The W166 Mercedes-Benz ML & GL chassis existed as the key Sport-Utility offering for the Silver Arrow brand from 2012 through 2019. It entered production as the third iteration of the M-Class and ended production as the first GLE-Class following a mid-cycle rename and facelift in 2015. With the unique customization available during the ordering process, there were two suspension options presented, as well as a host of different braking packages. This guide will serve as everything you need to know about suspension and brakes on the Mercedes W166 M-Class and GLE-class.
Mercedes W166 ML/GLE Suspension Overview
The W166 chassis utilizes two different means of damping, but the geometry remains the same on both AIRMATIC and standard vehicles. All models use double-wishbone front suspension and multi-link rear suspension. On AIRMATIC-equipped vehicles, the front air spring is integrated into the damper (generally an Adaptive unit, as made evident by the second reservoir on the shock). In this configuration, each AIRMATIC strut assembly operates independently from wheel to wheel to maximize suspension comfort and stability. We still see a double-wishbone layout on standard-equipment vehicles, but the integrated AIRMATIC unit is replaced with a standard coil-on-shock assembly.
The double-wishbone layout in the front of the W166 means the presence of both an upper control arm and lower control arm; the damping assembly, be it the AIRMATIC strut or shock and spring, is nestled between these, passing through the upper control arm and top-mounting in the engine bay. The upper and lower control arms are connected via a large, elongated steering knuckle. The steering assembly uses a standard inner and outer tie rod.
Moving to the rear, there’s a similar variation. The multilink rear suspension accommodates either an air spring or standard coil spring, and the adjacently-mounted shock absorber will either be a standard shock absorber or a damping-adjustable unit for AIRMATIC. Architecture-wise, it’s the more common multi-link suspension. Mounted to the subframe is a lower control arm, which also acts as a perch for both spring types. The control arm and the vehicle are tied together via both a front and rear lateral arm to control forward and rearward movement, as well as a rear tie rod to hold things in place.
Mercedes W166 Suspension At A Glance
- Suspension available in passive coil spring format and adaptive AIRMATIC suspension; the latter was mandatory on some models/options packages, and was an option on most others.
- Double-wishbone front suspension and multilink rear across both standard and AIRMATIC-equipped vehicles; typically associated with performance-focused models, these attributes mean increased road-holding ability as well as increased comfort at cruising speed. “Active Damping System” available on AIRMATIC cars with associated options code, controls shock damping in tandem with air spring via drive mode selection.
- “Active Curve System” available on AIRMATIC vehicles, adjusts roll angle and suspension firmness with drive setting to improve comfort and cornering ability as well as vehicle stability at speed.
- Late GLE-Class vehicles with AIRMATIC may be optioned with Magic Body Control; cameras scan the road ahead and predict surface changes/undulation as a method of preparing the AIRMATIC suspension and damping settings ahead of sharp bumps/depressions to reduce cabin bound/rebound.
Mercedes W166 ML/GLE Suspension Packages/Models
When you’re looking at any specific ML or GL and trying to determine whether or not it has standard coil springs or AIRMATIC air suspension, it’d be easiest to look at options packages. Across both the M-Class and GLE-class vehicles sold during W166 production, there were more than a few option packages that made AIRMATIC suspension mandatory equipment. ML models optioned with the “Dynamic Handling Package” (which includes the Active Curve System package) received AIRMATIC by association; all GLE and ML models equipped with “Active Curve System” and “On and Off-Road Package” will also receive AIRMATIC by association. All AMG models produced in the W166 chassis code would receive AIRMATIC as standard equipment as well.
Designated by the option code “489,” we’ll mention how to decipher if your W166 chassis has AIRMATIC suspension below.
Does My Mercedes W166 Have AIRMATIC?
If you aren’t certain whether a W166 model has AIRMATIC equipped, it is fairly simple to figure out without crawling underneath.
