Rear Wheel balance

[kajendog]

Hi,

New poster, long time lurker.

My 2000 KX 500 rear wheel really vibrates, seems out of balance.

I have trued the rim side to side, but failed to check how true it is in the diameter. The problem is the same after multiple new tire changes this summer.

I was wondering if because of only 1 rim lock, it would cause enough of an out of balance to be significantly noticeable around 40-50 MPH. I haven't seen this discussed before so am thinking I may have an out of round rim.

Any ideas/suggestions would be appreciated.
Thanks!

[Paul]

Hmm, thats a good question. I'm pretty sure Rick will be along shortly to share a pearl or two of wisdon. I have two rim locks on my bike - makes it easier to ride back if it pinch flats - I haven't noticed too much vibration from back there though.

[DanH1]

Yes the one rimlock will cause it to be out of balance and is notcable if you are riding on a smooth surface. Offroad/MX track you probably would not notice it.      
  Is there any visible runout when the tire is spun to indicate an out of round/bent rim?
  Depending on what brand rimlock you have about 2.5 oz +/- should do the rear, 1.75 oz +/- for the front.
  I always balance mine for running the Pikes Peak Hillclimb -class A dirt track tires on asphalt and gravel race course, speeds 95+mph.

Dan

[kajendog]

Thanks for the input.

The rim and hub are stockers, and came with only 1 rimlock.

Yes I only notice the vibration when I have to connect a loop trail by an asphalt stretch or very hard dirt road.

Next tire change, I will check the roundness of the rim, then I will add a second rim lock opposite of the stock one. Check the rim balance, mount a tire check the tire balance. I am not trying to be anal, it really is a significant vibration.

Thanks for the input.
Kajendog

[dezracer]

What about the wheel bearings?  I always use 2 rim locks.  It sucks to have a rear tire come flying off the rim at speed when you get a flat.

[KXcam22]

That's a good idea to add a 2nd rim lock.  All my old european bikes had 2, but I never considered adding a 2nd to the KX.  I always wondered why they didn't put the single rimlock opposite the valve stem to help the balance, but It is propably to make tire changes (or manufacturing) easier.  I will definitely add a 2nd this winter when I put on a new rear. Cam.

[Rick]

Ok, Paul, here I am, ready to post.

You guys with two rim locks must be moma's boy's with no sense of adventure...   (Just kidding).

On the balance issue, those who still run the Reno to Vegas event balance the wheels front and rear, but this is because of the sustained HIGH SPEED running.  If you're not running sustained high speeds, balancing should not be necessary.

With that said, you probably have another problem relating to the rim.  I think You mentioned you checked the side-to-side alignment of the rim, but don't remember you indicating you checked the outside of the rim in relation to the hub.  You can check this easily by clamping a srewdrive to the swingarm and rotate the tire while watching the rim's movement in relation to the screwdriver.  I would not be surprised to hear that the rim is not centered on the hub.  This is not real tough to fix, so just post up if that is a problem.

Finally, in my oppinion, balancing an offroad rim is a waste of time, as I do not believe any weights installed can stand the abuse of the offroad environment.  As for two rim locks, I stay with one, as it makes for a faster tire change.  With all the racing and riding, I have had two flat tires, both on the front.  However, even with only one front rim lock, I still rode just under 90 miles in a California National Hare & Hound without a problem...OK, the bike was a little squirrelly in the deep sand, but that was all the more reason to keep her pinned.  

Rick

I'll be curious to hear what you find as you investigate further.

[GreenMachine]

I usually don't post after Rick, cause his 2 cents are usually the last thing that needs to be said. But I have been balancing my rims(both front and back) For a while now. I noticed alot of vibrations while doing top speed testing so I decided to balance the wheels to see if it was coming from there. This is how I did it. Don't need any fancy wheel weight or machines.  All ya need is a roll of solder and some time. with the bike on a stand you must take off the brake rotors. Then I do a 4 point static balance. Mark off 4 points on you wheels. (90 deg. apart from each other.) Set one of the points at the top and let the rim go. It will probably start to move. (oh did I mention I do this after changing bearings) Let the wheel settle. once it stops moving, take some solder and wrap it around the spoke right next to the nipple at the highest point on the rim. If the solder ends up at the bottom remove some of it. continue doin this until you can put all of the 4 points at the top and the wheel doesn't move.

This should not be used as a band aid fix for a out of true wheel. That should also be checked.

Just my 2 cents.
Later,
Wig

[Rick]

Wow, now that's creative balancing!!  I've marked this post as being added to my book of tricks.  This process is so simple that it can be done every time you change tires.

A question:  How do you keep the solder from flying off the spokes once your done balancing?

Thanks

Rick

[Rick]

Wow, now that's creative balancing!!  I've marked this post as being added to my book of tricks.  This process is so simple that it can be done every time you change tires.

A question:  How do you keep the solder from flying off the spokes once your done balancing?

Thanks

Rick

[GreenMachine]

Rick,
Well, it really very simple. I use thick plumbing solder and wrap it tight. It will come "loose" but will not come off. The trick is to keep it from slinding down from the rim untill you are finished balancing the wheel. Then after that the centrifugal force will keep it at the rim end of the spoke, which is where they need to be to balance the wheel any ways. Some times when you push your bike you will hear them sliding up and down the spoke. I have never had a piece come off. And I have checked the wheels after installing a new tire, and they usually seem to be fairly balanced.

Later,
Wig