Bigphil001

My 03 didn't come with a spare tire and I couldn't find any decent DIY's to add one.

I used this battery cable to extend the ground:

Amazon

Amazon

This terminal, with the wingnut replaced:

Amazon

Amazon

A spare from another W211

Before making any changes this is what my trunk space looked like:



Remove the battery and you will be left with this mount and foam pad:
\

Remove the 3 torx bolts holding in the brack, and transfer it to the right hand side of the trunk space. I have to bend the the tab with the ratchet side slightly out. It should look like this:


Connect the positive terminal, and the terminal you bought along with the cable going from your new terminal to the old ground bolt. I chose to leave the old ground terminal in place incase I ever wanted to switch back to the OEM position for some reason.

Final trunk setup:





Took about 20 minutes to complete and is will worth the peace of mind!

PJmak

Will the tire fit over the calipers?

bbirdwell

Good info. Can you provide some more detail on the storage compartment on the driver's side of the trunk?

Yuille36

I'm positive that the wheel will fit over the caliper, if not then this whole exercise was pointless.

Jones77

Have you done anything about clamping the battery at the base or is the strap the only thing holding it in now? I've been pondering over this and you could probably make some sort of base out of steel or such to emulate OEM. Or change the trunk base to the spare tyre version which looks to be a fair mission.