Everything about Fat Cat Motorsport Suspension

[maupineda]

Some data to entertain

Regular E46 M3


CSL M3



Rears are

Regular
587mm - 18" rim
600mm - 19" rim

CSL
589mm - 18" rim
602mm - 19" rim

Yes, surprisingly the CSL is 2mm higher at the rear V Regular M3

Based on the above, I assume the shock travel for the E46 is the same, in fact, it seems that the Z4M is taller (2mm at 607 at the front and 7mm at the rear at 594)

I hope this is useful, someone with actual E46 M3 Billies should confirm in the name of data.

[Obioban]

IIRC the Z4M can have a bit more travel.

[K-Dawg]

Makes sense. The Z4 shock body doesn't have to fit down in the kingpin, which is why monotube's on the E46 M are travel limited.

[Cronenberged]

After 15 years of various adjustable shocks (up to quad adjustable remote reservoir JRZs)... it's honestly been pretty great to not be thinking about adjusting the shocks. The shocks are valved for my spring rates and corner weights, so likely I'd just make it worse anyway.

I've also idiot proofed my tire pressures, with the Michelin track connect setup... so all I really have to think about is camber (which I set via pyrometer).

It's relaxing

What height do you have your car set to?

[E46m3zcp]

EDIT: I am technically inclined and an engineer in the field of automotive, but I am not a suspension expert. What I am commenting on here is what I learned from a research driven by my curiosity and if anyone has additional information I will be happy to learn more.

It's not really clear what FCM means by front/rear bounce rate. From what I know (reference below), the bounce rate is related to how we derive the bounce and pitch frequencies and centers for the coupled front-rear vertical motion of a car. There is not a front and a rear bounce rate. There is just a bounce rate.

The vehicle bounces (up and down) and oscillates (rocks back and forth) about a bounce center and a pitch center, respectively, at a bounce frequency and a pitch frequency. These two modes are superposed to give the final motion. Given the specifications of the vehicle, one can calculate the centers and frequencies and these properties have an impact on comfort.

Cars have higher spring rates in the rear than in the front because it minimizes the pitch motion which is the most annoying mode. According to design principles, not only should the rear rate be higher, but it has to be 30% higher - or the spring center should be at least 6.5% of the wheelbase behind the CG. There are also other guidelines as quoted below. So the "Flat Ride" concept might be vaguely related to these guidelines but it isn't 100% defined by them. "Flat Ride" isn't something that's defined in any vehicle dynamics textbooks, as far as I know.

These principles affect only the ride quality and are unrelated to the cornering ability. I think it is safe to say that cornering ability usually comes at the cost of ride comfort.

Here are the derived design principles from the source mentioned below:



Source: Gillespie, Thomas D., fundamentals of vehicle dynamics (relevant chapter available here: https://edisciplinas.usp.br/mod/reso...php?id=2960518
The relevant portion starts on page 175).

And since I said this was not related to cornering ability, here is a quote from a famous book (Tune to Win, Caroll Smith) about what an experienced racing engineer had to say about spring frequencies.

[cobra]

E46m3zcp Interesting research. Here are my thoughts...
-Good handling and ride comfort are not mutually exclusive. Maybe people think that stiff=sporty=good handling, but this is simply not the case. Many well set up cars are both comfortable and corner faster than their lowered, bouncy counterpart.
-Flat ride isn't well documented in vehicle dynamics books because it's short sighted. You can't just take a vehicle that we think is cool and say "this is correct, therefore all vehicles must have this parameter". Auto engineers are hindered by compromises and safety standards. Take one of those auto engineers and tell them to design the vehicle with no regard for standards, regulations, or marketing and I bet it will look a lot different.
-The comment on spring frequency is true when chasing perfection, but to completely ignore the basic physics of the system is also silly. For most of us here we can do pretty well for a street setup with some calculations.

I am interested in the pitch and bounce frequency, gonna read up more on those!

[bigjae46]

I’m not an expert on the engineering.

