Dea_944t

Normally you would tighten the caster block-to-body bolts first and leave the M12 eccentric lock nut slightly loose and tighten it with the suspension loaded not to shear the rubber.

With spherical bearing caster blocks there's nothing to shear so I was thinking that it would be better to first tighten the M12 eccentric lock nut and then tighten the caster block-to-body bolts.
My idea was that this would avoid any unnecessary bending tension (or possible movement of the casterblock forward) in the caster block-to-body bolts when tightening the M12 lock nut.

Does this make any sense?

/Dea

kev951

always tighten no matter what the bushing is made out of when the suspension is at full droop, unless for some oddball reasons the instructions tell you specifically to do so. You can use a floor jack under the hub to compress the suspension easily. hope that helps

TonyG

First off... I hope you replace the front rubber bushings in the A arms with spherical as well be cause 1 without the other ain't gonna fix the problem.

And now is the time to do it since it's all apart.

As far as tightening the caster block goes... it doesn't matter because the caster block will probably be loosened up as well as the eccentric in the A arm when the car is aligned. But it makes no difference which is tightened up first.

And yes... make sure the wheels are off the ground when you do it.


TonyG

Grandpa#3

OK Gents, I need some education on the use of Spherical Bearing Caster Blocks and front A-arms Spherical Bushings. Will having both give a rougher ride? Question is why replace rear one without replacing the front rubber bushing? What problem would you run into? I am about to undertake this job is the reason for my questions. Thank you in advance for your time.

Cheers,
Larry

TonyG

Larry,

Each piece of rubber bushing you eliminate will cause more vibration and noise to be transmitted to the chassis. In the case of the caster block and the A arm bushing... replacing one will increase the nose and vibration by x. Replacing both will increase it by 2x.

The question is what is x?

With respect to the A arm bushings, x could be defined as "noticeable but not irritating" but will provide more feedback and steering feel. Likewise, the car will be far more stable under braking if you have big brakes and big sticky tires. The bigger the brakes and the stickier the tires, the bigger the difference.

This is really a track modification. On the street there is no benefit.

As far as replacing 1 instead of both (2).... there's no real point because you will have to align the car a second time when you replace the other busing, you already have everything apart now, ... and with 1 in place, you still have far too much unintentional movement in the suspension.


TonyG

Dea_944t

Not sure if you mean tighten at full droop or tighten with suspension compressed?
If I understood correctly the original rubber caster blocks should be tightened with the suspension compressed to avoid shearing the rubber.

I do it stepwise so first the caster blocks and next year the front bushings. I think that the caster blocks will make the biggest difference since they have a lot of rubber compared to the front bushings and a lot of rubber means a lot of movement.

Since I've removed only the caster blocks and done so without turning the eccentrics there will be no new alignment made.

I still think that if you tighten the caster block to body bolts first there will always be a bending tension in the caster block to body bolts since it should be impossible to push them forward with the same force thaht the lock nut will do when tightened

We seem to agree on the conclusion that when using spherical bearings it can be tightened at full droop.

/Dea

TonyG

The thread is about spherical caster blocks, not stock rubber caster blocks.


You either remove the rubber compliance in the suspension piece or you don't. You can't "half way" remove the flex.

That's like saying that my alignment will only be 1/2 way affected when I stand on the brakes....

It's up to you if you align the front end of the car.

I can tell you for sure that if you unbolt a stock caster block (never mind the slotted spherical bearing caster blocks....) you will not have the same caster and probably not the same toe as you did before.

The thread is about spherical caster blocks, not stock rubber caster blocks.



TonyG

theedge

Yes, ride will be rougher. Youll feel the road very will. Having either will effect the ride quality.

Rear one "can" have more rubber than the front one, and is easier to replace. If you have the stock/original caster block, its a big chunk of rubber. The 968 caster block is still a good upgrade in that case.

Replacing the front bushings is (to be optimistic) a major pain in the ***.

Dea_944t

The point of the thread was if there is any point in using a different procedure than for the original rubber caster blocks, that's why I'm referencing them.

I agree that changing both bushings would be the best but I still think changing the rear ones will give an improvement, this is also what I've been told by others that made the same change. There will be one less point in the front suspension that can flex so the unwanted movement will decrease.

I'll check the aligment to see if anything changed. The Porsche garage where I do the check had the experience that there would no or very small changes from this.

I was talking about the sphearical ones. For the stock ones this is not as important since the rubber will take up the movement to the front.
My thinking is that with the sphearical ones there is just metal to metal contact from the eccentric to the lock nut and there is a major risk that there will be stress put on either the bearing or the caster block to body bolts unless the lock nut is tightened first.

/Dea

Dea_944t

I was thinking that I'll do it at the same time as changing the outer joint which means that the Porsche garage will do it
If you have a suitable press it should be much easier but unfortunately I don't have one.

/Dea