E92 M3 Track / Racecar Project

[rTrackM3]

These are great explanations! Love the discussion here, everyone. I really appreciate this!!!

Just curious... are the findings more chassis specific? I only ask because I tracked / raced an e46 M3 for years putting over 2,000 miles per month on track and never once broke a stud. We had some come loose over time, but that was it. We ran a mix of Fall-Line and BimmerWorld studs exchanging studs every season. We torqued them to 82 ft/lbs at every event and only when it was completely cooled down. (I made it my job to run the car that much because I had big hopes and dreams of finding myself in Grand-Am, but my BMW racing career only made to winning a NASA GTS national championship haha. Maybe I’ll buy a pro seat one day).

I did break a stud on my Spec Miata and the wheel went flying off during an enduro... sadly I over torqued the wheel by a lot... things I learned transitioning from BMW racing to Spec Miata... zoom zoom!

Side note: The option we are looking at are the complete Future Classic hub conversion with M14 BimmerWorld studs. We will need to install within the next 1-2 weeks so we can put a new set of MCS 3-ways (Hellz Yeah!) and move the car to paint shop!

[ThunderMoose]

Originally Posted by ryanosiecki

These are great explanations! Love the discussion here, everyone. I really appreciate this!!!

Just curious... are the findings more chassis specific? I only ask because I tracked / raced an e46 M3 for years putting over 2,000 miles per month on track and never once broke a stud. We had some come loose over time, but that was it. We ran a mix of Fall-Line and BimmerWorld studs exchanging studs every season. We torqued them to 82 ft/lbs at every event and only when it was completely cooled down. (I made it my job to run the car that much because I had big hopes and dreams of finding myself in Grand-Am, but my BMW racing career only made to winning a NASA GTS national championship haha. Maybe I'll buy a pro seat one day).

I did break a stud on my Spec Miata and the wheel went flying off during an enduro... sadly I over torqued the wheel by a lot... things I learned transitioning from BMW racing to Spec Miata... zoom zoom!

Side note: The option we are looking at are the complete Future Classic hub conversion with M14 BimmerWorld studs. We will need to install within the next 1-2 weeks so we can put a new set of MCS 3-ways (Hellz Yeah!) and move the car to paint shop!

I believe there is something inherently different with E9x chassis. After 10 years in my E46 the last 4 of which with full aero and A7's and some TT3 track records I have yet to break a stud. I typically replace studs every 2-3 years.

[rhyary]

To add my .02 cents.
I chose Future Classic solution.
The front is very simple.
The rears are a major job, time wise.
So for the rear, DIY is no major expense, but to pay for install is expensive.

So if you plan to do rear FC solution, you want to do solid subframe bushings at the same time. And vice a versa, if you want to do (need to do) Solid subframe, think about FC rear.

But while you are in there, don't forget the diff bushings.

It is much cheaper for non DIY to do all these as one job because all involved taking lots of the same rear parts apart.

[admranger]

Originally Posted by ThunderMoose

I believe there is something inherently different with E9x chassis. After 10 years in my E46 the last 4 of which with full aero and A7's and some TT3 track records I have yet to break a stud. I typically replace studs every 2-3 years.

It’s fat and has 100 more hp. Other than that there’s nothing wrong with it.

I broke studs on my E36M3 club race car. It happens.

Buy some left handed drill bits and an extractor set. Good ones. Worked well but I didn’t have grade 12.9 studs.

[ThunderMoose]

Originally Posted by admranger

It’s fat and has 100 more hp. Other than that there’s nothing wrong with it.

I broke studs on my E36M3 club race car. It happens.

Buy some left handed drill bits and an extractor set. Good ones. Worked well but I didn’t have grade 12.9 studs.

How many studs have you broken in all you time racing?

[admranger]

Originally Posted by ThunderMoose

How many studs have you broken in all you time racing?

2. Willow springs.

Replaced all 20 before the next event.

I attribute that to the fact I bought an expensive left handed drill bit and extractor set (name brand tool truck kit) so I’d never need to use it to take out a stud.

[gills]

There's nothing inherently different with the E9x chassis other than what admranger said. Weight and power, that's all. The hubs used on BMW's are shared across many chassis with minor differences.

Thread-in studs break the same across all BMW chassis' and most of the time on a rear corner, NOT the front. I'd say 80-85% of the stud failures shared with me are from a rear corner and over 50% WITHOUT wheel spacers, much to the disbelief of many.

As I've said before, the rear corners are dealing with engine torque AND brake torque (and supporting corner weight), which are forces that act laterally/perpendicular to the studs. This lateral/perpendicular cyclical loading is a BENDING stress cycle for the wheel studs.

This type of load scenario is also the recipe to cause nuts to loosen. What is the best method to prevent loosening and minimize bending stress? Having sufficiently tensioned wheel studs!

