Poly Bushing Failure at Road Atlanta

[Flyboygsxr]

That makes sense due to the 360 degree articulation allowed by a spherical type bearing. In this case is the panhard bar mostly responsible for keeping the rear axle centered laterally from side to side?

 

[Grant 302]

Good point about the spherical ends. Yeah, I can see how they allow for angular movement without putting force on the arms themselves.
I'm not really sure why Ford made theres tubular and steel. I did wonder when I put mine on why they were so hefty. I just assume its a part that requires it.

Would be cool to see a force plot (the spectrum-y looking ones) of one in action. For that matter, I'd love to see one for every part to know where most of the forces are concentrated on it. I bet we'd find some surprises there for some parts!

Generally speaking, the use of steel is safer. IMO, tubes are fine for steel. My comment about not using tube is only for aluminum. *If* it failed in torsion, it would fail in a bad, very sudden way.

I dunno..I thought real time stress/strain plots were kinda boring!

 

[Grant 302]

That makes sense due to the 360 degree articulation allowed by a spherical type bearing. In this case is the panhard bar mostly responsible for keeping the rear axle centered laterally from side to side?

Yes, the panhard or watts link. And I'd say 100% responsible for lateral location with a '3-link' rear suspension.

If/when you have the time, lookup Ford's old 4 link on the Fox and SN95. They used two upper links to locate the rear laterally and with poly bushings, it would bind like crazy!

 

[2012-Boss]

My biggest concern is one side is spherical and the other is delrin. How much stronger is delrin than poly? I wish both were spherical but I can't justify spending that much money right now to buy the Ford Racing control arms. Just bought the race spec MGW shifter and some other parts plus another set of tires. Man this sport is expensive but I LOVE IT!!!

I have run the same Steeda arms with poly and not delrin combined with the axle side bearing for two hard seasons without issue. It is a very good design.

What you need to remember is that poly does not perform well with torsional force -I.e. Poly doesn't twist well. It does fine with compression. Placing a bearing at the axle effectively eliminates the force that causes failure in this application.

 

[DGRacing]

I have run the same Steeda arms with poly and not delrin combined with the axle side bearing for two hard seasons without issue. It is a very good design.

What you need to remember is that poly does not perform well with torsional force -I.e. Poly doesn't twist well. It does fine with compression. Placing a bearing at the axle effectively eliminates the force that causes failure in this application.

You're still going to get some deflection with that poly which means less traction.

 

[Flyboygsxr]

I have run the same Steeda arms with poly and not delrin combined with the axle side bearing for two hard seasons without issue. It is a very good design.

What you need to remember is that poly does not perform well with torsional force -I.e. Poly doesn't twist well. It does fine with compression. Placing a bearing at the axle effectively eliminates the force that causes failure in this application.

My Steeda lowers worked without issue for two seasons also until they didn't. Just be careful because if you don't have spare bushings it will leave you stranded somewhere or end your track day early. Not sure if I mentioned that in the thread but it wasn't only the upper that failed. The lowers failed the previous season.

You are right when you say poly doesn't twist well. Mine failed when I started using race pads and slicks. The extra grip and heat the is conducted into the arms will weaken the poly and it will fail. My UCA only lasted me half a season before it went. Learn from me because I would have to have to say I told you so. I would replace those bushings at a minimum every season. Poly is okay for a stock setup or a beginner but when you start getting faster I would be hesitant to stick with the poly. Just my thoughts…happy racing

 

[2012-Boss]

You're still going to get some deflection with that poly which means less traction.

I would certainly agree that for a track only vehicle, bearings on both ends is best. For a street car that sees some track time, the poly / bearing combination is a great compromise for better than stock articulation and reasonable NVH.

 

[2012-Boss]

My Steeda lowers worked without issue for two seasons also until they didn't. Just be careful because if you don't have spare bushings it will leave you stranded somewhere or end your track day early. Not sure if I mentioned that in the thread but it wasn't only the upper that failed. The lowers failed the previous season.

