Rear cargo spare location only takes a 17" I think... anything much bigger fouls the cover...

All e53 wheels have the same rolling diameter, so no problem going up in rim size. Tire widths of 235 or less will certainly fit as that's what the stock full size spare was (I misspoke earlier when I wrote 255).

The IS models with bigger brakes came with a 19" compact (thin) alloy spare, which is what I bought of eBay after converting to the bigger IS brakes on my 3.0mt. But, any 18" or larger wheel with the correct hub bore, bolt pattern, and offset that takes a 235 width tire will work fine.

I read that an 18" will fit BUT only if no wheel weights as the space was too tight, hence a 19" would be better.

So I will try to look for 19"x 8.5 or 8.0" (8.0" width should easily hold the 235mm wide tire and give clearance over calipers), 40mm offset (or less to ensure caliper clearance), 72.54mm bore diam wheel with
235/55R19.

https://tiresize.com/comparison/

https://www.tyresizecalculator.com/t...dth-calculator

Hope tihs helps others who are looking to replace or install a spare wheel in the spare area and have it still fit both that and over the 4.8iS calipers.

I have a 4.8is and I keep one rear tire in my garage ready to go. If I had an unrepairable flat, I could give someone the access code and they could fedex it to me (or drive to meet me if close enough). Near home, I can have the vehicle towed to the tire shop and use my spare. I do it this way because it often takes several days to get a rear tire (and weekends/holidays are a further delay) so I have something. I suppose on a longer road trip I could just toss that tire in the back. Fronts seem to be easier to find quickly so I haven’t done that.

14thBMW, thats fair, but I want to put a spare INTO my x5, hidden away in the same spot the spare is now, so I have it at all times.

Put a 17" wheel and tire in the spare spot. The important thing is to make sure you use the tire called out on the door pillar sticker. That way it should match the rolling circumference of your 20's. You won't screw up your differential or transfer case that way.

I think the key thing to do is a trial fit to be sure it will clear the brakes. A 17in regular wheel won’t clear them on my 4.8is. A donut spare would only get you to a place where you’d have to wait for the right size tire to come in since it seems no one stocks them. There aren’t really a lot of good options for the big-brake variants.

Physically I could leave my factory 17" wheel and tire in spare's spot but that is useless to me as my 4.4i (with factory 17" spare) now has 4.8IS brake calipers and associated bits up front so a 17" will not fit over the bigger front calipers. So I need(ed) to buy a 235/55R19 tire as that's the same dimension as the spare in vehicle currently (see my post above comparing the 17" and 19" tire dimensions) BUT I need(ed) to buy a 19" (BMW preferred) wheel which was 8.5" wide, MAX. 8.0" would almost be better honestly (too late now I guess)

I ended up buying a style 332 front wheel (19" x 8.5") and will get a tire fitted on it ASAP before my camping trip this weekend, and then it will fit in spare's spot and be useful for all 4 tires, should any of them have an issue.

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I carry a "shade tree" mechanic's kit for tires when I cross into the empty quarter.
Self tapping sheetmetal screws, plugs, slime and an inflator. Just for tire repairs of tires in the middle of nowhere in addition to my spare.

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I also have one of these in each vehicle:
Stop and Go International 6000 repair kits.

https://www.amazon.ca/dp/B0068FX3VO/..._wqcnFbPF7CDCG

But a few years ago, on a trip, I got a HUGE nail in rear tire sidewall so it wasn't even repairable so the spare was used then.
It's amazing. Kinda costly but wrapped up neatly and worked perfectly.

So I still need a spare that will fit any wheel hub in those crappy cases.

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