New lightweight, square wheel/tyre combo for the E90

[PranK]

I've been reading a lot lately about unsprung weight and how beneficial it can be to reduce it for driving on the track, given my semi's only have another day or two in them I am throwing around the idea of some lighter wheels and a square set up.

I have 265/35/19's and 245/40(?)/19 Federal 595's at the moment. The wheels and tyres are super heavy. I looked up my wheel weight online and got 14.5kg naked. Not sure if this was 8.5 (front) or 9 (rear) but that's a lot.

I have also been reading about the benefits of a square setup. Much better rotation and potentially less understeer. 

When I throw these together I'm thinking about a 17x9 or 18x9 square (preferably under 10kgs per wheel) with 245 or 255's. I can get some cheap 17x8.5 BMW M Sport wheels, they weight 10.5 kg's each but at 8.5 wide could probably only get 245's on them? I know they come with 255's from factory but semi's are a bit chunkier.

Otherwise it will be aftermarket wheels in a 9" width. Most of the other BMW wheels are heavy unless you pay a squillion dollars for some M wheels. 

Although, the E46 M3 Style 67's could be good but I'd have to buy 2 sets to square them up. 

My car has a tickle over 400hp and about to put an LSD in also, is 245 a little thin for a square setup? It kinda feels that way to me.

Also, is there any tangible benefit to having 18's over 17's? Is the footprint demonstrably bigger?

From those of you who went to light(er) wheels after heavy buggers, did you notice it much?

[Murray_Calavera]

What type of track driving will you be doing? 

Do you have a set of class rules you need to abide by that will limit your rim / tyre width?

[PranK]

49 minutes ago, Murray_Calavera said:

What type of track driving will you be doing? 

Do you have a set of class rules you need to abide by that will limit your rim / tyre width?

Nah, nothing formal, just open track days. Mostly small and tight circuits but I would like to get back out to Eastern Creek at some stage.

[GTSBoy]

I have Enkei RPF1s in 17x8 that are 7 kg. That's about as light as it is possible to get without going forged.

Apparently 18x9s are only <1kg heavier.

Just the wheel, obviously.

 

[PranK]

24 minutes ago, GTSBoy said:

I have Enkei RPF1s in 17x8 that are 7 kg. That's about as light as it is possible to get without going forged.

Apparently 18x9s are only <1kg heavier.

Just the wheel, obviously.

 

Enkei's are what I've been looking at. There were some Enkei 18x9's in my stud pattern that weighed 8.5kg's so similar to what you said.

Did you notice a difference when switching to lighter wheels?

[Kinkstaah]

Apex wheels are the go-to for all things BMW. They have quite the level of information on weight, fitment and other things. A friend who had an E36 was extremely happy with the wheels he got from them.

They should answer anything potentially answerable on the subject. :p

https://apexwheels.com/fitment-guides/bmw/3-series/bmw-e90-e91-e92-e93-3-series-wheel-and-tire-fitment-guide

[PranK]

I've been to the Apex site at least a million times and never noticed that page. Much appreciated!

[GTSBoy]

24 minutes ago, PranK said:

Did you notice a difference when switching to lighter wheels?

Well, yeah, but not so as you'd be able to attribute it to the weight. Went from stock R32 16x6.5s with 225s (ie, a bit bulgy) to 17x8 with 235s. So more rubber with better geometry, along with maybe a weight change. Dunno what the stockies weigh bare.

[PranK]

To this day I find the stock R32 wheel size hilarious. 

[Murray_Calavera]

2 hours ago, PranK said:

Did you notice a difference when switching to lighter wheels?

I would be very surprised if you could tell the difference between 8kg and 12kg wheels in a blind A B test.

What you will be able to notice is going to wider wheels (+wider tyres). If you don't have to abide by any rules, I'd fit the widest wheels you can get under the guards.

[PranK]

18 hours ago, Murray_Calavera said:

I would be very surprised if you could tell the difference between 8kg and 12kg wheels in a blind A B test.

What you will be able to notice is going to wider wheels (+wider tyres). If you don't have to abide by any rules, I'd fit the widest wheels you can get under the guards.

Ok cool, because I do have some OEM BMW options for light(er) wheels. 17x8.5 M Sport wheels are 11kg and I could put 255's on them. Maybe that's an initial test.

[Murray_Calavera]

1 hour ago, PranK said:

Ok cool, because I do have some OEM BMW options for light(er) wheels. 17x8.5 M Sport wheels are 11kg and I could put 255's on them. Maybe that's an initial test.

Sounds good. Might be worth double checking what size rim the tyres you are running want. Generally I'd expect to see a 235 tyre on a 8.5 rim. Any possibility of an easy to source OEM 9.5 wide rim?

Also with the thoughts of the square setup, I'd still say wider is going to be better. Say your currently on 235 front and 255 rear. Going to square 255 will be better. But say you could fit, 255 front and 275 rear, that will be better again. 

In hypothetical land there might be a world where you go so wide that performance starts to go backwards, but I don't think you'll ever bump into that situation in real life.

[PranK]

So, the wheels in question come with 255 tyres from factory but I guess semi's are usually a bit fatter, maybe that's too much for an 8.5.

I'm currently running 245 front and 265 rear with Federal 595's on my 19's.

There are no OE square setups so to run square I either buy 2 sets of OE wheels or get an aftermarket set. I was thinking about the OE 17's I have because I already have one set (17x8, 17x8.5) and you can get another set for under $500. 

I do have another set of the same 19's (I have a bit of a wheel problem) so I could put together a 19x9 square setup but I'm conscious of the cost of semi's this size. 255 square on the 19's would be pretty cool though.

 

[PranK]

Oh, and I forgot that the main point of this topic was to reduce unsprung weight!