CSG and RCE tag-team suspension Q&A thread! Ask us anything!

[cjopant]

Originally Posted by Racecomp Engineering

The change in ride height due to changing weight is a function of spring rate.

Changing compression settings will not affect this in any way, so don't do it for that reason.

Your car looks a little low IMO.

- Andrew

Thanks for the reply!

Would a slightly higher spring rate increase the threshold for added weight affecting height? If so, is that a silly thing to pursue?

It's definitely a touch too low, especially in the rear (where it rubs). I don't have any issues up front anymore.

[Racecomp Engineering]

Originally Posted by cjopant

Thanks for the reply!

Would a slightly higher spring rate increase the threshold for added weight affecting height? If so, is that a silly thing to pursue?

It's definitely a touch too low, especially in the rear (where it rubs). I don't have any issues up front anymore.

Stiffer springs would reduce the change in ride height, but in general that's not the reason to use stiffer springs. Cars with a lot of downforce might use stiffer springs (in part) to reduce variations in ride height at speed and because high downforce cars may be more sensitive to changes in pitch.

But for our cars, minimizing the amount the suspension moves is not a good idea for a car that's driven on the street.

- Andrew

[H1C]

Originally Posted by H1C

Question for CSG, RCE and other suspension gurus:

I recently installed 'motorsport-oriented' coilovers with Eibach Race springs: 500 lbs/in F, 450 lbs/in R. I have the TRD front sway, OEM rear, and got the ride height to about where it was with RCE Tarmacs and B8s. In fact I could not quite get the front as low as it was with the Tarmacs and B8s; the 6 inch long springs w/ no helpers would not remain captive at full droop if I went that low. So the front is maybe 7 - 10 mm higher than it was. There is now about a 5 mm rake F to R, whereas with the Tarmacs I measured a 15 mm F to R rake. I also have Ground Control top-mounted camber plates and their rear top hats that allow the shock shaft to extend about an inch higher.

I find now that the suspension soaks up bumps and broken/patched pavement incredibly well. I hear such pavement imperfections more than feel them now. And it corners very flat, as far as I can tell by street driving. I've yet to try this set-up at an auto-x or track day. I would say overall this set-up is the most comfortable suspension I've had on this car by far. I've had OEM, TRD springs and sways w/ OEM shocks, the RCE Tarmacs and B8s, and now this.

What's odd is that on relatively smooth pavement, I sometimes but not always get a bobbing or jiggling at the nose. They're small oscillations, and it kind of reminds me of driving an older 911 with stock suspension. I say relatively smooth, because in this part of GA there is no completely flat and smooth pavement. It's hilly around here, and they seem to have paved the roads disrupting the natural topography as little as possible, so there are always some undulations and ripples, even in newly laid asphalt.

But I seem only to get this jiggling or bobbing when the suspension is not being worked very hard. Any ideas on what could be causing this?

A couple of possibilities that came to mind are:

• Engine and trans are moving around on soft OEM mounts out-of-phase with suspension?
• Front suspension pivot bolts need to be loosened and re-torqued? I used to have adjustable F LCAs on the car and put OEM back on at the same time I installed the coilovers, along with adjustable R LCAs. I did play around with the ride height after initially torque-ing the LCAs down.
• I need to lower the car more? The drop currently is very mild, probably 15 - 20 mm lower than stock, and the spring perches are sitting in the upper 1/3 to 1/4 of available thread on the shock bodies. I have tons of available compression travel but not much droop: around 25 mm in F and 30 mm in rear.

This is my first go with a 'motorsports-oriented' coilover on this or any previous car. All my previous aftermarket suspensions were in the vein of Eibach lowering springs and Bilsteins, or PSS9's. I've never dealt with such high spring rates before. Is this kind of bobbing/jiggliness something to be expected with 500 lb/in springs?


Thanks for any input you guys have!

Originally Posted by Racecomp Engineering

This sounds very much like many motorsports oriented coilovers.

Great ride over big bumps and a bit jiggly over relatively smooth pavement. This happens with a coilover that has a lot of low speed compression damping and gas pressure with a very digressive or flat high speed compression.

Reducing gas pressure would help but may affect performance. Do you know what your adjuster controls (i.e. bleed or preload)? Got a shock dyno?

As for your ride height, why not use helpers? I basically always recommend them, and they're even more useful with springs as stiff as yours if you want to get the ride height right.

- Andrew

Thought I'd provide an update on this front-end bobbing/jiggliness with my MCS 1-way non-remotes, in case someone else with motorsport-type dampers encounters a similar issue:


I wound up removing all of the forward rake by lowering the rear 6 mm, because I've been finding the car too loose at auto-x in transitions and on corner exit. I found this to be the case even with a front-biased spring setup, and after adding a bigger front swaybar (replaced the TRD with the Perrin 22 mm set on stiff).


To my surprise, the zero rake made an already very good ride noticeably better. The car breathes with the road now, and rides flat over long stretches of bumpy and broken pavement. And those sections of local roads that used the get the nose bobbing -- no more. Not completely, but I'd say almost. And whereas the nose used to bob up and down continuously over these sections, now the front and rear feel like they're breathing simultaneously with the undulations. A couple of oscillations and then it settles, whereas before it was continuous bobbing at the nose. I'm not sure if this is what flat ride feels like, but I can't believe how calm the car is now over these sections.


I wouldn't have guessed that the ride could be so sensitive to a small forward rake, but apparently in my case, with my setup, it is. I'm looking forward to auto-xing with zero rake this weekend in our pretty bumpy local lot. I'm hoping and expecting that the rear will be more settled, and that the car will overall maintain more grip over the bumpy sections of the lot.

