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

[H1C]

Originally Posted by new2subaru

Maybe they were out of B6's

Haha maybe. He did repeatedly say B6's were designed for the OEM spring only, and that: 1) there was a chance, however small, that a shorter-than-OEM spring would not remain fully captive and seated on the B6; and 2) that I'd be giving up some compression travel using the B6 with a shorter spring vs. using the B8 with that same spring.

I never found the RCE Tarmac/B8 combo to have a lack of droop. I wish my current setup had anywhere near the amount of the droop that the Tarmacs & B8s have.

[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!

[Racecomp Engineering]

Originally Posted by H1C

1) there was a chance, however small, that a shorter-than-OEM spring would not remain fully captive and seated on the B6; and 2) that I'd be giving up some compression travel using the B6 with a shorter spring vs. using the B8 with that same spring.

Keeping them captive on B8s isn't an issue with our springs (or most out there).

Compression travel should be the same unless the B8 has a shorter bumpstop.

- Andrew

[Racecomp Engineering]

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!

This sounds very much like many motorsports oriented coilover.s

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

[H1C]

Originally Posted by Racecomp Engineering

This sounds very much like many motorsports oriented coilover.s

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

Thanks for your reply Andrew!

The coilovers are MCS 1-ways; I found them used in the member classifieds here for a great deal. The adjustment instructions say that they're "adjustable in rebound and the compression forces will adjust in proportion while adjusting rebound." I don't think I've ever seen a dyno for any MCS shock.

I tried increasing the rebound in front, but it didn't seem to eliminate the occasional bobbing. I think it made the oscillations smaller in amplitude and maybe less frequent, but they were still there.

I did order some helpers and divider spacers to be able to lower the front a bit more, along with spring isolators for all 4 corners. The rear springs are 7 inches long and have plenty of room to lower before they'd not remain captive at full droop.

I thought the bobbing might be because of some binding at the caster pivot point on the front LCA. But if this is common behavior in these kinds of shocks, I'm not too concerned about it. It doesn't happen that often, although it's sometimes funny when it occurs at night. I kind of feel like an LA lowrider, when I see my headlights bobbing up and down off the car in front.

Thanks!

[Racecomp Engineering]

Originally Posted by H1C

Thanks for your reply Andrew!

The coilovers are MCS 1-ways; I found them used in the member classifieds here for a great deal. The adjustment instructions say that they're "adjustable in rebound and the compression forces will adjust in proportion while adjusting rebound." I don't think I've ever seen a dyno for any MCS shock.

I tried increasing the rebound in front, but it didn't seem to eliminate the occasional bobbing. I think it made the oscillations smaller in amplitude and maybe less frequent, but they were still there.

I did order some helpers and divider spacers to be able to lower the front a bit more, along with spring isolators for all 4 corners. The rear springs are 7 inches long and have plenty of room to lower before they'd not remain captive at full droop.

I thought the bobbing might be because of some binding at the caster pivot point on the front LCA. But if this is common behavior in these kinds of shocks, I'm not too concerned about it. It doesn't happen that often, although it's sometimes funny when it occurs at night. I kind of feel like an LA lowrider, when I see my headlights bobbing up and down off the car in front.

Thanks!

Good job on the helpers. Dunno why some companies don't include them on single height adjustable coilovers.

I'd at least try reducing the damping and see how it feels. A dyno would really help diagnose that, but it can just be one of the tradeoffs for one of these types of dampers. Some handle it better/differently than others but overall it sounds like you're in good shape.

- Andrew

[H1C]

Originally Posted by Racecomp Engineering

Good job on the helpers. Dunno why some companies don't include them on single height adjustable coilovers.

I'd at least try reducing the damping and see how it feels. A dyno would really help diagnose that, but it can just be one of the tradeoffs for one of these types of dampers. Some handle it better/differently than others but overall it sounds like you're in good shape.

- Andrew

I think the previous owner put the spring/damper package together himself, having bought only the shocks from MCS.

I'll try reducing the damping in front -- I think I currently have the front set at 10/18 and the rears at 8/18 clicks from full soft. The instructions suggest 8/18 clicks from full soft as the starting point.

Thanks for the suggestion!

[bhmax]

Originally Posted by H1C

What's odd is that on relatively smooth pavement, I sometimes but not always get a bobbing or jiggling at the nose.

Curious, did you not get this at all with the Tarmac/B8 setup? I seemed to with Tarmac/B6. After watching some YouTube vids on “flat ride,” I wondered if maybe it was the relative frequencies front vs rear causing it. The car even got into some pretty crazy oscillations over certain bridges. I changed to Swift SpecR springs(softer front, stiffer rear) and it seemed to improve a lot.

