering feedback. It'll feel light to turn and you may feel it wanting to steer into a corner too much. Same thing if the fork sag is too much and both will also cause high speed steering instability. Check sag at both ends is roughly right (not saying what mine is, it's not a typical setup). If it's OK you can still lower the forks in the tripple clamps say 5mm and try that. 5mm is a big change here but it'll help get a feel for what the adjustment does, the steering will feel slightly heavier but more stable, if you go too far then too much rake will start to make the front want to wash out.

Someone mentioned the front fender, you didn't make any changes there but that can cause a similar effect. Fitting a couple of washers under either front or rear mounting bolts to change the fender angle slightly usually cures it.

Luck dude, let's know how it works out.

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My wobble WAS cured by suspension adjustments...

I guess it could depend upon the weight of the rider...

I'm right at 190 with stock springs on an 01 "S" model...

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My wobble WAS cured by suspension adjustments...

I guess it could depend upon the weight of the rider...

I'm right at 190 with stock springs on an 01 "S" model...

Peace dude, adjusting suspension was what I was suggesting. I just didn't think slight damping adjustments were likely to be the cause, or the cure. Some knobbies are scary as on the road if you're not used to them and rake/trail is probably going to have the biggest affect on moderating speed wobble.

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Trailtiger issues started AFTER he put on knobbies and AFTER he cranked up the damping. He needs to return the damping to where it was and retest. He also stated the shop that mounted his tires said the balance was so far off that were not going to put that much weight on the wheel so it is a given the wheels are terribly off balance.

So... this issues need to be addressed prior to trying other things.

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William1,

Where can I buy tire locks for the tires, and how hard are they to install? When I asked the dealer - who put on the new tires to install wheel locks, he said they don't do that, that they would service existing wheel locks, but they wouldn't install them. So where do I get them, and how hard is it to install. I understand that there are already 2 holes in each rim on the 2007 s to receive them.

Also, I do not have the equipment to remove the tire and replace them to the rims. The dealer charged me 120 dollars for labor to install both tires, no that price did not include the tires or the tubes. To get the heavy side of each tire to the opposite side of the new wheel locks, can I deflate each tire, put some soap on the rim edge, and slide the tire around the rim? If not, I don't know how to get the heavy tire side opposite the wheel lock.

Also, Can you install a wheel lock without removing the tire? Again, I do not have the know how or tools to remove the tires and put them back on. I understand the terraflex tire I am running on the rear is a real pain in the a$$ to get on and off.

Finally, are the soft to hard screw adjusters on the bottom of the front forks the dapening adjustment? If so, can you or anyone tell me how many clicks from soft or hard they should be from factory? I didn't record where they were.

Thanks,

Bill

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Rim locks are available in any motorocycle parts catalog, take a browse of parts unlimitered here at the TT store. You will only want one, unless you run super low tire pressures.

$120 to change two tires is cause for prosecution! Worse price I have ever seen is $70 for two and that includes balancing. You need to find another dealer.

To install a rim lock, you need to pull the bead on one side off of the rim to slip the lock inside. It is very easy to make a mistake and then you will need a new tube. They are like doing a bicycle only 10 times more difficult.

Lesson learned. Before ever making and adjustments, you need to make a note of where they are now. With suspension, it is a matter of turning the adjuster to full soft, counting the turns/clicks as you go. Write that number down. Then return to the original setting and move the desireed direction, make note of how far/clicks you moved it.

I would need to know what year your bike is. Is it a 'S' or a plated 'E'? I would be happy to look up OEM settings, but then it is better to start out too soft and stiffen Vs. starting out too stiff and going softer.

Miost likely, the upper adjustment (preload) sould be set at the 3rd groove from the top and the screw under the fork is set at 7 clicks out from closed.

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William1,

Thanks for all your help.

The bike is a 2007 s model. I think the letters near the setting screws go from s to h, so is closed the same as h?

Yes, please provide me with the clicks to use to get back to original from s over.

By the way, the reason all of my settings are currently set as far from s as possible is because I kept bottoming out the shocks, front and back when jumping. I asked a few questions about it in october or november. Two of the reasons I keep bottoming out is I weigh 175 without gear, and I am so short that I installed Kouba DRZ3 links and a gel seat and added a bar spacer and slid the shocks up about an inch in the holder beneath the handle bar to be able to get a toe on the ground. I know it is not the right way to lower a bike, but I do not have the cash yet to have the springs and shocks re-done to fit my height and weight. I have seen from some of the threads on here that that costs at least 500 dollars, and I can't come up with that much cash to spend on my bike.

I have three boys, the oldest -11- rides a kawasaki 2 stroke 60, and I am currently saving $ to buy my 7 year old a 4 stroke 50, so I need to skimp on any upgrades to the DRZ until my middle son has wheels.

Thanks in advance for the OEM settings. Please describe them as clicks away from the S on top and bottom of the shocks so I don't get confused.

Thanks again,

Bill

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DRZ3's will really mess you your suspension. No wonder it bottoms. Ok, I understand you cannot do anything about it at present. We'll do the best we can with what we have at hand.

One thing is you have lowered the rear by about 2-3/4" and the front only an inch. The reduces the amount of trail (angel the forks are from a vertical line). This has the effect of making the bike steer faster and also increases instability. You need to try to increse the amount you lowered the front. Bar risers are cheap and plentiful, then you can raise the bars, and raise the fork tubes.

An 07 S forks have 11.3" of travel. you can pull the tubes uop into the triple clamps till you have 11-3/4 space between the top of the tire and the bottom of the fender.

There is no preload setting.

The damping stock setup is:

Front

Compression:

Turn it clockwise to the full hard position, the counterclockwise 13 clicks out. So yes, closed/starting point is the same as H.

Rebound:

Turn it clockwise to the full hard position, the counterclockwise 16 clicks out.

You may also want to consider running a heavier fork oil, like a 7/7.5wt oil. Stock weight is a 5wt. It should be filled to 120mm (5.07"). This is 710ml (24.5 ounces) in each leg. This is also a cheap fix.

You also should check your headset (steering) adjustment to make sure it is properly.

Rear

Compression Low Speed 1 and 1/4 turns out

Compression High speed 10 clicks out

Rebound

13 clicks out.

You users manual will have pictures and a better explanation that I am providing.

If you have to run on the road, keep your tire pressures up.

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When I converted my XT to a motard I put a rimlock on the front wheel to match the rear, and had stability issues right from the get go...

...but once I balanced the front wheel with some slotted fishing weights to compensate for the rimlock, it was as steady as a rock on the freeway as fast the the little bike could go.:applause:

balancewheel1.jpg

Balancing is easy to do... Just remove the wheel, put it between some notched boards, and the heavy side always heads for the bottom. :lol:

Trimming the front fender also helps keep it from oscillating.

Greg

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