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My frontwheel is jumping up and down.

9K views 24 replies 14 participants last post by  ragnarher 
#1 ·
Some time ago I had a problem which I experience also other ATAS110DCT-owners has had. My steering was wobbeling. So I called a wheelguru who helped med adjusting the rim. His work made the "wobbeling" disappear. But between 48km/h and 68 km/h the front is going up and down in a really quick way. Has had the tyre cheked and it is ok. So I am wondering where this comes from. Ha anyone experienced anything like this ? I Am using the oem rims and Pirelli Scorpion STR 90/90-21.
I finds this extremely annoying so I hope that someone in here can give me som advice.
 
#5 ·
I agree with the balance but would give the tire a spin on the center stand just to see if its true.
Also when checking for true also check for out of roundness.
Thanks for replies. There is nothing wrong with my front-tyre or rim. I also replaced the front-tyre with a new one. Same ****. But I thouht maybe there can be an issue with the rearwheel in somekind so I checked the rear-rim. Maybe if the rim is out of balance, does anyone belive that this "offset" can spread to the front ? Because I measured a differense in 3mm at one part of the rear rim.
 
#6 ·
Being out of balance does not realy mean there’s anything wrong with the rim or tire. It means the weight of each is not equally distributed around the circumference. The wheel can even slip or spin inside the tire and cause a perfectly balanced setup to become out of balance. Are there any stick on weights or spoke wights on the front tire/wheel assembly?
 
#9 ·
If your wheel is true, spokes are tensioned properly and the tire is balanced, then consider the following.
What tires you are running and what is their condition and pressure? Heavily knobbed front tires like the Motoz rallyz, Mitas E10, Anakee Wild or TKC80 can cup badly with heavy front braking regardless tire pressure. Worn tires can influence bounce as can tire pressure.
Are your forks properly aligned and smooth? Compression and rebound set? Suspension sag reasonable? Too much fork stiction or wrong C&R settings can cause bounce. Improper sag - especially too much on the rear can impact handling.
Chain adjusted properly - looser is better. Cush rubbers in good condition. Have you tried changing what gear you are riding in? Sometimes the drive line gets into a rhythmic motion.
Does the bounce go away on smooth roads or if you ride on the centre strip instead of the vehicle wheel tracks? ? It's hard to see but many highways have undulations in the wheel tracks that cause the bounce at specific speeds that you mention.
My AT has always done it. Varies depending on what tires, pressures, suspension settings and speed.
 
#10 ·
I had a very bad wobble on my Atas a while ago. I had a pair Pirrelli Scorpion STR tyres fitted. My 3rd set.
Except this time the frond end was horrendous.. it had a serious wobble like speed wobble but much worse. If I loosened my grip it felt like the bars were torn out of my hands.
Unridable. After trying everything from changing the tube to checking the balance it turned out to be a faulty tyre. I sent the tyre back to Pirrelli and they wrote back saying they would refund the costs with fitting though they did not accept any thing was wrong with the tyre. A new tyre sorted the problem.
 
#11 ·
Not actually a fan of Pirelli tires for this reason... Great when they work, but not always consistent quality.

I would also check steering head bearings, while on the center stand. Tilt it with the front wheel off the ground, then grab the lower fork legs and alternate pulling and pushing front to back to see if there is any slop in the steering head. None is the right answer. Rotate slowly from center to left and to the right. Should be no "flat spot" in the center that feels like a bump as you rotate the steering. This is not likely, but worth looking at while you trouble shoot.
 
#13 ·
Some time ago I had a problem which I experience also other ATAS110DCT-owners has had. My steering was wobbeling. So I called a wheelguru who helped med adjusting the rim. His work made the "wobbeling" disappear. But between 48km/h and 68 km/h the front is going up and down in a really quick way. Has had the tyre cheked and it is ok. So I am wondering where this comes from. Ha anyone experienced anything like this ? I Am using the oem rims and Pirelli Scorpion STR 90/90-21.
I finds this extremely annoying so I hope that someone in here can give me som advice.
There is an easy fix for this: Just increase the rear tire pressure. I've got mine at 4 bar now, and no more wobbeling. Wobbeling was especially bad with luggage in the bike, so it has something to do with the rear tire.
My dealer put a lot of time in finding the problem, i later found it on a different forum with a different bike.
 
