[Australian Bimmer]

Hi all. I am a recent new member from Australia. My car is a 220i M Sport coupe with M Sport brakes and adaptive suspension. Loving the car, had it 2 weeks.
I am hoping someone can answer this question for me.
I have noticed that when upgrading wheels, owners often appear to put wider front rims on while keeping the standard size tyres, for my car 225/45 18. On the back the wider rims get fitted with wider tyres.
What is the point of going from 7.5” rims to 8” on the front if the same size tyre is used?

[Maynard]

It provides a more stable angle for the sidewall. A 7.5" wheel is the smallest recommended for a 225/40 tire, so the sidewall curves in or is more rounded, and the tire will roll over a bit more. On an 8" it is more solid/straight, and on an 8.5 even more taught (but that is the wider end, so you get a bit harsher ride, and most prefer to add tire width rather than stretch the tire). Not a big issue unless you push the car harder or track it, but if you are replacing wheels, it is a modest upgrade.

[overcoil]

7.5 inch width aftermarket wheels for the 2-series are difficult to find. I only know of one aftermarket 7.5 inch wheel that installs.

[da jemster]

Lessens understeer.

[Australian Bimmer]

Thank you everyone. Appreciate the answers. So there is a benefit.

[goodNIGHT]

If you're just stretching the tire (trapezoid tire) then you'll increase steering response and feedback. But braking might become a little more squirrely under hard pressure. Since you'll decrease the profile you might increase fuel efficiency but decrease comfort.

[B58togo]

Originally Posted by da jemster

Lessens understeer.

No, it does not. The OP specifically inquired as to why people upgrade wheels, keep the same front tire size on wider wheels, and go wider on the rear tires on wider wheels.

This actually increases understeer.

OP, I'm more concerned with straight line traction than perfect driving dynamics, hence me retaining the stock front tire size on 8.5" Apex EC-7's and going to 265's on the rear 9.5". I had no other choice with the Apex in the offset I wanted. Plus I don't want to add any more unsprung weight.

[Australian Bimmer]

Originally Posted by ScottSinger

7.5 inch width aftermarket wheels for the 2-series are difficult to find. I only know of one aftermarket 7.5 inch wheel that installs.

Yes, I noticed that too. They all seem to be 8”. I can’t find any 7.5” to fit in Australia.
The reason I asked the question is that I am going to buy a rim to use as a spare wheel for long trips I do quite often. I have 2 rear tyres with only about 5,000 kms (3,000 miles) left in them and 2 almost new front tyres. So I need new rear tyres very soon. That are all currently Continental RFTs. I can ‘buy 3, get one free’ Bridgestone Potenza RFTs at a great price $339 each (great for Australia, I just paid $415 for a Potenza 19” for my wife’s Mini Countryman. My friendly BMW dealer wanted $605 for a Dunlop 19”).
I can get two Potezas of one size (rears 245/35 18) and two another size (for the front, 225/40 18) with this deal.
In Australia, Bridgestone is the only brand that gives a pro-rata replacement deal on RFTs. If they can’t be repaired from a puncture or other accidental ‘road hazard’ damage you get an appropriate discount on a replacement. If the tyre is less than 10% worn the replacement is free, if it is 20% worn, you get 80% discount etc. etc.
I just found out about this Bridgestone pro-rata deal after replacing the Countryman’s tyres with Dunlops and then recently losing one to an irreparable puncture. $400 odd dollars down the drain, if I had purchased Potenzas it would have been a free replacement. So I replaced it with a Bridgestone and now have one almost new Dunlop and one brand new Bridgestone on the rear, non-driving wheels of the Mini. Not ideal I know but she drives very sedately and I will get a Bridgestone on the other side as soon as I need another new tyre for that car.
So, back to the 2 Series, I plan to buy 4 Bridgestones and get them all fitted and then keep the 2 front Contis as spares. I will mount one on a rim and take it if venturing too far from the capital (that isn’t hard to do in Australia, it is pretty sparse out there once you leave the main cities). I do these trips alone in the 2 Series Coupe so luggage space isn’t an issue as I only take a soft overnight bag.
I believe an 8” rim that fits the front with the standard sized 225/40 18 tyre will be ok for a spare for both the front and rear, temporary only until I either get the Bridgestone repaired or replaced. I have M Sport Brakes but believe from what I have read on here that the front rim should be ok on the rear as a spare option.
I could just but 3 tyres (2 for the rear and a spare to mount on a spare rim) and keep the Contis on tbe front, but with this deal I can get 4 for the same price as 3, so I may as well buy 4 and have Bridgestones all round.
Bye the way, we are pretty much on fire here at the moment. We have massive bush fires. I live 85kms from Brisbane and have had to set the alarm every 2 hours for 4 out of the last 7 nights to check if we have to evacuate. We are on a ‘prepare to leave’ warning that goes to a ‘watch and react’ warning when the wind dies down.
Oh, well, at least I have the cars and their tyres to distract me from the constant choking smoke!

[da jemster]

Originally Posted by B58togo

No, it does not......This actually increases understeer....

You're right, I missed his statement on "keeping the standard size tyres"

Originally Posted by Australian Bimmer

Hi all...I have noticed that when upgrading wheels, owners often appear to put wider front rims on while keeping the standard size tyres...

I assumed he was going to square his setup.