VIN Decoder
By simply googling for a Mercedes-Benz VIN Decoder, you can easily type your VIN into a search bar that will tell you everything you need to know about what options and packages your vehicle was sold with (this isn’t inherent to the W166 chassis; you can do this with most common Mercedes chassis). If “Code 489” is present, this is an easy indicator that the vehicle is equipped with AIRMATIC suspension. As a bonus, these sites may also detail associated options packages and additional add-ons such as Dynamic Handling, On-and-Off-Road, or Active Curve.
Wheel Well Inspection
A fortunate aspect of the W166 is that, unlike its low-slung sedan counterparts, the chassis provides a substantial amount of ride height regardless of the suspension package ordered. As the front suspension will be the easiest to see given the double-wishbone geometry, the spring design can be easily examined by looking into the fender well between the tire and the fender. If a coil spring is visible, the vehicle has standard suspension; if the black fabric of an air spring is visible, the vehicle is AIRMATIC-equipped.
Interior Inspection
Another simple way is by inspecting the interior for ride mode selection. As the suspension is damping and firmness-adjustable, a ride selection knob will be present in the interior; standard AIRMATIC vehicles offer “Sport” and “Comfort” adjustments; on vehicles with the “On-and-Off-Road Package,” additional provisions will exist for rough-terrain adjustment. Of course, these adjustment options will not be present on a vehicle optioned without AIRMATIC as the right quality is not adjustable.
Mercedes W166 ML/GLE Suspension Problems
Front Lower Control Arms
The front lower control arms on the W166 contain three individual bushings, two of which are pressed into the lower arm and one of which mounts the rear of the control arm to the body. As these bushings are rubber, they will wear over time. Signs of a bad bushing will include clunking in the front suspension over bumps and may also include a wandering feeling in the front axle and steering. In the case of damage or severe corrosion to the lower control arm, the entire assembly can be replaced, but the easiest (and cheapest) course of action will generally be to remove the original bushings from the arm and press fit a new OE-quality bushing set (this would be the two forward bushings as well as replacing the rearward “lollipop”-style bushing assembly).
When a faulty bushing is suspected, the easiest course of action will generally be to get the car in the air and inspect the bushings for tears or signs of damage, as well as wiggle the wheel itself in an effort to replicate the noise. Given the size of the suspension components on a W166-chassis model, it would be wise also to use a large pry bar to assess bushing deflection under load while the vehicle is in the air.
Front Upper Control Arms
The front upper control arm can be tricky to diagnose for failure on the W166 chassis, as the symptoms of wear and failure will be largely the same between the lower and upper assembly. The upper control arm on this vehicle contains two press-fit bushings as well as a single ball joint, both of which will make a similar clunking noise over bumps and corners as the lower assembly. Again, the easiest way to identify signs of wear will be to get the car in the air and wiggle the wheel top-to-bottom, paying careful attention to where any rattling or clunking may be coming from. Inspect the ball joint for signs of damage or increased play, and give the bushings a bit of prying to try and identify if they have any excessive flex.
Steering Knuckle Ball Joint
The oversized steering knuckle of the W166 chassis connects both the upper and lower control arm and contains a ball joint of its own on its base; this ball joint accepts the nose of the lower control arm. While replacing the entire knuckle is arguably the simplest method of repair, it would be significantly more cost-effective to replace only the steering-knuckle ball-joint. This is most easily identified by a visual inspection of the ball joint following any rattling over undulations or during steering input. Visual damage to the ball joint, such as a torn boot or leaking grease, will indicate signs of impending failure. It’s also an excellent time to note the condition of the control arm where the upper and lower ball joints are received, as any pitting or wear on the control arm will indicate that a full control arm replacement is necessary in the near future. Metallic deterioration on the knuckle is NOT a regular issue, but crazier things have happened, so it doesn’t hurt to take 30 seconds to check that out.
CV Axle Failure
Many W166 owners have attested to noisy front CV axles relatively early in ownership. These are most easily identified via low-speed tight cornering in an empty parking lot or similar environment, paying careful attention to sounds of chattering, clunking, or clicking. Mercedes does offer inner and outer CV axle rebuild kits (front and rear) should an issue arise. Please note; AMG-tuned cars, as well as “Off-Road Package” models, use different axle boot and rebuild kits than their standard counterparts due to axles designed for higher-intensity operation.
