Obioban's 2005 IR/IR Coupe

[bryce2113]

Good progress recently (later than I hoped, but... big undertakings this winter)...

Installed the final tube of the brake ducting, and confirm it fits without issue in all positions:

I'm curious to hear what made you move away from your custom 3D printed brake ducts. I used your design to print a pair over the winter. How do you like the Hard motorsport kit, specifically the slim low profile ducting component they now have?

[BMWahba]

Classics

That M5 is looking good! Polish up those tips

[Obioban]

Classics

[IamFODI]

I bought them from 3DM, and Ohlins reseller/rebuilder.
(833) 323-1117

^ Barry at 3DM is great! Close relationship with Öhlins USA, including a lot of testing work on BMWs for them.

[Obioban]

How did you get a set of Ohlin from perches with 65mm/2.5” ID? Getting away from 60mm would really open up spring options.

I bought them from 3DM, and Ohlins reseller/rebuilder.
(833) 323-1117

[duracellttu]

Ha... more involved question than you might think.

I found a line barely barrel springs that eibach makes, which they call their extreme travel line. That allowed me to use a shorter spring (6" IIRC) up front, while still having sufficient travel, which puts the perch above the tire at my desired ride height, allowing me to run bigger tires without compromising offsets (lets me run an ET35 front, which allows me to not have stupid camber to fit 285s). So, my front left is an eibach extreme travel 6" "barrel" spring. Eibach 0600.2530.0350.

Front left was tricky because the extreme travel line only comes in 50 lb increments.... but then I realized that GC sells and extreme travel spring (made by eibach, though they don't use that branding-- but visibly the same thing and I confirmed that they were with GC) in 6" 375 lb. Ground control GC150.64.66.


Both fronts are either 65mm or 2.5", I forget which (and am pretty sure most spring companies use the same thing here anyway. To fit that on the H&R shock body, I'm using Ohlins spring perches-- same thread pitch, so it's plug and play. Still using the H&R lock ring, because it's free.

Rear left is a TCK 700 lb beehive from my old TCK coilovers. TCK TKE 360 700 R.

Right rear is a GC linear 650 lb spring... I think 6"? With some of their cones on the top side, to protect the chassis from the spring.

Both rears are sitting on the H&R rear ride height adjusters, because they're really nice-- let you adjust the height without taking the spring out, or wheel off, which makes corner balancing way easier.

How did you get a set of Ohlin front perches with 65mm/2.5” ID? Getting away from 60mm would really open up spring options.

[Obioban]

Including the hybrid styles? I'm planning to replace the TC Kline plates currently on my car and NVH is a concern.

Great job and thanks for documenting all of this. I can appreciate the reasoning behind the choices you've made. Looking forward to more reviews of the suspension!

I had the hybrids before. They're closer to street than monoball in NHV. They're a nice product.

Mostly I don't think there's a ton of increased precision to be had from the monoballs/hybrids over street plates (as in, it's not hold chassis geometry like control arm monoballs) and they are a significant NHV contributor. So, the trade off didn't seem worth it to me.

... and the hybrid TMS camber plates have gotten crazy expensive, once you add the perches and shock adapters (and I sold my previous set with the Ohlins).

[Obioban]

Awesome to hear you finally got this installed!! What brand and size springs did you use F and R?

Ha... more involved question than you might think.

I found a line barely barrel springs that eibach makes, which they call their extreme travel line. That allowed me to use a shorter spring (6" IIRC) up front, while still having sufficient travel, which puts the perch above the tire at my desired ride height, allowing me to run bigger tires without compromising offsets (lets me run an ET35 front, which allows me to not have stupid camber to fit 285s). So, my front left is an eibach extreme travel 6" "barrel" spring. Eibach 0600.2530.0350.

Front left was tricky because the extreme travel line only comes in 50 lb increments.... but then I realized that GC sells and extreme travel spring (made by eibach, though they don't use that branding-- but visibly the same thing and I confirmed that they were with GC) in 6" 375 lb. Ground control GC150.64.66.


Both fronts are either 65mm or 2.5", I forget which (and am pretty sure most spring companies use the same thing here anyway. To fit that on the H&R shock body, I'm using Ohlins spring perches-- same thread pitch, so it's plug and play. Still using the H&R lock ring, because it's free.

