smithk993

Would someone help me understand the values for how toe is measured. I understand that toe out has the front of the tire pointing outward and toe-in pointing to the center line of car.

I see a lot of discussing about having like 1/32 or 1/16 toe to provide more crisp turnin? and total toe. I'm not sure how that relates to the figures below from the Porsche Repair Maual where they show +5' +- 5'. Can someone tell me what the 1/32 or 1/16 might relate to on a machine which measures angles?

From the Porsche Specs

Porsche Repair Manual Wheel alignment Values

Turbo USA TurboRoW Turbo X73 GT2
Front axle
Toe unpressed (total) + 5' ± 5' + 5' ± 5' + 5' ± 5' + 8' ± 2'

Toe difference angle at 20° lock − 1° 20' ± 30' − 1° 50' ± 30' − 1° 50' ± 30' − 1° 50' ±30’

Camber (with wheels in straight−ahead 0° ± 15' − 30' ± 15' − 45' ± 15' − 1° ± 5'
position)

max. difference, left to right 20' 20' 20' 10'

Caster 8° ± 30' 8° ± 30' 8° ± 30' 8° ± 30'

max. difference, left to right 40' 40' 40' 40'

Rear axle
Toe per wheel + 10' ± 5' + 10' ± 5' + 10' ± 5' + 13' ± 2'

max. difference, left to right 10' 10' 10' 5'

Camber − 1° 25' ± 15' − 1° 25' ± 15' − 1° 40' ± 15' − 1° 50' ±


Another bit of confusion for me is that the front TOE In values for US Turbo are +5' while the GT2 values are +8'. I would have thought that the larger value of positive toe in would have been less agressive? I understood the closer to neutral or negative (Toe Out) the more agressive the turnin and darty nature.

Getting an alignment next week so thanks for the insights.

Keith

adam_

the 5 +/-5 means "from zero to 10'..."

nice chart here: http://www.fresnoscca.com/forums/sho...hes-to-Degrees

1/32 is 0.1 degree or about 0.03" (1/32"=0.032" actually)

what are you trying to accomplish? Unless you are tracking- and racing for money- I'd go with just a nice street set up and skip much toe. Also, how the suspension moves under acceleration/braking is a factor in setting toe, which might explain the GT2 variance...

smithk993

I have PSS9 suspension lowered to the maximum amount allowed in the Pss9 specifications.

I don't track this car at present (have another car for that) but like maximize the handling on the street.

Am I correct in that as you approach toe-out (negative toe) that the turn in is quicker? If so, then it seems unusual that the specifications for the GT2 are actually more forgiving than for the turbo. Maybe thats to counter the effects of rear wheel drive and reduce oversteer....

So the Porsche specifications for front toe ranges from 0' to 10' or 0 degrees to .166 degree toe-in.

Keith

Macster

Alignment is tricky. It is setting the car up while stationary for when it is moving down the road at sometimes considerable speed, turning, braking, and so on.

A car spends considerable time turning. Even going straight ahead everytime you correct the direction to keep the car straight that's a turn.

Less toe in generally results in a car that wanders feels vague going down the road. More negative camber at the front is generally regarded as making the car quicker to turn in. But the car can become darty under some road conditions.

Variation in toe is affected by bushing stiffness and tire size. Stiffer bushing mean the wheels move back less when the car is moving down the road and thus need less toe in while stationary so when moving down the road the tires become more straight ahead without going from straight ahead to toe out. Same for the rear.

Softer bushings require more toe in so the toe does not become toe out when the car is moving.

Alignment is a very personal thing. Best advice I can offer is start with a standard alignment and then spend some time in the car driving it like you will drive it and on roads you intend to drive it on. After awhile you should develop an opinion as to what the suspension/alignment needs to better suit your tastes.