unstable k12rs after tyre change

[BANKSIE]

running a 2003 k120rs that came with Metzeler Z4's and the bike was utterly stable. Changed to Bridgestone 020's no difference except price so this next tyre change went back to Metzeler but they no longer do Z4's its now the Roadtec Z6. Since fitting these the bike weaves/corkscrews along at any speed above 75mph. Bought the tyres from BFM Tyres and they supplied standard Z6's the Metzeler web site states that the rear should be a special fit. BFM say not. I would like to know whether anyone thinks its a tyre fir problem ie Z6's don't work or whether it should have the specific tyre and would this cure the weave.

[Mr_Ed]

I would verify that they mounted the correct tire size... if that is OK then make sure they mounted it the right way... look for the arrow indicating direction of rotation. The refernce to there being a special "size" might instead be around getting one of the "B" rated tires... the "B" tires have stiffer sidewalls to better handle the weight of the K. Those are my best guesses... will see if someone with more knowledge gives you some more.

[ghaverkamp]

Who remounted the front wheel?

 

Compression of the front end before tightening the axle pinch bolts can be critical. Failure to do so can lead to symptoms such as those you described.

 

Greg

[ELP_JC]

First of all, the 'B' designation has NOTHING to do with your problem. In fact, if you're not riding fully loaded (close to GVWR) often, I wouldn't get it.

 

Now, your problem can be one or a combination of the following 5 issues:

1. Improperly installed tire(s). Check that the bead is fully seated ALL AROUND on both wheels.

2. Improperly installed front wheel (like Greg said). Check the manual for proper procedure; you can do this yourself.

3. Lack of the spacer on the rear wheel, if needed (the latest version of my 5.5" wheel didn't need it). ALL 5 inchers need it, by the way. Remove wheel and check if it's there (easy to do, and torque the bolts to 76 ft/lbs).

4. Lack of, or improper balancing. If no weights are present, most likely they weren't balanced (it's rare both wheels balanced perfectly, but possible, I guess). I'd buy a Mark Parnes balancer and DIY (or borrow one for now).

5. Defective tire. Again, rare, but possible. Check them thoroughly for unusual bumps.

 

Different tires make your bike feel different in curves, but straight performance should be pretty much the same. Keep us posted.

[Calvin (no socks)]

3 sets of Z-6s here, no B needed, solo travel...ok... I have a shim in the rear of my GT. I have seen them fall out while someone is working on their bike and they did not notice them. Also, the new tires wander around the first few miles after installing. That may be your weave thing...

[ShovelStrokeEd]

I had a bad front tire on my K12RS. Installation was fine, tire was just bad, ran out a good 1/2" at the tread center. Easy to check, place bike on center stand with front wheel in the air, hold a pencil on the fork leg and extending first to each side wall then to the center line of the tire. Observe gap or push while spinning the tire.

 

It does happen. Made my bike unrideable at speeds above 45 mph. Was fine up to that point with just a little weave at the bars. By 45 it would almost tear the bars out of your hand.

[cat0020]

This may be a stupid question, but were the wheels ever balanced after the tires have been mounted?

[gezerbike]

I'm on my 3rd set of Z6's and love em......this may sound over simplistic, but I've seen no mention of proper tire pressure here. Since everything is fine up to 75, I would suspect that the problem is not the tires or balance but in the installation of the tires and/or the re-mounting on the bike. You didn't mention who or how the tires were mounted. I've seen wheels get a little bent by trying to force modern radials on a rim with hand tire irons. Backtrack the steps and I think you will find the problem, especially using some of the advise in the above posts.