This has been my experience. I went from 600/700lb springs at 3000 lbs to 2650lbs. At 3000lbs, the car was well balanced, maybe a tad bit oversteery. At 2650lbs the car was great on smooth tracks. It was horrible on bumpy tracks. I’d literally have to slow to a crawl to get the car to turn in on low speed corners. I was slower than when the car was at 3000lbs.

Flat ride calculated 350/700. Went 400/700 which I think put me at 1.05hz. It was transformative. I’ve since put on 450 springs on the front with no real change in balance. Maybe it could be better but I’m within 1-2 seconds of NASA TT3 records on RRs. And I’ve deleted the rear sway bar and added aero.

I don’t think flat ride is an answer. More of a starting point. I would have spent a lot more time tuning the suspension if I didn’t have the FCM calculator. I think it turns a lot of people off since it goes against common BMW setups.

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[BigDave]

Thanks for the thread and support, gents. However some information is inaccurate and needs correction. Importantly: my consulting rate is $250 per hour and has been for several years. The $125 he's referring to is for a 30 min consultation, which is required. Additional consulting depends upon the number of specific details we need to cover when designing your Elite suspension.

Also, I am returning to my earlier practices of keeping shock dyno data private. I will no longer transmit it electronically or provide printouts. If you come to FCM headquarters, I can show you your final graphs. That's more than any top chef would do! The proof is in the tasting.

Finally, KBO is NOT like Ohlins DFV. Ohlins DFV does no appreciate 'high speed compression' blow-off. Compare this graph and a earlier FCM Elite KBO vs. an Ohlins DFV. The compression blow-off on the Ohlins is like a digressive, vs. the ACTUALLY flatter blow-off of the KBO!




The 'dual flow valve' is doing NOTHING to reduce high speed slope in any way that appears beneficial, certainly not for actual 'curb absorption.' The Kerb Blow-Off technology I have developed assist in truly reducing the high speed compression force build-up and must also be combined with appropriate reduction of high-speed rebound force to minimize jacking down. This is why it's more than just the 'blow-off' on compression that you need, but also a related 'blow-off' on rebound. So it's more correct to describe this as KBO / UltraD (Ultra Digressive) or what I'm pretty much just calling 'FCM Elite Ultimate.'

More accurately, KBO was inspired through my studies of the Penske's regressive valve (initially used on Formula 1 cars to help soften the vertical upset to the chassis from curb strikes at very high road speeds) when designing my Kerb Blow-Off valve. I have actually developed a regressive version of the KBO which I will eventually put on Christina in combination with other technologies. I began with developing a flat blow-off (which is what KBO gives you) and then continued my research and development into a 'regressive' blow-off, like the Penske regressive valve.

===

FCM Elite Stage 2 is still very well-optimized (it includes Ripple Reducer) and I'm careful to tune the compression and rebound forces to minimize jacking down (excessive rebound) and launching (excessive compression). An FCM Elite Stage 2 build is superior to any product on the market.

For those who want the best of everything, you'll want FCM Elite Stage 3 Ultimate. I can use my full arsenal of technologies and methods that help me optimize the suspension's response at a VERY wide range of road conditions - from lightly rippled roads to medium-sized rollers, to large 'bottom the suspension' kinds of bumps.

I've spent much of the spring and summer refining my methods beyond what I have in Youtube videos - so while the video on KBO does represent some of the behavior I aim for, there's more going on than just KBO.

===

A key point I need to communicate is that I am unlike what you would consider an 'aftermarket suspension vendor.' I create solutions, instead of selling parts. I take your specific, unique needs into account when designing a solution instead of trying to squeeze some off-the-shelf collection of parts into your car. I look at the entire suspension as thoroughly as I can and ensure each key component is considered and changed as required. This can't be overstated! Even using terms like KBO or Ripple Reducer only tells part of the story, as EACH BUILD gets a unique implementation of these technologies! As car weights, spring rates, driver usage, tires / wheels / aero, etc. all differ, how I integrate each technology is different. This is like being taught the basics of a dance step, or a workout routine, and then making your own variations.