Rear Lower Control Arm
The rear control arm design isn’t all that different from the design up front, with the exception of some general hallmarks that are somewhat adjacent to the standard Mercedes multilink rear.
Just like the steering knuckle at the front of the vehicle, the W166 uses an integrated (but replaceable) ball joint in the lower portion of the rear knuckle (this is where the lower control arm mounts to the hub). The lower control arm itself, generally two separate pieces for Mercedes’ typical multilink, is one large cast piece for the W166 and includes two rubber bushings (two inward, which mount to the subframe, and one further outward, where the rear shock absorber connects).
From here, though, the designs diverge. Rather than an upper control arm, the rear spindles have three distinct mounting points that keep the wheel affixed to the vehicle; a long “lateral arm” or a rear tie rod located towards the rear bumper in relation to the hub (more on that in a moment), a “camber arm” which bolts directly to the top of the spindle, and a forward tension strut that secures toward vehicle-front of the spindle. The spring, regardless of whether it’s an AIRMATIC spring or a traditional coil spring, will sandwich between the lower control arm and the chassis of the vehicle.
Front & Rear Lateral Arm, Rear Tie Rod
Although each of these parts serves a different purpose in the rear geometry of the W166, the parts are relatively similar in nature; each of these integral pieces relies on two bushings, one of which is fixed to the wheel carrier and the other of which affixes to the chassis of the vehicle. Multilink suspension can be particularly irritating to deal with, as the increased quantity of rubber bushings can make tracking down a rattle or clunk an involved process. Diagnosis will again be an exercise in visual inspections as well as an effort to recreate the ailment by shaking the wheel with the vehicle in the air. If the noise can be replicated, aim to isolate exactly where the noise is coming from.
AIRMATIC Air Strut/Spring Assembly
AIRMATIC failures are an inherent byproduct of opting for the more premium of the two suspension options, and they can be pricey depending on the severity of the issue. While the majority of issues faced by owners will generally be air strut or air spring-related, it is not uncommon for money to be wasted in these areas while chasing an issue only to find the wrong equipment has been remedied due to something like a bad compressor or a simple leaky airline.
AIRMATIC suspension utilizes a network of hoses and a compressor to provide adequate lift and inflation to the bladder inside of the air spring, providing comfort and compliance via millisecond-based adjustments of firmness at each corner. Each corner of the vehicle provides the potential for an AIRMATIC issue when the system is neglected or treated improperly; bending an air supply hose during spring replacement or a failing compressor can result in improper suspension behavior.
AIRMATIC issues should be addressed carefully and with certainty to avoid spending more than needed to remedy the problem at hand. For more information on AIRMATIC suspension and what to look out for, the parts that comprise the AIRMATIC assembly, and recommended maintenance intervals, you can consult our Ultimate Guide to Mercedes AIRMATIC by resident Mercedes expert Kyle Bascombe.
Standard Shock/Spring Assembly
The shocks and springs of non-AIRMATIC vehicles may be a good deal simpler (and cheaper) to repair, but knowing when to replace shocks and springs can also be tricky. Many early W166 owners reported hearing a popping or a clicking noise over bumps, but only from one corner of the vehicle; upon assessing the usual culprits of bushings, CV axles, and ball joints, the consensus was generally that everything was in order. Only when these individuals replaced their strut assemblies did they find that the issue went away, the extra chatter being a result of a faulty shock from the factory.
Generally, a strut failure on a W166 vehicle will be a lot easier to identify. Visual inspection for a failed strut should include examining the damper for any signs of leakage, grime buildup, and corrosion. If audible squeaking or groaning can be heard during compression, this can also serve as an indication that the shock absorber is on the way out.
Moving to the coil springs, replacement is generally warranted in the instance of corrosion or wear being visible; generally, it is good practice to replace the coil spring with the replacement of the shock absorber. Should a coil spring fail, there are a few key indicators that can indicate a problem to the driver. In early and less severe cases, a metallic rattling may be heard over bumps, a result of disconnected coils bumping into each other or of the spring itself shifting in the seat, given the new room provided by missing coils. In severe cases, the vehicle may sit visibly lower across an axle or even just one corner as the springs shed coils and gradually reduce ride height. Both a spring and shock failure can greatly affect handling characteristics, road-holding abilities, and vehicle capability and should be addressed immediately.
