Track forum general chit chat.

Rear subframe MUST be lowered to gain access to the sway bar and have enough room to rotate it and slide it out

Also a large rear bar should increase oversteer as it effectively is increasing rear spring rate....not induce understeer

kolosy after driving a caged m3, which ultimately removed a significant amount of rear weight, that didn't allow enough weight transfer to the rear on corner entry to increase forward grip.

My solution was to not plunk down 5k on damper, but just to adapt an APR GTC wing. In my opinion, it adds to much downforce at the rear at zero AOA without a proper splitter..but if you have a GT4 3 inch fake splitter (aka lip) and proper under body panels (like a turner) it's a start.
There is mainly way too much front weight on the M3

RalliartRsX wrote

kolosy after driving a caged m3, which ultimately removed a significant amount of rear weight, that didn't allow enough weight transfer to the rear on corner entry to increase forward grip.

My solution was to not plunk down 5k on damper, but just to adapt an APR GTC wing. In my opinion, it adds to much downforce at the rear at zero AOA without a proper splitter..but if you have a GT4 3 inch fake splitter (aka lip) and proper under body panels (like a turner) it's a start.
There is mainly way too much front weight on the M3

What’s interesting about that is that the day I noticed the understeer was the first day I was running the new wing. 72” wing logic swan neck. And I’ve got the fake splitter and an mporium under tray. I’m not saying the wing caused it, it didn’t. That just happened to be the day it clicked for me.

A 72 inch swan neck wing will undoubtedly introduce a ton of understeer..... especially without any real front aero

The fake lip and under panel down really don't add much in the way of downforce. Especially if the lip mounted to the bumper.... like 90% of the lips out there

A true splitter with a 72 inch wing is the proper balance. As I recall, a 71 inch wing is right at body width. Also I'll assume it's either a 9, 9.5 or 12 inch chord. All 3 of which has shifted the balance well to the rear....

It always drives me nuts when folks just show up to the track with a shadow setup of what they saw online

I spent an entire year sans aero just pounding laps and making minor changes to the car once I baselined the setup without aero . That allowed me to more understand the dynamics of the car (long wheel base, so rotation occurs slowly, limited weight in the rear, turn in point, speed differential, corner exit oversteer etc etc)

My recommendation; ditch the wing and lip and re baseline by pounding laps.

Here are two videos from myself

The first is without wing and turner under panel and GT4 lip (you can see just how much steering input is needed with the well used square 275 v730s)
Second video is with square CRS v1 275, heat cycled by Phil's, Rear APR 67inch wing. GT4 lip and turner panel.

RalliartRsX wrote

Here are two videos from myself

The first is without wing and turner under panel and GT4 lip (you can see just how much steering input is needed with the well used square 275 v730s)
Second video is with square CRS v1 275, heat cycled by Phil's, Rear APR 67inch wing. GT4 lip and turner panel.

Dont brake before T4, just lift and send it

RalliartRsX wrote

A 72 inch swan neck wing will undoubtedly introduce a ton of understeer..... especially without any real front aero

The fake lip and under panel down really don't add much in the way of downforce. Especially if the lip mounted to the bumper.... like 90% of the lips out there

A true splitter with a 72 inch wing is the proper balance. As I recall, a 71 inch wing is right at body width. Also I'll assume it's either a 9, 9.5 or 12 inch chord. All 3 of which has shifted the balance well to the rear....

It always drives me nuts when folks just show up to the track with a shadow setup of what they saw online

I spent an entire year sans aero just pounding laps and making minor changes to the car once I baselined the setup without aero . That allowed me to more understand the dynamics of the car (long wheel base, so rotation occurs slowly, limited weight in the rear, turn in point, speed differential, corner exit oversteer etc etc)

My recommendation; ditch the wing and lip and re baseline by pounding laps.

Appreciate the advice but not the insinuation that I just slapped all this crap together because it looks cool and sent it. I’ve spent 3 seasons in this car tracking it and building it out gradually. I added the aero this season. Don’t claim to be an expert it but I’m learning (and yeah, once you said it it of course made sense that too much rear downforce without balanced front will cause understeer).

Are there “real” splitter options that aren’t the full bore $3K Zebulon kit? The GT4 lip I have is about 4” out, but yeah it’s attached to the bumper. Does adding supports to it change anything?

