Race suspension question from a new Alfa driver

Alfa Romeo ONLY please!
Fortis621
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Post by Fortis621 » Thu Aug 18, 2005 11:10 am

Thanks for the informative technical discussion. I think I'll start with Mats' recommendation and go from there. I'll rely on your help as I get stuck (which I know I will). This is a great group. Thanks for your help everyone.
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MD
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Suspension

Post by MD » Thu Aug 18, 2005 1:56 pm

Yeah Mats, a discussion on racing dampers is the next progression. How about we give it a topic of its own to help with future searches for info? Most other key components have a slot of their own already I guess.
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Post by Zamani » Thu Aug 18, 2005 2:48 pm

Fortis,

Just to clarify, I had AVO coilovers with 125 lb/in springs AND the stock torsion bars. It helped to reduce roll, but it not enough for your race car I would think.

Now I'm just using 27.3mm torsion bars, koni sport shocks and stock 3.0 sway bar. Handles nicely.
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Maurizio
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Post by Maurizio » Thu Aug 18, 2005 11:01 pm

Numbers....

On my twin I'm using 600 lb/in + standard torsion bar in front and 400 lb/in in the back. And a huge 32mm hollow ar bar. In the back it probably could be a little less. There is one turn at the ring, when I get it right, lets the car step out 10 ~ 20 cm. I just liked the balance when I did add the 32mm ar bar and multiplied the original spring rates by 4 :lol:

@mats what kind of frequencies are you talking about?
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Post by Mats » Fri Aug 19, 2005 4:35 am

MD: The problem is I don't think any of us knows anything about shocks really, we know what feels good maybe but how would you set up a four-way adjustable coil over? ;)
I have no clue really.

Maurizio: Harmonic frequency in the front and rear suspension, this will tell you how "stiff" your car is in absolute terms i.e. we can compare any two cars and find out which one is sprung stiffer, spring rates is only comparable if you have exactly the same chassis ant the same weight over the axles...

There is a way to calculate frequency from wheel rate and axle weight, I'll see if I can dig something up.
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Post by Maurizio » Fri Aug 19, 2005 5:24 am

@Mats, ok thought it be something like that, but how are you going to measure\calculate the freuquency?
You need to determane unsprung weight (without dismanteling a car and a very difficult part is chassis stiffness).
And still the suspension setup is personal driving style related.

Shocks, is in my book also black voodoo magic.
Everybody wanted to sell an adjustable shock. And because I didn't want to become a pro in shock adjustment and spend the coming 10 years in adjusting my TS, I didn't go that route.

I was always charmed by the bilstein B6 shocks I had on my street 75 and spider. So contacted bilstein, gave them the guessed corner weights, spring rated and told them the car was for Nurburgring use. And they valved a coil-over front shock (to my desired dimensions) and re-valved my back B6 shocks.
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Post by Mats » Fri Aug 19, 2005 6:33 am

You can use axle weights for a reasonable approximation, you are probably not going to be able to calculate wheel rates perfectly anyway.
As I said, this is a good way to compare stiffness, I didn't say you could calculate the "perfect setup" backwards. :wink:

Bilstein B6? Whats the difference to the B46? Never seen the B6 I think.
Sounds like a good way to get shocks that are good (to get someone else to make them), costs too much here though, would be cheaper to get a set of fully adjustable coilovers with springs and everything. :?

Now, to get drunk...
See you after the weekend! :D
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Post by Maurizio » Fri Aug 19, 2005 6:49 am

Now, to get drunk... See you after the weekend! Very Happy
I'll have to stay another 30 min. :)
Banned.. ? ;-) Daily donky.. ==> BMW 118d Image
E36M3 (3.0) Ringtool :twisted: ==> definitely BANNED!

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Post by Maurizio » Tue Sep 06, 2005 5:59 am

Custom A-arms for coilovers without torsion bars and really ideal geometry however cost 2800 euros here in Holland (but you lose 22 kg!!!). Beautiful pieces of work but sooooooooooo expensive!

Have seen them last weekend on Zandvoort, they changed the connection A-arm - upright to a uniball. Which will move the upright up like a upside down ball joint and makes adjusting camber a breeze.
But what for me is a huge NO, is that they use a uniball for axial loads!! No uniball manufacturer will give you a number for maximum axial loads, only radial loads. Sorry got no pics camera was playing up....
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Post by Mats » Tue Sep 06, 2005 6:36 am

I know what you mean, but ususally you just over dimension the uniball and call it good.
It will take it and even if it won't you will probably feel it coming a mile away and be able to slow down/pit in.

Loads of race cars have done it that way. I bet thousands. Mine too. :)
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Post by Dennis » Tue Sep 06, 2005 11:33 pm

I'll have to dig in my archive, but I have a couple of pics of that suspension. Will post tomorrow..........
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