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Tire Size - 540i-6 MTech - 285 30-18??

15K views 17 replies 13 participants last post by  wopkevanos 
#1 ·
I have a 2003 540i M-Tech. It has the staggered rims with the 265 35-18 tires on the rear and the 235 40-18 tires on the front. (Not being able to rotate your tires really shortens their life, but hey, if I was looking for functional and efficient, I wouldn't be driving this car.)

I need rear tires and I have run across a new set of 285 30-18's that a friend has and they would be almost free. The only question is, will they work on this car with these rims? Any comments would be appreciated.
 
#2 · (Edited)
The only way to know is to mount them. The rear tires are spec'ed at 255/40. Check the sticker on the driver's door.

BTW, the wheels were staggered to appease the lawyers, which allows for mild understeer, something neophyte drivers can handle.
 
#3 ·
I just checked and they are actually spec'd at 265 35-18. I attached the pic, but I haven't posted a pic before, so I'm not sure if it will show up. Maybe the spec changed somewhere down the line?

I just can't get a feel for how much larger we are talking about. I suppose I could have them mounted and see for myself, but I was hoping someone would chime in and say they have done this, successfully or not. I appreciate the reply.
 

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#5 ·
Right, stock size got increased for the 2003s. I discovered this during the latest outburst of boasting on this forum about how rare the 2003 M-Sport is. (j/k guys)

OP, seems to me you'd have way too much stagger front to back, and hurt handling. Plus I'm assuming you'd be mixing tire brands, right? Also not recommended.

But if you really want to do it, just check to see if you've got an extra 20mm width clearance now. That translates to a little over 3/4 of inch.

And do that tire circumference equation, to make sure you're not changing the overall size of the wheel and tire too much. Easily findable via search.
 
#9 ·
The 17" front rims on my 2003 530i are toast, so I got a set of 4 replica style 29 wheels.

18 x 8.5" +15 Offset Front
18 x 9.5" +25 Offset Rear
74.1mm center bore
5x120 Bolt Pattern

I see your tire sizes for the 540i 18" wheels, but I was wondering how wide those rims are.

I checked tirerack.com using my car's model and the rim size I mentioned above. The website recommended 275/35/18 rear and 245/40/18 front.

Does that seem correct to you? If not, what size do you recommend?

Are all of the tires directional, or can you get a set that can be rotated from side to side?
 
#11 ·
TX530i I am not sure who you were asking about their wheels. What are you trying to accomplish with the tires? Big as you can get on the rears without rubbing or just reasonable tires that fit?

The tire rack size recommendations are not wrong, but you have more options.

Here is some info that may somewhat helpful. Keep in mind your wheels sizes are slightly different dimensions than these combos, but your offsets are different too which may cancel out any width differences. I am not great at doing those offset calculations so I can't say for sure. Anyway here are some OEM setups

2003 540i Sport came with style 37 wheels
  • 18x8 et 20 Front with 235/40/18
  • 18x9 et 24 Rear with 265/35/18

M5 came with style 65 wheels
  • 18x8 et 20 Front with 245/40/18
  • 18x9.5 et 22 Rear with 275/35/18
Also a lot of people put style 37 wheels from an e38 on their e39s as the e38 style 37 wheels are more plentiful. The e38 wheels are
  • 18x8 et 13 Front (not sure what size fronts people run with these)
  • 18x9.5 et 25 Rear (275/35/18 or 265/35/18 are both popular sizes)

Actual Tire Size Variation
fyi if you are unaware, the tire rack is a good resource because they list actual measurements for almost every single tire they sell. Actual tire width can vary greatly from tire to tire and from manufacturer to manufacturer. Look at the tread width and section width numbers when you are comparing tires.

Alternate Sizes
As you probably know you can run slightly different sizes than the ones listed above depending on what you are trying to accomplish. You just need to make sure you stay within the min/max wheel width for the tire size. And use a tire size calculator to make sure you are staying with a 3% difference from new size to old. 1010 tires calculator lets you compare up to four size to your original size.

