Front end vibration

[sonny8l3]

Hello, I get a vibration or shimmy or bounce in the front end sometime. It seems to have something to do with the road surface maybe. I have an '84 Yamaha 1000 front end. I've had the trike about 3 years, about 30k. It has not gotten better or worse. I'm wondering if this is common for vw's? Thanks for your time,

[peteg59]

If you don't think its pavement related, it could be something as simple as tire pressures. Not sure what is recommended for the size tires your running but as a rule: higher pressure in front, lower in the rear.

Just an example: I'm running 38psi out front in a bias ply M/C tire, & 22psi in the rear radial car tires. It seems to handle well with those pressures.

If you do a search on tire pressures in advanced search above, you'll find previous discussions on this very subject.

Unfortunately there are other variables that might need looking at, if tire press. adjustments fail...

[DeathBySnuSnu]

A shimmy is common on all motorcycle front ends used on a trike.

The trail is large.

Offset or raked trees. Progressive springs. Oil weight change. Tightening the neck bearings. Playing with tire pressures. All help.

Rule out everything else before any real change.

Check fork oil and seals.

Check neck bearings.

Check wheel bearings.

Then measure the trail.

[Sidecarbill]

Well judging from that picture, your front forks don't look like they're using much more than a inch an half of travel. Vws set up like yours don't usually have much weight on the front wheel. I have xr 80 fork springs and never run more than 15 lbs of air in the front tire. My front tire is a 500x16. You should be using that inch and half travel just sitting down on the bike.

[Loner]

Statements above are all in line to identify contributing possibilities. May I recommend one shortcut action that you might try to help lead you in a proper direction for diagnosis. Tighten the fork stem nut on your triple trees to the point of feeling some increased resistance (but not so much as to make it hard to steer). Then take a ride to see if the problem changes any. If it seems to be improved, then you know you are working a geometry problem and can proceed down that diagnosis and correction road. Hopefully it will improve and whole matter might be cured by a proper (for trikes) torque of that stem.

As a mention, from my own view when diagnosing front end problems, there are two primary planes of movement for the front tire - vertically straight up and down (bounce), and side to side (shimmy). Vibration is some mix in between these two. The reason I mention this is bounce will generally be attributed to wheel/tire or road variations, while shimmy is usually a problem in fork geometry or other areas of the trike (rear wheels out of balance for example).

If you try this, let us know what you discover (if anything).

[chopptrk]

If tightening the fork stem/neck bearing "nut" helps, then I would have to suggest a steering damper/stabilizer. I've noticed that most older factory bikes that have side cars (trikes?) have some sort of steering stabilizer. Also some factory built trikes use steering dampers. I installed one one my vw trike and liked it so much that I installed another on the other side. Worked great for me.

[sonny8l3]

Thanks y'all. I tightened the neck nut and lowered my front tire to 19lbs. It made a bunch of difference. I think I might try changing the neck bearings, since the fella I bought it from was real short on honesty.

Thanks for your time.

[LarryA]

Sonny just wondering outloud here....could a tubeless tire @ 19# break the bead on a hard cornering situation?? with a tube 19# not a problem? any other opinions here?

[peteg59]

^....x 2 on that Larry.

No matter how well it seems to handle now, I'd be extremely cautious taking corners with only 19psi out front!

[Sidecarbill]

I don't know if his tire is tubeless or not. I've run my front tire at 6lbs and it didn't fall off. Old vw was tubeless, factory manual called for 17 psi front. Old servicar harley was tube type called for 12 lb front. So no recommendation from me. Do what you're comfortable with.

[DaveO98]

If tightening the fork stem/neck bearing "nut" helps, then I would have to suggest a steering damper/stabilizer. I've noticed that most older factory bikes that have side cars (trikes?) have some sort of steering stabilizer. Also some factory built trikes use steering dampers. I installed one one my vw trike and liked it so much that I installed another on the other side. Worked great for me.

This may sound like a dumb question. But do the stabilizers limit your steering radius, or make it more difficult to turn?

[LarryA]

Dave I have not ever used a steering stabilizer, but I think they just dampen or slow down a quick road input that could become an oscillation if not damped. The stabilizer should have enough travel to allow full steering travel. I would assume the stabilizer would add a small amount of resistance to the steering effort. I'm sure many stabilizers have been added to cover up problems coming from worn parts, loose parts bad tires etc. Just guessing here but, I think some mfg's may add them to prevent shimmy as their products wear. No mfg wants their product to get a bad reputation!



design factors can also contribute to shimmy....but my knowledge of that stops here! good luck

[chopptrk]

This may sound like a dumb question. But do the stabilizers limit your steering radius, or make it more difficult to turn?

Hey Dave, good question. If mounted correctly, it will not limit turning radius. Hard (for me) to explain but the angle of attachment needs to insure you keep the full range of movement. Also I guess it's a lil stiffer but not difficult to turn what so ever. Hope this helped.