2003 Infiniti M45 Suspension Guide – Part 3 Air Suspensions

In part one of our suspension guide we covered the cheapest way to lower your 03 M45, springs. Springs are great and will take out some of that nasty wheel gap but you are stuck at whatever height the spring was made for and none of the one for the m45 seem to get the drop just right.

So in part two we showed you another more adjustable option in coilovers. Coilovers eliminate the need to settle for one set height. With a wrench, jack, jack stands and say 30 minutes you can change your ride height as often as you like. Coilovers also offer you the ability to fine tune your suspension via dampening. The drawback is that 30 minutes it takes to change the ride height, not very handy if you come up on a speedbump or steep incline.

Enter Air Suspensions.

Today’s modern air suspensions should not be confused with the hydraulic setups you see on lowriders. A hydro setup is basically a piston that is welded in place of your shock/spring setup. It can rapidly raise and lower the car, even make it bounce. While this achieves the same effect as an air suspension, easily adjustable ride height, it has many drawbacks.

The main problem for me with hydraulic setups is the ride is HORRIBLE. Since the piston that replaced the shock/spring setup is always rigid and has no give it would be the same as just welding in a metal bar for your suspension. It provides no give, absorbs no impact resulting in the harshest possible ride.

The second issue I have with Hydros is the hydraulic fluid itself. If you have a leak or any problems it is a damn mess. Lastly the pumps and batteries to have a good system are pretty large and take up most of even a good sized trunk.

Now on to what a modern air suspension is. The modern air ride systems like the Air Runner setup that is going in Project VIP are comprised of an adjustable strut with an “air bag” in the place of the spring, hence the name “bagged” for cars with air suspensions.

This bag can be inflated or deflated by the push of a button and allows to to raise or lower the car at ease. This is the same setup that Lexus and Mercedes use in cars like the Mercedes Benz CL63 AMG.

The pressurized bag reacts just like a spring allowing slight give and when paired with a set of adjustable dampers like the KYB in the Air Runners you get a track worthy push button adjustable suspension.

The system is pretty simple overall. You have the bagged struts that replace the factory setup. These are hooked up via air lines, fittings and valves that run to an air storage tank. The tank is hooked to a small compressor that fills the tank as needed. When you want to adjust the suspension you hit a switch which either tells the system to add or remove air from the bag.

The illustration below from Air Runner shows it pretty clearly.

Gallery: Courtesy of Air Runner

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Option 1: Air Runner Bolt in Suspension for 2003 Infiniti M45

Since this is the setup going into Project VIP I figured I would start with it. The Air Runner is a Japanese company that has a US division, making getting this kit much easier than some of the other JDM options. The kit is basically a bolt in setup. The fronts you just swap out your factory units for the Air Runner’s and the rear only requires you to weld in a supplied mounting plate for the bag. The rears are different since the shock and spring are separate not a single unit. Check back for a full article on the install later this month.

Air Runner for 2003 Infiniti M45 Specifications:

2 Front Sleeved 4-Dial Struts
2 Rear Bellowed 4-Dial Bag
1 Tank (Standard or Pancake)
1 Heavy Duty Compressor
1 Mounting Plate
1 Pressure Switch
MSRP: $4,293

Air Runner Suspension on 2003 M45 in Highest Position:

Air Runner Suspension on 2003 M45 in Lowest Position:

For more info or to Order Air Runner for your car visit www.airrunnersystems.com.

Option 2: Universal Air for 2003 Infiniti M45

While not officially listed as an application on their website it has been documented that with some modifications this kit can be fitted to an 2003 Infiniti M45. This is a “bag over” setup. This means that in the front your have to replace your spring with the bag and retain your existing strut. You don’t get and entire new unit like you do with the Air Runner.

This helps keep the cost of the system down but makes installation a bit more tricky. These can also be used in conjunction with coilovers making them even more adjustable. That however drives the cost up significantly. There is a member on Vipstylecars.com that did a UAS with JIC coilovers setup. It required a lot of modification and fab work. This does not seem for the faint of heart. Check his build thread for the details.

UAS System for 2003 Infiniti M45 Specifications:

2 VIAIR 480C, 200 PSI, 100% DUTY CYCLE
1 200 PSI PRESSURE SWITCH
1 SWITCH BOX (Hand Held 9 Switch)
8 “Blow Proof” 1/2″ AIR SOLENOID VALVE
2 UNIVERSAL AIR SUSPENSION AERO SPORT 9″
2 UNIVERSAL AIR SUSPENSION AIR HOUSE 8″
1 D.O.T. APPROVED FITTING & HOSES FOR F.B.S.S
1 CHROME ALUMINUM AIR TANK
1 SET OF BOLT-ON BRACKET KIT
1 HEAVY DUTY SOLENOID
1 BOLT PACK
MSRP: $2300

UAS installed on 2003 Infinit M45: Courtesy Mark Yuen Team Emotion

For more info or to Order UAS for your car visit www.universalairsuspension.com.

These are the main two documented “systems” that I have seen used in a 03 M45. You could always try and piece a set together from parts but looking at the amount of work that went into the JIC/UAS setup I don’t know if its worth it. When you take the cost of the UAS ($2300) and add in a set of Coilovers ($2000 for anything JDM) your are at the price of the Air Runners for which the install is infinitely easier.

Other non documented on US M45 possibilities:

Aimgain: MSRP 808,500 Yen or $8,900 US