The major problem I see with a majority of aftermarket tuners is they make a PART or a KIT and then try to push YOU into their box. I first look at what YOU need, then sculpt and refine the ideas and methods into a final result. This is literally a NEW CREATION for every build!

Their "sell as many parts as we can" approach creates a chaotic experience, and it even sucks for race cars. Ask duracellttu what he thinks of the TC Kline he's partially removed from his car, and what he felt in driving Christina (he was one of a lucky few to get that privilege).

===

Duracellttu is changing from single-adjustable TC Klines and these are two videos I made to show him why his driving experience in Christina was so much more supple and composed than the TC Klines:

E46 M3 TC Kline front dyno tests

E46 M3 TC Kline rear dyno tests

I'll look forward to adding his FCM Elite Stage 3 testimonials to this page, and to the website! Then Ian's later on
===

If you are curious about why there are testimonials like this:

then you can educate yourself on some of the methods I am using. The 3 Keys of Ride Harmony (VIDEO) is fundamental. As duracell points out the importance of Flat Ride being the foundation of every FCM Elite build.

And most importantly, get in touch! Refer to the FatCatMotorsports.com website and words directly from me rather than any forum post for specifics on my current business practices. Each thread that particularly inspires you, I want to hear about when you contact me. As always, big thanks to Ian for creating this new forum.

Cheers,
Shaikh

P.S. I'm going to send duracellttu an email with additional needed corrections. As he's a cool guy and already has a set of H&Rs with me for a Stage 3 build, it's all friendly.

I have TCK single adjustable front and rear. I am VERY disappointed. They dont stabilize the car well after 130MPH.

Great suspension should stabile our E46 M3 on rippled pavement even at 175mph. My custom Penske four way adjustable rear shock was MAGIC on my Honda Blackbird motorcycle at 180MPH. Unbelievable stability when high speed/low speed dampening was tuned properly. Once I tuned the shock, I never had to change it for any different type of pavement. Did perfect on the track AND the street!

I want that type ultra high speed stability and versatility for my M3!!!

[BigDave]

After 15 years of various adjustable shocks (up to quad adjustable remote reservoir JRZs)... it's honestly been pretty great to not be thinking about adjusting the shocks. The shocks are valved for my spring rates and corner weights, so likely I'd just make it worse anyway.

I've also idiot proofed my tire pressures, with the Michelin track connect setup... so all I really have to think about is camber (which I set via pyrometer).

It's relaxing

Last I read several years ago, you were using Ohlins dampers and Turner Motorsport Hybrid Street/Track Camber/Caster Plates.
I know you constantly re evaluate your set up and make improvements. What is your current set up?

I bet you run Michelin Pilot Sport 4S in the street?
Me: 245/40-19 and 275/35-19.

I like to see my tires reach 40PSI hot. My cold temp varies a lot depending on ambient temperature. I have an accurate after market real time temp and pressure senders and a digital monitor for my tires.
Is 40 PSI a good target?

My car would be an easy 300lbs more than yours. Cabrio plus no light weight components, plus heavy Brembos with floating rotors, plus me (Big Dave) at 240lbs.

Caster: Full Camber: -1.75 front -2.00 rear Toe: -0.18 Front -0.23 rear Ride height is max what my TC Klines will give me. My bumper cover clears most curbs and I-95 road debris now.

H&R Front rear anti sway bars. Turner adjustable front links.

How much $$$$$$ are these shocks going to bury my bank account?

[Cronenberged]

Last I read several years ago, you were using Ohlins dampers and Turner Motorsport Hybrid Street/Track Camber/Caster Plates.
I know you constantly re evaluate your set up and make improvements. What is your current set up?

I bet you run Michelin Pilot Sport 4S in the street?
Me: 245/40-19 and 275/35-19.

I like to see my tires reach 40PSI hot. My cold temp varies a lot depending on ambient temperature. I have an accurate after market real time temp and pressure senders and a digital monitor for my tires.
Is 40 PSI a good target?

My car would be an easy 300lbs more than yours. Cabrio plus no light weight components, plus heavy Brembos with floating rotors, plus me (Big Dave) at 240lbs.

