How high should an FD w/coilovers be for best performance?
09-07-04, 01:06 PM
#1
How high should an FD w/coilovers be for best performance?
What's the optimum height setting from the ground to the top of each fender arch (see my drawing) for a car thats going to autoX and roadrace? If you set the height at an optimum level and you get lower profile tires, ie. 225/50/16 to 225/45/16, do you raise the car to compensate for the smaller tires?
Last edited by Juan; 09-07-04 at 01:08 PM.
09-07-04, 01:27 PM
#4
Eats, Sleeps, Dreams Rotary
I think he said 25 inch for both front and back are ideal....I just wonder if it should be alittle higher in the back as any FD's I see coming out of a corner always appear to be doing a wheelie.
09-07-04, 02:40 PM
#6
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Search in the Suspension forum. He seems to post those measurements on a daily basis 
I remember him saying to set fronts at 25" and rears maybe at 25.5" but search for yourself as I could be wrong.
I remember him saying to set fronts at 25" and rears maybe at 25.5" but search for yourself as I could be wrong.
09-07-04, 02:42 PM
#7
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Originally Posted by rotary rockett13
Yes,your rear always needs to be a little higher than the front. If not when you acclerate your front end will just float.And you cannot hardly steer.
There is no "correct" ride height setting. The height of the center of gravity of the car is directly related to its ride height and we want the car as low as possible due to the lower CG's advantages in weight transfer. Therefore you run the car as low as you can without bottoming out the suspension or scraping the chassis.
Last edited by DamonB; 09-07-04 at 02:44 PM.
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09-07-04, 02:55 PM
#8
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My ride heights are 25" in front, 25.5" in back. If your car is regularly driven on the street, I would recommend a height of 25.25-25.5", front and back. Make sure you set ride height with you in the car and with a full tank of gas. You do not want the rear to be lower than the front, or you will get increased lift at high speeds.
09-07-04, 02:55 PM
#9
Racing Rotary Since 1983
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low is fast.
lateral weight transfer is what you want to minimize.
only 2 things effect lateral weight transfer.
1. track width (wider is better/faster)
2. center of gravity height. (lower is better/ faster) the CG of a stock RX7, BTW, is 17 inches.
the primary challenge for any front engine rear drive car is making the rear stick in a corner so you can get on the power before the other guy.
so rear end stick is most important. i think that 25 inches all around is the ultimate practical ride height objective for the FD.
other things like sway bar stiffness, shock valving, spring rates, tire pressure, non-vertical weight distribution and suspension settings effect the speed at which the weight transfers. as such they are tuning/trim considerations.
so if you run coil overs and can run 25 in the back i recommend it.
don't forget that the camber needs to be reset everytime you change ride
height. run your shocks and tire pressures soft in the rear for hook up.
good luck,
howard coleman
lateral weight transfer is what you want to minimize.
only 2 things effect lateral weight transfer.
1. track width (wider is better/faster)
2. center of gravity height. (lower is better/ faster) the CG of a stock RX7, BTW, is 17 inches.
the primary challenge for any front engine rear drive car is making the rear stick in a corner so you can get on the power before the other guy.
so rear end stick is most important. i think that 25 inches all around is the ultimate practical ride height objective for the FD.
other things like sway bar stiffness, shock valving, spring rates, tire pressure, non-vertical weight distribution and suspension settings effect the speed at which the weight transfers. as such they are tuning/trim considerations.
so if you run coil overs and can run 25 in the back i recommend it.
don't forget that the camber needs to be reset everytime you change ride
height. run your shocks and tire pressures soft in the rear for hook up.
good luck,
howard coleman
09-07-04, 06:27 PM
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If you have the option of setting your ride height wherever you want, you presumably must be running coilovers. One way to do this is to start at a reasonable height - 25" is as good a place to start as any, then adjust each corner with you in the driver's seat and the car the way you would have it on track (no spare tire or jack, 1/4 tank fuel, etc.) so as to optimize your corner weights (LF + RR = RF + LR). Once those are set, you can raise or lower all 4 corners the same amount to lower the car as much as possible without running into problems with bottoming out, scrubbing your tires on wheel well liners, fenders, etc. You can also raise the car the same way if you have trouble at that ride height. You will change camber slightly if you change the ride height slightly, so it makes sense to get a precision alignment once you've figured out where you're running the car, but changes of a 1/4" or so won't make enough difference to make the car "evil" handling.
09-07-04, 07:04 PM
#13
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25" (one finger's space from tire to wheelwell lip) is pretty low. If you've seen a 7 with H&R springs then you know what 25" looks like. I prefer 26" myself (2 fingers, although I use coilovers) and I think it's ideal for the streets. There is just too many dips, bumps, potholes, etc to slam your car without damage. Oh, and the hootchies may think it looks cool but if they have to wear a kidney belt then expect them to ride with someone else. 
Last edited by GoRacer; 09-07-04 at 07:10 PM.
11-12-04, 11:32 PM
#14
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Originally Posted by howard coleman
low is fast.
lateral weight transfer is what you want to minimize.
only 2 things effect lateral weight transfer.
1. track width (wider is better/faster)
2. center of gravity height. (lower is better/ faster) the CG of a stock RX7, BTW, is 17 inches.
the primary challenge for any front engine rear drive car is making the rear stick in a corner so you can get on the power before the other guy.
so rear end stick is most important. i think that 25 inches all around is the ultimate practical ride height objective for the FD.
other things like sway bar stiffness, shock valving, spring rates, tire pressure, non-vertical weight distribution and suspension settings effect the speed at which the weight transfers. as such they are tuning/trim considerations.
so if you run coil overs and can run 25 in the back i recommend it.
don't forget that the camber needs to be reset everytime you change ride
height. run your shocks and tire pressures soft in the rear for hook up.
good luck,
howard coleman
lateral weight transfer is what you want to minimize.
only 2 things effect lateral weight transfer.
1. track width (wider is better/faster)
2. center of gravity height. (lower is better/ faster) the CG of a stock RX7, BTW, is 17 inches.
the primary challenge for any front engine rear drive car is making the rear stick in a corner so you can get on the power before the other guy.
so rear end stick is most important. i think that 25 inches all around is the ultimate practical ride height objective for the FD.
other things like sway bar stiffness, shock valving, spring rates, tire pressure, non-vertical weight distribution and suspension settings effect the speed at which the weight transfers. as such they are tuning/trim considerations.
so if you run coil overs and can run 25 in the back i recommend it.
don't forget that the camber needs to be reset everytime you change ride
height. run your shocks and tire pressures soft in the rear for hook up.
good luck,
howard coleman
TIA,
Nic
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