This is a continuation of the following thread:
https://www.fitfreak.net/forums/2nd-...ly-driver.html

This will be an attempt to compile all technical information regarding the GE8/CRZ and possibly GD suspension.

GE8/CRZ suspension design:
First I would like to comment that the CRZ and GE8 suspension is nearly identical. The only difference I have found is the aluminum front LCAs and front knuckle have different part #s on the CRZ. The front subframe is identical, so the CRZ aluminum LCA will bolt up to the Fit, the only unkown variable is if the knuckle bushing is a different size where it mounts to the LCA. (This would mean that a 5-lug swap would be necessary to run the CRZ LCAs negating any weight savings.)

FIT Knuckle:

CRZ Knuckle and LCAs.


Notice that the traditional orientation of the compliance bushing (red circle below) has been changed on the GE8/CRZ front LCA:


Contrast this with the RSX/EP3/EM2 and 8th gen compliance bushing orientation:
RSX:

8th gen civic:


And a better pic showing the RSX LCAs and polyurethane Energy Suspension bushings.



I also want to comment on the dramatic difference in the tie rod end links on the CRZ/GE8:
Notice the dramatic increase in length. I would assume this is because Honda raised the location of the power steering gear box, my Fit is in storage so I can't confirm this suspcion.


The problem with the previous design (i.e. RSX/EP3/EM2) was that the steering geometry was dramatically altered if the car was lowered.

Due to the massive lowering, the angles of the suspension geometries are no longer optimum. Take a look at the below picture which shows the arms and tie-rods angled upwards. A Bumpsteer Kit (reverse tie rods) and a set of Roll Center Adjusters (RCA) should fix this problem.




What is Bumpsteer? A bit of an explanation: Bump steer on the front wheels is illustrated in the diagram below, and it can be seen that it is caused by unequal angles between the steering tie rod and the lower arm. Depending on the difference in the angles, the wheel will either exhibit toe in or toe out on bump.
Lowering a car changes the angles between the lower arm and the steering tie rod, this in turn increases the bumpsteer on the front wheels, hence the benefits of a lower mass center is not seen because of the bumpsteer.





Why use Roll Center Adjusters? Refer to the diagram below: At standard ride height, the roll center is set by the angle of the arms and the roll center is an imaginary point where their lines would intersect. Ride & Handling guru John Miles advises that roll center is set between 40mm - 60mm above the ground for stability, and from this baseline the handling geometries can be set.




When you lower a vehicle, the wheels "move up" into the body and the angle of the arms is no longer optimum, in some severe cases they push the roll center low down below ground level. This would result in more roll than standard therefore the benefits of lowering the vehicle would not be realized. This is why you may read in some magazines and documents why lowering a standard car too much without geometry change is actually dangerous and adversely affect handling.

 

GD guys, feel free to post up part # and pics showing the difference in the GD suspension. Specifically the knuckle, LCAs, and tie rod end lengths.

Hopefully we can get this stickied.

 

+rep, great writeup!

Can you help me understand this illustration better?

If one reduces the spring length by 1" e.g., but then installs a 1" RCA, doesn't that basically just restoring the stock height of the vehicle?

Is there a way to maintain a lower overall center of gravity for the vehicle, yet retain the engineered [stock] suspension geometry?

 

ohhhhhhh... nvm, I get it - the RCA lowers the connect-point for the lower control arm. I was mistakenly thinking it raised the connect point for the strut.

 

It resets the roll center, but in order to get the most optimal camber changes in your suspension travel, the lower arms may need to be swapped for something that is modified, such as with having a bend, or change in length to the structure. I think it's pretty car-specific with those types of mods, and I'm not sure if the Fit would benefit from it, or if it is even possible to see a correction in the design, but that's what I know from at least a few other vehicles. Our Fits probably handle pretty well with some stiff suspension and better grip, regardless, but for the go-kart feel, and those extra hundredths of a G in grip, some more work could probably be done. I'd just keep an eye on that b-spec racing series and see what they come up with for the fit, and go from there.

 

Maybe some Hotchkis front camber plates (from the CRZ or other Honda models) could be used to gain camber in the front? I haven't looked into it but, are there any adjustable front camber kits for the GE8?

For the rear, I've seen this....but it looks like it's more for the Hellaflush crowd:
ＧＥフィットリヤアクスル