HELP: High Speed Wobble, Possible Supension Adjustment?

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HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Roo » Wed Apr 20, 2016 1:59 am

New to the forum, so a quick Hello to the group :)

Under acceleration at high speed (160km/hr or higher) I get a wobble in the superduke. The harder I accelerate the worse it is. But its not a quick jerking wobble, just a steady wobble that gets more intense the longer I accelerate/faster I go. Looking for some help to correct the problem.

To correct the problem, I have to stop accelerating, let the bike settle itself, then accelerate again. Sometimes the bike will regroup quickly, sometimes I have to dropped the speed a lot. Most times when I accelerate hard the issue just starts again.

Things that seem to help the problem are, 1) hold the bars tigher, but this only helps minimally

2)Tuck in and get most of the weight on the front end of the bike/over the tank.

I'm the original owner, bike bought new last year, issue was there right from day one. Suspension is set to the manual's "sport" settings.

Things I think could help/looking for feed back 1) Adjust the rear shock preload? I'm 6 foot 3 inches ,
200 pounds

2) buy a scotts steering dampener ? Maybe under hard acceleration the front end is so light that an unbalance starts and the stock dampener can't pick it up and stop the issue

3) poor tire pressure? I'm just running the stock #'s. What is everyone else running for street use?

Any help will be appreciated. Love the power and comfort of this bike, however I'm coming off driving supersports for years , and I've never felt this unstable at high speeds!

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by xaotikos » Wed Apr 20, 2016 8:17 am

I dont have the monster but SMT instead which is more prone to wobbling than sdr because of total height.
Usually, wobbling comes from an unloaded front during acceleration. You should first of all set the correct sag rear and front. I believe your rear height is low (needs more preload) or front height is high (needs less preload). You should check with sag measurement.

The tighter you hold the bars, the worst the wobbling will become eventually. Putting some weight at front should minimize the effect.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by JimmyElsewhere » Wed Apr 20, 2016 9:17 am

You might have already done these but I would check the following:
The rear hub for bearing play and whole assembly,
the Swingarm pivot bearing for play,
Steering head bearing for play.
Probably engine mounts as well.
Maybe try a new set of tires too. Personally I don;t like the OEM's much and will be upgrading soon.

A steering damper won't fix the problem but might help avoid a tank slapper. I upgraded the stock unit to 25 weight oil which is a cheap fix for the factory unit.

I'm taller than you but about the same weight, but I'm still not happy with my suspension setup. I have wound on a touch of preload in the rear to set the rider sag but I think the front needs stiffer springs as my cable tie shows the front is pushing too far through the stroke.



Cheers Jimmy

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Roo » Wed Apr 20, 2016 4:35 pm

20k bike and it needs a suspension upgrade :(? I agree, going to increase the preload on the rear shock and hopefully that can help. Unreal that there is no preload on the front shocks. Yearly service is do, so I will get them to check those bearings for play. But like I said, the bike has had this issue day one off the showroom floor.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by xaotikos » Wed Apr 20, 2016 7:46 pm

Spring change is not suspension upgrade is just correction for your weight. 200 is not too heavy though and i believe with changes on preload here and there

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by dflowers » Wed Apr 20, 2016 8:50 pm

I have not had any wobbles which includes some pretty high speeds at a track day, but the front does get this light feeling. I think part of it is that it has no fairings. Once I get my mupo fork cartridges installed I am going to really focus on getting the settings right.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by wsmc99 » Wed Apr 20, 2016 8:57 pm

