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Brakes & Suspension Forum sponsored by The Tire Rack |
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05-27-2020, 11:18 PM | #1 |
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Member#: 475476
Join Date: Oct 2017
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Rear Suspension Bushings Squeaking? - Modified
I had a few questions when it comes to bushings in general... I've done a lot of research before all the work I've done on the car, and I like to think I did a decent job of making sure to upgrade everything accordingly? And so, I don't like to think I may have missed something important that needs a more professional eye!
A little bit of background: I own a 2018 WRX STI I've been modifying the past 2 years. I've had a lot of work done to it, through and through, and just finished a wave of suspension work and upgrades. I track her occasionally, and drive her weekly. List of suspension upgrades: -STI Front & Rear Swaybars -Tanabe Sustec Strut Tower Brace -Fortune Auto 500 Gen 7 Coilovers 9k/9k Swift Springs -Perrin Front Control Arm Bushings -Perrin Front Endlinks -Perrin Rear Endlinks -Torque Solution Rear Upper Inner Control Arm Bushings -Torque Solution Trailing Arm Bushings -VooDoo13 Adjustable Lower Control Arms (Rear) -VooDoo13 Adjustable Toe Arms (Rear) -Whiteline Rear Subframe Bushing Kit -Whiteline Front Roll Center Bump Steer Correction Kit The bushings are all polyurethane ones I've installed all of those myself at home, following correct torques, procedures, etc. She just came back from the shop for a full alignment work and corner balancing after all that. The rear end is squeaky/creaky, on the up-down movement. I'm worried that perhaps I didn't use enough lube on some of them, and they may bind? But that brings me to my main question.... how do you notice bushings binding? Do you need to go through extreme cornering loads to feel what that feels like? What are some of the consequences if not addressed? She's only lowered by about an inch/inch and a half, 3 degree camber front, 2.5 camber rear, 0 toe front and rear, 50/50 corner balance. I'm slightly worried when I DO take her to the track again, the bushings maybe bind or do something bad and cause an accident I'd rather avoid, safety is paramount! If all I have to worry about is just the squeaking, then that's fine, I can re-lube them if needed Feel free to drop any questions, I'll do my best to answer! I just want to understand more about these things so I may be aware if something happens, what to do to prevent it, etc. Thanks everyone
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05-28-2020, 01:06 AM | #2 |
Scooby Newbie
Member#: 401922
Join Date: Sep 2014
Chapter/Region:
BAIC
Location: NorCal
Vehicle:2018 STi WRB |
Adding to OP's concerns, I have installed Voodoo13 Rear LCA's in the past and think I have experienced the same noises when I had them installed onto my car. The noise happened every time I went over a bump or dip. It didn't matter how large or small the imperfections of the road were. The noise happened so much that I eventually replaced the Voodoo13 Rear LCAs with a SuperPro Rear LCA. The noise went away instantly. Here's a video of the squeaking I experienced (and suspect that the OP is experiencing as well).
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05-28-2020, 01:15 AM | #3 | |
Scooby Newbie
Member#: 475476
Join Date: Oct 2017
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Quote:
That does sound, pretty similar! I'll have to try and compare it to what I hear on my own end. A bit difficult to hear over the exhaust, but I appreciate the input! I wonder if it's because of the ball bearings. If THAT'S really all there is, I'm not going to worry too much ( noise is fine lol ) Thank you! |
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05-28-2020, 04:23 AM | #4 | |
Scooby Newbie
Member#: 401922
Join Date: Sep 2014
Chapter/Region:
BAIC
Location: NorCal
Vehicle:2018 STi WRB |
Quote:
Say, what front & rear sway bar sizes are you running and how are you liking your setup? Is it oversteer prone? Does it reduce the mid-corner understeer tendencies of the car? |
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05-28-2020, 09:03 AM | #5 |
Scooby Specialist
Member#: 498642
Join Date: Mar 2019
Chapter/Region:
Tri-State
Location: our wrx IS the family sedan
Vehicle:'19 WRX Ltd 6M dgm '08 Mustang GT (the toy) |
Polyurethane bushings tend to squeak mostly because of the way they're usually designed. Sometimes in some applications a bit of clunking can also result.
