1986 – 2004 Toyota Pickup
Kit Number: 4521-ST


*Due to an increase in sales volume, expect a 3 week lead time unless otherwise noted.

All kits include FREE GROUND SHIPPING to the contiguous United States. Alternative and expedited shipping is available if needed.

Kit includes an easy to install Active Suspension for each rear leaf spring. Without having to interfere with u bolts, installation will take approximately 1 hour. Roadmaster Active Suspension kits are designed to strengthen the rear leaf springs. This kit will significantly improve stability, performance and handling while reducing bounce and rear squat when loaded.

Installation Guide





Depending on the application for your vehicle, we have STANDARD duty and HEAVY duty kits. Find out which is best for your Vehicle, below!


STANDARD duty kits are designed mainly for 1/2 ,3/4 ton pickup trucks and vans that have rear leaf spring suspension setups. They can also be used on 1 ton pickup trucks that experience up to roughly 1-2 inches of squat when towing/hauling OR are simply looking for improved performance. When installed, this kit  is guaranteed to reduce rear squat and improve load management, improve stability, overall handling, reduce body roll when cornering, reduce bounce, eliminate axle wrap, wheel hop, and make your vehicle safer. These STANDARD kits will also provide a smoother more comfortable ride with or without a load. These kits are NOT designed for 1 ton pickups that have overload leaf spring located above the pack of leaf springs. Truck with factory TOP overload must utilize our Heavy Duty kits.


HEAVY Duty kits are identified by the letters HD located at the end of the part number. These kits are the ideal application for 1/2, 3/4,1 ton that experience roughly 2-4 inches of rear squat when loaded. The HEAVY Duty kits feature 50%  stronger coil springs with certain components larger than a standard kit and is recommended for applications where typical loading situations include the tongue weight or payload approaching the specified limits of the truck. When installed this kit will greatly reduce squat and improve management, while still offering all the great benefits of the standard duty Roadmaster Active Suspension and providing a smoother more comfortable ride with or without a load. Note* If the vehicle has an overload springs located above the pack of leaf springs, this overload spring must first be removed before the kit can be installed.

*Any factory TOP overload springs must first be removed before installing kit [As per fitting instructions]. *


Our kits fit a 3″ wide leaf spring with shackles that swing from the BOTTOM UP or TOP DOWN.

Below is a visual of what it looks like if  your shackle swings from the bottom up.


Below is a visual of what it looks like if your shackle swings from the top down.


If you are still unsure of your shackle position give us a call at 800-398-5036 and we can walk you through it.

30 Day Money Back Guarantee
Weight 24 lbs
Dimensions 31 × 6 × 10 in
How does Roadmaster compare to other rear leaf spring suspension products?

How Roadmaster Compares To Other
Rear Leaf Spring Suspension Products



Sway Bar

Helper Springs

Active Suspension

Reduces Vehicle Sway

Reduces Dangerous Roll in Cornering

Improves Fuel Mileage when Loaded

Reduces Axle Wrap & Wheel Hop

Eliminates “Bottoming Out”

Improves Hard Braking & Acceleration

Improves Towing & Load Carrying Abilities

Improves Driver Control with a Load

Improves Stability in Cross Winds

Extends Tire Life Significantly

Prevents a Harder, Stiffer Ride

Easy to Install

Can an authorized dealer help me with installation?

While the installation of our kits are considered simple and among the easiest in the industry, Roadmaster Active Suspension dealers possess installation experience and industry knowledge for those more comfortable with professional installation. Click here to find a dealer near you.

How does Roadmaster Active Suspension work?

Roadmaster Active Suspension (RAS) kits consist of a set of two very powerful, variable rated coil tension springs that when installed support and assist the rear leaf springs by holding them in their (Original designed) bowed position. When downward strain from load or vehicle weight shift is applied to the leaf springs, the stabilizing action of RAS comes into action immediately absorbing the force of the load. The greater the strain, the more corrective counter assistance force is applied from the RAS spring.

Is RAS easy to install and do I require special tools?

RAS is very easy to install and should take about an hour. Fully assembled out of the box with a set of easy to follow step-by-step fitting instructions, complete with pictures! For ease of install you will require a two post auto lift and standard shop tools. RAS can also be installed on the ground using a trolley jack and jack stands.

Will RAS reduce sway and roll when cornering?

Yes. RAS will greatly reduce body sway and roll in cornering. Roadmaster’s powerful coil spring supports the weight that shifts onto the rear leaf spring that is taking the additional load. Holding the leaf spring in a bowed position (not allowing to flatten out) maintains a more level vehicle on turns and curves.

