Notice the flanges are on the outboard sides - this keeps the OEM bushings from moving fore-aft



Here you can see the plastic outer sleeves. The are slick and somewhat brittle. They will break and then slide in the control arm bores. We destroyed the outer shell integrity pressing them out. These were still serviceable before we pressed them out.

 

Cliff
thanks for the explanations.

You should making these Delrin bushings for sale...
If there is no gap from the beginning that washer would be difficult to place.

I'll PM back to you regarding your "used" arms....

Thomas

 

Hello at all
new kit four upper arms V12VS for a DBS's friend...
here are pictures ...i think i will too add washers in each outside cavities to help...
new front bushings V12VS concept same as new rears V12VS

 

Believe it or not, you don't need a press to get the plastic sleeved bushing completely out, I use a small 1lbs ballpein hammer to tap them out in matter few seconds. Not at all tight..

 

When all you have is a press, everything looks like an interference fit in railroad proportions

Irish can you enlighten us on where the early bushings were failing. My understanding is the plastic was breaking. Was the break between the flange and the shell? Seems this would allow the shell to slide in the bore. Kind of like how we broke the flanges above.

x-chr

 

Hello
you said :
the 1.5mm gap should close when you fully torque it, trapping the inner sleeve
NO
there is still 1.5mm gap with new V12VS arms each sides !! see red arrow.
and with an small tire lever, without forcing, we make it move easily sideways !
the rubber is still too soft? even if it is stiffer than the old arms.
I'm thinking of adding precise washers in the recesses of the end caps...

Advices please ?
Thanks

 

here are my old bushings (70000kms)
completely cut all around the axis, through all lenght !!
so during braking and acceleration the upper arms moved 1.5mm to the right and 1.5mm to the left (in their housing)
and you can see the traces of contact !

it was on these road behaviour problems that Chris told me to change the upper arms
Thank you again!

I think all cars with kms/miles have these poor handling problems...
that's why Aston owners drive slowly...
LOL

 

Good, that was the information I was trying to get.

I would put in a precise washer as I scetched above - at least on the forward side (where the full outer rubber ring is).
My guess is that the bushing will "wander" over time and thus close the gap to the forward side (due to the braking forces).
That is what rubber somehow does over time, as is visible on my old bushings.

As for the material of the washer, I suggest either:
Some tough "plastic" like Delrin, in the case I would use round outer shape (dont know if you can machine a 1.5mm thick washer / or get a 1.5mm plate?) , or
Stainless steel, in that case I would make a squared shape (towards the inside), so the washer cant rotate and grind on the Aluminium chassis parts.

Thomas

PS: having seen your picture, Its probably better with 4 washers per arm.
However such fracture could also be the effect of pre-twist in the bushings (like bolting them down with the wheels in the air or not loosening them after lowering)

PPS: one can buy Delrin (POM) plates with 1.5mm or 2.0mm thickness! That probably solves the material question...

 

The reason for the space gap:

1. When braking, arms need to move to prevent NVM on road vehicles. If you don't care about NVM, remove bushing entirely and install your own custom Delrin or spherical.
2. For suspension, rubber bushing to flex for travel. The arm bushings are secured in place by center sleeve, arms are parallel to ground and the bushing flex needs to move up and down as suspension compresses or when fully extended on a service lift. If you slapped in a spacer to that gap, the arm bushing would now bind, causing arm to stay stuck/binded/locked and most probably send you into a wall as that vehicle corner will not unload when weight is removed.

So, it's not about filling or minimizing the gap on the stock bushing. That won't correct any suspension handling issues..if anything, you would be causing an issue of great concern. It's like running poorly designed polyurethane bushings, they touch the chassis/frame and bind the suspension arm from travelling. A correctly designed bushing/spherical/center sleeve will be secured between the chassis mounting tabs BUT not provide any binding with the mounting tabs when moving up and down through suspension range of travel.

 

Irish07,

thank you for your words of warning. It would indeed be dangerous if the washers would make the arms bind.
We have touched the issue of tolerances and binding in the discussions before.