I keep saying the studs are bending. What the hell is bending? Envision "bending" to be with the wheel off and the studs exposed, push on the side of the stud with your finger as hard as you can, it'll want to "bend" and is anchored/cantilevered where it installs into the wheel hub.

It's not hard to imagine where the peak stresses will be and why thread-in studs break the way they do; almost always inside the wheel hub or flush with the face. In the fastener engineering world, it's a fundamental design flaw to have thread transition areas (threaded portion of stud to un-threaded shoulder so thread-in studs can bottom out at the hub) and thread roots subjected to bending and why they are much more prone to failure vs. a press-in.


ryanosiecki, you mentioned you over torqued the Miata wheel stud. Did you send the stud out to have the fracture face analyzed? Even without ever seeing it, I can almost guarantee that you didn't overwhelm or stretch them from torquing, especially if they were ARP studs.

I also believe that the hot torquing thing is myth perpetuated in the thread-in stud world. Call ARP or MSI yourselves and they will tell you that professional race teams never bring this up. I will argue that risking having insufficient stud preload with things hot is far more dangerous than checking torque when hot.

People also think that wheel studs will stretch more once things are at an elevated temperature due to thermal expansion, or if you tighten when hot, they will overstretch once things cool down. In my testing I took a mockup assembly of a hub with studs, rotor, and center portion of a wheel fully torqued and heated it to 350F for 1 hour (which is hotter than reality). Not only was there never an increase in stud stretch, they would actually tend to LOSE stretch.

In the cases where I put more torque on the lug nuts after coming out of the oven then let them cool, there was never an increase in stretch. They were exactly the same as when I put them in the oven.

[ThunderMoose]

Originally Posted by gills

There's nothing inherently different with the E9x chassis other than what admranger said. Weight and power, that's all. The hubs used on BMW's are shared across many chassis with minor differences.

Thread-in studs break the same across all BMW chassis' and most of the time on a rear corner, NOT the front. I'd say 80-85% of the stud failures shared with me are from a rear corner and over 50% WITHOUT wheel spacers, much to the disbelief of many.

As I've said before, the rear corners are dealing with engine torque AND brake torque (and supporting corner weight), which are forces that act laterally/perpendicular to the studs. This lateral/perpendicular cyclical loading is a BENDING stress cycle for the wheel studs.

This type of load scenario is also the recipe to cause nuts to loosen. What is the best method to prevent loosening and minimize bending stress? Having sufficiently tensioned wheel studs!

I keep saying the studs are bending. What the hell is bending? Envision "bending" to be with the wheel off and the studs exposed, push on the side of the stud with your finger as hard as you can, it'll want to "bend" and is anchored/cantilevered where it installs into the wheel hub.

It's not hard to imagine where the peak stresses will be and why thread-in studs break the way they do; almost always inside the wheel hub or flush with the face. In the fastener engineering world, it's a fundamental design flaw to have thread transition areas (threaded portion of stud to un-threaded shoulder so thread-in studs can bottom out at the hub) and thread roots subjected to bending and why they are much more prone to failure vs. a press-in.


ryanosiecki, you mentioned you over torqued the Miata wheel stud. Did you send the stud out to have the fracture face analyzed? Even without ever seeing it, I can almost guarantee that you didn't overwhelm or stretch them from torquing, especially if they were ARP studs.

I also believe that the hot torquing thing is myth perpetuated in the thread-in stud world. Call ARP or MSI yourselves and they will tell you that professional race teams never bring this up. I will argue that risking having insufficient stud preload with things hot is far more dangerous than checking torque when hot.

People also think that wheel studs will stretch more once things are at an elevated temperature due to thermal expansion, or if you tighten when hot, they will overstretch once things cool down. In my testing I took a mockup assembly of a hub with studs, rotor, and center portion of a wheel fully torqued and heated it to 350F for 1 hour (which is hotter than reality). Not only was there never an increase in stud stretch, they would actually tend to LOSE stretch.

In the cases where I put more torque on the lug nuts after coming out of the oven then let them cool, there was never an increase in stretch. They were exactly the same as when I put them in the oven.

I guess I still don't understand why I don't hear about the number of stud failures on E46 chassis that I see on this forum. I am around guys that are racing hard on slicks with aero pounding curbs at tracks like WGI and rarely have any issues.

[gills]

Originally Posted by ThunderMoose

I guess I still don't understand why I don't hear about the number of stud failures on E46 chassis that I see on this forum. I am around guys that are racing hard on slicks with aero pounding curbs at tracks like WGI and rarely have any issues.

WGI is actually very smooth relative to other tracks. Also, session duration seems to be a factor. Shorter sessions have less incidents, although it still does happen.

