Front end suspension/handling questions

[martym00se72]

OK, I will start with the disclaimer that I know very little about suspension geometry and even less about the intricacies for tuning it. So apologies in advance if these are exceedingly stupid questions.

These questions come about from reading posts in earlier threads and curiosity has beaten embarrassment at having to ask:

- Can someone please explain the differences between drop spindles and ball joint/knuckle risers?

- How do they separately impact on handling?

- Can they be used together (or is that stupid)?

- What are the relative costs of them?

- Who produces them for purchase?

- Do they just 'bolt in' or is there other stuff to be done at the same time?

- What else do I need to know about these things?

Cheers
Marty

[LukeC]

Not a stupid question at all. They basically do the same thing.

They do two things: Raise the roll centre of the front suspension to give less roll in cornering, and improve the way the tyre is presented to the road when the car does roll (i.e. More negative camber on compression (outer tyre in a corner) and more positive camber (inner tyre in a corner)) so the tyre retains good levels of grip and response. You have to realise that the Alfetta chassis was designed in the early 70's. It's not that it was a bad design... just is a compromise for mainly road use and is fairly simple by today's standards).

The two methods both effectively extend the length between the top and bottom ball joints. The "knuckle risers", or extended top ball joints are at the top and is the easiest way to effect this geometry change. Vin Sharp is the man to talk to here for price and source.

Extending the lower of the upright can be effected in two ways: Upside down ball joints installed into the lower control arms (these must be sourced from a vehicle that has suspension loaded in the correct manner). This requires someone who knows what they are doing. Or cutting and welding two uprights together to extend the upright below the stub axle. This also required someone who knows what they are doing. This in my mind is the superior method except that to use legally on the road would have to be certified by first a structural/metallurgical engineer that has tested the weld (probably by x-ray), and then by an Engineering signatory on the basic of the former certificate (if you will get an ES to actually sign off on it).

All three methods may introduce some bump steer if the steering arm location is not corrected (stiff springs will alleviate this tendency).

[Duk]

LukeC has given you nearly all you need to know about the 2 (well, 3) forms of changing the suspension geometry.

But I'll add, and it's something that tends to get a bit lost in the who/what/when/where/why of geometry changes.
Because the front roll centre height is higher, then there is less lateral weight transfer onto the outside front tyre, but that lateral weight transfer still occurs. So some of the weight that was initially poured onto the outside front tyre is now supported by the rear outside tyre. The rear of the car works very well and is under utilised, so this perfectly fine.

In addition, upside down bottom balljoints are a huge change in terms of how much the distance between the top and bottom balljoints is changed. This would result in a very agressive camber curve.

And there will definitely be bumpsteer problems with geometry changes.
Basically the outer tierod end needs to be moved in the direction that the balljoint was moved. So if you go with knuckle risers/long top balljoints, then the outer tierod end needs to go up.
Drop spindle or upside down bottom balljoint it's obviously down.
It does seam that moving the top balljoint up requires less movement of the outer tierod end. Which is good, because you can't really move the outer tierod ends much............ At all. 

However, spherical rod ends can be used as their centre line is also the pivot centre and lets you raise the outer tierod end enough to get rid of basically all of the bumpsteer from the PACE long top balljoints.

Before I took my 75 Potenziata off the road I added the PACE balljoints (but without any bumpsteer correction) and found them to be an excellent improvement to what I found to initially be a rather disappointing car. I also added some 105lb/in springs over the Koni adjustables at the same time, but these 2 simple changes gave excellent results for what they cost.

[julianB]

And my $0.02...
A dropped spindle is the best way to achieve the roll centre change with a lowered car, but isn't ideal on a road car (I personally don't like the idea of a welded piece in my front suspension when the surrounding piece is cast- unless you get the thing x rayed/tested).
The upside down ball joint is best left for a track car.
The knuckle riser achieves the same thing but I have heard of them failing as well.

The direction change and lack of understeer with my lowered front end and knuckle risers is just fantastic... IMO, there's no point lowering the car if you don't change the roll centre.
The front end falls over mid corner and no amount of camber I ever had made up for it.
With the knuckle risers, it changes direction like a cat on carpet.
You should definitely do it!

[GTVeloce]

As above. Attached is a picture of an extended upper ball joint from PACE eng. I found them fantastic in a lowered GTV with other goodies. This pair are going into a fairly stock 75 so will see if they make as big (or maybe bigger) difference.

A picture tells a thousand words and explains how these mount -pretty much just like a standard BJ. All that's missing from the pic is the two bolts with spacers that attach to the upper arm.

Haven't tried a dropped spindle yet so can't comment although I know Beninca's offer the service. Pricing? It is a little cheaper for the ball joints but neither are 'cheap'.