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[oobflyer]

Semantics? Not sure what the difference is between pulsating, vibrating, shaking, etc. When I brake I feel the front wheel shake  or vibrate or pulsate; pick your verb  ;-)
I got the email reply from the dealership - recommending that I bring it in for them to check it out - I'll tell them about the steering head on SCalpeL' bike.

[Richard230]

I consider "pulsating" to be what you feel when your brake disc is warped or has a "hot" spot on the surface.  When you come to a stop, the braking seems to come on and off (like your regen when the battery pack is full) with the rotation of the wheel.  But "vibrating" would be a fast shaking like you get from an IC engine when it is running.  Needless to say, your dealer was right to suggest that you bring the bike in for inspection as braking performance issues would be a real concern to both the Zero designers and the component manufacturers, since the 2015 models have a new front brake system manufacturer with ABS.

I wonder if the vibration could be the ABS system malfunctioning?  On some motorcycles with ABS it doesn't take much to activate the system and when the ABS is activated you can feel a rapid pulsating or vibration through the brake lever or foot pedal.  It could be that the ABS is improperly programed and is activating too soon.

[CScalpeL]

Alright, so I did another couple of runs. I tried sport mode which as expected yielded the same results and I tried some android based GPS speedo apps (speedview, G-FORCE) but they were crap... I was at 100 km/h and they were still showing 40.

I did however compare my acceleration graphs with those of this guy Omar (happens to be from Israel too) that posted on youtube () doing a similar test with his 2014 SR.

Despite the fact that I don't know Omar's weight, there are still some things that I (think I) learned from this. My bike's acceleration is entirely linear while Omar has a much steeper acceleration in the first second which then levels out and follows the same slope as my acceleration graph after the first 1.5 secs. I think this would negate the possibility of rolling resistance being the cause since this should adversely affect my slope throughout the run. It would also negate the possibility of field weakening issues in the motor since I would expect to see a slope decrease at higher speeds. I did notice that there is a difference in the sound his bike makes in those first couple of seconds (before the wind drowns it out), you only hear the whine of the belt. On my bike I'm hearing a sort of fluctuating metallic/ceramic grinding noise where the frequency of the fluctuation (not the noise itself) increases with speed (don't hear it under light acceleration only when I give a full twist). Anyone familiar with this? Could it be a bearing in the motor under load? Any chance it is related to the lower performance?

BTW - my front brake would vibrate at high speeds and pulsate at lower ones, to the point where it was almost embarrassing to use the front brake to stop at a light since I would bob back and forth so much while stopping

[Richard230]

Your brake issue sounds like a warped rotor. 

[Doug S]

If the calculator doesn't consider gearing then its output is not going to be very useful.

Those calculators assume ideal setup of the vehicle (including gearing), with little if any wheelspin, perfect carburetion and perfect driver performance. The whole point of the calculators is that if you're not coming close to the performance they indicate, there's something wrong with the vehicle's setup or your driving.

[francesco]

I did notice that there is a difference in the sound his bike makes in those first couple of seconds (before the wind drowns it out), you only hear the whine of the belt. On my bike I'm hearing a sort of fluctuating metallic/ceramic grinding noise where the frequency of the fluctuation (not the noise itself) increases with speed (don't hear it under light acceleration only when I give a full twist). Anyone familiar with this? Could it be a bearing in the motor under load? Any chance it is related to the lower performance?

This describes very well what I hear as well (2015 S 9.4). At first I thought it was the belt being too tight and "ringing", but it doesn't seem to be the case.
I never heard it on the 2012 S; I thought it appeared in the 2015 because of the higher torque, but, as you point out, it doesn't seem to happen for the 2014 models...

[CScalpeL]

Your brake issue sounds like a warped rotor. 

That's what the mech thought at first but after swapping rotors without improvement, he tightened the huge nut on the steering head and that greatly improved it

This describes very well what I hear as well (2015 S 9.4). At first I thought it was the belt being too tight and "ringing", but it doesn't seem to be the case.
I never heard it on the 2012 S; I thought it appeared in the 2015 because of the higher torque, but, as you point out, it doesn't seem to happen for the 2014 models...

Francesco, it would be interesting to see if your bike's performance deviates greatly from the spec (after taking into account your weight)... Can you try measuring your 0-100km/h times? I attached the sound track from one of the runs, let me know if it is indeed identical to what you are hearing

[Richard230]

Now I recall that some years ago the steering stem preload loosened on my BMW Funduro and the steering would shake and vibrate as I braked to a stop.  Tightening the preload on the bearing made that problem go away.  In any case, it is a good idea to have the steering bearings properly tensioned.  That will make the bike handle much better around bumpy corners too and reduce the chance of a speed wobble when braking or hitting a large bump.

[francesco]

Francesco, it would be interesting to see if your bike's performance deviates greatly from the spec (after taking into account your weight)... Can you try measuring your 0-100km/h times? I attached the sound track from one of the runs, let me know if it is indeed identical to what you are hearing

I don't think it's the same "feature". The noise I hear is lower pitch and lasts less, more like the sound of a spring unloading.
I haven't measured performance yet. I'll post here as soon as I get a chance to do it.

[oobflyer]

To follow up on the vibration coming from the front wheel on my SR - I took it to the dealership last weekend - they checked the brakes (rotor), and the steering head bolt, but could not find the cause.
The service manager told me he'd call me after checking with Zero.
I'll be bringing the bike back to the dealership once they make the diagnosis.
Meanwhile - the mechanic assured me that it was safe to ride.

So I put another 250 miles on it 

[oobflyer]

My dealership called last week to say they had received the information from Zero on what to do to fix the vibration coming from the front while braking.
It was the steering head bearings that needed adjustment.
I took it back today - they worked on it for a couple of hours - and it's better, not completely better, but better. The loud 'clunk' that accompanied the vibration (while braking) stopped completely, but the vibration is still there when applying the front brakes.
I plan to ride it for another week or so before deciding if it's bad enough to warrent another trip back to the dealership.