I guess I can also try decreasing the aoa on the wing. I don’t want to ditch it entirely because of the new weight distribution.

Even at zero AOA, the 71" ,wing is generating significantly more downforce than the 4" GT4 lip attached to the bumper will ever produce. Also it isn't the attachment that generates the downforce. It's the actually pressure and speed differential of airflow across the area of the splitter. Which means; the lower portion need for extend to atleast the front axle line and be mounted to the chassis for any meaningful downforce to be produced and for that downforce to act across the front axle.. More splitter area also equals more downforce

You can build your own splitter utilizing the GT4 lip and mPorium panel as a template and utilize the professional awesome splitters mounts and brackets

Or spendy on a fancy splitter from Zebulon or similar

Sorry wasn't trying to be snarky.

kolosy wrote

Appreciate the advice but not the insinuation that I just slapped all this crap together because it looks cool and sent it. I’ve spent 3 seasons in this car tracking it and building it out gradually. I added the aero this season. Don’t claim to be an expert it but I’m learning (and yeah, once you said it it of course made sense that too much rear downforce without balanced front will cause understeer).

Are there “real” splitter options that aren’t the full bore $3K Zebulon kit? The GT4 lip I have is about 4” out, but yeah it’s attached to the bumper. Does adding supports to it change anything?

I guess I can also try decreasing the aoa on the wing. I don’t want to ditch it entirely because of the new weight distribution.

i bet you could build a "custom" splitter for less than $1k.... go buy some cheap particle board or wainscoting from home depot and trace it out. i'd bolt it to the front subframe via the factory bolt locations, and hang the front with some steel wire off the front crashbar.
ship the cutout you come up with to racebred components and have them do a custom wood splitter... add some endplates and tunnels if you want to get fancy.
https://racebredcomponents.com/collections/front-splitter-blades

i had a small universal apr lip with the oem performance "fangs" for a while and i feel like it just busied up the front end... i have to figure out front aero soon and i don't think i want to sandwich the gt4 lip between the bumper and splitter. it is probably better than nothing, but all kinds of sandwiching just adds things to flex, adds cracks, holes, and drag. there was a company called Revinora that made a very nice "street chin" that made the bottom of the m3 bumper completely flat when it was installed. unfortunately, they are out of business.
i'd say a gt4 lip attached to a bumper is better than nothing, but probably not enough to balance out a huge wing... hard to say depending on the AOA of your wing.
i'm likely going to go the racebred route... i can't do the $3k splitter thing just to rip it off if i make too big of a mistake.

roastbeef wrote

i bet you could build a "custom" splitter for less than $1k.... go buy some cheap particle board or wainscoting from home depot and trace it out.

I would recommend starting with plywood (birch is preferred). Make the cutout around the tires, mount the entire sheet, mark the leading edge cut line and saw away. Actually a router makes the process WAY easier. Then make 1 or 2 spares. Don't use aluminum to mount the splitter, it doesn't last and is not durable enough. Steel!

I recommend plywood because there is a learning process to drive around with a splitter. You'll likely hit and scrape the splitter on things like trailer ramps, low spots, speed bumps, etc. On my E46, I broke a plywood splitter by banging it on a 2 post lift while pulling in, going through a drainage low spot in the paddock where I have never scraped before, and had an aluminum mounting bend and fail.

Once you get it down with the plywood, get a carbon splitter. Carbon in this application has a significant performance advantage. My splitter is 3 years old and has only needed 1 minor repair.

RalliartRsX wrote

Even at zero AOA, the 71" ,wing is generating significantly more downforce than the 4" GT4 lip attached to the bumper will ever produce. Also it isn't the attachment that generates the downforce. It's the actually pressure and speed differential of airflow across the area of the splitter. Which means; the lower portion need for extend to atleast the front axle line and be mounted to the chassis for any meaningful downforce to be produced and for that downforce to act across the front axle.. More splitter area also equals more downforce

You can build your own splitter utilizing the GT4 lip and mPorium panel as a template and utilize the professional awesome splitters mounts and brackets

Or spendy on a fancy splitter from Zebulon or similar ��

Sorry wasn't trying to be snarky.

Bolting on more downforce isn't always the answer. It depends on what speed the understeer is occurring. Lower speeds would indicate it is more of a mechanical grip issue and not an aero imbalance. Downforce increases with the square of the speed. So the inverse is also true, half the speed then downforce exponentially decreases.

