G4s and extra weight

[MAvery]

I have G4s on an 02 WRX wagon. So, there's already 80 lbs (36 kilos) more weight in back than the sedan. In addition I carry about 150 lbs (68 kilos) of gear in back all the time. This is obviously much more weight than the G4s were designed for. The ride is not as smooth as without the weight, and even with the rears adjusted a high as they will go the ride height is lower than I would like. Rear suspension travel is compromised and I bottom out once and a while.

I know I need longer rear springs, but should they be stiffer as well? Logic says stiffer springs to support the extra weight, but I don't want to increase harshness. The current setup is at my personal limit. Will longer/stiffer springs make things better/smoother due to their ability to handle the extra weight, or does the ride degradation have more to do with damper valving?

I have a friend offering me another set of 5k 220mm G4 front springs. Should I try them out in the rear on my car?

[Whiteline]

Hello MAvery,

It deffinately sounds like you could do with the extra length rear springs, however increasing the spring rate is going to increase ride harshness and also change the chassis balance for times when the vehicle is unladen.
If you can get a hold of the 220mm 5 kg springs cheap enough, it may be worthwhile trying them and deciding for yourself if they satisfy your requirements.

Cheers
Wayne C

[Arnie]

Looks like Mark will be trying out my springs!

Wayne, one complaint that mark had, that we'd previously discussed, is the tendency for the coilovers to eject one out of one's seat on "table top" type of freeway overpasses. Also when one comes off of that overpass onto a drop one really gets dropped! Most of the road/track biased coilovers tend to do this. Is this the result of less travel? Or the valving? When compared to a stock WRX strut, these types of surfaces provide quite a bit of drama where the stock strut just shrugs it off. We were just wondering if its simply inherent (why?) and if its within the Group 4's range of adjustment or valving to get that type of ride.

[Whiteline]

Hello Arnie,

The majority of this complaint will be to do with there being less travel in the shock/strut as they are designed to be run at a lowered ride heights (to enable them to ride in the mid point of there overall allowed travel range). If they are set at a ride height close to OEM they are close to there upper limit, resulting in reaching full extension quite easily on Yumps in the road surfaces, resulting in driver ejection as the shock is unable to absorb the momentum of the vehicle. The same will also occur on drop offs.
The stifffer spring rates and valving are going to exagerate this occurance and make it more pronounced than that of the OEM struts soft springs and valving.
You could try adjusting the Group 4's to full soft adjustment to see if it helps, however it will provide less control of the suspension.

Cheers
Wayne C

[Arnie]

Ahhh, I was thinking that it might be something along those lines. I will try lowering the car a bit and see how that affects things on those types of yumps. I think I've made the assumption that by keeping the car higher I would maximize travel however I think I failed to realize that that may only apply to bump travel while at the same time reducing droop travel. If I "centered" things I could probably reduce the tendency for seat ejection feel I get on occasion. This feel is something that Mark and I discussed when I took his car for a test drive over my local highway yumps.

So what ride height would you think would be the rough center of max bump and droop travel?

[Whiteline]

Arnie,

Ride heights of around 350 to 360mm on the front and 340 to 350mm on the rear (measured from the centre of the wheel to the guard) will provide sufficient droop travel whilst not lowering the vehicle too excessively.

Wayne C

[MAvery]

Unlike Arnie, my car is too low - about 335 with the rears adjusted as high as they'll go. I've ordered longer, slightly stiffer, springs (8"/250lb) to try in the rear. I was hoping to get the ride height to be about an inch lower than stock, but I'll take your advice and aim a little lower than that.