Originally Posted by GSS138 Completely depends on corner weights and if you are trying to lean the car towards more understeer or more oversteer. On my first set of coils(soon
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08-12-2014, 05:22 PM | #1 (permalink) | |
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2.0f/2.3r is going to be loose, 2.3f/2.1 is pretty nuetral and 2.1/2.0 is a little soft and probably still on the nuetrul side (tending towards oversteer).... Fwiw, my race car sits in the 2.4f/2.25 and tends towards slightly loose on corner exit and that is with no rear bar. |
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08-12-2014, 09:07 PM | #2 (permalink) | |
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Every post market "spring kit" out there tunes to something around .80-.85 because they can sell that product and not kill someone. Or at least not be sued for creating an "unsafe ride rate" as per the DOT. that being said, I don't drive your car that you know intimately. I see what you are saying, because you know your car's frame, your sway bars, your tires, what you like, etc. better than I do, and are a much more experienced driver. But as for a baseline tuning point, and to understand how a suspension works(regardless of the car) the Front ride Freq/ rear ride Freq, tells you how the car is setup. <1 induced understeer. > 1 induced oversteer. That's not my opinion that's just physics. Doesn't tell you how to drive it fast, doesn't make you push the throttle when you know you maybe shouldn't, it's just a reference point.
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08-12-2014, 11:39 PM | #3 (permalink) | |
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Increasing spring rate at an axle (front or rear) with no other changes, shifts the lateral load transfer distribution (LLTD) towards that axle. LLTD tells you how much of the car's lateral weight transfer is borne by either the front or rear axles in roll. An axle pair of tires generates the most lateral grip, when inside and outside are most evenly loaded, due to the tire load sensitivity curve. If at Setup A, the front and rear had equal LLTD, and from there you stiffened the front springs, you'd now have a greater front axle load differential at a given lateral g, than you had before. Greater load differential = less grip. Less grip at front means shift towards understeer. The ratio of ride frequencies is one data point in the understeer/oversteer equation but hardly the only one. Sway bars, resulting geometry of the outside tires, static weight distribution, wheel/tire stagger are a few of the other variables. Changing roll stiffness at one end can have second-order effects (like improved resulting geometry due to less overall roll) but the primary effect is to increase the load transfer of the stiffened end, resulting in a shift of grip to the other axle in cornering. ...but you don't have to take it from me - there are countless texts on the subject, encourage everyone to check them out and discover how it all works, for themselves. |
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08-13-2014, 12:17 PM | #4 (permalink) | |
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If you calc the rates for every single post market spring kit or out of the box coil over solution, you will either get a number between .80 -.90 (Understeer) or you will get something in the range of 1.13-1.25 (looser rear end). (Assuming close to OEM un-sprung corner weights) Swift Spec R= 2.0115/2.2145=.90 Tein S-tech= 1.682/1.87 =.89 Nismo T2 motorsports springs = 2.0821/2.4224 = .859 Now let's look at some popular performance coils Tein Flex = 2.2035/1.9833= 1.11 Stance GR= 2.2035/1.9624 = 1.12 Megan Racing 2.0115/1.6650 = 1.21 (loose!) Edit: Synolimit's Setup 2.6880/2.0361 = 1.32 (have fun cowboy) Our OEM(non nismo) 1.6334/1.8563 = .89 This isn't a coincidence! Again, it doesn't make your car go fast, has nothing to do with grip, doesn't get you trophy girls. It's just a baseline calculation that you can use to have a reference point for what you can expect out of your spring, your motion ratios, and your corner weights to do. Of course putting the tires, driver, sways, fuel, etc on top of this number changes everything. But it's nice to have a solid starting point . This PDF explains it better than I can: Freq of Ride rrates
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08-13-2014, 03:22 PM | #5 (permalink) | |
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08-13-2014, 12:52 PM | #6 (permalink) | |
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What I have seen with some regularity for full coilovers on 370Z race cars is front range of 1000 to 1200 lbs and rear of 600 to 900 lbs. These are on cars races in series such as Continental and Pirelli and on either DOT or race slicks. Full on race slicks do need signficantly more spring due to stickage factor. I usually jump 200 lbs from rates I use for DOT tires minimum. And differnt tracks may dictate changes as well. Im planning on having a range of springs from 1000 to 1200 front and 600 to 900 rear. I just know my old DOT setup of 1000 front and 500 rear is allowing too much rollover with slicks.
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Grant Last edited by Shamu; 08-13-2014 at 12:55 PM. |
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08-13-2014, 01:11 PM | #7 (permalink) |
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Absolutely 100%. And like I said, these numbers sure as hell don't teach you how to drive or win anything for you.
But what they are useful for is tuning. So if you know your car is setup with say a 1.15 ratio, and man you just need the *** end to swing around a little bit faster, you can now with no guess work select a spring that is going to help move your car towards 1.20 which should make it a little looser. It's just a tool and a reference. And it sure as heck can't tell you what you like or prefer, it's like saying "hey it's 70 degrees outside". Some people might like it, some people might not. Some people put on a jacket, some people go swimming.
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