Lowering and geo question

[pothole]

So, I understand there are limitations with the stock suspension arms that lead to problems when lowering and achieving desired geo settings. I may well be going with RoW M030 and H&R springs and would like to know what I'm looking at.

From what I've read it's toe and camber that's the issue - adjusting one effects the other. But in what direction?

How does the conflict work? Let's say, as an example, I want as much neg camber as possible. Would this mean lots of unwanted toe? Thanks.

[Topless]

RoW M030 is pretty plug-n-play and alignments still work well. Where you get in trouble is going too low in front inducing bump steer and lots of toe out, or too low in the rear and requiring adjustable track arms to keep rear toe settings usable. I am a huge fan of not reinventing the wheel but relying on a set up guy with LOTS of experience here. There are many good DIY race prep projects but suspension setup/alignment/corner balance is where I gladly defer to very experienced hands.

[pothole]

Sure, I totally agree. Which is part of the reason I'll probably go with RoW M030. But the H&R springs, from what I understand, are not a big departure from the RoW M030 springs. I just want a tiny bit more drop than you get with the RoW M030. Seems like a good way to go so long as I understand the geo implications.

What do you run on your 2.5?

[Topless]

I run PSS9s with stock spring rates. My car is still dual purpose street/track so I don't want it totally tied down. I paid through the nose for setup and corner balance but got excellent results. Several other instructors have driven my car and commented "Wow, this thing is sweet!" So far it is the fastest BSX car in SoCal... until a faster one comes along. My brother and I are in a dogfight for the 2012 Zone 8 championships and he is very quick.

[pothole]

Yeah, PSS9 or KW Clubsport would be nice. Too expensive for me right now.

Another reason why I am thinking about adding H&R springs to the M030 kit is that I will probably take a little weight out of the car (light weight bucket seats, delete aircon, remove spare, light weight back box) and that will only push the ride height up.

I may have an option of acquiring UK-produced kit that's used in the main Boxster race series over here. That would give me ride height adjustability, which would be my preference.

[thstone]

I have ridden in Topless' car and I can say for a fact that its very nice and that he can drive it VERY fast!

Like the OP, I am still on the stock suspension and could only get -1.2 deg camber so I added front adjustable lower control arms to get -2.5deg camber on the front.

The toe can be set separately and shouldn't be problem within the ranges of the stock suspension. Find a good local shop and they can set up the car to match your driving style and needs.

[pothole]

What I'm really trying to understand is - if I got with H&R, what will be my limitations regards geo?

Will I not be able to get any negative camber on the front? Will I have to run tons of negative camber on the rear?

This is pretty much the opposite of what I want. I want to dial out as much of the understeer as possible, so I want to max out the front camber and keep the rear camber under control.

[jsceash]

What about the tires rubbing the fenders. This probably the biggest reason I've held off on any system. What do you do about that and whos coil overs don't require rolling your fenders.

[Topless]

Originally Posted by pothole

What I'm really trying to understand is - if I got with H&R, what will be my limitations regards geo?

As you lower the car, negative camber increases and the car tends to toe out. Getting 2-3 degrees negative camber while maintaining zero toe up front is the holy grail. Lowering the rear a touch is ok but it is easy to go too far and not achieve zero toe without adjustable control arms. Too low in the rear and handling goes out the window.

The simplest way to improve negative camber is by adding GT3 arms in front instead of changing springs as thstone has done. It does cost a bit more than springs but you can really dial in ideal settings in front. By only adding lowering springs you will lower the nose a fixed amount but your alignment results may be less than ideal.

I don't understand your term "geo setting". Are you asking about steering geometry and bump steer issues?

Jsceash,
Tires rubbing wheel wells is more of a wheel/tire issue than suspension issue. You can stuff 275s front and rear without rubbing if you choose your wheel offsets carefully.

[DFW02S]

Originally Posted by Topless

...
I don't understand your term "geo setting". Are you asking about steering geometry and bump steer issues?
..........

Geo = alignment.