My opinion and observations are as such:
200 lbs is on the edge of the design parameters for the springs.
Get your rear sag to 40mm and see if it helps.
The fork springs are probably sacked a bit, greater than 32mm of sag? That at the moment will work to keep weight on the front, but at the cost of full travel.
Try tire pressures at 35F/33R cold.
Steering dampers mask geometry issues, fix the geometry issue.
In real terms you'll need a 1000# spring for the rear vs. the stock 971# and probably just one 1.0 kg/mm fork spring. When that is set, raise the forks to 8mm above the triples.
I weigh 225-230# and have an 1100# rear spring and 1.0 springs in both forks. All sag numbers align and the bike works great. The rebound damping in the stacks will need to be fortified though.
*Death grip on the bars will only make a weave worse.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Roo » Wed Apr 20, 2016 9:08 pm

Tks for all the advice. Going to try and get some sag #'s with the help of a friend

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Gimlet » Wed Apr 20, 2016 11:27 pm

I have no such issues with mine. I did have terrible bar wagging problems with my SMT and no amount of suspension adjustment would dial it out. It was cured instantly and completely by changing the tyres.
Haven't heard of this problem before with the SDR but I'm convinced the OE Sportsmarts are not suited to this bike. There is a lack of feel at both ends and a strange sensation of wandering at the front on some surfaces. I've learned to trust the rear but its an act of faith. It never feels entirely trustworthy and its always slightly wooden.
The rear is on 1600 miles and already well on the way. I doubt it'll make 2500 miles then I'll be replacing with a set of Metzeler M7RRs.
I have the Metzelers on a 1098 Ducati and I run them at 35 psi rear and 33 psi front. I found running the Sportsmarts on the SDR at those pressures made things worse and added a harsher ride as well for some reason. I've pushed them back up to 35 front and 39 rear.

I'll be getting a pro suspension set-up on mine but I'm not altering anything till I've changed those tyres.

Maybe the OP's problem is a combination of wrong tyres and forks running at the limit of preload. Though a 200 pound rider doesn't strike me as excessive for standard fork springing on a bike like this.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Roo » Thu Apr 21, 2016 4:26 am

Will adjusting the bars to the forward position help any?

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by JimmyElsewhere » Thu Apr 21, 2016 10:29 am

Another thing to check, Triple trees are tightened to spec, and wsmc99's post reminded me that you should also check the fork height above the triple trees is even on both sides.
Also , a long shot here, and I'm not even sure whether this could be an issue with the SD but I've seen an incorrectly tightened front axle have some weird effects on dirt bikes. Maybe loosen off the pinch bolts on the front axle, give the bars a good bounces and re-tighten to spec. Like I said a long shot but who knows.

I'm also wondering is there any way at all the rear wheel could get out of alignment ? I'm not familiar with the rear hub assembly but I'd assume it's not possible unless there's an assembly fault/part failure however it might be worth doing a string-line alignment to check both wheels are true.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by wsmc99 » Thu Apr 21, 2016 2:34 pm

Roo wrote:Will adjusting the bars to the forward position help any?
Yes, it will weight the front end a bit more, but try the other steps first because of the lack of travel you may have with to light a spring.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Roo » Thu Apr 21, 2016 11:20 pm

I have a buddy lined up tomorrow to give me a hand setting the sag.

Been watching some youtube vids on how to check the sag, doesn't look too hard. Just need a extra hand

2 quick more questions.... Sorry, I hope i'm not getting annoying yet :o

What range do I want the rear sag to be? From what I see, I want the rear to be 30-35 mm? One person said 40mm in the rear though.

Also, I prob should check the front right? Even though I can't make an adjustment. My thoughts are I should have the front within about 5 mm more sag then the rear.

Really appreciating all the feed back. Going to check all the bearings out as best as I can while I'm at it.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by wsmc99 » Thu Apr 21, 2016 11:51 pm

Happy to share the knowledge.

Sag numbers are a function of travel.
On road bikes you want your dynamic sag (aka Rider Sag) to be about 25% of the total travel. This is bike unloaded to you in gear sitting on it with as much weight as you can put on it.

I calculate 40mm as 25% of travel, but the actual shock spec says 45mm. Somewhere in that range is fine.
Front should be approx 32mm of sag.

