A comment about bushings


#1

I’ve mentioned recently that I just replaced my front struts along with all the rubber parts. Had someone else do the hard work.
I just wanted to comment for the edification of those who’ve never replaced a long-existing set of struts how much road noise was reduced. I never cease to be surprised at how quiet the car comes out when I do this. It’s like brand new again.

For the record, the rubber bushings on which sit the upper and lower ends of the springs, and the rubber bushing contained within the upper strut mounts, dampen a lot of road noise. They absorb and covert to heat energy the vibrations. However rubber compressed for years under perhaps 700 pounds per spring, over a very small contact area at the end of the coils, compresses, thins (due to a process called “cold flow”), and loses its ability to convert the vibrations (the rubber hardens). These are “critical paths” through which road noise either gets damped out or gets transferred to the body structure.

I’ll bet that those of you who are working mechanics always get a frown and a look of suspicion when you suggest replacing upper mounts and bushings. Nobody perhaps believes you. The guy that did mine had it super-easy… I brought all the parts in a box and instructed him to replace them all. I included the exploded view drawing and Toyota part numbers along with the shipping papers so he could see that the parts were correct and OEM. I specified that I wanted the new upper and lower spring bushings and the upper mounts as well as the bumper stops replaced along with the struts. I’m sure most of you guys aren’t that lucky.

I’m hoping that someone out there will think of this post when he/she has his/her struts done, remember it, and the job of convincing will be easier for you pros. If I convince just one person, I’ll feel I’ve contributed.

I love the new quietude. I miss my old body. It broke my heart to have to have someone else bolt everything in.


#2

Well? Bushings are basically isolators.

Go figure?

Tester


#3

I think it is the bad conditions in the roads for me, sure only 157k miles but the ride seems rougher hitting potholes and pavement cracks than it used to be, how to determine when replacement parts are needed in your experience would be appreciated @the_same_mountainbike


#4

TSM … good post, just curious, did you find it difficult to locate sources for all the OEM bushings?


#5

True, tester, but how often do we actually think about them?

Barky, my preference is to do all the rubber parts on any car in good shape every time the struts get changed. Rubber breaks down. Loaded constantly by the weight of the car, it flattens and hardens. And there’s no doubt that potholes and other impact shocks exacerbate the problem. One has to remove the springs, bushings, and upper mounts to change the struts anyway, so why not change the rubbers? People assume that old cars just get noisier and there’s nothing one can do about it. While there are many things that do deteriorate that really aren’t practical to change, when one has to pull parts apart anyway, why not?

But realize when reading this that you’re reading writings from a guy that gutted a perfectly good car from the B-pillars back to add more soundproofing. I hate road noise.


#6

I didn’t, George. There’s a site called “overstocktoyotaparts” that sells them wholesale. The struts are KYB, but my research shows KYB to be a Toyota OEM supplier.


#7

No, we’re not as lucky as the mechanic you used. In fact, most people who consider themselves in the know aren’t as smart either. But then you seem to take an active interest in your car and enjoy keeping it in fine condition.

Even on this forum I laugh when a poster asks a question about the necessity of replacing struts that have, say, 150000 miles on them. The number of people who respond “If they’re not leaking they’re fine” or “bounce the car a few times and see if it stops” is an indication that very few people know or care about struts and bushings. Anyone who thinks that struts/mounts/bushings are fine after 150,000 miles just looks at a car as a conveyance from A to B and doesn’t really pay attention to handling and noise.

I’ll bet if you drove your car on a skidpad or slalom course before and after you’d also note that your car stopped, turned, and handled better with the new struts.


#8

Even without a skidpad I can feel the difference. It still had some damping ability, but it was definitely due. Overdue, actually. I did my rears a few years ago. I should pull out the paperwork… it might have been longer ago than I realize.

I agree 100% with your comments about the responses. I keep my mouth shut, because many people are just quoting things they’ve heard. As a matter of fact I’ll bet that if most people were told by a shop that they should consider getting new struts the first words they’d say would be “are they leaking?”. And I suppose that’s fine if all they want to do is get from A to B.

I do take an active interest in my car. But I also rarely take things at face value, I like to understand the “why” of things. I love physics, because EVERYTHIING is physics. And it’ll do what it’ll do, no matter how we define its “laws”. We know so very, very little. There’s Soooo much left to explain.

Next Step: new tires. My wear bars are getting obvious.


#9

“Next Step: new tires. My wear bars are getting obvious.”

I don’t know where you live but if it’s going to be dry all summer wait until fall. Those “racing slicks” can be fun. :slight_smile:


#10

speaking ofphysics, have you read about the hexagonal hole in the atmosphere, or cloud cover?, at saturns pole. I thought it was a hoax until I investigated further. amazing. just more proof of how little I/we know. as I age my mind becomes more open and I am less “certain” about things. for a while the opposite was true. glad I saw the light.


#11

With all due respect @asemaster, I’m one of those “If they’re not leaking they’re fine” guys. The reason I say this is a 20+ year career engineering struts and shocks, some with wires coming out and computers attached. The primary wear item is the seal that keeps the oil in. The second wear item is the piston band that acts as a bearing and somewhat as a seal bathed in nice lubricating shock oil. The third is the bearing below the seal, also bathed in oil. The damping control parts are springs designed to have infinite life (18 million cycles plus) and orifices (holes) that don’t wear. Most all dampers are similar inside.

