Tire Problem ... "DEATH WOBBLE"

BumpaD_Z28 · January 06, 2009, 12:13:49 PM

A little (OK A LOT) of history first ...

When I bought my bike in Feb 2008 it had on AVON Viper Sports, a 120/60 FRONT, and a 170/60 rear ...
I didn't like the smaller 120/60 rear, so I sold it to a Bandit 600 buddy and bought a NEW AVON Viper Sport 120/70 front ...

Then head off in the spring on a 300 + mile ride to Southern UTAH. When we got there the same friend I sold the front tire too (ironic) noticed that my rear tire was showing "white cords". I had worn it out on the way down, probably due heat / some VERY high speed freeway runs. Anyhow ONE of the local shop had ONE tire choice in 170/60 a DUNLOP Qualifier. Good tire I figured, so I went with it (as if I had a choice) ...

Well on the 300 + mile ride home, right at freeway speeds ~80+ MPH, I got / get what I like to refer to as "DEATH WOBBLE". Had a VERY scary (even after slowing down), VERY nerve racking ride home. Then throughout the summer I tired to fix the "DEATH WOBBLE" with the DUNLOP rear ...
1. Checked my axle alignment MULTIPLE times
2. had the DUNLOP dealer re-balance the tire
3. had the DUNLOP dealer warranty a NEW Qualifier in 170/60

All the same result "DEATH WOBBLE" at steady freeway speeds of ~80+ mph

So my options as I see it, FIX THE mismatch !!! And PRAY

the "DEATH WOBBLE" goes away:

1. Buy a new front DUNLOP Qualifier to fix the mismatch ...
(don't really favor this option as I never had a wobble until the mismatched F*ing ~~DUNLOP Qualifier~~, don't know if I can stomach having DUNLOP's, and my front tire is still fairly new.)

2. Buy a new rear AVON Viper Sport to fix the mismatch ...
(kind of a pricey "sport" tire, and "currently unavailable" at my favorite retailers)

3. Buy a new front and rear BRIDGESTON BT016

(again matching) ...
(are the BT016's "too much tire" for my 5k+ a year M900 ? Would you suggest the BT014 or BT021 instead? I do like spirited canyon riding, in between the boring freeway stretches !)

THANKS for your time / HELP ! I need to get this fixed before my first freeway outing in the spring

~DaVe

He Man · January 06, 2009, 01:46:39 PM

Are you sure its the tire?

I had this death wobbble on matched tires. Its was a suspension problem though.

BumpaD_Z28 · January 06, 2009, 02:52:18 PM

Quote from: He Man on January 06, 2009, 01:46:39 PM
Are you sure its the tire?

I had this death wobble on matched tires. Its was a suspension problem though.

Well ... I'm not 100% sure ... It occurred directly after the tire install, so I concluded that it was either the tire mismatch, or something the tire tech "broke" / screwed up

Hoe do I diagnose a suspension problem ?

I did try and adjust the shock softer / firmer ... and it didn't change the wobble ....

THANKS !

~DaVe

Porsche Monkey · January 06, 2009, 03:00:34 PM

I agree that its most likely a suspension issue. Go over all your suspension mounting points and make sure everything, including bearings are how they are supposed to be.

I have a set of BT-016s. They are a great tire in the twisties. When they warm up they stick like nothing else. I would not expect to see more than 2500 miles from them though.

clubhousemotorsports · January 06, 2009, 05:58:51 PM

just my .02 I doubt it is the tire.

If it was not there before the dunlop was installed then I would look for something assembled incorrectly. does your rear axle nuts take torque (is the spacer backwards)?

different tires can change the way the suspension reacts, they are your first suspension.
is tire pressure correct?
is the suspension cranked up in the back or is it stock?

does the bike "wobble" all the time at the exact speed?
does it just wobble when hitting bumps?
does it wobble if you hang on tight or loose to the bars?

does the bike have a damper?
if so what is it set on (full in,out or in between)?

BumpaD_Z28 · January 06, 2009, 11:42:02 PM

Quote from: Ducaholic on January 06, 2009, 03:00:34 PM
I agree that its most likely a suspension issue. Go over all your suspension mounting points and make sure everything, including bearings are how they are supposed to be.

