Why are bushings not designed to rotate?

[VictorH]

Title is not exactly correct but what I've noticed on the front and rear suspensions is that the bushing design is such that the suspension component will not freely rotate but is limited by the rubber bushing itself. In most other cars I've worked on, the bushing for a given suspension component is designed to prevent Lateral deflection or other movement in a plane different than the rotation of the suspension component. The suspension piece can generally rotate up and down freely.

The Mustang suspension is not like that. The bushing itself resists movement in the desired plane of operation. Why is that?
I was wondering why for example the front tension arm is torqued to 185 ft lbs and some of the rear components are well over 100 ft pound too. I think that is not that it's "needed" but it reduces the chance of the bushing itself rotating in the mount. Plus some of the bushing sleeve ends actually have serrations to prevent movement.

Anyway, wondering if anyone knows the answer to this question. Basically you are riding on the compliance of the rubber for a significant part of your ride and suspension movemen down the road. Seems odd. Hope the explanation above makes sense. Picture of my front control arm bushing below to see a bit of what I mean.

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[Järn]

Cost. Ford put in inexpensive binding rubber bushings at eight key suspension joints in the IRS. There are vendors that sell replacement parts with bearings for each of the 8. I have replaced 4 of the 8 bushings with parts from Steeda and Ford Performance, with fantastic results. Both of the steering control arms can also be replaced/improved.

 

[Jaymar]

This is only speculation so take it for what it's worth but I believe that the bushing deflection in rotation is built in as part of the suspension movement. It behaves much like a spring but it reverses its direction of force once past the center point. Many people who replace the rear lower control arm bushing with a bearing report increases in movement in the rear suspension.

 

[VictorH]

This is only speculation so take it for what it's worth but I believe that the bushing deflection in rotation is built in as part of the suspension movement. It behaves much like a spring but it reverses its direction of force once past the center point. Many people who replace the rear lower control arm bushing with a bearing report increases in movement in the rear suspension.

I totally agree with this. I don't think it's speculation, it had to be part of the suspension design. My only problem (not sure it's the only one) but it's not really the basis for a durable and long lasting suspension system. I could be wrong but for a performance-type car, I don't think it's the optimal approach.

 

[NGOT8R]

I have every Steeda rear suspension part available (including the spherical bearing) on my 2019 Bullitt, plus a BMR camber lockout kit. How important is a camber arm upgrade for drag racing? If I decide to stick with the factory camber arms for now, which slot (the one closest to wheel or the one closest to the center of car) is recommended for the best compromise when switching between factory wheels and a drag pack?

 

[thompsje]

I totally agree with this. I don't think it's speculation, it had to be part of the suspension design. My only problem (not sure it's the only one) but it's not really the basis for a durable and long lasting suspension system. I could be wrong but for a performance-type car, I don't think it's the optimal approach.

Anything that can rotate freely needs clearance. Clearance can allow for dirt and water intrusion, unless you can figure out a way to reliably boot and gasket everything. Ford builds cars as daily drivers and that brings compromise. One is the understanding that there is only so much maintenance and regular inspection that most owners are willing to do.

Another is the cost that people are willing to pay for the initial purchase and ongoing maintenance. For every one of us here, there are 10x more Mustang owners who would shit a brick if part of the maintenance schedule was a full suspension overhaul every 10k miles. There is a reason that nearly everything other manufacturer also uses bushings.

Personally, I think Heim joints and/or spherical bearings are a poor choice for most street use. Water, salt, and dirt would kill them in a year for me. I *would* like to see options like higher durometer rubber or poly replacements as factory parts in more applications tho. That's where I think that Ford really misses the target. The bushings are generally way too soft to combat NVH when the difference is probably minimal. For the ease of a replacement, I'd redo every control arm with a poly bushing option rather than trying to press them out myself.

 

[VictorH]

I have to agree with you too. However, my prior car was an E90 M3 and none of the bushings were like this. And, yes, there were boots on everything so that obviously helped. I had a tension arm monoball upgrade to the front suspension and got 70,000 miles out of it and many, many track days before I replaced them as a matter of precaution (replaced the aluminum arms as well).

The one good thing I can say about the monoball upgrade to the front of the Mustang is that the steering feel went from really numb to, I can actually feel some of the road surface now through the wheel. To me that is a huge plus and nice to have especially for track work.

 

[thompsje]

Yeah, I think we're on the same page. Before the S550 chassis was even released an E90 M3 probably had an average sticker price of 2x a base GT. I would hope you get some trick components for that cost.

I've had BMWs too (although not an E90 M3), and there's definitely a reason a given suspension arm for a Mustang costs $100 and similar one for a BMW is a lot more. It's not just the M tax. I don't track, and I'm frankly enjoying that I can almost rebuild an entire Mustang suspension for way less than I'm used to.

 

[shogun32]

what would make more sense is if the clamping force was less, and the interface between mating faces had a very thin but durable shim between them so the joint could articulate freely or at most with modest force.

https://www.mcmaster.com/98089A224/
https://www.mcmaster.com/98055A211/

2 or 3 of these in a stack well greased with wheel grease (so it'll stay on) at each surface might prove useful.

Some of aftermarket bushing replacement kits are such that the center shaft being clamped with the thru-bolt can freely rotate in the bushing.

 

[VictorH]

Heck YES! Before I went to the Ford dealer last week to get a couple of nylock nuts for the ball joints that I had to remove for the control arm, I asked my wife for a $20 bill. I did that thinking the same nut for a BMW would run $4 or $5 each (wasn't thinking about the Ford equivalent). My total for two Ford Parts Nylocks from the local dealer? $2.12 for both including tax! That's so cool.

 

[Bossdog]

After market rear camber arm and lateral link seem like not real valuable upgrades until you watch the you tube video attached in post #2. Eliminating the suspension binding and allowing your expensive Magneride dampers and springs to actually do their job seems to me to be a very good reason to upgrade these parts, especially of you intend to road race.

Any downside to upgrading these 2 parts?

 

[shogun32]

Any downside to upgrading these 2 parts?

Thinner wallet. Better sitting posture.

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