GTS twins: the GTMore journey

[markw10702]

Originally Posted by GuyLedouche

Is there an upgraded front wheel bearing/hub setup available? I have 4 track days and less than 30k miles on one and it's toast. I'm definitely doing the Motorsport rears now.

Even the M4 GT4 uses the standard wheel bearing / hub. 31207857506

I am not aware of an upgraded version.

[FaRKle!]

Originally Posted by markw10702

Even the M4 GT4 uses the standard wheel bearing / hub. 31207857506

I am not aware of an upgraded version.

But they probably also recommend a 7500km replacement interval.

[SYT_Shadow]

Originally Posted by GuyLedouche

Is there an upgraded front wheel bearing/hub setup available? I have 4 track days and less than 30k miles on one and it's toast. I'm definitely doing the Motorsport rears now.

for the front there is not. New OEM ones every 5k miles/once a season.

[GuyLedouche]

Originally Posted by SYT_Shadow

for the front there is not. New OEM ones every 5k miles/once a season.

Sounds like a plan.

[SYT_Shadow]

Originally Posted by GuyLedouche

Sounds like a plan.

Yup. Been there many times. Interestingly they puke their guts out but continue to work just fine for quite a while!

[melanthius]

Originally Posted by SYT_Shadow

Yup. Been there many times. Interestingly they puke their guts out but continue to work just fine for quite a while!

I couldn't locate a source for the "bmw Motorsport" rears you referenced. Where do you buy?

And what is your interval for those?

I had my car at SV bimmer and told them I was thinking of changing the wheel hubs as preventative maintenance and they looked at me like I was the biggest idiot and just said they don't recommend worrying about it until they "start going out"

Although I'm not running on slicks or ultra fast times so maybe I just have that much less stress in them. my car has over 60k miles and at least a handful of track days on it.

[melanthius]

User chrisjguzman helped me find it, but fyi dude your pm inbox is full.

[SYT_Shadow]

Originally Posted by melanthius

I couldn't locate a source for the "bmw Motorsport" rears you referenced. Where do you buy?

And what is your interval for those?

I had my car at SV bimmer and told them I was thinking of changing the wheel hubs as preventative maintenance and they looked at me like I was the biggest idiot and just said they don't recommend worrying about it until they "start going out"

Although I'm not running on slicks or ultra fast times so maybe I just have that much less stress in them. my car has over 60k miles and at least a handful of track days on it.

It's a rare incident, but I've seen two in person already. I won't be the third.

Hubs usually last a while so I won't be replacing these until something happens.

Here's the link to the hubs. Note you can also use the upgraded rear bearings to complete the set

https://www.bimmerworld.com/Drivelin...008328143.html

https://www.bimmerworld.com/Drivelin...82-M4-GT4.html

[fanatic1]

Originally Posted by SYT_Shadow

It's a rare incident, but I've seen two in person already. I won't be the third.

Hubs usually last a while so I won't be replacing these until something happens.

Here's the link to the hubs. Note you can also use the upgraded rear bearings to complete the set

https://www.bimmerworld.com/Drivelin...008328143.html

https://www.bimmerworld.com/Drivelin...82-M4-GT4.html

Have you considered the core4 hubs for press in studs?

Edit, looks like these are press in and heavier duty

[SYT_Shadow]

Originally Posted by fanatic1

Have you considered the core4 hubs for press in studs?

Edit, looks like these are press in and heavier duty

I've heard about them for years, but I'm not sure what they solve in the F8X.
In the E9X I do use their 14mm conversion

Front f8x: the bearing is what dies, not the stud. I have to replace hubs every year due to the bearing failing, so I prefer to use fcp and use the stock piece. 14mm studs don't fail at all when swapped every season

Rear f8x: i prefer the motorsport hub. The Core hub uses the f8x design which can break

[fanatic1]

Originally Posted by SYT_Shadow

I've heard about them for years, but I'm not sure what they solve in the F8X.
In the E9X I do use their 14mm conversion

Front f8x: the bearing is what dies, not the stud. I have to replace hubs every year due to the bearing failing, so I prefer to use fcp and use the stock piece. 14mm studs don't fail at all when swapped every season

Rear f8x: i prefer the motorsport hub. The Core hub uses the f8x design which can break

Broke a few rear studs, never had a problem with the front. Was considering press in - the shoulder for the threaded was where they were breaking.

But that MacGyver trick for removing studs made easy work of annual stud replacement

[SYT_Shadow]

Originally Posted by fanatic1

Broke a few rear studs, never had a problem with the front. Was considering press in - the shoulder for the threaded was where they were breaking.

