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!)
what tunning did you use on your Dobinsons? Comfort tune?
thanks a lot for this review, I was looking for for this kind of review long time.
I’m on the fence between this Dobinson IMS suspension and the OME BP51 suspension. I currently have Icon Stage 2 and think it’s a bit jolty, looking for a change. In your opinion after riding on both, which is your favorite?
Just had mine fitted sunshine coast 4×4 couldn’t be happier
I went with a nearly identical setup on my 4Runner after agonizing over the decision for far too long. I went from stock to IMS and the description in the article of “night and day” is totally accurate. I’m extremely satisfied with the Dobinson system and can finally stop all the silly sweating over making a “wrong” choice.
Really happy to hear that! We love it when something we work on for Trail4R leads someone in the right direction for their build!
How do they fare off-road? I have Ironman FCPs in my 17 TRD and every off-road adventure leaves me feeling like I’ve got whiplash. (Aired down to 16-18psi) I’m looking for something a little more forgiving.
The IMS suspension does really well off-road. I would say slow to medium speed offroading is where I noticed the biggest improvement over my previous monotube shocks. These feel like they soak up both large and small bumps better than before. Ive never used the Ironman foam cell pro shocks, so I can’t give first hand feedback. There are also certainly other factors that could play in like your spring ratings and things like that. I can tell you I did talk to someone a couple months back who switched from FCPs to the IMS and was very happy with their choice.
Hope this helps- please let me know if you have other questions
How would you compare this setup to a Bilstein 6112/5160, the OME 3″ lift, or the base Dobinson lift?
All those kits are going to be twin tube shocks. So all the benefits above about IMS will be true of this kit compared to those. If you look at the pictures of the Bilstein, OME, or Dobinson’s twin tube shocks, you can see the differences in shock body diameter and how much beefier the IMS kit is compared to those. The ride quality should be smoother with these than those kits, and should perform better offroad. That said, there’s a cost increase with those benefits, so any of those kits will work just fine. This will just be a step up from them.
FYI, both the 5100 and 6100 series Bilstein shock are monotube. That said, they both use digressive damping which, as I understand it, means they aren’t as good on rapid bumps but may control body lean and/or nose dive better. I’ve been looking at all of these options and leaning towards the Dobinson’s IMS because of the adjustable spring seat and the progressive/linear damping. I don’t really care about handling on pavement (on a lifted 4×4 it’s never going to be good), but soaking up washboard bumps on forest service roads is a high priority.
Nice write up!
I would love to know the exact coils you went with from Dobinson’s. Looks like you got a nice amount of lift.
Thanks Greg! I went with the C59-300 front coils. Those provide 2″ of lift along with the 574 extended travel front coils, which add 1″. So a total of 3″ front lift approximately.
Hi thanks for the info – did you replace the factory coils (front & rear) and did you have to add longer brake lines? What size tires? I am driving a 2016 SR5 4Runner in the woods, country roads, deep wet muddy/icy logging trials and in the cities of NH & ME packed with hunting equipment, camping gear, a dog, extra gas, water, etc. Roof rack & side steps. I’d like to add a few skid plates to protect from stumps & rocks. Thanks again for your time.
Hey Chris, thanks for the comment. My full kit is as follows:
Front coils – C59-300
Front shocks – IMS59-50574
Rear coils – C59-325
Rear shocks – IMS59-50701
This gives about 3″ of front lift and 2″ of rear lift. Tires are 295/70r17 (33.5″). I didn’t add longer brake lines, as that’s generally only recommended with 3+ inch rear lifts and long travel rear lifts. I have front skid plates and sliders (total 200#), a rear drawer system, a roof rack, etc. This past weekend I had 2 passengers, several hundred pounds of gear, etc. and there was very little squat in the rear, even with the stock load rear springs. Not sure how much lift you’re looking for, but unless you carry that all the time, I would recommend the stock weight springs from dobinson’s, rather than medium or heavy duty springs, as those will provide too much lift and be stiff when unloaded.
Hi Tanner, Thanks for the details, that’s exactly what I was looking for and I appreciate your time to respond. Now on to the build!
Good luck Chris! You’ll really enjoy it!