180 replies to this topic

[1984mini25]

Cheers. Here's one example of the impression that you're buying an OE quality part, which in my case completely failed before I'd even finished a light restoration.

 

http://www.minispare...MS.aspx|Back to

 

Mine are due for replacement as well. As much as I don't want to, I'm replacing mine for black poly items. The same of witch I've done with the upper bump stops.

[MontpellierVanMan]

Those droop-stop rubbers 2A467 are the ones I fitted a few months ago, bought from MiniSpares, as replacements for the ones I bought from Somerford about 5 years ago which failed before the car had ever been driven - the rubber block collapsed AND de-bonded from the support bracket. Does this mean that paying a "premium" price has got me no further ?

 

My particular concern with the rubbers parts is that the rubber-type used must have a considerable effect on damping and noise-insulation in applications such as the interfaces between the subframe and the shell (tear-drop rubbers at the lower-front, rear-support rubbers secured in the foot-well) and between the motor and the sub-frame (main engine rubbers).

 

If the manufacturers manage to *******-up so much of the more obvious functions of these parts, I have absolutely no faith in their choice of compound ; when I'm trying to look for a source of the occasional low-frequency rumble, like searching for something that might have got caught between the shell and the subframe (is that weld a bit proud ? did I drop a nut in there ? etc) it could just as well be that one of the rubbers has completely the wrong characteristics.

 

I suspect that none of the usual suspects actually has any qualified mechanical engineer working for them to define the specification of the parts they are trying to subcontract the manufacture of, and that it's just "copy this for us".

[tiger99]

The subframe mounting rubbers are indeed a serious problem. The toeboard mounts were always prone to fracture or de-bonding, even when genuine parts were used. I would advise always fitting a full solid mount kit, with toeboard reinforcement, and enjoy the improved handling, instead of messing about with doubtful rubbers. You will probably want to add some top quality sound insulation to the bulkhead and toeboard area to restore the noise level to its former level, or less.

 

At the back, poly bushes in all 4 subframe mounts will do the trick and don't have much effect on noise level, but again it is possible to add insulation to the rear floor area, boot and inside of heelboard if necessary.

 

But what about suspension bushes? The lower arms can, not very effectively in my opinion, be replaced by poly, but if you do that with the tie rods things become dangerous, with tie rods known to break due to fatigue fracture because the poly is not compressible. It is usual to use one poly each side, in front of the mount, and one rubber behind the mount to avoid the problem. Rose joints are not appropriate on a road car where some controlled amount of compliance is needed for a basic level of comfort. Also the rose jointed tie bar kits on the market are an amateurish design which is quite abominable as it substantially moves the pivot centre and gives partial trailing geometry to the lower arm, with castor change on bumps. I think a redesign of that area may be necessary...

 

Engine steadies could usefully use a rose joint at the engine end, but poly at the body or subframe end is too harsh and noisy. I am thinking hard about that one...

[69k1100]

Depends on the shore hardness of polyurethane used of course. It is a very versatile polymer but gets a bad rap largely due to little thought going into manufacturing.

[tiger99]

Yes, but regardless of its Shore hardness it probably does not compress well in an application like tie rod bushes. It might be better if it was foamed, but in this particular application I can't see how long life will be achieved along with the ability to flex as required. But I suspect that you know something that the bunch of rather clueless Mini spares suppliers don't. Please do tell us more.

 

I note that some exotica use fluid filled bushes, and the expensive way of doing it might be to use a small hollow toroid of poly filled with some suitable fluid. When deflected into a wedge shape, as they are, fluid would be displaced from the compressed edge to the expanded edge, allowing the required movement, while still being quite stiff in pure compression.

 

My long term view involves using a correctly positioned ball joint, sitting in a resilient cup, or maybe controlled by a stack of Belleville washers,  in a redesigned mounting lug, so that the articulation and compliance can be defined separately. For severe competition use you might be able to tolerate zero compliance. The key is to bite the bullet and accept that the subframe needs to be modified instead of faffing about with Rose joints which put the pivot in the wrong place, in the manner of the usual suspects.

[limby2000]

This must be a common issue, i fitted minispare knuckles to the top arms of my car 18 months ago, its still in a dry garage (not heated), ive not even got round to putting the hubs on so its not been under load, and last week noticed there both cracked around the edge. Can anyone recommend a better quality?.

[Dusky]

Maybe we should call this thread "Classic car aftermarket rubbers".
Had a bad experience on some Ford parts Today..

[1984mini25]

But what about suspension bushes? The lower arms can, not very effectively in my opinion, be replaced by poly, but if you do that with the tie rods things become dangerous, with tie rods known to break due to fatigue fracture because the poly is not compressible.

 

I keep hearing this, But I've been running mine around for the last 11 years with poly bushes on the lower arms and front tie rods without any problems whatsoever.

[Broomer]

But what about suspension bushes? The lower arms can, not very effectively in my opinion, be replaced by poly, but if you do that with the tie rods things become dangerous, with tie rods known to break due to fatigue fracture because the poly is not compressible.

 
I keep hearing this, But I've been running mine around for the last 11 years with poly bushes on the lower arms and front tie rods without any problems whatsoever.

My lower arms never caused any problem being poly, about 8 years, 3 open pit lane track days and about 6 mini action days with track time oh and a trip to the ring.

Tie rod bushes on the other hand in poly or rubber tend to be a standard one year serviceable item though if not more frequently.

[tiger99]

Or until you crash when a tie rod breaks without warning.

[1984mini25]

Or until you crash when a tie rod breaks without warning.

 

But try proving it was down to the bushes and not age/wear and tear.

[tiger99]

The standard steel tie rod is adequately rated and will not suffer fatigue failure unless it is encounters excessive bending loads. The tensile load due to hard braking is nowhere near its limit. If it breaks, the cause can relatively easily be determined by anyone who cares to investigate, including plod and the insurance company.

[Ethel]

Serious question - won't they bend first if they're subjected to a serious bending load ( i.e. beyond elastic)? I'd be more worried about the brackets on the subframe, but still suspect any plaggy or rubber bush would yield first.

[Broomer]

My thoughts exactly Ethel, basically unless your mini is identical to tigers he will find something to whine on about regardless of your opinion or experience.

Edited by Broomer, 01 September 2016 - 11:26 AM.

[Mini Manannán]

The word on the street is that Minispares  are sourcing all their rubber components from new suppliers now, fingers crossed they have a better than 6 months shelf life!