track car suspension

[r lane]

Will attempt brevity; A 78 911 track car. Currently 24mm front and 31mm rear torsion bars. 1'' swaybars both ends. RSR struts and shocks, 161/160 front valving and 180/170 rear valving. Digressive is not noted so I assume they are not. The car feels very planted and stable, but I have no other reference as in experience in other cars. Because I have them, I feel I should at least try them. A pair of 34mm rear torsion bars and a pair of rear 934 valved shocks, 220/180. I have to think that is going to tighten up the back, meaning more oversteer, but maybe not as the rebound number may keep the inside tire better planted. Any experienced feedback down this road would be greatly appreciated. Not to confuse the above, but I have access to a set of RSR front struts, valved 220/100 and has a 19 mm spindle offset. Would like to understand valving comparisons. The first number is the strength of rebound I believe and the second number is compression. How would one compare 161/160 valving to 220/100. I realize this is not a black and white issue, but would like to hear some intel on this subject. Bob

[Bill Verburg]

Originally Posted by r lane

Will attempt brevity; A 78 911 track car. Currently 24mm front and 31mm rear torsion bars. 1'' swaybars both ends. RSR struts and shocks, 161/160 front valving and 180/170 rear valving. Digressive is not noted so I assume they are not. The car feels very planted and stable, but I have no other reference as in experience in other cars. Because I have them, I feel I should at least try them. A pair of 34mm rear torsion bars and a pair of rear 934 valved shocks, 220/180. I have to think that is going to tighten up the back, meaning more oversteer, but maybe not as the rebound number may keep the inside tire better planted. Any experienced feedback down this road would be greatly appreciated. Not to confuse the above, but I have access to a set of RSR front struts, valved 220/100 and has a 19 mm spindle offset. Would like to understand valving comparisons. The first number is the strength of rebound I believe and the second number is compression. How would one compare 161/160 valving to 220/100. I realize this is not a black and white issue, but would like to hear some intel on this subject. Bob

24/31 is just slightly less under steer than a stock 74 Carrera
24/34 is ~100% less under/more over

The shock damping mostly matters when the track isn't glass smooth, Turtles and such are where digressives shine

older oe RSR valving was 180/170 or optional 240/180 rear and 160/160 w/ optional 240/180 w/ 10mm raised spindles
too much damping makes the ride harsher aka increases ride frequency
, too little leads to porposing and odd vibrations

What you need depends on the track surface conditions

wheel/tire sets also have a large effect

[stownsen914]

If the car feels planted and stable, what would be the advantage of stiffening up the rear with 3 mm thicker torsions? From your description, I assume the car isn't understeering, squatting, or bottoming out? These are the things I'd want to address with heavier rear torsion bars.
Statistics and comparisons are a great way to find a starting setup. After that, you make changes based on what the car is actually doing / how it's feeling. What are you trying to fix?

[r lane]

Originally Posted by stownsen914

If the car feels planted and stable, what would be the advantage of stiffening up the rear with 3 mm thicker torsions? From your description, I assume the car isn't understeering, squatting, or bottoming out? These are the things I'd want to address with heavier rear torsion bars.
Statistics and comparisons are a great way to find a starting setup. After that, you make changes based on what the car is actually doing / how it's feeling. What are you trying to fix?

Not trying to fix anything as I get out of the car grinning, but is the setup as good as it can be. Only one way to find out and as a friend described as trial and terror. Just because you think it is performing wonderfully doesn't mean you can't make it better. You can make it worse as well and now you have learned something. And as Bill implied, tracks are not all the same and that effects the required setup. Can I go faster. Thanks as usual guys and keep the letters coming, Bob