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Options for adjustable coil springs with a real damper??
I usually like to shake down a new (to me) car before throwing aftermarket springs and dampers at it. But unfortunately the original rear shocks and springs are all done on my 72k 04 8. So I need replacements for now and will try to anticipate any further suspension upgrades in the future. My plans for the car are weekend driving with 4-5 track days a year. My level is intermediate running 200TW tires and maybe some XP8 pads. I have plenty of experience running Bilstein, Koni, Sachs and Ohlins dampers. My usual starting place would be Koni yellows with a GC coil over setup. However GC does not make a conversion for this car and for some reason Koni decided to go with twist adjust dampers in the rear. I could go straight to Ohlins DFV, but it seems like overkill without knowing what I want to tune into the chassis. So what are my options considering the following:
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Need at least adjustable spring preload at stock+ rates.
Need a quality damper, ideally one that is designed and made in Europe
I have ZERO interest in any of the cheap, colorful, no-name coilovers sold on ebay or other sites. No offense but this includes Tein, BC, stance and all the other cheapo stuff.
I am leaning to Bilstein PSS because of the price point but am open to other options for this platform
yeah, that jdm-yo stuff is typical forum talk from lesser experienced folks
I replied to your post in the racing section. There is a ton of information on here if you’ll take the time to look for and read through it. New threads aren’t really necessary.
I ended up going with PSS coilovers. Got them on sale for 1K. Hopefully the spring rates make sense for the RX8 platform. The rear bias may improve flat ride as well as gather a bit more rotation. I haven't had too much of a chance to push the car, but stock under all circumstances the front washes out every time. A rear biased spring setup may be just the ticket. If its too extreme I can always pull the rear sway bar. Once I get them installed, will let you know.
Not quite as exciting as when I opened my new ohlins, but there is still something about new suspension components. Very nice quality for the price. Hopefully they perform like they look.
In! Not too bad. For some reason I thought I could pull out the rear shock without unbolting any links. Yeah that didn’t work. Much easier releasing the two uppers. Next up to set ride height and alignment.
I set the ride height at about 13.75” front and rear. At this level the rear springs are at the max preload adjustment. The fronts are about 10mm from max preload. Street + alignment was done.
Quick review...
Ride- Can’t get much better with a traditional damper. Spring rates are very reasonable. Almost no bad ride characteristics, supple on all but the sharpest impacts. First time I installed dampers in my fun car and my wife did not comment negatively on the ride. I never really experienced the oem shocks in good condition but the pss ride seems at least as good.
Street Handling- Again, about as well balanced as it gets with a traditional damper. I would call it sport+ levels of damping. Very controlled at aggressive street speeds, but never abusive. Travel is well controlled up to about 8/10 level. Beyond that chassis movement starts to push on the damping level and uses a bit more travel. For some cars this could be an issue, but the rx8 seems like it has endless quality travel. Body roll is notable but still well controlled. The car is predictable, consistent, and exhibits no bad behaviors over even broken pavement. With this setup the car is silly easy to drive fast comfortably.
Track Handling- No track time yet, I will update ASAP. My predictions are this setup is a good match for the stock 500tw 225 tires I am running. Considering I am on stock pads, it’s a good overall match.
I do have concerns how far I can track this setup in the future. A 200tw 245 tire and a flat out track day could be too much for these dampers. Maybe augment with some sway bars would help. I will have to see, the camber and toe curves on this car seem excellent. I may have to just get used to more chassis movement during aggressive track driving. Not necessarily a bad thing.
I think that the rear "body roll/chassis movement" is built into the car's handling/setup from factory. Hipermax coilovers and rb sway bar in the rear, never got rid of it completely. With oem suspension, it was even more pronounced though.
Yep. Body roll is a function of Cg and roll center relationships while dampers and sway bars control wheel movement. You can stiffen things so that the body can't roll, but you're also restricting wheel movement by solving that problem that way so there's a point of diminishing returns. On your average sedan the toe and camber changes with compression aren't a design priority, so you have no choice but to stiffen until you find some acceptable middle ground, but here there's no real point in stiffening it beyond tuning out the comfort and safety margins. Beyond that you're tuning for 2nd order characterisrics that have to do with how fast the body moves in turn-in and turn exit rather than how much.
You can try to lower it a bit more, but IMO below about 13" things start to get weird (as well as scrapy). Some of the fastest folks here run without a rear bar at all.
It takes some getting used to. Its weird moving through so much travel without anything negative happening, especially with the rear suspension. Most of my previous cars either come into the bump stops, spike the rear spring rate and upset stability. Or on full compression or rebound you get massive toe changes that you need to correct for with wheel inputs. Usually the solution is to setup your rear toe curve at ride height and just limit travel. I was running 670lbs spring on the rear of the S2k, and it still rode pretty decent. The spring rate was needed to stay off the bump stops and to avoid going into no mans land with toe control.
I remember pulling the wheel off for the first time on the RX8, looking at all the links and thinking WTF.
So I was able to get a couple of track sessions in at TSMP. Its been a while since I tracked there, but with the RX8, I was able to get up to speed pretty quickly. Last time I was there I had a S2k with Ohlins and BFG Rivals. Compared to that setup the RX8 drives.... safe. Its hard to put a wheel wrong with this car. Similar to the street, there was significant body motion, especially roll. This is with a set of old 500tw tires. Running about -1.5* camber in the front, I consistently rolled onto the edge of the front tire. The rear was not as bad but I have -2 back there. With even a decent tire upgrade I will need to make some suspension changes. On the positive note, while the damping and spring rates facilitated lots of wheel travel, nothing negative came from it. I never bottomed or spiked the bump stops. I could drop a wheel or hit curbing with no issues. Trail braking into tight corners promoted good rotation but never any oversteer. The current setup is very safe and easy to drive at its limit.
Bottom line is the PSS are perfect for the street but less so for the track as the car is setup now. Obviously some front camber will help, but if I move to a 200TW 245 tire, I will need make changes. Having experience with the DFV, I know they are a safe bet, just not sure I want to drop the cash. I usually tune with spring rates, but maybe a stiffer set of bars would help PSS setup I have now.
Yep the front edge rolling is a thing, ans I'm not sure more suspension will fix it (without making the front independent suspension more dependent). I'd suggest instead to solve this with more camber. 1.5 is nothing, try to get it to 2.5 with offset bearings if you can.
06-02-2021, 03:28 PM
