Alfa Romeo Owners Club of Australia Forum

Technical => 160 Series (90, 75, 164 Sedans) => Topic started by: GTV-074 on August 26, 2020, 11:27:33 PM

Title: Alfa 75 Rear Suspension Options.
Post by: GTV-074 on August 26, 2020, 11:27:33 PM

I'll be poking around the rear of the 75 in the near future to refresh the isostatic linkage setup, so whilst the rear is a little bit un-picked here & there
thought i might take the opportunity to refresh some of the rubber around the place.

Plan is to do the,
2 gearbox mounts (standard rubber)
Diff mount (standard rubber)
Shocker mounts (standard rubber, check spring rubbers while i'm there)

Now what is the collective thinking from the knowledgeable folk out there for the rest (car will be used for some spirited road use!),

A frame mount bush - poly or rubber?
Watts link bushes - poly or rubber?
Rear roll bar - poly or rubber?

If it matters, I'm hoping (he says looking to the heavens!) to do the work with the transaxle in situ (ie. just jack, lift, push, lower where i need to).

Any help, advice, gotchas would be appreciated.


Title: Re: Alfa 75 Rear Suspension Options.
Post by: Colin Edwards on August 27, 2020, 08:44:44 AM
Hi GTV-074,

I have "Powerflex Purple" polyurethane bushes fully throughout the rear suspension - A frame front bush, all Watts linkage bushes and all roll bar bushes.
Front end has full poly as well. 

Location of the A frame during cornering and managing roll-steer is critical, so number 1 for me would be Watts linkage, then front A frame bush and finally ARB. 
The 75 chassis is so good the front to rear balance can be tuned via combinations of rear ARB poly and rubber bushes. 

A decent set of adjustable dampers is definitely worth considering to fine tune handling / grip balance. 

Title: Re: Alfa 75 Rear Suspension Options.
Post by: GTV-074 on August 27, 2020, 12:13:27 PM
Thanks Colin...

Poly is much easier to fit too!

Will go with yellow konis all round... standard setting to start with and then adjust if necessary.


Title: Re: Alfa 75 Rear Suspension Options.
Post by: Colin Edwards on August 28, 2020, 08:06:10 AM
Appears my 75 had Konis installed not long after purchase by first owner - still have receipt!
These were set at around 66% hard front and 50% hard rear.

I fitted new Konis about 2 years ago using similar initial setting.  At the same time fitted 28.5mm Pace torsion bars and 29.5mm Alfaholics front anti-roll bar.
Played around with damper setting and arrived at 85% hard front 66% hard rear.

Title: Re: Alfa 75 Rear Suspension Options.
Post by: GTV-074 on August 28, 2020, 03:59:32 PM
I need to refresh all the rubber bits front & back as mentioned.

I had a 75 back 20+ years ago, when the car was 8 years young, this current car just feels loose compared to what i remember.

So gearchange needs a refresh and slowly work through suspension/mounts, anything rubber etc.

From what i've read, these cars are so individual in the sense that any mods  made are in the eye of the beholder so to speak.

But yes, i m guessing for now with the standard setup (I will upgrade ARB & TB bars later) i'll just go for what feels right , more tuning to come later.

Title: Re: Alfa 75 Rear Suspension Options.
Post by: GTVeloce on August 28, 2020, 08:20:31 PM
Don't go too crazy with poly bushes. Some places they work well and others not so well. Watts link they are great, caster arm they are great and ARB cushions sure but I wouldn't use them for shock absorber mounts, upper A arm mounts or ARB links. I haven't used them for the A frame bush so can't say with any authority however I did read some interesting perspective that suggesting not using them there either. The theory goes that bush is meant to twist as well as providing location. Rubber twists reasonably well but poly much less so and therefore the poly A frame bush is working against the forces rather than with them. I am keen to try the spherical ball instead. This allows great location but still allows perfect rotation (twist) as well.

Also, a new set of decent rear springs help significantly. There are a few options but King Springs make a reasonable (and reasonably cheap) spring for the 75 in standard and lowered height. I'd recommend the standard height for a 75 - lowered is fine for a GTV6 but it sits a bit too low for a 75 IMHO.

Also, if you are doing the gearbox mounts, have a good look at your rubber guibos (donuts). You will need to disconnect the rear at the least so a good time to replace any that need it. And check the hanger and centre bearing while you are there.
Title: Re: Alfa 75 Rear Suspension Options.
Post by: Colin Edwards on August 30, 2020, 02:57:25 PM
Hi GTVeloce,

New Koni yellows come complete with rubber bushes and associated hardware.  Make sense to use new rubber bushes.
I haven't had any issues with the poly bushes in my ARB drop links. 

Polyurethane replacement bushes for control arms are usually two or three piece assemblies typically forming a "plain" type bearing.  This poly "bearing" must be lubricated to eliminate stiction.  Copper based anti-seize or lithium based grease seams to work well.  The bush manufacturer usually includes grease in the kit.