I just (gulp) had to buy new tires for my 2012 X5. It came with the ridiculously huge 20" wheel package. I decided to go with non-run flats, so I'd like to figure out an 18" or 19" donut to carry with me, at least on road trips. I don't care what car the donut comes from, as long as the diamater works. Can the hive help me pick one?
Bolt pattern is 5x120. Tire sizes are: Front: 275/40-20; Rear: 315/35-20
Two ways to do this.
1. Mathy. Calculate out the tire diameter (275 * 0.4 * 2 /25.4) + 20 = 28.7"
2. non-mathy.
Go to Tire Rack's website, shop for tires by size, punch in one of your tire sizes, pick a random result and click on "specs". It will give the diameter.
Okay, we know the diameter. Finding a donut of the same size is a little more challenging. I'd be looking for vehicles that use the same tire size and carry a donut. Tire Rack does let you search by wheel diameter, which shows you all available sizes for, say, 19" wheels. Then you look for really skinny tires with a high aspect ratio, such as 155/80R19. Check the specs, that's 28.7" diameter.
Finding a wheel that fits in the middle of that is your problem :D
I know people that use a kit meant for the 6 series. The rolling dia is only 26.5 but it isn't something you are going to finish your trip on anyway. The panel lights up like a Christmas tree when it figures out one of tires isn't spinning the right speed as its friends but you can get to a safe spot.
On my x-drive X3 I chose the "2 cans of fix a flat and a small compressor to get me off the highway" route when I got rid of the run flats.
Why not just do what a lot of OEM's are doing? A can or two of fix-a-flat and a small 12v air compressor.
Driven5 said:Why not just do what a lot of OEM's are doing? A can or two of fix-a-flat and a small 12v air compressor.
That's what BMW did on the M5 in 2002. To pick a random example that's at least partly relevant :)
Don't break that transfer case. Its not cheap.
Probably easier to go with the fix-a-flat and air compressor. Off to investigate that now.
Maybe get the BMW mobility set? It has all you need.
Might be cheaper from Tischer BMW (www.getbmwparts.com)
Yep, cheaper at Tischer ... but these things expire and FCP has the lifetime exchange thing.
GeddesB said:
Came here to say this. Plug in the sizes you have and click calculate. It will give you a chart on the right of equivalent sizes. The sizes they give aren't always a flavor that many (or sometimes any) manufacturers make, but if you click on the size it will take you to a list of tires available in that size. If you click and find three, maybe skip that flavor. If you click and find 60, bingo.
You can also choose the compare tab on the left which lets you put in two different sizes. It will show you the difference and also show speedo error (if any).
Slippery said:Yep, cheaper at Tischer ... but these things expire and FCP has the lifetime exchange thing.
I decided to go this route. Picking up from my local dealer on Tuesday!
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