924Board.org

[RC]

Am trying to see if its possible to use or adapt VW urethane rear trailing arm bushes to suit our cars. AFAIK the only options are the stock rubber ones ($100 + set) or the Elephant monoball ones, for $300.

The only trailing arms I have are happily sitting where they belong and I`m not keen on dismantling the rear suspension for a few measurements. These are what I`m talking about. I need the outer diameter of the bushes or the inner diameter of the hole in the arms. Also need the overall length of the installed bushes and/ or the inner width of the mounting bracket.



This is the elephant balls unit. If you haven`t fitted yours yet Dan, any chance of wrapping the calipers around them please?



Appreciate any input here.

[Min]

if you can't find anything appropriate I can probably fabricate something, either a mold for urethane bushings or bushings themselves.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

[RC]

Maybe that`ll be plan B then Min.

Knew the VW ones have a big through bolt and initially thought they were a direct swap with ours until Rasta pointed out that ours have a 12mm bore. Doh!

Well he sent me these VW type 1 bushes to experiment with. Hopefully the OD is the same and I can just make another bush or inner sleeve down to 12mm.



If it fits then perhaps you may be interested in turning up inner bushes? Good chance though they`ll just be more spare crap as you would think that another 24/44 owner had done this before.

[Rich H]

???

the bushes that go form the torsion bar carrier to the trailing arm?

I have a pair here from a UK supplier I bought then decided the old onees were OK. Came off e-bay IIRC Polybush.co.uk Cost £25 they are brand new, never fitted, yours for cost.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[ideola]

[RC]

Ta Rich. Thats now plan C, and looking like a distinct possibility.

Thought yours were black Dan, mistook them for elephant balls. Now realize I got thrown off track by the black & white & hard & soft comments in your other thread.



That`s them eh?
Know yours are for the ally arms and not positive of the interchangability on early steel ones. Some suppliers list 24/44/68 while others say 44/68?
Thanks for the measurements.
Would you mind just confirming the metal bush length?

Unfortunately the VW ones are smaller at 39mm OD. Inner flange to flange is 45mm and outer 57.4mm. Tube is 61mm long. Not a direct fit but hopefully a good possibility they will fit inside of the old stock steel casing, with the rubber removed. Easy to make more bushes or inserts to suit the 12mm ID.

Since I`m so much enjoying actually driving my car ATM am very reluctant to strip the suspension only to discover things don`t fit and I have to wait weeks for more parts. Know the feeling?

[Min]

*starts shopping on ebay for delrin bits*

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

[ideola]

[RC]

[ideola]

Sorry, I got rid of all the rubber bushes

I have about another week or so before I'll be assembling everything (have to wait 5 days for the hard nose paint to fully cure). Should I go ahead and post dimensions for everything???
_________________
erstwhile owner of just about every 924 variant ever made

[RC]

No worries Dan.

But you never know what might be under the bench in some garages.

Thanks to your measurements have sufficient info to get some metal inserts made. Feel that these red VW bushes should fit inside the OE casings. Since i`ve been wrong assuming things before would really like some confirmation before my car spends more weeks stuck on stands.

Sure that Min or anyone else considering making their own bushes would appreciate all dimensions though. It`s often uncommon tech data like this that can never be found by search when you need it, so would be useful to document it here for future.

[smither]

Ok here goes

Hole for the bush in trailing arm.
Diameter 37.2mm to 37.7mm (there are some ridges in mine of around 0.25mm in depth that appear to be original, must be there to grip the bush)
The total breadth of the hole is 47.9 mm.
The flage around the hole is 56.1mm in diameter.

The silent block removed in its uncompressed state.
ID of metal sleeve is 12.05 mm ( not sure about the extent of wear as i do not know the age of the it)
The metal sleeve's OD is 20.16mm.
The original silent block has a metal plate that forms the outward side this is 57.7mm in diameter.
The metal plate is 3mm thick and the metal plate plus the rubber flap around the edge of it is 8-9mm thick
The metal sleeve length measured form the inner side of the bush out to the metal plate is around 29.5mm but the plates on my bushes are a bit rusty so this mearsurement varied alot.
The width of the bush measured from the inner edge of the metal sleeve to the outer metal plate is around 29.87mm.
The rubber part of the bush is 38.94mm in diameter (again this is used and uncompressed)

The new urethane bush in its new uncompressed state.
ID of metal sleeve is 12.03mm.
OD of metal sleeve is 22.2mm.
The new bushes have a single metal sleeve rather that one set in each half of the bush.
The total length of the sleeve is 54.97mm making it considerably shorter than the metal parts of the old silent block.
No metal plate
Diameter of outer flap is 60mm.
The total width of the bush is 26.59mm.
The depth of the bush excluding the outer flap is 19.84mm.
The flap varies in thickness between 6.7 to 7.3mm.
The diameter of the inner part of the bush is 42.4mm.

I did these measurments with a set of digital calipers, i do not no the tolerance of them but looking at some of the measurments i got and the likely size someone would design to i would say the are accurate to around 0.25mm.
I will hopefully be getting the new bushes fitted on Friday (my vice is to small) so i will let you know how they fit. I will post some pictures when i figure out how to.
Hope this helps .

[RC]

That`s great info Smither, thank you.

Things are looking up for the VW part, same OD as your stock rubbers and an interference in the arm hole. Apparently then the steel arms (alleged VW part) have a nominal 37.5mm hole while the aluminium 924S, 944, 968? arms have a 42mm bore. Clearly not an interchangeable bush for them then.

Sorry that I didn`t understand what you mean here:

[smither]

The part of the bush that goes into the hole in the arm is 42.4mm. Which is alot bigger the the diameter of the hole.
So maybe the urethane bushes won't fit in the steel arms as they are actual listed for late 944/968. Never mind, i will still try to get them in and let you know how it goes. As the urethane bushes are shorter than the silent block they might squish to fit (we can alll dream), it's worth a go as the are useless to me otherwise even if i ruin them in the process.

[RC]

Your stock, and my VW urethane ones are only 1 - 1.5mm larger. Don`t like your chances of a good fit, if at all.

Maybe Rich H has BTDT?
Kind of explains why only some sellers list 924 along with 944 and 968 compatibility. What they REALLY MEAN is 924S.

Just a suggestion, before you stuff up your bushes contact the seller, explain the problem which I feel they know of anyway, and see if you can exchange them for some VW ones but keep the tubes you have with the 12mm bore?