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RAS

RoadActive Suspension Kit

Part Number: RAS4521-T

547 Reviews

In Stock

$539.00

Not Confirmed to Fit

2006 Ford Explorer

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ras vehicle suspension towing/load leveling helper springs roadactive kit

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SCHEDULE AN INSTALLATION

2,000-lb Capacity. This kit upgrades your vehicle's factory suspension for improved stability, handling, and control. The mechanically active system eliminates axle wrap and wheel hop. Comes fully assembled and is easy to install. Great Prices for the best vehicle suspension from RAS. RoadActive Suspension Kit part number RAS4521-T can be ordered online at etrailer.com or call 1-800-940-8924 for expert service.

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Reviews (547)
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RAS Vehicle Suspension - RAS4521-T

Highlights

Custom Fit for Your Vehicle: Mounts to existing attachment points
2,000-lb Load Support: Keeps your truck level and stable when towing or hauling heavy gear.
No Maintenance Needed: Once installed, it works automatically with no adjustments required.
Smoother, Safer Handling: Reduces sway, body roll, and axle wrap for steadier control under load.
Stronger Rear Suspension: Adds strength to leaf springs without making the ride harsh when empty.
DIY-Friendly Setup: Arrives fully assembled and installs easily with no drilling or cutting.

Features to know about

Keep Your Truck Level and Confident: 2,000-lb Rear Suspension Support

Heavy trailers and bed loads can make the rear sag, throwing off your steering and braking. The RoadActive Suspension Kit adds up to 2,000 lbs of rear axle support to keep your truck level and balanced. The system strengthens your factory leaf springs so your ride height stays even whether you’re towing a camper or hauling gear. With a level stance, handling stays predictable and braking stays steady under load.

Smooth Out the Bounce and Sway: Mechanically Active Suspension Design

Uneven roads, curves, and sudden braking can cause leaf springs to hop or sway. This kit converts the standard rear suspension into a mechanically active setup that instantly absorbs and dissipates load force energy. That means less axle wrap, no wheel hop, and a stable ride that stays planted in corners. You’ll notice better traction and control without giving up ride comfort when unloaded.

Stronger Springs That Don’t Give Up Comfort

Adding strength often makes the ride harsh, but not here. The RoadActive Suspension design adds critical support to the existing leaf springs without compromising ride quality. It eliminates bottoming out while keeping your truck comfortable for daily driving or long hauls. You get the extra stability of a heavy-duty setup with the smoothness of stock suspension.

Install It Once and Forget About It: Fully Assembled, No Maintenance Needed

Getting better suspension shouldn’t mean days in the garage or constant adjustments. This kit comes fully assembled and bolts on with no welding, drilling, or cutting required. Once it’s installed, there’s nothing to maintain or tune—just reliable performance trip after trip.

Installed RoadActive Suspension kit mounted on a vehicle’s rear leaf spring, demonstrating positioning and fitment of the rear axle enhancement system.

Built for Ongoing Load Work: Added Safety and Efficiency

Vehicles that regularly run under load benefit in more ways than one. With improved stability and reduced body roll, you get safer handling, smoother towing, and less driver fatigue on long drives. The strengthened suspension also helps extend tire and component life while supporting maximum loads with confidence every day.

Specs

Weight and Capacity

Weight capacity: 2,000 lbs

Warranty

Warranty: 2-Year warranty

4521-T RoadActive Suspension (RAS) Standard Duty Suspension Kit

This Product Fits The Following Vehicles

1981 - 1995 Isuzu Pickup
1991 - 1997 Isuzu Rodeo
1992 - 1996 Isuzu Trooper
1985 - 1989 Isuzu Trooper II

4.7

547 reviews

5 Stars		(446)
4 Stars		(66)
3 Stars		(16)
2 Stars		(7)
1 Star		(12)

by: SamW 06/21/2026

2026 GMC Sierra 1500

Just perfect to level the rear of my GMC 1500 Denali with the 29' Airstream (900 lb tongue wt). Preload is set at 1mm. I tried 2mm and it was overkill for this application. I was pleased with how easy the install was. I had to use a two jack hack to get the rear tires off since my 19" lift floor jack didn't quite have enough reach. You lower the differential after the tires are off so the rear axle is hanging free for the install. See photos

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Mike L.

