Bad vibe

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Danno

Danno

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While testing the Titanic, I noticed a judder in the front end at around 70-75mph. Looked down at the front wheel and noticed the tire buzzing in a tight wobble.

Back at the garage, I spun the wheel and held a piece of chalk with the fender brace and got this:

Bad vibe


This is one of four new Avon Roadrunner tires I bought for both bikes, although I don't remember the particular source. anyone else ever see one of these apparently warped at the sidewall?
 
Personally, I’ve never had a bad Avon, and I’ve had a few over the years.

Did you check the rim?
 
The rim has a tiny bit of axial and radial runout (as I said it's not perfect), but not near as much as the tire and there doesn't seem to be a corresponding flat or warp on the rim at the point the tire hangs out.
 
The tire is static-balanced like all the tires I mount and the vibe isn't apparent until you get it going pretty good.
 
I did have an experience of high speed weave/wobble with the old Avon Venom. I replaced the tire with the exact same size and model Avon. Weave/wobble was gone. Like L.A.B., I too suspected faulty mounting.
 
Is that a stock rim? I had some real trouble the last time I mounted tires getting the bead to pop out properly. The tire looked correct until you checked the bead carefully around the edge of the rim. I could see some spots where the tire was essentially trapped in the rim. I believe it is probably due to the narrow rim. I had to get it good and slicked up and get air into it from a compressor and not a hand pump.


Russ
 
Wouldn’t hurt to deflate, break bead (both sides), snot up beads and re-inflate.
 
L.A.B. said:
Are you sure the tyre bead is fully 'up' on the rim as it looks as if it might not be?
Click to expand...

It looks ok and I always overinflate when mounting tires, especially tubeless, so they seat on the rim. I guess I could deflate it, smear some NoMar lube around and then reinflate.
 
rvich said:
Is that a stock rim? I had some real trouble the last time I mounted tires getting the bead to pop out properly. The tire looked correct until you checked the bead carefully around the edge of the rim. I could see some spots where the tire was essentially trapped in the rim. I believe it is probably due to the narrow rim. I had to get it good and slicked up and get air into it from a compressor and not a hand pump.


Russ
Click to expand...
Stock original rim. I have a 90/90 on the front of the SS clone. I might just swap the two.
 
They can be a pig to fit and get on the rim square, looks like it is mounted across the rim, inflate it and bouncing it tends to get the bead settled concentric, check both sides are the same when done. I prefer to use chalk dust when fitting tyres to avoid any moisture getting behind the rim and under the bead.
 
I took several pics and blew them up and examined them and there appears to be a spot slightly clockwise from the 'bulge' where the tiny edge marks (I think there are 3 ridges) are not quite where they should be, sort of folded in a bit?

At the center of the 'bulge'
Bad vibe


A bit clockwise
Bad vibe


A few more degrees clockwise and this appears to be the center of the spot that doesn't look right (to me)
Bad vibe


The last pic is the area I'm going to concentrate on.
 
Thanks to all for the suggestions. With most tires, it's readily apparent if they aren't seated correctly. After close examination, I still can't really see if it is or isn't, so I will proceed as if it isn't and see if it makes a difference.
 
Yesterday I swapped front tires between the SS clone and the Titanic. The SS had a smaller, 90/90 while the shaky tire on the Titanic was a 100/90. A quick, 5-mile blast with speeds up to 75 mph revealed no vibes as before on the Titanic. Will try to get out on the SS today and see if the larger tire is still wobbly. One good sign, it took only 1 regular and 2 small spoke weights to balance on the SS's alloy rim and the smaller tire took one weight, just like before. The larger tire had taken 5 regular and 2 small weights before.
 
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