"Clunk" noise upon hard acceleration

[ocspark]

Hi All,

Wonderful place here. I wanted to see if anyone else has come across this problem I've recently noticed. Upon hard acceleration from a stand still, I hear a "clunk" noise. Seems to come from the front wheels. Does it more often on wet roads. Seems as though the torque is too much for the axle/wheels to handle and it skips a little before catching on? It does it with traction control on or off.

TIA

'14 Silver 2LT

 

[Chaconzies]

Yep this is the wheels slipping. The spark has a very torquey motor but stock wheels are less grippy since they are meant to maximize range. As a result from a complete stop if you slam the throttle you'll most likely get a few seconds of wheel slip. This will be more noticeable when tires are wet, cold, or on smoother roads.
To fix you would probably need to buy tires with more traction or just accelerate a bit slower.

 

[StevesWeb]

I get a lot less of this since putting some grippy ContiPro Contact tires on my electric rocket ship.

 

[Nashco]

As mentioned, it's a function of losing traction (wheels start spinning) and instantaneously the motor controller cuts power back (to limit wheel spin). Unfortunately, we have EXTREMELY compliant motor mounts, which don't like this rapid change in torque direction. The CLUNK you hear is the motor bouncing around in the motor mounts, transitioning from one extreme to the other against the mounts. With more time, either better mounts or better controls could have fixed this. Obviously, since it's a nuisance and probably not expected to break things for the vast majority of users, they didn't bother. I fully expect the Bolt EV to learn from these sorts of things, but don't expect the Spark EV to ever have a fix for it, unfortunately. I've thought about making some custom mounts that are stiffer to eliminate this (at the expense of increased NVH during typical driving), but it's pretty low on my list of things to do.

Bryce