4Runner Bump Stops: The Complete Guide

Bump Stops For the 5th Generation Toyota 4Runner: The Complete Buyers Guide

Have you ever been driving along on a trail, when all of the sudden you hit a rut that turns out to be a little deeper than expected? Then you cringe as you hear the rear axle slam up against the vehicle and you swear something has to be broken. Maybe you do a lot of hauling with your 4Runner and you bottom out from potholes on the road due to all the extra weight of a trailer.

Well, that contact you feel is your rear axle bottoming out and hitting the rear bump stops.

The sole purpose of stock bump stops is to prevent metal-on-metal contact when bottoming out. They don’t provide any dampening or cushioning of the suspension, they are only a fail-safe in case you bottom out. In order to prevent harsh contact with the stock bumps, you will need to upgrade to aftermarket bump stops. Otherwise, those hard-hitting bumps could end up causing some serious damage to your vehicle.

In this article, we’ll be covering the different types of bump stops, the materials used, the different applications for aftermarket bump stops, and some of the best brands to look at when upgrading.

Types

There are three basic types of bump stops that are prevalent on the market for off-roaders.

1. Rubber
2. Micro-cellular urethane
3. Hydraulic

The first two listed are the most common and the most practical for the majority of the community. For those that take their off-roading to the next level, such as a pre-runner or high-speed offroad style build, the hydraulic bump stop is probably going to be the way to go.

1. Rubber

There are two different types of rubber bump stops that are popular on the market right now.

One is a completely natural rubber product and the other is called dual-durometer rubber. The natural rubber bump stop is natural rubber from top to bottom with a hollow core. The dual durometer rubber, which means it is made from two rubbers extruded together to form one piece, looks almost like a larger/taller stock bump stop. Both types of rubber bump stops are maintenance-free, allowing you to install them and forget about them. Although they are different designs and slightly different makeup, they both provide the same benefits and functions.

Both styles of rubber bump stop work to absorb the energy from the vehicle pressing down onto the rear axle or vice versa. The further the bump stop is compressed, the more resistance it gives which in turn will help to push the frame and axle-back apart. The rubber material allows for a cushioning effect instead of a hard stop like the stock bump stops that are typically made from polyurethane. All of this will result in a smoother ride and no more harsh bottoming out.

Rubber bump stops are much taller than stock bump stops. They in turn will act as a helper spring when towing, providing supplemental resistance to the rear springs. This results in a safer and less bouncy towing experience.

Pros:

• Maintenance-free
• Part for part replacement
• Easy installation
• Provides better stability on and off-road
• Improves towing experience

Cons:

• Non-customizable
• Not designed for high-speed use

2. Micro-Cellular Urethane

The next variation of bump stop is made from micro-cellular urethane.

This material is essentially a really firm foam and has very similar properties to the rubber bump stops. As the bump stop is formed, there are millions of tiny air pockets created within the material. All of those air bubbles allow for the compression of the foam. This is how they can make a variety of different densities and strengths to these bump stops. The more air inside, the less resistance; less air equals more resistance. This type of bump stop is also maintenance-free, which is an added bonus. It is always nice to have one less thing to worry about.

Just like the rubber bump stops, these urethane bump stops will absorb the energy created by a bump in the road and spring itself back into place.  It also provides a progressive spring rate as the natural rubber. The more the material is compressed, the stronger the resistance and spring effect will be.

Urethane bump stops are also much taller than stock bump stops. They are also typically taller than the rubber bump stops. This again allows it to act as an additional spring in the rear to help hold up the vehicle under the weight of a trailer or any load in general such as a heavy build with aftermarket armor, lots of gear, or both.

Pros:

• Maintenance-free
• Part for part replacement
• Easy installation
• Provides better stability on and off-road
• Improves towing experience
• Different resistance options available

Cons:

• Not designed for high-speed use

3. Hydraulic

Hydraulic bump stops are the crème de la crème when it comes to off-road bump stops.

They are designed like the shock struts you already have in your suspension, just shorter in height and with a much wider inner shaft. They are usually filled with lightweight shock oil and nitrogen and will function similarly to how standard shocks work. Hydraulic bump stops can vary in length and diameter and the nitrogen inside can be fine-tuned to provide different valving (or resistance).

Like the other two types mentioned before, hydraulic bump stops will cushion the rear axle as it rises, but it does so in a couple of stages. The initial resistance comes from the compression of the nitrogen. This will be somewhat light at first compared to a stiffer response in the mid-range of compression. The final third of the shaft stroke will be where the piston is forced through the shock oil. The bulk of the energy absorbed will occur in this end range.

