Handling: Camber Attainable with Struts. Your Experiences?

[skeeler]

I'm not worried about the power and torque. 197 BHP and 151 lb-ft should be plenty, depending on gearing. The high rev limit should be a boon to autocrossing, again, depending on gearing.

Speaking of autocross, I'm more concerned with handling than power. The weight is lower than any other 4-seat RWD car that I know of, which is the main reason I'm considering this for my family car. The low center of mass is very exciting.

The only concern I have with the car is the front McPherson struts. All my Miatas have had double wishbones up front, and those cars would give over 2 degrees of negative camber without camber links, camber plates, or any other nonsense. Plus, they give camber gain under compression. I know that some strut-equipped cars, BMWs in particular, are camber-challenged; they have limited static camber and poor camber curves. Stuts often give camber loss, rather than camber gain, as the suspension compresses. The drivers I know who autocross Bimmers in Stock classes or in Street Touring classes frequently complain about not being able to get enough camber.

Fortunately, I don't seem to hear this complaint as much from the folks racing WRXs and STIs, though the grip offered by AWD may be mitigating the problem in their cases. So, can anyone comment on how much negative camber one can achieve in the front of other Subarus? Also, what are the camber curves like? Do you see much camber loss? How about with aftermarket dampers and springs that lower the car dramatically?

[switchlanez]

Originally Posted by skeeler

I'm not worried about the power and torque. 197 BHP and 151 lb-ft should be plenty, depending on gearing. The high rev limit should be a boon to autocrossing, again, depending on gearing.

Speaking of autocross, I'm more concerned with handling than power. The weight is lower than any other 4-seat RWD car that I know of, which is the main reason I'm considering this for my family car. The low center of mass is very exciting.

The only concern I have with the car is the front McPherson struts. All my Miatas have had double wishbones up front, and those cars would give over 2 degrees of negative camber without camber links, camber plates, or any other nonsense. Plus, they give camber gain under compression. I know that some strut-equipped cars, BMWs in particular, are camber-challenged; they have limited static camber and poor camber curves. Stuts often give camber loss, rather than camber gain, as the suspension compresses. The drivers I know who autocross Bimmers in Stock classes or in Street Touring classes frequently complain about not being able to get enough camber.

Fortunately, I don't seem to hear this complaint as much from the folks racing WRXs and STIs, though the grip offered by AWD may be mitigating the problem in their cases. So, can anyone comment on how much negative camber one can achieve in the front of other Subarus? Also, what are the camber curves like? Do you see much camber loss? How about with aftermarket dampers and springs that lower the car dramatically?

I deduce that a MacPherson setup takes up more vertical space and double-wishbone takes up more lateral space. MacPhersons free up space below the engine so it can sit lower for a lower CoG (handling gain); that probably can't be designed with double-wishbones.

[skeeler]

Originally Posted by skeeler

The only concern I have with the car is the front McPherson struts.

I should mention that I realize the great width of the boxer design necessitates McPherson struts, so these struts are a direct result of the low center of mass.

[Allch Chcar]

I looked into it some and you can get around 3 degrees of camber with a plate on the front suspension. Have to wait for the Subaru/BMW guys to chime in for any facts.

[skeeler]

Originally Posted by Allch Chcar

I looked into it some and you can get around 3 degrees of camber with a plate on the front suspension.

Where'd you get this number?

[Allch Chcar]

Originally Posted by skeeler

Where'd you get this number?

I'm glad you asked because I was reading up on Mustang suspension recently so I might have confused which car I was thinking about with that. Hold on and let me check.

[Dave-ROR]

Originally Posted by switchlanez

I deduce that a MacPherson setup takes up more vertical space and double-wishbone takes up more lateral space. MacPhersons free up space below the engine so it can sit lower for a lower CoG (handling gain); that probably can't be designed with double-wishbones.

Sure you can. The car uses Mac Struts for packaging (fitment with the wide engine), cost, and it's what subaru knows.