Hydraulic Sway Bar
AIRMATIC models equipped with active dampers and more advanced handling packages (such as ACTIVE CURVE system or Dynamic Handling) utilize a hydraulic front sway bar in an effort to increase comfort, variability, and versatility. These sway bars are able to decouple for off-road driving, manipulate themselves for increased road handling, and also can decouple themselves at highway speeds to increase cruising comfort.
With the increased versatility of this unit comes the added risk of failure. The unit uses a hydraulic rotary actuator nestled in the middle of the sway bar, which is able to adjust the rigidity as well as the coupling between both wheels. The system is hydraulic yet operates in tandem with the air compression provided by the AIRMATIC system; a hydraulic reservoir exists on the passenger side of the engine bay. While leaks from the plumbing between this reservoir and the sway bar itself are rarely reported as of now, the reservoir’s cap did receive a recall in 2018 for a new unit with a bolstered membrane. Some early models that have not had this new cap installed may be prone to leaking from the vent holes of the cap, a small issue with expensive implications should the hydraulic system run dry and burn out the rotary actuator. If there is a presence of leaking hydraulic fluid in the engine bay, if the fluid level reads low or if the fluid appears foamy (a result of air mixing with the fluid due to a low fluid level), the cap likely warrants immediate attention.
Mercedes W166 ML/GLE Suspension Upgrades
Suspension upgrades for the W166 are relatively few and far between but can most easily be split again by AIRMATIC and non-AIRMATIC options
Standard Suspension
General standard suspension upgrades for the W166 will generally be an upgraded shock and spring. Trusted suspension companies such as Eibach and Bilstein should be able to provide the ride height decrease and handling upgrades that most W166 owners may seek.
For those willing to be a bit more adventurous, newer companies also seem to have some W166 performance options listed; Silvers lists a set of single-piece coilovers for the M-Class and GLE-Class.
Strut spacers can also be found for a ride height boost, although extra research must be done to ensure that the company supplying the parts is reputable and trustworthy; as a non-OEM piece connecting the top of the strut to the body, the failure of this part while driving can be incredibly dangerous.
Off-roaders will find that most 4MATIC-equipped W166 vehicles are reasonably capable in stock trim, but may fail to find performance upgrades on the aftermarket. Upsized wheels and tires will generally be the extent of modifications to these vehicles, with the crown for off-road driving being held by the W166 models equipped with the Code 430 package.
AIRMATIC Suspension
AIRMATIC is Mercedes’ highest-tier suspension offering, and as such, this suspension package can be tricky to expand upon. AIRMATIC provides a ton of versatility out of the box, and vehicles optioned with “Active Damping” shock absorbers will likely portray the best the vehicle has to offer. However, that doesn’t mean W166 owners must leave their cars stock. A few options do exist for W166 AIRMATIC owners looking for a sportier appearance.
“Lowering Links” are produced by a few companies (the linked company being UK-based), providing extended height sensor links that effectively trick the vehicle into running AIRMATIC on a lower ride height setting than it normally would by making the sensor believe the vehicle is riding higher than it is. We can’t speak on the effects that this kit may have on the AIRMATIC assembly long-term, but this is likely the cheapest approach to lowering the vehicle.
“Lowering Modules” achieve the same goal via software rather than hardware. This equipment usually plugs into the vehicle anywhere from the OBDII port to splicing into the AIRMATIC control module and is available from any plethora of manufacturers; the software effectively expands the range of functionality for the factory air shocks and air springs, offering the decreased ride height that many seem for a sporty appearance. While many companies may manufacture these kits, the most trustworthy will generally be from recognized manufacturers such as H&R.
