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

[grippgoat]

https://www.ft86club.com/forums/show...IjLTDBVcXYz9NQ

That was the setup on my 2023 BRZ when I bought it.

Previous owner was towing to the track, and the front camber is that aggressive because it was (and possibly still is?) heavily wearing the outside of the front tire on track.

There's a mod list at the start of that thread, but the highlights w.r.t. setup/alignment are: MCS 2-way non-remote 450f/550r, full droop is about 14.5" front, and ride height is about 12.9". Cusco rear upper control arms and SPL rear toe links. Perrin swaybars (22mm front, 19mm rear I think?) with adjustable endlinks. Camber plates are about half way to full negative from center (and more asymmetrical than I'd like), and I think it's got the stock 14mm bolts top and bottom at the knuckle.

I'm going to be driving to/from the track, and doing some street hooning.
I don't love the way it drives. It grips for days in the corners, but it doesn't want to go straight. It's extremely darty, and there is basically no self-centering in the steering. Low speed traction (like pulling out of driveways / turning from stop signs) is abysmal, although I think that might be tires + weather more than setup. The tracks I plan to hit are a 1.5 and 3hr drive, and frankly I wouldn't feel safe driving this setup on a highway, especially when tired after a long day. I also suspect it'd be really bad in the rain.

I'm looking for setup advice to dial it back a bit, but still work well on track. Some specific things I'm wondering:
- I've mostly driven on the stock wheels... Could the extreme camber + high offset stock wheels be moving the contact patch inboard of the steering axis, so that kingpin angle is actually causing a de-centering force?
- Am I low enough to be getting into camber loss and bad roll center behavior, and could that be why the car needs so much camber?
- Can I actually go much higher without running out of droop travel?
- How much caster is too much on these cars? I can go from 6* to 7* by going to a different set of holes on the Karcepts camber plates. Is the old Impreza trick of swapping the plates to the opposite side of the car and rotating them a thing on this platform?
- Would a couple more degrees of caster actually get me enough extra mid-corner camber to let me give up some static?

I have many more questions, but I think that's enough for now. 😅

-Mike

[Racecomp Engineering]

Originally Posted by grippgoat

That was the setup on my 2023 BRZ when I bought it.

That's a pretty aggressive setup! A lot of parts.

What kind of tires are you using?

I do think the camber you're running is responsible for that particular steering feel, though I'm not entirely sure why. I could be wrong.

Yes you're pretty low without roll center correction, but that's plenty of camber and front roll resistance.

It looks like those coilovers are designed to be run pretty low and I would be concerned about running out of droop travel if you increased ride height to say 25mm less than stock (or ~13.5 inches). But even just a little more ride height (10mm maybe) would go a long way IMO and still be OKAY.

You shouldn't need 7 degrees of caster. I know Myles did run around that much on our 1st shop car, but 6 is still plenty.

- Andrew

[strat61caster]

@grippgoat dial back to -3F and -2R camber, you will sacrifice grip on track as well as get more outside edge wear but gain stability on freeway. I’ve been there before and I think this is the good aggressive/street compromise.

I’m currently at -4.3F and -2.5R and some toe out in front and similar rear toe. More caster won’t affect much imho, steering will feel a touch heavier and that’s about it. If you had less rear toe in I’d suggest that but you’ve already got quite a bit, that’s usually at fault for highway wandering in my experience. Zero toe front doesn’t usually result in bad street manners.

Some toe in front may help on center freeway stability, it’s been a long time since I tried that but I recall I thought it made the car a little numb in the corners. Changing wheel offsets and width won’t really help (I swap between oe and 17x9 regularly, tire makes a bigger difference), you’re just riding on the inside edge and thus more susceptible to road conditions, i can really really feel it turning on wet painted lines, the front will basically lose all traction for two or three inches while the rear end pushes you forward lol.

I’ve tried most combos of -1:-4F and -1:-3R camber and various toe settings, I really think you’re feeling the camber and at least without doing some incommon geometry stuff the easiest fix is to just dial it back. Good luck, welcome to tracking strut based suspension cars.

