Another trailing arm bushing question, Polly bronze durable? Options

[trojanhorsepower]

I relatively recently installed my new set of 914rubber bushings. These were purchased maybe 10 years ago and installed maybe 5 years ago, but since the car was apart they have almost no miles on them. After finally being able to drive the car I found this.

https://www.youtube.com/shorts/2DWFetQ51aE
https://www.youtube.com/shorts/H5XFSS_rh74

So clearly these don't fit properly. I was going to go with the Elephant racing kit, but a friend of mine installed poly bronze bushings on his Jeep and they did not last a year. Anyone have any experience with these bushings as to long term durability? Or should I just bite the bullet and go with the soft rubber original style?

Thanks,

Peter

[tygaboy]

I have polybronze in the LS car with about 6000 miles over 5+ years and they're fine. You need to keep them lubed - I think the service interval is every 5000 mile but check with the mfg. I believe it's a requirement to add zerk fittings to enable lubrication without disassembly. In looking at your videos, I didn't see any zerks so maybe those weren't maintained as needed?

[trojanhorsepower]

No zerks these are the duralan type material. Basically no miles. Literally on and off the trailer a few times and up and down the road maybe 3 times, so 5 miles total? Are you supposed to install the zerks for the plastic/rubber bushings?

Thanks

[tomeric914]

I installed the Elephant Polybronze bushings 15 years and at least 20k miles ago. As Chris mentioned, lube them regularly and you'll have no problems.

Before the Elephant bushings, I did try someone else's bushings and they failed miserably after 3 months.

[mepstein]

I bought from that first batch of 914 bushings. They were junk. They slid on by hand so obviously the wrong dimensions and tolerance.

[trojanhorsepower]

OK thanks guys. Elephant bushings it is.

[mepstein]

OK thanks guys. Elephant bushings it is.

The ER bushings are known to just work. Not cheap but reasonable for how long they should last.

[Superhawk996]

Elephant racing and Restoration Design both offer properly sized rubber bushings.

There are numerous downsides to bronze and poly bronze for street use.

[Montreal914]

Bruce Stone installed a set of Prekom rubber stock (or sport (IMG:style_emoticons/default/idea.gif) ) in my arm. They were a pain to install as they should. On Prekom's list page when hovering, the description says designed and made in the US. But when you click on the description, it states these were designed and are fabricated in EU per original specifications. I belive it is the latter.

https://www.prekom-usa.com/product/porsche-...bushings-stock/

There was a thought these could be the same as the ones sold by ER in this kit below. They are also sold by Restoration Design EU.

https://www.elephantracing.com/porsche/914/...for-914/rubber/

Time will tell if they last.


Having purchased a set of Rebel Racing front (RSR) bushings, I have been wondering how their matching rear kit is. (IMG:style_emoticons/default/idea.gif)

This: https://www.rsrproducts.com/product-page/re...ear-bushing-set

After talking with @bdstone914 who has restored many trailing arms, one of the issue with any of the rigid options comes with the fact that the cylindricity of the trailing arm's tube is deformed probably due to its welded fabrication process.

ER's polybronze bushings compliance of the red part compensates for this problem, then you have a classic bronze over steel pivot design.

[Superhawk996]

Just keep in mind none of the OEs use bronze bushings and that includes the likes of Ferrari, Porsche, Lambo, McLaren, etc. Cost is not why they use rubber bushings

[worn]

Just keep in mind none of the OEs use bronze bushings and that includes the likes of Ferrari, Porsche, Lambo, McLaren, etc. Cost is not why they use rubber bushings

Can you expand a bit about the actual down side of the bronze bushings from ER?

[Superhawk996]

Just keep in mind none of the OEs use bronze bushings and that includes the likes of Ferrari, Porsche, Lambo, McLaren, etc. Cost is not why they use rubber bushings

Can you expand a bit about the actual down side of the bronze bushings from ER?

There is a big degradation on the amount of road noise, tire noise, and impact noise (noise over bumps) transmitted into the cabin vs rubber bushings.

There is a significant increase in the spike loads input into the chassis - this reduces durability of the chassis pick up points like the suspension console. Rubber bushings absorb that spike loading.

With no rubber wind up from the bushing you lose some damping of the suspension as it travels over small bumps and road input - this makes the dampers work harder to control the wheel motion.