Hydraulic bump stops are primarily designed for those that enjoy higher speed off-roading, such as desert riding and racing. Therefore, the design is better suited for those environments and not so much for towing, although there will be benefits provided over the stock bump stops. Two downsides to hydraulic bump stop compared to rubber and urethane are that they are much more expensive and they will require maintenance to ensure they are functioning at their peak level. Another thing to note, improper installation of this kind of bump stop could cause the rest of your suspension to ride worse, or even cause damage to it or your vehicle.

Pros:

• Provides greater stability off-road
• Great for high-speed off-roading
• Customizable to your needs
• Different resistance options available

Cons:

• More expensive
• Typically requires professional installation
• Requires maintenance

All three types of bump stops will make a huge improvement in how your vehicle rides off-road. The rubber and urethane bump stops will both double as helper springs to help smooth out the ride while towing. While the hydraulic bump stops will provide some benefit with towing, they are more suited for the more experienced and extreme off-roader. Rubber and urethane bump stops will be the perfect fit for the majority of those that take their vehicles off-road. But if your rig fits in the category that would utilize hydraulic bump stops, they will be worth every penny.

Functions

As mentioned earlier, there are two main reasons to upgrade from your stock bump stops to aftermarket ones: towing and off-roading. Below I’ll break both of them down to explain why and how these will change the game for you.

Towing

You don’t have to be an avid off-roader or rock crawler to see some huge benefits from aftermarket bump stops.

If you frequently tow with your 4Runner, beefing up the bump stops could help drastically reduce the sag in the back end and provide a much smoother ride. As you load down your trailer, you will of course notice that the rear of your vehicle gets lower and lower. Then as you drive over bumps or dips in the road, all of that extra weight pivoting at the hitch will bounce you up and down like a see-saw. Swapping out your wimpy stock bump stops with some aftermarket rubber or micro-cellular urethane ones will give your vehicle some extra resistance to fight off the bro lean. Plus, since the bump stops will likely be under pressure at all times when the trailer is attached, the added resistance in your suspension will minimize the see-sawing effect and result in a much smoother and more comfortable ride for you.

I was able to measure the difference in ride height between stock and the SuperSprings with a lightly loaded trailer (roughly 1,000-1,200 lbs between trailer and contents). All loaded down, the SuperSprings kept the rear of my 4Runner sitting ½” higher over the stock bump stops. It’s not a drastic difference, but it’s significant enough to show that aftermarket bump stops will improve your towing experience.  One major thing to be aware of though, is that despite aftermarket bump stops providing more stability and a somewhat ‘stiffer’ rear suspension, it does not increase the towing capacity of your vehicle. Always make sure to adhere to the GVWR from the manufacturer.

You’ll get the most bang for your buck with rubber or micro-cellular urethane bump stops when it comes to towing assistance. The hydraulic style bump stops will also help with providing a more comfortable ride while towing, but obviously at a much higher cost. A pair of rubber or urethane bump stops will only run you a couple of hundred dollars and about 30 minutes to install them. There are much more sophisticated systems to help with towing needs such as air ride suspensions. However, those are more expensive, more complex to work with, and can sometimes fail which will put you in a bind out on the road.

Off-Roading

We all know that going off-road is going to put a lot of strain and stress on our suspension systems.

That’s why a lot of us make the investment early on to upgrade shocks and coils in order to provide extra lift, more travel up and down, and a better-tuned system for life on the trails. All of these things will help provide a firmer, more controlled ride, and hopefully help keep your wheels on the ground in order to give you more power and traction as you traverse the uneven terrain. When making this investment, you’ll want to make sure you include a set of bump stops on your shopping list.

When going off-roading, your suspension system is going to be doing the brunt of the work to keep your vehicle as stable as possible and absorb the jolts from bumps and drops in the terrain. Your struts/shocks and springs allow for the up and down travel in your suspension as well as providing some resistance as they reach the end range of their compression. That resistance will help to press your wheels back onto the ground and hopefully keep your tires gripping the ground instead of spinning, sliding, or even in the air.

When you add in some of the bump stops styles mentioned above, your suspension’s ability to push your wheels back to the ground will improve. It will help to control and smooth out the up/down travel in your ride and make what is always a bumpy and jarring ride a little more enjoyable.

Another benefit to aftermarket bump stops is that they will help to reduce some of the strain on your suspension as it’s an extra piece to absorb the weight of your vehicle.

Brands

Three of the bigger names in aftermarket bump stops are DuroBumps, Timbren, and SuperSprings.

These brands utilize either rubber or urethane to create their products. I won’t be covering a specific brand for hydraulic bump stops, as that is more of a niche market. We will save that post for another day.

Most of the popular suspension companies, such as King, Fox, ADS, Icon, Bilstein, and others, will have some options for hydraulic bump stops. All three of the brands covered below provide a very similar function even though they are made from different materials.

