Poly bushes disintegrating?

[GTVeloce]

A few months ago I installed a set of poly bushes into the castor arms of my 75. Doing some engine bay work the other day and noticed chunks of red bush had fallen off. It appears the bush is disintegrating. It was in excellent condition when I installed them (they had previously done less than a 1000km on another car and then had been stored in box) with absolutely no signs of cracking or damage.

This is a daily driver that hasn't (sadly) seen any spirited driving so they haven't had a hard life of high heat. Has anyone else had this problem? I wasn't aware they should degrade with age (originally purchased in 2011).

[Colin Edwards]

Hi GTVeloce,

Have the bushes been exposed to some sort of aggressive solvent? 

I have personally experienced large scale failures of pink / red polyurethane rollers in my line of work.  This was a "grade" of poly formulated for its machining qualities.  NFG in this particular application.  A grade of polyurethane with excellent moulding properties was the replacement.  Are your bushes moulded or machined?

See below image of the purple moulded caster bushes on my 75.  About 13years old.

[bonno]

Hi GTVeloce
As Colin has indicated, the premature failure was mostly likely due to either mechanical and or chemical damage, as poly bushes are designed for the life of the vehicle. There is a good write up of poly versus rubber suspension bushes at the following link.
https://www.suspension.com/blog/rubber-v-polyurethane-suspension-bushings/

[GTVeloce]

The poly bushes that disintegrated had not been treated to any heat or chemicals and have spent most of their life in the garage waiting to go on a car!

Interestingly they are red so perhaps the same material Colin was referring to.

I spoke with Sebastion Mauceri who mentioned he was aware of some red bushes that didn't hold up. Anyway, he helped supply me with a new set so now I just need to fix the clutch first...

[V AR 164]

Hmmm very interesting topic.

I too have had similar issues with red poly bushes on the sway bar end links on my 93' Hilux. They were on the car when I bought it and noticed they had completely failed. They were ripped in half in some sections and chunks missing in others.

However, in my 164q, I installed blue Superpro poly bushes on the front lower control arms, sway bar end links and rear trailing arms 2 years ago. To this day they are still 100% intact and look brand new. Even after the front control arm poly bushes that have been exposed to numerous oil leaks, coolant leaks, heat and de-greasers they are still perfect.

The only red poly bush brand that comes to mind is Nolathane. Not sure if its the same brand as the red ones you and I mentioned but good chance it is. Anyways, I run Superpro for everything now and have no issues so that's what I would recommend.

Cheers, Andrew.

[GTVeloce]

I don't remember what brand they were. I bought them around 2010 and briefly installed them on my GTV. I felt they may have been transmitting too much NVH so swapped them out fairly quickly. They have since been sitting in a box in the garage till a few months ago when I needed a set of castor bushes for the 75. When I finally get around to remove them I'll take some snaps (clutch comes first...)

The replacements I have are Superpro.

[Colin Edwards]

Seem to recall local manufacturers adopted some sort of colour coding of polyurethane hardness.  Red / pink was Shore 90 - relatively hard.  We used this spec for friction wheel tyres - provided good traction / adhesion performance.  Manufactures proposed this material / duro given it was easy to machine.  The wheel tyre surface needed to be very smooth with around no more than 0.02mm run out!  The poly "tyre" is moulded to wheel then machined to a very specific diameter. 

The red / pink poly wheel tyres did not need to be resilient given they were lightly loaded.  Recall at least one manufacturer suggest this grade did not have the resilience of some of the softer grades.  Shore 90 is similar in "hardness" to skate board tyres.  Possibly a bit hard for suspension bushes?