I have a set of BT-016s. They are a great tire in the twisties. When they warm up they stick like nothing else. I would not expect to see more than 2500 miles from them though.

How can I check the bearings without replacing them

Quote from: ducvet on January 06, 2009, 05:58:51 PM
just my .02 I doubt it is the tire.

WOW !!! now I'm really confused, if everyone thinks it is a suspension related issue, this could be BAD

...

Quote from: ducvet on January 06, 2009, 05:58:51 PM

If it was not there before the dunlop was installed then I would look for something assembled incorrectly. does your rear axle nuts take torque (is the spacer backwards)?

different tires can change the way the suspension reacts, they are your first suspension.
is tire pressure correct?
is the suspension cranked up in the back or is it stock?

does the bike "wobble" all the time at the exact speed?
does it just wobble when hitting bumps?
does it wobble if you hang on tight or loose to the bars?

does the bike have a damper?
if so what is it set on (full in,out or in between)?

The rear axle nuts do take torque and the spacer is in the correct way (I hope ! will check again ...)

I have played with the tire pressure up and down with the same results.

I have never moved the "spring preload" on the rear, only the slotted shock adjustment (back to stock now).

It does wobble all the time at the same speeds (within -+5 mph), bumps don't seem to affect it, and I have tried to hold loose and tight to the bars, BUT the wobble seems in the rear as the front / steering seems "steady" ...

And no dampener ...

THANK YOU everyone for the help, I have ignored this issue for awhile because it was making me think extreme thoughts, like buying a for sale sign !!!

~DaVe

Howie · January 07, 2009, 03:26:25 AM

Wheels true? Balanced?

Langanobob · January 07, 2009, 03:44:03 AM

I'm at a loss to come up with an explanation. Something doesn't quite seem right that, assuming your rear first rear tire was serviceable when you left., that it would be down to the cords after only 300 more miles. But I don't know what would point to as far as solving your problem.

Don't want to sound like a hand wringer but your "Death Wobble" name for it is a little too apt and I wouldn't ride it in the spring until you get a damper, or find a definite cause over the winter. Not sure how the damper will work if the problem is coming from the rear, but it can't hurt. Are the motor mount bolts all tight?

Since you've re-balanced, re-aligned and even changed the rear Dunlop again with no results, can you try a different front tire just to absolutely for sure eliminate it from the equation?

He Man, when you had a similar problem and it turned out to be the suspension, what specifically was the suspension problem?

Don't think I'm being much help here, just clutching at straws.

Porsche Monkey · January 07, 2009, 05:31:34 AM

A damper is/may only mask the problem. You need to find the source of the wobble first before you put a band aid on it.

Norm · January 07, 2009, 07:21:06 AM

As stated above, don't put a damper on to the fix a problem, find the problem 1st. A damper is always a good idea, but only for insurance. Mismatched tires sometimes work and sometimes they don't, put on same brand/model tires and save the ones you have for.............?
Next, if you don't have clip-ons, find another way to put more weight on the front end - the wobble may go away and you bike will handle much better in the twisties with a little more forward weight bias.
Finally, set up, or have someone help you set up your suspension properly. Whether or not it is part of the current problem, your bike will be safer and faster at the same time. It should be a first do for anyone picking up a new bike.

Langanobob · January 07, 2009, 07:35:56 AM

Quote from: Ducaholic on January 07, 2009, 05:31:34 AM
A damper is/may only mask the problem. You need to find the source of the wobble first before you put a band aid on it.

+1. I should have been more articulated with my post. I didn't intend that a damper be more than something to keep the bike safer while he was test riding it if he hasn't found the problem by spring. Did not intend to sound like a damper is a permanent fix. Thanks for pointing this out.

Speeddog · January 07, 2009, 08:08:01 AM

Have you checked that the wheels are actually aligned?

The marks on the swingarm aren't super accurate, and the plates have quite a bit of clearance on the axle hole, so in total it's not a very good way to judge alignment.

Also, check that the motor mount bolts are torqued to spec.

BumpaD_Z28 · January 07, 2009, 09:52:52 AM

Quote from: howie on January 07, 2009, 03:26:25 AM
Wheels true? Balanced?

