Grey to Black
11-08-2016, 03:37 PM
#1
Grey to Black
Local track is going from traditional grey carpet to the new Black (CRC?) carpet.
What are they typical changes folks are making for this newer carpet (diff oil, shock oil, springs, etc).
I'll be running a VTA car on it.
Thanks for your help!
What are they typical changes folks are making for this newer carpet (diff oil, shock oil, springs, etc).
I'll be running a VTA car on it.
Thanks for your help!
11-08-2016, 06:53 PM
#5
Tech Fanatic
less front camber 1*
glue sidewalls
softer springs...for me around 13lbs/14lbs work great..
2.5 rear toe
turn down my D/R a little
glue sidewalls
softer springs...for me around 13lbs/14lbs work great..
2.5 rear toe
turn down my D/R a little
11-09-2016, 01:34 AM
#6
11-09-2016, 11:04 AM
#9
Tech Initiate
A little confused on why you would go softer on your springs? is so you tire isn't being "pushed" into the carpet as hard?
11-09-2016, 01:26 PM
#12
I won't go into a full, detailed engineering explanation but a spring's rate simply controls the amount the suspension deflects under cornering and longitudinal acceleration, and thus the body roll angle. The load on the wheel/tire is a function of static load, lateral g-force, wheel track, and CG. The lower the spring rate, the more the suspension deflects and the chassis rolls more. The higher the spring rate the less the suspension deflects and the chassis rolls less. The actual loads on the wheel/tire are virtually unchanged (for a comparable lateral g-force).
If you want the details, check out the book by Milliken & Milliken on Race Car Vehicle Dynamics. It is the bible of race car chassis engineering and analysis. It's only about 800 pages and chock full of complex mathematics...
11-09-2016, 01:35 PM
#13
On a related note, I have used data acquisition on my cars to measure vehicle speed, lateral and longitudinal acceleration, RPM. What I've found is that a USVTA car's maximum lateral g-force capability seems to be around 2.3g's before traction rolling, no matter which carpet the car is on. Again, a function of wheel track, CG height, and lateral g-force applied.
I was able to achieve this on both the gray and black CRC carpet, but as others have found the new carpet makes it easier to get there. I too have found that gluing the sidewalls helps, mostly on the front. My *theory* is that it stiffens the sidewalls of the tire, making the effective spring rate on that wheel higher and causing an understeer condition (if used on the front only) which stabilizes the car when it reaches the cornering limit. Reducing the steering angle seems to help as well, but I have a couple of theories on that...
I also found that increasing the droop front & rear seemed to reduce traction rolling on the black carpet. Perhaps letting the car roll more? This would also explain how going softer on the springs also works.
I was able to achieve this on both the gray and black CRC carpet, but as others have found the new carpet makes it easier to get there. I too have found that gluing the sidewalls helps, mostly on the front. My *theory* is that it stiffens the sidewalls of the tire, making the effective spring rate on that wheel higher and causing an understeer condition (if used on the front only) which stabilizes the car when it reaches the cornering limit. Reducing the steering angle seems to help as well, but I have a couple of theories on that...
I also found that increasing the droop front & rear seemed to reduce traction rolling on the black carpet. Perhaps letting the car roll more? This would also explain how going softer on the springs also works.