Edit: caster plates going from -6 to -7 made the steering feel a little heavier, I didn’t notice any performance gain or change in street manners. Data may show improvement, but the butt dyno couldn’t tell.

Edit2: I’ve found ride heights to have no impact on alignment needs, car feels better lower in my experience. Some people go up past -5 degrees, it’s just the nature of this suspension design.

[marco_mc22]

Originally Posted by grippgoat

https://www.ft86club.com/forums/show...IjLTDBVcXYz9NQ

That was the setup on my 2023 BRZ when I bought it.

Previous owner was towing to the track, and the front camber is that aggressive because it was (and possibly still is?) heavily wearing the outside of the front tire on track.

There's a mod list at the start of that thread, but the highlights w.r.t. setup/alignment are: MCS 2-way non-remote 450f/550r, full droop is about 14.5" front, and ride height is about 12.9". Cusco rear upper control arms and SPL rear toe links. Perrin swaybars (22mm front, 19mm rear I think?) with adjustable endlinks. Camber plates are about half way to full negative from center (and more asymmetrical than I'd like), and I think it's got the stock 14mm bolts top and bottom at the knuckle.

I'm going to be driving to/from the track, and doing some street hooning.
I don't love the way it drives. It grips for days in the corners, but it doesn't want to go straight. It's extremely darty, and there is basically no self-centering in the steering. Low speed traction (like pulling out of driveways / turning from stop signs) is abysmal, although I think that might be tires + weather more than setup. The tracks I plan to hit are a 1.5 and 3hr drive, and frankly I wouldn't feel safe driving this setup on a highway, especially when tired after a long day. I also suspect it'd be really bad in the rain.

I'm looking for setup advice to dial it back a bit, but still work well on track. Some specific things I'm wondering:
- I've mostly driven on the stock wheels... Could the extreme camber + high offset stock wheels be moving the contact patch inboard of the steering axis, so that kingpin angle is actually causing a de-centering force?
- Am I low enough to be getting into camber loss and bad roll center behavior, and could that be why the car needs so much camber?
- Can I actually go much higher without running out of droop travel?
- How much caster is too much on these cars? I can go from 6* to 7* by going to a different set of holes on the Karcepts camber plates. Is the old Impreza trick of swapping the plates to the opposite side of the car and rotating them a thing on this platform?
- Would a couple more degrees of caster actually get me enough extra mid-corner camber to let me give up some static?

I have many more questions, but I think that's enough for now. ��

-Mike

To answer your questions:

1) Yep, high offset wheels made your scrub radius lower, this leads to a precise steering feel with less dynamic toe changes under hard braking and a more forgiving steering. Anyway it should not give you a de-centering force, which is in my opinion caused by all that camber: tons of camber make the steering less precise at low speed with less self centering force, the front of the car is like driving the Titanic between the icebergs, that is normal. To check for a reduced self centering force just do some drifting or donuts, it is a better way to me.

2) Yes you are, anyway with that specific setup and those beefy bars + stiff springs this is less than a problem to me......and no, these cars do need all that camber to work, pretty much as any other strut equipped car like Bmw's or Porsche.

3) Ask MCS to be 100% sure of the correct ride height range, then decide which is your ideal ratio, bump biased for the track and the opposite for the road.

4) Yep, rotating your plates and switching the left one to the right and viceversa would usually give you around 7-7.5 degrees depending on the plates. In my opinion +7 is a good compromise, I like the heavier steering feel plus this would give you a better geometry if you have increased camber and SAI. I would not use more than +8.

5) No, no matter how much caster you will use, these cars as said before need lot of camber, with good tires and a decent setup -3 to -5 is the spot to be fast.

That said, I'd dial back some camber, spring rate and relative to your tire choice you may also consider to keep those huge bars or remove them. The actual car is just too much for the road and keep in mind that to remove all the wandering you have described you shall use soft springs, soft bars and toe in on both front and rear axles, all performance decreasing mods, you can minimize wandering and tramlining but not completely get rid of it if you want a sport car

[grippgoat]

Originally Posted by Racecomp Engineering

What kind of tires are you using?

