ALFAGTV6.COM

[ar4me]

I want to do it as simple and cheap as possible, so I thought of torsion bar coilover combo.

Jes,
From what i rouglhy measured (It's really cold out there, so is my garage ) Drop for 15" rims including flex clearence is around 4,3 cm. Cost wise (exchange rate) I don't know if it's worth, if I can buy new fully adjustable coliovers for around 320$ Too bad i bought PS3 four weeks ago

4.3 cm sounds like a lot. That is more than mine - I doubt you can fit that in 15" rims. With 15" rims you should have roughly 1" (about 2.5 cm) less than me, although rim design will vary and influence the exact number.
Jes

[kevin]

Pete, on my race car using 15 ''rims and the RS set up i dont even worry about the minimal camber gain i get as my travel in suspension in bump is 25-30mm max and i run at 2.5 deg to start off with.Maybe i am wrong here - comments?

[ar4me]

The value of drop spindles is that you don't screw up your front geometry as you do when you have the lower A-arm pointing upwards (in order to lower front end). This is unrelated to suspension travel. They change the roll-center (compared to a car with stock spindles and same ride height), moving it up, and hereby reduce roll.
Jes

[Duk]

The value of drop spindles is that you don't screw up your front geometry as you do when you have the lower A-arm pointing upwards (in order to lower front end). This is unrelated to suspension travel. They change the roll-center (compared to a car with stock spindles and same ride height), moving it up, and hereby reduce roll.
Jes

Not to mention the improved camber gain on compression to further help reduce understeer.
So many good points that eliminate the minor bad points (cost and slight increase in unsprung weight).

[kevin]

Jes, Duk, I know that the objective is to minimise the the distance between the cg and roll centre as this reduces your roll angle that’s why most people try raise roll centres (to a limit though). Taking into consideration that my suspension travel is 30mm bump and 20mm down there is a vast difference to a car that has 100mm in bump which most people are designing around. My roll centre at the moment is nearly level with the tarmac at the moment due to the low profile slicks on my 15 inch rims . My point is in my case (not 17’’ rims) I don’t get a big variation in roll centre height thus I get my consistency in handling. If I was using 16 or 17 rims I would drop spindles and I was using up to 100mm of travel in bump and rebound. This would put this car in road track catergory with that much travel. My problem now is my tyres are doing all the work and obviously not lasting. Its not that I am against dropped spindles as I am making a set now for my road GTV 3.2 with 17” rims as the geometry is seriously bad.
Please shoot me down if this totally incorrect as I am here to learn from you chaps.

Questions
1) Where is the optimin roll center height and how much is the max it can vary before the handling becomes totally unpredictable
2) This leads to how much travel (bump, rebound) should you have for full race set up , fast road track day set up.
3) What is max spring rate kg for track front and rear, and for road track day.

[ar4me]

With drop spindles you can run a softer suspension, and yet control roll. If you have lowered front with stock spindles you may need very stiff front suspension to control roll. Very stiff suspension can cause problems with traction if the surface is not super smooth, i.e. somewhat bumpy in places. Drop spindles basically give you some more flexibility in setup, in some sense. My main reason for the drop spindles is that I want to be able to soften the suspension.
Jes

[Zamani]

Jes,

How about a lowered pivot point for the watts linkage mount? That was a recommendation from Beninca. Not too low, maybe the pivot is moved into the middle of the dedion.

[ar4me]

Yes, I have been thinking about that too, but I need to figure out how much lower. Just installed the rear race coil-overs from Ron yesterday - doing many changes to the 3.7... I may have to pull engine to modify sump (in order to allow perfect alignment of engine and transaxle) - we'll see...
Jes

[grant]

AE86 use the same method to lower the RC on the rear axle. I'm going to pick up a new "stud" for that purpose from a local dealer and compare it to my spare Dedion and see if the OD of the shaft is the same as the watt's linkage for Alfas. If it is, it should be easier/cheaper to do the mod..