#19 ·
There is an easy fix for this: Just increase the rear tire pressure. I've got mine at 4 bar now, and no more wobbeling. Wobbeling was especially bad with luggage in the bike, so it has something to do with the rear tire.
My dealer put a lot of time in finding the problem, i later found it on a different forum with a different bike.
Have not tried what you suggests but normally when riding in terrain/forests, I normaly lowers the pressure in my tires.
What I noticed last night was that when it was cold outside and the bike was cold too, the jumpingproblem did not show up. After a few kilometres it came back but I believe that the oil in the suspension was warm.. Maybe the temeperature has something to say ?
 
#14 ·
Put some of this in it (actually both tires)
Run it for a few miles at the speed you get the issue at and see if that helps. Either way this stuff is worth it even if it doesn’t fix your problem.
If it does then it was a balance issue if not…
 
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#16 ·
You know, I have never really understood the physics of why beads or liquid actually can balance a tire... I am assuming that they provide some damping effect to the vibration, but I can't for the life of me figure out how they could improve balance.

But I'm just an IE (imaginary engineer, as my EE buddies would say...)
 
#21 · (Edited)
Hey B. The answer's pretty simple when you get down to it. Basically the heavy spot on the tire "pulls" or slightly accelerates the tire in the direction of its position relative to the axle. This centripidal force would be something in the range of delta-mass * rotation rate^2 * radius. This force on the tire acts in the plane of rotation. Anything inside the tire that can move (balance beads, Slime, etc.) will be "thrown" to the opposite side of the tire, working to even things out. Another way to look at it is via conservation of angular momentum (why most big objects in space are spherical), but those equations are uglier to work with.

This guy is a little dry to listen to so start the vid at 40 secs or so. He has great graphics. :p

 
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#17 ·
Beowulf, I have a wobble when decelerating from 50 to 30 mph after a drop.
We have minimized the wobble after many new parts, also removal of the back Shad case improves wobble issue.
However, the Africa Twin didn't wobble with case until the drop is my issue.

I am not sure what you mean by the Front going up and down issue after you solved the wobble by perfecting the wheel/tire balance. Please explain in another fashion if possible what is front up and down issue, weird to me.

Crazy the wheel and tire require 100% perfect balance, because nothing in life is really 100% perfect if made by a human/human robot.
 
#18 ·
I am not sure what you mean by the Front going up and down issue after you solved the wobble by perfecting the wheel/tire balance. Please explain in another fashion if possible what is front up and down issue, weird to me.
Just meant that when I had a tire out of balance, the wheel was oscillating significantly in the vertical axis (up and down.) Balancing it fixed it.

If it happened after a drop, maybe check the rubber bushings that the handlebar risers attach to. Looseness in the handlebar mount might be a problem that could allow a wobble.

If the rims are true and the wheels are in balance, and there isn't slop in the steering head, then maybe check damping on the rear shock. Note where it is set, then increase compression damping considerably stiffer than it currently is set to, ride, and see if it had an impact. Maybe check your static sag, with you sitting on the bike, and adjust preload. These bikes will wobble/wallow a little if the rear is way too soft.

Not sure how the drop could have affected the suspension, but that is were I would try next.
 
#23 ·
Once agian, thanks for all replies. It is really touching to see the engagement. I really apprechiate it.
I have finally found about what was wrong. As eralier said, I tried another tyre. Problem lasted. Kellox (thos who imort Honda to Norway) was not really helpful and suggested it was the tyre. Never anything wrong with Honda was their repy. Nice attitude :NOT: So being a little upset of all this I bout another tyre, put it on the rim an suddenly I realised that the problem was gone. Never thought that 3 tyres could have the same defect, but it was so. Wishes you all a happy week-end.(y):)
 
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