Front end vibration. Forks wiggling at high speeds.

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BruinFJRguy
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Re: Front end vibration. Forks wiggling at high speeds.

Post by BruinFJRguy » Sun Feb 09, 2020 7:21 pm

raYzerman wrote:
Sun Feb 09, 2020 6:49 pm
As I mentioned earlier, I was amazed on two FJR's now that the front wheels were so much off right from the factory and has so much clip-on weights installed on them....... I don't think your situation is all that unusual. The radial runout is a concern... did you measure that where the tire seats or out on the perimeter of the rim (less accurate out there I would say). Hopefully you had a dial indicator... Jes sayin', maybe it's not as bad as you think it is.
In cases like this, best balance the wheel separately and leave those weights on permanently.
Our measurement of runout wasn't that scientific. We spun it on the balancer on axle stands and held a stick to it. You could see the gap narrow and widen as the wheel spun, all on the outside. We did not measure inside diameter. It might not be that bad.

We had enough stick on weight to make it good for now. I might get a clip on for the center next time. We did mount the stick-ons near the center; 3 on one side of the center ridge and 3 on the other. Secured with black duct tape to color match. I'm satisfied. It's nice to ride without obsessively looking down wondering what is going on down there. :D

In other news, I've continued to tweak the front fork settings. Right now I'm at just a touch of pre-load on these .95 Racetech springs; about 3.25 lines/sections out. I've found the springs a little soft still. I know you suggested maybe 1.1s before I bought the .95s, but these are what I have for now. I'm running 10 weight Maxima fork oil right now I believe. Today I cranked front compression in to 4 clicks out; rebound is about 7. That seems to be a good setting. I'm suprised it felt prudent to stiffen things up so much. But, I was wallowing a bit into the corners on twisties before; today things seemed nice and stable.

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raYzerman
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Re: Front end vibration. Forks wiggling at high speeds.

Post by raYzerman » Sun Feb 09, 2020 10:05 pm

The .95's are good for your weight, you're using a little heavier fork oil, the 4 clicks of compression seems (to me) a little excessive... is it not harsh on bumps? I would maybe have you back off that 4 clicks of compression to say 6 or 7, I don't know anyone who runs it at 4 (maybe for the track?).... dial in the preload another two lines, leave rebound at 7. Really what should be done is to take some sag measurements.
The plushest ride is where you have the least amount of damping that still gets the damping job done... however, if you do track days, you'll perhaps have a preference for stiffer...... all good, and take some time to try it and tweak it in over a summer with the various riding conditions.
I will also suggest you are partly influenced by the great compromise shock on the rear end, possibly making you think the front end is inadequate (it isn't). I'd dial in the rear shock to 6 clicks out of rebound. If you like stiffer you might want 5. But nothing truly fixed it until my RaceTech shock got transferred onto that bike.
Keep yer stick on the ice........... (Red Green)
Duct tape can't fix stupid, but it can sure muffle the sound.

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