Definitely check both as it gives you an idea of the balance of your bike.
If you have 5 extra mm in the front of sag you might balance with that number less in the rear.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Silent singer » Fri Apr 22, 2016 5:32 am

Just to throw something else in the mix. I've just fitted Mupo cartridges but I'm running the recommended base settings for now until the tyres are scrubbed in.

My front preload is 32mm and the rear is 7mm (shock spring from unloaded). Changed both tyres for Metzeler Sportec M7 RR running 40/36 psi cold and there are 3 lines showing on the forks (clamped on the third so technically 2 lines). I also have the high speed wobble above 120mph. Haven't played with the compression/rebound settings yet. It's all a guesstimate until the tyres are scrubbed in and I can hopefully give some meaningful feedback to what is going on.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by wsmc99 » Fri Apr 22, 2016 8:28 pm

Silent singer wrote:Just to throw something else in the mix. I've just fitted Mupo cartridges but I'm running the recommended base settings for now until the tyres are scrubbed in.

My front preload is 32mm and the rear is 7mm (shock spring from unloaded). Changed both tyres for Metzeler Sportec M7 RR running 40/36 psi cold and there are 3 lines showing on the forks (clamped on the third so technically 2 lines). I also have the high speed wobble above 120mph. Haven't played with the compression/rebound settings yet. It's all a guesstimate until the tyres are scrubbed in and I can hopefully give some meaningful feedback to what is going on.
Way to high on the tire pressures!!!! 35F/33R cold.
Your front SAG(?) is 32mm I assume, what's the rear sag? that will be important.
That may be a bit steep in the front mine is 8mm above (5mm is stock I believe) which is about 2.5 lines showing. Sounds like you are about 10mm.
You are changing to many factors at once.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Silent singer » Fri Apr 22, 2016 9:14 pm

Can't remember rear sag off the top of my head. It's on the set up sheet at the shop. I agree, it's a lot to change at once but I've just fitted new cartridges and a completely different set of tyres so I'm basically starting from scratch. I'll put the forks down to 5mm. I set them flush earlier today, thought that was stock. The bike damping/preload is a guess for a track set up for Sunday but running road pressures until the day. I'll have a better idea what's going on then and from that we'll make more adjustments until it's right. I'll figure out some road settings after the track day.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Silent singer » Sat Apr 23, 2016 8:22 pm

Rear rider sag is 40mm. With the forks back to stock position (5mm) it's definately better. At 3 lines it was 7.5mm, 2.5mm between lines. Still haven't ridden fast enough to upset it. It was stable today at 120mph so it's a step in the right direction.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by wsmc99 » Mon Apr 25, 2016 4:14 am

Silent singer wrote:Rear rider sag is 40mm. With the forks back to stock position (5mm) it's definately better. At 3 lines it was 7.5mm, 2.5mm between lines. Still haven't ridden fast enough to upset it. It was stable today at 120mph so it's a step in the right direction.
Yep, sounds like it's in the right range now.
I have no stability issues whatsoever at any speed.
funny thing that my girlfriend said she had some shake at higher speeds and I asked her where she was sitting on her bike. Way to the back. Told her to move forward when it happened again, it went away. Time for some more rear preload for her!
you also can play with lightening the rebound which can help a bit if the shock packs down.

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Re: HELP: High Speed Wobble, Possible Supension Adjustment?

Post by Silent singer » Mon Apr 25, 2016 5:45 am

Another interesting possible cause to a speed wobble that is hadn't considered is that when I put the bike on the Abba stand yesterday the rear tyre was still touching the floor. I could still spin it reasonably easily but it was rubbing the floor which it didn't do with the Dunlops. The Metzeler Sportec M7 RR it seems is quite a tall tyre and I'm guessing would have the same geometry effect as dropping the forks through the yokes. I say guessing because I changed the front as well and I have no idea if the front is also slightly taller than the standard Dunlops to even it out.

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