Is there a suspension guru in the house?

[Si]

I've stripped my donor and am about to start bolting bits to the chassis, all I'm missing is suspension.

These are the specs I've been given:

Front: 16", 5 or 5.5" stroke, 275-325lbs spring
Rear: 15", 5 or 5.5" stroke, 275-325lbs spring

So, what should I go for (stroke/spring weight)?

The target build weight is 850-950kg (hopefully nearer to 850).
Weight distribution will be 50/50.
Power around 220bhp.

Intended for mild road use.

I've been quoted £400 from Damper Tech so far. Any other companies worth trying?

Thanks in advance,

Si.

[gareth08]

Hi Si
The longer the stroke the more travel you will get in the suspension but this is also goverened to a degree by rebound and damper settings (if there adjustable).
The spring rate (lbs) will be goverened by the weight of the car.What car is it your bulding.
The rears will be fairly standard in relation to what car your building,the fronts however will depend on what engine you are fitting,i.e bigger/heavier the engine the higher the spring rate.
As a pointer my sumo is running 280lb rears and 420lbs on the front with Gas spax 14 point adjustables all round but I do personally prefer a harder ride(no comments please).Im using a small block Ford.
Hope this is some help
Gareth

[dave]

Hi Si.
I'm not familiar with the Python kit but you should be able to get this info from the kit manufacturer as there are many factors which need to be taken into account when determining shock and spring lengths and spring rates.

[Si]

Gareth/Dave,

It is for a Python (weight etc is posted above). I've posted the recomended specs from RV Dynamics, which give me a range to work within depending on how I want it set up. I was just looking for some extra detail on the effects of the extremes of the range (spring weight/stroke).

My suspension setup experience is from racing dirt bikes but I'm not sure that translates to road cars.

My feeling is that I should run a heavier spring rate which will allow me to run with less static sag which will lower the ride height and a shorter stroke to keep some clearance at full compression. But I'm painfully aware that could be the opposite of what I should be doing for a road car?

[dave]

Si.
I would be tempted to go for the softer spring rate and the longer shock travel, you can shorten the stroke by adding additional bump stops if required.
If you are fitting adjustable dampers you can use the spring platform to alter ride height and the damping rate can be adjusted by a small screw, if the worst comes to the worst you may have to but another set of springs at about £15 each.
Good luck.
:tu

............Just my opinion.

[Si]

Hmmm... I'll have a ponder.

Is there any generic suspension setup info around?

Are there any general guidelines for static sag and race sag. For example on dirt bikes 100mm/25mm is a general rule of thumb for rear sag.

The two sag figures dictate the ride height on bikes. Does the same apply in the car world? It occurs to me that race sag may not even exist in the car world.

Sorry for being clueless.

[gareth08]

Hi Si
Dave is right with regards to softer spring and longer travel and if not for you then change springs but on the other hand if you want less static sag then you,ll need harder springs.
If i was in your position id go for longer stroke but use harder springs as you can adjust damp and rebound via the shocks and make springs harder by adjusting the spring platform.
Bike suspension does translate roughly to car so your not to far out with youre ideas.
As for info as Dave says get Python spec and adjust to suit your car etc.There was a company near me that did suspension but they have moved.I,ll see if I can find out were they moved to and see if I can get a number for you.
Hope this is of some help
gareth