Your experience with polyurethane cradle bushings ?

[Martinnfb]

Hey guys , I just ordered a set of poly cradle mont bushings from Energy Suspension. I was wondering if anybody can provide any feedback about this upgrade . It seems to be reasonably beneficial way how to straighten my subframe cradle and get a rid of the deflection in the rubber ones.
Cheers
M.

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[BmacIL]

Not many people outside of those with dedicated racecars have done them, and most of those folks do aluminum bushings. There's honestly no reason to do poly bushings when you have something like the CB005 lockout kit available.

 

[Martinnfb]

Thanks for the input. I am aware of lockout kits, yet once I'm dealing with the rear end, it seems to be reasonable to replace the rubber completely. I am not going to track this car, so solid (aluminium or Delrin) bushings are out of the question, yet I am curios to see , how it would be if Ford had chosen the right approach
Also I am in the limbo, trying to decide if I should go with a full replacement of the differential bushings as well ? It would make sense to get the diff. lock out kit and see if I like it, and again, once the cradle is down I might as well go full poly . Also I am not sure about the noice increase with 3:73 gears.
Seems like not many guys took this path on the daily driven cars.

 

[BMR Tech]

Do not do the full replacements.

I promise you, there really is not any benefit to a full replacement poly bushing over a "lockout" or "insert" style modification.

The only time I suggest a full replacement is if the customer is set on it and they're okay going with something "solid" such as Delrin or Aluminum material.

 

[Martinnfb]

Thanks Kelly, I hear what's you saying , however lockouts and inserts won't stop the deterioration of the rubber parts and full replacement of the cradle bushings will have the same effect with the benefit of simplicity and longevity . Or am I missing out on something?

 

[BMR Tech]

Deflection, articulation and sagging are the biggest contributors to the OE rubber bushings deteriorating. Environmental conditions also play a factor, but the damage caused from the environment is amplified when you have the 3 conditions I mention above. Polyurethane is still a polymer and subject to the same conditions and results.

With the lockout parts, you drastically reduce the fatigue stresses on the factory bushings....so the odds of the bushings failing or deteriorating is very low.

 

[Martinnfb]

The previous mustang I bought 17 years ago and it's still in the garage . The new one is our retirement car, so it will be a while. However even if I sold the car next year, I would feel much better to sell/buy a car with a full polyurethane rear end rather, then one that is full of add-ons.
Back to the original question, if anybody can provide feedback I would be most grateful.

 

[Martinnfb]

Deflection, articulation and sagging are the biggest contributors to the OE rubber bushings deteriorating. Environmental conditions also play a factor, but the damage caused from the environment is amplified when you have the 3 conditions I mention above. Polyurethane is still a polymer and subject to the same conditions and results.

With the lockout parts, you drastically reduce the fatigue stresses on the factory bushings....so the odds of the bushings failing or deteriorating is very low.

To my understanding almost every polyurethane bushing manufacturer has lifetime warranty for it's product. No way that we can say that natural rubber last anywhere near to the lifespan of a polyurethane .
If my local dealer had access to BMR product I would go with BK 047, and the reason is simple. If I put lock out on rubber bushings in next 6to 10 years the lockout kit will be still fine , but the original OEM bushings would have to go out anyway. How do I know? Did it on my (at the time) 12 year old fox-body, where every rubber component was distorted or completely destroyed .
So that is my reasoning for a full set of bushings, now back to the point.
Kelly how is the feedback from customers, that installed BK047 ?
Thank you

 

[BMR Tech]

Feedback is that they wish they went with lockout kits.

FYI - We were by far the first company to make and test and release poly replacement pieces for the S550 Mustang IRS system. My recommendations have some substance, I assure you.

You seem set on the full poly replacement pieces. Nothing wrong with that, but I feel your reasoning is based on your experiences that are somewhat irrelevant. If you eliminated the movement, bind and sagging of those pieces you mention - they would not have needed replacing. A pivot point bonded rubber bushing and a "support" rubber bushing are totally different.

 

[BMR Tech]

There are also OE Subframe design characteristics that make a poly bushing subframe mount somewhat unreliable over time with repeated shock loads.

If I wasnt traveling right now I would share some data. I'll try and throw some images up when I get back next week to explain further.

 

[Martinnfb]

Thanks for sharing the feedback Kelly, Is there any particular reason, why ? Noise, need to grease perhaps ?

I know your work Kelly and I do admire your dedication and respect your expertise, however my experience is relevant. In past 17 years I have been working on previously mentioned suspension and could first hand observe wear and tear of bushings, heim joints, delrins you name it. $95 000 later I stopped counting and set it on Polyurethane. That was at the point when I decided not to track the car and bring it back on the street. That is the reason why I am so set on the full-poly setup.
From what you said I understand that the lockout inserts will absorb the load and therefore increase life of the OEM rubber. That might be the case, but if you replace the rubber with urethane, you will eliminate the weak point all together. And frankly I was contemplating aluminium inserts , but there is almost no feedback available .

I would love to now more of what people think about poly bushings. Experience based, preferably.
Cheers
M.

 

[Martinnfb]

There are also OE Subframe design characteristics that make a poly bushing subframe mount somewhat unreliable over time with repeated shock loads.

If I wasnt traveling right now I would share some data. I'll try and throw some images up when I get back next week to explain further.

That would be fantastic. Can I possibly call you once you're back at the office in order to bug you little more ?
Cheers

 

[xXANCHORMONXx]

I’m probably your best bet.

I had a 15 EcoBoost with 450 plus hp and BMRs full catalog on the car.

As far as the rear subframe I had Delrin subframe mounts and poly diff mounts.

The sound transfer into the car was awful, it took months to break in until it finally became semi bearable.

I sold it and bought a 16 GT350 and put the BMR bits on it but instead I did the lockout on the rear and their rear subframe brace.

I do time attack every other month on the EB and now with the 350 and couldn’t be happier with my decision.

The only way I would do solid bushings again is if I converted my car into a full race car, but I don’t see the upside.

 

[Tractor Junk]

I’ve got the BMR derlin bushings in the subframe mount. Ford Performance had stopped producing the aluminum units at the time, so BMR was my backup solution. The only reason to use these vs. some type of lockout is weight. If you are concerned about weight, and I am in a big way, then go with the bushings.

Don’t get these if you’re sensitive to NVH. However, they’re great for a track car and the product quality is great.

 

[Martinnfb]

Thanks Guys for sharing, much appreciate your response.

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