Will RAS fit on a truck with a lift kit?

Roadmaster Active Suspension kit specs are based off of stock vehicles, without any aftermarket suspension modifications. From a fitment standpoint, RAS generally fits lifted trucks without an issue. An issue may arise if the lift block is fabricated in an odd shape that interferes with our axle connecting brackets, or if it's a complete suspension swap. Before ordering a RAS for your lifted or leveled truck, be sure to check your suspension to look for possible issues as described. If there appears to be an issue as described in either one of these two instances, email us at sales@activesuspension for assistance and further instruction.
Provided fitment is not an issue, RAS works great on lifted and leveled trucks from a functionality standpoint, greatly reducing squat caused by towing, significantly improving stability, excessive bounce and any axle wrap/wheel hop.

Will RAS help get rid of my squat?

While RAS is geared towards significantly improving performance and overall towing experience & capability without hassle (by improving ride quality, significantly reducing sway, bounce and body roll), one of the most noticeable visual benefits is reducing rear squat when towing or hauling. Because the RAS works in conjunction with the existing leaf springs (that vary greatly in rating), the amount the RAS reduces rear squat will vary as well. Generally, a pickup owner experiencing 2-3 inches of squat should expect the RAS to keep that truck level or extremely close to level. For vehicles experiencing over the 2-3 inches of squat, RAS will still help and an improvement should still be seen, but remaining perfectly level should not be expected.

Each kit is tailored to your specific vehicle

Roadmaster Active Suspension is uniquely assembled for your model and ships out the day you order! Roadmaster Active Suspension is the only suspension upgrade on the market that is made to fit your rear leaf spring suspension.

Roadmaster Active Suspension kit comes fully assembled out of the box and ready for installation. Follow your application guide that is in the box and you will be ready to test your Roadmaster Active Suspension in about 45 minutes! If you are not satisfied with your Roadmaster Active suspension we offer a money back guarantee.

Product Benefits
  • Eliminates Axle Wrap
  • Simplifies Load Carrying
  • Improves Roadhandling
  • Makes RV’s Safer
  • Saves Fuel and Wear on Tires
Warranty Information

Roadmaster Active Suspension kits are warranted for 5 (five) years from date of purchase, against defective components and materials. However, kits cannot be warranted if any changes or modifications have been made to any rear leaf spring suspension components on the vehicle you intend installing the kit on.

If you would like to complete our online Warranty Registration, please click here.

Return Policy

Roadmaster Active Suspension provides a 30 day money back guarantee, from date of purchase. However should the kit be returned, it must be re packed in the original packaging with all components included. The customer will be responsible for the return freight charges.

Take a look at what other people are saying about Roadmaster Active Suspension

I had your suspension on my smaller, older Tundra and it made an enormous difference in the size of the loads I could haul and tow for my Handyman business. There was no question after purchasing my newer Tundra that I was going to install another RAS as soon as I could. It allows me to safely haul and tow the loads that I need to in order to service my customers.
Thank you!

-Pete K. on August 12, 2020

Very satisfied! I've tried many other types of suspension upgrades in the past on other trucks. This system by far is the best!

-Michael M. on July 23, 2020

It's a smooth ride and I don't have to mess with air bags. Best investment I made for hauling. Installation was easy.

-Dustin J. on July 14, 2020

I installed this on my chevy pick up when this was a new product on the scene. It was the best suspension upgrade. Much improved ride over bumps, and also handled turns like I had installed a rear sway-bar. Awesome product.!!

-Tom W on June 20, 2020

Made a big difference on my 2013 f150. took me longer to kack the truck up and get the wheels off than it did to install both sides. Really noticed the difference the first time I took it out and drove over the roughest railroad crossing I would almost have to stop for. Big difference. Can't run right over it now at speed with no weight in the back. Tows my 28 foot camper way better than the old airbag system that I had to tear off my truck.

-William S. on June 17, 2020

Awesome upgrade to my F150, I didn't want to put air bags on because I had enough on my electric system. This was an awesome option. My truck towed our camper good and this just made it better

-Tim C on June 1, 2020

Awesome upgrade on my F150, I didn't want to put air bags on because I had enough electric system. This was an awesome option. My truck towed our camper good and this just made it better.

-Tom C. on May 28, 2020

If you're on the fence DO IT, you won't regret it. For 2 years I fought the rough ride of bags. Normal driving and towing. With the camper I made so many adjustments with the hitch and air pressure and could never get rid of the bouncing especially hitting the bridge abutments. With the RAS there is none of that. My wife even looked over at me and she couldn't believe the difference. Rough roads, pot holes it just soaked them up. I HIGHLY recommend them. Also RAS has a money back guarantee, can't go wrong with that, but I guarantee you won't want to.

-Scott Shafer on May 18, 2020

I had Roadmaster Active Suspension on my 2013 F150 to help pull my camper. When I recently picked up a 2016 F150 Ecoboost there was no question I was going to add them again. I have to say the results are even better! Without a load, the truck handling improved significantly with my Club Car Precident golf cart in the short bed, I can hardly tell it's back there after installing the Roadmaster Active Suspension.

-David Brady on May 9, 2020

Hated my truck sagging and always struggling with towing and just poor handling. Have had add leafs and air bags in the past and tried the HD kit for my f150. Wow, rides smoother and stable then stock and tows way better, almost no squat and keeps the trailer tame. Will never not have this product on a vehicle again.

-Luke Ryan on April 27, 2020

I used to know squat...so much better not looking at the sky now. I've had it about 3 months installed and wow what a difference it has made.

-Joe Joe Dodwell on April 10, 2020

Super easy install. Between the instructions and Youtube Videos and taking my time, was easy. Set the smallest setting for "25%" assistance. Again, haven't towed or hauled anything, but noticeable difference driving. Truck actually feels much smoother, less roll in turns, smoother over big road imperfections.

-Eric M. on March 15, 2020

Installed mine today on my 2019 Silverado 1500 4x4. Obi-wan would be proud! No drift in the rift, no sway along the way. Rides like a dream!

-Charles French on March 15, 2020

When we bought our horse trailer I immediately knew I needed something to help with the suspension on my truck. I did my research and came across the Roadmaster Active Suspension and decided to try it out.. to say I’m impressed is an understatement.. rides great loaded or empty, stops my truck from bottoming out when loaded heavy and just makes towing a much safer and more all around enjoyable experience.

-Justin Meyerhoff on March 9, 2020

I'm so impressed, well engineered, model specific, fits first time!
I installed it on a 2001 Ram 2Wd, to pull my travel trailer. It performed very well and greatly reduced tail wagging when being passed on the interstate!
The 3100 lb trailer required no sway bars using the Roadmaster Active Suspension. I thought it was pricey at first, then installation was a breeze, after putting it to the test pulling my camper!
I would be happy to recommend it to anyone! It actually works!!

-Rick Walls on March 5, 2020

The lack of squat made me very impressed. The performance of the kit speaks for itself for anyone who uses their truck as a truck, but what stands out the most is the customer service and the confidence in the money back guarantee that is behind every kit. I'm comfortable saying that this kit is something I will install on any vehicle I own going forward.

-Peter Novobilsky on February 16, 2020

I put these kits on everything! so much less hassle than air bags and the ride quality is far superior!

-Just Trost on February 13, 2020

My trailer always bottomed out my suspension so I did my research and bought the Roadmaster Active Suspension. I installed it, which was very easy and it changed the ride of my truck for the better. It (my truck) has never ridden so smoothly and when I pulled my trailer it was like it wasn’t even there. Great Product I will buy again for other trucks.

-Bryan Hale on February 12, 2020

I’ve had Roadmaster on my 2010 F250 for 4 years. Love it! We are full time RV and I love the stability control that Roadmaster offers. Huge difference pulling a 14,850lb 5th wheel

-M.P. Buck on January 13, 2020

Just the road handling after the install was amazing basically feels like it sticks to the road like a sedan instead of a 4wd truck. I originally was getting them for towing but the road manners made them worth the money.

-James Courtney on December 28, 2019

Just installed your kit on my 2019 F150. Very nice piece and install was a breeze. Thank you!

-Phil K. on December 26, 2019

I am now rocking the new (F150) HD kit. I was amazed that the ride quality was every bit as good as the standard duty kit that I had installed for over a year!

-Eli Hauschild on November 17, 2019

The ride on my truck is much better after installing these. Loaded, control and unloaded. Just amazing.

-Ray E. on November 12, 2019

Bought these and put them on my 2014 GMC 1/2 ton crew cab to haul my travel trailer, changed my ride immediately, removed the bounce on bridges and the sway motion. Would recommend to anyone doubting.

-Andrew S. on November 7, 2019

I love the system, easy to install and adjust. Extremely well made parts. My truck rides better now empty than it did before.

-Brian Vancleve on November 5, 2019

Works awesome on my 2013 F150 long bed. I put my Arctive Cat Trail in the bed and pull a 25' travel trailer with no rear sag at all.

-Walter P. on October 30, 2019

Finally no sag, no loss in the Denali ride. Gained +2'' hitch ball height. She corners better too. Amazing.

-Grant C. on October 2, 2019

While doing my due diligence in researching many different items on the internet to improve overall stability on the rear end of my truck I’m happy to say I made the perfect choice. I ordered my part and was awaiting arrival. However due to unforeseen weather conditions my package was stuck at UPS while the hurricane battered the state. I reached out to RAS company for help because I needed the part for my trip. They responded promptly with a plan to get me what I ordered. They made special accommodations and had another part sent overnight to me so I could have it in time. Outstanding Customer Service with prompt and pleasant responses to me. I would HIGHLY recommend going with a company that has high standards in Customer Service no matter what you buy. That being said why go anywhere else when you have, both the best product on the market, and Excellent Customer Service with Roadmaster!!

-Joshua P. on September 13, 2019

These things were an easy install and live up to the hype. I took the camper on a test pull after installing the Roadmaster Active Suspension and my truck pulls at highway speed with no sway or hop or anything. This product is amazing and true to the claims.

-Mark Overmeyer on September 7, 2019

Love them! Roadmaster Active Suspension rides so nice.

-Brandon Moore on August 27, 2019

I've installed them (on my 1 ton) and love them what a game changer!!!!

-Scott S. on August 21, 2019

These work great, got them on my Titan XD for my heavy tongue toy hauler, also had a set on a Sport Trac several years back, ride quality does not suffer when unloaded, but improved loaded

-Doug B. on August 19, 2019

I have tried about everything out there for aftermarket helper springs. Pretty much like everyone else says airbags ride like a tank and other leaf springs are either too stiff or bouncy.
I pull a landscape trailer every day as well as a heavy dump trailer and 6000 pound boat.
I put the (Roadmaster) Active Suspension on my 2019 F150, I'm really not sure of the engineering how to’s, but these things work better than I ever imagined.
It keeps the back end from squatting and it also keeps it on the road on rough roads and washboards no matter whether you’re unloaded or pulling a heavy trailer.
I will never buy another system other than these (Roadmaster) Active Suspensions. If you’re needing extra capacity and stability for your truck you would be smart to buy the (Roadmaster) Active Suspension system and forget the trial and error and waste of time and money of anything else.

-Chris C. on August 13, 2019

Thanks for the great service, the fast delivery and your great product. I've installed the kit asap and it transformed my truck. The ride quality is amazingly good now. Stability on the highway is great and it corners like a much lighter vehicle.

-Marcus K. on August 11, 2019

Love them on my 2017 F150! Hands down the best suspension accessory on the market.

-Jake B. on July 24, 2019

One of the first things I added when I bought the truck. Had air bags once and never again. Your product really does work great

-Rob Ryder on July 19, 2019

Made the rear sooo much more stable than without.

-Eli H. on July 3, 2019

I had these installed 2 days ago and I love the results. Thank you!!

-Diego on July 2, 2019

Thank you Roadmaster. My axle-wrap is cured. You saved me from not being able to tow our new fifth-wheeler

-Dan L. on June 29, 2019

Worked as advertised on my 2015 6.2L Chevy towing a 33' trailer.

-Lewis on June 11, 2019

I love mine. My Tacoma is hooked to a 4,000 pound trailer most of the time and it sits like no trailer is attached. When I do unhook my trailer my truck drives more like a car. I will never own a truck with leaf springs without this add on.

-James L. on May 22, 2019

Over 300,000 miles on 4 trucks. Never let me down.

-Bill C. on April 18, 2019

I bought a new Ford Excursion in 2002. Shortly after buying the excursion I started experience wheel (hop). I Found your company on the internet and bought your product. Your Active Suspension has over 335500 miles on them and is still doing what it was designed to do! Great product and has been maintenance free.

-Jay F. on February 19, 2019

I wanted to thank you for your excellent help when purchasing a Roadmaster kit for my Ford F-150. Also want to say thanks for the very speedy response to my order. I installed my kit with no problem and the installation guide was very easy to follow. No spring stiffness at all and the body did not roll or lean at all when cornering! Thanks again for all the help, and for one of the few times in my life I am talking up a product.

-Ron H. on October 25, 2018

As a FedEx Ground contractor and owner of a Dodge Sprinter Van, I just wanted to let you know that with a Roadmaster Active Suspension now installed on my vehicle, it has not only greatly improved the load carrying and handling, but also makes my van feel much safer. On average I drive about 1000 miles a week. The Roadmaster allows me to take corners with more confidence. Best of all the Roadmaster is saving me money. I am saving on fuel economy and tire life. I am saving about 6 gallons per week. I believe the Roadmaster is a must have for any long wheel base vans or trucks. For a small business owner like myself, the cost of the Roadmaster and all the advantages it offers, has been worth the price. It has paid for itself in a matter of months. Thanks for a great product.

-Phil R. on June 20, 2018

I am an insurance agent for GuideOne which currently recommends installation of your product on 15 passenger vans in order to be eligible for commercial coverage. I personally own a 2000 Ford E-350 because of having 10 children. I installed your product for my own experience. This product is unbelievable. It is a completely different vehicle. I am not just recommending this product, but pushing it for safety sake. Thank you again.

-Ron F. on July 5, 2018

I just want to take a minute to let you know how thrilled I am with the Roadmaster products I purchased. I have driven a sport utility vehicle for years and they have the reputation of an unstable ride. As soon as the Roadmaster system was installed on the rear leaf springs I noticed a tremendous improvement in the handling characteristics. Even while applying maximum breaking, I noticed my truck was easily controlled and the weight transfer was less severe. I would recommend this to anyone owning a truck or van. Thanks again for such a great product.

-Ron W. on January 7, 2018

I want to thank you again for such a great product!!

Was easy to install and made 100% difference. No more bottoming out and with the suspension I have got under my car, it'll all be saved now. The handling was even different - much better - and cornering was like hugging the road.

I am still excited about this product. Thank you again for such a wonderful assist to my vehicle.

-Reitha G. on August 15, 2018

I just want to let you know that after installing Roadmaster Active Suspension on my Dodge Ram I am thoroughly impressed!! I have owned this truck since it was new and there have always been a few things about it that have bothered me. After installing your product all of those problems went away. The first thing I noticed was that the bucking feeling was completely gone. The truck no longer squatted down when I loaded it up either. I cannot tell you how happy I am with this product and the fact it does everything as advertised!

-Joe D. on April 5, 2018

Thank you for developing such a wonderful product that provides a sense of safety and security to those of us with 15-passenger vans. One of the greatest fears of owners of these vehicles is how they will handles in emergency situations, particularly in conditions that could provoke a rollover or loss of control of the vehicle. Your product provides invaluable peace of mind, knowing that our vehicle is optimally configured to give us the best, most secure, handling in these situations.

Thank you for providing us with a quality safety tool and for providing excellent customer service. I'm a very happy RAS customer and look forward to purchasing more from you in the future as we grow!

-Nathan on December 16, 2017

As the manager of a small fleet of maintenance vehicles I have been thoroughly impressed with the Roadmaster Active Suspension units performance and the expense savings. Immediately after installation the trucks drove like they were brand new, the ride height was restored and all body roll was eliminated. We have been able to load our vehicles like they were new once again. We plan to put them on all of our vehicles in the future.

-Ed H. on March 29, 2017

Thank you for a fantastic product. It has made major improvements to the suspension of my truck. I was skeptical at first but with your 30 money back guarantee it was a no lose situation. The improvements were amazing just like your ad stated. I put them to the test day one and loaded my truck with what would normally cause my truck to bottom out. I couldn't believe the way my truck handled with the load. I will recommend this to all my friends with trucks!! Thanks again.

-Greg G. on March 20, 2017

I want to let you know how extremely pleased I am with the Roadmaster Active Suspension that I purchased. I was skeptical at first, but decided to give it a try. I carry very heavy truck mounted carpet cleaning equipment in my Maxi-Van and have been using a Dodge 3/4 ton van for years. I recently bought a 3500 van hoping that it would give me more stability. Even with the heavier can I still experienced instability and a lot of sway. When I turned a corner, it felt like the van wanted to turn over. The Roadmaster has corrected that problem. It is just fantastic. Now my van runs level and when cornering the van is right there. This product is what I have been looking for.

-Chuck G. on December 6, 2017

This product is the greatest thing I have done for my truck to help accommodate the weight of the trailer. Roadmaster took out any dips or bumps in the road. Let me again say thanks for your help in making all of my trips from here on our the easiest in my 31 years of RVing.

-Vernon S. on August 2, 2017

I am writing in regards to the recent installation of the Roadmaster kit to my Lincoln pickup. I absolutely cannot believe the difference it has made. The truck seems to ride more level and smoother over road bumps and uneven surfaces. The most notable difference is the handling in general. It is like driving a sports car that hugs the road. This is without a doubt the best money I have spent on any after market product. I would be happy to speak to anyone who is thinking about purchasing this product.

-Donald C. on February 9, 2016
Return Policy

Roadmaster Active Suspension provides a 30 day money back guarantee, from date of purchase. However should the kit be returned, it must be re packed in the original packaging with all components included. The customer will be responsible for the return freight charges.