Rear left is a TCK 700 lb beehive from my old TCK coilovers. TCK TKE 360 700 R.

Right rear is a GC linear 650 lb spring... I think 6"? With some of their cones on the top side, to protect the chassis from the spring.

Both rears are sitting on the H&R rear ride height adjusters, because they're really nice-- let you adjust the height without taking the spring out, or wheel off, which makes corner balancing way easier.

[K-Dawg]

The monoball camber plates are just too much NHV for the amount of precision they add, for me.

Including the hybrid styles? I'm planning to replace the TC Kline plates currently on my car and NVH is a concern.

Great job and thanks for documenting all of this. I can appreciate the reasoning behind the choices you've made. Looking forward to more reviews of the suspension!

[duracellttu]

Awesome to hear you finally got this installed!! What brand and size springs did you use F and R?

[Tbonem3]

Ya I'm concerned (I'm moving from poly tms street plates to vorshlag). Oh well

[Obioban]

Congrats on reaching this point. I'm surprised you're on poly bushed camber plates and rsms though.

The monoball camber plates are just too much NHV for the amount of precision they add, for me.

[Tbonem3]

Congrats on reaching this point. I'm surprised you're on poly bushed camber plates and rsms though.

[Obioban]

I did a bunch of mods over the winter. The most significant (for me, anyway) was the Fat Cats suspension.

Because of moving, it's been hard to make actual progress on getting the car 100% (was driving for a while with no sway bars connected, etc). But, as of last week I'm installed, bump/droop ratios optimized, corner balanced, aligned, corner balanced again, and preload dialed out. I've put ~100 (street only so far) miles on the car, and and comfortable giving very early impressions.

My complete setup is as follows:
Fat Cat Motorsports Stage 3 Coilovers (every option they offer)
Springs: 375 FL, 350 FR, 700 RL, 650 RR (equal frequencies left/right, 1.97hz front, 2.10hz rear, 75% front roll couple with sway in middle of adjustment range)
Ground control street camber plates
Ground control street RSMs
Ground control Front sway/bushings/brackets/end links
CSL Rear sway/bushings/brackets, with home made adjustable end link
Sealed monoball RTABs
TMS Sealed monoball FCABs
Bimmerworld sealed monoball rear adjustable camber arms
CSL Kingpins

I'm running at 60% bump, 40% droop up front, with a .5" rake (seem to be optimal for high speed oversteer/understeer), which puts me at ~14" front, 13.5" rear. In terms of alignment, I'm at -1.5 up front (this will be pyrometer based set more negative on track) and -2.0 rear (this will be left alone on track). I'm super psyched to have a setup that lets me run high enough to have a reasonable street camber, with the CSL kingpins-- should be a pretty killer camber curve and let me get away with meaningfully less static camber on track! Rear geometry should also be pretty good, with the CMP bushings raising the subframe and minimal drop. My geometry is also pretty rigidly held, as the only bushings in the entire setup are rear upper control arm inside bushing-- everything else is a sealed monoball (shock mounts and drivetrain mounts are still bushed/stock, so NHV is pretty minimal).

Onward to initial street impressions of the FCM setup:
The only word I can think of to describe the car is unflappable. Nothing seems to phase it. If you've ever driven a car with too much tire (the level of grip is more than the suspension can deal with), this feels like what the opposite would be. The closest analogy that fits is a stock FRS/BRZ/86, on the default prius tires-- only with PS4S levels of grip.

It is remarkably different than any setup I've driven before. And I've been all over the map-- Motons and JRZs on the e36 track car, TCKs and Ohlins on this car, Stock springs with Koni yellows on the M5, Dinan springs with Koni yellows on the M3 wagon. I can't say it definitively till I've been on track (after which I'll make a dedicated thread about the setup), but so far this setup feels faster and easier (to drive) than any of the above. Plus, I'm excited to have a setup that just valved for my specific corner weights and spring rates, so I don't have to mess with adjusting shock valving before/during/after track events. It's just correct for the car.

I'm pretty excited for this setup-- don't think I'll be changing again. I look forward to seeing what it's like on track!

[Obioban]

Street review of wavetrac: indistinguishable from stock.

No track time on it yet.