In some cases, namely in secondhand purchases, AIRMATIC owners may wish to delete their factory suspension entirely in favor of a cheaper shock-and-spring design. These kits are available all over the internet from a host of companies looking to cash in on stressed AIRMATIC owners, so sufficient research must be done prior to making a purchase. Frequently, AIRMATIC owners will pick an easy and inexpensive option and put them in the car only to learn that a fault code is triggered and is near-impossible to clear. Going with a trusted supplier that offers a coding defeat is always the best course of action for factory-esque function, even if it costs a few hundred extra per corner to go with a trusted AIRMATIC-delete brand such as Arnott (who does not have a kit for the W166 chassis yet), the new suspension will likely last a long time and should still allow the vehicle to function as designed.
In regards to the off-road community, AIRMATIC vehicles provide a bit more utility out of the box. Standard AIRMATIC vehicles have a bit of additional ride height to offer, and the continuously-variable suspension geometry will often provide the axle movement one might find favorable on a jagged or rugged trail. For the ultimate in performance, though, prospective buyers should seek to find a W166 with the factory-optional “On-and-Off-Road” Code 430 package. These vehicles get a two-speed transfer case, additional drive modes and data displays, increased ride height and differential variability versus standard W166 AIRMATIC vehicles, and metal skid plates down the length of the vehicle. These parts, supplied by Mercedes themselves as a factory option, will likely be the best available to make the W166 into a capable trail vehicle; unfortunately, retrofitting them secondhand is relatively impossible, save for the extra undercarriage cladding.
Mercedes W166 ML/GLE Brake Specifications/Overview
Front Discs
The W166-chassis is available with several different engine options, and as such, the level of artillery to get the hefty SUV stopped can vary greatly. While the caliper options on the W166 chassis are relatively easy to grasp, buying the correct brake discs can be a challenge.
The W166’s standard front axle equipment is a 330mm x 32mm blank-face, vented disc. It’s equipped on all base-optioned vehicles, ranging from the ML350 to GLE300d to GLE400. As an asterisk to this rule-of-thumb, the 2012 (first-year) ML550 received specific drilled front and rear discs as standard.
Available for almost any W166 model was the P31 “Sport Package,” and one of its several changes over the standard equipment was larger front brakes. The exact size is determined by the engine; M276 V6 models received vented and cross-drilled 350mm x 32mm rotors, while V8 models received a similar set at 375mm. The package is available across a range of models in the W166 lineup and can be found on anything from the ML250 BlueTEC to the GLE350 to the GLE550e; however, you should know that post-GLE facelift P31 models use a different size front brake pad from P31-equipped M-Classes.
AMG-tinkered models such as the GLE43 AMG and GLE450 AMG and vehicles equipped with code U29 “Performance Braking” package use an even larger cross-drilled and vented rotor, sizing in at 375mm x 36mm. The U29 package is relatively rare, but consulting both a VIN decoder and the part number present on the removed set of discs should adequately indicate whether or not the discs are these upsized models versus the P31 package for non-AMG examples.
The most performance-oriented models, such as the ML63, GLE63, and GLE63S, as well as the late U29-optioned GLE400 and GLE450, have a massive 390mm x 36mm vented-and-drilled front disc. It can also be found on non-AMG biturbo M276 vehicles that are equipped with the M016 “Performance Enhanced Engine” package. It serves as the highest tier of front axle stopping power on the W166 chassis.
Rear Discs
Moving to the rear of the vehicle, we see a similar diversity in rotor size and type. At the bottom-rung comes what would be considered standard equipment, a 325mm x 14mm solid and blank-face disc. Anything from an ML350, to ML250, to GLE350 or GLE300d, to basically anything between may run these discs While their skinny and small dimensions might not add the sporting appearance that W166 owners may seek, they’re significantly cheaper to replace than alternative vented or drilled rear rotors.
Moving up the ladder to P31 sport-equipped W166 vehicles, the 330mm x 22mm vented and blank rear disc is the next largest offering. With a larger diameter and added cooling capacity, this braking package does an excellent job of toeing the line between utility and performance; added size and cooling help promote strong braking characteristics, while the moderately-sized no-frills disc saves a bit of money over a sporty cross-drilled or slotted design. Cross-drilled options can be an effective cosmetic-enhancing performance modification for those looking for an easy bolt-on upgrade.
