...Oh, and, my 05' Honda Insight does the same but it doesn't automatically restore regen so I do pick up speed... eventually... after a hundred yards of no regen. Which is a bigger problem... I miss out on that lovely downhill recharge
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...Oh, and, my 05' Honda Insight does the same but it doesn't automatically restore regen so I do pick up speed... eventually... after a hundred yards of no regen. Which is a bigger problem... I miss out on that lovely downhill recharge
Sounds like what we have here is nothing more than a loss of traction and therefore inability to maintain the same braking force. ICE cars with ABS will behave the same way. It doesn't matter what causes the loss of traction. That's an argument between the tires and the road. The Roadster's choice is to either lock up the wheels and lose control, or do what it does and reduce braking to maintain control. Decades of ABS experience says the latter is the right choice.
Scotty: "Ye cannot change the laws of physics, Captain"
Ahhh, this explains a similar puzzling behavior I've been seeing several times.
I'm arriving a bit fast towards my driveway and brake medium hard to slow down. Then I hit a bump, always the same bump, and for a very short moment it feels like the brakes don't work at all. Then they bite again and everything's fine.
The moment is very short, a heartbeat maybe, but it's always enough to send a jolt of adrenaline in my body. Think "Oh Sh*t!"
I first thought that my was foot being jerked off the break pedal on the bump, but I made sure to keep the pedal pressed and it was still doing it.
This explanation makes sense. To test it we could check that it does not happen in performance mode (the regen is less there, right?)
Feels like a bug to me. Maybe traction control should not disengage regen if you're braking?
Sounds like a fault.
In order to engage regen - just like engine braking on a conventional car - you have to have your foot off the accelerator/gas.
A bump to one wheel is likely to cause reduced rotation of that wheel, which would indicate to the TC that the powered wheels are spinning too quickly in comparison.
In both cases, why/how would more power be applied to the drive wheels?
Momentary loss of brakes shouldn't increase speed as dramatically as described.
The question is how the car can distinguish between a bump and a patch of ice. Encountering a patch of ice while braking (explicitly or regen) you loose traction, and the only way to keep control of the car is to release the brakes (stop regen) until you regain traction.
The effect of a bump is identical to a patch of ice, so whatever action the car chooses it should work in both situations.
No matter what, regen only applies to the rear wheels. If the rear wheels lift off because of a bump, you will loose regen braking. The question is how long it takes for the car to see it has landed and re-engage regen.
How long do the wheels loose traction because of a bump? How long does it take until regen is re-enabled? The latter should preferably be significantly less than the former.
But, but, if you hit a bump with a front wheel, and this causes TC to shut-off regen to the rear wheels, won't you feel a noticeable decrease of your braking power?
If this is right, I stil don't see how it would be different in a regular car. The regular car TC would start the ABS pumping the brakes and you'd temporarily loose braking power too.
Could it be that the regen on/off/on/off cycle is much slower than the ABS brake on/off/on/off?
Last edited by toutizes; 10-23-2009 at 08:19 PM.
The TC light comes on whenever an issue occurs, it flickers when you go over speed bumps at an anlge or when one wheel hits a sunken manhole cover. Same on regen; it's really quick, 100mS-500mS tops. As soon as traction is restored the light is already out.
For those who've not driven a roadster flat out, the TC has to be experienced. Unlike ICE vehicles where the lag between control and reponse is wide enough to fit a bus through, the TC on the roadster is invisible; on wet, greasy leaves you can floor the accelerator and the car rockets off with the TC light on solid but with the car accelerating wildly; there's no pulseing, juddering, surging, etc. so much power under such fine control; it's a marvel to behold really. Nice job by Drew Baglino and team - Tesla Motors - Engineering
This is why I (and all owners I expect) find the idea of a complaint in this area to be quite incredible.
As has been explaned to me the ABS and TC are separate. TC can be turned off. ABS cannot be turned off. In the case of this complaint, if the driver relied only on the regenerative braking going down a hill, in my opinion, inattentive driving.Originally Posted by toutizes
On the other hand it behooves all Tesla drivers to test and know the limitations of your brakes. Take the time to bed in the brakes. Push the peddle as hard as you can in order to get the ABS to start pulsing. The brakes are powerful but don't be afraid to push hard and don't let the regen braking lull you into a false sense of security. If you are letting the regen braking slow you down, have your foot at the ready in case you need the brakes. Drive safe and use common sense.
It sounds like the TC is already very good, but one could imagine that a car could have a sensor to detect when a wheel doesn't have weight on it, and handle that case differently (fully re-engage as soon as the weight is back on), than if it looses traction even with weight on the wheel. Not sure if that would make sense technically, though.
Last edited by doug; 10-27-2009 at 10:36 AM. Reason: split post
I believe I have experienced this effect. I was slowing down using regen on a wet road and and suddenly felt a sharp surge forward exactly like the car was hit from behind. I quickly looked in the rear view mirror, and the car behind me was too far away to have caused it. I was on a level road, so I can imagine it would be much more pronounced while going downhill.
I've seen the TC light coming on many times when hitting bumps in the road, but only one time felt the push forward during regen in over 6000 miles.
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