orange260z

Hi all, I apologize if this information is out there somewhere, but I didn't see it when I searched.

I use my car as a DD in the summer, putting on 200-300 highway miles per week. However, I like to take my on/off ramps fast and do go for spirited back roads drives on weekends. I'm currently using Michelin PS2 tires 235/305 on Carrera II S wheels and Carrera Sport wheels. When I replace the tires on the Carrera Sports I will likely get MPSS or the new MPS4S.

(1) What is the recommended alignment setting for an aggressively driven street car with a factory PASM suspension ?
(2) from this optimal "performance" setting, what would I change to get better tire wear?

Thanks!

semicycler

As much negative camber up front as you can with very little toe in the rear. Have your alignment shop use the GT3 settings knowing the front camber will come up short. And use the lower side of any toe spec to reduce tire wear, especially in the rears. If the car is too twitchy afterwards add some toe up front.

edited: and seriously consider getting the DSC suspension control box to replace the factory PASM control box. It's simple to install, helps tremendously with PASM cars, and can be removed and resold in the classifieds when you sell your car

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orange260z

Thanks for the guidance, semicycler! The DSC is something that I'd very much like to get, but will likely have to wait until the USD-CAD exchange rate improves. With the added shipping costs to Canada, most US-sourced parts have a landed cost about double what you would pay.

mikemessi

Agree with semicycler. As much negative camber as you can get (probably around 1.5 deg) up front with zero toe. Very little toe in rear (minimal spec, I like around 2 to 3mm total) and take out some rear camber. Stock is around neg 2 to 2.5 degrees. Bring it down to around neg 1.75. This will minimize factory understeer and dramatically improve rear tire wear.

orange260z

Thanks mikemessi, semicycler. This is really helpful information!

cosm3os

subscribed. Same for a .1, right? Street and track with stock suspension?

lowbee

I am getting an alignment done on my 997.1S next week and after reading a lot of threads on the alignment settings, I think I will give the following a try. Let me know if anyone see something obviously wrong. Thanks



Best above really means good if I can get the front camber to -1.3 degree


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semicycler

Less toe up front. 997.1 is 5' +/- 5'. GT3 spec is 6' +/- 2'. So go for the lower side of the spec towards zero but still positive. I prefer a number between 0.0 to 0.04 degrees, perhaps 0.02 +/- 0.02 degrees.

Rear toe is good, perhaps just a hair lower at 0.08 if you really want to push the lower end of the specs to minimize tire wear.

Caster is not adjustable in stock form. As long as it lands in the 7.5 to 8.5 deg range you are fine. If you are out of spec with a stock suspension something is wrong like your lower control arm hydraulic bushings are shot.

Rear camber could go a bit higher to -1.5 degrees. It will help with corners and all that weight in the rear. But there is only so much you can do for that with alignments. Next step beyond a DSC box would be stiffer sway bars.

lowbee

Appreciate your input. I think I read one of your older post that said with close to zero toe in the front, your steering at higher speed becomes very alive. Since my steering already feel light at higher speed, I thought I go for a little more toe in the front.... I will see what toe I am currently at when the car is on the alignment machine then decide between 0.04 to 0.08 toe; I could be running zero toe in the front now without knowing it.

Thinking out loud, how much additional tire wear will -1.5 rear camber introduce versus -1.3 ? Is the relationship linear so an additional 15% of tire wear with -1.5 ?

German888

Very interested in understanding the front toe myself as I have the same "light / alive" feel at speed. Ft toe is currently set at .02

Astur

First of all it's not my intention to hijack this post but I too need input from you folks that seem be in the know. However, let me point out that I consider this wheel alignment thing is an occult science with a bit of rocket science to really keep me from understanding it.

I have a 997.2 C2 with 19" wheels which I also use as a DD and have never nor will ever track it. What I'm really interested in is reducing tire wear and would welcome specs that I can hand over to an alignment technician that he will understand in order to dial them in.

I did get some settings from Petza914 but his cars are 997.1 generation and also one highly modified, the other a C2S.

semicycler

Front toe controls turn in and high speed stability. Too much toe positive or negative and your tires scrub the pavement rather than rolling causing wear. Decrease toe for cornering improvements (closer to zero, even going negative pointing outwards for autocross driving). Increase toe for autobahn driving above say 130mph without going too high to induce premature tire wear.

But it's a trade off. Which is more important? High speed straights and long slow turns? Or fast s-turns and steering responsiveness? As you can imagine autox'ing with an autobahn alignment is sluggish. Autobahn driving with an autox alignment is twitchy. Personally I prefer the middle of the two styles - front toe closer to zero with a hair positive for street driving to keep the steering responsive yet still being reasonable sub 130mph. It's a sweet spot for back road carving and on/off ramps and still very driveable at higher speeds. But this is USA street driving with speed limits so my alignment is tailored to that driving style - fast acceleration, cornering, and braking over top speed.