Moving up to a 345mm x 26mm vented and cross-drilled rotor, we have the rear-axle braking artillery for the ML63, GLE43, and M016-equipped GLE450 and GLE400 models. These units will also fit the same models equipped with the U29 “Performance Braking” code.
Front Calipers
As mentioned above, the W166’s front caliper equipment has three tiers. The majority of W166 vehicles, namely those with a base-level braking package, will sport a dual-piston sliding-type caliper that is unpainted and unbranded. These calipers will generally be more than sufficient for day-to-day driving but are rather unimpressive cosmetically.
Moving up to Sport-equipped non-AMG vehicles, we still see a sliding dual-piston caliper. This unit, manufactured by ATE and sporting some Mercedes-Benz badging, is a bit more premium in appearance.
At the top of the range, we have a caliper bespoke to AMG models of the W166 family. A fixed-piston monoblock design for increased performance via equal distribution, the AMG models receive a six-piston single-piece Brembo-manufactured front caliper, both painted and proudly wearing the “AMG” moniker for cosmetics. A 2016 GLE63 will reportedly stop from 70 mph in 166 feet; for reference, a tiny mid-2000s W203-chassis C32 AMG does the same test in 174 feet.
Rear Calipers
The rear caliper on the W166 chassis is a bit more straightforward. A single-piston, TRW-manufactured sliding caliper is used across the range, with the most-premium option sporting paint and appropriate badging for the AMG models. The parking brake for these models is electronic and is affixed to the side of the caliper; when replacing pads, be certain that this parking brake is off. The piston may eject itself otherwise.
Mercedes W166 ML/GLE Brakes At a Glance
- Sliding caliper design used across most standard-option vehicles both front and rear; two-piston in front, single-piston TRW-manufactured rear.
- P31 Sport Package vehicles/U29 Performance Braking M-Class vehicles receive twin-piston sliding painted/finished front calipers via ATE; same rear TRW single-piston sliding caliper.
- AMG models receive six-piston, painted Brembo front calipers; rear sliding single-piston (painted)
- Several different-sized front and rear discs vary from model to model and across trim levels; careful attention necessary to purchase the correct set
- OEM-plus upgrades are relatively easy
Mercedes W166 ML/GLE Brake Repair/Service
Very little is different than on your standard car when it comes to servicing or repairing the W166 front or rear braking system. The sliding caliper that will be present on the vast majority of W166 models, both front and rear, is a tried-and-proven design, both effectively providing stopping power and remaining relatively cost-effective from a manufacturing and maintenance perspective. Wear items on (and surrounding) the sliding caliper consist of:
- The pads and the disc itself.
- The brake wear sensor (integrated into the brake pad set).
- Caliper sliding pins.
- Associated fluid and hoses.
A single pad sensor exists for the W166 chassis, which mounts to the front caliper. This sensor nestles into the pad when new, and as it wears over time, the sensor will eventually make contact with the disc and trigger a low-pad warning. That does not mean immediate replacement is mandatory; the warning indicates that the pads need servicing as soon as possible but have enough mileage left to get where you need to go.
The brake fluid for the W166 chassis is rated at MB 331.0 DOT 4 Plus, and the braking system only takes a couple of liters to fill. Mercedes cites that as a result of the more advanced DOT 4 Plus fluid, the fluid should be flushed from the vehicle every 20,000 miles to ensure a healthy lifespan for the entire assembly. Again, this interval can be extended slightly but may result in premature wear of the braking assembly over time (and may reduce braking performance as the fluid becomes contaminated).
A brake fluid flush can be done manually but is handled easiest via a pressure bleeder, especially without anyone to help out. With the replacement of pads and rotors, be sure to inspect the plumbing of the brake hoses for any signs of leakage or cracking; failure of these hoses can be spontaneous if not caught ahead of time and can be very dangerous. Inspecting the mounting hardware for the caliper is also pertinent, as heavy corrosion can result in an eventual failure or (at minimum) added difficulty in a future replacement. Inspecting brake pad wear can also be lucrative; with uneven wear between the inner and outer pad on a sliding caliper design, one can infer that a brake caliper is not functioning as intended.
