CSR Front suspension set up

[Hanns Per]

when setting up the front suspension of the CSR I wonder how push rod and adjustable damper springs relate to each other.

to increase ride height do I make the push rod longer or do I adjst the damper springs? What do I have to watch out for?

Thanks

HPK

 

HPK

[paul jacobs]

That's a very good point I suppose that in fact it doesn't matter which one you adjust, probably the pushrod will be the easiest to turn. Email the factory and see what they say, but if you could post the reply here it would help the rest of us

 

Paul J. Hard work never killed anyone ........ but why take the chance! New CSR now finished & running, awaiting SVA.

[Jason Plato]

normally adjust the pushrod , otherwise you will be increasing the preload on the spring.

[I.Mupferit]

I know it is not the same design but I guess the same principle applies. On my Freestyle pushrod suspension, Gary adjusted the pushrods rather than the spring seats to adjust ride height, I imagine for the reasons Dave suggests.

 

Brent

 

2.3 DURATEC SV Reassuringly Expensive

R 417.39 😬

[Neill Anderson]

I am not a CSR expert but do have experience with other pushrod suspension systems.

Most rocker systems have an inherent non linearity in the rocker ratio such that the damper travel for say 10mm wheel travel is greater nearer the bump end of the damper than the droop end, this is how they achieve rising rate.

 

The amount of rising rate can be quite a lot. Consequently it is normal to set the damper lengths (bolt centre to bolt centre) equal side to side to ensure that the rocker geometry is consistent side to side. Ride height and thus corner weight is set via the pushrod length and you can iterate around if you then decide that the amount of damper stroke is not correct ether side of your initial chosen damper length.

 

Of course it is easier if you know the initial (ideal?) damper length and the amount of non linearity in the rocker installation. Use of top quality springs also helps a great deal.

 

To measure the ratio changes simply plot a graph of vertical wheel rim travel (say 10mm increments) against measured damper shaft travel. Be aware that the effective rate of the spring (damper mounted) at the wheel is related by the square of the rocker ratio, i.e. if the damper moves only ½ of the wheel travel then the effective spring rate at the wheel (wheelrate) will be ¼ of the marked spring rate. The rocker ratio also affects the damper rate at the wheel and also possibly overall roll stiffness.

 

Regards

Neill

 

[paul jacobs]

So...........not as simple as it looks then Thanks Neill, it's good to have technical input, it kinda made sense the third time of reading - slowly.

[Neill Anderson]

It's not too bad to visualise in 2 dimensions, gets very difficult without a computer model or excellent drawing skills in 3D

If you are really keen simply make a stick model from ice looly sticks and drawing pins around half or full scale and then it is quite easy to see how things react.

I am sure we all have better things to do however!!

Neill

[Hanns Per]

Thanks so much. If I understood it correct then I should not touch the preload on the dampers for adjusting the ground clearance. Makes sense to me.

Damper adjustment impacts the work of the dampers/springs. So dampers correlate to corner weight and the rear suspension.

Since I have push rods I can adjust ground clearance with the push rods.

However I have to adjust ground clearance on the rear suspension with damper preload?!

 

HPK

[Neill Anderson]

The corner weight is ultimately determined by spring compression, whether directly by the platforms as at the rear, or indirectly by the length of the pushrod (combined with equal side to side) platforms at the front.

As Dave J has pointed out, if there exists a mass imbalance then all you can do by corner weighting is average it out as best as you see fit, albeit (technically) at the expense of the ride heights perhaps no longer being equal.

In general most strive for fairly equal front weights for a driver and half race fuel load within a few kg.

However remember to remove as much friction as poss when you do it, ie slacken all dampers to full soft and disconnect all anti roll bars. Once weighted etc then connect the roll bar links ensuring they are adjusted for a perfect fit (driver mass still present etc). Then re adjust dampers.

Also ensure that you lock the steering straight ahead, the combined geometry of castor and KPI and scrub radius means vertical jacking with steer input which of course affects the corner weights.

Best of luck

Neill