This is why I hate Urethane

[TME_Steve]

Well this isn't technically a suspension post but it's more commonly used for suspension than anything else.

I'm robably going to get flamed for this but for those who don't know I hate urethane for most applications it's used for. Eg Engine mounts (as you can see below) and most suspension mounts. The exceptions are those which have very little lateral or vertical load and no twist apart from perpendicular to the mount.

For example, urethane mounts on our front upper wishbone where it bolts to the car I'd be OK with (hence they are still in my car). Swaybar D rubbers I'm OK with as well as there is not too much vertical load applied to them. However, lower control arms, no thanks.

The reason being Urethane deforms much more plastically (as opposed to elastically) than rubber, meaning it doesn't spring back properly. The problem is deformation of the mount over time (a relatively short time) and then things move like they shouldn't.

Anyway, I couldn't find just how old this rollstop was but it is certainly less than 3 years. And check it out! and that's without an engine in it so add another 5mm or so deflection with the engine hanging on, probably 10mm under load. The tailshaft was hanging mighty low I must say. Now that half my vibrations are gone, back to getting that SAYC diff angle correct....

 

[unclepaulie]

yeeesh! looks much worse then what you explained over the phone

 

[mills_88]

Fuck!!! Going to check mine out tomorrow.

 

[mookers]

Dumb question: if urethane does that, then why do they use it? Does it have some short term benefits?

 

[TME_Steve]

Its cheap in that its easy to mould into shape, its usually stiffer than rubber so until it distorts it feels like the suspension is better connected to the car, for the applications I dont mind it in, it is often better than rubber.

 

[naughtika]

that shows that design isn't made for our cars.. maybe a solid one?

 

[Scottie]

To me, that just looks like it has been subject to excessive heat. I haven't seen urethane melt/warp like that before from just general use.

 

[mookers]

http://en.wikipedia.org/wiki/Polyurethane

Damn, that's a lot of chemistry. My brain hurts now.

 

[TME_Steve]

Solid rubber would be the go, wish I had my lower control arms to show, they were similar

 

[CANDEE]

If that rollstopper is like that, what are the engine and transmission ones like? They should surely go before the roll-stopper as they should be taking the weight?

 

[TME_Steve]

Well the roll stopper takes a fair bit weight, esp under load, my front mount is solid rubber and looks perfect, yet to pull the urethane drivers side off....

 

[lathiat]

That's the rear rollstop


I had some polyurethane ones in my Magna, they didn't do anything like that - although were only maybe 9months old when i last got them out, and, were much much thicker than that sideways - and had no holes drilled. Also mine had metal built into the center where the bolt goes through. Seems like that mount was kinda badly designed to be.

but they do look heat effected.

 

[unclepaulie]

sikaflex mount it is then

 

[[TUFFTR]]

Just asking but does having the holes drilled in them also effect the longevity and rigidity of them? Every poly mount I've seen has been solid.

 

[naughtika]

Just asking but does having the holes drilled in them also effect the longevity and rigidity of them? Every poly mount I've seen has been solid.

I think it was put there to lessen the vibration..

also I think these were made for the NA SOHC 6G72 which were used on the USDM 3G eclipse..

 

[Size1]

I think that I may have this problem also, I am getting vibrations through the floor particularly when turning right on a decline. I haven't had a look yet but is where is this mount situated.

 

[TME_Steve]

The mount is almost in the centre of the car at the back of the engine....

 

[Size1]

Found a drawing for them. Was this the rear roll stop, transmission roll stop or front roll stop? It looks like the rear from the picture but I'm not sure. And can you just replace just the insert? Sorry for reviving an old thread.

 

[[TUFFTR]]

Touching base on what I asked before, I still reckon having holes drilled in them isn't helping the cause. You can see a fold line where it's sagged next to that bottom hole. I have never ever seen a poly mount go bad on 3000GT's. Guys love them, but they are solid poly, not this.
Steve, have you seen solid poly's go bad too?

 

[Size1]

Sorry I read the thread again and it says it is the rear. I plan to jack the car up over the Easter break to have a look.