Moving to the monoblock design on the 6-piston AMG trims, we actually see a decrease in servicing difficulty. The monoblock design, a commonly-used blueprint for motorsport, promotes easy pad swaps via a drop-in design. Pad swaps on these models take only minutes simply by punching out the pins, removing the clips, and pulling out the old pads to swap in the new set. When servicing the discs with the pads, service is still relatively straightforward; the caliper is unbolted from the mounting bracket and is moved out of the way to allow for the removal and replacement of the old disc.
Replacement intervals and items to be concerned about remain the same for the AMG monoblock calipers. Wear sensors, hoses, pads, discs, and fluid should all be serviced to ensure the longevity of the expensive six-piston front unit as well as the simple sliding rear unit. Replacing everything together is pricey but leaves you without any questions regarding the safety and health of your braking system.
Mercedes W166 ML/GLE Brake Upgrades
The world of W166 braking upgrades is a tricky one. For the vast majority, upgrades will be limited cosmetic enhancements or light performance increases; few are likely plotting a hot-lap session, even in their GLE63S.
Discs
As hinted earlier, there’s a lot of variation across the W166 range, from blank to drilled to upsized and downsized. Most commonly, questions regarding disc modifications on the W166 surround the concept of getting cross-drilled discs on both the front and rear of the vehicle.
On vehicles with cross-drilled fronts from the factory but blank discs in the rear, upgrading the rear discs to an aftermarket or OE-replacement drilled model is generally the easiest solution; manufacturers such as Zimmerman make a high-quality drilled replacement for blank rears to add a bit more cooling as well as a symmetrical appearance to the front axle.
Note that while caliper models may seem similar from base to sport package models, rotors cannot necessarily be swapped freely; differing diameters between discs available with each package will require a different size pad as well as the appropriate-sized caliper to hold the pad.
Calipers
Caliper upgrades across the W166 chassis are relatively few and far between, largely a result of the similarity between caliper models below the AMG level. Owners looking for a cosmetic change on base-level calipers would best spend their money by painting their calipers (or having them painted professionally) or otherwise cosmetically modifying them. Aftermarket solutions do exist from companies such as Ceika or Brembo, but these will come at a hefty premium for what many would consider to be a cosmetic upgrade, given the installation of race-grade equipment on an SUV. Familiarity with the variances between front spindles is generally the best way to verify if upmarket calipers will fit a lower-package vehicle.
Pads
Uprated brake pads are the simplest and best course of action when it comes to vehicles not destined to see a race track. A brake pad can be selected entirely surrounding the needs of the vehicle and the owner; a low-dust pad to keep nice wheels clean, a long-lifespan pad for commuters doing a lot of driving, or even a high-bite and heat-resistant pad for those who are driving their W166 a bit harder than most. FCP Euro offers a pretty good spread for P31 Sport vehicles, ranging from low-dust options for daily driving like ATE, TRW, Akebono, or Textar, to more performance-targeted pad models like the Ferodo DS2500. AMG models see some additional performance-focused pad options as a result of their sport-focused caliper design, ranging from more Ferodo equipment to EBC pads to Hawk Performance gear.
Hardware
If you can track them down, stainless steel braided brake lines from a reputable manufacturer can be an excellent hardware upgrade. The reinforced line provides additional pedal feel for any vehicle using hydraulic braking, as well as increased heat resistance, added weather resistance, and less risk of swelling over time. Relatively inexpensive and simple to install, stainless lines will increase performance as well as longevity over crack-prone rubber hoses.
Mercedes W166 ML/GLE Brake Torque Specs
- Mercedes W166 Front Caliper Bracket Bolts - 85Nm or 63 lb-ft, plus 45°
- Mercedes W166 Front Caliper Guide Pins - 55Nm or 40 lb-ft
- Mercedes W166 Rear Caliper Bracket Bolts - 55Nm or 40 lb-ft
- Mercedes W166 Front Caliper Guide Pins - Tight!
