Author Topic: One for the experienced racers...  (Read 4661 times)

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105gta

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One for the experienced racers...
« on: March 26, 2014, 04:49:22 PM »
Hi all, long story short, I'm after some input from anyone who race's a fast transaxle car for info on under steer, trying to determine whether the inherent understeer in the TA cars is more an issue during the slower speed corners or the hi speed sweepers, all my experience with racing alfas was with 105's, I'm now building a 116 and considering potential items to address/be mindful of.
For a little more info consider a GTV6 track car, light weight, hi power, good geometry suspension, sticky tyres etc...  All the usual mods.
With the 105 I always struggled with rear end grip during the slow tight corners ( I mainly done hill climbs) and from what I can attain the 116 can generate much more rear end grip to the point of under steer, I am just curious if it's more prevelant at hi or low speeds...

Ben
1967 Giulia Sprint GT Veloce (WIP)
1985 GTV6 (WIP)

hammer

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Re: One for the experienced racers...
« Reply #1 on: March 26, 2014, 06:38:31 PM »
Ben,

I've found the transaxle cars to be superb through high speed sweepers. They tend to understeer through the tight stuff. You can dial this out to a certain extent with torsion bar & spring ratios as well as shock settings (sway bars to if you want to play with them as well) but if you want to totally eliminate slow speed understeer you'll probably end up compromising high speed rear grip. I'm no suspension/chassis expert but I've raced a couple of transaxle cars for the past 7 years now and these are my basic findings, having played with suspension set up quite a bit.

Have a chat with Vin Sharp in Melbourne or Richard Anderson in Brisbane if you want to upgrade bars, springs and shocks. Either of these guys can offer you expert advice and sell you the parts you'll need to handle well at high speed.

Cheers,

Brent

aggie57

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Re: One for the experienced racers...
« Reply #2 on: March 27, 2014, 08:44:52 AM »
Long time since I did this, but in essence my approach was to add toe in and some negative to the rear end; combined with sway bars and so on it reduced grip at the rear on turn in (what you want) but once the car settled into a corner rear grip was re-established so high speed stuff not affected. 

To use this approach though you need to consciously drive the car into corners and encourage the rear end to let go a little with confidence it will grip and hey-ho-off-we-go!!  Feels absolutely fantastic when you get it right.
Alister
14 Alfa's since 1977. 
Currently 1973 GTV 2000, a couple of Mercs and a '14 Beetle (yes, seriously......)
Gone......far to many to list

105gta

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Re: One for the experienced racers...
« Reply #3 on: March 27, 2014, 09:19:09 AM »
Thanks guys, this is the sort of info/feedback I'm after.
I really appreciate it.

Aggie, do you happen to recall approx how much toe in you run on the rear, I currently have 2deg neg camber and lowered roll centre on the rear but no toe in. I also have raised the front roll centre with big torsion bars/springs and revalved koni's. So far I'm happy with how it performs but want to be prepared for future moves.
Ben
1967 Giulia Sprint GT Veloce (WIP)
1985 GTV6 (WIP)

aggie57

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Re: One for the experienced racers...
« Reply #4 on: March 27, 2014, 03:42:02 PM »
Sorry Ben, can't recall exactly but I think it was only a couple of mm.   One car we did ourselves and the other I had Beninca's do it.

Great you have the negative, rear roll centre already.  Its a series of small changes isn't it, not one thing alone.

By "raised the front roll centre with big torsion bars..." do you mean you have extended uprights plus stiffer bars? 
Alister
14 Alfa's since 1977. 
Currently 1973 GTV 2000, a couple of Mercs and a '14 Beetle (yes, seriously......)
Gone......far to many to list

105gta

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Re: One for the experienced racers...
« Reply #5 on: March 27, 2014, 04:59:39 PM »
Aggie - Yes I have inverted lower ball joints and 29 mm bars at the moment...
Yes a lot of small steps as you say, the rear end mods made a lot of difference to the feel of the car, dedion mods include the roll centre, neg  camber, sz front pivot and rose jointed watts link including centre pivot.
Over all the car feels pretty good, just a few more things to tackle before I'm done with the main mods then it'll be the fun part of fine tuning everything to work harmoniously.

Ben
1967 Giulia Sprint GT Veloce (WIP)
1985 GTV6 (WIP)

aggie57

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Re: One for the experienced racers...
« Reply #6 on: March 28, 2014, 01:51:45 PM »
Sounds like a good setup - I'm envious!
Alister
14 Alfa's since 1977. 
Currently 1973 GTV 2000, a couple of Mercs and a '14 Beetle (yes, seriously......)
Gone......far to many to list

alfa duk

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Re: One for the experienced racers...
« Reply #7 on: April 01, 2014, 10:45:07 PM »
Ben
 No mention in the previous posts about front camber. This was a major turning point with the handling of my car as i originally had 2 degrees but after some discussions with an old bloke, he took the car and returned it with 4.5 degrees. It transformed the car to very little understeer under hard cornering but introduced slight oversteer, which with the v6, you can power out of it.  The only catch is in the wet. You really need to learn how to drive the set up. With the big camber, only a small amount of tyre is in contact with the road so you need to carry some speed through the corners to try and get as much of the tyre on the track. Doug
85 gtv6 dead, cant let go
84 gtv6 24 valve VRA spec
84 gtv6 andalusia
80 gtv group s