Subframe mounts.....poly / OE ?

[John.]

I'm contemplating fitting poly bushes to the rear subframe of my coupe, subframe is awaiting the bushes which are sitting in the packet...….BUT, I'm trying to get my head round why the poly-bush crowd don't have a machined collar to replicate the contact area(where it meets the body) that the standard bush has ? From an engineering point of view, the poly bush is of a cheap design ?
The S/S sleeve if made like a top-hat shape would surely be better?

After doing my front subframe with poly's and having the bolts slacken I think due to the subframe shifting.....I'm thinking maybe OE is best?

[John.]

In the above pic it's clear to see the difference in contact area, poly bush metal insert sitting on top of old bush.....excuse the rust!

[steve briance]

Surprised to hear your front subframe moved!

[steve briance]

Annoyingly I seem to have lost most of my last reply. How is it that the first line posted but the next 20 lines or so vanished?

What I had said was about stretch bolts and reusing them (if you did) may have allowed the movement, especially if they had been reused before by a previous owner. They thin out a surprising amount when torqued several times.. .

In answer to your original question - for me it is poly bush every time just because I have never been able to fit factory bushes without destroying something! The last lot I tried to fit snapped some m12 threaded bar when trying to pull the bushes in with washers, nuts and serious torque.

[tango123]

I too have been told that trying to fit the oe bushes are a right pita.

[Lago Blue]

John.

Questions:

- Similar to the OE bush's steel core which appears proud of the rubber, could you sandwich a hardened washer on top of the pojy's SS core to get the footprint you seek?

- What is the current effective installed height of the OE bush steel core vs. the poly's? In other words, do the poly's leave room for a washer up top? If they don't does it matter?

- Are the radial markings inherent to the chassis boss or the OE bush?

- Are these mark-makers perhaps to help inhibit movement?

I too lost part of my response while typing this. I fat-fingered something in the bottom-left of the keyboard.

[piotr]

I have poly on front and rear subframe and I can't feel.they any better then old OE bushes I have replaced.the only advantage in my opinion is that they very easy to fit. as mentioned above when I was try to fit mine OE new bushes I ended up destroying two of them so I went for poly bushes.

[John.]

Regards bolts;- I think originals were used but then I fitted non-stretch type.

Didn't realise the OE bushes were a pain in the a*** to fit.....I do have access to a 100 ton press though!

Lago.....I have considered the washer idea. Haven't measured yet but suspect the height of the poly steel core will be same as the OE bush. The markings...… I don't have new (OE)bushes so can't say for sure but marks are on chassis too?.....they can only be there to prevent movement I think.

[willg54]

The bushes need to be chilled to fit, unless you can heat the subframe up too. They are a very heavy interference fit. The shear stress when fitting at room temperature will be huge!

Do the poly bushes not have a small plastic shim that fits on the top, similar to the wishbone bushes??

I went for the solid aluminium bushes. Get a bit of vibration at high rpm through the chassis, don't know if it's them for the aftermarket engine mounts.

[Mikes2]

I go for OEM every time. They can sometimes be a challenge to fit - just need to be careful.
I'm not convinced the bolts are stretch. Initial torque is nowhere close to what an M10 or M12 can take

[newsh]

Annoyingly I seem to have lost most of my last reply. How is it that the first line posted but the next 20 lines or so vanished?

Steve, if you post from Tapatalk and insert a phone emoji, the rest of the post will go missing. This is to do with this forum sw compatibility with Tapatalk as it doesn’t happen on others. I have learnt to not use emojis on S2 forum unless I type the bb code

[steve briance]

Thanks for that, I don't use tapatalk but think I did insert a phone emoji. It's good to know What happened so I can avoid doing it again! (forum emoji)

[John.]

……. They are a very heavy interference fit.

This is a concern if I fit poly.....'cause they just push in !?

[varia]

I used a wheel bearing puller set the subframe bushings

[steve briance]

That's interesting Varia, your polybushes look like o.e bushes but just in polyurethane? They look like they would need pressing in as much as the old rubber ones? My guess is the majority of poly users including me are; commenting how easy they are to fit are using 2 part items where they do fit by hand and then. You just push the steel Bush through the middle.