[H1C]

Curious, did you not get this at all with the Tarmac/B8 setup? I seemed to with Tarmac/B6. After watching some YouTube vids on “flat ride,” I wondered if maybe it was the relative frequencies front vs rear causing it. The car even got into some pretty crazy oscillations over certain bridges. I changed to Swift SpecR springs(softer front, stiffer rear) and it seemed to improve a lot.

Hmm I can't say that I noticed it with the Tarmacs/B8s. But it's certainly possible that I'm just not that perceptive. I also had OEM top mounts and adjustable front LCAs with spherical bearings with that set-up. Maybe those dampened the transmission of suspension movement to the cabin a bit more than my current camber plates and OEM LCAs do.

Very interesting data point about softer front and stiffer rear spring rates helping quell your bobbing a lot. I watched some of Fat Cat Motorsport's YouTube videos a while back -- I remember he talked about flat ride and relative frequencies. Maybe I need to revisit those videos and try swapping my springs front to rear and see if that completely gets rid of my jiggling.

[Racecomp Engineering]

I was going to mention flat ride. You are running a front biased set-up, but that is not the issue here. That kind of pitching is noticeable with very soft dampers but you're not going to notice it with MCS.

The valving is identical on B6 and B8, so I'm not sure what was causing it for bhmax. It's a pretty common set-up and one that I really like.

- Andrew

[H1C]

Originally Posted by Racecomp Engineering

I was going to mention flat ride. You are running a front biased set-up, but I don't think that's the issue here for sure. That kind of pitching is noticeable with very soft dampers but you're not going to notice it with MCS.

The valving is identical on B6 and B8, so I'm not sure what was causing it for bhmax. It's a pretty common set-up and one that I really like.

- Andrew

Andrew, to clarify: do you think, with certainty, that the front-biased setup is not the cause here? Or do you not think that the front-biased setup is, with certainty, the cause here? But that it still may be the cause, or a contributing factor?

The "don't think" and the "for sure" in your statement leave room for what logicians like to call a "scope ambiguity." Sorry for the nerdy interlude; I went to grad school for analytic philosophy.

[Racecomp Engineering]

Originally Posted by H1C

Andrew, to clarify: do you think, with certainty, that the front-biased setup is not the cause here? Or do you not think that the front-biased setup is, with certainty, the cause here? But that it still may be the cause, or a contributing factor?

The "don't think" and the "for sure" in your statement leave room for what logicians like to call a "scope ambiguity." Sorry for the nerdy interlude; I went to grad school for analytic philosophy.

Haha sorry about that. The spring rates are not the cause.

I've felt the same thing on a variety of cars and with a variety of spring rate biases on the same car. The unifying factor is a motorsports oriented coilover (and yes I've felt it on different brands to varying degrees) with a lot low speed compression and gas pressure.

EDIT: but I personally would consider changing the springs because I think that may be a little too understeer biased for some especially with your bigger front bar. Different issue though and you should test what you have first before making changes. That one does have some personal preference.

- Andrew

[H1C]

Originally Posted by Racecomp Engineering

Haha sorry about that. The spring rates are not the cause.

I've felt the same thing on a variety of cars and with a variety of spring rate biases on the same car. The unifying factor is a motorsports oriented coilover (and yes I've felt it on different brands to varying degrees) with a lot low speed compression and gas pressure.

EDIT: but I personally would consider changing the springs because I think that may be a little too understeer biased for some especially with your bigger front bar. Different issue though and you should test what you have first before making changes. That one does have some personal preference.

- Andrew

Thanks for the clarification I'll try the 500 in F, 450 R for at least one event before deciding whether to swap them F to R. I primarily auto-x and do track days only occasionally, without any concern for lap times, so I've found that somewhat of a front bias is good for slaloms and for stability in sweepers while being able to get back on the gas sooner.

Currently it doesn't feel too stiff in front relative to the rear -- unlike when I had the Hotchkis 25 mm bar on for about a week with the Tarmacs/B8s. That bar made the front unbearably stiff and pushy, and very noticeable even on the street.

[Racecomp Engineering]

Originally Posted by H1C

Thanks for the clarification I'll try the 500 in F, 450 R for at least one event before deciding whether to swap them F to R. I primarily auto-x and do track days only occasionally, without any concern for lap times, so I've found that somewhat of a front bias is good for slaloms and for stability in sweepers while being able to get back on the gas sooner.

Currently it doesn't feel too stiff in front relative to the rear -- unlike when I had the Hotchkis 25 mm bar on for about a week with the Tarmacs/B8s. That was unbearably stiff and pushy, and very noticeable even on the street.

Gotcha, yes for auto-x you're in good shape.

- Andrew