Chime in on my alignment specs

[na2ub]

For street / track. I am getting an alignment soon on my SC and want a decently agressive alignment without going overboard. Here is what I am thinking

Front:
Camber: -1
Toe: 0
Caster: ?

Rear:
Camber: -2
Toe: 1/8th combined.

Does that seem reasonable? Will it be to darty on the 120mph straight, or will the rear toe keep that under control?

TIA,
Doug

[dad911]

Well, that's certainly not overboard.
What's your suspension specs? & tires?

[na2ub]

Am I being too dainty? I just don't want to eat through the insides of the tires when driving on the street. That being said, I probably only put about 1,000 miles on the car each year. (hopefully about 120 of those on the track).

Tires are Kuhmo Ecsta (sp?) SPT 205 55 R16 and 225 50 R16 on 6 and 7 Fuchs. (stock).
Suspension is 22/29 T-bars with bilsteins valved to match (by ER) with new rubber suspension bushings. Sways are still stock SC. (Carrara sways sometime in the future.).

Car is a little lower than Euro, although hard to tell since the camber is out of whack. Probably end up about 24.75 rear 25.25 front.

Do you think I should go -1.5 front, -2.5 rear? What about toe - I know there are varying opinons here, but a little toe in, either front or rear, helps steady the car, right? I don't mind a little wandering with 0 front toe, as long as it is not scary at speed.

[KTL]

Since you drive it so little, max camber front and rear. Given how little you drive it, you'll not be killing your tires too soon. I've run the maximums on my street car turned track car for many years and I have not had to replace tires at too high of a rate. I've tracked that car for about 5 yrs. with occasional street cruising and exclusively driving it to/from events (never trailered)

You'll be lucky to get -1 to -1.5 in the front. I'd suggest a bit of toe out if you run short tracks and some toe in if you run longer tracks with higher speed turns. Your rear toe is fine.

[na2ub]

Local track is mid ohio. 2.4 miles, 120 mph straight, 65mph sweepers. It is my understanding that if I run 0 toe in front, I should definitely keep some toe in in the rear. If I toe in the front, I can zero the rear (factory spec?). I guess I will plan for 0 in the front (compromise) and toe in in the rear a little for stability. If I run max camber in the front (between -1 and -??) shouldn't I keep the rears one degree more negative to avoid excessive understeer? Seems like -1 in the front, and -2.5 in the rear might push a little through the tight corners.

[tobluforu]

Try to get around 6.0 caster if its adjustable on your car. If you want, get max camber at the rear, then adjust the front to have .5 less in the front. I run zero toe on the front with 1\16th toe in the rear. I also run 1\4 inch spacers in the front as well.

[Chuck Moreland]

Originally Posted by na2ub

Am I being too dainty? I just don't want to eat through the insides of the tires when driving on the street. That being said, I probably only put about 1,000 miles on the car each year. (hopefully about 120 of those on the track).

@1000 miles per year, you don't have to worry much about wearing out the tires on the street. They'll be dried out after 5 years/ 5k miles and ready for replacement anyway.

But with inadequate camber you can shred a set of tires in 200 track miles, easy.

Given your driving balance, you'd be better off going more aggressive on the camber.

With your existing setup, the most you can get from the front is about 1.5 degrees. Max this out.

Set your rear at 2.25, which will be a good balance to the front.


Your planned toe settings should be okay. Set your caster at +6.5

[stlrj]

Doug,

After you get it aligned, could you post the alignment printout so we could see the before and after results?


Cheers,

Joe

[tobluforu]

If the shop has the ability to corner balence then you might as well go for it.

[na2ub]

Thanks for the input. After doing some suspension work, I have had the car up and down about 6 times so far and am getting fed up so I am taking it to someone else to do. Corner balance is not in the cards for now, but there is a local shop with scales, so I might take it in to see how far off I am. Naturally after I see that the car is out of balance, I will be itching to get it balanced ... damn!

[turborat]

What a great question.

Here is what I have learned through several years of listening to "expert" opinion, a lot of adjusting on my own and lot of time spent, several prematurely worn sets of tires and considerable money paid to align and set-up my car numerous times to get it right. My points below are based on performance set-up for track.

Considered to be old and outdated technology by some, the 911's torsion bar suspension is surprisingly sensitive to small changes. This can be good if the set-up blends well with tire size and type along with suspension stiffness and compliance. if not, the car may become a diabolical nightmare on the track or in the wet. Suspension modifications increase the sensitivity to all of these adjustments.

