Trying to understand wheels

[fomb]

I've got an E70 30d on 20" RFTs and the ride is appalling and new tyres are going to cost me a fortune, so I'm looking at replacing the current wheels with 19"s and going non-RFT. However after a quick look on eBay I've managed to completely confuse myself over wheel sizing.

Right now I know I have 275/40 front and 315/35 rear but from looking at 19"s the sizing is all different.

How can I replace the wheels without completely ballsing everything up?

[ucb]

Look at the lower spec models in range with the same engine ie the SE if you've got MSport etc
And use

https://www.wheel-size.com/calc/
Www.wheelfitment.eu/

[Pica-Pica]

Look at your tyre label and see what sizes you can use (minimum rim size)
Also use this to compare rolling circumferences.
http://www.wheelcalc.com/

[Regbuser]

Or look on https://www.alloywheelsdirect.net/ for your model, from there you'll see your current wheels and possible smaller diameters with matching tyres.
Make a note of the part numbers, then search on eBay.

[d_a_n1979]

fomb said:

I've got an E70 30d on 20" RFTs and the ride is appalling and new tyres are going to cost me a fortune, so I'm looking at replacing the current wheels with 19"s and going non-RFT. However after a quick look on eBay I've managed to completely confuse myself over wheel sizing.

Right now I know I have 275/40 front and 315/35 rear but from looking at 19"s the sizing is all different.

How can I replace the wheels without completely ballsing everything up?

ALL BMW alloys are on here:

https://www.auto-treff.com/wcf/index.php?category-...

If you use Chrome; it'll translate it to English for you and if you look at the menu on the right hand side; you'll see all the BMWs by their code (ie F01 for my 7 series etc)

As long as the 19s you're looking to fit match the offset (give or take 10 less than yours, NOT more) then you're fine to go with them (and as long as they're 5x120)

But obviously you need to ensure that they're for an SUV too

That website will also give you the correct OEM BMW tyre sizes

So; this is the link for the E70 alloys and all their information: https://www.auto-treff.com/wcf/index.php?tagged/64...

Personally I'd just stick with the 19s that were fitted to the E70; keeps it easy then

I'm doing exactly the same albeit with my F01 730D; selling the 20s on to fit 19s after winter (I've got 18s and winter tyres to fit in the next few weeks); find that the 20s tramline badly on the poor country roads that surround me and that's with the suspension in perfect health and a very recent full tracking & alignment... 19s will be much better suited

Edited by d_a_n1979 on Tuesday 26th October 08:27

[fomb]

Thanks - do I need to worry about tyre width that much? 315s are heckin wide on the rear and I suspect I won't find 19s anywhere near as wide.

[mmm-five]

fomb said:

Thanks - do I need to worry about tyre width that much? 315s are heckin wide on the rear and I suspect I won't find 19s anywhere near as wide.

You can get 315 width in 15" tyres, so I'd not worry about finding them in 19" sizes - and if it's a standard size from a 'lesser' model then they'll be readily available.

[Pica-Pica]

You will need to get the best wheel rim width to tyre width match as well. See chart on here:
https://mechanics.stackexchange.com/questions/3961...

As an exemplar: my F30 335d comes with
8” width rim front and 225mm tyres
8.5” width rim rear and 255mm tyres
(Nothing like your monsters, but the chart will show the acceptable range.

Another thing to be aware of is the rim profile. I believe JJ is the correct rim profile for run flats and for AWD vehicles. DON’T quote me on that, as I cannot find reliable information on line, but I believe that JJ profile provides a more secure tyre retention than a J profile.

[fomb]

One last one - which I hope is the last. I notice my rears are 35 profile vs the front at 40 which I assume is a slight difference in rolling radius. Do I need to really worry about that? It seems like a tiny difference

[Scrump]

fomb said:

One last one - which I hope is the last. I notice my rears are 35 profile vs the front at 40 which I assume is a slight difference in rolling radius. Do I need to really worry about that? It seems like a tiny difference

35 and 40 are percentages of the width. As your front tyres are narrower than your rear tyres then the overall diameter is the same.

40% of 275 = 110
35% of 315 = 110

Exactly the same diameter front and rear.

