track suspension and reindex

[edh]

OK - I have just been on the phone to EMC

Their view is

The car should sit on the torsion bars, which should carry the weight of the car. The helper spring only really loads up as the car rolls.

He didn't want my car to re-index - thought it sounded OK as it was, although suggested KW spring rates were way too puny....

I'm going to take my car as it is setup now to Anglesey & see how it goes

 

[Hilux]

People concentrate on spring rates all the time but ARB`s are key

I ran adjustable Weltmeister ARB`s (set up by Promax) and it transformed the balance - M030`s are too soft for track in my view and you cant dial in/out oversteer.

 

[Neil Haughey]

That is almost certainly true. Ppl forget that 968 M030 bars are designed to run with spring rates around 200 lb/inch or so not 3 to 4 times that. The only reason why any of us have those bars is because the regs tell us to use Porsche parts. Given the supply problems first with M030 ARBs and now with wishbones there is a strong case to open this up to aftermarket parts, after all do they this in the states and over there much of the 944 racing is much more focused on tight regs and low costs than it is here. Its something I have never understood given that there is nothing to stop someone spending £5K+ on Ohlins yet we have to use factory ARBs.

 

[George Elliott]

anyone know the KW V3 spring rates, I have no experience of them but suspect they are quite soft - which I like for various reasons.

thanks

George
944t

 

[edh]

340 f / 285 r - according to big Dave...

I've got some 447 / 391 springs to go on

 

[Jonny944CS]

Cough ** From page 1 ** Cough []

ORIGINAL: Jonny944CS

ORIGINAL: nicksonmsport

if the coilovers are already a much higher spring rate than the torsion bars, do they take over altogether, or do the torsion bars increase the rate over the top of the coilovers?

The two different spring types run in parallel, therfore the total is found by adding the two spring rates together.

However, the springs do not mount directly to the wheel hub, therfore it is more instructive to calculate spring rate at the wheel using the suspension geometry.

Rough equivalent motion ratios for the 944 geometry are:
Front Spring = 0.93
Rear Helper Spring = 0.65 (not sure about the torsion bar - but there are published wheel rates for these)

So taking KW v3 as an example:

Front spring rate = 60N/mm
Front wheel rate = 60 * (0.93^2) = 51.9N/mm

Rear 25.5mm torsion bar wheel rate = 31N/mm
Rear helper spring rate = 50N/mm
Rear wheel rate = 31 + [50 * (0.65^2)] = 52.1N/mm

 

[George Elliott]

Jonny,
my sincere apologies, [8|]I actually read that with interest but you baffled my simple brain with motion ratio's and N/mm when I suppose I expected lb's/in compression loadings.

I guess like everything, there is more to it than meets the eye, the motion ratio is the "gearing" caused by the suspension compression geometry? Hmmmmmm

Thanks Ed, what are the units of your / Big Dave's figures?

thanks again, and I hope that cough improves...

George
944t

 

[Jonny944CS]

[]

I'm not good working in old money but I believe the conversion factor from lb/in to N/mm is 5.71.

KW springs have the rates marked on their coils, these are: 60N/mm front and 50N/mm rear, so 342lb/in front and 286lb/in rear.

My point is that you must to consider the wheel rates when upgrading and comparing axles.

Wheel rates for comparison:
- standard 944 Turbo ~ 20N/mm
- 86 Turbo cup and M030 968 Konis ~ 30 to 57N/mm (progressive rate)
- KW v3 ~ 52N/mm
- 87-on Turbo Cup Bilstiens ~ 58 to 63N/mm (progressive rate)
- GAZ ~ 69N/mm (standard) 85 to 140 N/mm ??? (race) [:-]

 

[Hilux]

ORIGINAL: Neil Haughey

That is almost certainly true. Ppl forget that 968 M030 bars are designed to run with spring rates around 200 lb/inch or so not 3 to 4 times that. The only reason why any of us have those bars is because the regs tell us to use Porsche parts. Given the supply problems first with M030 ARBs and now with wishbones there is a strong case to open this up to aftermarket parts, after all do they this in the states and over there much of the 944 racing is much more focused on tight regs and low costs than it is here. Its something I have never understood given that there is nothing to stop someone spending £5K+ on Ohlins yet we have to use factory ARBs.

Exactly Neil, odd but c`est la vie.

Firmer rates better controlled by the (more expensive adjustable) dampers is the trade off but not with standard M030. The standard M030 bars tend to shear the front links which shows that they are marginal anyway.