I have:
- Used Falken RT-660s on the stock rims in 225/45/17.
- 17x9 +35 with brand new sticker Hankook Z214 in 245/40/17 for the front, and 17x9 +42 with used Z214 in 245/40/17 for the rear.
- 17x9 +35 front / +42 rear with used Goodyear SuperCar 3R in 245/40/17.
- 17x9 +35 with brand new SC3R in 245/40/17 as spare fronts (previous owner liked to keep spare fronts, because they wore out much faster).

I don't have:
- Anything that's truly good in the wet.

I haven't decided yet if I should run the sticky tires, or just try and sell them to get something else. I'd like to sell at least the +35 rims, too, because I want to be able to rotate front to rear.

I'm trying not to buy tires yet, though. Budget is a bit strapped, and I still need a new helmet.

Originally Posted by Racecomp Engineering

Yes you're pretty low without roll center correction, but that's plenty of camber and front roll resistance.

I really want roll center correction, but whiteline says their 1st gen kit doesn't work on the second gen, and their second gen kit is still in R&D. I don't know why their first gen kit doesn't work, though. I've seen a youtuber with a second gen that had it installed. ¯\_(ツ)_/¯

I haven't found any other bolt-in options yet. The Buddy Club extended balljoints require modification. Hard Race has some that they don't give much info on, and I suspect it's a carry-over 1st gen part similar to the buddy club, and may or may not actually work or require modification.

Originally Posted by Racecomp Engineering

It looks like those coilovers are designed to be run pretty low and I would be concerned about running out of droop travel if you increased ride height to say 25mm less than stock (or ~13.5 inches). But even just a little more ride height (10mm maybe) would go a long way IMO and still be OKAY.

Yeah, I was thinking of raising to 13.25 or 13.5. I guess I'll give it a shot and see what it does. If I start lifting the inside front, it's not gonna be good.

Originally Posted by Racecomp Engineering

You shouldn't need 7 degrees of caster. I know Myles did run around that much on our 1st shop car, but 6 is still plenty.

- Andrew

I mean, I have the parts to get more, so I might as well try it?

Thanks for the response!

Originally Posted by strat61caster

@grippgoat dial back to -3F and -2R camber, you will sacrifice grip on track as well as get more outside edge wear but gain stability on freeway. I’ve been there before and I think this is the good aggressive/street compromise.

That's about what I was thinking. I've seen some driven-to-the-track 1st gens online running like 3 to 3.5 in front and still going fast.

Thanks for the reply! I read the rest of it, but didn't have anything to say in response, so didn't quote it.

Originally Posted by marco_mc22

1) Yep, high offset wheels made your scrub radius lower, this leads to a precise steering feel with less dynamic toe changes under hard braking and a more forgiving steering. Anyway it should not give you a de-centering force, which is in my opinion caused by all that camber: tons of camber make the steering less precise at low speed with less self centering force, the front of the car is like driving the Titanic between the icebergs, that is normal. To check for a reduced self centering force just do some drifting or donuts, it is a better way to me.

In thinking about this, I went back and re-read the MotoIQ suspension guide part 8 on caster and kingpin angle to refresh my memory.

Kingpin angle causes the wheel to move in an upside-down arc with the high point in the middle, when the steering is centered. The wheel wants to be at that high point, thus self-centering force. This effect is increased the further outboard the contact patch is from the point where the steering axis intersects the ground. The article doesn't go into it, but it makes sense in my head that if the center of the contact patch is actually inboard of where the steering axis intersects the ground, you'd get the opposite arc, with high points on the ends at full lock, and a low point in the middle and the tire would want to fall away from that mid point.

Having a lot of camber would move the contact patch substantially inboard when going in a straight line, or turning at low Gs. How much, I don't know exactly. Then increasing camber with camber plates increases kingpin angle, moving the steering axis to ground intersection point outwards.

