Hi, I just picked up a sweet new to me 2002 M Roadster with the S54 engine. I am super excited since it was the car I wanted back in college but obviously could not afford. It was pretty sweet Red with S54 and 56k on the odomoter. It is only needing two major items from the PPI, convertible top and clutch, plus the Inspection II servicing and miscellaneous items like fixing the cruise control,new speakersm replacing the mirror, and belts, etc... and then finally performing a paint correction with a CQuartz. It will be a fun 2nd car after my GTI daily. I'll be doing a combination of diy and shop work. I have a few questions though as I intend to perform some mods for auto-crossing, canyon carving, and a couple of track days per year. Rear differential: I intend to upgrade the rear subframe, I have a friend with an off road racing team with 8 different welding devices, so I may upgrade the diff at the same time. I find the gearing on these way too long. Has anyone upgraded to the 3.73 or 3.46 gears? Do you like them? If so is there a differential you like? I have lift access so I can rebuild a clutchpack but prefer not to have to. I intend to keep the engine stock and it will never be boosted. Brakes: I was intending to go stainless steel lines, Hawk HPS pads and stock rotors, any recommendations? Suspension: How do people like to set these up? Stiffer in the front the rear, Does anyone have a handling tutorial for M Coupes and Roadsters?
. Welcome to the forums and congrats on the new ride. Hope you enjoy every moment in/at/around/under it. There are certainly others on these forums with more knowledge than I but, as to your final drive gearing there are a few basics to consider. If I'm remembering correctly, the gearbox in the E36 platform has a straight one-to-one 5th gear, hence the higher final drive ratio/s. Without an overdrive gear, the 3.73 would be very low gearing on the highway. Acceleration would indeed be stronger but, you would really be buzzing it at 70+ freeway speeds. The 3.46 would be a better compromise between performance and highway cruising. The OEM brake rotors are pretty good even if you track it a little. IMO braided stainless lines are a good/cheap investment. There are many good pads out there, Hawk being among them. We've been happy with Porterfield R4-S pads for dual duty. Be sure to upgrade to high temp brake fluid. Standard fluid can boil quickly on the track. We've been using GS610 for several years with very good track/street results. ATE still offers excellent high temp brake fluid too. You'll get dozens of suggestions on suspension. My only advice is don't over-spring it. There is such a thing as too stiff. Enjoy the ride! .
Welcome to the club & forums, congrats on the new ride & fulfilling a dream! Maybe someone else will have a comment on diff. gear ratios - I'd venture the stock gearing was tilted towards autobahn cruising. I have a Quaife diff. in my E30, which has worked fine for me, although obviously not dealing with the power levels of the S54. A downside, though it hasn't even remotely been an issue for me, quaife depends on both wheels being on the ground - if one wheel is in the air, it's no different than an open diff. I'd think that unless you were emulating drivers in the heyday of E30 DTM racing, most scenarios it's very unlikely to get a rear wheel off the ground. Clutch-pack diffs don't have that downside, so that might be a consideration. Stainless steel lines and racing brake fluid are good ideas - ATE Type 200 is popular (used to be ATE Super Blue, I could go on a rant about bureaucratic governmental idiocy, but will let it go at that), ATE has a dry boiling pt. of 536°, I use Motul RBF 600 (boiling pt. 594°), there are others with higher boiling points, although they're a good bit more expensive - I haven't used Hawk HPS, but I'd think they'd be fine for street and auto-x, I wouldn't be surprised if they're not the ideal track pad, but probably would be fine for starters (always take an extra set of pads to driver's school weekends as a backup). Stock rotors should be fine - if you hit the track and end up with warped rotors, the fix is improved brake cooling, &/or bigger (& pricier!) brakes. Getting air blowing directly into the brake rotor center and out the vanes is ideal and can accomplish a lot, but that can be a challenge/hassle to get ducting routed, and center-placed venting typically requires wheel bearing replacement - such cooling measures are probably overkill for maybe 1-2 track weekends a year. Although many like the cool look of cross-drilled rotors, there is more potential for cracking and failure with big chunks breaking off than stock rotors, meaning you end up off in the weeds or worse the instant the rotor fails and you hit the brakes - that alone is a strong argument in favor of stock rotors. When any type of rotor show signs of stress cracking, replacement is a good idea. From what I've heard, Z3 M coupes and roadsters can be twitchy as far as handling goes - high hp, very short wheelbase, and, if memory serves, a bit of a throwback rear suspension design - such a setup takes smoothness and proper driving technique/skills to manage the car. Tales of unexpected snap oversteer... so, as far as setting up the handling balance, some mild understeer might mean more predictability at the limit, especially for high-speed track events and everyday driving. BMW quite often biases it's vehicles towards understeer with narrower front tires and wider rears, I'm guessing yours is no different. The Z3 M is one model where I'd think in many scenarios it's probably better for handling stability/safety to keep the staggered setup for track and everyday driving. Auto-x, a bit of oversteer can help the car to rotate and get around the course quicker - some oversteer at lower auto-x speeds shouldn't be much of a problem as long as you're reasonably capable of dealing with it. I'd guess a very stiff suspension setup would exacerbate any negative handling tendencies. You might consider chatting to TC Kline and check their recommendations, or Turner Motorsport or Dinan.