Caster: Full Camber: -1.75 front -2.00 rear Toe: -0.18 Front -0.23 rear Ride height is max what my TC Klines will give me. My bumper cover clears most curbs and I-95 road debris now.

H&R Front rear anti sway bars. Turner adjustable front links.

How much $$$$$$ are these shocks going to bury my bank account?

I'll believe Obidian is running the H&R Street Performance coilover tuned by FCM. Thats the set up I'll be running and it's not the cheapest set up at around $5500. If you scroll up or back a few pages there is the optimal cheap set up that's around $1400.

[bigjae46]

I have TCK single adjustable front and rear. I am VERY disappointed. They dont stabilize the car well after 130MPH.

Great suspension should stabile our E46 M3 on rippled pavement even at 175mph. My custom Penske four way adjustable rear shock was MAGIC on my Honda Blackbird motorcycle at 180MPH. Unbelievable stability when high speed/low speed dampening was tuned properly. Once I tuned the shock, I never had to change it for any different type of pavement. Did perfect on the track AND the street!

I want that type ultra high speed stability and versatility for my M3!!!

The doubles are way better. The track car right now is on 400/700 springs. My weight distribution is different than most so optimal spring rates will be different. Never had a stability issue even before I put the aer on.

[Obioban]

Last I read several years ago, you were using Ohlins dampers and Turner Motorsport Hybrid Street/Track Camber/Caster Plates.
I know you constantly re evaluate your set up and make improvements. What is your current set up?

I bet you run Michelin Pilot Sport 4S in the street?
Me: 245/40-19 and 275/35-19.

I like to see my tires reach 40PSI hot. My cold temp varies a lot depending on ambient temperature. I have an accurate after market real time temp and pressure senders and a digital monitor for my tires.
Is 40 PSI a good target?

My car would be an easy 300lbs more than yours. Cabrio plus no light weight components, plus heavy Brembos with floating rotors, plus me (Big Dave) at 240lbs.

Caster: Full Camber: -1.75 front -2.00 rear Toe: -0.18 Front -0.23 rear Ride height is max what my TC Klines will give me. My bumper cover clears most curbs and I-95 road debris now.

H&R Front rear anti sway bars. Turner adjustable front links.

How much $$$$$$ are these shocks going to bury my bank account?

I used H&R coilovers as my base point. They're non adjustable shocks, with FCM prefers (for durability, and not screwing it up), ride height adjustable, and work with a variety of springs. My only complaint with using the H&Rs as a starting point is that they're pretty heavy (especially compared to the Ohlins I had before).

I am currently running GC street camber plates. I think the TMS hybrids are better camber plates, but they were back ordered for months when I was putting the FCM setup together, so it wasn't an option. I will switch back to them in the future.

I do run PS4Ss for my street tire, in 245/40-18 and 275/35-18. Sounds like your setup is one profile size too large, currently.

I don't really monitor tire temps/pressures on the street. I run 34psi cold, but my car is 10% lighter than stock. If my car was stock weight, I'd run 35-36psi on the street. On a vert, I'd probably run 36-37psi cold (on the M5 I run 38psi cold, and my M5 is ~vert weight). On track (not on PS4Ss), I start out at ~27psi cold, and adjust pressures after each session based on what the Michelin app tells me to do (I run Michelin tire temp/pressure sensors).

IIRC the H&R coilovers were ~$1500, and then I spent ~$5000 for the FCM services on the shocks. That said, I got every optional extra they offer, so you can get in a starter FCM setup for less (~$3000 was the starting point IIRC).

I run way less camber than most people, street and track, because my ride height is higher than most people-- so I have a way more functional camber curve.

[duracellttu]

The doubles are way better. The track car right now is on 400/700 springs. My weight distribution is different than most so optimal spring rates will be different. Never had a stability issue even before I put the aer on.

Can you let us know your corner weights as a reference?

[Cronenberged]

H&Rs are on sale rn for $1350

[bigjae46]

Can you let us know your corner weights as a reference?

With me - forget how much fuel. I think it was about 6 gal.


Just the car with 6 gal




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