Rim newbie with REALLY basic question

[taintedsaint]

At age 50, I've always pretty much stuck with factory rims except for my restomod 68 Deville and a couple others. I've got a '91 735iL which is just exceptional. Beautiful black car. Of course, 15" wheels are tough to find really good tires for so I've got some new Coopers on for now.
SO, I'm looking at wheels, considering going to a 17" or 18" with tire size adjusted to keep same overall diameter as original.
When I'm looking at factory wheels, I see listings like "18x8 ET 13". I understand 18x8 obviously but what is ET13? Assuming they are all 5 x120 lug pattern?
Nearby friend has set of new in box M Parallels in the size mentioned above and want to know if they'll fit and tuck in fender well like stock. Not interested in "stanced" wheels.

Thanks to all for helping an old idiot.

Joe

[Mless5]

Hi Joe,

ET means offset, usually measure in mms - basically how far the rim will stick out (or not) in relationship to the hub. You want to make sure you are buying rims of the same or very close offset, otherwise you are risking not clearing the caliper or rims sticking out too far out (may cause tire to rub on fender lips). I don't think you would want to go any larger than 17" on that car really.

http://www.bmwe34.net/E34main/Upgrad...ls_upgrade.htm

[taintedsaint]

Thanks so very much Mless5. I have a really good understanding of offset, my Deville wheels were a nightmare finding a good offset. Also, thanks for the guidance on 17". I really didn't know what to go to. I'm certainly NOT looking to look like a baller, not my style. Trying to increase tire choices going forward. Appreciate the input.