So if he is having low speed understeer bolting on a large splitter is the wrong answer. It leads people to put canards, tunnels, tire spats and anything else they can put on that claims to increase downforce which leads to more high speed oversteer which then leads to an AOA adjustment or a gurney flap.

I learned this the hard way, when you take a bunch of weight out of the car, there is less weight transfer forward under braking so the car may stop better but trail braking at turn in may cause understeer. Typically, a softer front spring will decrease understeer. Can also try more front negative camber or less rear negative camber.

I do think I’m having low speed understeer more so than high speed, but I will pay closer attention to it next time I’m out. I can also do the sway bar disconnect suggested, as well as play around with aoa.

Back on splitters for a second — so is the issue with the typical GT4 splitter that it’s not a smooth surface from leading edge all the way back? Or that it’s not supported well enough and just deflects instead of pushing the car down? Or that it doesn’t come far enough forward? Or all of the above?

kolosy wrote

Back on splitters for a second — so is the issue with the typical GT4 splitter that it’s not a smooth surface from leading edge all the way back? Or that it’s not supported well enough and just deflects instead of pushing the car down? Or that it doesn’t come far enough forward? Or all of the above?

i think the theory with a gt4 style splitter is it isn't going to work two ways... it is going to create an airdam at the bottom of the bumper, but it doesn't go back far enough to create a low pressure zone under the front axle. basically, underbody aero will sort of be a mess, especially with the oil cooler duct exit.
it will still do some work being mounted to the front bumper. these bumpers are pretty stout as they are mounted, plus the wire hangers add some stability. just know it is going to flex a little bit.

please consider that this is just theory based on what i've read and continue to learn about. i have ideas, but i'm not out here building splitters.

roastbeef wrote

i think the theory with a gt4 style splitter is it isn't going to work two ways... it is going to create an airdam at the bottom of the bumper, but it doesn't go back far enough to create a low pressure zone under the front axle. basically, underbody aero will sort of be a mess, especially with the oil cooler duct exit.
it will still do some work being mounted to the front bumper. these bumpers are pretty stout as they are mounted, plus the wire hangers add some stability. just know it is going to flex a little bit.

please consider that this is just theory based on what i've read and continue to learn about. i have ideas, but i'm not out here building splitters.

The air going over the lip is probably going across the bumper and then exiting down the side of the car. If you can get more clean flow, there might be more extraction from the wheel well.

I still think the GT4 lip does slightly lower the pressure under the lip which would improve extraction from the oil cooler. In no way does it compare to a large splitter but I'd have a hard time believing that the GTS was worse aerodynamically than a stock M3.

bigjae1976 wrote

The air going over the lip is probably going across the bumper and then exiting down the side of the car. If you can get more clean flow, there might be more extraction from the wheel well.

I still think the GT4 lip does slightly lower the pressure under the lip which would improve extraction from the oil cooler. In no way does it compare to a large splitter but I'd have a hard time believing that the GTS was worse aerodynamically than a stock M3.

i agree.

i guess i didn't put my words down correctly... it is definitely better than nothing, but a splitter that reaches farther back is more ideal.

Downforce is a pressure differential. Airflow at various speeds across a surface exerts a pressure that's inversely proportional to velocity

Meaning; you want to accelerate the airflow underneath the car to decrease the vertical (upward ) component of the pressure. Combination of Bernoulli's and ground effect.

A splitter acts on similar principle.The function of the splitter is to direct and accelerate airflow underneath and over the upper surface. That's why it's called a splitter; it splits the airflow above and below the vehicle
That's why a splitter attached to a bumper has negligible effects as once it's past it's trailing edge (about 4 inches in the GT4 case), the air becomes detached and turbulent if it doesn't have a consistent surface. Which in turn, means the airflow actually stagnates (stops accelerating) and you lose all your suction (ground effect or downforce)

I ran a home made splitter for a few years before upgrading to my current Zebulon setup. Fairly straight forward to build. I used 1/2" birch. Used standoffs bolted into the subframe bolt areas as my rear chassis mounts. The front was held by four splitter rods going to the bumper beam. I did add additional supports to the outside ends after cutting in some diffusers but you you could skip them.

I ran this setup with a 72" swan neck Nine Lives wing and it was fairly balanced. Switching to the Zebulon splitter threw it out of wack and I just upgraded to a much larger rear wing to bring balance back to the car.

