what is a good ground?

[solitz]

also try to keep earths as SHORT as possible

very very true on this front

[aaronng]

sorry but you are not right on this coz the threads is never had a good contact with the terminal, usually the terminal hole is slightly wider so you can put the bolt in, so if dont scrap the paint the terminal is still sitting on the paint, so YES you better scrap the paint but dont FORGET to put some touch up paint after that, so you wont have any problem with rust.

So scrape paint off and then put touch up paint back on?
Even if you put touchup paint around the terminal so that any exposed metal is covered, the sanded part that is under the terminal can rust if it is humid.

[narchi]

but Electronic corrosion control then. done.

[EuroDude]

What you do is scrape the paint off from around the chassis bolt hole, then bolt down the ground cable's ring terminal so the terminal touches the chassis, then paint over the Bolt and Terminal so air/humidity cannot reach the exposed metal and cause rust. If the bolt goes straight through the chassis, you may need to paint the other side so air cant find its way in.

[aka_NSX]

So scrape paint off and then put touch up paint back on?
Even if you put touchup paint around the terminal so that any exposed metal is covered, the sanded part that is under the terminal can rust if it is humid.

oh well thats IMO, and I never had any problem with all the car I have done