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      03-30-2019, 06:07 AM   #3
PeterY
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Drives: Graphite E92 335i N54 6MT
Join Date: Jan 2012
Location: Melbourne, Australia

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2007 BMW 335i  [0.00]
Post E9x ///M3 steering rack retrofit

I installed an E9X Servotronic M3 steering rack on my car, it's by far one of my favourite mods to date! Highly recommended in my opinion! The M3 steering rack has a quicker ratio of 1:12.5 vs the standard non-M steering rack which has a ratio of 1:16.

Part numbers:
1- M3 steering rack - 32102283632
2- M3 billet steering shaft (optional) - 32302283432
3- M3 tie-rods (optional) - 32102283461 (left), 32102283462 (right)

*try to get a complete rack with tie-rods, steering shaft and everything in one package. Itíll work our way cheaper. The seller I got mine off included the steering shaft and tie-rods free of charge.

The M3 rack is wayyyy faster, and makes the steering feel so responsive. The M3 steering rack is Servotronic, i.e. it has variable assistance, at low speeds it gets lighter, and at high speeds it becomes heavier. To achieve this function, it has a solenoid valve on it, and the valve is controlled by the JBBF module, I haven't wired the solenoid valve to the JBBF module yet (on the M3, the Servotronic steering weight is controlled by the MSS60 DME, lucky there's an alternative way to control it on non-M cars, on the 1M and other N54 vehicles the JBBF can control the steering assistance).

To achieve a heavy steering, it closes the valve, which restricts the flow of the pressurised hydraulic fluid coming from power steering pump, and for light steering, the solenoid valve is fully opened. At its lightest setting, the steering is significantly lighter than the stock 335i steering weight, and itís heaviest, itís also significantly heavier than the stock 335i steering.

Overall the steering feel has been majorily improved. No wonder all the media reviews keep describing the E92 M3 to have that magical steering feel that no other car has got haha

Currently it's running at the heaviest possible setting, it's a fair bit heavier than the standard 335i steering, I hated it initially, but now I got used to it, and I absolutely love the meaty steering feel. Not sure if I'll ever get around to wiring it tbh, we'll see. I might do it on a quiet Saturday afternoon, and code the JBBF module to have a custom assistance curve, i.e. specify how heavy I want the steering to feel at different speeds (can be done through JBBF NETTODAT hex file coding ).





I faced an issue with installing the M3 rack, the M3 tie rods are too long, which means that even when they're fully winded in, I had significant amount of toe-out. When I swapped to the original 335i tie-rods, I was uncomfortable with how short they are, to achieve my desired alignment (zero toe), the inner and outer tie-rods were only screwed by a couple of threads, which wasn't safe in my opinion.





The solution was to cut off 2-3mm off the M3 inner tie-rods, and screw them all the way inside the outer tie-rods, that way the arm is very strong with plenty of thread contact in-between the two pieces, and I can achieve my desired alignment.





The issue originally rose because the E9X M3 received different knuckles to non-M cars, and the tie-rod attachment point sits further out than on the M3 than on non-M cars, hence why the M3 has longer inner tie-rods to make up for the distance.



The M3 rack also comes with a nice billet piece steering shaft, this is a solid piece, unlike the standard non-M E9x which is a hollow tube. This was done so that the steering shaft could clear the header of the S65B40 V80 motor. After initially looking at it, it seemed that it could help with fitting bigger outlets on RHD cars, but if you take a close look, the U-joint section is actually more bulky on the M3 steering shaft. So I'd say it won't help much for that purpose. The steering shaft swap is optional, it doesn't have to be swapped with the M3 rack (you can grind off a small plastic tab, and re-use the standard steering shaft). I still fitted it either way, it's a nice looking piece of metal, and it's significantly stronger than the stock piece, it also has a beefier universal joint on it.







Just for reference, here are the steering rack ratios of some other performance cars on the market:

You'll notice that the E9X M3 has by far the quickest steering rack out of any modern production sports car!

E9x M3 and E82 1M: 12.5:1 (they use the same rack)

Non-M E9x 3er: 16:1
Non-M E8x 1er: 16:1
E46 M3: 15.4:1
E46 M3 ZCP/CSL: 14.5:1
E46 330ci ZHP: 13.7:1
E86 Z4M Coupe: 12.8:1 (the closest to the E9x M3)
F82 M4: 15:1
F87 M2: 15:1
F10 M5: 16:1
W204 C63 AMG: 13.6:1
W205 C63 AMG: 14.1:1
B6 and B7 RS4: 13.1:1
B6 and B7 S4: 14.5:1
EVO X MR: 13:1
VA (4th gen) WRX STI: 13:1

It's interesting that the newer ///M cars have much slower steering ratios than old school cars, this could potentially be due to the electric motor used in the Electric Power Steering system not being strong enough to turn the wheels. The quicker the steering ratio, the more energy is needed to turn the steering wheel (a simple gearing leverage situation). An alternative thought, it could be due to efficiency reasons, putting a very quick steering ratio and a strong electric motor behind to turn the wheels might ruin the benefits of changing over to EPS. EPS found its way into modern cars to save energy (fuel) and lower emissions.... etc. So the engineers might have been forced to slow down the steering rack ratio to find a good balance between efficiency and functionality.
__________________
Sparkling Metallic Graphite 335i Coupe 6MT (Build Thread) | MHD Custom Tune | Wagner EVO2 FMIC | ÷hlins R&T coilovers with 8/14 Swift springs | Dinan Camber Plates | Rear HardRace fully ball-jointed toe arms, upper camber arms and guide rods | Front M3 control arms with Monoballs ball-joints | M3 Steering rack with servotronic retrofit | E93 M3 Front & Rear Sway Bars | Nolathane rear subframe bushings | HEL Performance SS braided brake lines | 19" BMW 437M wheels | BMW P steering wheel | CIC+Combox retrofit

Last edited by PeterY; 05-17-2020 at 07:49 AM..
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