Driveshaft Effect

[nervous]

Don't know if this has been covered but on my ride to work today I flipped on my throttle lock about 65 MPH, sat back and took both hands off the bars. I immediately noticed that the bike had a distinct tendency to want to gently turn left. I was in the right lane so the crown would have actually worked against this. It just required the very lightest throttle side counter steering input to correct and is unnoticeable with both hands on teh bars. My first thought was driveshaft effect or torque steer but having no experience with that I am not sure if that makes sense. If not then I should start looking at some other things.

What do you think?

 

[garyahouse]

If it were driveshaft effect or torque steer, then you'd notice more of a pronounced difference under acceleration than you did on steady cruise or decel. However, that would NOT explain why I've never experienced this on my FJR...

Torque steer was a result of early front drive vehicles with dissimilar length front axles. Not a factor on the FJR.

Driveshaft effect typically causes the rear end to jack up under accel, and visa versa under decel. Mama Yamma did a great job with the FJR's design. This is not much of a factor on the FJR, and dead sure wouldn't cause what you're describing.

Check your tire pressures. 41-42 front? Check your front tire wear. More wear on the left? I know that sounds strange, but I've seen this a couple times... that the front tire has a more pronounced flat area on the left side. Why? Who knows. But I've seen it. That would cause the bike to pull left ever so slightly. I assume that with the front wheel in the air, the steering head turns freely. I assume there have been no accidents causing twisted or bent forks??

Gary

darksider #44

 

[Bounce]

What were you doing? Trying to text someone?

 

[MrM0t0]

I experienced the same phenomenon after replacing the squared off OEM tires. I've seen references to it by others but have yet to read an authoritative answer.

 

[gixxerjasen]

Tire wear on the left is an easy one. The road slopes down to the right so that rain water will run off (It's supposed to anyway) and thus when riding straight up and down you are actually more on the left side of your tire.

Go to England and you'll wear down the right side going the other direction.

As for the torque steer, I dunno.

 

[MrM0t0]

My link

I DID find an authoritative answer.

 

[TwilightZone]

>"I DID find an authoritative answer."

Had you re-assembled your forks?

Did you tweak the forks to fix the steering, or is this just something you can live with?

 

[RossKean]

Tire wear on the left is an easy one. The road slopes down to the right so that rain water will run off (It's supposed to anyway) and thus when riding straight up and down you are actually more on the left side of your tire.

Go to England and you'll wear down the right side going the other direction.

As for the torque steer, I dunno.

In addition, consider cornering, especially at intersections. You actually travel further on the left hand turn than on a right hand turn. In addition, because the turning radius is larger, you are typically taking the turn faster. Both these wear out the left side faster.

 

[wmadoty]

Nearly 16,000 mile on my 2010 and it has done this since it was new. I almost always have a hand on the bars so I don't let it worry me much. I just assumed that they all did this and you can not feel it is you have a hand on the bars.

 

[Fred W]

Nope. Not driveshaft effect. Most likely it is fork misalignment. (same link that MrMoto linked to) BTDT

Even if your forks haven't been tweaked by a deer (as mine seem to have) the forks can be twisted in triple clamps causing the same condition. But if you want to be sure you don't have a bent fork, do as I did in the linked post and, with the bike up on the center stand and all weight off the forks, loosen the fork legs in the triple clamps and rotate them 90 degrees at a time and measure how much the axle protrudes from the right fork. It should stay the same as you rotate the fork leg around. Mine didn't.

If your legs check out straight, then just be sure to tighten the clamps in the proper sequence getting everything perfectly straight.

BTW - I did get everything assembled aligned properly (both tubes bent rearward) and she tracks straight as an arrow down the road with no hands on the bars now.

 

[nervous]

Good stuff everyone and thanks. Tire pressures are correct. No I wasn't texting. The tire wear makes sense now. I'll look closer but I don't think I'll see anything dramatic, but it probably wouldn't take much for the slight effect I felt. The other recommendations are a bit more involved and I won't go crazy chasing this ghost down but when I do got to those areas I'll pay a little more attention.

How about another dumb theory: In the thread that was linked someone mentioned that in an older poll that many FJR owners noticed this same thing. Is it possible that the bike might just be slightly heavier on the left side for some reason, perhaps from the engine design or drive train equipment, that would then be perfectly normal?

 

[wfooshee]

It takes a very small amount of ANYTHING being out of perfect alignment to cause a tracking error like that. Uneven tire wear is the most likely culprit, and pretty much unavoidable. Something not exactly straight in the chassis is also a possibility, and that would most likely be fork legs. If somehow your tires don't EXACTLY trail one another, you'll have the tendency to steer with hands off. Back to the tire, though, an unevenly worn tire would be enough to "misalign" the tire tracking.

