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[feeutfo]

After some experimentation with basic poly alternatives, IMO, it's becoming clear that a proper poly ball joint is needed.

Having discussed this with Powerflex regarding their range of rearward wishbone bushes, it's also clear that none have a centre hole that meats the omegas 14mm diameter to accept the omega bolt size. I don't think a smaller bolt is wise. So while some designs could be modified slightly by fitting sleeves to space out the bush outer dia to 49mm. It's a non starter if the bolt won't fit through the hole.

Any ideas on a poly replacement?

Here are the oe dimensions from the Meyle web site.

Meyle rear wishbone bush
614 035 0010
Height 46 (to space out the subframe)
Inner diameter 14 (to take the bolt)
Outer diameter 49 (to press fit into the wishbone)

To add, from memory, the wishbone metal is 26mm deap.



Thanks to numerous members with various projects that have tried various lumps of poly solutions, but these don't offer enough control, giving odd steering sensations on the brakes at best.

It seems it really does need to be a ball joint design. But to find one that fits....

[aaronjb]

Something like this, some engineering may be required: http://cad.aurorabearing.com/viewitems/products-commercial-spherical-bearing-metric-units/s-spherical-bearings-metric-ptfe-liners-available-?

Though I'm not sure 32º of suspension travel is enough, without measuring bump-to-droop.. There's one with a 14mm bore, what's the OD of the standard bush?

Ride might be a bit harsh with just a spherical bearing in there, mind.

[VXL V6]

I'll watch this thread with interest.... But unless you can get someone to make something which can be easily and cheaply made (looking at the movement of the axis I think that's going to be difficult) and provide longetivity well in advance of the genuine GM article - ie lifetime like the front polys - then I think GM is the only sensible route.

[05omegav6]

Something like this, some engineering may be required: http://cad.aurorabearing.com/viewitems/products-commercial-spherical-bearing-metric-units/s-spherical-bearings-metric-ptfe-liners-available-?

Though I'm not sure 32º of suspension travel is enough, without measuring bump-to-droop.. There's one with a 14mm bore, what's the OD of the standard bush?

Ride might be a bit harsh with just a spherical bearing in there, mind.

Nice idea, but nothing on that list that is even close to fitting   very limited compliance as well

Adding a thick washer to the support bush of the Sierra bushes might help reduce the lateral give. Say a thickness of 4-6mm and a diameter of 30-32 mm.

The amount of lateral force that the rear bush has to deal with is quite impressive...

Just to add, this is clearly a trial and error process rather than a simple fix, so perhaps needs an structured testing regime.

[feeutfo]

Yes Aaron that's the general idea. The outside diameter is 49mm.

The oe bush has roughly a 4mm thick surround of rubber as a damper between the globe centre spacer and the outer shell. Say 8mm total accross the entire width , for argument sake.

To utilise the items in the link, two spacers would be required to 46mm to space out the subframe bracket, then a circular poly collar fitted to the outer shell to provide damping, this would have to fit within the 49mm diameter shell.

The ball joint itself will have to take massive lateral load, like the entire weight of the car, and not stick.

A big ask.

[feeutfo]

This is the closest design I can find. Sizes are off, bloody Amricans insist on using inches. And the centre bolts is drilled. Bugger that. Although lubrication is going to be needed.

http://www.4wheelparts.com/Fabrication-Tools/Flex-Joints.aspx?t_c=86&t_s=528&t_pt=101460&Manufacturer_PQ=Daystar

[feeutfo]

Plus, as said, not sure 20degrees of articulation is enough.

Also, looking at the diag,not sure but I think I'd like to see the red material/poly surround the ball further to stop it popping out. But that would restrict articulation further.

[feeutfo]

From the link for clarity

[feeutfo]

I wonder if we could use the poly parts and make the rest to omega sizes...?

[05omegav6]

Ooh... I wonder what the tooling costs would be to get a set made

[2woody]

yes - have looked at this in some detail and have come to the conclusion that a new wishbone with longitudinal bushes at front and rear is the only solution worthy of merit, BUT

your "floppy" vertical bushes are giving you quite a lot of improved handling by allowing the wishbone to move inwards at the rear under cornering. This in turn gives you some toe-in on the outer wheel, which is good !

I'd really need to do some serious calculation work on replacement vertical bushes before being convinced of their safety.

[feeutfo]

Hmmm, I presumed the only reason the rearward bush is vertical is to give yaw movement given the excessive play the front oe bush can give throughout its life?

Plus, if fitting a vertical rear poly bush, I wonder if the depth of bush needed to keep it from popping out, will physically fit between the subframe brackets without striking the subframe on full extension and compression...?
The wishbone metal is only 26mm deep. A ball joint poly bush may well need to protrude either side. Full extension may well see the bush outer diameter meat the subframe.

[05omegav6]

My next to steps are...

1. Replace the yellow bushes with the black ones. If negative performance then onto step 2.

2. If the black ones are supportive enough laterally,  but too stiff to allow the arm to move vertically, then I will remove the flanges from the black bushes and replace with the flanges from the yellow bush. This would give a composite bush with the upper and lower 10mm being the softer yellow compound, whilst the central 26mm within the arm being the much harder black compound. This should allow adequate suspension travel whilst restricting the horizontal movement which is causing the toe changes under load and the subsequent tyre scrub.

3. If all else fails, refit the GM rears.

[feeutfo]

An old thread but these work. £50 a wishbone from Volvo. Half hour a side to fit. Piece of Pee.

Ride is very firm on the c70 though. Mostly spring rates, but the the rubber bush depth around the circumference was about 3mm iirc.


http://oldsite.omegaowners.com/forum/YaBB.pl?num=1232197401/0

[Kevin Wood]

The situation is different on a shopping front wheel drive car, though. You have the forces from the driven axle to control so there isn't the luxury of allowing some "give" in the bushes to compensate for cornering, etc. or it'll torque steer all over the place.

What problem are we trying to solve with the original bushes? IME they have very much less "give" in them than the front bushes and, again IME, they don't seem to fail as quickly.