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10-23-2021, 03:52 PM | #23 | |
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It seems to take into consideration Track width, sway bar arm lengths, motion ratios for sway bar/damper/spring. https://www.fatcatmotorsports.com/FC..._M3_Online.htm I do find it hard to believe the FRC for a E46 m3 is 68% and then E9x to be in the 50s? That doesn't seem to make sense. I'm not saying my numbers are accurate either but E9xM FRC lower than E46 doesn't make sense to me.
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10-23-2021, 04:00 PM | #24 | |
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Also, comparing stock FRC between cars, are even just to see what they are stock, is completely useless - this coming from someone whos spent hours upon hours of doing so. What are you trying to accomplish finding the E9X stock FRC? |
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10-23-2021, 04:15 PM | #25 | |
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Formulas I'm seeing: wheel rate = spring wheel rate + ARB wheel rate Axle Chassis roll stiff ness = (Trackwidth)^2 x (Combined Wheel rate) / (2 x (360/Pi)) Front Roll Couple = Front Chassis roll stiffness / Rear Chassis Roll Stiffness This is omitting the bumpstop itself as well. I'm trying to get as best of a spreadsheet to identify flat ride + a decent FRC to experiment. If my math is completely off to yours and I'm unclear which is correct, that leaves me with a very poor base to go on.
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10-23-2021, 04:58 PM | #26 | |
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The numbers look slightly different then what I'm using. I linked the spreadsheet I use above. You could punch in the same numbers to both and see how they compare. I've found this one to be accurate. |
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10-23-2021, 06:04 PM | #27 | |
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10-23-2021, 06:07 PM | #28 | |
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Good luck! |
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10-23-2021, 06:14 PM | #29 |
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On FRC%: I think the point isn’t so much the number itself; it’s more about comparison, e.g. one setup vs. another, or an aftermarket setup vs. stock.
I tried several calculators, including the one tsk94 linked. The relationship I describe earlier was the same in all of them. |
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10-23-2021, 06:17 PM | #30 | |
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10-23-2021, 06:19 PM | #31 | |
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10-23-2021, 09:35 PM | #32 | |
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10-23-2021, 10:37 PM | #33 | |
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Again, I wouldn't get caught up in the actual FRC number. It's not that important. |
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10-27-2021, 10:15 AM | #34 |
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Yeah a lot of people ignore bump stop and bump travel tuning which is the biggest problem with running "neutral" spring rates. Put 300-400lb spring up front and you will be down on the bump stops a lot even with shortened stops. There just isn't much stroke up front to work with due to packaging. Most coilovers are ~4-4.5" of stroke up front which gives you pretty much the same amount of wheel travel... leaves you with very little bump travel to play with once you put 700lb of corner weight on the spring. It's no wonder why many people feel the car drives better with 400-700lbs up front. By staying off the bump stops you may have an effectively lower front wheel rate in roll.
I would not say calculating FRC is useless. The data is all here including sway bar motion ratios. It's just a lot of work. It's useful for knowing how setup A or B will change the cars behavior given X or Y feedback from the driver. At the very least, playing with the spreadsheet helps the concepts sink in. You do need to be aware of all of the significant variables though and bump stops engagement is a huge one overlooked. Then there are the smaller things that move the motion ratio around a bit like track width and alignment. If you know your spring and sway are setup to produce the handling you want but the car is still missing something then you can now look at all the other little things that are easier to tune than springs and revalving dampers. Last edited by bbnks2; 10-27-2021 at 10:26 AM.. |
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10-27-2021, 08:32 PM | #35 | |
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