Why 19 Inch Fronts on CS and GTS?

[chrison600]

Hi all,

I'm looking around at wheels for my 2015 M4 and was a bit surprised to discover that although the current M4 with Competition Pak is equipped with 20 inch wheels front and rear, the CS and GTS have 19 inch fronts with 20 inch rears.

Come to find out, this configuration (19 front/20 rear) is also used on the C63 and 911 GT3 CS.

Can anyone clear up why this is done?

Chris

[uniqueMR]

In simple terms: larger diameter rear wheels and tires aid traction and ensures a steady supply of grip.

[bigrum]

I've been wondering the same thing as I consider the 763M wheels instead of my current 20inch all around 666M wheels. I think the former look better and my god they look easier to clean.

So to whomever reads this post, would you switch? Why or why not?

[G35POPPEDMYCHERRY]

i ordered the wrong tires for my sister m-sport 428xi. since its a staggered setup. since that car has a lot of traction issues

[EricSMG]

Originally Posted by uniqueMR

In simple terms: larger diameter rear wheels aid traction and ensures a steady supply of grip.

Wheels or tires?

Not the same thing, please clarify your thought process.

[uniqueMR]

Originally Posted by EricSMG

Wheels or tires?

Not the same thing, please clarify your thought process.

Here you, Sir:
In simple terms: larger diameter rear wheels/tires aid traction and ensures a steady supply of grip.

[MNoob]

Originally Posted by uniqueMR

Here you, Sir:
In simple terms: larger diameter rear wheels/tires aid traction and ensures a steady supply of grip.

26.6 vs 26.8. that seems like a pretty negligible increase.

[RevNev]

The CS and GTS have 19's on the front to stop understeer caused by the low profile 20's. They steer and generally handle better with 19's on the front and CS 763M wheels are lighter than the 666M's and look much better I think.

[Bluer2]

Originally Posted by RevNev

The CS and GTS have 19's on the front to stop understeer caused by the low profile 20's. They steer and generally handle better with 19's on the front and CS 763M wheels are lighter than the 666M's and look much better I think.

is that powder coated or painted? and what color is that?

[RevNev]

Originally Posted by Bluer2

is that powder coated or painted? and what color is that?

They're painted in BMW Dekorsilver paint code A55. It's the same colour as the E90/92 359M wheels.

[Darth One]

Reason is simple: the smaller diameter in front greatly decreases the gap between the wheel and heat shield, thereby vastly improving the setup’s efficiency at getting pebbles getting stuck in there and increasing bmw’s parts sales. Quite ingenious, really

[CanAutM3]

Originally Posted by uniqueMR

Here you, Sir:
In simple terms: larger diameter rear wheels/tires aid traction and ensures a steady supply of grip.

I'm not sure what this is based on

In general terms, tire tuning is much like suspension tuning: softer translates to more grip while stiffer translates to sharper handling response. So a 20" wheels with 30 profiles tires will have a sharper response but less grip than a 19" wheel with a 35 profile tire due to less flex from the sidewall.

I can only assume that BMW did this to improve the overall balance of the car when shod with sticky r-compound tires as the GTS and CS were designed to use.

[CanAutM3]

Originally Posted by RevNev

The CS and GTS have 19's on the front to stop understeer caused by the low profile 20's. They steer and generally handle better with 19's on the front and CS 763M wheels are lighter than the 666M's and look much better I think.

The 763M are gorgeous IMO, particularly in that colour . The best OEM BMW wheel in a very long time IMO.

I wonder why BMW is not offering them in such colour.

[RevNev]

Originally Posted by CanAutM3

I can only assume that BMW did this to improve the overall balance of the car when shod with sticky r-compound tires as the GTS and CS were designed to use.

Most circuit cars don't have mega low profile tyres, Formula 1, Nascar etc and although low profile provides a sharper turn in, they tend to have less overall grip than a taller tyre with more flex.

20's on the M3/M4 were likely for aesthetics until they track tested and found it didn't work and their dedicated track cars (CS/GTS), performance is their priority over popular aesthetic "big wheel" trends.

[CanAutM3]

Originally Posted by RevNev

Most circuit cars don't have mega low profile tyres, Formula 1, Nascar etc and although low profile provides a sharper turn in, they tend to have less overall grip than a taller tyre with more flex.

Pretty much what I said, no ?

[RevNev]

Originally Posted by CanAutM3

The 763M are gorgeous IMO, particularly in that colour . The best OEM BMW wheel in a very long time IMO.

I wonder why BMW is not offering them in such colour.

I agree, the 763M wheels look fantastic but I think matte black accommodates an aesthetic trend but masks the true beauty of the wheel. When blinged out a bit in silver particularly on a dark colored car emphasises their beauty I think.

The 666M wheels aside from being a mongrel to keep clean, are the ugliest wheels they've fitted to an M model car, couldn't convince myself to like them even with spacers and a set of lower springs.

[R-M4]

I don't know much about wheels at all. However, I chose the 19" wheels for my M4 (competition package) because of looks.
I believe there was a time when you couldn't choose the wheel size an all competition package M4's came with 20".

[melvyn]

These are the BM stared Cup tyres on the CS, fronts are 19s with more cut tread on outer edge in to cut down on understeer, rears are 20s with more slick from outer enge in for more grip.CS and GTS were tested on this setup.

Click on pic for bigger pic.

[CanAutM3]

Originally Posted by melvyn

fronts are 19s with more cut tread on outer edge in to cut down on understeer

Could you elaborate why "more cut tread on outer edge" would reduce understeer?

[melvyn]

Originally Posted by CanAutM3

Could you elaborate why "more cut tread on outer edge" would reduce understeer?

Only if you can explain why BM went to all the trouble to test this setup on the GTS and CS.
I suggest you get on your "Google" again, plenty of information there for you.


Is there anything that you do not know?

[CanAutM3]

Originally Posted by melvyn

Is there anything that you do not know?

Plenty, and I have not heard of this theory before, hence why I am asking the question...

Originally Posted by melvyn

Only if you can explain why BM went to all the trouble to test this setup on the GTS and CS.
I suggest you get on your "Google" again, plenty of information there for you.

That doesn't provide much of an answer now, does it?

[M3SQRD]

Originally Posted by CanAutM3

Plenty, and I have not heard of this theory before, hence why I am asking the question...

That doesn't provide much of an answer now, does it?

And I always thought “cut tread” was to improve wet performance, not increase dry performance