The "Bad Rubber" anomaly

[GrUmPyBoDgEr]

The subject crops up time & again on these forums; "specialist" dealers warning us of dodgy "do-nuts" bushes etc. being unreliable & or having short service life due to the "modern rubber"
What are the "facts of life" on this?
When I think of the quality of tyres & coolant hoses that were available back then they were in no way comparable to the quality that we take for granted today.
I don't think that it is fair for these people to blame "modern rubber" for all of the problems but rather the choice of rubber that is used in our replacement parts.
Any specialists out there who can throw some light on the subject?

Cheers
john

[tdafforn]

Modern rubber is pretty good if my 10 year old renault is anything to go by.
No replacement bushes or pipes in its lifetime and it still handles and works fine!
Tim

[sebring]

most if my bad experiences with 'modern rubber' (and I have had several failures) is with engine, gearbox mounts and some seals, manufactureded for our older cars by small specialists (i.e. non OE parts). Unlike the large multi-national manufacturers, they cannot afford the H&S and environmental protection requirements associated with rubber production and thus use a less 'toxic mix'. The consequences for us is that the life expectancy and durability of such componts are far less; I have been told this by differing classic parts suppliers and there seems no way around it.
Buyer beware i suppose

[peterako]

My only experience with this has been the modern engine mount (Carb side) that lasted a whole 10 months.

Rubber came totally unstuck

I have now put in my old mount and time will tell....

Only changed my mounts because the engine underwent a rebuild last Christmas-ish.

In hindsight the new ones looked less well finished than the old ones.

Peter

[Roy Gillett]

I have posted these observations on other threads, and they are only hearsay, but reliable I believe.

My brother in law is a rubber chemist, ex head of the technical department at a leading rubber compounder. Following a donut failure after 5000 miles and an engine mounting failure after only four months, I asked his opinion.

His advice was that many environmentally nasty chemicals that used to be used in rubber compounding have been outlawed and cannot be used in any context. In many instances other chemicals can be substituted but there are real problems in getting rubber / metal bonding to work. It seems to me that most of the problems we experience are arround the bonding interface between rubber and metal.

Apparently for modern applications, components with a rubber metal interface are differently designed with much more physical interlocking between the components to make up for lower bonding forces.

Even so the B in L says that designing modern bonded components is a real headache and his company had a serious problem with a piece they supplied for Volvo.

So, modern bonded rubber parts are differently designed and the motor industry work to lower performance criteria for them. In general rubbers have improved apparently, but the bonding problem for older designs is an on-going issue.

So I am told!


Roy

[Frank Howard]

Rubber came totally unstuck

Peter,

As Roy explained, it sounds more like a bonding problem.

[RodMcIntyre1]

Hello all,
Would not the obvious solution to the modern rubber bonding problem be elimination of the rubber by substituting a modern flexible material like that used in suspension bushings, urethane I believe?
Cheers
Rod

[rocket]

Interesting idea Rod..i have a company that produces urethane components,they do pretty well everything better than rubber except..and this i feel is the big problem..they dont like high temperatures which seems to be involved in most motor vehicle applications.This said,ive often wondered how urethane doughnuts would perform?

[Jason1]

Hi

ive often wondered how urethane doughnuts would perform?

There was somebody on Ebay selling these sometime ago, there was a lot of talk on here about them. I have not seen them on there for sometime.

Jason

[redskatejbf]

As regards engine mounts and upper diff. mounts see the posting by CEEJAY- REFURBISHING UPPER DIFF. MOUNTS posted in the Elan forum March 6 , 2008. This concerned using Red PU 40 Lurethane for engine mounts etc. I googled PU 40 Lurethane and the supplier is in Australia I could not find a supplier in the U. K. You could not use this for doughnuts but it had been used with great success apparently on engine mounts.
Does anyone know off a supplier in its liquid form suitable for pouring / moulding in the U.K.
Regards John.

[rocket]

I work with various urethanes in different grades and hardnesses.I dont know of any available to be used outside of a suitable works premises due to health and safety.Maybe i should look into bonded urethane parts,i have produced suspension bushes etc with good results already.

[GrUmPyBoDgEr]

Hi Roy,

thanks for your informative post; sums it all up for me, this place is a mine of information

Cheers
John