I've seen Subaru market "negative scrub radius geometry" in some models. although I don't specifically know where the BRZ sits. If the starting point is already close to or below zero, then I could see the setup changes sending it off to Narnia.

As far as testing it, the most I've done is let go of the wheel in a tight parking garage with a concrete floor. There was basically zero self-centering. That's obviously not indicative of what it would do at 1G+ in a high-speed turn, but I'll deal with that later when I actually get to the track.

Originally Posted by marco_mc22

2) Yes you are, anyway with that specific setup and those beefy bars + stiff springs this is less than a problem to me......and no, these cars do need all that camber to work, pretty much as any other strut equipped car like Bmw's or Porsche.

I actually don't think the previous owner tracked the car with the full swaybar setup. I have to go back and check his build thread again. I may actually go back to stock, to just reduce the number of variables going on.

Originally Posted by marco_mc22

3) Ask MCS to be 100% sure of the correct ride height range, then decide which is your ideal ratio, bump biased for the track and the opposite for the road.

I will contact them (Karcepts, who specced them). The ride height, alignment, and damping is all spot on to the baseline setup included in their instructions. Although it's not clear to me whether that setup is specific to gen2, and whether that matters.

Originally Posted by marco_mc22

4) Yep, rotating your plates and switching the left one to the right and viceversa would usually give you around 7-7.5 degrees depending on the plates. In my opinion +7 is a good compromise, I like the heavier steering feel plus this would give you a better geometry if you have increased camber and SAI. I would not use more than +8.

Thanks. I think I'll give that a shot.

Originally Posted by marco_mc22

5) No, no matter how much caster you will use, these cars as said before need lot of camber, with good tires and a decent setup -3 to -5 is the spot to be fast.

Originally Posted by marco_mc22

That said, I'd dial back some camber, spring rate and relative to your tire choice you may also consider to keep those huge bars or remove them. The actual car is just too much for the road and keep in mind that to remove all the wandering you have described you shall use soft springs, soft bars and toe in on both front and rear axles, all performance decreasing mods, you can minimize wandering and tramlining but not completely get rid of it if you want a sport car

Any suggestions on spring rates? The front doesn't seem too high compared to a lot of weekend warrior type setups I've seen (often 7-8kg front, which is 400-450 lb/in), but the rears do seem quite a bit higher than anything I've seen online (550 lb/in = 9.8 kg/mm).

Thanks for your response!

-Mike

[Code Monkey]

I drive 6 hours from Atlanta to VIR with -4.6 camber (about to become -4.8) with zero issues...

[grippgoat]

Originally Posted by Code Monkey

I drive 6 hours from Atlanta to VIR with -4.6 camber (about to become -4.8) with zero issues...

What tires? Have you done it in the wet? In the dark? In the dark and wet?
How much Red Bull? How old are you? lol.

If it doesn't give you abnormal wear on the inside if your tires, though, that's at least a good data point.

-Mike

[Code Monkey]

Kumho Ecsta V730, 255 width, no rain.

Got caught up in pouring rain coming home from Barber, -3.5 camber and 3 people in the car, no problems at all.

The only time when the car felt squirmy was in my 2017 BRZ on Pirelli Trofeo R (225 width, -3.6 camber or so) when I drove in pouring rain. Had a few wtf moments, but kept all the inputs slow and gentle, and after a few minutes was passing all the traffic.

[grippgoat]

Originally Posted by Code Monkey

Kumho Ecsta V730, 255 width, no rain.

Got caught up in pouring rain coming home from Barber, -3.5 camber and 3 people in the car, no problems at all.

The only time when the car felt squirmy was in my 2017 BRZ on Pirelli Trofeo R (225 width, -3.6 camber or so) when I drove in pouring rain. Had a few wtf moments, but kept all the inputs slow and gentle, and after a few minutes was passing all the traffic.

Thx. I can keep an unruly car on the road when I'm alert. My concern is more about things like not seeing a pothole in time (40-something eyesight sadness), or just losing focus for a few seconds when it's dark, and wet, and a boring stretch of road, at midnight when I'm super tired after a long tiring day at the track, and my neck and eyes are getting tired from jiggling on a stiff suspension.