The maintenance aspects and misalignment aspects were mentioned above by others.

The need for ongoing maintenance, chassis loads, durability, and poor NVH are the main reasons OE’s won’t touch something like poly bronze bushings.

They have advantages on track / race cars but there maintenance, and frequent replacement are part of the game.

[trojanhorsepower]

Well dang, already ordered the poly bronze ones. I guess if these are too harsh I will replace them someday with rubber ones.
Thank you all for your input. The next big question is can ER get them here in time for me to install them before Okteenerfest?.....

[mlindner]

Well, I've got polybronze installed over five years ago and about 4,000 miles per year. No noise, ride is not overly harsh. Only service is grease every spring. I think they are perfect for a 914 that is driven. Mark

[mlindner]

Just a fun shot after the install of the Polybronze bushing. All cleaned up, following instructions going in next day. The guy in the picture is my buddy who came to Wisconsin in the middle of winter from Florida to help me and share the fun. Mark

[bdstone914]

Bruce Stone installed a set of Prekom rubber stock (or sport (IMG:style_emoticons/default/idea.gif) ) in my arm. They were a pain to install as they should. On Prekom's list page when hovering, the description says designed and made in the US. But when you click on the description, it states these were designed and are fabricated in EU per original specifications. I belive it is the latter.

https://www.prekom-usa.com/product/porsche-...bushings-stock/

There was a thought these could be the same as the ones sold by ER in this kit below. They are also sold by Restoration Design EU.

https://www.elephantracing.com/porsche/914/...for-914/rubber/

Time will tell if they last.


Having purchased a set of Rebel Racing front (RSR) bushings, I have been wondering how their matching rear kit is. (IMG:style_emoticons/default/idea.gif)

This: https://www.rsrproducts.com/product-page/re...ear-bushing-set

After talking with @bdstone914 who has restored many trailing arms, one of the issue with any of the rigid options comes with the fact that the cylindricity of the trailing arm's tube is deformed probably due to its welded fabrication process.

ER's polybronze bushings compliance of the red part compensates for this problem, then you have a classic bronze over steel pivot design.

There are several reasons why rubber bushings are a better choice over hard material ones like 914 rubber makes. The rubber adds dampening as is grips the shaft.
Almost all shaft are bent. I have torn down over 20 pairs only to find a couple pair that are not bent. This makes hard bushings more difficult to install. The trailing are also not consistently round and the bushing ends not in line. This is from the forces of cornering.
The holes can be oversized. I had a pair of the 914 rubber bushing and they fit loose.
The Prekor bushing are very difficult to install. I have done four sets abd it takes about 4 hours. I had to make tools to install them. I ripped three bushing out of four sets installing them carefully. The design is flawed. It has an undercut below the flange where it should be thicker. The flange can tear off. They have no instructions or do they know how to install them. I have had several conversations with Igor at Prekom about improving the design. I don't know if they improved them.
ER buys Prekor and marks them way up
They at least sell the tools with them.
I am not addressing poly bronze bushings as I have not used them.
That my story and I'm sticking too it.

[rjames]

Anyone using the RSR/Rebel Racing bushings?
https://www.rsrproducts.com/product-page/re...ear-bushing-set

[mepstein]

Well dang, already ordered the poly bronze ones. I guess if these are too harsh I will replace them someday with rubber ones.
Thank you all for your input. The next big question is can ER get them here in time for me to install them before Okteenerfest?.....

There’s a lot of people that really like them. There are so many things that go into making a suspension feel harsh or compliant. Tires, tire pressure, shocks, all the other suspension bits, etc.

[trojanhorsepower]

OK. Well I'll hope for the best. They did not ship today so probably have to go to Okteenerfest on the wabbly ones. It should be fine I won't be driving much (probably just on and off the trailer)....

[yeahmag]

Anyone using the RSR/Rebel Racing bushings?
https://www.rsrproducts.com/product-page/re...ear-bushing-set

I'm using them and really like them. My opinion on ride quality may be different than others, but I like a non-binding, low maintenance bushing like teflon. The rear bushing is by design collinear. When you remove the spring, you can move the swing arm through it's arc with 1 finger. I also run their front bushings with self leveling washers for the same reason.

I beat the hell out of these and they are still good as new.