OEM Wheels: M4 GT4 vs M4 CS

[x.shell]

Anyone know if the M4 GT4 wheels will be available to purchase? They are the same style as the CS wheels (M-Perfomance wheels), but are way more concave.

M4 CS









M4 GT4

[CanAutM3]

Aren"t the GT4 wheels 18"?

The concavity also likely stems from lower offsets and wider wheels (18x11). I am not sure they would meet the clearance margins that would allow BMW to make them "street legal".

[x.shell]

Originally Posted by CanAutM3

Aren"t the GT4 wheels 18"?

The concavity also likely stems from lower offsets and wider wheels (18x11). I am not sure they would meet the clearance margins that would allow BMW to make them "street legal".

What you say about the offsets and making them street legal makes sense, but does that same criteria apply to OEM aftermarket parts as well? Even the OEM M4 GTS wheel offset is pretty aggressive for the front; making snow chains kind of iffy (my unscientific observation).

In any case, you're probably right about them being unavailable. Bmw probably wouldn't want to go through the hassle.

[M3Tooner]

Does the M4 GT4 run 18x11 square setup? Looks like it does. I wonder if the wheel offset is the same front to back. Interested in finding out how they pulled that off and if any spacers are being used. A square 305 tire setup will be sweet for the track!

[x.shell]

Originally Posted by M3Tooner

Does the M4 GT4 run 18x11 square setup? Looks like it does. I wonder if the wheel offset is the same front to back. Interested in finding out how they pulled that off and if any spacers are being used. A square 305 tire setup will be sweet for the track!

I wonder too. Unless they reworked the geometry, I don't see how they can run a square 18x11 set up without using spacers for the front. A couple folks on this forum has gotten a 18x11 + 305 square set up to work in the Apex thread. However, front spacers + very specific suspension + a lot of negative camber was necessary.

[F3IGHTY]

It is 18x11 square and they run a massive spacer up front. Pics in the GT4 sales brochure.

These wheels and the GT4 Ohlins setup are on my wishlist. Someone with a motorsport account needs to hook up us with some spares orders lol.

[mcvaughan]

The motorsport wheels are very tasty!

[swagon]

The wheels are made by SAI http://superalloyengineering.com/products/wheels/, a Taiwanese company that supplies forged wheels to Ferrari or McLaren (even the P1, apparently).

Some person in another thread said that the CS/ M Performance wheels have "Made in Taiwan" stamped on them so they are made by the same company, too.

BTW, all other M3/M4 wheels are from Fuchs.

[x.shell]

Originally Posted by F3IGHTY

It is 18x11 square and they run a massive spacer up front. Pics in the GT4 sales brochure.

These wheels and the GT4 Ohlins setup are on my wishlist. Someone with a motorsport account needs to hook up us with some spares orders lol.

Originally Posted by swagon

The wheels are made by SAI http://superalloyengineering.com/products/wheels/, a Taiwanese company that supplies forged wheels to Ferrari or McLaren (even the P1, apparently).

Some person in another thread said that the CS/ M Performance wheels have "Made in Taiwan" stamped on them so they are made by the same company, too.

BTW, all other M3/M4 wheels are from Fuchs.

Thanks for the info guys.

[M3Tooner]

Originally Posted by F3IGHTY

It is 18x11 square and they run a massive spacer up front. Pics in the GT4 sales brochure.

These wheels and the GT4 Ohlins setup are on my wishlist. Someone with a motorsport account needs to hook up us with some spares orders lol.

Is that the massive spacer i see in the picture? Looks like at least 25mm. I can't believe it is acceptable for a motorsports team to run that big of a spacer and not have durability concerns of putting a lot of stress on the studs and wheel bearing. They must've done something else to make it work, especially for 24 hours endurance racing.

[CanAutM3]

Originally Posted by M3Tooner

Is that the massive spacer i see in the picture? Looks like at least 25mm. I can't believe it is acceptable for a motorsports team to run that big of a spacer and not have durability concerns of putting a lot of stress on the studs and wheel bearing. They must've done something else to make it work, especially for 24 hours endurance racing.

Maybe the spacer is just there to allow using the same wheels front and rear. The positioning of the bearing could have very well been designed accordingly. Further, a well designed and fitted hub centric spacer does not put that much more stress on the studs. The studs squeeze the assembly together and it is the friction between the components that carries the most of the load.

[x.shell]

Originally Posted by M3Tooner

Is that the massive spacer i see in the picture? Looks like at least 25mm. I can't believe it is acceptable for a motorsports team to run that big of a spacer and not have durability concerns of putting a lot of stress on the studs and wheel bearing. They must've done something else to make it work, especially for 24 hours endurance racing.