You are right when you say poly doesn't twist well. Mine failed when I started using race pads and slicks. The extra grip and heat the is conducted into the arms will weaken the poly and it will fail. My UCA only lasted me half a season before it went. Learn from me because I would have to have to say I told you so. I would replace those bushings at a minimum every season. Poly is okay for a stock setup or a beginner but when you start getting faster I would be hesitant to stick with the poly. Just my thoughts…happy racing

You had poly on both ends of the LCA, correct? That is something I wouldn't do on a car that sees the track. I would have a bearing on at least one end.

 

[BigTaco]

Poly bushings can be used on the track, you just have to service (replace) them. Inspection is the key. Look at the 302R, they had to use poly because of the rules and Mutimatic kicked a lot of ass with the FRPP poly arms. The 302R was an endurance racer to boot. The 302S Arms with the spherical arm are way more durable but even those will wear out. All suspension bushings will wear out no mater what they are constructed of. With this in mind, buy from a supplier that tested and engineered their parts to work, not just to fit. One of the top sellers does the latter and yet has good feedback because their parts are cheap and they are willing to send out replacements to the customer after parts failure. I'm willing to spent more on something that was thoroughly engineered,tested and beaten on before it was offered for sale. My .02....

 

[steveespo]

+1. Funny thing is I considered swapping to poly bushings this year because the clunking on the streets does drive me crazy......this reinforces my decision to stick with the spherical bearings on the UCA.

Tough thing is many of us want (wanted) to have our cake and eat it too, I have come to realize if you are going to run super stiff suspension settings and race tires then the comfortable OEM or "street/track" pieces from the vendors will not allow the maximum performance improvements the other components can provide and that durability will suffer on those parts. Most, if not all rules unlimited race cars use solid bearing connections at suspension articulation points. They don't ride well on the street and make a helluva racket on all but smooth pavement.

Early on we had a thread started by Gary of "I did what I said I wouldn't" which basically was an upgrade to all the Ford Racing suspension parts used on the Continental cars at the time plus the Steeda UCA and spherical bearing. It was a commitment to support his speed on the track as well as the associated increased loads from using Hoosier R6's, Gary is one of if not the quickest driver's on the Forum and the fact that he hasn't had failures of the components is an advertisement for their suitability.

Freeing up the rear axle from all of the stretchy/binding/non linear Ford bushings allows the axle to clearly communicate what it is doing to the driver. Now if the driver can understand rear axle language he can take advantage and gain speed, if not then not much improvement and possibly danger awaits. Right now I speak "broken rear axle", I understand most of what it is saying but can't quite alway talk back to it to make it dance. That is what I'm working on this season with the new race springs, shocks and axle connections.

 

[Flyboygsxr]

Steve,

What did you break and how did you break it?

 

[steveespo]

Sorry Adam, I didn't break anything on the rear axle, what I meant was I am speaking "broken English" the way I am trying to get the rear to rotate without spinning or losing grip on corner exit with my new setup. With much higher spring rates both front and rear I am relearning what it takes to go fast with the car. Old habits aren't working the same as the car is more responsive and more on edge than with the P springs and Konis.
What I did have an issue with was the stock differential bushing, like many others mine had a few tears in it, and was the cause of a high speed vibration that I have been chasing for a year and a half. Changed to the spherical bearing and the car was vibration free in February at VIR up to 152 mph. Thanks to wwilde for tipping me off to check it.

 

[DGRacing]

Sorry Adam, I didn't break anything on the rear axle, what I meant was I am speaking "broken English" the way I am trying to get the rear to rotate without spinning or losing grip on corner exit with my new setup. With much higher spring rates both front and rear I am relearning what it takes to go fast with the car. Old habits aren't working the same as the car is more responsive and more on edge than with the P springs and Konis.
What I did have an issue with was the stock differential bushing, like many others mine had a few tears in it, and was the cause of a high speed vibration that I have been chasing for a year and a half. Changed to the spherical bearing and the car was vibration free in February at VIR up to 152 mph. Thanks to wwilde for tipping me off to check it.

Steve. Yeah, I had to relearn the whole car after spring/coilovers/aero. I was slower with it at first, but mainly because my brain wasn't used to the new information the car was giving. But your car is faster no doubt, just need to catch up to it again. With that quicker suspension you'll need to make sure you got the grip underneath. Then it all jams together! See you in May.