-Mike

[Wangspeed]

Originally Posted by grippgoat

https://www.ft86club.com/forums/show...IjLTDBVcXYz9NQ

That was the setup on my 2023 BRZ when I bought it.

Previous owner was towing to the track, and the front camber is that aggressive because it was (and possibly still is?) heavily wearing the outside of the front tire on track.

There's a mod list at the start of that thread, but the highlights w.r.t. setup/alignment are: MCS 2-way non-remote 450f/550r, full droop is about 14.5" front, and ride height is about 12.9". Cusco rear upper control arms and SPL rear toe links. Perrin swaybars (22mm front, 19mm rear I think?) with adjustable endlinks. Camber plates are about half way to full negative from center (and more asymmetrical than I'd like), and I think it's got the stock 14mm bolts top and bottom at the knuckle.

I'm going to be driving to/from the track, and doing some street hooning.
I don't love the way it drives. It grips for days in the corners, but it doesn't want to go straight. It's extremely darty, and there is basically no self-centering in the steering. Low speed traction (like pulling out of driveways / turning from stop signs) is abysmal, although I think that might be tires + weather more than setup. The tracks I plan to hit are a 1.5 and 3hr drive, and frankly I wouldn't feel safe driving this setup on a highway, especially when tired after a long day. I also suspect it'd be really bad in the rain.

I'm looking for setup advice to dial it back a bit, but still work well on track. Some specific things I'm wondering:
- I've mostly driven on the stock wheels... Could the extreme camber + high offset stock wheels be moving the contact patch inboard of the steering axis, so that kingpin angle is actually causing a de-centering force?
- Am I low enough to be getting into camber loss and bad roll center behavior, and could that be why the car needs so much camber?
- Can I actually go much higher without running out of droop travel?
- How much caster is too much on these cars? I can go from 6* to 7* by going to a different set of holes on the Karcepts camber plates. Is the old Impreza trick of swapping the plates to the opposite side of the car and rotating them a thing on this platform?
- Would a couple more degrees of caster actually get me enough extra mid-corner camber to let me give up some static?

I have many more questions, but I think that's enough for now. 😅

-Mike

There's a lot here, and I'm short on time. I had some complaints about my Karcepts MCS 2WNR setup as well. 400F/500R springs. I couldn't get the car confidently settled in steady state cornering at less than track throttle. It was too easy for the rear to come around, especially over a hump or elevation change. Sharp bumps were handled better. It was setup by the previous owner to be aggressive on turn in, and rotate aggressively for autox. After about 6 months, I had a long convo with Brian at Karcepts, and we decided for me to step down to 400F/400R, which is what the previous owner originally had.


I also had the car aligned and corner balanced at the same time. The centering isn't great still, but it's good enough. The rear of the car feels better damped with 400/400 and settings that are sane for the street, and I don't notice too much of a decrease in rotation ability. Oh, I also set the ride heights to 13.25" front (center to fender) and 13.75" rear (center to fender). Front camber is -4.0, rear -2.4, toe zero. No change to caster, even though I have caster adjustable hats.

[M0nk3y]

Originally Posted by Wangspeed

There's a lot here, and I'm short on time. I had some complaints about my Karcepts MCS 2WNR setup as well. 400F/500R springs. I couldn't get the car confidently settled in steady state cornering at less than track throttle. It was too easy for the rear to come around, especially over a hump or elevation change. Sharp bumps were handled better. It was setup by the previous owner to be aggressive on turn in, and rotate aggressively for autox. After about 6 months, I had a long convo with Brian at Karcepts, and we decided for me to step down to 400F/400R, which is what the previous owner originally had.


I also had the car aligned and corner balanced at the same time. The centering isn't great still, but it's good enough. The rear of the car feels better damped with 400/400 and settings that are sane for the street, and I don't notice too much of a decrease in rotation ability. Oh, I also set the ride heights to 13.25" front (center to fender) and 13.75" rear (center to fender). Front camber is -4.0, rear -2.4, toe zero. No change to caster, even though I have caster adjustable hats.

