I don't know exactly which car you have. If is is the Twin Spark, you have power steering, which has a faster ratio than non assisted, and therefore, a 330mm steering wheel makes a huge difference. Obviously it doesn't reduce the angle needed, but it reduces arm movement drastically. If you don't have PAS, you may still find Shankle in the US make a quick rack kit, but I don't know if it is still available.
The 75 is the carburettor version (Dellorto carbs), not the TS, but it does have a servo. The servo might be a retrofitted one, but I think Alfa sold the 75 with a factory retrofitted servo at that time -- meaning they just slapped it in there without much thought. A bigger steering wheel doesn't really help me since I would still need to change grip on the wheel to get enough lock.
What does the quick rack kit contain?
With regard to the torsion bars. Ride height reduction makes very little difference to the camber. The unequal length wishbones were engineered that way to maintain consistent geometry and reduce bump and roll steer. Again, uprated torsion bars are availble, but are expensive. Then again so is the RS Racing front dampers which have the assister springs on them, which are used in conjunction with the torsion bars. They need a fairly radical castor adjustment for the spring clearance in the top wishbone though.
The co-owner of the car has a full RSR kit (the Ron Simons kit, right?) lying around the garage somewhere (it went missing a few months ago) that we might want to fit, but as you point out, this is not exactly a cheap option. (If we knew where it was we might fit it next year, but before I make any expensive changes I need to strip the car down and do a critical inspection of all the load-bearing parts of the body. If I find faults that seem critical we're not going to bother spending too much money on it anyway).
You will have to have someone frabricate some new metalwork for the castor rod mounting in the inner wing. A good mechanic or panel beater should be sufficiently competent to do this. Make sure the rust is cut out, and not just plated though.
I have only given it a cursory inspection. The L-shaped bracket that is welded onto the wing seems to be more or less intact, but the bodywork seems to have rusted through. I figured I could cut out that piece of the body, make a replacement and weld it in myself, but if the bracket is a goner I probably need someone to create one for me.
What sort of metal thickness does the bodywork have here? 1mm? 1.25mm? (I have lots of 1mm and 1.25mm sheet metal lying around).
You can modify the mounts to do away with the cushion bush mountings. RS Racing supplies balljoint mountings which need inner wing metalwork modification, but these are them much less prone to rust, and maintain suspension geometry better whilst cornering and braking, and make the front feel more consistent, stable and responsive.
Hmm, someone suggested I replace the standard castor rods with 105 series balljoint rods. How do the modifications I have to make for 105-series balljoints compare to the modifications I need for mounting the RSR kit? (My thinking is that I try the 105 series rods in the short term, and then, when the RSR kit turns up again, we can try that on).
RS Racing also supplies uprated anti roll bars. Either 28mm or 30mm. They increase the bar stiffness by about 300-400%, I think. You will need to lower the front suspension and dial in a fair bit of negative camber for this to work though. The trouble is, when you increse front roll stiffness, you increase the car's tendancy to understeer. Extra camber can help this, but tyre wear will suffer.
Studying the pictures from a recent track-day it looks like I need significantly more negative camber anyway, and since the car is mainly for having fun, it doesn't really matter if the tyres are going to suffer. (That being said, we drove the car 450km to a track day last weekend, drove it on the track and then drove it 450km home again afterwards :-) ).
Firmer rear springs will be needed. Eibach is really just a little too soft, but Spax, Koni or AVO shold be better. The RS Racing 50 or 60 KG rear spring should work also (60 only for the 30mm bar, but the rear may become twitchy in the wet). You will need firm dampers to make any of this work. I would suggest adjustables such as Koni, Spax or AVO. In my opinion, the Bilsteins are not firm enough if you're looking for a setup to keep the car from rolling during cornering. The firmer the rear, the less negative camber you will need on the front. With any of the above, I would say your looking to lower the car 30-40mm and will need somewhere between 1.5 and 2.5 degrees of negative camber. I would use 30min or so of toe-in to sharpen up the steering also.
I'll let you think about that before going on further.
Thanks for your tips! I haven't really given the rear end much thought yet. There is so much to sort out at the front end. My guess is that I am going to spend a significant amount of time swearing over stuck torsion bars :-)