The source of those problems is in the polyurethane bushing parts being longer than the sleeves that go inside them. This starts allowing the poly to be put under compression as you torque the fastener even before the sleeve starts getting clamped, and as the suspension moves the flat faces of the poly rub against the brackets. Poly is kind of a sticky-slippy material, and will not slide smoothly (hence the usual need for lubing them). Makes me wonder how well the producers of poly bushings actually understand suspension function. There is a DIY fix for this, where you hit the flat faces of the poly with a belt sander or hold them up against a bench grinder wheel to reduce their length to the same length as the sleeve that runs through them or a tiny bit shorter (I'm talking less than 1/32" being plenty here). The only possible downside is potentially shorter life, but poly bushings should really be considered "wear parts" from the get-go. That doesn't imply frequent replacement; some of the bushings I've modified in this (and somewhat more extensively with other efforts) have lasted in excess of 8 years and are still holding up just fine in driving that includes HPDE road course time. I lube them once a year as part of going through the car for the first track day of the season and they don't ever squeak. Norm |
05-28-2020, 09:39 AM | #6 | |||
Scooby Specialist
Member#: 498642
Join Date: Mar 2019
Chapter/Region:
Tri-State
Location: our wrx IS the family sedan
Vehicle:'19 WRX Ltd 6M dgm '08 Mustang GT (the toy) |
Quote:
Quote:
The end result of this induced stiffness is some extra rear roll stiffness, kind of like swapping out the rear sta-bar for a stiffer bar or going with heavier rear springs, and the result is pretty much the same (less understeer to possible oversteer in combination with other efforts intended to reduce understeer). I don't have any idea what the numbers here would look like, but on a different chassis going to poly added almost as much roll stiffness as the car's rear sta-bar (this was actually tested). On one of mine (a stick axle car) the difference in lateral head-toss going from rubber to poly in the rear suspension linkage was easily noticeable. FWIW, IRS vs stick axle doesn't change the fact that poly bushings just don't like to be 'squished' in order for suspension linkage arcs to all agree with each other in 3D. The good news is that further DIY efforts can reduce this induced roll stiffness side effect as well. I might even have a sketch somewhere. Quote:
It might be worth first trying it out at autocross to get some idea if the handling might be a bit too loose for the higher speed stuff. Failing in that, take it easy, even on the out lap, and be even more willing than usual to back off a bit and point people by. Norm |
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05-28-2020, 09:48 AM | #7 |
Scooby Specialist
Member#: 498642
Join Date: Mar 2019
Chapter/Region:
Tri-State
Location: our wrx IS the family sedan
Vehicle:'19 WRX Ltd 6M dgm '08 Mustang GT (the toy) |
Mainly for Thor's benefit . . . I'm a retired engineer who has dealt with suspension bushings off and on for 25 years or so. I also drive at HPDE track days in either the intermediate or advanced run group depending on what entity is putting on the event. I am not an instructor, and to tell the truth I really consider myself an "Intermediate".
Norm |
05-28-2020, 02:10 PM | #8 | |
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Member#: 507317
Join Date: Oct 2019
Chapter/Region:
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Location: SW Ohio
Vehicle:2019 WRX Pure Red |
Quote:
The noise, from where the camera was sitting, almost sounded like metal on metal knocking. like if one of the mounting holes on the LCA was just enough bigger than the bolt going through it to allow for movement of that bolt to cause contact with the hole sides. I don't have poly rear bushings, nor do I have aftermarket rear LCAs/TAs. I really wish that some of these bushings were still made of (solid) rubber with a harder durometer and zero voids so that the benefits are rubber are still there, but also the benefit of stiffer than OE soft squishy test drive feel was gone. Note: Adding solid rubber front LCA bushings to my Mk4 GTI really changed the characteristics of the car and the steering feel. The OE busihings had voids in them to make the ride soft and compliant, but the solid ones really brought the drive in line with the spirit of the GTI. |
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05-28-2020, 02:46 PM | #9 | |
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Join Date: Oct 2017
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Quote:
Norm, Thank you for all the amazing insight, this honestly helps a whole ton, I super appreciate it! I used PTFE synthetic lube on all the bushings for their interior and housings, and normal grease to their faces. It could be the grease is just not good enough, as yes indeed the bushings get VERY squished in, like you mentioned. I'd probably be too afraid of sanding them and messing a set up, or not making both sides match on it. I HAVE heard at least for their internal bore and outer area, to use teflon tape and then lube it up before sliding them in, supposedly helps eliminate friction, which is something I may try. I'll have to take her into some windy roads up the hills and bang her around a bit to see what I get in response, I completely agree with you that tracking her the next time with this new setup will be a slowly but surely approach, getting a feel to how the car behaves, what it likes, what it doesn't like, and so on. I'll report back with some findings, might try to snag a video if possible! |
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05-28-2020, 02:51 PM | #10 | |
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Quote:
I'm running the stock STI sway bars, which are 24mm front and 20mm rear. I don't think I'll upgrade them, as they do just fine for me for what I do! Current setup has just been finished a few days ago, so I don't have a good feel for what it likes and doesn't like, this weekend I'll probably re-lube some of the bushings I can reach ( without needing to drop the entire subframe like for the rear upper control arms ) and then test her on some windy hills and see how she does. |
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05-28-2020, 04:02 PM | #11 | ||
Scooby Specialist
Member#: 498642
Join Date: Mar 2019
Chapter/Region:
Tri-State
Location: our wrx IS the family sedan
Vehicle:'19 WRX Ltd 6M dgm '08 Mustang GT (the toy) |
Quote:
Quote:
Norm Last edited by Norm Peterson; 05-28-2020 at 04:41 PM. |
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05-28-2020, 04:35 PM | #12 | ||
Scooby Specialist
Member#: 498642
Join Date: Mar 2019
Chapter/Region:
Tri-State
Location: our wrx IS the family sedan
Vehicle:'19 WRX Ltd 6M dgm '08 Mustang GT (the toy) |
Quote:
At this point, I simply plan on modifying any polyurethane bushings as something that gets done as initial bushing prep even before jacking the car up. Doesn't matter if I'm replacing only the bushings or the whole arm. Normally, I grind the ends into flat cones to better accommodate any off-axis rotation. Quote:
Norm |
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05-28-2020, 05:08 PM | #13 |
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Vehicle:87 Yugo Red |
If I may throw my experience into this as well.