Tire size and type are factors for camber setting. Wider tires may require different camber than a thinner tire. Sidewall stiffness will also effect these settings. I prefer a 225/245 tire on 7/8 wheels for the SC flares on the track. The tire mentioned will wear very quickly on the track. Especially at Mid-Ohio (I love that track). One weekend if driven hard. Consider Toyo RA1 R888, Nitto 01, Michelin Pilot cup or similar performance tire.

Suspension stiffness and car's weight are the next factors to consider. I refer to suspension travel and the additional (-) camber gained as suspension compresses through turns.

.....and finally. Driving style will may determine final set-up.

I am happy to share my car's set-up. I have achieved a set-up that gives me a 4-wheel drift and very neutral feel.

If your car is lower than Euro height, you need to consider (if not done already) some of the parts below to include modified struts and tie-rod drop links and steering rack spacers. Otherwise bump-steer will be your rival.

My car's weight is 2,376 with 6 gallons of fuel and me in the seat.
1979 SC fitted with 930 flares. Track width will effect set-up also.
23/32 torsion bars
Re-valved Bilstein Strut inserts based on corner weights and torsion bars.
Boge struts decambered spindles raised 30mm
Elephant Racing tie-rod drop link
Steering rack spacers
Bilstein sport shocks (rear)
Weltmiester bushings on all four corners
solid engine and trans-axle mounts
Cambermiester kit
22MM sway bar front non-adjustable
22MM sway bar rear adjustable
Toyo RA1 tires - 235/275 17"

Corner-balance is imperative and must be considered with any set-up change.
Mine is:

FL - 430#
FR - 423#
RL - 783#
RR - 740#

Camber:

FL - (-) 1.53
FR - (-) 1.51
RL - (-) 2.61
RR - (-) 2.56

Toe:

FL - .29 Toe Out
FR - .29 Toe Out
RL - .34 Toe In
RR - .33 Toe In

Caster:

FL - 5.06
FR - 5.01

Hope this helps you out. Use it as a guideline and accept that your final settings may be different.

[euro911sc]

Keep in mind that your toe measurements should be in DEGREES not INCHES. It is very common to state toe in inches, but since we all have different size wheels/tires and measure at different spots who knows what we are really saying! The Porsche spec book gives it in degrees for this reason.

Some negative toe in the rear is recommended. IRRC spec is -10' +-10'.

I am running min caster and 0 toe in front. I am unhappy with the stability and will be moving the caster more negative to add more high speed stability. Car turns on a dime in low speed now, but I'm a track guy and such sensitivity is not desired.

I have -2 deg. front and -3 deg. in the rear for camber. so far no issues with street wear on tires, but I'm only 3 months into driving ti and I don't drive it every day... hard to fit 3 kids in 1 race bucket

I have the same t-bars as you, 22/29, but have gone to 22mm adj. sways and have my rear bar set to 3/4 soft and front bar set mid pack. I will be moving to all soft in the rear to try and reduce some over steer.

Hope this helps

-Michael

[euro911sc]

Originally Posted by turborat

Camber:

FL - (-) 2.61
FR - (-) 2.56
RL - (-) 1.53
RR - (-) 1.51

Toe:

FL - (-) .29
FR - (-) .29
RL - +.34
RR - +.33

Whoa! are you saying you have less neg. camber in the rear than the front? Also that you have positive toe in the rear?? Both go against what I have read here and in books... and you say you have a neutral handling car? I'm in disbelief... if true (not saying you lie!) it just goes to show that there can be a wide variety of setting 'groups' that will work for a particular car and driver. Which leads to an error in assumptions we are making that if we use someone else's specs we will like how the car drives!

-m

[na2ub]

Originally Posted by euro911sc

I am running min caster and 0 toe in front. I am unhappy with the stability and will be moving the caster more negative to add more high speed stability. Car turns on a dime in low speed now, but I'm a track guy and such sensitivity is not desired.

Positive castor not only improves stability (wheel tracking) but is supposed to reduce the positive camber change that the wheels experience during cornering. Most track guys run all the castor they can get.

I agree, turborat's settings, unless typo's seem quite unusual. But if it works for him, so be it.

[turborat]

Post is edited. Front and rear cambers were reversed. Toe out in the front. Toe in at rear. Alignment guy's note has negative and positive as printed. Measurement is in minutes.

