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how far is it below ground on a stock spider.( inchs, or cm )lets say a 1984 spider? thanks
 

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thanks.. but from what i read here a few years ago.. i thought it was below...
 

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If a line drawn from the lower ball joint center point to the lower a arm bushing is going donhill, there is a good chance the roll center is below ground. If that the same line is flat or going up hill the role center must be the above ground?
 

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oh...my... shock.:eek:.. horror..:eek:. a spot below msierts car:p
 

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You're about a half inch off. The geometric center of the ball joint is the center of the ball, not the lower side. besides, isn't it obvious that the arm slopes upward?

I see you have the spacers-between-the-arm-and-spring-pan version. Alfa also made a deeper spring pan for use on one side.

BTW - you should do this test, and other alignment measurements, with the driver's weight in the car.

Still a good looking and clean undercarriage!

Robert
 

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The picture reflects IAP sport springs that have been shimmed up about 3/4".

Without the shims I was scrapping the pan guard all the time. Now with them shimmed and going to 205/55/15's vs 205/50/15's I have never bottom out.
 

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For best front geometry, the lower arm should be parallel to the ground. Your inner end is about 10 mm too low. If you take the spacers between the spring pan and the arms out, you should just about get the perfect level on this side. Make a similar correction to the other (again with the driver's weight in the car).

Often when the car is lowered with aftermarket springs, the lower arm tilts the wrong way as yours is. You get some bump steer and a bit of adverse camber as the car loads in a corner. You can compensate for the adverse camber by adjusting more static negative camber (adj upper arms), but that makes the bump steer worse.

Then you get a bit twitchy in rough corners. That's not the right combination for a guy who's nervous about cornering anyway. Spruel, Alfaholics, and others make a drooped steering arm that will take out the bump steer. (You could get a faster - shorter - arm while you're at it).

But an easy step is to raise the front a bit to get the arms parallel. This may actually be faster in the corners by eliminating the twitchiness, allowing the driver to go FASTER. Getting the steering and F/R balance right is the best way to improve your lap times. I'd adjust F/R to get a bit of oversteer on hard throttle for my preferred corner exit, but you may be a bit nervous.

Robert
 

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Then you get a bit twitchy in rough corners. That's not the right combination for a guy who's nervous about cornering anyway.

Robert
I'm working on that..............I seem to relax and go faster when I'm chasing someone around the track for some reason. BTW I'm studying the race video........thanks for the help.
 

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It would be an extremely easy thing to work out by just taking a few measurements and then doing a 1/10th scale drawing (suggestion).

If I was to make a race car (and rules allowed) I would just lift the inner top pivot ... infact you could make the roll centre adjustable by having a few holes to choose from.

Heck I could modify my car now and nobody would ever know :D
Pete
 

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If I was to make a race car (and rules allowed) I would just lift the inner top pivot ... infact you could make the roll centre adjustable by having a few holes to choose from.
Lifting the inner top pivot will give you positive camber change in bump. That is the opposite of what you want.
 

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Lifting the inner top pivot will give you positive camber change in bump. That is the opposite of what you want.
Understood. I would have to draw it out but I am only thinking 10 to 20mm's, not huge. As long as the top arm angles downwards you will still get negative camber on bump.

Anyway my car will not be modified ... just "bench" pressing ;)
Pete
 

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If I was to make a race car (and rules allowed) I would just lift the inner top pivot ... infact you could make the roll centre adjustable by having a few holes to choose from.
As per Genericswood's comments: Why?
I have no experience with the 105 chassis, but after looking at the pretty pictures and reading what is written on Alfaholics website, increasing the camber gain on bump is a good thing for the 105 chassis (it is very beneficial on the 116 chassis too :D). What you are suggesting would ruin the camber curve, sending it totally the wrong way.
If you were able to lower the top suspension arm chassis pivot point, the roll centre height would be raised and the camber curve improved.
Raising the lower suspension arm chassis pivot point would achieve the same thing. I've seen pictures of that being done on coil spring equipped 116 chassis race cars on GTV6.com.
 

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Okay you guys are miss-understanding my comments. I'll further explain with a crude picture.

First of all it would be difficult on a 105 chassis to raise the inner bottom wishbone pivot, at least without somebody noticing ;). Raising the top wishbone inner would be a better and easier "cheat" that would be near impossible for a scrutineer to notice. Heck would only take you a few minutes, okay make it an hour if you welded up the old hole.

If you are racing in a class where you can lower the bottom wishbone outer ball joint, then that is what I would do, but if all ball joints have to be standard ... It all depends whether having a higher roll centre is better than the loss of negative camber on braking. Something a test session would probably be required to confirm. Remember nothing is perfect it is all about finding the best compromise that the er, rules, er, allow ;). Remember also that all later 105 series have the raised top outer ball joints already.

When a 105 series chassis is lowered the top wishbone ends up with a pretty aggressive angle, I believe (have not measured it) so it could come up a small amount without causing problems. See the red wishbone in my picture:
Pete
 

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I haven't done any measuring of the 105 chassis either, but from what I've seen, the distance between the chassis pivot points of the top and bottom control arms is greater the distance between the spindle/upright ball joints. So the basic, standard layout looks like the bottom diagram in that picture I posted.

Alfaholics do this for a reason :cool:
 

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If that is the case then my suggestion would most definitely not work (but the top wishbone I'm pretty sure does not angle up like your lowest picture, especially on lowered cars).

BTW: Alfaholics do the lower ball joint relocation because it gives the best of both worlds, ie. you do not loose your negative camber on braking AND you raise the roll centre. But not many race series will allow this.
Pete
 

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Well made drop spindles then :D Next to impossible to detect unless they really know what they're looking for.
Check out what Richard Jemeson has done for the 105, he even keeps the forging seam to help keep it looking standard :D
 

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Well made drop spindles then :D Next to impossible to detect unless they really know what they're looking for.
Check out what Richard Jemeson has done for the 105, he even keeps the forging seam to help keep it looking standard :D
:)

Pete
 
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