Lube choices for urethane bushings is pretty crappy. Oil based will break down, harden and decay urethane. Water based will wash out. By far the best AND cheapest lube I have ever found for urethane bushing is silicone grease. Head down to your local hardware store and hit the plumbing aisle. You'll be able to find it in a small tube for a few bucks with the o-rings kits for faucets as that's what it's used for. It's waterproof, and will not decay the urethane. Now, on to the problem you're having, please also check the upper mounts on the shocks in the rear and make sure you're not getting some creaking noises from those as well. |
05-28-2020, 05:19 PM | #14 |
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[quote=Norm Peterson;46327702]I'm convinced that you need to at the very least greatly reduce how much the poly is being compressed before you'll have anything resembling even a semi-permanent "fix". You don't need machine-shop precision here, and matching the two sides really doesn't matter because the poly will self-center itself along the length of the sleeve. Remember, you only need to have the poly a tiny bit shorter than the sleeve to remove all of the compression. And this tiny amount shorter doesn't have to be a perfectly even amount shorter all the way around as measured with a micrometer, just that little bit shorter everywhere.
At this point, I simply plan on modifying any polyurethane bushings as something that gets done as initial bushing prep even before jacking the car up. Doesn't matter if I'm replacing only the bushings or the whole arm. Normally, I grind the ends into flat cones to better accommodate any off-axis rotation. Gotcha, so you're basically just making a flat cone to remove a little bit of material so it's not a flat face pressing onto the housing. I might look into it for sure. It seems I'll have to at the very least remove the rear upper control arms and rear trailing arms and re-lube/ over-lube the housings, bushings, everything, and then go from there at the very least |
05-28-2020, 05:23 PM | #15 | |
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And thats a good point, I'll check if the shocks housing is not the creaking part, within the trunk |
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05-29-2020, 06:51 AM | #16 | |
Scooby Specialist
Member#: 498642
Join Date: Mar 2019
Chapter/Region:
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Location: our wrx IS the family sedan
Vehicle:'19 WRX Ltd 6M dgm '08 Mustang GT (the toy) |
Quote:
Making the faces flat cone shapes improves the bushing's ability to accommodate off-axis link rotations or when the two chassis-side bracket pivot axes for an arm are not perfectly aligned with each another. Norm Last edited by Norm Peterson; 05-29-2020 at 06:56 AM. |
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05-30-2020, 09:44 PM | #17 |
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I went ahead and took a video today of me bouncing on the trunk, full weight on, while recording under the car for any squeaking or creaking. All I could hear were the shocks...
So now I'm wondering if I was just hearing that, or the car frame flexing a bit from the stiffer setup https://imgur.com/a/NPYlyTP video with audio |
11-09-2020, 03:58 PM | #18 |
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Vehicle:08 OBP Sti |
I have this exact issue only people 18 feet away can hear the grind clunk sound last few months its been unbearable loud after listening to it for 2 years. Will be tearing both control arms put in a used upper soon enough and see if that fixs the problem. I assume its maybe my upper control arms my front lca ball joints where metal on metal around seven years so i guessing all the rubber bushings on the lca are pretty useless now.
I even had the rear struts removed reinstalled problem is still there only louder when its not cold out. ISC lower control arms 3 years, oem upper 11+ years old RCE endlinks Whiteline sways 22mm f/r, various WL support stuff Feal 441s |
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