Originally Posted by
30Tooth
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Originally Posted by
30Tooth
You're running out of shock travel, almost everyone does and some cars handle that situation better than others depending on the flex.
Right. I couldn't work out if the car was just bottoming out or I was running out of travel. I've tried using o-ring bump stops on the shock shafts to calm it down in the past; it didn't really help a lot but 'the problem' happened more gradually. Just measured the shocks on the car (front end)
Total travel off the car = 8.8mm (irrelevant as it's longer than when at full droop but it does mean the piston isn't resting at the bottom of the shock body)
Spring length at full droop = 20.25 mm (slightly compressed)
At ride height ready to go = 1.65mm compressed
Compression at max wheel travel = 6.43 mm
so total shock travel availble from ride height = 4.78 mm (pretty close to what you calculated!!)
Originally Posted by
30Tooth
The springs are too soft particularly the front ones let's do the math shall we?
Let's pick 2.6 xray springs which were tested to be 260gr per mm.
It's worse than that; all the springs I have measured are softer in the first half of their range, with the quoted rate being applicable at full compression (which will never be reached before runnin out of shock travel)
The springs I am currently running (3 racing white) measure C=2.35 N/mm at 4mm compression. I was, however using the outer hole on the front shock tower to make it a little stiffer.
Originally Posted by
30Tooth
The car weights 1350 and each wheel has 25% of the total weight, assuming common motion ratios and shock angle.
Each wheel has 337.5gr, motion ratio on the front is 0.55 and cosine of 35* shock angle is 0.82. 260x.55x0.82=approx. 117.3gr.mm wheel rate, 337.5/117.3=approx. 2.9mm of deflection at rest.
Being that on high grip tracks 2G are possible and this is the limit before traction roll, let's simplify calculations and say all the load of the inner tyres was transferred to the outside tyres, 337.5gr +337.5gr=675gr. The roll bar contributes with 25gm.mm so 117.3+25=142.3gr.mm during roll. 675/142.3=4.74mm shock travel used.
FYI here's the numbers from RC3 for this setup
I think that's even softer than you were basing your calculations on, or is it just the difference in units between grams and Newtons?