Part of the popularity of polyurethane is due to it's low cost. When I purchased a set of poly bushings for the rear leafs of my 88 4Runner, I paid $19. When I purchased a set of factory rubber bushings for my rear leafs, I paid $70!! As you can see, there is a significant difference in price. This alone is the reason many people use polyurethane when they go to replace worn bushings.

Some others use it because it deteriorates much slower than rubber. Others use it because it is generally firmer than rubber. Still others because it is available in colors other than black. Some manufacturers use graphite in their black polyurethane, to help keep it from squeaking. This is a very good reason to stick with plain old BLACK when buying poly bushings. 

Energy Suspension is one of the leading poly manufacturers for 4WD applications. They make bump stops, spring bushings, and anti-sway bar bushings for Toyota trucks and 4Runners. 

Anti-Sway bar Bushings

The first application I'm going to discuss is polyurethane anti-sway bar bushings. Anti-sway bars are a great place to use poly since it is firmer than rubber. The less the sway bar is able to compress the material holding it in place at the control arms (or axle on certain vehicles) or where it attaches to the frame, the better it can do it's job. Since the swaybar can compress poly less than rubber, poly is a better choice.

If you are most interested in how your truck performs off the road, then I would advise you not to use polyurethane on your sway bars. Sway bars try to keep your wheels as level as possible, and off-road, this is exactly what you don't want. You want your wheels to extend or compress as freely as possible, not restricted by items like sway bars. Many people, like myself, have removed their sway bars entirely. They are not a necessary part of your suspension, as they are designed only to improve ON-road handling. My 4Runner is a daily driver, and gets at least 200 miles a week on it. The only difference between driving with my swaybar and without is that I have to go a couple miles per hour slower through turns, without my swaybar.

IFS Bump stops

The second application we'll look at is Low-Profile bump stops for IFS (Independent Front Suspension). Energy Suspension makes two bump stops that are great for IFS use. A "low profile," and an "ultra-low" profile bumptop. They are both pictured here. A stock 86-95 Toyota IFS gets approximately 5.75" of wheel travel. Using Low profile stops the wheel travel goes up to 7". Some people have used the Ultra-low profile bump stops to gain even more wheel travel, with the stock suspension components.

I do NOT recommend using Ultra-low stops to replace your compression bump stops, because of the amount of force that those bump stops may see. An Ultra low bump stop may not be adequate to handle the force of the suspension bottoming out. If used as an extension bump stop, they "may" provide the necessary cushioning, and will provide more wheel extension. If you mainly do very slow, rock crawling type four wheeling, these low profile bump stops would be a great way to get more wheel travel. If your style of wheeling is fast, like running sand dunes at Pismo Beach, then you probably want to stick with the stock bump stops.

Leaf Spring Bushings
 

Polyurethane leaf spring bushings are also available. This is one of the more well know applications for poly. On-Road handling can be greatly improved using poly spring bushings. When I switched to poly bushings on my 4Runner, I noticed much less body roll through turns, a firmer ride, and the poly seemed to eat up the smaller bumps in the road much better than rubber ever did.

One of the major complaints about polyurethane is how incredibly squeaky it can be if not lubed properly. It is recommended that you rough up poly spring bushings with coarse sand paper before installation. Most sets of polyurethane also come with a silicone type grease that will not evaporate. By coating the bushings in the grease, and roughing them up beforehand, the poly bushings will not squeak.

If you live in wet areas, or drive through a lot of mud or water, you may end up washing the grease off of your bushings. I once made the mistake (while using a pressure washer to de-mud my truck) of spraying the spring bushings very well. Immediately my bushings began squeaking, and within 6 months I opted to spend the $19 and re-install my spring bushings, rather than listen to them squeak any longer.

Along with the firmer ride, and less body roll, you may also experience a loss in wheel travel. Since the poly is firmer than rubber, your springs will not be able to compress the poly as well, and so they will not be able to twist up as well.

I was very curious to see exactly how much wheel travel would be lost using poly, as compared to factory rubber. One evening I got my 4Runner crossed up, so that the suspension was maxed out. I took careful measurements of wheel travel. The next day I switched my bushings to new factory rubber, and that same night went back to the same spot, got my 4Runner twisted up just the same way, and re-took the measurements. I had gained nearly 1" of wheel travel, just by switching back to rubber bushings.

I admit, 1" is not very much, but for those of you searching for every bit of wheel travel out of your trucks, this is something to consider. 

I also have a very important tip to share with you about installing poly bushings if you choose to do so. The stock rubber spring bushing at the opposite end of the shackle, is a ONE PIECE bushing. It is rubber, MOLDED into a thin metal sleeve, with a thick metal sleeve through the center. There is no way to remove the metal from the rubber....you must remove the entire bushing as one piece. 

The best way I found to do this, is to take your most heavy duty flathead screwdriver, and a heavy hammer, and pound the screwdriver into the spring eye, right where the spring leaf wraps around the bushing and meets up with itself. This will cause the spring eye to open slightly, and you can POUND out the bushing. Don't worry, you won't break the spring....but if you wiggle the screwdriver, you make break the screwdriver.

In early 1998, Energy Suspensions announced a break through in polyurethane. They could now produce poly that will give you all the old benefits of poly, but it is more flexible, so there is no loss in wheel travel. I have yet to talk to anyone using "new" poly urethane on a Toyota. I don't even know if they are making Toyota bushings with this new poly yet, so I can't tell you much about it, other than 'it exists.'  I'm sure we will be learning more about this product as time goes by.