Is it ok to run a 45 series tire on a e53
 

Does anyone know if it ok to run a 45 series tire on a 4.4l e53 . And what is the smallest tire possible without getting an error or break something like a transfer case?

I think the guidelines for tire selection go like this:

Will it fit on the rim and not lose the bead?

if yes, then:

Are all four tires the same outer diameter (to avoid aforementioned transfer case/ differential damage)?

if yes, then:

Will you be making obscenely high RPMs because a really small outer diameter does not go well with your gearing and final drive ratio (which for 4.4 is 3.94, I believe).

To answer the last one, find a tire size calculator you like. There are plenty that will tell you the revolutions of the old tire and the revs of your potential new tire based on the difference in tire measurements.

Someone else will have to chime in on if your speedo will be off or not. On old school trucks that had a mechanical gear off an axle or something, the speedo would be incorrect. I don't remember how E53s get speedo info...it's probably from the ECU though so it could be fine. You will need to check that out.

Speedo will be off. They are like motorcycles set to display high. There is a great tire size calculator online app you can calculate the additional error. If you cHange all tires to a different size the car will not know it will just think you are going a different speed.

You can instantly introduce instant problems when you change tire width by changing the center of lift: you will flip which way the bearing is stressed and could instantly have 4 bad bearings. (Ask me how I know)


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My stock tires are 29" on 18" rims I have 19s now with a 275/45/19 and a 245/50/19 in the front . And it's ok but it's to much tire for my taste. I want to go to a 295/40/ and a 235/45 .

Sorry a 235/50 witch both are 28.3 " would this be ok

You think it's too much tire...
Because you're thinking of how smaller diameter tires look on a sedan;
But the X5 is not a sedan!

You will hate the look of it an on X5 -
it will look soo out of place -
like a bloated elephant with tiny feet::bustingup

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I'm not talking about going to that extreme just from a 29" to 28.3 I just want to know if it's ok . Because the people at discount tire said that I can't because the x5 is to heavy in the front

The X5 above is fitted with the stock e46 M3 CSL 19 inch wheel/ tire combo , it does look extreme on an X5 doesn't it?

The smallest stock diameter for an e53 tire is about 28.7 inches;

Your tire retailer may be concerned about the minimum load rating, 103 or thereabouts;

They may be concerned regarding their own liability,
if they knowingly and willingly fit tires that are undersized and if they don't meet the minimum load rating...

You seem determined,
please post some pics when you have them fitted...