Dobinsons Internal Monotube Shocks (IMS) + Upper Control Arms (UCAs): The Perfect Setup For A Serious Weekend Warrior?
The Dobinsons IMS kit is a solid mid-level suspension offering for our 5th Gen 4Runners. They have been a staple in off-roading in Australia since 1953 and are quickly gaining popularity in the US. They are also made in Australia just like their main competition is.. the all-mighty ARB.
They’ve made a name for producing well-built, durable suspension components at a reasonable price point. This holds true with their internal monotube shock (IMS) kit that we’ll be reviewing today!
I consider this kit to be a step-up from entry-level suspensions such as:
- Bilstein 5100s
- Dobinsons Twin Tube Shocks
- Eibach Entry-Level Kits
The IMS suspension sits between those kits and pricier high-end options like:
- Dobinsons 3-Way MRR
- Fox DSC
- King Shocks
Before installing the IMS kit, I ran the Dobinsons twin-tube shocks for around 20,000 miles. I will provide a comparison between these two offerings as well.
Dobinsons offers a number of different lift options, with everything from 0-3″ of lift. They also offer options for extended travel front & rear travel, adjustable trailing arms, and panhard bar. Their rear coil springs also come in stock weight ratings all the way up to 1000 lbs constant load. Whatever your desired lift height or weight carrying needs, Dobinsons has you covered!
Dobinsons components are tested in some of the harshest environments in the world, and they claim virtually zero shock fade with their IMS components.
Find it Online:
- Full IMS Kit Non-KDSS (KDSS kit also available): Check Price
- Dobinsons UCA: Check Price
- Dobinsons twin-tube shocks: Check Price
Twin-Tube vs Monotube Basics
There are a number of benefits of a monotube set up over twin tubes. As their name suggests, twin-tube shocks have two chambers, one containing hydraulic fluid and the other containing gas. Fluid flows between the two chambers under pressure, providing shock dampening. If the shock compression occurs rapidly, the fluid and gas can mix, called foaming. This majorly impacts the shock performance and decreases ride quality.
Internal monotube shocks eliminate foaming by using a single, larger chamber containing both the hydraulic fluid and gas separated by a floating piston. This prevents the oil and gas from mixing and allows for larger oil volume and better heat dissipation. Collectively this provides more damping, more travel, and a much more stable shock performance over a variety of terrains and environments.
Dobinsons IMS Benefits
When comparing the Dobinsons IMS kit to their twin-tube shocks, there are a number of noteworthy differences.
First, you can visually see that the IMS coilovers and rear shocks are beefier than their twin tube counterparts. The main body of the shock and the lower leg of the coilovers are significantly larger. This makes the shock much stronger, thus reducing the likelihood of a failure.
The IMS shocks have a larger 50 mm (~2″) billet alloy piston and larger oil capacity. This provides much better heat dissipation than the twin-tube shocks.
Additionally, the IMS shocks offer progressive valving, which has some benefits over the linear valving of twin-tube shocks. More on that below.
Beyond the performance characteristics, the IMS coilovers have a fully threaded shock body. This allows for complete adjustability of coil seat height, giving you the option to raise or lower the lift height. You can also add or remove preload to account for weight changes in the front of your vehicle. The shocks are also fully rebuildable and re-valvable, meaning a set of these IMS shocks can last you a very long time.
Dobinsons uses the highest quality Fuch’s German shock oil, and the IMS features a 3-stage sealing system. Despite being rebuildable, they should go quite a long time before needing to be rebuilt.
The front coilovers come unassembled by default, however, you can either have them shipped that way or pre-assembled for an additional cost.
When it comes to upper control arms, I wanted something that would have improved strength/durability, increase caster, and be low maintenance.
The Dobinsons UCAs checked all those boxes for me. They are made of HSLA (high-strength, low-alloy) steel, and are noticeably beefier than the OE upper control arms. There are 3 degrees of caster built-in, pushing the wheel further forward and away from the body mount. When I had these installed, we were able to get a little beyond 3 degrees of caster with no problem.
I personally liked the simpler design compared to other aftermarket UCAs, as I feel like they have eliminated failure points. They also come with Sankei 555 Japanese-made ball joints, which are sealed for a maintenance-free life. Along those lines, they use OEM-style rubber frame bushings, which again, require no maintenance.