I'm not sure why anyone feels the need to run Rake statically on these cars. They should be at most 1/4" of rake, but most likely 0" F/R

For me, I have Aero - but run at 1/4" of rake for off-throttle turn-in and then the downforce takes care of the car becoming neutral rake at speed. But a lot of the issues you're mentioning can easily be related to rake alone. Also 0 Toe...don't quite understand the logic behind that either especially if you're commenting on a non-confident setup

I'm 400/500 and TBH the car is miles better than my pervious setup of 400/350.

MCS 2-Way Remotes
-4.6 Front, 1/8th Toe out
-2.5 Rear, 1/16th total In

[marco_mc22]

Originally Posted by grippgoat

Any suggestions on spring rates? The front doesn't seem too high compared to a lot of weekend warrior type setups I've seen (often 7-8kg front, which is 400-450 lb/in), but the rears do seem quite a bit higher than anything I've seen online (550 lb/in = 9.8 kg/mm).

Thanks for your response!

-Mike

I'd stay between 5-7kg/mm on both axles for a dual duty 86 without aero, choose the balance between front and rear frequencies relative to your driving style and tastes, both Flat Ride and Pitch can work when tuned correctly.

For reference I really enjoyed 5K front 7K rear on both road and track, with 22mm front solid bar and no rear bar, 2mm toe out front and 2mm toe in rear and camber to suit tires. I also liked 7K square with 22mm FSB and OEM 15mm rear bar + more rake, more forgiving and faster in transitions for sure but less rotation e less steady state peak speed, it really depends on you

[Breezer]

Originally Posted by grippgoat

...MCS 2-way non-remote 450f/550r, full droop is about 14.5" front, and ride height is about 12.9"...
- Can I actually go much higher without running out of droop travel?...

Have you also measured droop on the strut shafts?
What are the stroke lengths of the MCS struts?
Are you also measuring ride height from level ground to the pinch weld at each lift point?
Measuring droop at the strut shaft and calculating as a percentage of overall stroke is more accurate and precise than relying on wheel to bodywork measures. I suggest one third of stroke as minimum droop for street use.
If raising ride height by increasing spring preload, then be sure the amount of preload doesn't detract from the spring's usable stroke enough to cause bind, otherwise you'll need a stiffer spring rate or longer spring. If droop/bump percentage is adequate, but you feel like you're still too low, then leveling spacers above the strut mounts can be added to address your roll center concerns.

[grippgoat]

Originally Posted by Breezer

Have you also measured droop on the strut shafts?

No. I haven't had them out of the car. And I don't think that's something I can measure without getting the spring off.

Originally Posted by Breezer

What are the stroke lengths of the MCS struts?

¯\_(ツ)_/¯

Originally Posted by Breezer

Are you also measuring ride height from level ground to the pinch weld at each lift point?

I did once out of curiosity, but that is harder to measure and not especially useful to me. Wheel center to fender is the internet standard, and most people, including me, don't have bent fenders. Modern manufacturing tolerances are pretty tight, and pinch welds can get damaged, too, so IMO it's a wash.

Originally Posted by Breezer

Measuring droop at the strut shaft and calculating as a percentage of overall stroke is more accurate and precise than relying on wheel to bodywork measures. I suggest one third of stroke as minimum droop for street use.
If raising ride height by increasing spring preload, then be sure the amount of preload doesn't detract from the spring's usable stroke enough to cause bind, otherwise you'll need a stiffer spring rate or longer spring. If droop/bump percentage is adequate, but you feel like you're still too low, then leveling spacers above the strut mounts can be added to address your roll center concerns.

I looked a bit closer today while I was making some camber adjustments. The helper (or is it tender?) spring is not quite coil bound at full droop, so it could probably go up like 1/4" without losing usable droop travel. I have a pair of 400lb springs coming, and will likely throw a strut in springless when I rearrange springs to look at full travel and camber curves, just to understand what's going on a bit better.

-Mike