However the idea here came out of the observation, that the forwardfacing stock bushing with the full rubber ring to carry the braking load
moved forward ("wandered") with age and the bushing thus was in permanent contact with the chassis anyhow.
So a washer placed in front of the forward facing bushing (with some gap for free arm movement) would eliminate the "wandering" of the bushing with age.

Thomas
.

 

However, with age..that plastic sleeved bushing will eventually jam the spacer/washer between the bushing and chassis tabs. I understand the logic, however it seems like a band-aid repair to stop the plastic sleeved bushing from walking. If I remember right, it's also the front-upper-rear bushing that walks out from braking. If you had a 1.5mm gap and decided to build a 1mm spacer leaving 0.5mm clearance, the front-upper-rear bushing will walk and reduce that 0.5mm to zero. To stop the arm from travelling forward and walking the rear bushing out, you would "theoretically" need to insert a spacer to both front faces, this will minimize bushing walk on braking. However, that would provide to much chassis contact and not allow arm to move freely with suspension travel. The same can be said about the rear suspension upper arms, they are also plastic sleeved and tend to walk out of the arm. Inserting these "spacers" to all 4-corners would handicap the vehicle handling ability once strung out to perform. Btw, this spacer this has already been experimented by Aston Martin for the DB7 models. Aston would insert these spacers to the lower suspension bushings. Nonetheless, the spacers would split from pressure and get pushed out.

 

Phil57DBS Thank you for pointing out the 1.5mm.

I thought we were talking about the gap between the inner sleeve and the chassis tabs. I assumed that was the gap Thomas was referring to. The inner sleeve should be clamped when fully torqued. This is why we have to loosen the control arm bolts when setting ride height and then re-clamping when the car is resting on its tires at the desired height.

In your picture you are saying the inner sleeve is no longer bonded to the bushing? If so, (curiously) do you have metal or plastic shells and has the car ever been lowered?

Irish sums it perfectly. We have three different levels of stiffness.

1) V12s arms - quiet and smooth, gains more control of contact patch (higher durometer rated bushings), lacks stiffness at the limit, performs beautifully for a dual purpose vehicle

2) Delrin bushings - increased NVH, increased wear, will not allow cross axis travel, requires fabrication, provides adequate stiffness at the limit.

3) Spherical bearings (AMR). high NVH, high wear, allows cross axis travel, plenty stiff, wonder what those are going to cost and how often you will need to replace bearings

I dug out our set of 12s arms this afternoon. It looks like one could safely run Delrin in the lower rears also, The upper rears utilize outboard cross axis joints so there should be no suspension bind running a solid bushing top and bottom.

If I am understanding Irish, under braking, the weight of the car is compressing the front bushing into the most forward mounting tab (1.5mm gap closes ). The rear inner sleeve is trapped with the bushing bonded to it, but there is not enough friction between the plastic shell and the rear bore of the arm so the arm walks down the rear plastic shell instead of the bushing deforming forward. I presume (over time) this destroys the shell, and or, the arm never resets to it's proper fore- aft location in the rear bore (constantly changing caster) . I assume metal shells provide enough friction in the bores such that both front and rear bushings deform forward, limiting forward movement of the arm.

Thomas - I have all four 12s arms.

chr

 

A good discussion. I never understood the original design intent.

Thank You

chr

 

A good discussion. I never understood the original design intent.
i agree...

Please where are Sphericals on OEM arms ?
or which OEM joints are already spherical or rigid?

i think
one on upper front arms
two on lower front arms
??
https://www.scuderiacarparts.com/par.../152/720/24327

one on upper rear arms
three on lower rear arms
two on 14
??
https://www.scuderiacarparts.com/par.../152/720/24329

to know where to work on the remaining rubber silentblocks...
thanks
Phil

 

Ball joints, 2 on front (1 upper) arm and one at the lower. None on the rear arms, all bushings. Unless you count the anti-roll bar end links.