High speed wobble.

[fudgie]

We all left bike night last night and I was tooling down the interstate when I cranked it up to 100 mph. About 95 mph she started to wobble side to side. I slowed to about 90 and it went away. A few more sec and she woulda tank slapped and thrown me off. What causes this? Never happened on my old tires. New Bridgstone front (I was in a pinch), new General Evertrek rear, and stem bearing were retourqed, maybe a tad to much, all last week. Usually have a Metz front and a Hankook k-106 rear. Psi was good a few days ago. 38 in my CT. Max is 44.

[jimmytee]

I just had a similar scenario with a new set of Avon Cobras. The wobbly or fish movement as I described it would really come on past 80 mph. I took it to the shop where I bought the tires and had them mounted. The owner test rode it and said he didn't even know how I rode it up there. He felt the issue at much slower speeds. After checking it out , we decided it was a bad front Avon. Got a replacement and all is right as rain again. He, Danny, was perplexed, he'd never had a bad Avon Cobra, and was disappointed.

[fudgie]

Wish I woulda tried it with the front before I got the rear put on. It would help narrow it down. But since I put a new front and rear on at the same time, its kinda hard to tell which is which. Guess maybe new skins, again, all the way around this spring.

[Pete]

Almost every high or low speed wobble I have ever had was traceable to the front tire. I would start there first. Especially since you just changed it.

[fudgie]

Almost every high or low speed wobble I have ever had was traceable to the front tire. I would start there first. Especially since you just changed it.

My low speed wobble was due to my rear ct was bad.

[csj]

I presently have, and have had on two other occasions, a 100mph
wobble with a car tire. I'm able to remove the problem by
replacing the top shock bushings with new rubber ones.

But in about 5K, problem comes back cuz the rubber bushings
crush again. The nylon/neoprene ought to fix it.

[fudgie]

The nylon/neoprene ought to fix it.

Have those on. 

[Ricky-D]

If the feeling is that a replacement of the shock bushings fixes a wobble problem, a look farther should be concentrated on the swing-arm.

For if the swing-arm is solid no amount of shock bushing degradation should cause a wobble.

As evidence of this just look at single sided swing arms such as the Rune.

My feeling is, if a shock bushing replacement cured a wobble problem, it probably was more a correction of the reassembly process of the rear, such as the drive line and axle that was the true problem, more than a bushing replacement.

***

[KSDragonRider]

mine does it... it loves to do it with new tires and grooved cement freeway.  I can give her heck up the ramp, and about the time you are going to merge, you are hanging on for dear life!

I have found that i need to ride some crappy roads at slower speeds to scrub them in real good.  But yeah, every time I install a new tire front or rear, it takes about 2k on the grooved freeway before it stops that crap above 90.

The wifes solution is dont ride that darn fast... buzz kill.

[GJS]

I bought my 99 IS in 2004.
It also had a very dangerous wobble above 90+mph on a new set of Metzlers.
It was not always there and was worse when I went there quickly. I went through Kansas state at 105mph without issue, but I creeped up to that speed.

Had the same problem after I went to a new set of Venoms, only worse, started above 80mph.
(using balancing beads (2oz in the front 3 in the rear))

After the Venoms, I had a set of Dunlop D3s(?) (worst tires I have ever owned)
I lost road grip is a shallow curve (non-banked) and tumbled the bike because of it.
The bike was written off and i have since rebuilt it.
The D3s just lost their grip in a non-banked corner at 35mph

As part of the rebuild I did a very close inspection of the entire frame and replaced the shock bushings as well.

Went to a GoodYear Triple Tread CT in the hope of never loosing road grip again.
The CT was fabulous for gripping the road especially in the rain.
However, I still had a high speed wobble. (same D3 still on the front)

This spring I replaced both tires with 2 new Metzler 880s and my problem is gone.
Using standard lead weights to balance.
Just yesterday again, I went from 70-100 without any indication of a wobble.

I was sure it was not tires as I had already been through a number of tires with no/little change.

If it is not related to the tires, I can't imagine what else could have made the difference.

Good luck!

Cheers,

GJS