6/23/2026

Nicely done, Sam! Thanks for the photos, we always appreciate those!

by: John 09/13/2025

2022 Toyota Tacoma

The install takes about 30 minutes with a floor jack and jack stands. You do not need to remove the center tension bolt just lengthen it out. Lay the assemble over the spring and install one bolt on the ender side. Snug up the spring to desired % of tension and you are good. I did not remove the tires there is no need as you can get to everything. If you can not secure the frame in the upright position with stands I would remove the tires for safety.
The good is the brackets fit nice on the leaf springs and at 25% (the white washer) it lifted the truck 1.5 inches.
The bad is the enhancement bracket that passes by the leaf spring on the drivers side rubs against the brake line hard. I am pretty sure this is an issue with the Tacoma pickups if you look on line. Customer service at etrailer gave me the I don't know you need to contact the manufacturer. Own up and do not pass the buck is my response to that answer. My fix was to loosen the hold down bracket on the brake line under the leaf spring assembly and add 2 washers behind it to move it out away from the plate 1/8 inch. While doing this and before retightening this bracket bolt I also loosened the line bracket bolt fixed to the axle farther to the right and rotated it a little while bending the brake line ever so slightly to create a 1/4 gap between the break line and the enhancement kit bracket when it was tightened back on.
My two cents.

John One Year Later

9/14/2026

Well It has not failed me yet. Being basically a spring under load all the time I am assuming the spring will stretch some over time and I will have to adjust tension accordingly. The pickup sits nicely on the thinner washer setting so I am leaving it there and hopefully that will help the system last longer.

by: Raymond 02/24/2026 One Year Later

I don’t think they are really made for the old PU. 1997 k1500 8 ft bed with a 750 lbs camper tong weight I think I had to put to much pressure on the Kurt stabilizer chains to get level. It looked like the newer truck reviews on YouTube were great thanks Dingler.

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by: Les 06/22/2025

I purchased the RAS system 6 months ago to help with rear end sag & control while towing our 22 ft 4200lb camping trailer. It improved sag & helped handling even when not towing! I don't get the bounce when driving on bumpy uneven roads the wheels stay planted on the road. I recently purchased a 8000lb camping trailer & my 24 1500 Silverado handles it very well, I will adjust the RAS to the next step up for the extra weight when time permits.
The install took just over an hour with help from a friend & a car lift which is good since I'm 70 years old.
Great product!

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Brooke M.

6/25/2025

Looks great, Les :) I hear lots of good this about this option for suspension enhancement and how you said, even without towing it can improve the ride quality. Glad to know that you are happy with them, too! do you have any upcoming camping trips planned?

by: Scott 09/17/2026

Ford F-150

Installation was very simple. Watched many installation videos and had no issues with installation. Wanted to gain an extra 1 inch in height in the rear on my F-150 while towing my travel trailer and actually gained 1.5 inches in the rear and only lowered the front by 1/4 inch. very satisfied with it so far.

by: Vince 07/29/2025

I’ve bought a lot of products from etrailer and as always everyone I dealt with is professional and knowledgeable of the numerous products they sale. I used every resource they offer to help me decide what type of suspension upgrade I was going to use to improve the haul and tow ability of my 2017 diesel chevy Colorado 4x4 crew cab short bed. I chose the RAS system from Roadmaster. I also called them and ask some very detailed questions about using my OEM shackle instead of replacing with the plates in the kit and was told that was fine and that others had also. I got professional and knowledgeable info that helped make my decision. The product is exactly as promoted and every review out there on the internet about how good or unchanged the unloaded ride is after installing are true. My truck rides better now and it was already quieter and almost as smooth as my wife’s Cadillac. If your looking to improve the drive, tow and haul ability of your leaf spring vehicle, and I say vehicle instead of truck because I don’t know if they have them for other leaf spring vehicles, you are not going to find a better easier to install product that does that for your loaded or unloaded vehicle, IMHO. I will update in a year after next spring mulch haul. I don’t expect zero squat but hope to reduce and improve loaded steering performance. Took longer to jack up truck and remove tires than install kit.

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by: Stephen 07/17/2026

Ford F-150

2023 F150. Install was fairly easy. Set at 25%. Ride unloaded a bit stiffer, but handling much better. Lifted rear of truck about an inch. Towing 7500 lb camper down NYS thruway which is crowded with much unforgiving bumps and pot holes the ride was more manageable. The 25+ mph cross winds did make for quite a bit of sway still, not as bad as before adding the RAS. Still felt passing trucks trying to suck me in, not as bad as before.
I plan on cranking the RAS to 40% on next camping trip and hopefully give the RAS 5 stars.

by: Paul 08/18/2025

2022 Toyota Tacoma

Easy install when I rotated tires. Forgot to measure height difference, but it did raise a bit. I like the adjustability and not having to remove springs and shackles to add a leaf. Will be towing the camper with improved support.

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by: Elden R 07/08/2025 One Year Later

Helps immensely, 12x6 inclosed trailer from NY to Florida and back up to NJ no problems

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Gwendolyn Y.