Porsche sets up the 997 leaning towards autobahn style driving - high speeds, slow turns, very little hard braking. Front toe spec is 0' to 10' (0.0 to .167 deg). So being closer to zero is still within spec from the factory. GT3's though have a tighter spec of 4' to 8' (0.067 to .133 deg). Remember though the top speeds are much higher in Germany too and generally the GT3 crowd is less concerned with tire wear. So I choose to land in the 0' to 4' range, decreasing tire wear, increasing cornering and steering responsiveness but giving up some steering stability on straights when above 130mph. It's a case of using the GT3 specs as a starting point and tailoring them to my driving style. Since it's rare for me to be at autobahn speeds I bias towards handling improvements over high speed steering stability. But your "best alignment" is relative to your driving style.

semicycler

More negative camber improves cornering, especially in our wide rear wheel, rear engine cars. All the weight is back there. With street tires you can go upwards of -1.8 deg in rear camber without sacrificing rear contact patch area. Go higher and you start to lose grip. But the front to rear camber needs to be close otherwise the front to rear gripping changes (over/under steering). Some say keep them within 1.0 degree. Others want them closer to 0.5 deg difference. Personally I like to stay within the GT3 camber specs unless I'm using track tires.

Toe affects tire wear way more than camber. Our cars are known to go through rear tires generally 2X faster than the fronts. Anyone having severe rear tire wear will almost always have too much rear toe, not too much camber. But since the rear wheels are wide with negative camber more than your average daily driver, any rear wear shows up on the insides and is blamed on camber when in fact it's the scrubbing instead of rolling from too much rear toe.

But you don't want the rears too close to zero toe otherwise the back end starts walking around on you, especially when braking. So again it's a trade off - go closer to zero in the rear toe to decrease tire wear giving up some stability at speed and when braking. I prefer to again stay within the factory rear toe spec pushing the lower side of it to reduce rear wear.

Now my wife drives well within the speed limits, slow to accelerate, smooth gradual turns, slow braking. You could put a cup of water on the dashboard and it won't tip over when she drives. With her driving style more camber front or rear is not needed. She doesn't push the car in the corners at all so she needs a flatter setup. I align her cars with less camber to keep the tires flatter while keeping toe on the low side of any spec for reduced wear. Her tires will wear very evenly and get well beyond the rated tire mileage. But when I drive her cars the off ramps feel squishy with too much body roll.

semicycler

997.2 specs below. The numbers are in degrees/minutes. To convert minutes to decimal degrees divide by 60.

In your case stay within the standard spec (first column) shooting for the middle on everything except rear toe. Go for the lower side of rear toe closer to 5' or .083 degrees to reduce tire wear. Keep in mind that generally our cars will go through 2X rears for every 1X fronts. It's normal.

Or you could use those same specs shooting for the upper range on camber to improve cornering a bit while staying on the lower side of the toe specs to reduce tire wear. It's your call.

mikemessi

The only way to answer this correctly is to know your current alignment settings and current tire wear. But in general, zero toe all around and zero camber will result in the least tire wear and quietest ride while driving in a straight line down the highway. But this isn't realistic so everything is a compromise. Alignment numbers while sitting on alignment rack are static numbers. What's actually more important are the dynamic values. For example, if you have zero measured static toe in the rear, this results in a nice quiet ride with minimal wear while cruising down the highway. But, as soon as you hit the brakes hard, because of flexible suspension bushings the rear dynamically toes out from the drag of the brakes and the rear wanders under braking. Hitting the brakes hard at 100mph and having the rear drift one way or the other is a little frightening. To counter this we add a small amount of static toe in. Basically guessing how much so that under braking it stays zero or retains some toe in. Every car is different depending on how worn the suspension bushings are. To be safe, Porsche adds extra toe in but this results in scalloped tread blocks due to scrubbing as semicycler mentioned causing excessive wear and tire noise. Add some negative camber to the rear and you get the common excessive tire wear and cording on the inside rear. In general, most people wear the inside of the rears and outside of the front. For most, the fix to this is more front negative camber and less rear (and correcting the excess toe). I like a quiet tire and dont mind the lively front so prefer zero toe up front. Zero toe also causes less "binding" of the suspension allowing freer up and down movement and a slightly better ride in my opinion. So in summary regarding toe the least amount needed to keep the rear stable under braking. I think semicyclers numbers are pretty good. I track my car 4 to 6 times per year but mostly drive on the street (7500mi/yr). I like the "street" toe settings we've been talking about but I run a little more aggressive camber to balance out shoulder wear. I have -2.25 deg up front and -1.75deg in the rear. To get this I added GT3 front lower control arms. Not needed if not tracked but I still recommend pushing the front camber to the max your adjustment can go.