Personally, I've experienced 2 or 3 E46's that have broken wheel studs in AER race weekends. One of them breaking 14mm thread-in studs on the left rear using Rogue's drill jig kit. We're limited to 200TW tires in AER also.

As I've said before, an assembled "wheel joint" has pretty large safety factor so these things don't happen more than they do, but they happen more with thread-in/screw-in stud cars than they do press-in stud cars.

I forgot to mention that the E9x M data I have seems to favor the fronts failing. My intuition says this is the extra weight that is being dealt with that can be overcoming the friction interface of the wheel-rotor-hub and putting 100% of the bending stress on the studs once that happens. The fracture face of the studs in these cases still show bending fatigue failure.

[ThunderMoose]

Originally Posted by gills

WGI is actually very smooth relative to other tracks. Also, session duration seems to be a factor. Shorter sessions have less incidents, although it still does happen.

Personally, I've experienced 2 or 3 E46's that have broken wheel studs in AER race weekends. One of them breaking 14mm thread-in studs on the left rear using Rogue's drill jig kit. We're limited to 200TW tires in AER also.

As I've said before, an assembled "wheel joint" has pretty large safety factor so these things don't happen more than they do, but they happen more with thread-in/screw-in stud cars than they do press-in stud cars.

I forgot to mention that the E9x M data I have seems to favor the fronts failing. My intuition says this is the extra weight that is being dealt with that can be overcoming the friction interface of the wheel-rotor-hub and putting 100% of the bending stress on the studs once that happens. The fracture face of the studs in these cases still show bending fatigue failure.

Thanks for everything you've share on this subject. It's been incredibly informative.

[rTrackM3]

First and foremost, I hope everyone is in good health here. It is not news to anyone, but these last few weeks have been difficult for a lot of folks around the world. No doubt, the focus of my track car project has drifted during this pandemic. I am very grateful to be part of this community and for providing an outlet to escape reality right now.

Here is the latest... I don't have any updates on the build pre se, but I have conceded on this hub discussion. Initially I was going to time-out and replace my M12 thread-in studs and replace the OE hubs. Then I was considering the Future Classic M14 thread-in stud with F8X hub conversion. Finally, with more research I started to drink the koolaid on this press-in stud concept. So... I went ahead with best of both worlds (IMO) - M14 Press-in studs with F8X rear hubs from Core4 Motorsports.

I am sure many of you share the same experience... I have not had any issues with my M12 thread-in studs regardless of brand. My rationale to go with this setup was mainly for added insurance and the lighter weight hubs are a nice performance bonus. I believe the weights savings are 0.5lbs per corner in the rear, but correct me if I am wrong. In addition, they are reasonably priced and as you can tell by this thread and others, the customer support I have received from C4 is worth every penny. So if you're more of an evidenced based person or just want further education send a private message to "Gills" for more information. Also, if you are planning ahead, these were not an overnight delivery. The M14 studs they use are in low supply so anticipate 4-6 week lead time.

Full disclosure I have no vested interest in C4Motorports and have no financial incentive to writing this. This is my experience that is worth sharing. Especially when this failure could result in serious injury and best case a damaged BMW

[rTrackM3]

Say Cheese!!!!!!!

[rTrackM3]

Front and Rear.... Dogbone usually wins the style points on these pictures

[dogbone]

Originally Posted by ryanosiecki

Dogbone usually wins the style points on these pictures

haha! I don't think I've ever won style points for anything before!

Are the new hubs on the car yet?

[gills]

Thanks for sharing, Ryan (and Dogbone in his build thread).

Just want to make clear if it's not obvious that the fronts are OE E9x M3 hubs and the rears are from F8x. I don't have pricing truly set in stone yet for this as Dogbone and Ryan are the first to give this a go, but going this route will be significantly cheaper (hundreds) than "that" other kit.

As for M14 stud supply, I currently have enough in stock to make either 1 or 2 more sets if anyone reading is interested. MSI is backlogged with M14's at the moment and I'm not quite sure yet what the demand is for this solution. If anyone else is interested, please let me know and do not hesitate to reach out to me with any questions whatsoever.


-Tom

[rTrackM3]

Originally Posted by dogbone

haha! I don't think I've ever won style points for anything before!

Are the new hubs on the car yet?

It's a-coming!

[rTrackM3]

A-Pillar

[rTrackM3]

Trunk

[rTrackM3]

Door Bars

[dogbone]

Very nice!!

[tsk94]

Nice! I like the door bar design

[rTrackM3]

Originally Posted by dogbone

Very nice!!

Thank you!

Originally Posted by tsk94

Nice! I like the door bar design

Thanks! It was the builders (Autocore Performance Group) idea. Can not wait to see it with the gussets and 'IMSA' bar... and painted!