[Mtl128_25]

Hi guys,

I have a 2018 230xi convertible with the sports package (blue calipers) and bought 235 40 18 tires and started having flat tire since the roads here have lots of holes.

I will sell these tires and wanted to put the 17 inches instead. Can i go with a 225 50 17 or even a 225 55 17 tire? I want the thickest sidewall possible. Thanks alot for your help!

[gosi]

If you change sidewall size, your speedo will read wrong. Also your back and front diameters need to be within about 1% because of xdrive

[Mtl128_25]

Im not too worried about the speedo but so I can install the 205 55 17s on all 4?

[dradernh]

Originally Posted by Mtl128_25

Im not too worried about the speedo but so I can install the 205 55 17s on all 4?

In a 205 tire, 205/50-17 is the correct size for our cars.

The diameter of a 205/55-17 tire is about 1.0" greater than the diameters of the tires BMW put on our cars. Maybe they'll fit and not rub, but I'm guessing not. Maybe another forum member knows if 25.9" tires work on our cars.

[gosi]

Why are you looking to install a 205 tire anyway? Why not go with 225 or more?

[Mtl128_25]

So i could do 225 55 17?

[dradernh]

Originally Posted by Mtl128_25

So i could do 225 55 17?

Probably not. The tires BMW puts on our cars are right around 25.0" in diameter. A 225/55-17 tire is around 26.7" in diameter.

[Mtl128_25]

Can i put 205 55 16 then?

[dradernh]

Originally Posted by Mtl128_25

Can i put 205 55 16 then?

Are the calipers below the ones you have (if so, my understanding is that there aren't any 16" wheels that will fit over the calipers)? You can always try Tire Rack for advice on both tires and wheels.

[Mtl128_25]

Yeah they are with the blue calipers. Is my 23xi considered the m sport or track handling edition in this case?

[dradernh]

Originally Posted by Mtl128_25

Yeah they are with the blue calipers. Is my 23xi considered the m sport or track handling edition in this case?

I don't know; other forum members on the General Forum subforum might know: https://www.2addicts.com/forums/forumdisplay.php?f=446. You could try asking there.

[Mtl128_25]

I just had another bump on the side of my tire. I need to increase the size of my sidewall. Would the 205 55 16 work with my car (blue calipers)?

Thanks

[sethwas]

why not stick with the OEM 17" size if you are dropping from 18".
You will get more tire options there, and you can choose one that doesn't have the bulge issue.

[Mtl128_25]

Originally Posted by sethwas

why not stick with the OEM 17" size if you are dropping from 18".
You will get more tire options there, and you can choose one that doesn't have the bulge issue.

There are too many pot holes here. So i wanted to reduce the wheel size and increase the sidewall of the RFT tire. I still wanted to keep runflats since i have the convertible variant and dont have place in my trunk to put a tire and other daily stuff.

[Maynard]

Runflats are reportedly much more prone to bubbles and blowouts/sidewall failures, so that may be a big part of the problem. You may also want to re-examine your collision-avoidance tactics and drop speed a bit on those roads. Down here you can also get replacement coverage for road-hazard damage (at the better/larger places), and that would be worthwhile if available. And don't buy tires at a supercheap e-warehouse, Costco, Walmart, etc. (they cut costs by skipping QC or altering composition slightly, some are even selling seconds).

BMW totally confused e/b with the m-sport vs sport brakes vs track pkg nomenclature - even the parts suppliers get confused. They made different sizes of the 'blue brakes' (the rotor diameter is what matters, but the calipers don't interchange either) - I think you can get some 17" over the 340mm rotors; I have the BBK with 370mm rotors and they won't fit a 17. You might call Tire Rack with your VIN and ask them, or perhaps even the dealer can tell you (they might have a set of 17s they could test fit for you if you ask nice - those are common take-offs).

[Expert@ApexWheels]

Originally Posted by Maynard

BMW totally confused e/b with the m-sport vs sport brakes vs track pkg nomenclature - even the parts suppliers get confused. They made different sizes of the 'blue brakes' (the rotor diameter is what matters, but the calipers don't interchange either) - I think you can get some 17" over the 340mm rotors; I have the BBK with 370mm rotors and they won't fit a 17. You might call Tire Rack with your VIN and ask them, or perhaps even the dealer can tell you (they might have a set of 17s they could test fit for you if you ask nice - those are common take-offs).