When a spacer is that thick, the spacer is actually fastened straight into the hub. And the hub-centric design of the spacer will take all stress off the bolts.

Kind of like this.


Although the added weight might introduce more stress on the bearings, it's probably a worthwhile trade off to have the ability to run a squared set up.

[M3Tooner]

Originally Posted by CanAutM3

Maybe the spacer is just there to allow using the same wheels front and rear. The positioning of the bearing could have very well been designed accordingly. Further, a well designed and fitted hub centric spacer does not put that much more stress on the studs. The studs squeeze the assembly together and it is the friction between the components that carries the most of the load.

Agreed that the spacer is needed to run the square setup. Here's a closer picture of the assembly. You can see the original hub pilot nesting deep inside the spacer, which suggest that the bearing position may not have been changed?

One other thing I noticed, and it may be an artifact of the picture angle but it seems like the rotor offset is shallower than base car. Meaning the rotor is sitting far more outboard than base car.

[M3Tooner]

Originally Posted by exo-shell

When a spacer is that thick, the spacer is actually fastened straight into the hub. And the hub-centric design of the spacer will take all stress off the bolts.

Kind of like this.


Although the added weight might introduce more stress on the bearings, it's probably a worthwhile trade off to have the ability to run a squared set up.

The additional stress on the wheel bearing will come from the change in the distance from wheel center line to bearing center line. The added weight of the spacer will have minimal affect on bearing stress and it looks like the one used on the M4 GT4 is quite weight optimized.

Can somebody calculate if an 11" wide wheel with proper spacing/offset is able to keep the distance between Center Lines to be same as base car?

[x.shell]

Originally Posted by M3Tooner

Agreed that the spacer is needed to run the square setup. Here's a closer picture of the assembly. You can see the original hub pilot nesting deep inside the spacer, which suggest that the bearing position may not have been changed?

One other thing I noticed, and it may be an artifact of the picture angle but it seems like the rotor offset is shallower than base car. Meaning the rotor is sitting far more outboard than base car.

This could be the case to create more room for the brake cooling ducts right behind it. It looks to me, like you suspect, that the bearing position is the same though.

Originally Posted by M3Tooner

The additional stress on the wheel bearing will come from the change in the distance from wheel center line to bearing center line. The added weight of the spacer will have minimal affect on bearing stress and it looks like the one used on the M4 GT4 is quite weight optimized.

Can somebody calculate if an 11" wide wheel with proper spacing/offset is able to keep the distance between Center Lines to be same as base car?

I can't do an accurate calculation because I don't have the offset information, but an estimation results in a wheel's center line that sits a lot more outboard vs the stock M4 with OEM 18" wheels. So yes, there is more stress on the hub/bearing. But again, the cons of such a set up is probably offset by the gains they achieve by going with a wider tire and track. They just need to last 24hrs at the most and even if they don't, it's a quick fix in the pits.

[M3Tooner]

Agreed that the benefits probably far offset the reduced bearing life. More rubber in the front for better grip, Less complexity in wheels/tires that the team needs to carry, Ability to reuse tires in a any corner of the car, and etc.... But I chuckled when you said "They just need to last 24hrs at the most". I know what you mean.

But yes, if it is good enough for 24hrs of endurance racing, it's good enough for some of us that only do 20-30 minutes per session of HPDE, that's for sure.

[Drew@Sonic MS]

Confirming the GT4 is a 18x11 square set up.

Available for order as well as all the other parts

[x.shell]

Originally Posted by Drew@Sonic MS

Confirming the GT4 is a 18x11 square set up.

Available for order as well as all the other parts

Are all the parts available for us regular folk? Or do you need to buy the GT4 first?

[Drew@Sonic MS]

Originally Posted by exo-shell

Are all the parts available for us regular folk? Or do you need to buy the GT4 first?

We can help out .

Some items are ridiculously priced like the front lip but the wheels were surprisingly not too bad. About half the price of the front lip for all 4...

[The Choosey begger]

Those are going to be ridiculously expensive, APEX wheels and call it a day. I've tested lighter wheels back in the day, my times were pretty much the same, we're talking 20lbs vs 23lbs wheels.

I know in theory better stopping, better acceleration blah blah

[Parabolica]

Originally Posted by F3IGHTY

It is 18x11 square and they run a massive spacer up front. Pics in the GT4 sales brochure.

These wheels and the GT4 Ohlins setup are on my wishlist. Someone with a motorsport account needs to hook up us with some spares orders lol.

Are they using Ohlins or Bilstien? It says Bilstien on the GT4.

[F3IGHTY]

Originally Posted by Parabolica

Are they using Ohlins or Bilstien? It says Bilstien on the GT4.

That's just the title sponsor of the N24, the GT4 runs Ohlins TTx.