Suspension Gurus

[Chris L]

G'day all;

Looking for some advice on front suspension spring rates. This is what i know. Upper and lower wishbone setup similar to MGB V8 geometry from what Im led to believe, this is a GV Python round tube chassi circa 2000 model. Current shocks are Aldan, and they are at 22 degrees from top to bottom and 330mm extended length, travel is 70mm. The shocks are suspect and i have no clue as to the spring rate. Im going to get some QA1s in about 4 weeks. The engine is set back quite a bit and weight distribution is 50/50.

Any clues as to what springs I should be running. I do want to do some track days so that needs to be taken into account. The QA1s will be the double adjustable proma stars.

Thanks in advance
Chris L

[Rog246]

Chris I would go and get each corner of the car weighed, then go and speak ask what the suspension eggspurts reckon !
That way you have a real starting point IMHO
Rog

[Merv and Sharon]

Chris does it have a front sway bar? If so then softer rates are possible.

[Chris L]

Yes Merv, 22mm.

Chris L

[Rog246]

Chris just found thisink that should be very helpful to you.
Coil Spring Rate Calculator

hope it helps
Rog

[Merv and Sharon]

Chris I am no certainly expert, but most Cobras don't need massively high spring rates, particularly if there is a sway bar. The lower weight of the car makes that possible. For example a typical 'street' Cobra might have 300-350lbs at the front and 250-300 at the rear (remember that Falcons supposedly have spring rates less than 200lbs). For racing these might increase, depending on the shocks/sway bars used. Some are using 400-500lbs. If most of your driving is on the road then you don't want it to ride like a board. There was also an earlier thread that may help: Shocks and Spring Rates

[Rebel1]

Chris, send me a PM with your email and I'll send you an XLS file to calculate what springs you want based on all the info you seem to have. ie. Angles, weights etc.

You can choose a range of spring rates depending on your driving style.

[Mrs flatchat]

Chris L, go talk to George at Python he should be able to put you straight.
How stiff is the chassis, first priority -- then get a decent set of tyres
The suspension needs to be fairly compliant with good control form the shocks and front anti roll bar

[Gav]

I would go and see George, as Eve suggested.
He knows just how to make one of his cars handle.

[Tenrocca]

Be wary of any suggestion of a "standard" spring rate for a cobra. There are lot of variables at play - corner weights, un-sprung weights, shock mount points and angles etc, and each of these will vary from car to car. I run 425 front and 400 rear, and find the car is very comfortable on the street with a softer setting on the shocks (single adjustable qa1). Another cobra with a different set up and with those spring rates might find it hard as a rock.

[Gav]

The shock mounting angle is what makes the difference.
More angle will require a heavier spring.

[Chris L]

Thanks all for the suggestions, will take them all on board and Im sure will get a decent result. The rears are about right at 450lbs, have no issues there, but am just trying to get the fronts to be better, although it seems ok on the street, I just think it would not be much fun if really pushed . I would at the end of the day like to have the ability to "wind" it up at a track day and make some adjustments. Im thinking if I choose the correct shocks/springs and get the tyre pressures correct, I should have a window to make some adjustment.
While Im at it, 17" tyres at tire rack in the US, what do you advise for a track day say at Winton ( Shelbyfest).

Cheers and thanks

Chris

[Zedn]

Gday Chris,

Aldan colour code their springs so you can identify them. If you take out the spring and look on one of the ends you will find some coloured stripes. They have a chart on their website that allows you to identify the rates. Thats of course if they havnt worn off.

[Beejay]

Chris,

It depends on what class you want to run.

If in street class take a look at the Kumos and Hankook RSR.

Cheers,

Ben

[Tenrocca]

Chris - The Kumhos KU36 are probably the best "extreme performance" rating tyres you can get from tyrerack in the 17" size, unless you go for a R spec. I got some local last week - and it worked out cheaper then tyrerack.

[Gav]

Shame you haven't got an 'extreme performance' cobra to go with those tyres Andy.

[Tenrocca]

"Extreme" can mean many things, "extremely average" for example.

No one likes a smart arse Gav.

[Gav]

I don't believe everything I hear about you Andy.