7/23/2025

That's a long trek, so I'm glad these helped you along the way! Do you take that trip often, Elden?

by: Jeff 06/08/2026 One Year Later

Nissan Leaf

Great product, helps with sway and when the truck has additional weight it progressively compensates. I would add this to any vehicle with leaf springs.

by: Sergio 08/12/2020

2011 Nissan Titan

The bed of the truck measured 37.5" with a tool box weighing 200 lbs. The truck felt weighed down with passengers weighing 600lbs. Total weight 800lbs with a tank full of gas. After the install the truck rides smoother and certainly " like new". The stopping distance and acceleration distance have shortened drastically. I'm planning on loading up the bed and the Roadmaster Active Suspension RAS4611. My wife even drive it and she could feel the difference. "It drives like a muscle car." Buy it. Install time at a reputable mechanic shop was a 30 min. Install. I received them today at 1 pm and got it installed at 3:00 pm and finished the install at 3:30pm. It's an investment worth the price over traditional air bag system. Mechanic installed this on 2011 Nissan Titan SV.

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Sergio J. One Year Later

8/13/2021

What can I say. After a year of constantly driving through Texas roads and highways. I have moved twice and loaded the bed of my truck plus U-Haul 6x12 trailer and thy truck has not felt the load of it. The Active Road Suspension Leaf Spring is constantly sort of speak sensing if theres load so it can actively push it upwards. I have even driven up to the crazy roads of Pennsylvania and my pick drives smoother than when I got it from the dealer. Im telling you these things work. As any cautious driver upkeeping his own vehicle, I have periodically checked the bolts and location of the resistance in between the spring and it has not deflected or moved from its original installation. I believe every pick up must have these. It beats constantly putting air on the air bags especially in inclement weather like up here in Pennsylvania with the snow. I couldnt be more satisfied with this purchase. Thank you etrailer for offering this superb product.

Sergio J. One Year Later

8/16/2021

Just like when I bought it.

by: Miguel 07/09/2021

I love the product since i have a 2021 toyota tacoma crew cab long bed with a campertop a robber mat and a jack thats around 450 pounds that a have at all times my truck was sittind low a lilbit plus it was swagging on the road i have summo spring to help my suspention but it was not enoght so i did my research but this was my better option i just installed it yerterday july-8-2021 and went for a ride where i ussually drive everyday and WOW now my truck rides very smood plus it lift my tryck 1 inch on the back now my tryck seats level it took me about 2 hrs but i did right i just follow the intructions and done i love the product the only thing that im concern is that the left side underneat the springleaft there is a breik line that is too close to the roadmaster suspention i hope that with the time dont hit that line because if it does thats the line for the breiks and i will be in trouble replacing it other wise evreything works great i recomend it 100% thanks guys i will buy it again?????best $500 that i spend on my truck

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Miguel One Year Later

7/10/2022

Its been working very well i loaded a couple of times and its awesome

by: Rick Maybury 03/26/2021

I have a 2020 Silverado 1500 6 cyl Duramax with the Diesel Off Road package (3.73 diff). Travel trailer loaded is probably about 6,000 lb. I took several measurements during and after the spring kit installation. All measurements increased about an inch including the stock suspension with trailer and equalizer bars and with the spring kit installed at 1 mm spacing. A one inch improvement overall. I took the truck on a short drive and didn't notice any difference in ride (wasn't stiffer) which is what I wanted. Good to know that I can adjust the springs to the 2 mm spacing if I want to increase the suspension assist. Going camping next week and looking forward to see how it improves handling and porpoising.

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Rick M. One Year Later

3/27/2022

After a year I am still pleased with this product. I had been adjusting the spring tension higher when towing and then back down after a trailering trip, but now just leave it adjusted to the trailer towing tension as the unloaded ride doesnt seem to suffer when the springs are tighter.

by: Bruce 08/14/2026

These made such a difference in the ride of my pick up while pulling my enclosed trailer. Let’s squat more stability.

by: Rich 03/05/2020

2011 Toyota Tacoma

Easy install 2011 Tacoma crewcab long bed. Helped with sag when towing microlite travel trailer. Keeps the rear end raised in the rear a little when unloaded, but I like that look. Only complaint and its nothing big when truck is unhooked and empty when i get out I can hear alittle noise from RAS. Sort of like a bedspring coil. Night pic is with RAS installed daylight pic is with out installed

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Rich One Year Later

3/10/2021

Still working great. Towed a Flaggstaff microlite 23LB Travel trailer prob between 5 and 5500 LB’s to Niagra Falls with no problems, truck sat level with trailer and 2 adults,2kids. Getting ready to make a 2,000 mile round trip to disney in florida in a few weeks.

