Spring rates and handling

[TwinDad]

As I've been researching spring combinations for my GSW, I've noticed something about the entire golf platform that I have not noticed on other cars that I've done suspension on. The golf is the first fwd car though. Typically the spring rates up front are considerably heavier lb/in up front than the rear. On the golf, gti and R, the front is lighter. Is that a fwd thing. Does it help with oversteer somehow? The reason I ask is because I'm considering putting stock gti manual transmission springs up from with my stock GSW rears. My front currently sits almost 1/2" higher than the rear. Based on measurements, these should lower my front about 5/8-3/4". They are stiffer than the stock golf fronts though and 10lb/in stiffer than the golf rears. What's the negative in doing this? Do I also need to add stiffer rear springs? Or would a larger rear sway bar help it out?

 

[IDriveaGTI]

As I've been researching spring combinations for my GSW, I've noticed something about the entire golf platform that I have not noticed on other cars that I've done suspension on. The golf is the first fwd car though. Typically the spring rates up front are considerably heavier lb/in up front than the rear. On the golf, gti and R, the front is lighter. Is that a fwd thing. Does it help with oversteer somehow? The reason I ask is because I'm considering putting stock gti manual transmission springs up from with my stock GSW rears. My front currently sits almost 1/2" higher than the rear. Based on measurements, these should lower my front about 5/8-3/4". They are stiffer than the stock golf fronts though and 10lb/in stiffer than the golf rears. What's the negative in doing this? Do I also need to add stiffer rear springs? Or would a larger rear sway bar help it out?

Is that a fwd thing? - it's probably more dependent on suspension design thing. The actual wheel rate is what designers are going for and depending on the pivot points(I forgot the actual names for these) the actual wheel rate can be different than spring rate.

What's the negative in doing this? You may not actually accomplish what you want. That's what someone said in your other post when them mentioned that the engine transmission weight may go into what the actual ride height will be. Also, are there other suspesion components to that go into ride height that you are taking into consideration?

Do I also need to add stiffer rear springs?
Or would a larger rear sway bar help it out?

I would like to hear more about what you are attempting to fix/correct/change here with putting different springs on the car. Generally changing the relative spring rates front/Rear can change the handling dynamic of the car. Sways do that too. Without knowing what you attempting to accomplish, it's hard to say if they will "help" or if you need to add stiffer springs.

Are you just attempting to just get a mild drop or something else?

 

[TwinDad]

Ideally I'm looking for a mild drop in the front without increasing the ride firmness too much. While researching the ride heights and spring ratings, I noticed that all of the front springs were softer than the rear. The negative I'm talking about is how it could hurt the handling. The gti springs are stiffer. This means that I will have a stiffer front spring rate than my rear. I'm not talking about the ride height. I know that is another gamble. I was concerned if it was set up this way to control or balance understeer and oversteer. I've been reading more on my own on this outside of the forum. From what I can tell it is a fwd thing. Rwd cars tend to oversteer more while fwd tend to understeer. Softer springs up front will lessen understeer. Stiffer out back increases oversteer. I'm going from 130lb/in up front to 175lb/in. My rears are 165lb/in. The gti rear is 230lb/in. Yes I now answered my own questions on it. The real test will be to see how it actual works out driving it. It might be negligible under most driving situations. Since puting in the gti rear springs will most likely bring back a negative rake, a thicker sway bar in the rear is probably the best solution.
As far as not achieving my desired drop, I think the poster in the other thread was really trying to split hairs. The weight difference between an auto golf and a manual gti is a few lbs. I guess I'm more optimistic than he is. I'll see how it goes and post pics up on that thread when I get around to putting them in. Its easy for guys to sit behind the keyboard and try to figure out why it won't work. Other people just go and do it. Thanks for the reply

 

[breaking badly]

It's logical. Read this and you will agree rear springs usually need to be stiffer.

When you debate weight distribution and spring rates you want to know the wheel
rate, not just the spring rate. It's not the same, not on rear at least. Actually it is
even far off, but let me begin with the fronts:

The front spring is sitting on the strut close to the wheel. The lever ratio is close
to 1 here.

The rear spring is sitting somwhere in the middle of the lower control arm, far from
the wheel. For that reason the spring itself needs to provide twice the stiffness to
gain the desired wheel rate. I'd guess effective ratio would be around 0.6 or so.

So, when the rear spring is just marginally stiffer than the front spring, it is in fact
(the resulting wheel rate) still significiently softer at the wheel (where it matters).

Agreed?

On a side note, never forget a FWD station wagon has a huge difference in rear
axle weight between empty and fully loaded. Loaded it's more than twice the weight
which means spring and damping rates require to be a big compromise. You cannot
only count a weight distribution of 60 : 40 for the empty car. With the boot full of
stuff it's 40 : 60 and more than that. Empty about 500 kg on rear, loaded more than
1000 kg (2.200 lbs). Contrarily, the front remains almost constant. It's affected by
dynamic weight distribution (braking hard), not so much by loading the car with stuff.

So, what to do:

Don't brake your head about spring rates. You won't even notice any variation of
20 % more or less. What you would notice is extreme lowering since with that the
car will probably sit on the bump stops which are 10 x (1000 %) stiffer compared
to the steelen main spring.




.

 

[TwinDad]

Yeah. The more I read the more I figured it wasn't a big enough variable to change anything drastically. I found my way onto a British forum if guys who amateur race. The stuff they were spouting out made my head hurt. Bottom line it's less than 20% increase. Should be fine. Just hoping now the drop is sufficient ����