Well yes as far as the DUNLOP dealer in my area goes, it is balanced, very little weight on it, and it appear to spin "true"

Quote from: Langanobob on January 07, 2009, 03:44:03 AM
I'm at a loss to come up with an explanation. Something doesn't quite seem right that, assuming your rear first rear tire was serviceable when you left., that it would be down to the cords after only 300 more miles. But I don't know what would point to as far as solving your problem.

Don't want to sound like a hand wringer but your "Death Wobble" name for it is a little too apt and I wouldn't ride it in the spring until you get a damper, or find a definite cause over the winter. Not sure how the damper will work if the problem is coming from the rear, but it can't hurt. Are the motor mount bolts all tight?

Since you've re-balanced, re-aligned and even changed the rear Dunlop again with no results, can you try a different front tire just to absolutely for sure eliminate it from the equation?

He Man, when you had a similar problem and it turned out to be the suspension, what specifically was the suspension problem?

Don't think I'm being much help here, just clutching at straws.

Well the rear was on the way out, I just didn't think it would be GONE in a 600 mile trip, that one was sorta my fault, BUT I guess if I would have replaced it before leaving it might have wobble both there AND back

And after all the times I have had the rear wheel off the bike, I feel like I'm just clutching at straws also

Quote from: Norm on January 07, 2009, 07:21:06 AM
As stated above, don't put a damper on to the fix a problem, find the problem 1st. A damper is always a good idea, but only for insurance. Mismatched tires sometimes work and sometimes they don't, put on same brand/model tires and save the ones you have for.............?
Next, if you don't have clip-ons, find another way to put more weight on the front end - the wobble may go away and you bike will handle much better in the twisties with a little more forward weight bias.
Finally, set up, or have someone help you set up your suspension properly. Whether or not it is part of the current problem, your bike will be safer and faster at the same time. It should be a first do for anyone picking up a new bike.

When I first got the bike I did raise the rear suspension a little bit (I think 1.5 turns out on each adjuster?) But rode it that way for quite awhile without the wobble issue ... I'll work on more suspension adjustment

Quote from: Speeddog on January 07, 2009, 08:08:01 AM
Have you checked that the wheels are actually aligned?

The marks on the swingarm aren't super accurate, and the plates have quite a bit of clearance on the axle hole, so in total it's not a very good way to judge alignment.

Also, check that the motor mount bolts are torqued to spec.

Yes I've aligned the rear wheel a few different ways, I'm not using the marks on the arm ... I've used a straight edge on the sprocket, a laser, and even another method of a small screwdriver in the chain / sprocket to "set" the wheel / chain tension, and then tighten ....

Anyone know the engine mount spec off hand (I'll find them in the service manual eventually ...)

THANK AGAIN everyone !!!! I gotta get this bike figured out

~DaVe

Capo · January 07, 2009, 03:06:14 PM

Check your steering head bearings

clubhousemotorsports · January 07, 2009, 04:52:28 PM

Okay so let me re-cap
original tire= no wobble
new tire =wobble
different new rear tire = wobble
rear tire balanced twice = wobble
rear wheel aligned = wobble
no damper = damper not bad
rear wheel assembly correct per manual?
happens at same speed +- 5mph

what speed is it again?
wheel bearings checked for play side to side?
swingarm shimming checked for play at the swing arm pivot?
steering head bearings checked for detents?
slotted adjusters?
motor mounts tight?
no cracks at motormounts?
check for cracks at frame , monsters tend to crack at the center between the two motor mounts where there is only one tube.
cracks on triple trees?

To be honest if this has been an issue I would find a good shop and have them give it a once over you may be missing something, these bikes do not have death wobbles normally. I would saY THAT IT SHOULD BE A FAIRLY EASY FIND FOR A ( damn caps lock button) good mechanic. I do know that the dunlops tend to be stiff and this could affect your suspension but I doubt it would only be at one speed. I would look for something damaged or worn at this point.

I had a customer bring me a monster last summer to fix his starting problem, he never had noticed his frame was broken and steering head angle is now around 19 degrees with the front tire contacting the head. He never noticed a handling problem, I would have yours checked by a pro. It may be a tiny fix and not worth fighting yourself. Or you might find out you need a new bike.

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Tire Problem ... "DEATH WOBBLE"