Spring rate for rear coilovers

[Wally]

Originally Posted by ricola

I used pro-tech dampers on my Phantom GTR, they were good and held up to the elements well. I can't remember the exact history but I think the Pro-tech owner was with one of the other companies and then left and set up on his own. The fact that they are relatively small and build to order to your exact specs cheaper than any competitors in ally rather than steel means they win hands down for me...

Can't argue with that! Good find!

[ricola]

Here are the pro-techs, more pics on my build thread...

[Wally]

Very purdy indeed!

What spring rate did you end up with and how will you set your torsion bars? (like i.e. 1 or 2 splines lower)

[ricola]

I set up the spring plate so it was level with the rebound stop on the chassis, this is with stock swing axle (ie shorter) torsion bars, not sure what that equates to in splines drop... The springs are 125lb/in. Without the coilovers, the stock bumpstops were just about to touch the chassis with the engine/trans in so with most of the weight at the back (no doors, roof or interior though). Will wait to see what adjustment it will all need once the car is built up again and if I need to adjust the spring rate, fine tuning should be easy enough with the coil-overs..

[Wally]

Good reasoning; I was figuring similarly low springs too, as in between 100 and 200 lbs when you're using the torsion bars as well. Curieus how it turns-out once your driving her ;-)

[evilC]

Does anyone have any corner weights for the Super? I was thinking to calculate some 'ideal' torsion bar/spring loads. This won't be a definitive answer but just to see a comparison between the empirical result and the seat of the pants one.

Clive

[Steve C]

Originally Posted by evilC

Does anyone have any corner weights for the Super? I was thinking to calculate some 'ideal' torsion bar/spring loads. This won't be a definitive answer but just to see a comparison between the empirical result and the seat of the pants one.

Clive

Hi

Could that be worked out with the front to rear weight split?

Steve

[Sandeep]

I was doing some calcs on the rear spring rate for my coilover installation and recall a value of 360 lbs/in.

2200 lbs with driver / fuel, 62 % rear bias, Max G of 1.5, 4" rear travel. I am not sure if this is in the ball park or not as I recall Pete with the '52 split having a rear rate of ~ 600 lbs/in, but the car has not been driven yet.

Sandeep

[evilC]

Originally Posted by Steve C

Hi

Could that be worked out with the front to rear weight split?

Steve

Yes, it could but I was never confident about the numbers. From the information that is available from various sources the actual values differ enough to throw doubt on the potential answers especially when you factor in the suspension frequencies for both road and track. Having actual corner weights would take the first variable/approximation out of the equation.

Clive

[Humble]

Here's the corner weights from my 1303 race car when it was still stock. Full tank, with spare, no driver.

Total 1931lbs.

LF 394 RF 409
LR 582 RR 546

Front 803 41.6%
Left 976 50.5%
Cross 991 51.3%

[ricola]

To add one into the mix, I used 300lb/in on my old speedster replica with 915 and EJ20 turbo, no torsion bars and that was a good stiffness for street use...

[ricola]

I never weighed my speedster but found that 300lb springs were good for it...

[owdlvr]

...pretty much the exact reason I posted before ordering springs. Based on this thread it "makes sense" but in my head it just seems so way completely off :P

"paging Clive to the red courtesy phone...Clive to the red courtesy phone."

:-)

-Dave

[evilC]

Originally Posted by owdlvr

...pretty much the exact reason I posted before ordering springs. Based on this thread it "makes sense" but in my head it just seems so way completely off :P

"paging Clive to the red courtesy phone...Clive to the red courtesy phone."

:-)

-Dave

Sorry for the delay folks - been busy.

Adding my sixpennyworth. I have Spax PSX progressives on the front of the '03 that I estimate are 100 - 130lb/in over the travel distance. On the back I have 23.5 P944 rear torsion bars that give around 10% extra stiffness over stock. Having run the motor for around 6 months now and 6,000mls on our country roads around here the spring rates are hard for normal road use but when pushed feel about right - I would hate to up the rates much more especially at the back. Looking back at the figures these rates concur with fast road car spec, which fortunately is where I expected to be.
The roads around here are very bumpy and I do have an issue with the exhaust bottoming out so I am pondering whether to increase the rear ride height. The wheels do follow the bumps really well especially the faster you go, which is very helpful as it only has a cooking 1600tp so is driven with a brick on the throttle.
The front end sticks uncannily well and when I push very hard the back begins to hop that I suspect is either a anti-roll bar or bump stop issue but that is the only time it unsticks. I initially dropped the roll centre of the front and you can certainly feel the initial bite on turn in but I want to soften the action so I will try the original roll centre over the hols.
All together I have I think produced a road rally car that is a softer suspended setting than tarmac rally and almost a gravel spec with a lowered stance. My interim conclusion is that its got the right spring/damper rates but some of the settings need playing with.

It would be wrong to criticise any other set up that is very different as it is all about getting what works for you in the arena you play in.

Clive

[Wally]

Originally Posted by evilC

It would be wrong to criticise any other set up that is very different as it is all about getting what works for you in the arena you play in.

Clive

I agree, but you know how it is...people want exact answers

It still wonders me how a 944 with the engine in the front runs the 23,5mm stock in the rear and how that can be an acceptable upgrade for a sporty beetle with the rear engine?

In line with your very true above remark: I run the 25,5mm 944 M030 (optional) torsion bars and still think they are too soft.