Front end vibration. Forks wiggling at high speeds.

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

Post by FJRoss » Thu Jan 02, 2020 9:03 pm

Hppants wrote:
Thu Jan 02, 2020 7:47 pm
To the OP, what does the front tire look like in terms of wear? Is there even the slightest hint of scalloping or cupping?
I was thinking the same - unless something is broken, front end wobble or shake is usually a bad tire. Scalloped or belt separation. These are usually worst under deceleration, not at higher speed.
I would have a good look at the tire condition but also check steering head torque and make sure the stem nut is tight. I would also check the torque on the top and bottom pinch clamps on the triple tree. As suggested, also check runout on tire and wheel.

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

Post by BruinFJRguy » Sat Jan 11, 2020 8:28 pm

Alright, dudes. My response is a bit overdue. Sorry about that.

So some suggestions can be ruled out; others, I'm not sure. I have yet to investigate further, just been to busy. I have checked in and read the suggestions, though.

1. I don't think the rim is bent. But I'll perform the test.

2. I doubt it's the windscreen. I've used this National V-Stream sport a lot with no issues. I've also used a large Cee Bailey.

3. I have never serviced the head bearing. I suppose it is a good time to do that.

4. It might be the fork alignment. I've had these forks off a couple times to service them. I've torqued the pinch bolts to spec, but only using a random procedure. Basically, I tighten each side, each bolt, up progressively working towards the torque spec, and then I go around and make sure I get clicks on each one individually.

5. I've always taken the wheels off myself to have the tires changed. It's possible I did something wrong this last time, but I suspect the issue is either fork alignment or the head bearing. I've been through several tires and the problem is recent.

6. The tires are brand new Bridgestone T31s. I had a T31 GT on there that was not worn out or close to it. But I needed a new front and after a second attempt with a GT tire I was once again tired of the stiffer sidewall (too harsh a ride). The issue has been similar with both.

I've really not had an issue until I changed out the springs. My spacer setup is not factory, but I think functional. I'm a little uncertain as to if the springs are perfectly centered at the bottom. It is the bottom of the fork legs that seem to bounce fore to aft rapidly.

I guess I'll try disassembling and reassembling the wheel setup and the fork pinch bolts, and go from there.

Thanks for all the input! I'll update as I go. Hopefully I can dig into it soon.

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

Post by BruinFJRguy » Sat Jan 11, 2020 10:20 pm

raYzerman wrote:
Thu Jan 02, 2020 9:30 am
slight imbalance of tires at that speed will reveal itself... how were they balanced, dynamic or static?
... does it make any difference if set on Hard preload?
Dynamic spin balance, I believe. I have my tires installed at Chaparral Motorsports (large online and b&m vendor). They do a lot of tires there. Their balancing is usually spot on.

Doesn't make any difference hard or soft, I don't think.

The vibe really seems like something is shaking in the bottom of the fork legs.

I'm going to try to realign the fork legs and will re-tighten the axle nut and pinch bolts now. Hopefully that does it.

I already disassembled my re-freshened for legs once to try to re-align the springs. Come to think about it, as we discussed before, I did try (unsuccessfully) to slide hammer out one of my lower bushings before deciding they were good until next service... ... Could be I dislodged it... :roll:

Edit: also, for anyone interested, I have the "A" model.

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

Post by Hppants » Sun Jan 12, 2020 10:55 am

OK - now I'll bet a beer that the balancer machine at the store is out of calibration. Try a STATIC balancer, concentrate on being precise (no wind currents, etc), and try it.

My local cycle gear has had a problem with its balancer for years. The machine manufacturer insist that its on calibration, but I've shown them otherwise with the static balancer. The machine guesses the correct amount of weight, but its placement is about 30 degrees off. And you won't notice it until you get to about 75 mph. With a good static balance, I feel NOTHING well past the 3-digit point.

Another thing - it has been my experience that the rim is largely what is off balance, and not the tires. As I change tires, the amount of weight doesn't change, and the placement is always very close to the one prior. My current set of tires was mounted and balanced by a cycle store in Kingston, TN. I had no choice as I had a huge puncture while on the road. He put a ton of weight in all kinds of places, and of course, it's off at high speeds. (sigh)
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Re: Front end vibration. Forks wiggling at high speeds.

Post by NTXFJR » Sun Jan 12, 2020 11:22 am

Dammit, I find myself agreeing with Pants. :D
I have seen "precision" dynamic balancers that were off a bit. The ones that are spot on are great and of course get to the perfect weight placement quickly. I have a static balancer that I use and when I spend a few ocd minutes on a tire, have been able to achieve perfect enough results with a rock steady ride north of a ton (on the track). One of the tricks I do is to store the precision bearings in a ziploc bag away from the humidity or they begin to get a little crusty and not so smooth rolling.
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Re: Front end vibration. Forks wiggling at high speeds.