This setup was good for a 1.17 at summit and 1.59 at VIR in TT3 trim.

turbo_joe wrote

I ran a home made splitter for a few years before upgrading to my current Zebulon setup. Fairly straight forward to build. I used 1/2" birch. Used standoffs bolted into the subframe bolt areas as my rear chassis mounts. The front was held by four splitter rods going to the bumper beam. I did add additional supports to the outside ends after cutting in some diffusers but you you could skip them.

I ran this setup with a 72" swan neck Nine Lives wing and it was fairly balanced. Switching to the Zebulon splitter threw it out of wack and I just upgraded to a much larger rear wing to bring balance back to the car.

This setup was good for a 1.17 at summit and 1.59 at VIR in TT3 trim.

Interesting.. no issues with not having the oil cooler venting open? Do run brake ducts? And I think my wing logic wing is pretty close to the 9L one. The occams racer guy compared them and they were largely equivalent.

kolosy wrote

Interesting.. no issues with not having the oil cooler venting open? Do run brake ducts? And I think my wing logic wing is pretty close to the 9L one. The occams racer guy compared them and they were largely equivalent.

Zebulon doesn’t have an oil cooler vent either.

Hey track gurus! Rookie question. I have done a TON of searching but a lot of the information out there is old (products have changed names / compounds) and may no longer be accurate, or I found so many conflicting suggestions, so wanted to get the 2025 "latest".

I am taking my E92 M3 to it's first HPDE at NJMP Thunderbolt track in a few weeks (6/15), and is my 2nd time on track (first was in a G80). I have fully stock brakes, rotors, and pads. I am planning to get a fresh Motul 600 brake line flush at the least. I am also debating getting a set of either dedicated track pads, or an 'in-betweener' brake pad that can do both light track duty + street. Some people have suggested I could stick with OEM pads for my first few track days but it sounds like I run the risk of being unable to fully participate if I overheat them. I have mentally acquiesced to having to swap pads between street/track and re-bed them each time but if you think overkill for my usage, let me know.

If I wanted to get a dedicated track pad, is EBC Bluestuff still a popular/respectable choice? (and if so, it would be these two on FCP right? Fronts and rears ).

I live in NYC and use the car only on weekends and *hope* to get to the track 3-4 times per year if i can (Lime Rock, NJ Motorsports Park, Monticello, Thompson). My goal is to pump that number up if I can get a handle on consumables / logistics.

kolosy wrote

Interesting.. no issues with not having the oil cooler venting open? Do run brake ducts? And I think my wing logic wing is pretty close to the 9L one. The occams racer guy compared them and they were largely equivalent.

I havent run an oil cooler vent in about 5 years and its never been an issue. I do not run brake ducts either but I run the BW/Alcon Nickel BBK. Venting the oil cooler under the car is counteractive to even running a splitter. You dont want to dump air back under the car, especially in the middle of your splitter,

I also have a do88 oil cooler that made a nice difference in oil temps.

Eric335 wrote

Hey track gurus! Rookie question. I have done a TON of searching but a lot of the information out there is old (products have changed names / compounds) and may no longer be accurate, or I found so many conflicting suggestions, so wanted to get the 2025 "latest".

I am taking my E92 M3 to it's first HPDE at NJMP Thunderbolt track in a few weeks (6/15), and is my 2nd time on track (first was in a G80). I have fully stock brakes, rotors, and pads. I am planning to get a fresh Motul 600 brake line flush at the least. I am also debating getting a set of either dedicated track pads, or an 'in-betweener' brake pad that can do both light track duty + street. Some people have suggested I could stick with OEM pads for my first few track days but it sounds like I run the risk of being unable to fully participate if I overheat them. I have mentally acquiesced to having to swap pads between street/track and re-bed them each time but if you think overkill for my usage, let me know.

If I wanted to get a dedicated track pad, is EBC Bluestuff still a popular/respectable choice? (and if so, it would be these two on FCP right? Fronts and rears ).

I live in NYC and use the car only on weekends and *hope* to get to the track 3-4 times per year if i can (Lime Rock, NJ Motorsports Park, Monticello, Thompson). My goal is to pump that number up if I can get a handle on consumables / logistics.

Get dedicated track pads for sure. And I would avoid EBC pads, they are junk IMO. Feel free to DM me if you want some input on pads.