Handling: Camber Attainable with Struts. Your Experiences?

[skeeler]

Originally Posted by Racecomp Engineering

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

- Andrew

Thanks. Sounds like you are the right guy to talk to. Is camber loss an issue then?

[Kostamojen]

As a Subaru guy who has done pretty much everything with his car suspension wise (bushigns, coilovers, whatever, even lifting the car for off-road purposes) I'll chime in...

You can easily get -2.5-3 front camber with camber plates and the stock camber bolts. The stock bolts are good for just over -1.5 as Racecomp mentioned (great guys BTW, they know far more than I do, LOL!).

If this is indeed just a take-off suspension from an Impreza, then STI aluminum control arms are an option up front as well, and I'm not 100% on this but they might also modify the suspension angles a bit (more caster too).

There are also kits out there for adjusting suspension angles when the car is lowered, at least in terms of the control arm location and tie rods.

There are also LOTS of bushing upgrades and other such bits available that you can use in Street Touring classes, and those work wonders.

Working with the front suspension is VERY easy on these cars. I can have the front struts off and back on in under an hour with hand tools. Although I haven't worked with the rear multi-link yet...

[Ryephile]

Camber loss on struts is always the problem. It's a dichotomy; run lots of static camber to achieve good contact patch at peak cornering, or zero static camber to get peak grip and stability at WOT and full-brake. You can't have both. This is why some tires are especially designed for strut cars; their carcasses are flexible to stay reasonably stable in a straight line with high static camber.

However, if the car has good roll stiffness, the amount of camber loss up front won't be a big deal, or perhaps even a real problem. With enough roll-stiffness, even -1.5° static will be an acceptable compromise between straightline stability and using maximum tire shoulder in corners.

[Racecomp Engineering]

Originally Posted by skeeler

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.

I don't auto-x myself but most of our customers do. 2008 STU National champ was one of our sponsored drivers running our coilovers on a GD chassis STI. The class is fun in that you have more tuning options than the stock classes, which kill the high, soft, and camber challenged (when running hoosiers on soft springs) Subarus.

Originally Posted by skeeler

Thanks. Sounds like you are the right guy to talk to. Is camber loss an issue then?

It's something to think about for sure especially on lowered cars but it's absolutely workable. There are a few roll center correction kits that help but these are illegal in ST. A few people run some unconventional set-ups, but the 2008 winner was fairly straightforward FWIW.

- Andrew

[Racecomp Engineering]

Originally Posted by Ryephile

Camber loss on struts is always the problem. It's a dichotomy; run lots of static camber to achieve good contact patch at peak cornering, or zero static camber to get peak grip and stability at WOT and full-brake. You can't have both. This is why some tires are especially designed for strut cars; their carcasses are flexible to stay reasonably stable in a straight line with high static camber.

However, if the car has good roll stiffness, the amount of camber loss up front won't be a big deal, or perhaps even a real problem. With enough roll-stiffness, even -1.5° static will be an acceptable compromise between straightline stability and using maximum tire shoulder in corners.

I agree. It's just a part of the puzzle but there is a sweet spot depending on the rest of your set-up.

- Andrew

[Allch Chcar]

Wow. Thanks so much for sharing guys! I thought the number I found was fishy but it sounds like it's normal for Macpherson struts.

[Kostamojen]

Originally Posted by Ryephile

even -1.5° static will be an acceptable compromise between straightline stability and using maximum tire shoulder in corners.

One thing I did with my camber plates was run them at max camber at the auto-x, then the next day pull them back to where they are at a more factory location for better tire wear and straightline stability for daily driving.

Wasn't that hard to do either, just get some weight off suspension and pull it back into place. 15 minute job at most.

[70NYD]

I had macphersons in my 323, while they are challenged in the 'camber curve' I could run ~2degrees all around (macphersons all around) with the camber plate on neutral and 6 degrees (was just for test never actually drove like that) with camber adjusted to max. I did have coilovers that have a WIDER lower bolt arc slot so it allowed for a very good setup.
By maximum I mean maximum on the bottom and maximum on top combined. The top swing was 4 degrees from start to finish and the bottom swing was 2degrees from top to bottom. But what you really want with a macpherson for auto cross (for my 323 anyway) is decent static camber and as much caster as you can get to increase your dynamic camber in autocross dynamic camber is more important than static

[Ryephile]

^^Excellent point! Dynamic camber is what's relevant.

[70NYD]

Ooh whoops there wasn't meant to be a dislike thumb there.. Was supposed to be a
I never got more than 4deg positive caster, but some ppl run up to 8
I also only did a few autocross, never really had time...

[skeeler]

Originally Posted by Kostamojen

One thing I did with my camber plates was run them at max camber at the auto-x, then the next day pull them back to where they are at a more factory location for better tire wear and straightline stability for daily driving.

Wasn't that hard to do either, just get some weight off suspension and pull it back into place. 15 minute job at most.

One of the local STR guys does this with his Z3 M Roadster. It takes him no more than 10 minutes.

[skeeler]

Originally Posted by Ryephile

^^Excellent point! Dynamic camber is what's relevant.

So, by dynamic camber, do you mean instantaneous camber as a function of static camber, compression (or rebound) travel and caster-induced camber?

[70NYD]

Dynamic camber as in anything happening under compression/extension/steering

[Ryephile]

Exactly.

It's not a perfect system, as dynamic camber is maximum with tight-radii corners. Those that run HPDE/track-days would likely have to run more static camber, as steering angles are less on a track vs. auto-x.

At this point however, we're kind of nitpicking a perceived problem that may not exist. We're not familiar with the cars' balance at the limit in various situations [street tire auto-x vs. Hoosier track-days]. The problem may end up being the rear-end camber curve, a roll-center axis issue, or a bump steer problem front or rear. Of what I've seen so far of the suspension, I may hazard a guess that the rear toe-control link might result in too much bump steer with the rear wheels.

...or the car could indeed be close to perfect; who knows at this point. Remember that Porsche's are all strut and they manage to make it work very well.