But that MacGyver trick for removing studs made easy work of annual stud replacement

That's really interesting. For me it's the fronts. That said, they no longer break when replaced annually

[sly1types]

Originally Posted by SYT_Shadow

Correct, getting overfill messages

Edit: when you're below 7.3L it'll show less than full. The queue for me to add a quart is when it shows full (so 7.3L).

Maybe my sensor is bad. I just did my second oil change. I tried 7 quarts and it wouldn't show less than full, but i went to a full 8 quarts and it showed full not "overfull".

Next oil change maybe i will try 6.5quarts and see what it says. I just need to see at what point it shows less than full...

[SYT_Shadow]

Originally Posted by sly1types

Maybe my sensor is bad. I just did my second oil change. I tried 7 quarts and it wouldn't show less than full, but i went to a full 8 quarts and it showed full not "overfull".

Next oil change maybe i will try 6.5quarts and see what it says. I just need to see at what point it shows less than full...

there may be a histeresis range in the sensor to not freak people out

[SYT_Shadow]

We've been meaning to post the Motorsport rear hub photos but haven't been able to yet
These are the motorsport hubs with BimmerWorld studs installed

Here they are!

[SYT_Shadow]

Also important: kingping modification. The GTS' come with a very, very sexy billet machined kingpin. This gives extra clearance for wide wheels/tires as well as extra camber.
As with many good things, there were teething issues: the 'v1' front billet kingpins fail eventually. They made a 'v2' version but did not replace your 'v1' unless it failed under warranty.
The v2 kingpin is pretty expensive, around 2500 each.

Some 'v1s' made it past the warranty. Fortunately, the 'v2' is simply the 'v1' with some intelligent machining done to it.
We had heard of all the issues with kingpins prior to purchasing GTS1 & 2 and never gave it much thought, that is until user Prodrive_X posted pictures of the v1 and v2.
As mechanical-industrial engineers we are appalled at the mistake they did in v1. You should never concentrate stress in a thin location in a piece, and even the simplest Solidworks model would quickly show you that 'v1' is a no-no.

Anyway, GTS1 has the v2 kingpin and GTS2 has the v1. We parked them by each other and that made the process easy. You could do this modification without photos of v2 because all you're trying to do is remove the stress concentration.

The tools are simple: a dremel for fine work and a angle grinder for the big work.
We used a random angle grinder with a 'diablo' disc, the same one we used to modify the M3 Invisihitch into a M4 model that they don't sell.



We used a black sharpie to mark the area we were trying to get rid of




The almost-final result, just needs some polishing


Final result




[disclaimer: High-performance driving and automotive modification carry inherent risks.
High-performance driving can be very dangerous and may result in injury or death. We make no representations or warranty about products protecting against injury or death.
Car modifications of any kind that facilitate high-performance driving may reduce or limit the life of your car and any of its wearable parts and could result in damage to the car. We are not responsible for damage of any kind]

[adc]

Wait, so removing material from the area increases the strength? How, does it simply get redistributed a different path/arc?

[SYT_Shadow]

Originally Posted by adc

Wait, so removing material from the area increases the strength? How, does it simply get redistributed a different path/arc?

I've attached the image of a stress concentration. In a nutshell, you don't want large variations in material thickness as that concentrates stress in a single point, which will fail. This is way sections usually are smooth.

In the case of the GTS kingpin v1, the material is extra thick and ends up in a very thin part, which cracks. By removing material I'm allowing better distribution of the stress

If I had a copy of ANSYS I could show this effect easier, but at this point I don't even have Solidworks.

I'll page NYG who may explain it better

[NYG]

Originally Posted by SYT_Shadow

I've attached the image of a stress concentration. In a nutshell, you don't want large variations in material thickness as that concentrates stress in a single point, which will fail. This is way sections usually are smooth.

In the case of the GTS kingpin v1, the material is extra thick and ends up in a very thin part, which cracks. By removing material I'm allowing better distribution of the stress

If I had a copy of ANSYS I could show this effect easier, but at this point I don't even have Solidworks.

I'll page NYG who may explain it better

What am I explaining here?

I see a concentration of tensile forces at the neck.

More cross-section = less deflection/lower stress
Less cross-section = higher deflection/higher stress/susceptibility to buckling on compression face

[SYT_Shadow]

Originally Posted by NYG

What am I explaining here?

I see a concentration of tensile forces at the neck.

More cross-section = less deflection/lower stress
Less cross-section = higher deflection/higher stress/susceptibility to buckling on compression face

The original knuckle design has a extra reinforcement that then lands right in the weakest spot of the knuckle. The modified bmw one removes all that extra material

Thank you

[adc]

Thank you guys. I'm not mechanically disinclined, but I should have paid more attention to that mechanical engineering course in school.

[polarbearz]

How's the quality of TA5R? I heard flow formed wheels have a possibility to bend or crack on track. I am deciding which wheels to buy. Is it necessary to buy the forged TA16?