‘91 K1 Bent wheel tolerances?

Is there a standard for how much is too much? I've never checked this before, so excuse me if my terminology is incorrect. I'm installing a new front tire on my 91 K1 and thought I would check the run out of the wheel. The ride feels fine at speed, though it seems to pick up a little more vibes around the ton. This might be normal for an older K, I don't know because this is my first one.

After removing the old tire I reinstalled the wheel back into the forks. On one side of the wheel the side to side run out varied as much as .037" and the run out for the diameter varied as much as .016" For the other side of the wheel the side to side run out varied .025" with the diameter run out varying .010" Is this too much and something to worry about? Thanks!

I don't have those specs for a K75, so I looked up the specs for a spoked F650 and for a cast wheel on an R1150R

The radial and lateral runout for the wheels on an R1150R are:

Rear wheel - .019" or .5 mm
Front wheel - .011" or .3mm

The spec is the same for the R1100S

For the wire spoked F650 wheels they are more tolerant.

Lateral and radial runout for both front and rear is .08" or 2 mm

I would expect the spec to be about the same on the K75 as for the other cast wheels. But the spec for the spoked wheels probably defines an outer limit where you will feel it.

Thanks Paul, that's just the kind of info I was looking for.

I dug out my Clymer manual for the classic K bikes.

Wheel tolerances are specified the same as above for the R1150R and R1100S

Frame Man

And if yours are out, you can send them to The Frame Man in Sacramento. I have had great experiences with their work on several different bikes. They even checked one and called me to come get it with no charge because it was still within tolerance.

What you will usually find with the three spoke wheels since so much of the rim is unsupported, is when they strike an object/chuckhole hard enough or if the air pressure is too low, they will bend at the rim/ flange area.

Chances are you have one single "dent" in the rim area. Check the locations of the "high" spots of the side to side runout on each side. See if they are at the same spot. A hit on the rim will usually flare out the flanges of the rim making it wider at that location.

That will also usually coincide with the low reading on the diameter.

I have some rims that have that much runout and have not noticed any issues. But I usually only exceed 100 in spurts (passing lines of cars). Very seldom am I riding on roads that I can hold it for any length of time either because of the road or because of Officer Obie.

But if you want to make sure it is absolutely right, the Frameman in Sacramento http://www.motorcycleframeman.com/ does outstanding work. He straightened a 3 spoke K75S rim for a bike I was working on. It was bent over 1/8". He got it within .007" axially and radially. I believe the cost was around $125. Not bad for a $750 wheel.

All that being said, I would first make absolutely sure your tire balance is right. Most bike shops use a single arbor electronic balancer. They also have many young kids just out of high school mounting and balancing the tires as their first job in the shop.
All it takes is one time with a heavy wheel and a careless kid to bend the arbor on the machine for EVERY wheel from then on to be balanced incorrectly.

That's why I now have my own static balancer. I can get them within 1/8 oz. (shops will only get them within 1/4 oz.) and I can recheck them every time I have the wheel off.

98lee said:

All that being said, I would first make absolutely sure your tire balance is right. Most bike shops use a single arbor electronic balancer. They also have many young kids just out of high school mounting and balancing the tires as their first job in the shop.
All it takes is one time with a heavy wheel and a careless kid to bend the arbor on the machine for EVERY wheel from then on to be balanced incorrectly.

That's why I now have my own static balancer. I can get them within 1/8 oz. (shops will only get them within 1/4 oz.) and I can recheck them every time I have the wheel off.

Click to expand...

I agree, I static balance my tires and have had no problem with speeds well over the ton (don't hit it too much, but sometimes when the planets line up.)

Ralph Sims

I had these guys repair the front and rear rims on my K11RS. Tighter than BMW spec. has a "rimjob special" going on thru the month of October. http://www.mcwheel.com/
btw- at 100mph, you should not experience handling issues on a K1.

Thanks!

Thanks everyone for your input and advice. Actually the K1 handles fine at 100mph, it's rock solid. I was just changing the front tire and thought I would check the runout which I have never done before and was ignorant of it's tolerances. It's just that it seems like I am noticing a little more buzz at 100 than I do at 80, not bad all though. I guess it could be engine vibes or even feedback from the front tire because it was wearing a little uneven nearing the end of it's life. My new tire is due to arrive Friday. Thanks again!

A few thoughts from someone who's experienced a bent and unbalanced front rim on bmw GS models...

1) bent and balance feel very different. Balance is bumpy, vibrating. Easily fixed with weights. Bent (as in not straight) is a left right wobble, and far more concerning, I'd say dangerous.

2) yes it can have significant effect, especially at speed since the bike is essentially self correcting it's path Everytime the wheel goes round once. (Google physic of motorcycle) May not be an issue most of the time, but when you pass that trailer, or get that mighty crosswind the two could easily set the bike too far off, causing terminal wobble.

3) for anyone that rides sand you'll find out quickly just how much effect it has on riding straight lines even at slow speeds.

I found a used parts bike and swapped out the rim for immediate relief. If you can do the same as our have a buddy with similar, it's an easy test.

Still have my bent cast rim (2mm run out) to see if someone can salvage.

Ride safe!