[d_a_n1979]

fomb said:

One last one - which I hope is the last. I notice my rears are 35 profile vs the front at 40 which I assume is a slight difference in rolling radius. Do I need to really worry about that? It seems like a tiny difference

Yes; use the willtheyfit website to suss out what tyres you can change to:

https://www.willtheyfit.com/

It's all about keeping within the 2.5% +/- tolerances so your diff & speedo aren't affected

[Pica-Pica]

fomb said:

One last one - which I hope is the last. I notice my rears are 35 profile vs the front at 40 which I assume is a slight difference in rolling radius. Do I need to really worry about that? It seems like a tiny difference

The rolling circumference can be found in the calculator I posted
http://www.wheelcalc.com/
So if the rear tyres are wider than the fronts then the rolling circumference may be the same if the rear profile is smaller (or similar). You should stick to the sizes on the tyre label.
Example for mine (OEM sizes)
225/45 x 18” front = rolling circumference of 2010mm
255/40 x 18” rear = rolling circumference of 2016mm
Which are acceptably close to each other.

[fomb]

Oh man, this is confusing. I know my wheels are ET35/40 F/R whereas wheelfitment says they're ET48.
You then look at eBay and that's telling you that E71 alloys (ET21/48 F/R) will fit just fine.
I suppose I'll just have to stick with the wheel styles that I know fit the E70 and wait for some to pop up

[d_a_n1979]

Look at that link I provided and don't use ebay. Lots of wrong info on ebay whereas the website I provided shows all wheels and their necessary details. Stick to that.

You'll be fine with 19" alloys suited to the X range as long as they have similar offsets to your alloys currently.

If they have an offset of c35, you'll be fine with the same or less down to say 20/25, they'll sit closer to the line of the arch, but not outside etc... Similar if you were to use spacers to space them out etc

There are lots of E70 19" alloys; however finding a set could prove hard work, just a case of keep checking eBay and Gumtree and maybe local breakers etc

Edited by d_a_n1979 on Wednesday 27th October 13:20

[fomb]

d_a_n1979 said:

Look at that link I provided and don't use ebay. Lots of wrong info on ebay whereas the website I provided shows all wheels and their necessary details. Stick to that.

You'll be fine with 19" alloys suited to the X range as long as they have similar offsets to your alloys currently.

If they have an offset of c35, you'll be fine with the same or less down to say 20/25, they'll sit closer to the line of the arch, but not outside etc... Similar if you were to use spacers to space them out etc

There are lots of E70 19" alloys; however finding a set could prove hard work, just a case of keep checking eBay and Gumtree and maybe local breakers etc

Edited by d_a_n1979 on Wednesday 27th October 13:20

Definitely. I've yet to find a semi-decent set that have anywhere near the right offsets

[d_a_n1979]

fomb said:

d_a_n1979 said:

Look at that link I provided and don't use ebay. Lots of wrong info on ebay whereas the website I provided shows all wheels and their necessary details. Stick to that.

You'll be fine with 19" alloys suited to the X range as long as they have similar offsets to your alloys currently.

If they have an offset of c35, you'll be fine with the same or less down to say 20/25, they'll sit closer to the line of the arch, but not outside etc... Similar if you were to use spacers to space them out etc

There are lots of E70 19" alloys; however finding a set could prove hard work, just a case of keep checking eBay and Gumtree and maybe local breakers etc

Edited by d_a_n1979 on Wednesday 27th October 13:20

Definitely. I've yet to find a semi-decent set that have anywhere near the right offsets

Stick to the E70 alloys as per that link; they'll have the correct offsets then

[fomb]

d_a_n1979 said:

Stick to the E70 alloys as per that link; they'll have the correct offsets then

You would have thought so, but having been through them all, none are the same. I have the 333M alloys which seem to have different offsets to the other styles

Edited by fomb on Thursday 28th October 16:14

[naturalaspiration]

Offset is different as it needs to be match different wheel widths - within allowed specs. X5 alloys are also quite sturdy in order to whitstand greater forces caused by X5's non trivial weight.

[fomb]

naturalaspiration said:

Offset is different as it needs to be match different wheel widths - within allowed specs. X5 alloys are also quite sturdy in order to whitstand greater forces caused by X5's non trivial weight.

So, if you have a narrower wheel, say a 315 down to a 285, the wheel is 30mm narrower. Therefore the center line of the wheel should be closer to the hub by 15mm? Therefore, your ET40 is essentially now ET25?

[d_a_n1979]

fomb said:

d_a_n1979 said:

Stick to the E70 alloys as per that link; they'll have the correct offsets then

You would have thought so, but having been through them all, none are the same. I have the 333M alloys which seem to have different offsets to the other styles

Edited by fomb on Thursday 28th October 16:14

They don't have to be the same offsets as your current wheels; just the correct set for the X5 E70... That's why I state stick to those styles as per that link...