[pothole]

Yes, geo just refers to suspension geometry / alignment.

My problem is that the adjustable arms are so pricey. Are they the only way to achieve adjustable camber?

What about top mounts?

[Topless]

Originally Posted by pothole

Yes, geo just refers to suspension geometry / alignment.

My problem is that the adjustable arms are so pricey. Are they the only way to achieve adjustable camber?

What about top mounts?

Welcome to Porsche. The GT3 arms are less $$ than camber plates and offer a lot more adjustability.
Front Camber Plate Set, 996/997/986

[pothole]

Bit of a nightmare.

On my old BMW E36 track slag, I just bought some used M3 Evo top mounts for £40 the pair. Fitted them reversed and that bought me -2.5 camber and some extra caster. Job done. Takes all of about an hour to fit them both, too.

I guess I might just have to keep a look out for some used camber plates. Problem with the GT3 arms is that I probably need new arms anyway and buying GT3 arms right now is going to blow the budget. And I'm pretty reluctant to buy new arms now and them replace them fairly soon with GT3 arms.

I may just have to see what can be achieved once it's lowered. Shame as I now already that I'll want to max out the front camber.

I'd read a few references to twist the strut and also something to do with widening the mount holes to increase camber...does this ring any bells?

[thstone]

Originally Posted by pothole

Yes, geo just refers to suspension geometry / alignment.

My problem is that the adjustable arms are so pricey. Are they the only way to achieve adjustable camber?

What about top mounts?

As I mentioned, I was in the exact same situation and just bit the bullet and installed the adjustable front lower control arms - instant -2.5 deg camber in front!

[Overdrive]

Originally Posted by pothole

...track slag...

Sorry in advance for my less that contributing post, but I just get a kick out of some the slang that exists in the UK...as I'm sure you do with some of the slang here. If I didn't know what that meant already I'd be

I don't know much right now about suspension setups for the car, I'm still learning things every day with this car. I believe my ideal/minimum setup would be sticking with stock wheels, good and grippy summer tires or the best A/S tires I can find, and the ROW M030. I guess when it comes to tracking the car I want to leave it as it's supposed to be set for the street from the factory and get good at driving it fast in that way rather than setting it up differently...but that's just me.

[pothole]

Heh - what would be the equivalent of track slag in the US?

I wouldn't claim to be Fangio reborn. But I've done enough track days to know that I'd get frustrated very quickly if I was fighting the set up too much. It doesn't need to be an out and out track set up. But if we're talking, say, less than one degree neg camber on the front, I'm pretty sure that's not going to cut it.

I ran -2.5 on the BMW and that was absolutely fine for road driving - more importantly, it was great on track, pretty my zero understeer - neutral to oversteer everywhere, which is what I prefer.

I'm leaning more towards the aggressive coilover setup if the deal I had arranged at the end of the last year still holds. I think it comes with camber plates so I would hope to be able to achieve at least -2, which should be just about OK.

[LAP1DOUG]

Pothole: I agree with the "aggressive coilover setup", but be careful on trying to lower the car too much. It will help out static camber to a point, but if you take it to the limit, the control arms will go past parallel to the ground and dynamic camber curves in roll will go to hell. The best solution for these cars really is good coilovers with minimal lowering + GT3 arms for camber. If you want to get rid of understeer, it also helps to get wider front tires and reduce the front to rear tire stagger these cars come with. The best bang for the quid is always tires - start there.

[pothole]

Yup, noted. ANd of course with coil overs I will be able to tune the ride height just right.

I won't go crazy low, but I will go a little lower than RoW M030. That's the plan, anyway.

[berty987]

The control arms are fixed to the chassis behind the front suspension and in front on the rear . As you lower the car and move the suspension further away from its pivot you would get more camber and on the front more toe "out " and on the rear more toe "in " I suspect. The race series boxsters dont use the Gt3 camber correction plates on the front arms over here in the UK so Id suggest for a road car you wont probably go low enough to require any specialist equipment to re adjust the geometry , though you may experience increased tyre wear from the increased camber.