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Z4 M40i

Discussing the current generation Z4
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tweeky687
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Z4 M40i

Post by tweeky687 » Thu Jan 23, 2025 6:46 pm

Hi all.
Please be gently on me I`ve just ordered A Z4 M40i for delivery in May.
Can anybody tell my the PCD and the centre bore Diameter.

My current car is an M340I and I`ve two set of wheels for it a set of 19 inch M898`s used for summer and set of 18inch 780 used for winter, Will either of these wheels fit?

Thanks in advance.

Mark
Current cars M340i and a Caterham 7

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Z4 M40i

Post by B21 » Thu Jan 23, 2025 6:49 pm

tweeky687 wrote: Thu Jan 23, 2025 6:46 pm Hi all.
Please be gently on me I`ve just ordered A Z4 M40i for delivery in May.
Can anybody tell my the PCD and the centre bore Diameter.

My current car is an M340I and I`ve two set of wheels for it a set of 19 inch M898`s used for summer and set of 18inch 780 used for winter, Will either of these wheels fit?

Thanks in advance.

Mark
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Z4 M40i

Post by tweeky687 » Thu Jan 23, 2025 7:28 pm

Thank you
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Z4 M40i

Post by buzyg » Fri Jan 24, 2025 1:43 am

Welcome to the board Tweeky. :) Great user name btw. :thumbsup:
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Post by tweeky687 » Fri Jan 24, 2025 9:59 am

Thanks Buzyg,
Dates back to 1986 when I was working in Germany.
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Post by sars » Fri Jan 24, 2025 7:45 pm

Hello and welcome, the standard winter wheel/tyre for the Z4 M40i is a square 255/40 R18 on a 18 x 8.5 alloy ET 30. I run 255/35 R19 on 19 x 8.5 with Continental AllSeason Contacts and do not have an issue with grip in everyday use when it's cold and wet or frosty, a few inches of snow is not much of a hindrance, it's always the back that gives up first and it is controllable.

If your standard winter setup is 225/45 R18 on ET25, this has a similar diameter to 255/40 R18 and the poke is 8mm less than standard, so you could get a set of 10mm spacers to bring them out a bit, the key question is traction and stopping having less contact rubber.
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Z4 M40i

Post by deltasierra » Sun Jan 26, 2025 1:20 pm

I got a pair of cheap winter tyres to put on S/H rims, rubber compound seems very soft so I’m not expecting long life, maybe they will do 2000 miles before I change back in March

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Post by Nanu » Sun Jan 26, 2025 8:25 pm

I don't have the need for winter tyres. If snow and or ice, she stays in the garage 8)
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Post by sars » Sun Jan 26, 2025 9:12 pm

Nanu wrote: Sun Jan 26, 2025 8:25 pm I don't have the need for winter tyres. If snow and or ice, she stays in the garage 8)
Got your new tyres fitted yet?
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Post by Nanu » Mon Jan 27, 2025 9:05 pm

sars wrote: Sun Jan 26, 2025 9:12 pm
Nanu wrote: Sun Jan 26, 2025 8:25 pm I don't have the need for winter tyres. If snow and or ice, she stays in the garage 8)
Got your new tyres fitted yet?
Just fitted last Friday when returned from holidays. £665 for all four fitted, new valves not required. Haven't had the opportunity to give them a good run out yet but do seam a little quieter. Will give them a proper run over the next couple of days.
Had to enter them on the idrive manually as not recognised automatically but all seams to be working fine.
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Post by sars » Mon Jan 27, 2025 9:38 pm

Nanu wrote: Mon Jan 27, 2025 9:05 pm
sars wrote: Sun Jan 26, 2025 9:12 pm
Nanu wrote: Sun Jan 26, 2025 8:25 pm I don't have the need for winter tyres. If snow and or ice, she stays in the garage 8)
Got your new tyres fitted yet?
Just fitted last Friday when returned from holidays. £665 for all four fitted, new valves not required. Haven't had the opportunity to give them a good run out yet but do seam a little quieter. Will give them a proper run over the next couple of days.
Had to enter them on the idrive manually as not recognised automatically but all seams to be working fine.
Yep, I had to do that too, I wonder how the auto recognition works?
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Post by Nanu » Wed Jan 29, 2025 8:45 pm

Got your new tyres fitted yet?
[/quote]Just fitted last Friday when returned from holidays. £665 for all four fitted, new valves not required. Haven't had the opportunity to give them a good run out yet but do seam a little quieter. Will give them a proper run over the next couple of days.
Had to enter them on the idrive manually as not recognised automatically but all seams to be working fine.
[/quote]
Yep, I had to do that too, I wonder how the auto recognition works?

[/quote]The ride feels softer and less noise. Handling seems to be good, so far the car has gone in the direction I have pointed it which is a good sign. Confused re the pressures. One BMW site says 2.2 bar all round the car monitor recommends 2.3 bar and tyres currently 2.4 bar which the garage says is the correct pressure.
What do you run yours at?
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Post by sars » Wed Jan 29, 2025 9:40 pm

Nanu,
I think this may classify as a thread hijack :D
If you go to the screen where you had to configure the tyres, somewhere in there are three tyre pressure setting options, partially loaded comfort and eco and fully loaded. Each setting has different pressure settings, so dependant on temperature, comfort is 2.2 bar and eco is higher, I think 2.6 bar, mine are set at 2.3 bar. So anything between >2.2 and <2.6 bar is okay as long as they're all the same that is.
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Post by tweeky687 » Fri Jan 31, 2025 11:19 am

sars wrote: Fri Jan 24, 2025 7:45 pm Hello and welcome, the standard winter wheel/tyre for the Z4 M40i is a square 255/40 R18 on a 18 x 8.5 alloy ET 30. I run 255/35 R19 on 19 x 8.5 with Continental AllSeason Contacts and do not have an issue with grip in everyday use when it's cold and wet or frosty, a few inches of snow is not much of a hindrance, it's always the back that gives up first and it is controllable.

If your standard winter setup is 225/45 R18 on ET25, this has a similar diameter to 255/40 R18 and the poke is 8mm less than standard, so you could get a set of 10mm spacers to bring them out a bit, the key question is traction and stopping having less contact rubber.
So would that be spacers all round or just on the rears.

Thanks in advance.
Current cars M340i and a Caterham 7

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Post by sars » Fri Jan 31, 2025 5:03 pm

tweeky687 wrote: Fri Jan 31, 2025 11:19 am
So would that be spacers all round or just on the rears.

Thanks in advance.
Apologies, poke front is 8 mm and rear is 17 mm!, suggest you fit the rears and see how much room you have between the inside of the wheel arch to the outer edge of the tyre before buying 15.0mm spacers because 275 on a 10" wheel is slightly less stretched than a 225 on 7.5" wheel.

This explains why my rears look a little inbound compared to the normal rears which are 275/35 R19 as there is 5.0mm less poke and a smaller diameter.
IMG_3444[1].jpg
IMG_3444[1].jpg (336.6 KiB) Viewed 882 times
On order Black Sapphire Z4 M40i Handschalter 8) Current gorgeous SFR Z4 M40i
Gone 2017 Iridium SL400, 2015 435d xDrive Convertible, 2012 E350 CDi Convertible, 2010 DSB Z4 sdrive30i, 2008 Audi A4 Cabriolet, 2006 Phoenix Yellow Z4 2.5Si

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