They all have three things in common…

1. First, they are progressive bump stops, meaning that as the material is compressed, the resistance against the axle is increased.
2. Second is they are all maintenance-free, so after a simple install, you can just let them get to work without worrying about whether they need to be cleaned, lubricated, or rebuilt.
3. Finally, they are all reasonably priced. A pair of bump stops from the three brands below will run between $150-$260.

If you are looking for some hydraulic bump stops, you should plan to pay that price per bump stop. Below I will go into more detail about the brands and the specific product that they offer.

DuroBumps

Shop DuroBumps:

• Front: Check Price
• Rear
  • No Lift Required: Check Price
  • 2″ Lift: Check Price
  • 3″ Lift: Check Price

DuroBumps is a USA company based out of Arizona. The founder, Curtis Glenn, was dissatisfied with the options available to him for bump stops on his 3rd Gen 4Runner so he took his experience in the rubber and plastics industry and turned it towards creating his own bump stop. When he finalized his prototype, he advertised them on a forum and things took off from there. They now offer bump stops for 4Runners, FJ Cruisers, Tacomas, Tundras, and some Lexus models.

The DuroBump bump stop is made from dual durometer rubber that provides progressive damping upon impact. DuroBumps are the most similar in appearance to the stock bump stops in my opinion because they appear to be a harder, more solid rubber. That’s because the rubber is actually two types of rubber combined into one piece. The design places a firmer rubber at the base of the bump stop and part of the main body, and a softer rubber on the end, so that they both work together to provide the damping effect.

Timbren

• Timbren Bump Stops: Check Price

Timbren Industries is a well-known brand based in Canada that specializes in off-road bump stops and trailer suspension systems. While they get plenty of customers purchasing their off-road bump stops, they have a wide range of trailer suspensions as well as their signature SES, or Suspension Enhancement Systems. These SES bump stops are very similar to their off-road bump stops, but are offered for a wide range of vehicles and are only intended to enhance the suspension systems for daily driving and towing.

The Timbren Active Off-Road bump stop is made entirely of natural rubber with the exception of the mounting plate. They are designed with a hollow core to allow more give when absorbing the energy from those harsh bumps. A big perk of this brand is that they come with a lifetime warranty and satisfaction guarantee. That’s right, a LIFETIME warranty. You don’t see too many of those on parts that work this hard.

SuperSprings International

Find them online: 

• SumoSprings Bump Stops: Check Price

While they’ve ventured into the off-road market and are really gaining traction, they have a large variety of products aimed at work vans, RVs, trailer applications, and more. They also offer a product called coil SumoSprings that are designed to give a boost to coil capacity by 15-30%. If you have not seen their coil SumoSprings, check them out here.

All of SuperSpring’s products are made of micro-cellular urethane. They can vary in density to provide different levels of resistance.

The 4Runner applications are part of their product line called SumoSprings, and they are offered in two different variations for us. One is for lighter loads, rated at 1,400 lbs at 50% compression (blue) of the bump stop, and another for heavier loads, rated at 1,800 lbs at 50% compression (black). I have the lighter version installed on my 4Runner because I don’t have additional weight from bumpers or any built-in storage, and I don’t do any heavy towing. If you are towing frequently, the SumoSprings 1800lb black version is what you want to consider. If your 4Runner is a daily driver, and you occasionally go off-road, then the 1400lb blue version is for you. By installing either the black or blue SumoSprings, you will see a reduction in body roll which is a huge plus for most owners. Before SumpSprings, you would need to install a full airbag system to see a similar performance enhancement.

SuperSprings also provides a limited lifetime warranty. So if their product fails from typical use, they’ve got you covered!

SumoSprings are gaining popularity quickly because of their versatility. They are great for daily driven 4Runners along with off-road applications as well. Read this recent review on SumoSprings.

Final Thoughts

Whether you spend time on the trails, are frequently towing with your 4Runner, or just use it as a daily driver, your ride will greatly benefit from replacing the stock bump stops with one of the bump stops covered in this article. Even a daily driver is going to encounter potholes, manhole covers, or road work that will jolt the whole vehicle. They all will greatly improve the ride quality and stability without breaking the bank.

One of the great things about the brands highlighted is that all of their products are super simple to install for any skill level.

In less than an hour you can feel more comfortable and secure while towing, and more smooth and stable on or off the road. Remember, the stock bump stop is your vehicle’s last defense to prevent two heavy metal objects from crashing together. New bump stops won’t make you feel like you’re driving on a cloud. But I can tell you that after driving with my SuperSprings installed, the ride is much smoother and I no longer experience the harsh jolts in my suspension.

At the end of the day, this is an affordable, maintenance-free upgrade that will greatly improve the ride quality and help extend the life of your suspension.