Post by ionbeam » Sun Jan 12, 2020 11:24 am

BruinFJRguy wrote:
Sat Jan 11, 2020 10:20 pm
...Dynamic spin balance...Doesn't make any difference hard or soft...The vibe really seems like something is shaking in the bottom of the fork legs.

I'm going to try to realign the fork legs and will re-tighten the axle nut and pinch bolts now. Hopefully that does it.

I already disassembled my re-freshened for legs once to try to re-align the springs. Come to think about it, as we discussed before, I did try (unsuccessfully) to slide hammer out one of my lower bushings...
Any interest in asking if someone in your area would be willing to let you try their front wheel just as a diagnostic?
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Re: Front end vibration. Forks wiggling at high speeds.

Post by BruinFJRguy » Sun Jan 12, 2020 12:05 pm

Alright. Well, that makes sense. The tires on my SUV were horribly out of balance when I got them back from a local tire shop. I had actually had tires put on 3 cars of mine, all very close together in time, and they were all out. I do know these things can be inaccurate.

Last night I loosened the middle fork pinch bolts, axle nut, and axle pinch bolts. I compressed the front end a few times to (hopefully) align everything, and tightened according to procedure. I didn't make it out to test but I will today.

If I'm still off, I'll look into getting a static balancer and doing it myself. I can be sufficiently OCD, I think.

Ionbeam, I could do that, but it's a bit of an inconvenience for whoever. I'll try the other method first. Trying another wheel would give me an idea if it's the wheel or the fork legs, though.

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

Post by raYzerman » Sun Jan 12, 2020 12:26 pm

Personal findings... two FJR's '07 and '14, front wheels by themselves horribly out of balance (40-50 grams).... '14 came with 30 grams of clip-on weights from the factory. Recommend balance front wheel by itself, with TPMS sensors if any, install clip-on weights (get the right ones for Yamaha wheels), leave those on permanently. Mount tire and add stick-ons where required (should be minimal).
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Re: Front end vibration. Forks wiggling at high speeds.

Post by Hppants » Sun Jan 12, 2020 12:58 pm

My buddy bought this one:

http://www.marcparnes.com/Yamaha_Motorc ... lancer.htm

It's more expensive than the universal ones on Amazon, but I'm here to say, if you are patient, that puppy is SPOT on.
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Re: Front end vibration. Forks wiggling at high speeds.

Post by ionbeam » Sun Jan 12, 2020 1:12 pm

Hppants wrote:
Sun Jan 12, 2020 12:58 pm
My buddy bought this one:

marcparnes Wheel Balancer

It's more expensive than the universal ones on Amazon, but I'm here to say, if you are patient, that puppy is SPOT on.
I have a balancer on the idea of the Parnes that was made by FJReady, a riding bud and neighbor.

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Don't ever think about spinning the wheel, it will turn forever. Simply turn loose of the wheel and let the heavy spot settle at the bottom. Add weight 180° from the heavy spot, rotate the wheel 90° from the heavy spot and release the wheel. If the weight is right, the wheel won't move. This balancer is also SPOT on.

I have marked the heavy spot of the bare wheel and balanced the wheel without the tire -- like raY. The last 3 front tires have needed no weights.
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Re: Front end vibration. Forks wiggling at high speeds.

Post by Hppants » Sun Jan 12, 2020 1:23 pm

Alan - is that one of the "cheapies", and you and Ray just added the bearings and c-channel abutments (proper word?)?
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Re: Front end vibration. Forks wiggling at high speeds.

Post by ionbeam » Sun Jan 12, 2020 1:37 pm

My balancer was definitely not one of the cheap ones, IIRC, it was around $95. If I'm going to spend some money it might as well go to a friend. FJReady machined them in batches of 5, not for bulk commercial sales so there was nothing to drive the price down. He used ultra low friction skate board bearings. Leave the cone and spring on the rod and hold the rod vertical then drop the wheel on which will somewhat compress the spring. Put the other cone on and drop it into the wheel center then drop down the locking collar and tighten. Turn the wheel vertical and the spring will automatically center and tension the cones. Use the supplied V-blocks to support the rod. Balance as any static balancer but what ever you do -- *don't spin the wheel* the low friction bearings are amazing. The balancer came in a tube with end caps which makes it easy to stow the balancer when done.
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Re: Front end vibration. Forks wiggling at high speeds.

Post by raYzerman » Sun Jan 12, 2020 1:53 pm

Definitely not a cheapie, excellent quality piece! I think I got the last or second last one Ed made. The spring thing is a great idea. I refitted the brackets on my HF balancer so I could set the FJReady one right on (ie, using the HF bearings). Plans in the works to make a couple of supports for the low friction bearings..... I'd like to replace the rather small screws (not metric) in the black clamps with something easier to use, perhaps larger allen heads or a wingnut type... but that's a small nit, it's great as is!
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Re: Front end vibration. Forks wiggling at high speeds.