[Var]

Is it worth corner balancing a car if you're going to be adjusting rake and ride height after the fact?

Has anyone just carefully adjusted their ride height at all corners and gotten remotely close cross weights?

[strat61caster]

Originally Posted by Var

Is it worth corner balancing a car if you're going to be adjusting rake and ride height after the fact?

Has anyone just carefully adjusted their ride height at all corners and gotten remotely close cross weights?

Yes, if you adjust two adjacent corners of the car equally, i.e. front/rear or left/right it should have negligible to zero impact on the corner balance.

Corner balance isn't that sensitive on a big car like this as long as you're in the ballpark you'll be fine, kind of a 'once a year' check imo unless it's convenient or if you're tearing the car apart and putting it back together.

[Var]

Originally Posted by strat61caster

Yes, if you adjust two adjacent corners of the car equally, i.e. front/rear or left/right it should have negligible to zero impact on the corner balance.

Corner balance isn't that sensitive on a big car like this as long as you're in the ballpark you'll be fine, kind of a 'once a year' check imo unless it's convenient or if you're tearing the car apart and putting it back together.

On my Miata, the car was basically undriveable until after a corner balance. I thought my coilovers were blown after I installed them. It would understeer going right and oversteer going left. The car was aligned multiple times. God that was such a headache.

Good to know it won't be as sensitive on this car

[CSG Mike]

Originally Posted by Var

Is it worth corner balancing a car if you're going to be adjusting rake and ride height after the fact?

Has anyone just carefully adjusted their ride height at all corners and gotten remotely close cross weights?

The two should be done simultaneously.

[WVAsphalt]

I'm experiencing what I think is very excessive body roll. KW V3's, 6kF/7kR, ride height is 13 1/4" from hub center to wheel arch, 215/45r17 Nexen SUR4's, whiteline bolts with -2.5F/-2.3R (as much camber in the front as I could get, no rear correction) 0 toe. What would be the best way to reduce this? Stiffer springs, sway bars, or have I lowered the car too much? Picture from deal's gap for reference, I don't have any pictures from track days.

Sent from my SM-N950U using Tapatalk

[cjd]

Originally Posted by WVAsphalt

I'm experiencing what I think is very excessive body roll. KW V3's, 6kF/7kR, ride height is 13 1/4" from hub center to wheel arch, 215/45r17 Nexen SUR4's, whiteline bolts with -2.5F/-2.3R (as much camber in the front as I could get, no rear correction) 0 toe. What would be the best way to reduce this? Stiffer springs, sway bars, or have I lowered the car too much? Picture from deal's gap for reference, I don't have any pictures from track days.

Sent from my SM-N950U using Tapatalk

Excessive by what measure? What's the handling characteristic you want to change?

[WVAsphalt]

The car actually feels fairly neutral in steady state cornering; slightly understeer biased, which I suspect could be aided by more front camber. When the car has taken a set to one side, and transitions back to the other side, there is a lot of body movement that I think is detrimental. I also feel like I'm reaching the point in the front camber curve where it starts to go positive. Maybe I'm wrong.

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[H1C]

Originally Posted by Racecomp Engineering

Also, I'm finalizing the set up guide document but thought I'd post some quick tips here:


....

Ride height
If you set the front spring perch at 50 mm from bottom and the rear perch 90 mm from bottom, you should be near a 25 mm (or 1 inch) drop. All cars are different and also the drivers rear is usually a little lower, so it will take some fine tuning. A 25 mm drop is the recommended starting point. However, there is a lot of travel and we've run these lower with good results. A little bit of forward rake can also be helpful for some users.


.....

Andrew, I didn't want to clutter up your Superstreet-1 thread so I thought I'd ask here: do you know why most Twins' LR corner sits lower than the RR? I've never corner balanced; I just measured the threads on the shock bodies and set them equal L to R.



I always thought it was because of my uneven garage floor, but then I noticed that the RR corner always looks a bit higher no matter the surface. I haven't gotten around to correcting it, but I've spent a bit of time looking at my top mounts to see if they were somehow different from side to side -- so I found it interesting that you've observed this rear height discrepancy in many Twins.

[Racecomp Engineering]

Originally Posted by H1C

Andrew, I didn't want to clutter up your Superstreet-1 thread so I thought I'd ask here: do you know why most Twins' LR corner sits lower than the RR? I've never corner balanced; I just measured the threads on the shock bodies and set them equal L to R.



I always thought it was because of my uneven garage floor, but then I noticed that the RR corner always looks a bit higher no matter the surface. I haven't gotten around to correcting it, but I've spent a bit of time looking at my top mounts to see if they were somehow different from side to side -- so I found it interesting that you've observed this rear height discrepancy in many Twins.

Not just most twins, most Subarus! I haven't looked too much into it but IIRC the weight distribution isn't perfectly even in the back.

- andrew

[wparsons]

Originally Posted by Var

Is it worth corner balancing a car if you're going to be adjusting rake and ride height after the fact?

Has anyone just carefully adjusted their ride height at all corners and gotten remotely close cross weights?

Total waste of time to corner balance it if you're going to adjust the ride height or rake right after.


Even ride height != even cross weights, so you'll need scales (or a lot of luck) to get them close.

[Shadotracker]

What is the length of the oem strut compared to the KW v3? I've been looking online and the forums and haven't found anything solid as to the OEM strut length measurement.