Also, you said the crown would work the bike the other way, and I'm not sure I agree. Don't know for sure, though. If you're curious, find a mall parking lot late at night and you'll have all kinds of slopes to play with. Just don't hit any lamp posts. That's kind of hard to explain, as my step-daughter can attest.

 

[Road_Runner]

Nope. Not driveshaft effect. Most likely it is fork misalignment. (same link that MrMoto linked to) BTDT

+1 fork misalignment. Had the same problem and fix as Fred W. although on a different cycle (Sprint ST). Mine was bad though, and I was concerned about possible uneven tire wear.

If the FJR I am riding now does not track exactly straight and true, I am at a loss to notice.

 

[Fred W]

Also, you said the crown would work the bike the other way, and I'm not sure I agree. Don't know for sure, though.

I'm sure. It definitely tracks downhill (a little) if the road is crowned or tilted. BTDT. Almost all secondary roads in New England get serious crowning for winter drainage. The bike wants to go to the right.

But I'm not sure that a badly worn tire will cause the steering to pull, although it is a good theory. Reason I'm not sure is that my current front PR2 is a mess right now and the bike still tracks straight (with hands off on a flat road), though it feels and sounds like a buzzsaw around the corners.

Check out the shadow on the floor

The back one isn't any better

Can't wait to get some new sneakers on it.

 

[nervous]

Also, you said the crown would work the bike the other way, and I'm not sure I agree. Don't know for sure, though.

I'm sure. It definitely tracks downhill (a little) if the road is crowned or tilted. BTDT. Almost all secondary roads in New England get serious crowning for winter drainage. The bike wants to go to the right.

But I'm not sure that a badly worn tire will cause the steering to pull, although it is a good theory. Reason I'm not sure is that my current front PR2 is a mess right now and the bike still tracks straight (with hands off on a flat road), though it feels and sounds like a buzzsaw around the corners.

Check out the shadow on the floor

The back one isn't any better

Can't wait to get some new sneakers on it.

I had a front tire on my last Bandit that I took out with low air pressure and it ended up badly cupped. The result of that was a condition that felt like an instant tank-slapper when your hands were removed from the bars. The results can be dramatic.

 

[Fred W]

I had a front tire on my last Bandit that I took out with low air pressure and it ended up badly cupped. The result of that was a condition that felt like an instant tank-slapper when your hands were removed from the bars. The results can be dramatic.

These have never been underinflated. I'm highly conscientious and keep them at 40F 42R.

On second thought, they have been run cold. Very cold. Like, well below freezing cold this past winter, quite a bit. Which probably has the same effect of as under-inflation since they never truly "warm up". Hmmm...

 

[Bokerfork]

If you all will remember, I had a similar problem last year after lubing the rear splines. The OP is on to something with the torque steer. Right part of the bike, wrong effect.

You need to pull the rear drive and make sure the timing marks from the male section of the rear spline are lined up with the timing marks on the female side.

Without these marks properly lined up you will get what we around these parts call "The Obama Effect", i.e. damn thing goes left no matter what the input.

I got so tired of Old Michael nudging me toward the double yellow(he has a very light "touch" on the bars)that I tore his rear end apart just to straighten him out._beemerdons_

Mark

 

[LAF]

If you all will remember, I had a similar problem last year after lubing the rear splines. The OP is on to something with the torque steer. Right part of the bike, wrong effect.

You need to pull the rear drive and make sure the timing marks from the male section of the rear spline are lined up with the timing marks on the female side.

Without these marks properly lined up you will get what we around these parts call "The Obama Effect", i.e. damn thing goes left no matter what the input.

I got so tired of Old Michael nudging me toward the double yellow(he has a very light "touch" on the bars)that I tore his rear end apart just to straighten him out._beemerdons_

Mark

I have seen this debate on alining shafts when I owned a K 1200 LT BMW. As endless as a good ole oil debate.

When I did my 0 mile 10, I can not tell you if it is alined or not when I put it back in? Mine runs pretty strait.

I am a firm believer in that when I did my fork springs, and when I did my MCL triple tree, and anytime I take the front wheel on and off to bounce all components well before torque. It seems to settle or set, and just feels right to do it that way. Perhaps learning old school checking "fall away" on Harleys?

I see this as tire wear, tire balance, of weighted saddle bags/load, or maybe posture sitting the bike?

 

[gumba]

Read Dave Searle's evaluation of Motion Pro's Fork Tru jig in Dec. issue of MCN. In the article Dave wrote that even though he had given a lot of thought to front wheel/axle placement, the jig pointed to his forks being out of parallel. He suggests the 4 lower triple clamp pinch bolts be torqued first. I tried it and it worked for me. Not only does my scoot track true, but stiction is gone as is the dreaded 45 mph head-shake. I bought the tool but haven't used it yet.