Post by ionbeam » Sun Jan 12, 2020 1:56 pm

raYzerman wrote:
Sun Jan 12, 2020 1:53 pm
...I think I got the last or second last one Ed made...
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Re: Front end vibration. Forks wiggling at high speeds.

Post by Abercrombie FJR » Sun Jan 12, 2020 10:51 pm

bill lumberg wrote:
Thu Jan 02, 2020 7:05 am
What shield are you running? At that speed, a variety of things can contribute to suspension anomaly. I think you're looking in the most likely area, but not necessarily the only area that could create that symptom. The amount of air you're pushing can affect the very trim of the bike, as you well know.

Following.
Good call. Several years ago I installed a slightly taller Cee Bailey screen on my 2013 for the first time just before leaving home for an FJR rally in LaCrosse. I was running late leaving home so I was hot footing it a little and experienced a crazy vibration or slight wobble. I was less than 10 miles from home and I could've went home to trouble shoot to insure that it was the windshield but I pressed on. When I came home I removed it and never had another problem. It was a shame I loved the Cee Bailey on my gen 2 FJRs but it didn't work for me on the gen 3.
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Re: Front end vibration. Forks wiggling at high speeds.

Post by BruinFJRguy » Tue Jan 14, 2020 1:31 am

Went for a long and fun ride up 38 and 243 into the San Bernardino mountains the other day. The weather was brisk, but the ride was awesome.

I learned (again) i don't prefer front psi at 40+. I find the ride much more pleasant at 37.

Also, the problem is not resolved. It is mostly limited to 85+. It seems the fork legs are vibrating opposite each other, as if the wheel is shaking left to right. One fork bottom moves forward as the other goes back, minimally, many times per second (i.e. fast). I think I need to try the balancer next. Followed by wheel bearing perhaps.
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Re: Front end vibration. Forks wiggling at high speeds.

Post by FJRoss » Tue Jan 14, 2020 8:25 am

Use a dial indicator and check radial and lateral run-out on both the tire and the rim with the wheel mounted on the bike. Wheel might show satisfactory static balance but if a wheel is bent or if a tire is out of round, this can be a big problem that could explain what you are seeing. A dynamic balancer can sometimes pick up a problem that you don't see with a static balancer.

In addition to looking for bulges in the tire, it is very much worthwhile to have a look all around the rim to make sure that the tire is evenly seated. If it isn't, you can break the bead and reseat it. Might even be possible to mostly deflate the tire and bounce it on the floor to seat it more evenly without breaking the bead. (Assumes that the tire itself is not defective)

If the bearings are bad, you can usually tell. With the calipers removed, the wheel should turn easily and very quietly (and for a long time) once you give it a spin. Removed from the bike, the bearings will feel "notchy" if you move them with an index finger.

Check that the axle is not bent and that your fork legs are completely straight. A bent fork could easily cause your issues. Does the bike track straight with little to no steering input?

Edit: Fork bushings seem to be in good shape? Have they been changed?
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Re: Front end vibration. Forks wiggling at high speeds.

Post by raYzerman » Tue Jan 14, 2020 9:22 am

Balancer next....
Inspect tire for runout, bulge. Check for bent brake rotor while you're at it. Can be a simple check while holding a pencil against the tire/rotor/wheel while spinning it on the balancer, pencil will leave a mark on the high spots. If you think it's significant enough, break out the dial indicator. IF brake rotor is out a tad, first spin all the rivets to get rid of road crud, re-check.
Wheel bearings would have to be totally shot/loose, would be noisy... but are captured by axle/spacers. You'll know immediately once you check them with the wheel off. Note the bearings will be pressed (in) against the aluminum spacer, so may seem hard to turn because you're turning both sides at once... may need a tool...
OK, what did you find at this stage........
Gotta talk again about steering head... if never checked, I'll bet money they need attention. While wheel is off (less weight), install axle into forks, push pull to see if you think there's any play in the steering head... if so, retorque (37 first, then 15-18).
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Re: Front end vibration. Forks wiggling at high speeds.

Post by BruinFJRguy » Sun Feb 09, 2020 4:46 pm

Alright. Had the help of a local FJR friend who is a better mechanic than I am. Fortunately, he has both a No Mar and a balancer.

Front wheel is SLIGHTLY out of round. Rim fluctuates 1/8" or so when spinning. The wheel without tire is about 49 grams heavier where the stem goes. I had very heavy metal 90 degree stem on the front. There are lighter weight ones I've learned, but we reverted to a standard rubber straight stem for now. With the wheel remounted, it took just about 42 grams to balance opposite the valve stem. That's a lot of weight. I'm not sure why it takes so much. I don't think it's had that much on there before.

Anyhow, smooth as silk now. The steering head I'm sure could use a service. For now, things are flawless, so I'm not messing with anything.

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

Post by raYzerman » 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.
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