I’ve tested dampers to beyond a simulated 150,000 mile durability and tested dampers with 100,000+ real world miles (and 10 years time) on them that still met manufacturer’s specs for loads. I don’t agree with a bounce test, it won’t work with modern cars. I stand by the “not leaking, don’t replace” with a caveat, over 100-150K, change 'em, you’ll like the results. I do this on my own cars. The “not leaking” is to prevent the big-box mechanic from claiming the shocks are “worn out” at 50,000 miles.

That said, I am in complete agreement with you on replacing dampers and rubber parts as well as the dampers at high miles. The the rubber parts fail exactly as @the same mountainbike accurately described. The suspension is a system performs best when all is as designed. Replacement dampers are nearly always 10-20% stiffer than the OE parts and help the other things that loosen up with time. People also want to “feel” the difference new parts make. The rubber bits are definitely as important the dampers to provide the feel and the noise reduction most want.

This train of posts should somehow be automatically linked to anyone posting a suspension question. A lot of questions we see posted here got answered in this series of responses.


#12

I wonder if it’s feasible to install thicker than stock spring bushings to reduce road noise.
Would help a lot of econoboxes.


#13

Yes, especially the uppers help but it tends to increase the ride height. Adding additional rubber to the top mount is pretty much impossible since the spot is usually pretty full to begin. Pulling the carpets and installing sound insulation (Dynamat and others) might be just as effective but it does add a little weight. A quiet bump “feels” better than a harsh AND noisey bump.


#14

Circuit, I wondered about that too. But, having personally fallen victim in the past to the “law of unintended consequences”, I’d be inclined not to try it. I wonder, however, if bushings and strut mounts with an upgraded ability to absorb noise would be a viable market for aftermarket manufacturers.

The big surprise I discovered when I completed the Dynamat project was the amount of noise from outside the car that it attenuated. Wind noise, noise from passing other cars traveling in the opposite direction, that type of stuff. Apparently more of that goes through body panels than I ever realized. Suddenly I could roll the windows up and the car was almost totally isolated from the outside world.

I should add to this explanation my point that Dynamat attenuates the noise that originates from a different SOURCE. Yes, it lowers the resonant frequencies of the body panels by changing the mass, and yes it absorbs vibrational energy and dissipates it as heat energy, but it’s noticeable more in the effect that has on transference of outside noise than road noise. The spring and strut bushings are noticeable in their reduction of road noise.


#15

@Mustangman‌

Can you explain what happens when a strut/shock does leak? And I don’t mean when it leaks its oil. But instead when it loses its gas charge

How does this effect the performance?

Tester


#16

I agree with asemaster’s comments 100%. With all due respect to Mustangman, a mechanic in the field sees total and partial failures of shocks and struts all of the time with no oil leakage and on cars with less than 100k miles.

The examples I could provide about failure with no oil leakage, passing the pogo test, and so on are countless.


#17

@Mustangman‌ , and I agree with you. I’m not saying that every strut over 100,000 miles needs replacement right away or the car is unsafe to drive. On the contrary, if it comes down to replacing a strut or paying the rent, the answer is obvious. And it is rare that I find a strut worn to a point that I recommend replacement immediately as a safety issue.

But I also find it laughable when someone points out that they are still driving a car with 200,000 miles and the struts are “perfectly fine.” They simply are not. Period.


#18

I’ll have to respectfully disagree with asemaster. I currently own a car with well over 200k, and as far as I and my mechanic can tell, the struts are fine. That being said, as was said earlier, the rubber parts could probably stand to be replaced if I cared. I had the struts, steering knuckles, tie rods, etc. all checked out when I got an alignment/new tires and the mechanics couldn’t find anything they recommended replacing.

I’ll also add that I’m not one of those who says it’s impossible to have shocks wear out sooner, I replaced shocks on a truck with less relatively low miles that weren’t noticeably leaking and they were so bad I could compress them all the way and they wouldn’t extend.


#19

I apologize once again for the formatting, it seems like every time I post all paragraphs and indentations disappear.


#20

@Tester, there is leaking gas charge and there is leaking oil. Gas first, oil later. Gas charge is used to prevent foaming inside the pressure damper. Like with brakes, air in the pressure chaber is bad. During extension, the oil needs to rush back into the pressure chamber to fill up the volume of the rod exiting the damper. Gas helps push the oil back into the chamber on twin-tube dampers but the oil seal at the top keeps it in. Once it leaks out, the damper won’t work as well on rough roads to keep the tires on the ground but the slower motion of the body is still controlled OK. Not all twin tube shocks or struts are gas charged. The gas is a small boost in performance.

On mono-tube, or high pressure dampers, the gas is in a sealed space opposite the rod next to the pressure chamber with its own seal and a floating gas cup. When this seal fails, the shock just flat stops working since all the gas mixes in the oil chamber. It usually start knocking like you have 2x4’s in the springs because the gas cup is now smacking the piston. It nearly always leaks, too, since that rod seal isn’t designed to keep the gas in. Monotube shocks and struts are more commonly used as options on performance cars and trucks and many, but not all, have wires coming out connected to a computer.

A comment about oil leakers; a twin-tube strut can make quite a mess before it stops working because it has lots of extra oil. Shocks can’t. Mono-tube shocks and struts can’t leak much oil before they start knocking. Monotube leakage can be pretty spectacular, especially if you use an impact wrench to remove them… it can unscrew the piston letting the rod shoot out with oil spraying everywhere!