Spring Rates for my Protege

[Knox MSP]

So while the car is down (blown diff) I've decided to do a couple other things. One of those things is coilovers (deciding between BC and Fortune Auto right now), and I am totally confused about spring rates. Almost all the coilover setups I've seen for autocross in my car are set up with a stiffer rear spring (ie./ 450F/600R). Is this normal in a mid-weight FWD?

Right now I'm thinking about going with 8k Front/10k Rear. I still want to drive the car in the mountains, so that involves travelling to and from, and I don't want to rupture a disc on the way there, but still want it properly sprung for autocross as well.

Any advice is appreciated.

Thanks,

Joe

[TedV]

Yes, it is normal. Stiff rear helps the car to rotate, not push, is lighter than a huge sway bar and helps keep the front wheels on the ground when turning and accelerating.

[thrdeye]

I had BC Racing Coilovers. I ran 10F/12R in my STX Subaru (2002). I'm not sure how stiff you'll want to go exactly, or if there needs to be a bigger variance front to rear. Luckily springs are cheap and easy to change. 8/10 sounds like a pretty good start.

[PushinTheLimit]

Even alot of guys in road racing that run coilovers, they run stiffer rear springs than front springs to help rotate the car on mid-corner.

[steverife]

I'm of the theory that the relationship between the rates for the front and rear of the car aren't the end all be all of balance.

When I figured up an FSP build for the Mazda 3, I think I came up with 700F/450R. The downsides to a lot of rear rate is the car can be less predictable over bumps and less liveable on the street.

With all that said, the CRX is 500/550 and is going to be about 510/560. It was 450/500 last year and 400/450 when I first got it. If you talk to 20 different ST Honda drivers, you will probably 10-15 different rate combos. Some guys run 900/700, some run 700/560, some run 500/500, some run 500/600, some run 450/600, and so forth. All of them seem to handle about the same and no setup seems to be decidedly faster.

[Wheelman_13]

I'm of the theory that the relationship between the rates for the front and rear of the car aren't the end all be all of balance.

When I figured up an FSP build for the Mazda 3, I think I came up with 700F/450R. The downsides to a lot of rear rate is the car can be less predictable over bumps and less liveable on the street.

With all that said, the CRX is 500/550 and is going to be about 510/560. It was 450/500 last year and 400/450 when I first got it. If you talk to 20 different ST Honda drivers, you will probably 10-15 different rate combos. Some guys run 900/700, some run 700/560, some run 500/500, some run 500/600, some run 450/600, and so forth. All of them seem to handle about the same and no setup seems to be decidedly faster.

It's just different means to the same (stiff rear) ends.

500/600 springs with 30/30 tire pressure and/or front-biased shock settings might accomplish nearly same thing as 500/500 springs and 25/35 tire pressures and more rear-biased shock settings. There would be subtle differences, but the car would rotate with similar ease.

[TedV]

If you would like some reading, take some measurements, do some math... a decent starting point is http://farnorthracing.com/autocross_secrets5.html

clifts notes version "Measure your corner weights, unsprung masses, and motion ratios, and then pick springs that put the front NF at 2.2 Hz and the rear at 2.5 Hz. " That will give you a ballpark starting point and then adjust the car to make it do what it wants to go fast.

[steverife]

I'm of the theory that the relationship between the rates for the front and rear of the car aren't the end all be all of balance.

When I figured up an FSP build for the Mazda 3, I think I came up with 700F/450R. The downsides to a lot of rear rate is the car can be less predictable over bumps and less liveable on the street.

With all that said, the CRX is 500/550 and is going to be about 510/560. It was 450/500 last year and 400/450 when I first got it. If you talk to 20 different ST Honda drivers, you will probably 10-15 different rate combos. Some guys run 900/700, some run 700/560, some run 500/500, some run 500/600, some run 450/600, and so forth. All of them seem to handle about the same and no setup seems to be decidedly faster.

It's just different means to the same (stiff rear) ends.

500/600 springs with 30/30 tire pressure and/or front-biased shock settings might accomplish nearly same thing as 500/500 springs and 25/35 tire pressures and more rear-biased shock settings. There would be subtle differences, but the car would rotate with similar ease.

I know those are hypothicals, but people don't even seem to make big adjustments. I'm just not sure how much rear rate matters. I do know that it is very important to optimize the front.

[Knox MSP]

Thanks guys. Think I am going to start with the 450/550 rates to start off and see how I feel about it. I guess I should start looking for some places to get cheap springs.

[integra55]

like Rife said everyone seems to be different ... my CRX is 450 F and 400 R .... front Koni's full soft and rear full stiff .... 3 position rear bar in the stiffest setting and a tiny HF front bar

[steverife]

Thanks guys. Think I am going to start with the 450/550 rates to start off and see how I feel about it. I guess I should start looking for some places to get cheap springs.

I think that is a decent starting point. If you ever get serious, I think you'd want to go a little higher on the front, but the 450's should be more than "good enough".

Do you know what length you need? I think I have 300, 400, 450, 500, and maybe 700's that I'm not using.

[steverife]

like Rife said everyone seems to be different ... my CRX is 450 F and 400 R .... front Koni's full soft and rear full stiff .... 3 position rear bar in the stiffest setting and a tiny HF front bar

You ever try the shocks full soft all around? Or full stiff?

[Knox MSP]

I believe they would be 8".

[integra55]

like Rife said everyone seems to be different ... my CRX is 450 F and 400 R .... front Koni's full soft and rear full stiff .... 3 position rear bar in the stiffest setting and a tiny HF front bar

You ever try the shocks full soft all around? Or full stiff?

yeah... full stiff = a bit more push .... full soft is pretty fair in the wet

[Knox MSP]

Coilovers ordered. So excited!