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Suspension Gurus !

Posted: Thu Dec 09, 2004 8:13 pm
by Murray
Please take a look at the first two photos and tell me what you see.I'm currently running Shankle 27mm front sway bars stock torsion bars and new Koni Yellows adjusted at about 50%.Rear is Shankle 25.? roll bars Shankle springs and Koni Yellows at 50%.Looks to me as if the inside front wheel is trying to lift ? This sickness I'm smitten with calls for constant improvement.Would larger torsion bars flatten the front end out? Coilovers are not an option as I don't want to change class.Perhaps I need to lose more weight ?

http://www.alfagtv6.com/bb/viewtopic.php?t=59

Posted: Thu Dec 09, 2004 11:38 pm
by otter
how fast are you taking the corner??

Posted: Fri Dec 10, 2004 1:00 am
by Mats
I see a rather nice GTV being driven like they should be. :)
Quite a lot of roll but you need to give us some more info.

Tyres? street stuff or slicks with threads (Yoko 032R or similar)?
What are the tracks like in the UK, smooth or bumpy?
Weight of car, power?

What do you use the car for? Is it a streetcar that you do some racing with or is it a serious racing car that you can't (legally) drive on the street? Looks like the latter because I can't see a rollcage and there is something that looks like an interior.

Forget shocks, they have nothing to do with roll.
Roll bars are for fine tuning, not as a substitute for springs.
Get the biggest torsion bars you can find and try to match them with a set of springs, can you change to 60mm springs in your class rule? That would help, much easier to find the right spring.
You can get it somewhat right by calculating frequncies for front and rear, the rear should be a little softer (lower frequency).
Make the car as low as you can according to your class rules or without bottoming out.

All this will of course destroy any type of street driving capabilities but if you want to be fast on the track...

Or just say "fukc it" and get a good set of tyres and adjust some angles on the chassis and drive it like you stole it without worrying about leaning over. :wink:
A good seat is always good and helps you relax, get one.

Posted: Fri Dec 10, 2004 2:27 am
by Micke
With that body roll you need -7 deg static camber....

What options do you consider realistic?

If coil overs are out then this would be my agenda:

1) lose weight as much as you can
2) Get stiffer torsion bars. The original ones are way too soft
3) When you install the torsion bars you can lower the car as well
4) Get rear springs to match the torsion bars
5) As you're at it adjust the wheel alignments

After getting through this you will discover a totally new car to drive.

Posted: Fri Dec 10, 2004 6:51 am
by Greg Gordon
Hi Murray,
Your inside front tire is trying to lift off the planet. This is common on cars with stock torsion bars a big sway bar and good tires. The only real fix is to stiffen the front suspension with stiffer torsion bars of a coil over set up.
That said, your car looks really great going around corners!

Posted: Fri Dec 10, 2004 11:28 am
by Jim K
Murray,
I went through the same questions years ago. If you want a short answer list, read Micke's pointers twice!
Jim K.

Posted: Fri Dec 10, 2004 5:07 pm
by Zamani
My opinion, don't lower the front too much such that the relative angles of the double a-arm cause you to lose camber in a turn. Don't make the rear too stiff, or else you will start sliding more. Although some actually like this, I don't.

Posted: Sat Dec 11, 2004 2:29 am
by Mats
you can't really lose camber in a turn by just lowering the car, the camber-gain curve is somewhat constant as long as the legths and mounting points are the same.
You will however get bump steer (and therefore roll steer)

Posted: Sat Dec 11, 2004 8:19 am
by Murray
Thanks for all the solid comments guys ! I use this Alfa on the street as well so I'll be conservative.I think I'll start with one size larger torsion bar.All in all I'm very pleased with this car's handling and probably being able to unload the inner front a bit is just a reflection of how well this machine is sticking to the track.My racing is just for fun and I'm sure I can realize far greater reductions in lap times by improving the quality of the device installed in the driver's seat.I'm probably not even using 75% of this car's capability with its existing setup !

Posted: Sat Dec 11, 2004 10:34 am
by Barry
:?: Murray,What kind of speed were you carrying through this corner??Describe the type of corner if you would.What is your entry speed approx.??

I must be honest when I say that for a reletivly stock setup your car looks very good through here.How was your turn in,mid corner and exit(apex)attitude of the car??(Understeer,4 wheel drift,oversteer etc)

The unloaded front wheel has a lot to go before lifting at all.I believe that you will understeer before lifting any wheels.

Barry

Posted: Sat Dec 11, 2004 12:47 pm
by Murray
Barry I would have to guesstimate the speed at about 50mph (80kmh.) I rarely get to look at the speedo on the track! My car is very neutral and to produce oversteer I really have to get on the gas or be going too quickly going in.I haven't been able to provoke understeer.I guess I could generally state that if she slides it's all 4 wheels.

Posted: Sun Dec 12, 2004 5:23 am
by Barry
Murray,Thats good stuff!! The only "STOCK" type car Ive been able to 4 w,drift was my P 944 .It says a lot for your current setup,very good.To up the ante know you must try to maintain this balance front and rear.
Unfortunately its not always this simple.You mentioned that mods might force you into a higher catagory.What are the rule limitations?
If the rule is no removal of the original suspension or something similar,add the coilovers and retain the torsions.An idea,some people like to twist the rules without breaking them,others are worried about "sportsmanship"and the like....

Can you post the regs for your class or mail them to me??

btw,was the vette any better or quicker than you through the corners???

Would the class jump be viable without modding your engine or is the opposition to stiff??

Barry

Posted: Sun Dec 12, 2004 10:01 am
by Murray
Barry the Vette is behind me only because he's not allowed passing in the turns (Rules for SOLO 1 lapping sessions) I'm sure he blew by me coming out of the turn-oh well I get better fuel economy than him !
I'm going to stick with larger torsion bars for now as the rulebook would bump me up a notch with anything more serious and my 20 year old car is not ready for WRX s-nor is my 50 year-old brain !The previous owner of this car basically set it up per the European Car Mag.instructions and I guess that works pretty well.

Posted: Wed Dec 15, 2004 11:02 am
by Barry
Murray,I thought the thread had died a sudden death,but then I thought about your brakes!!This is a cheap and easy way of getting better lap times on any car.Im sure many club racers have dived inside and taken position because of good brakes.What do the reg`s` say??

Barry

Posted: Wed Dec 15, 2004 11:24 am
by Murray
Barry same story there only pads can be non-OEM and its amazing how observant and knowlegable the inspectors are,even for a car like mine which they've never seen in real life.You are absolutely right about being able to minimize your braking zone.I run Porterfield R4 pads on all 4 wheels and keep my brakes in tip-top shape.All in all I'm very pleased with the Alfa brakes particularly their ability to maintain stopping power and modulation throughout a long hot day on the track.Nevertheless increased braking power would knock seconds off every lap.