Ok, I know a lot of you track your car, so I trust your advice. I have A'pex N1 coilovers and they come w/ F/R 9kg/5kg. It feels great for the street and aggressive driving, but I plan on swapping them over to a hatch that will be mostly for track use. So, I'm thinking about keeping one of the springs and changing the other. Which of these would be a better combo:

Front/Rear:
5kg/7kg (keep 5kg rear spring and move it to front)
7kg/9kg (keep 9kg front spring and move it to rear)
9kg/11kg (keep 9kg front spring in front)

Would the 9/11 setup be too ruf as the car will still see some occasional street use? For reference, here's what the rates equal in lbs/in:

5kg/mm = 280lbs/in
7 = 392
9 = 504
11 = 616

Oh, and the front and rear springs are the same length, 225mm (~9").
Thanks.

 

.....i dunno if you can swap those coilovers from front to rear and vice versa, but here's what i'd do on an itr:

keep the front 9k springs and change the rear 5k springs to 12k. Perfect. jmho

 

i'm going to agree. with stiffer springs in the rear, the car is going to have a tendancy to oversteer. this will make it much easier to rotate the back end of the car which is a desirable affect (at least for me) for a track car.

 

I'll only be swapping the springs, which are the same length and ID, so it shouldn't be a prob swapping them if I need to. Wow, 9/12 huh?...I was thinking that too much of a difference between F/R would not be good, that's why I asked about 9/11. How would the ride quality be since the car would still see some occasional street use? I was told by a knowledgable source that one should keep the springs rates as low as possible w/o allowing the dampers to bottom out. That's why I asked about the 5 and 7kg setups cuz I don't want them too stiff where I might lose traction from it not being able to react to the road well enough. Thanks.

 

your reliable source gave you very good a reliable information....far too many people overkill their spring weights just because everone else is doing it or they heard realtime sets theirs up that way. you only need enough spring to counter the movement of the unsprung weight....as you said.

you are also correct about "too much difference between f/r would not be good" this is called roll ratio, and it is primarily what causes your car to handle in a particular way with regard to oversteer/understeer (this and contact patch). In a nutshell, the ratio between the front a rear spring rates (when considered as a whole system with the sway bars) control that rate at which your car's weight transfers from one side to the other as you go into a turn. by slowing the transfer down at one end of the car or speeding it up at the other you can affect oversteer/undresteer (all else being equal). What you have to also consider is the weight difference in the front and rear of the car, however...as this is what you are compensating for when having different spring rates f/r. It is my opinion and experience that a neutral car is fastest. I prefer to user driver input to make it rotate or not. others like a car that is biased one way or the other....its a matter of style and preference. as young mr. lisa pointed out above he likes his protege loose with plenty of oversteer....I think and ITR rear is too light for this and it causes too much rear break lock-up and instability.....but its all a matter of opinion and preference and thats what makes racing fun.

fyi I run 800f/700r w/ 22mm rear bar and stock front bar w/ 5" ride height....it works for me.

dave w

 

Wow!, thanks for the great info and explanation. I plan on using a 22mm rear sway also, but would like to test how it feels w/o it first and just playing w/ spring rates. Do you have an estimate or an equation to calculate how much effective spring rate a 22mm rear sway would add to the rear springs on a honda? You seem to be one of the few ppl on any of the US boards that run a higher spring rate up front. That seems to be mostly a jap thing. Thanks again for the info.

 

the reason japanese coilover setups have higher spring rates in the front is to counteract nosedive under heavy braking. it makes the car more stable under heavy braking and improves the turn in response. the car's tendency to over/understeer is then adjusted thru bars and damper settings

i agree with davew that a neutral setup is faster around the track... oversteer can make u feel fast, but sometimes u are actually losing time and scrubbing off speed in the corner.

it's all driver preference. for instance, mika hakinnen prefers a neutral setup and is very precise in the way he sets up for a corner, using minimal braking on entry and maintaining maximum corner velocity to get the maximum exit speed. david coulthard in contrast, uses much more oversteer, heavier entry braking, and really uses the tires thru the corner... so one is precise and smooth, the other is harder and rougher, but both can be equally fast...





[Modified by Spikey, 8:28 PM 1/10/2002]

 

absolutely...but the jdm racers could certainly control nose dive w/ stiff front springs and still run even stiffer ones in the rear like many usdm racers do. Its my feeling that the rear is too light for super high spring rates and it makes the rear float too much under heavy braking. but I know racers who drive faster than I and whom I respect that dissagree and prefer the higher rates in the rear...I tried it and didn't like it. try both and see what you like....just be sure to drive/brake accordingly or you might get yourself in trouble.

sorry, off the top of my head from my desk at work I don't them the formula for determining the effect of the 22mm bar on the rear spring rates...but i'm sure an internet search will net some results for you.

-dave w

 

.....actually my opinion may be moot because I'm speaking from a dc2 chassis opinion.

I want to correct what I posted earlier:

I like to run the same size wheel/ tire combo on all four corners so I can rotate from front to rear... With that in mind, the 2/3 (f/r) seems to work very well on the dc2. This would actually equate to 200f/300r, 5kf/7.5kr, or 9kf/13.5kr... I dunno how this translates over to the eg's... Supposedly they have the same platform so it shouldn't be too different.

I've seen many road racers run 400f/500r or 500f/600r on the dc2. I guess it all depends on how you like you car to handle. For a street car, you don't want too much oversteer... But if track only, then maybe more oversteer is ok... And yes the jdm guys run lower rates in the rear, but they run skinnier tires in the rear to get oversteer. Just different ways of skinning a cat I guess.

Something easy to do would be to run the opposite of how they came: 5kf/9kr combo of the coilvers you have now and see how you like it. Then stiffen up front or rear depending on how you like it... Trial and error, y'know? You'll prolly end up with 9kf/ (9,10,11,12,13.5)kr after running different setups... I figure those coilovers shocks can take at least 9k...

 

I thought that JDM racers also use narrower rear tires to help rotate their cars, since they go with lighter rear springs relative to the front. It's almost always 195-55/15 in the rear with 205-50/15 or 225-50/15 or 215-45/16. Something like that but always larger in the front.

 

Yeah, that's what I said.....