rear toe question??

[Steve W]

It seems the common rear toe recommendation on a 911 is at 1/8", but is that per side or total?

A search shows all kinds of numbers posted with no units, which could be minutes, mm, fractions of an inch, or fractions of a degree, and it's usually not specified as per side or total.

[J Smith]

I've always run 1/16" per side, so that would be 1/8" total toe in. It's worked well for me for the past couple years on the track, although I may try a little less now with my Guard LSD set up for 80% lockup on deceleration. I think that's the main reason for running toe in on the rear...keeps things stable under braking.

For a 25" diameter tire, I think 1/16" equates to about .13-.14 degrees. I think. Sometimes my math isn't so good.

[TimT]

It's considered total toe...

Such that you have enough toe in that under braking the wheel doesn't go to a toe out attitude

[450knotOffice]

Tim, thanks for that explanation. It makes sense now.

[Bill Verburg]

Current practice on 997Cups is 0 toe front +34" total toe rear(toe in), w/ 18" Michelin slicks

or

-5'(toe out) front, +34' total toe rear, w/ Pirelli slicks

[Steve W]

Thanks guys. Does the rear toe settings of the 997s have any relation to the earlier body 911s? I aware a lot of the 996 and 997 GT3 guys are running anywhere from 34' to 44' rear total toe in, which is equal to ~1/4" total toe in to reduce nervousness and snap oversteer.

[Bill Verburg]

Originally Posted by Steve W

Thanks guys. Does the rear toe settings of the 997s have any relation to the earlier body 911s? I aware a lot of the 996 and 997 GT3 guys are running anywhere from 34' to 44' rear total toe in, which is equal to ~1/4" total toe in to reduce nervousness and snap oversteer.

As the 996 and 997 suspensions are very similar one would expect similar settings

It appears that they did some experimenting
here's the setup for 2002

and for 2003

from 2003 up through the late 997s they use they same settings

[Steve W]

I understand the 996 and 997s have very similar suspension design so they share the same alignment setups, or are you saying that such also applies to the early body 911s, (pre '89 and back) - so one could run 1/4" total rear toe? For the 70s and 80s 911s, B.A's book calls for:

"Toe-in: +10 min +/-10 min (maximum difference between left and right 20 minutes)"

The above doesn't specify total toe or per side, so if one assumes total, that would be ~1/16" total, or about 1.77 mm, almost nothing. On the other hand, if it's per side, and one goes to the max end of the spec, that could be +20' per side, or +40' total, or 1/4" total. Do I have it confused enough already?

Now if we go further in BA's book, for the 964s and 993s, he further goes to specify "rear toe at +15 min +5 min (per wheel)", or 30 min total, or about 1/4".

[Bill Verburg]

Originally Posted by Steve W

I understand the 996 and 997s have very similar suspension design so they share the same alignment setups, or are you saying that such also applies to the early body 911s, (pre '89 and back) - so one could run 1/4" total rear toe? For the 70s and 80s 911s, B.A's book calls for:

"Toe-in: +10 min +/-10 min (maximum difference between left and right 20 minutes)"

The above doesn't specify total toe or per side, so if one assumes total, that would be ~1/16" total, or about 1.77 mm, almost nothing. On the other hand, if it's per side, and one goes to the max end of the spec, that could be +20' per side, or +40' total, or 1/4" total. Do I have it confused enough already?

Now if we go further in BA's book, for the 964s and 993s, he further goes to specify "rear toe at +15 min +5 min (per wheel)", or 30 min total, or about 1/4".

I believe so
I run 0 toe front w/ +5' side rear, when I run less in back the car gets twitchey, more and it doesn't seem to turn well. It's hard to compare because I also changed all the bushes and pinned the side mounts at the same time. On the 993 Cup cars they ran 0 front and +5 to +10' /side in back.

Don't know about 964s

w/ my '76 C3, 0 toe front and +1/8" side rear seems to work well. 17" wheels

[911st]

I have to ask. Dose 1/8" mean that if one could mesure the distance between the most forward part of the tire and there rear most part of the tire the delta is 1/8" per side.

Thus, if one uses an alignment string, do we expect the front of the tire mesurement to be 1/16" in and the rear point 1/16" out?

Thx

[Bill Verburg]

Originally Posted by 911st

I have to ask. Dose 1/8" mean that if one could mesure the distance between the most forward part of the tire and there rear most part of the tire the delta is 1/8" per side.

Thus, if one uses an alignment string, do we expect the front of the tire mesurement to be 1/16" in and the rear point 1/16" out?

Thx

yes

[911st]

Thanks again Bill!

[175K911]

My experience is limited to the 74-89 911 models but have found that rear toe-in is needed to counteract the suspension bushing slop under hard braking and cornering. Once I converted the back of my car to ER Polybronze and inner Monoball cartridges, I was able to dial back to +5 min per side. Combined with my Guard set at 50/80, the rear is rock solid under threshhold braking even when trail braking at triple digit speeds.

[jhhaas]

what would one expect with 1/16 total toe out in the rear? squirrly under threshold braking? what else?

[Dave at Pelican Parts]

I would expect it to be squirrelly under braking, and want to slew sideways in the corners under power. It was kind of fun having to chase the tail end of my first 914 all the time, but it did get old quickly. And the rear tires (street tires) were eaten in something like 5000 miles. The inner shoulder was completely shredded, with pieces of cord sticking out.

--DD

[cstreit]

Originally Posted by jhhaas

what would one expect with 1/16 total toe out in the rear? squirrly under threshold braking? what else?

You'd be spending your time trying to keep your tail lights from exiting the corner first.

Imagine if you're turning hard right, but your left rear tire is trying to turn left a little.