by: Mark 03/27/2026

2017 chevrolet Silverado

I haven't hooked up my camper yet but set the springs up with the white wafer and it raised my truck 1 1/2 inches which is the amount it dropped after I put on a fiberglass topper. The ride is just a bit stiffer but a lot less body roll I noticed. Not impressed with the 25 Silverado suspension compared to my previous 2017 truck. If the squat is still there after I hook up the camper, there is plenty of adjustment left.

by: Brent k 04/09/2026

2001 Nissan Leaf

i installed these on my 2001 ford f-250 4x4 and this is a huge upgrade whether your towing or empty.truck rides and handles better than it ever has. easy straight forward installation. you will need a t-55 for the front bolt and a 12mm ratchet wrench for the adjustable bolt that tightens the spring and a couple of 22mm and a 19mm wrench or crescent wrenches for the jam nuts. i took the weight off of the leaf springs for easy adjustment of the coil spring and used the thinner of the two disc that came with the kit and it raised the rear of the truck up exactly 1 inch empty without a trailer connected. if you use the thicker disc it will raise it more.

by: William 03/20/2020

2017 Ford F-150

I found this items cheaper on another site but etrailer match and then beat the price.
Item installed super easy, more work jacking up the truck and taking the tires off. Can be installed with out removing tires just make it easier to get it in. The item did lift the back of my truck 1 inch. See Pics.

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William One Year Later

3/30/2021

Makes the ride a little stiffer but its a truck. Great when pulling my 37 camper. Helps out a lot!!!!

by: Alan 04/28/2026 One Year Later

Did not fit my 1995 F-150. ETrailer was very helpful in an effort to make any adjustments needed. We all decided that they were a "no go" for installation. Return was made easy. I have bought several other pieces of gear since. Thank Etrailer.

by: ACE 07/11/2026

I have put these on every pickup that I have owned and not only does it assist with heavy loads, my tires have gone past 80,000 miles before needing replacement. All Chevy Duramax 2500's and 3500's!!

by: Russell 09/01/2022

I received this kit in a very timely manner always do from etrailer have some issues with the instructions that come from roadmaster not a trailer the bump stop spacer didn’t say that you need to use the original bolt from the bump stop so it slowed me down greatly on the install however I took it out on a quick run without a load I do feel that this has made the unloaded ride smoother tomorrow I’ll be taking the trailer out for a bit and we’ll see how it works there and I’ll update this rating.

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Russell One Year Later

9/2/2023

OMG!! I have done extensive traveling with my trailer over the last year and the RAS system has made a huge difference in sway, road buffeting and squat. I can’t imagine not having this on any vehicle that tows!

by: William 03/21/2026

ford Ranger

Balances ability to tow my 1800 squaredrop Hiker camper with 350 tongue weight as well as roof top tent on Leer 180 camper topper. Better handles load and side to side tipping on '21 Ranger. Keeps sage to a minimum.

by: Michael 06/21/2022 One Year Later

Overall, very happy with the product. GMC didn't have any way to improve the truck from squatting when I hooked up my trailer. This kit didn't stop the squatting but significantly reduced the bounce on bad dips in roads, bridge/road transitions and bad railroad crossings.

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Michael One Year Later

7/7/2023

Removed the Suspension Enhancement and installed Airlift. Cost more but rear-end isnt sagging 4.

by: Jeff 05/22/2024 One Year Later

Straight-forward installation on a 2007 Pleasure way Excel RV (I did it myself in a few hours) although I did have to modify the air bag mounting bracket with a slot to allow RAS hardware to fit. Great installation instructions. Vehicle height is now correct and could be made level by tension adjustment during install. Handing is improved, I was able to remove aftermarket sway bar which improved ride. I have been considering installation of stiffer rear shocks to soften rebound now that the rear spring rate is increased.

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by: QM 06/29/2021 One Year Later

Night and day difference on our 2011 F150. Before installing the vehicle was almost undrivable at highway speeds due to bouncing/jerking when pulling our trailer. The bounce/jerk has been virtually eliminated since installing the Active Suspension. Installation was a breeze, hardest part was getting the wheels off the truck due to corrosion between the wheel and the rotors. Total install time was roughly 1hr 15 minutes including the stubborn wheels. Initially I was hesitant to order due to the price, but very happy with the results, etrailer also did a great job at guiding me through the process, shipping and answering a few technical questions along the way. Highly recommend if you need a little more spring/payload.

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Info for this part was:

Written by:

Mary K

Updated by:

Wilson B

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