Rubber vs. Polyurethane

[crv]

I've searched and know this has been brought up a few times. Looking for a little additional info on this as well as maybe results over the years as a lot of the threads were quite old. A lot of guys should have some miles on both by now.

Wondering if polyurethane body mounts are some of my problems as of late...I've seen multiple people mention that they are super stiff, smaller than rubber mounts so require more shimming, etc.

Also, my Blazer is going to be on the sand dunes for the majority of its use...which would benefit me more?

Thanks!

[DeadheadNM]

Last I used poly mounts was about 14 years ago and swapped back to rubber within months. This was on a daily driven K5 though. For me, the ride was way too rough and I didn't need any more loose screws...I've used poly leaf spring bushings with rubber mounts and been happy with the results.

[skorpioskorpio]

Interestingly, I just had this conversation with Wes from Classic Heartbeat yesterday morning. I was all set to do the poly mounts, after all my project is a 2 wheel drive conversion, handling a priority, seemed obvious and I happen to mention this and got a pretty passionate response to the contrary. Wes' take on this was that unless I planned on seriously cross bracing the frame to prevent any twisting, I absolutely did not want to use poly mounts unless I wanted to pop spot welds in the body all over the place.

Hmmm, interesting. His take was that the frame was designed to flex and the body on these trucks was not, which got me thinking, there is probably a lot of truth in this. The Blazer/Jimmy is mounted on what is essentially a shorter version of a frame designed to mount 2 independent bodies to, a cab and a bed, except in this case it doesn't, and it doesn't have a forward bulkhead to the bed, or a rear wall to the cab, or really much of a structural roof. I'm not sure that seriously stiffening the frame is really that desirable either, at least for me, I personally think there is diminishing returns on adding the weight of structure to achieve better performance, especially if you are limiting that structure to a plane with a thickness of about 8-10 inches, not to mention the hoops you have to jump through to still accommodate the trailing arms, etc.

My initial thoughts were that the poly mounts would tie the body into the frame better and help stiffen it, but after this conversation with Wes and the fact that I've pretty much exposed the whole structure of my truck in stripping it and prepping it for the rocker repairs, I gotta say, the rear of the body tub has very little twist resistant structure to it, and there is certainly none in the front clip, and not much in the cab floor. So now I'm thinking rubber it may be, and maybe poly is not such a great idea, and if I've come to this conclusion with what I'm trying to accomplish I can't imagine that poly would be desirable on a 4 wheel drive truck at all as everything I've wondered is exponentially worse on those.

[Burt4x4]

I love my poly body/tranny/engine/xfercase mounts.

Lets see hmmm back in about 1995 maybe 1994 I swapped out ALL my rubber for polly mounts.
Not just any poly ~ Energy Suspension Brand BLACK = impregnated w/poly graphite (RED does not have this)(well at the time I was researching)

The poly graphite is there to prevent "poly squeek".

Poly does flex just as well as rubber, BUTT when installing poly mounts it is very critical that you do not squeese the mount. If the poly mount is too tight (buldgeing out) the poly can no longer flex and you now have a "solid" mount.

SO you tighten the mount enough to have it all nice and sugg, but not squeesing the life out of it. Then you add a secong "keeper" nut to the bolt. I like to use nylon inserted nuts, makes for a great keeper nut.
You can "overtighten" the mount first just to seat it in place, then back it off to snugg again.

I have litterlly NEVER had to touch my mounts eversence I put them in with this know how.

Anyway Poly is not as bad as you all make it sound. I wheel and flex the piss out of my K5 and have been for years...

[turp mcspray]

I also installed the black poly mounts in my orange blazer, about 15 years ago. I used it as a daily driver for several years, and did a lot of rock crawling. I never had any issues either.

[skorpioskorpio]

Burt, Turp just curious, did you run topless? Like I said I was already set on poly, specifically Energy polys until this conversation. My project is being built as a daily and I am building it so I can drive it like I stole it, but I don't want to trash the tub in the process. It's a ground up build so the tub will start straight, sound and solid as will the frame. Even though poly is less than half the price of OEM type rubber it's not really a factor for me, in the grand scheme of things is kind an insignificant cost.

[Burt4x4]

Yup, well ragg top....gave away my hardtop in 98
My K5 is mostly offroad only now..unless I'm herrassing my neighborhood or runing to the store..

[turp mcspray]

I ran topless as well. In the rocks, it flexed, and twisted plenty! Frames by themselves, are very flexy. I used the poly, thinking they would add some rigidity. These blazer tubs, even with all the extra body stiffeners, still move around a lot. I never saw any damage from the mounts. Plenty from rocks though! On my current frame off build, I went with poly again.

[swyfor5]

Got a poly set here ready to go in! Thank's for the Info guy's. Burt- good to see you post here-been a while-missed your input! Oh, I am going with my poly set soon!

[Burt4x4]

Wassup swayfor5
Workin livin workin livin ... you know the drill
Happy Friday!!
Burt

[MrGraySay]

Thanks for all the chatter on this subject, fellas. I'm looking at replacing all of mine with poly as well. Is there a specific brand you all have researched & would recommend?

[Burt4x4]

I buy all my poly from Energy Suspension via Summit Racing:
Black is better IMO =polygraphite
http://www.summitracing.com/search/b...rgy-suspension

[69-72]

I don't know about anyone else but the rubber mounts I put on mine from LMC started to look like the 40 year mounts that I replaced them within a year of installing them. All of them are all cracked and dried out looking.
Posted via Mobile Device

[ckato4477]

^from what I hear, most stuff from LMC is low quality, so it makes sense