Skeeler: Unfortunately, I've been double wishbone all around for years, so I need to relearn mac strut junk myself so I'm no help on this one currently.

[Dave-ROR]

Originally Posted by skeeler

Where'd you get this number?

It doesn't matter if you plan on running stock, unless that's allowed? I didn't think it was?

Anyways, how much actual space we can get depends on the car. I think the old RX7 race car I used to crew on got around 5 degrees with plates, 3 degrees was around the middle of the plate... so it's going to depend on how much space there is to move the top of the strut inboard.

[skeeler]

Originally Posted by Dave-ROR

Skeeler: Unfortunately, I've been double wishbone all around for years, so I need to relearn mac strut junk myself so I'm no help on this one currently.

Yep. This is my situation (except for rear multi-link on my NC). I've never modified the suspension on a strut-equipped car, but I'm very interested in this one (or will be, once I have a second child). I look forward to learning about struts and boxer engines.

[Ryephile]

Mac struts have little camber gain or loss, assuming the control arm is reasonably long, total stroke is short, and the control arm angle isn't excessive.

If you plan on doing stock-class Auto-x, then you'll have to hope the strut towers are slotted, or the knuckles have an eccentric connecting it to the strut. That would be the only built-in adjustment apart from an eccentric control arm bushing set or adjustable strut top.

Another solution is to add stiffer sway bars and/or springs, to keep the car flatter in corners. This will improve contact patch, however it may adversely affect wheel rate [unless the car is too soft out of the box].

Long story short, there are solutions and none of them are ideal.

[Racecomp Engineering]

With plates and/or aftermarket bolts on an Impreza, you'll be able to get more camber than you really need (well over -3.5).

2008+ Impreza can get -1.5 to -1.8 if you're lucky up front with the stock adjustment (eccentric bolt). Pretty good for a fun street car but not enough for track/auto-x with sticky tires. I'd expect the same from this car but we'll see. Maybe okay for stock class auto-x on such a light car if the standard springs are decently firm.

The Impreza is OKAY up front....it gets worse when the car is dramatically lowered though.

- Andrew

[skeeler]

Ryphile,

Thanks for your reply.

Unfortunately, springs can't be replaced in Stock, and only one swaybar can be.

Fortunately, I'd probably run this car in Street Touring. Looking at the numbers, it might be nearly competive with the two fastest cars in the Street Touring R class: The NC Miata and the AP1/AP2 S2000. The weight, torque, and power posted for the FR-S all land between those of the NC and S2k.

Springs, dampers, and ARBs can be replaced in ST. So, tf the front suspension can be given enough camber in a Street-Touring-legal way (eg, with camber plates or "crash bolts"), and if the car can be made to fit 9-inch wheels and 255 tires, it might not do too badly. My NC fits those wheels and tires, so I'm hopeful the 275-lb-heavier FR-S can, too. (Too bad I won't be able to use my existing wheels, thanks to the 5x100 lug pattern.)

The lengthy wheelbase won't help it, though.

Thanks again.

[Racecomp Engineering]

For what it's worth, STU class Imprezas don't have any problems getting enough static camber.

- Andrew

[skeeler]

Originally Posted by Racecomp Engineering

Maybe okay for stock class auto-x on such a light car if the standard springs are decently firm.

Thanks for your reply.

Do you know much about the Street Touring category? There's a lot more that can be done to fix factory problems in suspension. That's one reason I run my NC there: The NC's stock suspension is ridiculously high and soft, but the design of the suspension arms and the rest of the platform is excellent, so the car is really transformed with dampers, wheels springs, and roll springs.

The STIs certainly do well in Street Touring U, but I don't know if AWD grip hides an underlying problem with the strut suspension. Obviously, that grip will be lacking in FR-S and BRZ. I guess I need to pay more attention to what the STU Subie drivers have to say.

Lightness is relative. My last five cars have been Miata, Miata, Miata, CRX, and first-gen Prelude. The FR-S and BRZ are big cars to me.