Parts of the original post make me think that we've already made contact; perhaps you called me? If not, no worry, I just get a ton of calls, E-mails and PMs about the very things you're asking, specific to ///M Coupes & Rdstrs. (just just interrupted for the past fifty-five__55__minutes by someone going to look at a 98 ///M Rdstr in the morning...). I've had a 3.73:1 (40% lockup clutch-pack) differential fitted to my 2001 ///M Rdstr since February. February of 2002! Given the high RPM range of the S-54 engine, I do not find it buzzy at all, and it's a very popular ratio for this car. In fact, there have been many instances back when I was daily commuting in the car that I would launch myself down the freeway entrance ramp, merge with traffic and settle into a pace, only to realize several miles later that I had neglected to shift out of 4th gear and into 5th! Conversely, the exact same scenario in my 99 ///M Rdstr (then still with a stock 3.23:1 final drive ratio) that I would attempt to upshift, not realizing that I was already in 5th gear__I was looking to put it in an imaginary 6th gear, that the car didn't have. Such is the difference between the S-54 and the S-52 engine characteristics; the S-54 loves to rev, while the S-52 is left panting for more air! I am a big proponent for the TC Kline suspension packages. TC has worked up several options, and a seemingly infinite amount of tunability with his front/rear suspension packages. Their True Match coil/over setup is reasonably economical (I am in the middle of fitting a set to a 2001 Z3 3.0 Coupe, the rears are installed__along with an Ireland adjustable toe/camber kit__and the front will go on tomorrow). Anyway, the the Koni shocks can be supplied in single or double adjustable configuration; I typically recommend single for strictly/primarily street use, but if you have autocrossing, "canyon carving" and a track day or two planned, then the double adjustable (separate bump & rebound settings) may be more beneficial to you. Incidentally, TC has the shocks valved to his specifications, and both adjustments are external (versus the type of shock that has to be removed from the lower mount, bump-stop rubber pried out, compressed and... etc., etc., etc.). As for the springs, I find the 450 Lb/in front and 500 Lb/in rr best suited for me, and is a great street setup . Some people that track their cars opt to go for stiffer rear springs, and disconnect the rear swaybar altogether. That plays a little more into what MGarrison was saying. If we DID already talk, then you're aware of the trunkfloor/differential mount reinforcement that I offer__if not, contact me directly for full details. Congratulations on getting the car, I love mine (all of them)!
Well there you go. Someone with personal experience in the same car. Not a bad place to start. If your intended use for your S54 M is similar to his, you may have found the perfect set-up. Only you know. If your primary purpose is canyon carver and autocrosser with only some normal driving, Randy's platform would probably be excellent for you. Sounds like a Lot of fun to me. But, if you might be regularly spending hours on the highway, you might have other thoughts after a while. It sounds like you're pretty savvy, young and capable so you may well enjoy the heck out of the 3.73 gear. Only you will know. My initial comment about gearing was filtered by personal experience too. Muscle cars with 4.30s, 4.11s and 3.90s, Mazdas upped to 4.32 and 4.56, E30s with 4.10s and a Formula Continental running some ridiculous 5.xx for a short while. You get the idea. They were all Fun ... for their purpose ... or for a while. My toys for the last decade or two have all been double-duty daily drivers and I'm getting less tolerant of extremes in my cars (although my E30 is running an H&R Cup Kit). If you're young and have the resources, go for it. Have fun. It should be a great project and you're certainly starting with a fun platform. Let us know where this takes you. .
