Front vibration

[frodef]

I've had some sort of vibration from my K75 for a while now, it seems to be most noticeable when the bike is warmed up a bit and at lower speeds. I think it's from the front and it's there regardless of whether the clutch is engaged. My prime suspects are the front tire and front bearings (in my mind the tire was "newish", but turns out I last changed it in 2011..). I'm replacing both shortly, but thought I'd ask here first for other ideas / possibilities that I might want to look into while having the wheel off..?

[TimTyler]

You could ask whomever is changing the tire to check the wheel for balance and true with the tire off.

With the wheel off you can turn the wheel bearings with your fingers to feel if they're smooth or have play.

With the wheel off you can loosen the forks in the fork brace, re-install the axle, and re-tighten the axle then the forks to make sure the alignment is proper.

With the wheel off and perhaps the forks removed from the bike you could check the tightness of your steering head bearings. Maybe even clean and lube them.

[frodef]

Thanks Tim! Regarding the steering head bearing we were taught when I took my license to have someone push the rear wheel down (if necessary) while centerstanding and push/pull the front wheel to check for play. No play when I tried this last time. Would a worn steering head bearing cause vibrations typically?

I'll be changing the tire myself btw. Got the tire cheap from someone who got the wrong dimension  :deal:

[TimTyler]

Would a worn steering head bearing cause vibrations typically?

Oh, I dunno  :dunno  I just thought it would be worth checking if you have the front end apart.

Front-end vibrations can also be caused by whack in the rear of the bike, like a rear tire and swing-arm bearings.

[johnny]

greetings frodef...

what i would like to know at what speed does it commence to vibrating and at what speed does it stop vibrating...

is the vibration the same the whole time or does it intensify at any point...

what happens when you take both hands off the grips during the vibration...

are you running both bias ply or both radial or one of each... tell us more about the tiors...

how many miles since you replaced the suspension fluid...

j o

[frodef]

Hi Johnny, sorry but the speed thing is a bit fuzzy.. typically when I start up I think "this is barely noticable", then I drive for a while and when I exit the motorway and slow down I think "holy shit this is bad, must fix asap!". Repeat. So.. I can't really feel it at all above say 60 km/h or 35 mph, and below that it's anywhere between faint and scary.

Actually I first noticed this at the end of my pan-european trip last fall. Got a new rear tire (metzler lasertec) while wintering in italy, alas that didn't fix the problem for the trip back this spring (rules out the rear tire though). The (soon to be replaced) front tire is a bt45. Don't think either is radial, but that's one of those subjects I really haven't looked into at all.  :dunno

Don't think anything really happens when I take hands off the grips.

There's FLUID IN MY FORK!?!  :euro   :mbird    :falldown:  ahem.. that's one of those things I've managed to pretend doesn't exist, haven't touched it in the 5 years I've had the bike. Guess it's time.

[rbm]

Is it an up/down type vibration that varies with speed, becoming pronounced at 60 KPH but barely noticeable above and below that speed.  If so, that would probably be tires causing it.   DAMHOK.

[frodef]

I finally got around to actually work on this, i.e. take off the wheel to replace at least tire and bearings. I took off the wheel and put it on the balancer, and while it (i.e. the old tire) seemed reasonably balanced I finally noticed a buckle on the lip of the rim. I'm guessing that's the source of the vibrations I felt. I used a block of wood and a hammer on it and got it reasonably straight I think.

However, my primary concern right now is the bearings. I got the old bearings out (they seemed fine really), but when I put the new ones in I must have pushed too hard or something, because the spacer seems to be stuck between the inner races of the two bearings, meaning that the spacer is forced to rotate with the inner races and there seems to be more friction there than I like. I don't understand how this could happen because I imagined the lips against the outer races should be slightly further apart than the spacer is long... any ideas anyone?

[frodef]

Well I went for my tried and true method of ignoring all potential problems and put the wheel back on with fresh (but somewhat stuck) bearings and rubber. I made a short test run and the vibration seemed to be gone, although I have to take a longer trip to know for sure. So in all likelihood the problem was the bump in the lip of the rim, which I should have noticed earlier. So sorry about the noise here but thanks for all input and patience. Off now for two weeks of family (aka bikeless) vacation.  :yippee: