1. Vehicle Suspension
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  4. Rear Axle Suspension Enhancement
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Roadmaster Active Suspension Custom Leaf Spring Enhancement Kit - Heavy Duty

Roadmaster Active Suspension Custom Leaf Spring Enhancement Kit - Heavy Duty

Item # RAS34FR
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RAS Heavy Duty Vehicle Suspension - RAS34FR
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3,000-lb Capacity. Convert your vehicle's leaf springs into a mechanically active suspension system. RAS adjusts to your load to level your ride. The system also increases stability, handling, and control by improving traction and reducing sway. Lowest Prices for the best vehicle suspension from RAS. Roadmaster Active Suspension Custom Leaf Spring Enhancement Kit - Heavy Duty part number RAS34FR can be ordered online at etrailer.com or call 800-298-1624 for expert service.
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RAS Vehicle Suspension - RAS34FR

  • RAS
  • Leaf Springs
  • Rear Axle Suspension Enhancement
  • Heavy Duty

3,000-lb Capacity. Convert your vehicle's leaf springs into a mechanically active suspension system. RAS adjusts to your load to level your ride. The system also increases stability, handling, and control by improving traction and reducing sway.


  • Heavy-duty custom kit converts your vehicle's factory leaf springs into a mechanically active suspension system
    • Actively strengthens leaf springs for improved ride quality with or without a load
  • All-in-one suspension system improves stability, handling, and control
    • Eliminates axle wrap, wheel hop, and bottoming out
    • Reduces dangerous sway and body roll while cornering
    • Keeps your ride level when towing or hauling a heavy load
    • Improves traction while breaking and accelerating
  • Variable-rated coil tension springs automatically adjust to your vehicle's load
    • Activate immediately to support the extra weight
    • Disengage when unloaded, allowing your leaf springs to perform as intended
  • Customizable coil springs can be adjusted during installation to accommodate your towing or hauling needs
    • Independently adjustable for side-to-side leveling of off-center loads
  • Helps extend the life of leaf springs, shock absorbers, shackles, and even tires
  • Durable, epoxy e-coated steel construction
    • Corrosion-resistant brackets on the ends of each unit have a salt spray rating of more than 800 hours
  • Easy, bolt-on installation - no drilling, cutting, or welding required
    • Unit secures under the leaf spring and around the factory U-bolts
    • Fully assembled kit and hardware are included
  • Maintenance-free - adjustments and monitoring aren't needed once installed
  • Made in the USA


  • Weight capacity: 3,000 lbs
    • Roadmaster Active Suspension will not increase your vehicle's weight-carrying capacity
  • 2-Year warranty
  • 30-Day money-back guarantee

All-In-One Suspension System

When towing or hauling a heavy load, you may encounter a number of problems that can make your driving experience difficult or dangerous, such as sway, body roll, or bottoming out. When your vehicle is weighted down, your factory leaf springs can't counteract these problems to the extent that they are supposed to. The weight will overpower the leaf springs and cause them to twist or flatten out. When that happens, they cannot support, level, or stabilize your vehicle effectively. Additionally, because your factory leaf springs are passive, they won't begin to tackle problems such as sway until those problems have already started.

Diagram of RAS Installed

Roadmaster Active Suspension (RAS) kits enhance those passive leaf springs by converting them into a mechanically active, all-in-one suspension system. RAS kits have variable-rated coil tension springs that automatically adjust to your heavy load. Other suspension systems only solve a few problems and usually at the expense of other improvements your factory leaf springs may need. RAS, on the other hand, is a unique kit that provides everything you want in a suspension system without any trade-offs. It eliminates bottoming out like air springs, reduces sway and body roll like sway bars, keeps your ride level like helper springs, and improves traction and braking control like traction bars. This improves your vehicle's stability, handling, and control while you are towing or hauling, as well as when your vehicle is unloaded. RAS also makes your overall driving and towing experience safer and more comfortable, which greatly lessens driver fatigue.

How RAS Works

Close-Up of RAS Tension Spring

Each RAS unit has a powerful variable-rated coil tension spring that converts your passive leaf spring into a mechanically-active system. Once your vehicle is loaded, the tension springs immediately activate to absorb and support the weight. This allows your leaf springs to maintain their bowed position and keeps them from flattening out or flipping over, which greatly hinders their ability to bear a heavy load. The tension springs are variable-rated, which means that the heavier your load is, the more assistance they provide to your leaf springs. Because of this design, RAS reacts instantaneously, whereas hydraulics, air springs, and other suspension systems take time to react. And unlike your factory leaf springs, RAS stops sway and sag before they even start to happen. Additionally, when your vehicle is unloaded, the tension springs disengage, allowing your leaf springs to perform as intended without hardening your ride. RAS won't hinder your leaf springs' movement, nor will it cause any friction between any of the brackets.

Eliminates Axle Wrap and Wheel Hop

RAS Eliminates Axle Wrap

When under a heavy load, leaf springs are especially susceptible to axle wrap, which can cause wheel hop. Wheel hop is when the tires lose their grip on the road, causing a jarring, up-and-down movement. Axle wrap occurs when the circular motion of the tires cause the leaf springs to twist or rotate. If the leaf springs twist far enough, wheel hop can occur. RAS stabilizes your leaf springs by absorbing the force of the load they're trying to support. This eliminates axle wrap and wheel hop, as well as prevents your vehicle from bottoming out. Because of this, less strain is put on your vehicle. And by reducing some of this wear and tear, RAS helps extend the life of your leaf springs, shock absorbers, shackles, and even tires.

Reduces Sway and Body Roll

RAS eliminates sway and body roll

When driving along a curve while towing or hauling a heavy load, the back end of your vehicle or trailer can start to shift with that weight. If your factory leaf springs have flattened or twisted under this load, they won't be able to prevent it from shifting. Because of this, your trailer will sway away from your vehicle. This makes driving challenging and dangerous, as it increases the risk of body roll, which is when your vehicle drastically leans to one side. This can often cause you to completely lose control of your vehicle. Body roll is especially prevalent with multi-passenger vans and vehicles towing long campers, trailers, or boats. RAS provides a much safer ride by reinforcing your factory leaf springs and stabilizing your load. This helps prevent sway from occurring and reduces the chance of body roll while cornering, turning, and swerving. RAS also lessens the rocking motion that happens during windy conditions or when a semi passes by on the road.

Levels Your Ride and Improves Traction

RAS Levels Your Ride

When your vehicle is overloaded, the bulk of the weight transfers to the rear axle. Your factory leaf springs then become overwhelmed by this weight, as they are not strong enough to support it. This causes the back end of your vehicle to sag and the front end to rise, which means that the front tires have lost some of the grip they need with the road. In addition to loss of traction, it can also cause poor headlight aim, unintentional swerving, and an extremely bumpy and uncomfortable ride. RAS bolsters your factory leaf springs and enables them to provide support for your load without compromising ride quality or comfort. This keeps your ride level from front to back whether you are hauling a load in the bed or towing a boat, trailer, or camper. RAS also ensures that your tires have the traction they require while braking and accelerating, which improves the overall driving experience.

Customizable Coil Tension Springs

Adjusting Spring With Spacer

RAS is also customizable. During installation, the coil tension springs can be adjusted to 2 different tension settings or anywhere in between for improved road handling and support. To do this, rotate the springs while keeping the threaded rod still. As you turn the spring, use one of the 2 included spacers as a gauge to measure the widening gaps between the coils. In order for the RAS units to work as intended, you must tension the coils to a minimum of 25 percent with the 1mm white spacer and no more than 40 percent with the 2mm spacer. The springs can also be independently adjusted to compensate for off-center loads such as a handicap lift.

Easy, Bolt-On Installation

RAS Once Installed

This custom-fit kit comes fully assembled and is easy to install. Each RAS unit simply bolts onto your factory leaf spring with the included hardware, and drilling, welding, and cutting aren't required. First, position the eye hook bracket so that it wraps around the top of the factory leaf spring eye. Then the axle bracket secures under the leaf spring and around the factory U-bolts on the other side of the leaf spring pack. Once the maintenance-free RAS units are fully installed, you won't need to monitor them as you would with air springs.

Corrosion-Resistant Steel Construction

RAS Construction Close-Up

RAS is extremely durable and corrosion-resistant. The units are constructed of high-grade alloy steel, and they have an epoxy e-coat on the coil springs to provide extreme corrosion resistance. The brackets on the ends of each unit resist the effects of water and other elements, and they have a salt spray rating of more than 800 hours.

4611-TDHD RAS Custom HD Active Suspension System for OEM Leaf Springs - Rear Axle

Installation Details RAS34FR Installation instructions

This Product Fits The Following Vehicles

Customer Reviews

Roadmaster Active Suspension Custom Leaf Spring Enhancement Kit - Heavy Duty - RAS34FR

Average Customer Rating:  4.8 out of 5 stars   (12 Customer Reviews)

3,000-lb Capacity. Convert your vehicle's leaf springs into a mechanically active suspension system. RAS adjusts to your load to level your ride. The system also increases stability, handling, and control by improving traction and reducing sway.

2021 Toyota Tundra

Was very easy to install on my 2021 Toyota Tundra , I cant wait to see how it does when I haul a Heavy load. Lifted the rear up an inch. Drives even smoother than it already did.


I just finished installing this kit and the installation was very simple and smooth. I did take it for a no-load test run, and could tell the change. Can't wait to see how it does with a load, (my Quad).

2019 Toyota Tundra

Added a Roadmaster Active Suspension Kit to my 2019 Tundra to reduce squat when towing my Travel Trailer with the fresh water tank full. The extra 400 lbs of water adds a lot of tongue weight. My experience with e-trailer is that they always ship “freaky fast”. As usual, my order was at my door in just a few days. The Roadmaster Active Suspension kit was nicely packaged with very good instructions. All components were well designed and manufactured. Installation went smoothly.

2008 Toyota Tundra

We have a 2008 Toyota Tundra. This really helped a lot with stability and sway (don't have a sway bar). We have a Trailer with a 700 pound tongue weight, and this product combined with our WDH lelveled everything out. When unloaded it did raise the rear of the truck about 2 inches, I will be adding a leveling kit to the front end.

2013 Toyota Tundra

Wow....What a difference! First off, the etrailer crew was fantastic and my order arrived a couple days early. The wife and I were scheduled to go camping the week following Thanksgiving and I wanted to install the RAS before we left so I could see if it lived up to the hype. It arrived the day before Thanksgiving while I was at work which gave me 2 days to attempt to install these on my 2013 Toyota Tundra. It took approximately 90 minutes to install......And I'm very meticulous about these things!! I had a little hiccup trying to extend the threaded rod, but etrailer support set me straight - On Thanksgiving!!! I took the beast out for a test drive and was amazed at the difference in the ride. I set them at 45% or the 2mm disk spacing and my truck rode like it was on rails. No more sway or body roll, even my wife noticed the difference! She said "I don't have to grab the Oh Sh!t handles anymore!" 2 days later we loaded up our travel trailer, a 30' trailer that weights about 8,000 lbs, and took off. The ride was sooooo much better. Very little sway from passing trucks, it was less bouncy, and we handled the corners much better. I highly recommend this product!


Installed RAS34FR on 2016 Tundra 2WD used to tow an RV Trailer with an 800 lb tongue weight (truck rated for 1000 lb). The Blue Ox hitch system we use sets ball behind rear bumper about 14" putting significant leverage disadvantage on truck, and even with weight distribution set up pretty high, truck rear squats way too much. I really like the RAS system for many reasons including: relatively easy installation, less hassle once installed compared to air bags, minimal impact on truck ride loaded and/or unloaded, expect system to be durable over the long haul, no need to fuss with pressure adjustments of air bags, and ability to easily "self tune" amount of added support in unlikely event you may choose to alter it. I will continue using system in towing our 4 ton RV trailer as well as doing typical home owner hauling. The RAS system ( the 3000 lb capacity option) set up for 40% assist has made a world of difference towing the RV. Truck now sets level even without heavy torque set on bars of Blue Ox hitch. Handling is back to normal; no sway, front of truck elevation neutral VS pitched upward, ride is good. Please note that at the initial set up listed above, truck does set up about 1-1/2" higher when empty and ride is just a bit more stiff compared to stock (no RAS) ride. I may choose to back down on 40% assist level a bit in future to resolve these issues which are minor in my judgement. etrailer service from Christina J was excellent. Shipping was trouble free and prompt. Communications were timely and to the point. Although the RAS price is high, overall I feel that I got what I paid for - a product that delivers the performance it brags about. eTrailer listing was accurate and helpful. It appears the RAS product reviews are legitimate VS the obvious fake ones you get on some other popular sites. I recommend the RAS product and feel potential buyers can trust it will deliver within it's specifications for you.


It’s the second set I’ve owned with my first being on a Tacoma. Followed directions when installing and it went smoothly.

2019 Toyota Tundra

Easy install quality parts. Fast delivery. Test drove nice can't wait to hook up to some weight.

2017 Toyota Tundra

Super fast shipping and excellent customer support. Would highly recommend doing buisness with etrailer.



2016 Toyota Tundra


Ask the Experts about this RAS Vehicle Suspension

  • Heavy Duty Roadmaster Active Suspension That Fits 2017 Toyota Tundra 4x4
    Happy to help, and I was able to confirm with the manufacturer the correct Heavy Duty Roadmaster Active Suspension kit that is a fit for your 2017 Toyota Tundra 4WD, which is the following part: - Roadmaster Active Suspension Custom Leaf Spring Enhancement Kit - Heavy Duty # RAS34FR The RAS is a really good choice for suspension enhancement for your Tundra, as it will keep your truck level, help with any body roll you might experience, while also giving your truck better traction...
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  • Will the Roadmaster Active Suspension System Lift the Bed of an Already Lifted Truck
    The Roadmaster Active Suspension system # RAS34FR effects the suspension, so it will work with any body lift that you may have in place. The RAS system will lift the rear of the vehicle approximately 1" to 1-3/4" depending on the truck, so the bed is also going to raise up in the process that same amount- so it's going to be in addition to whatever body lift has already been added.
    view full answer...
  • Do I Have To Remove The Leaf Spring Eye Bolt To Install?
    That's a good question. I have seen videos of this product installed and many times the (part C) eye bracket hook just lays onto the leaf spring eye. However, since 2008 the Tundra's have required one side of the eye hook to be removed. I have attached the install procedure PDF file. Step 6 reads, "Remove one side and place it on top of the rear leaf spring eye bracket hook." They certainly could have provided a picture illustrating this and a better explanation. So yes, you do have...
    view full answer...
  • 2008 Toyota Tundra TRD 4x4 Dbl Cab Suspension Enhancement for Carry Camper in Bed
    For your 2008 Toyota Tundra that you will be carrying a camper in the bed of the best suspension enhancement by far is the Roadmaster Active System part # RAS34FR. This kit allows you to have adjustable suspension support that offers the best stability from side to side for campers and unlike other options it doesn't hurt the ride quality. Many report the ride quality actually improves.
    view full answer...
  • Will the Roadmaster Active Suspension for a 2016 Toyota Tundra Work With TRD Anti-Sway Bar
    The Roadmaster Active Suspension (RAS) Custom Leaf Spring Enhancement Kit part # RAS34FR is an excellent option for a 2016 Toyota Tundra. In regards to compatibility, there should not be any with upgraded anti-sway bars from what I can see. The RAS kit mounts above the leaf spring pack so you will be fine.
    view full answer...
  • Best Suspension Enhancement for 2021 Tundra SR5 4x4 Towing Trailer
    The best suspension enhancement for your 2021 Toyota Tundra is by far the Roadmaster Active Suspension kit part # RAS34FR as it gives you the support you are wanting to prevent sag, doesn't hurt loaded or unloaded ride quality, and also improves handling and side to side stability.
    view full answer...
  • Can RAS34FR Roadmaster Active Suspension System Be Used Along With Weight Distribution
    The US- made # RAS34FR Roadmaster Active Suspension kit is a fit for your 2006 Toyota Tundra and would be an excellent addition to augment your rear suspension and to improve your ride quality whether the truck is loaded or unloaded, towing or not. The system will work along with your Equal-i-zer weight distribution system to level out your ride height between the front and rear axles and will also help prevent axle wrap and wheel hop. You'll want to be sure to repeat the set-up procedure...
    view full answer...
  • Can I Use the Roadmaster RAS on my 2009 Toyota Tundra with a 4 Lift
    From a fitment standpoint, RAS # RAS34FR generally fits lifted trucks like your 2009 Toyota Tundra without an issue as long as this is a block style lift. 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; if you've got a full on suspension lift with elongated springs or other adjustments to the suspension the RAS will not work for you. If you've got a suspension lift, I recommend...
    view full answer...
  • Best Suspension Enhancement for 2019 Toyota Tundra for Support and Ride Quality
    If you wanted the best suspension support for your 2019 Toyota Tundra and the best ride quality what you want is the RAS system part # RAS34FR. This will give you adjustable suspension support like you are wanting but unlike other similar options this will improve ride quality loaded and unloaded.
    view full answer...
  • Best Suspension Enhancement for 2016 Toyota Tundra Towing Trailer with Bounce
    To prevent the bouncing you are experiencing and give you the best support and ride quality you'd want the Roadmaster Active Suspension kit part # RAS34FR. Unlike other similar options this would give you the best overall ride quality while giving you the support you need to prevent the bouncing.
    view full answer...
  • Can RAS Leaf Spring Enhancement Kit Fit With Air Helper Springs On 2017 Toyota Tundra?
    While this has not been tested, since the air helper springs for your 2017 Toyota Tundra like the Air Lift LoadLifter 5000 Ultimate Air Helper Springs with Internal Jounce Bumpers - Rear Axle # AL88299 mount on the leaf spring pack and add a bracket to the top of the leaf spring, it is unlikely that the Roadmaster Active Suspension Custom Leaf Spring Enhancement Kit - Heavy Duty # RAS34FR you were looking at will fit. With that said if your Tundra has lower overload springs you can add...
    view full answer...
  • Suspension Enhancement Recommendation for 2008 Toyota Tundra with Gooseneck Hitch
    For your 2008 Toyota Tundra the suspension enhancement I would recommend the highest is the Roadmaster Active Suspension kit part # RAS34FR as it gives you adjustable support like you are wanting but it also gives you a better ride quality and handling unlike the other options so it's the best overall solution.
    view full answer...
  • Rear Suspension Enhancement Recommendation for 2020 Toyota Tundra
    We do have the Timbren kit part # TTORTUN4 that is a fit for your 2020 Toyota Tundra which will give you an additional 6,000 lbs of suspension support. We don't have any kits that would provide more support but if we did it would probably cause your ride quality to be harsher than you'd like. For the ultimate in rear suspension support the RAS system part # RAS34FR is the way to go. This gives you the support you are wanting and actually improves the ride quality loaded and unloaded...
    view full answer...
  • Is SumoSprings or Roadmaster Active Suspension Better For 2008 Toyota Tundra
    For your 2008 Toyota Tundra, between the SumoSprings Solo Custom Helper Springs # SSR-610-54 and the Roadmaster Active Suspension (RAS) Custom Leaf Spring Enhancement Kit # RAS4611TD, the better overall system is the RAS # RAS4611TD. The reason for that is the RAS is an active system which continually reinforces your Tundra's original leaf spring suspension. The force normally put on its leaf springs, either when carrying cargo or towing a trailer like you are, gets transferred to the...
    view full answer...
  • Suspension Enhancement for 2020 Toyota Tundra to Help with Ride Quality and Stability
    For your 2020 Toyota Tundra the suspension enhancement kit we offer that would give you the best sag reduction, stability, and handling would definitely be the Roadmaster Active Suspension kit part # RAS34FR over everything else. Other options can help with some of those things but you usually have to sacrifice ride quality unlike the RAS setups.
    view full answer...
  • Suspension Enhancement Recommendation for 2003 Toyota Tundra with B and W Turnoverball
    I have a really great suspension enhancement kit that fits your 2003 Toyota Tundra with the B and W Turnoverball hitch # BWGNRK1251 you have but none of the air bag style kits we offer will fit with an in-bed hitch. Instead the best option by far is the Roadmaster Active Suspension kit part # RAS34FR which gives you the support you are wanting when towing but also improves ride quality when you aren't towing as well so it's by far the best option.
    view full answer...
  • Recommended RAS Leaf Spring Enhancement For 2018 Toyota Tundra Towing Small 5th Wheel Trailer
    For your 2018 Toyota Tundra towing a small 5th wheel trailer with 1200lbs of pin weight I recommend the Roadmaster Active Suspension Custom Leaf Spring Enhancement Kit # RAS4611TD as it has a 2000lb load rating which is plenty for the weight of your trailer, and will do a great job of preventing sag and eliminating sway and body roll when your truck is loaded or unloaded. There is nothing wrong with going with the heavy duty # RAS34FR that has a 3000lb load rating, but you do not need...
    view full answer...

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