[KTL]

Doug,

Don't underestimate the benefit of scaling the car. For street use it's meaningless. But on the track it makes a big difference. I learned first hand that setting by fender height looks nice, but can result in a car with corner weights that are considerably off the mark. I set my car to the obligatory "euro" fender height and called it good. Car handled OK at the track, but I would drag the RR under heavy braking.

Well one day I was at a friend's garage with another 911 ('79 SC) and we put our cars on his new scales for grins, to see how much of a difference in weight there was between the two- '79 SC vs. '87 Carrera. Mine was over 300 lbs heavier and my RR corner was almost 200lbs lighter than ideal. For a quick fix I turned up the LF torsion bar adjuster to compensate and it made a noticeable difference in reducing the RR lockup. Once I got the car well aligned and corner weighted, it was a whole new driving experience. I attribute the good alignment to the improved better handling, but i'm sure the corner weighting helped a good bit too.

As another aside, I diddled with the front coilovers on my racecar this winter to set the perches better. Seemed unlikely that they were at the correct setting, bottomed out on the strut. Well my eyeball adjustment threw off the car's handling immensely and the car understeered like a pig, balance and toe all out of whack. Point being is there's nothing wrong with making changes. Just make sure you take measurements to check your results so you can know sooner (at home) than later (at the track) if you made an improvement before spending your money (track day entry fee).

[Peter Zimmermann]

I like to start with a conservative setup, and sneak up on what you can consider comfortable for your driving style. I have always set my car to work its best on the fastest turn of a particular track, and adjust my lines/apex in the slower corners as needed. I prefer Euro height because of shock travel.

I will generally start with 1.0 negative camber (front) and 1.8 negative camber (rear). I set the front toe at +1/32 (toe OUT) total. Rear toe is zero (you don't need a "handbrake" back there!). Start your practice runs with 32(F)/34(R) - cold - and measure your gain.

The next step, if you have adjustable sway bars, is to find a balance point for your driving style. Then, get out the pyrometer and get to work. Do three fast laps, bring the car in, and measure each tire across its contact patch. The inner third of each tire should be about 25F hotter than the outer third, with the center somewhere in between. Be very quick doing this, preferably have someone to measure and a second assistant to write. All measurements, if possible, should be made in the hot pits. Stay in your car; it takes too much time to get out, collect your tools, etc. Talk to the event steward, tell him what you and your helpers want to do and make sure you know the track regulations.

Repeat your laps and measurements. Only then will you begin to form a picture of what you want from the car, and how to change/ improve it. The toe out will create a small amount of straight line darting, but nothing serious. It will also aid with turn in, the faster the better.

And, BTW, start a log including tire pressures/temps, ambient temp and track, and you must corner balance the car before setting your specs. If all is well with your front suspension components (struts, spindles, bearing adjustment, tie rod ends, etc.), you will probably end up with about 5.6 +/- .2 caster. A little more won't hurt. This strategy has worked very well for me, if you choose to try it - good luck!

[euro911sc]

Originally Posted by na2ub

Positive castor not only improves stability (wheel tracking) but is supposed to reduce the positive camber change that the wheels experience during cornering. Most track guys run all the castor they can get.

I always thought it was negative, no? IE 0 deg. caster is straight up and down and more neg. is moving the top of the strut toward the rear of the car... either way, I'll be increasing the caster angle by moving the strut top toward the rear

I originally set it up with low caster because I drove a car that had very heavy steering and I hated it. It was mentioned that a likely cause was high caster. So I figured I'd start with the least amount and move up as needed. Now that I am confident on doing that work myself I can mess with it at will

I like Pete's advice: set the car up for the fastest corner and figure out how to deal with the rest of the track!

-Michael

[na2ub]

Thanks guys. Not sure about the castor sign, if it even has one. If 0 degrees (or no castor) is straight up and down, wouldn't any angle be a positive increase in castor? Blah blah ... Anyway, I am leaning toward Chuck's approach, not only because the most closely resemble what I was thinking, but also hey ... it's Chuck. Not to disregard any other comments, though. There are a lot of good points and approaches. The one problem I had when I DE'd mid ohio, was a lot of understeer on the last tight downhill turn in the esses. I am hoping the upgraded suspension and more camber in the fronts will help remove that. It really crushed my momentum though that corner ... very annoying.