If it is of any help I recently upgraded my 530i sport from 17" to 18" wheels (OEM style 37) and I considered the following Rear tire sizes
  • 245/40/18
  • 255/35/18
  • 255/40/18 (Tire size calculator said this was just barely under the acceptable limit)
  • 265/35/18

As far as larger tires go, some people run 285s in the rear and report no to minimal rubbing, but I think those people all at least had rolled fenders. Keep in mind the M5 had rolled fenders from the factory and the rear M5 wheel liners are shaped differently to accommodate the larger tires without rubbing.

So if you are going to run 275 or larger you will probably need to roll your fenders. And depending on your suspension and/or whether you carry people in the back of your car you may get slight rubbing from the wheel liners depending on the specific tire.

Square
Also did you already receive and open the wheels? Unless you want the staggered look I would think about buying a set of four identical wheels so you can have four identical tires (square setup) rotate your tires. Finding a set of 9" wide wheels would probably be ideal. But if you really like the wheels you have you could buy four fronts or four rears of the replica 29 wheels.

Although if you buy four front replica 29s you would be limited to 255 max as they are 8.5" wheels and a 265 is going to need at least a 9" wheel.

And if you have four 9.5" rims you may have to run a spacer to clear the strut upfront depending on the offset and tire sizes. For example I know a bunch of the M5 guys run square 275s need 3mm-5mm spacers up front. I don't know if the hub to strut distances are the same for the non M cars, so you might have more or less space than the M5 guys. Also the replica 29s offset is slightly different so that may may help you(but my offset math could be wrong).

Rotation
Some of the tires might not be directional, but double check that those non directional tires do not have a specific inside and outside edge tire tread pattern. Unless I am confusing myself, if they have a specific inside and outside edge then rotating them side to side is not going to do any good. As the inside edge is still going to be on the inside and therefore the negative camber is still going to wear the inside edge of the rears faster than the outside edge.
 
#12 · (Edited)
Lots of tires are asymmetrical -- i.e. not directional. Note if you go directional AND staggered, you can never rotate tires at all. If rotation is a goal, you should not have purchased staggered wheel sizes.

Three quick thoughts:

1. Style 37s are beautiful wheels on the E39.

2. As Solo shows, there is a lot of detail to master before making your decision. You've handcuffed your tire choice somewhat by the wheels you've purchased. Make sure you find the wheel circumference calculator and observe the 3% rule.

3. On what other board would someone get answers so quickly on a 4 year old thread? The BimmerFest E39 group is outstanding.
 
#13 ·
I appreciate everyone's help.

I wanted to go square, but I really like the look of the wider rear tire.

Thank you for the online calculator recommendation. I used it to match the size of my tires to the 2003 540i. The tires are the exact same height. Since my rims are .5" wider, the tires are .4" wider.

I was able to find non-directional tires on another thread that were recommended by a number of people. They also have a good rating on Tire Rack. I figure side-to-side rotation is better than nothing.

I bought Sumitomo HRTZ III tires - 245/40/18 front & 275/35/18 rear.

Thank you again for the help.
 
#18 · (Edited)
I have done some research on maximum tire size, and decided which I wanted to buy for my E39 540i Touring. I had 17" BBS 245 cm square, but replaced them with an Alpina 18" wide set. Many forums argue that 275s will rub, but I think I figured it out.

The M models are built with rolled fenders. By factory they support wider wheels than all other E39s. I would not recommend rolling fenders yourself because it will leave small cracks in your paint which will lead to corrosion.
By looking at pictures all others that remark rubbing drive E39 sedans, but not the tourings. they have a larger rear side compared to sedan's. So I assumed the wheel wells are also slightly larger. I decided to take my chances and ordered



Michelin, Pilot Sport 4
245/40 ZR18 (97Y) XL
275/35 ZR18 (99Y) XL


After installing we put the hydraulic air suspension on the lowest position and it showed sufficient clearance. Look at that...
 

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