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  #1  
Old 04-13-2017, 09:53 AM
bmilleria bmilleria is offline
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'07 K12GT High Speed Shimmy - New Tires

Hello all,
I have a question about my 2007 KGT that has me baffled. I recently hit about 8500 miles on my old set of Pilot Road 4 GT tires, and I couldn't be happier with them, but they were worn out, so I purchased a new set of PR4 GT tires, and had them installed. I mounted and dismounted the wheels myself, but had a local Honda dealership actually mount the tires. I got the new wheels and tires home, got them mounted, and took it to work the next day.

Now here's the problem/question... Anything above about 60mph up to around 82 (could be higher, but that's the fastest I've gone), I get a shimmy from the front end. If I had to describe it, it would be like following an 18-wheeler, even though there was nobody around me and it wasn't too windy. The front wheel just felt like it stepped right and left.

I've done some research on this forum and other forums, and I've read about issues with load ratings with tires, ball joints, etc. I am positive that the tires I put on were correctly rated, and there doesn't seem to be any play in the steering head. It didn't have this wobble right before my tires were changed, though I do seem to remember that I had kind of a similar problem the last time I mounted new tires. My current PSI is 39/45. The only variable seems to be when I put on new tires. Has anyone had this issue before?

Thanks for any advice/input, and keep the shiny side up!
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  #2  
Old 04-13-2017, 10:07 AM
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Re: '07 K12GT High Speed Shimmy - New Tires

Couple things come to mind. Raise the front end off the ground and spin it. Look for out of round or and odd tread wag. Tires may not be seated on rim, bad belts, out of round. Recheck air pressure. Keep in mind sometimes problems migrate. A faulty rear may show up as issues with the front. So repeat visual test on rear wheel. Also loosen all the front bolts, axle, fender, etc, then sit on bike, lock front brake and bounce the front end. Idea being something might be on a bind and needs a good bounce to line it up. After, get off the bike carefully and retighten everything. Tighten in a pattern, slowly working up to proper torque. While the front is up in the air check ball joints, bearings for play. I have seen wear issues show up when new tires are put on. Not sure why, maybe old tires were so vague I didn't notice, new tires made it more obvious? Don't just look at the front, give rear and front equal time. I had one bike that had a death shake to the front, almost tank slapper, and it was loose spokes on rear wheel. Loosen the brake pads and roll tire, if you can get it to spin freely, see if it shows balance issues. Does it stop at the same spot? Or roll back and forth? I'm thinking it is a faulty tire and/or install issue, on front or back. Dark beer for tire problems. Added thought. Balance issues usually show up over 45 mph, out of round or bad belts under 45 mph.
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Old 04-13-2017, 10:41 AM
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Re: '07 K12GT High Speed Shimmy - New Tires

Quote:
Originally Posted by bmilleria
... I get a shimmy from the front end. If I had to describe it, it would be like following an 18-wheeler, even though there was nobody around me and it wasn't too windy. The front wheel just felt like it stepped right and left ...

Your problem could be tire related but what you are describing sounds exactly like bad ball joints, a common problem in the early slant-K bikes. It is often misdiagnosed as a tire problem because tires changes can make the problem more noticeable.

The way to check is to put the bike on the centerstrand with the front wheel off the ground, then grasp the wheel carrier on both sides at the axle and see if there is any play in the front suspension. There should be none whatsoever and if there is... time to replace the ball joints.
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Old 04-14-2017, 12:49 AM
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Re: '07 K12GT High Speed Shimmy - New Tires

Did you static balance check them prior to reinstalling?....
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Old 04-14-2017, 01:38 AM
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Re: '07 K12GT High Speed Shimmy - New Tires

I would try setting the tyres pressures to what they should be first - 36 front, 42 rear (unless you have a very good reason for setting yours differently to the rest of us).

Give it another try & let us know.
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Old 04-14-2017, 10:29 AM
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Re: '07 K12GT High Speed Shimmy - New Tires

Since the wobble appeared after new tires my .02 would be bad balance or not balanced at all. This is a typical symptom as speed increases.

I've endured the bad ball joint problem and a wobble isn't symptomatic of that...ball joints are more like bad steering head bearings. Even if your tire is installed backwards it wouldn't induce a wobble.

Start with the easy stuff first...rebalance then see where you are.
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Old 04-14-2017, 12:44 PM
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Re: '07 K12GT High Speed Shimmy - New Tires

I guess we need to define what the OP meant by 'shimmy', but the description was 'like following an 18-wheeler, even though there was nobody around me and it wasn't too windy.' That describes a vague directional instability, not a wobble or shimmy. If the problem is a cyclical vibration then it is probably tire related, but if it is a vague wandering as feeling one is in a wind then that would not point to tire balance. The mention that the problem has persisted through multiple tire changes is also a clue.

In any event, checking the ball joints takes about ten minutes tops so there's no point in guessing or speculating, just check it and if it's not the issue then move on.
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Old 04-14-2017, 12:58 PM
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Re: '07 K12GT High Speed Shimmy - New Tires

I'm on the ball joint side, but your tire pressure is too high. Use the book pressure of 36/42. Having the tires changed at the honda shop says they did not balance the rear unless they have an adapter. If you say you are using dyna beads, I'm out of the discussion.
Does your bike have a weave at 30mph or so, ball joints. All the other checks mentioned sound good. ( have had bad ball joints and not been able to feel much by grabbing the front and trying to move it fore and aft but that is the check).
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Old 04-14-2017, 01:03 PM
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Re: '07 K12GT High Speed Shimmy - New Tires

Quote:
Originally Posted by Beech
( have had bad ball joints and not been able to feel much by grabbing the front and trying to move it fore and aft but that is the check).
Yes, in the early stages it may be difficult to detect the play. If ball joints are the problem it will continue to degrade though and sooner or later it will become obvious. Many of us spent a lot of time trying to convince ourselves it was just tires, myself included.
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Old 04-14-2017, 01:52 PM
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Re: '07 K12GT High Speed Shimmy - New Tires

Quote:
Originally Posted by bmilleria
My current PSI is 39/45.

45psi on the rears??? WHY? The maximum allowable pressure for these tires is 42psi. It's written right on the tire sidewall! What is the purpose of subjecting the rear tires to excessive stress?

As for the vibration you are encountering, it isn't ball ball joints.... as you say, the only thing that has changed is the tire. It's an impossible coincidence that the ball joints would suddenly become defective, at the very moment you changed tires!

It is far more likely that you simply have a bad balance job!
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Old 04-14-2017, 01:57 PM
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Re: '07 K12GT High Speed Shimmy - New Tires

Quote:
Originally Posted by RFW
It's an impossible coincidence that the ball joints would suddenly become defective, at the very moment you changed tires!
No one is saying that. However if the ball joints are on the way out the change from a worn to new tire profile can exacerbate the problem, or at least make it feel different. This makes it easy to confuse the two.
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Old 04-14-2017, 07:44 PM
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Re: '07 K12GT High Speed Shimmy - New Tires

Quote:
Originally Posted by millers
No one is saying that. However if the ball joints are on the way out the change from a worn to new tire profile can exacerbate the problem, or at least make it feel different. This makes it easy to confuse the two.
And it is a known problem and easy to check.
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