Steering ABC's

[QuadManiac]

...[the DPS] can not turn the bar by itself.

and

any corrections taken by the operator seem to be hindered by a locking or stiffness in the steering.... This is no doubt caused by a DPS malfunction, but the initial lane change is not.

Unfortunatley, these two bold statements, upon which the rest of your well though out hypothesis is formed, are just not based upon fact. The DPS IS capable of turning the bar by itself, not necessarily by design, but under some as of yet unknown fault condition. Its final stage is, afterall, just a high torque motor driving the steering shaft. An error in drive signal will turn the shaft readily.

It is also certainly possible that a faulty VSS could cause the bike to pull or jerk in one direction by applying brake selectively; but without further evidence, there is no way to determine, as of yet, which system is causing the initial symptoms.

From all of the anecdotal data that I've read to date (the same that everyone else has) and from my long time engineering expertise in feedback control systems, I'm going to bet that it is the DPS... but without having experienced the failures myself (no, I'm not volunteering to be a guinea pig) and without a whole lot more data, in my opinion it would be presumptious of me, or of anyone else, to suggest an absolute cause.

 

[Way2Fast]

Unfortunatley, these two bold statements, upon which the rest of your well though out hypothesis is formed, are just not based upon fact. The DPS IS capable of turning the bar by itself, not necessarily by design, but under some as of yet unknown fault condition. Its final stage is, afterall, just a high torque motor driving the steering shaft. An error in drive signal will turn the shaft readily.

It is also certainly possible that a faulty VSS could cause the bike to pull or jerk in one direction by applying brake selectively; but without further evidence, there is no way to determine, as of yet, which system is causing the initial symptoms.

From all of the anecdotal data that I've read to date (the same that everyone else has) and from my long time engineering expertise in feedback control systems, I'm going to bet that it is the DPS... but without having experienced the failures myself (no, I'm not volunteering to be a guinea pig) and without a whole lot more data, in my opinion it would be presumptious of me, or of anyone else, to suggest an absolute cause.

While it may be possible for a "runaway" DPS motor to turn the bars by itself with no rider input....how would you explain the bars turning with the DPS disconnected? That is the reason why there HAS to be more to the problem than just the DPS malfunction.

 

[Firefly]

While it may be possible for a "runaway" DPS motor to turn the bars by itself with no rider input....how would you explain the bars turning with the DPS disconnected? That is the reason why there HAS to be more to the problem than just the DPS malfunction.

Hold the phone a sec.....

I have not heard a single report of anyone having steering problems or bars turning with the DPS disconnected.

You have said you believe your DPS has not worked from day one -- this is FAR different than having it disconnected.

If your DPS has power going to it - then there is a very good chance it is at least working intermittently.

In fact, if your DPS had power to it - and you felt it wasn't working -- and then you were having intermittent steering problems--- then there is a great chance the DPS is your smoking gun.

Your 'VSS theory' is based on 100% assumptions.

Now that you have your DPS disconnected - I'll bet good money you won't have any of the steering issues you had before.

Only one way to find out.......

 

[Way2Fast]

Hold the phone a sec.....

I have not heard a single report of anyone having steering problems or bars turning with the DPS disconnected.

You have said you believe your DPS has not worked from day one -- this is FAR different than having it disconnected.

If your DPS has power going to it - then there is a very good chance it is at least working intermittently.

In fact, if your DPS had power to it - and you felt it wasn't working -- and then you were having intermittent steering problems--- then there is a great chance the DPS is your smoking gun.

Your 'VSS theory' is based on 100% assumptions.

Now that you have your DPS disconnected - I'll bet good money you won't have any of the steering issues you had before.

Only one way to find out.......

There was an account posted on this forum where a rider was riding along with a BRP tech when he experienced the steering problems. The tech pulled the fuses and the problem didn't go away....not until he disconnected something under the vehicle...the post writer didn't know what it was. I'm recalling this post from memory, it would take a LOT of time to try and locate it among all the threads on the subject.

 

[Firefly]

There was an account posted on this forum where a rider was riding along with a BRP tech when he experienced the steering problems. The tech pulled the fuses and the problem didn't go away....not until he disconnected something under the vehicle...the post writer didn't know what it was. I'm recalling this post from memory, it would take a LOT of time to try and locate it among all the threads on the subject.

I do remember that post--- and the person didn't get into the tech side of what was really done--- it was a pretty vague post.

My impression was that the tech had pulled the front fuse --- then went for a ride and forgot about the other fuse - and then unplugged that or directly unplugged the DPS. The person never followed up on what the tech did --- but it's a really good chance it had to do with the DPS --- not the VSS as you cannot just 'unplug' the VSS.

 

[Longlegs]

I thought of something else I tried while mine was acting up; I tried hitting the brakes as well as shifting gears and niether one changed the feeling of the steering being locked. Just more food for thought.