A benefit of using these ball joints and bushings is that replacement parts can be sourced at a local automotive store in a pinch. In many ways, these UCAs are just a stronger version of OEM, and that simplicity was something I wanted for my build.
Overall, I’ve been very happy with the quality of these UCAs, and after several thousand maintenance-free miles, I have no complaints.
The ball joints do not come pressed in by default but you can pay a little extra to have them pre-assembled if you don’t have a press available to use.
The Dobinsons IMS kit performs exactly as I would expect a high-quality aftermarket suspension. It has significantly reduced the body roll when cornering, as well as nose dive when braking hard.
Compared to the Dobinsons twin-tube shocks, it feels just as planted, but the progressive nature of the valving has taken away some of the harshnesses. Speed bumps and potholes are smoother now, as well as an overall more comfortable ride compared to my previous twin-tube shocks.
If you’re going straight from factory suspension to IMS, the difference will be night and day. You will notice a combination of a firmer, more planted ride, but less jolting bottom outs when going over bumps, potholes, or the like. Overall, I’m very happy with the on-road performance.
Off-road is where this suspension really shines, and where you can start to notice all the benefits over the twin-tube shock setups.
As I mentioned above, these shocks have progressive damping. Simply put, this means that with smaller compressions (e.g. washboards, small rocks & bumps), the shock will be softer (less damping). They will then stiffen up (more damping) with larger compressions so that you don’t bottom out and maintain control.
These shocks have mild progressive dampening at low force input and have more linear dampening at higher forces. This provides a good balance of on-road handling and off-road comfort. According to Dobinsons, they perform similar to their MRR valving, which you can see here.
This is an oversimplification of valving and damping, and if you want to learn more head over to the experts at Accutune to read about progressive vs digressive vs linear.
At low speeds (<10 mph), the progressive valving really makes a big difference. It soaks up bumps and ruts on the trail much better than the twin-tube shocks. There have been numerous times when I’ve braced for a big bump expecting to get jolted around as I would with the twin tubes. However, I am instead surprised at how smooth the IMS is. Albeit, I have extended travel coilovers, which have more down-travel and probably play a part in this as well.
Overall I feel more planted and stable and feel like I have much less jostling around compared to the relatively stiffer, linear damping of the twin-tube shocks.
Medium-to-High Speed Off-Road
I live in North Carolina, so when I say medium-to-high speed, I don’t mean bombing through the desert at 70 mph. Going 40-50 mph down some forest service roads is about as spicy as I get over here.
The larger components of the IMS kit provide a lot more dampening and increase their performance greatly.
At these speeds, the shocks don’t feel quite as progressive or plush as they do at low-to-medium speeds. Some of the stiffness of the twin tubes is still present, just a little less harsh. They feel very planted and handle large forces (potholes, bigger rocks) at speed better than my previous twin tubes, so I’ve been comfortable driving faster on this suspension than before.
Overall, the off-road performance has improved in every category, with the largest gains being at low and medium speed. Improved comfort, stability, and durability are all factors that lead me to try the IMS, and it has lived up to my expectations so far.
I have found that suspension choices are often very subjective, and will vary greatly based on how you use your vehicle. For some, a very stiff ride is best because they want the best handling and on-road characteristics. Others may want a super plush ride and are willing to put up with a little body roll and nose dive.
For me, as a daily driver and 90% on-road, I wanted something that walked the line between on-road handling and comfort and performance off-road, and I really feel like the Dobinsons IMS nails that for me.
I have improved stability and handling on-road compared to stock. At the same time, I also have a more comfortable and forgiving ride than linear or digressive twin-tube shocks. When you combine that with comfortable and controlled off-road performance, this makes for an excellent kit for the weekend warrior like myself. I still like to get after it on the trails. Being able to do so enjoyably and confidently without sacrificing my daily driving has me very happy with the IMS kit overall.
I chose to pair that with the Dobinsons UCAs for a maintenance-free solution, and so far I have no regrets with these either.
Are They Right For You?
Overall, I feel like the Dobinsons IMS offers a ton of performance for their price point. For the weekend warrior who wants more performance than an entry-level suspension but doesn’t need a bypass or reservoir shock, this is a great option. It will serve you well whether you’re hitting the trails hard or driving the kids to soccer practice and everything in between.
(Special thanks to my friend Brian at Alpine Performance & Offroad in Troutman, NC for allowing me to photograph in his shop during the installation of this suspension!)