This is a good resource for learning more about the various brake options that the guys at bimmerworld put out:
https://www.bimmerworld.com/About-Us...t-Brakes/#228i

From what I know, our 17" wheels don't clear the 370mm brake kits for these cars and I haven't heard of any others that do.

-Tom

[msej449]

@Mtl128_25 If it helps, these are Alutec Wolfrace Drive 7.5Jx17 wheels, carrying 225/45 R17 94V XL Pirelli runflat tires on my M Performance Brake M235i 2016.



I appreciate you're trying to get a tall a sidewall as possible, so 45% aspect ratio may not work for you.
225/45 = 45% of 225mm = 101.25mm = 4"

The earlier post was quoting 225/50 = 50% of 225mm = 112.5mm = 4.4" but that's for a 'non-standard' size that may well rub i.e. not be practical. It's certainly not a 17" size you'll find available from BMW i.e. not certified by them.

205/55 = 55% 0f 205mm = 112.75mm = 4.4" so this standard size gives you the same sidewall height as the non-standard one above. Albeit that the 205 is a narrower tire than the 225 of course. All to do with this being a ratio, not an absolute.

And for completeness, your existing tyres are 235/40 = 40% of 235mm = 94mm = 3.7" - So the standard winter size of 205/55 would give you an extra 0.7" or 11/16" or 18mm approx.

[Caveat: you need to check my arithmetic on this! I was remedial math at junior school.]

As regards runflats vs non, I'm with you on keeping to them, since I had damage to a sidewall on my previous 3 Series and the runflats let me drive home and get to the garage next day.

[Maynard]

Easiest way to do sidewall math is overall diameter=wheel size/2 (25-17/2=4inches, or 3.5 for 18" wheels). So if you stick w/ stock diameter, only the ratio changes w/ wider tires, not the actual height of the sidewall. Running physically larger tires is the only way to get more sidewall, and then you will likely have rubbing or fitment problems along w/speedo issues.

[Mtl128_25]

Originally Posted by msej449

@Mtl128_25 If it helps, these are Alutec Wolfrace Drive 7.5Jx17 wheels, carrying 225/45 R17 94V XL Pirelli runflat tires on my M Performance Brake M235i 2016.



I appreciate you're trying to get a tall a sidewall as possible, so 45% aspect ratio may not work for you.
225/45 = 45% of 225mm = 101.25mm = 4"

The earlier post was quoting 225/50 = 50% of 225mm = 112.5mm = 4.4" but that's for a 'non-standard' size that may well rub i.e. not be practical. It's certainly not a 17" size you'll find available from BMW i.e. not certified by them.

205/55 = 55% 0f 205mm = 112.75mm = 4.4" so this standard size gives you the same sidewall height as the non-standard one above. Albeit that the 205 is a narrower tire than the 225 of course. All to do with this being a ratio, not an absolute.

And for completeness, your existing tyres are 235/40 = 40% of 235mm = 94mm = 3.7" - So the standard winter size of 205/55 would give you an extra 0.7" or 11/16" or 18mm approx.

[Caveat: you need to check my arithmetic on this! I was remedial math at junior school.]

As regards runflats vs non, I'm with you on keeping to them, since I had damage to a sidewall on my previous 3 Series and the runflats let me drive home and get to the garage next day.

Thanks alot! Its much appreciated.

I have the same M Performance brakes as yours on my 230XI Cabriolet.

Would the 235 45 17 or 215 50 17 work with my car?

[msej449]

@Mtl128_25 'Would the 235 45 17 or 215 50 17 work with my car?'

Not as a winter setup on my vehicle. I answered this question for my specific VIN using the official BMW shop.bmw.co.uk website which showed me 4 retro-fit options available from BMW.

17" Star Spoke 379: 225/45 R17 91H - Runflat - 7.5Jx17 - OS:43
17" Y Spoke 380: 205/50 R17 89H - Runflat - 7Jx17 - OS:40
18" Double-spoke 385: 225/40 R18 92V - Runflat - 7.5Jx18 - OS:45
18" Radial Spoke 388: 225/40 R18 92V - Runflat - 7.5Jx18 - OS:45

But this is specific to my VIN and geography. You'll have to find the equivalent facility on the US BMW site if you want to get a baseline on what is 'certified' by BMW for your specific vehicle.

Caveat: For me, if BMW doesn't use a particular configuration of width(mm)Jxdiameter(") and tyre xxx/yyy-zz, then I'm not interested. This is partly because in the UK, insurers are strict about 'certified' stuff: if you had an accident and the insurance assessor identified you didn't have a 'certified' retro-fit, your cover could be invalid.