Street alignment specs

[woodsman]

I'm looking for your experiences/ opinions on specs. I'm about to get mine done after lowering the car 1.5" FR and 1.0" RR. I've read the other posts but want suggestions on conservative STREET ONLY specs.

(1) Do these cars need more RR camber than the FR ?
(2) Doesn't it make sense to demand a 200 lb. weight on the driver's seat?
(3) I'm concerned more about dynamics than overall grip levels
thanks

[Steve Tinker]

Woody...
Earlier this year I installed PSS9 coilovers to my 2001 S and had the same questions.
I lowered the Fronts 17mm & Rears 12mm which is about half of what yours is.
I had a quick alignment by a non Porsche shop and it was OK on the road, except the car got nervous over 140kmh. So I took it to a Porsche shop and they gave me the following setup:

FRONT: Toe = 1,5mm, Camber = -0.6 deg, Caster = +7deg.
REAR: Toe = +2.0mm, Camber = -2deg.

Wih the Front toe increased from 0 to 1,5mm the nervousness dissapeared and the car now feels really good at all speeds.

PS. with your lowering, be prepared to scrape your underside - perhaps the roads in BC are better than in Australia, but even mine set at 17mm & 12mm lower than stock, its easy to contact the underside.....

So, yes the rear need more Camber than the front. The shop said that having my 65kg weight in the drivers seat for normal roadwork was splitting hairs, but for track work, that weight & corner balancing was preferred.

[Topless]

I agree with most of Tinkers settings. For a lot of hwy work I would probably run less rear camber, maybe -1 degree R with -.5 degree up front. This should give you nice even tire wear.

[Ian c]

Factory specs for comparison ....

[thstone]

Originally Posted by woodsman

I'm looking for your experiences/ opinions on specs. I'm about to get mine done after lowering the car 1.5" FR and 1.0" RR. I've read the other posts but want suggestions on conservative STREET ONLY specs.

(1) Do these cars need more RR camber than the FR ?
(2) Doesn't it make sense to demand a 200 lb. weight on the driver's seat?
(3) I'm concerned more about dynamics than overall grip levels
thanks

Alignment is all about tradeoffs. When you say that you want an improvement in dynamics, are you willing to live with the downside like increased tire wear or some loss of straight line stability? If not, then you won't see much of an increase in dynamics.

With that being said, ST's numbers are an improvement over stock but won't transform the car into a canyon carver (the changes aren't big enough). But this is a good starting place and definitely in the right direction.

Usually, the rear has about 0.5 deg more camber than the front. This can vary but its a good starting place.

There is almost no value in weighing down the drivers seat when aligning the stock suspension. The car really needs coilover shocks and a corner balance to be able to take advantage of the change in weight distribution due to the driver's weight.

[woodsman]

thanks for the help guys- I often see Boxsters set up with lots of neg cam on the rear (-2) and wonder if it's really required if the driver actually wants a 'neutral' car. Maybe Porsche is just trying to guarantee understeer?

[edc]

What works best for you really depends on your driving style and the types of roads. Lots of negative camber is great but you really need to be leaning on the car a lot in the corners to make the most of it otherwise for the most part it is unfavourable. The Boxster has a tendency to understeer so if you want to reverse this dynamic then you would want more negative camber at the front than the rear. The problem is you will be highly unlikely to achieve this with the standard parts and range of adjustments. The problem is exacerbated when you lower the car. There is another thread on here somewhere where there is discussion about my car having the front top mount slots drilled togain more adjustment.

As for weight in the car, you should try it and see the results live. There is a lot more change than you might otherwise think. My car is typically set up with ballast for a full tank and 65kg in driver seat. For me this is how the car would be if driving particularly fast.

[woodsman]

FUEL! I didn't think of that...Geez now I wish I knew what the specs were before I changed the struts- transient response was good and it was stable all the way to 145 that one time...but it understeered except in that one upward sweeper. Maybe -1 all round and a little toe out front and back? Anyone tried it?

[Topless]

Hehe,

Yes my car has a touch of toe out in the front. It improves turn-in for really aggressive cornering like on an AX course. It also makes the car a bit darty and unstable at speed. Toe out tends to wear the inside of the front tires more than the outside.

Toe out in the rear is like driving a bucking broncho. The car is totally unpredictable under braking and constantly wants to swap ends. Not recommended.

[thstone]

Tradeoff's, tradeoff's.

I run zero toe in front to get a tad better turn-in, minimize tire scrub, and maximize straight line speed - its a good trade off between speed, turn-in performance, and straight line stability.

Front toe out will improve turn in but at the expense of straight line speed and stability.

Rear toe out? Turn in can be even quicker (this is similar in character to most four wheel steering systems, e.g., the new GT-3). But since the toe out is fixed (not varying in proportion to the steering input) it results in crazy handling because anytime that the car starts any amount of rotation (intended or not), the toe out wants to drive the rear end around even further resulting in oversteer in both directions. Tank slappers are easy to induce.

[edc]

I did run 2 minutes toe in all round but after some tweaks am at zero all round. A touch of toe in on the rear keeps it stable under throttle and in a straight line.

[woodsman]

ok, so no toe out. Since I seldom get over 75 maybe I'll try zero toe, fr and rr. If need be I could add toe out to the fr, at a later date.
Does anyone know how low you can go before needing to replace the rear toe links?