Please Take Caster Setting Seriously!

[Vincent Hill]

I read through a lot of Alignment threads because my 1982 steered heavy like a truck and my 1976 steered light like a race car. I read through the threads and saw the same complaints. Overall there was a Lot of great advice. One person had the Caster in the 8 degree range which is seriously too much and another person has Caster in the 2 degree range which is too little.

Overall I found that my thinking of changing my readings from 6.2 to 5.8 were actually about right on track because the 1976 has about 5.5 to 5.7 degrees of Caster and the 1982 SC has between 6.0 and 6.7 degrees of Caster

Last Night I got the car back with 5.7 and 5.6 degrees of Caster and .6 Negative Camber in the front. When I drove the car it was like I was in the 1976 with light precise steering! It felt GOOD!

The reason for this thread is I saw that several people would state to someone that had about the same amount of Caster I do to " Take a Degree Out of it" They took .5 degrees "out of it" and the car is now knife edge quick. If I had taken 1 degree or Double the amount the car would have become twichy and unstable. I was actually looking for 5.8 degrees of Caster and ended up with a little less!

Just imagine if I had stated take a degree and ended up with 4.9 to 5.1 degrees of Caster? A little is a lot and do not make changes of more than 3 to 5 TENTHS of a degree at a time on the Caster. This is all about the Stability and safety of this vehicle and is not to be taken lightly!

[Peter Zimmermann]

Vincent; your post makes more sense than many that I've read. I can't tell you how many years have passed that I've been recommending settings in the 0.8 to 1 degree negative range for front camber for cars of your vintage (my '82 is set at 0.8 negative). After setting the camber, and then the toe (to zero), what is the typical caster measurement? Usually in the 5.4 - 5.7 range, more is usually not obtainable. Safe, predictable, and easy to drive fast. Great post!

[Talewinds]

That's very interesting stuff!
I just did turbo-ties and bump-steer spacers on my 88' and then had the toe set properly by a shop. Although the new tie rods and bump-steer made great improvements in some areas, I'm left wondering why my steering is now SOOO heavy.
Any advice?

[BoxsterGT]

Go all the way and get a full alignment, not just toe. Every setting is important.

Len

[Helios59]

Timely thread. I'm getting Turbo Tie-Rods and new suspension bushings on my '86 Turbo-Look

What would be the recommended camber and caster settings? I have the Turbo suspension, with 205 front tires and 245s at the rear.

Thanks!

[Vincent Hill]

This IS scary! The reason for me being there was "I" just changed to the Turbo Tie Rods and also wanted the front of my car Raised so it would have 1 degree down bubble (Full Tank seats empty means it will be a little lower driving)

(BTW, I also installed 8 MM Grease fitting to the tie rods and Ball joints! The 1/16 Pipe tap is a perfect match and do not screw the fittings in more than 1/2 way they could rub the parts inside)

I use Piper Motor Sports near Dulles Airport that is 45 miles away from my house and would go there if they were 100 miles away! They have a great flat table with the Alignment machine and can set everything.

The only reason I have .6 neg Camber is they could not get .8!

I wanted 5.8 degrees of Caster and got 5.7 and 5.6 on the Drivers side (I think that makes it straight on a slightly crowned road)

I do not have my sheet, but yes all 4 wheels were aligned and you can falll asleep and be safe if the road does not turn! The Steering is very well weighted now slightly heavier than the BMW 320I which has a max speed of 100 vs a max speed of 150. I will post the setting next week when I am back from Ohio and have the sheet.

#1, do not go much below 5.4 to 5..5 on Caster and no need to go much above 6.1 to 6.2 in Caster the steering effort is just excessive for NOTHING!

[KTL]

I'm not sure why this is "scary?" Yes caster makes a big difference and the steering feel can be changed drastically w/out much change to caster at all, as nicely detailed by Vincent. However if the steering is light or heavy, the postive caster still provides the desired self-centering effect.

Plus the light or heavy steering is somewhat of a preference depending on the car's target environment. On a track car, the heavy steering is more precise as the inputs are much quicker. On a roadgoing car, the light steering is nice for around town manuevers such as turning sharp corners or parking the car.

[d.a.autry]

It's 'scary' that everyone else has gone with the turbo rods/bump steer kits. . . all at the same time . . I think that's what he means.

Great minds perhaps??

[jpnovak]

I did not realize that Caster settings were so sensitive.

While on the subject of caster. What is the best method for measuring caster at home? Strings are easy to setup for toe and digital levels make Camber a snap.

Do you put your digital level on the strut tube?

Do you measure at the wheel center and take the difference between angle with a 20deg steering angle on each side (40 deg total)?

Toe-plates are easy enough to setup. Just two sections of sheet steel and a dab of grease work great. Recycled Formica counter tops also work well and can be build to hold scales.

[KTL]

Jamie,

Here's how I measured mine with the strings

http://www.smartracingproducts.com/pdfdocs/caster_layout_template.pdf

http://www.smartracingproducts.com/pdfdocs/011410_smartstrings_manual.pdf

[Vincent Hill]

Originally Posted by d.a.autry

It's 'scary' that everyone else has gone with the turbo rods/bump steer kits. . . all at the same time . . I think that's what he means.

Great minds perhaps??

AMEN!! On Everyone at the same time and wondering the same things about the settings!

Slightly OT, We have all seen the Universal Joint Rubberband Tie Rods on the 911, but when I went to change the Tie Rods on the 1982 BMW 320I, They were "Exactly" the same parts as the Turbo Tie Rods. The BMW has good Tie Rods and shifts great but has the Sway bar as the Brake reaction Rod through Rubber bushings that go bad about every 10 to 20,000 Miles! (I resolved this problem by installing Huge thick greased washers on both sides of the control arm and this was about 80,000 miles ago.

Every car has their weak and strong points and I MUCH rather drive the Porsche!

[Vincent Hill]

Originally Posted by KTL

I'm not sure why this is "scary?" Yes caster makes a big difference and the steering feel can be changed drastically w/out much change to caster at all, as nicely detailed by Vincent. However if the steering is light or heavy, the postive caster still provides the desired self-centering effect.

Plus the light or heavy steering is somewhat of a preference depending on the car's target environment. On a track car, the heavy steering is more precise as the inputs are much quicker. On a roadgoing car, the light steering is nice for around town manuevers such as turning sharp corners or parking the car.

You hit the "Other" Nails on the head! MUCH easier to drive in town and Park! But in my case the steering was Sooo Heavy, I do not think I would have the strength to do a race, my arms would be Wooore Out!

[Talewinds]

I just checked the alignment report, after they made adjustments my caster was, Left: 5.98, Right: 5.89.

Seems fine to me............ ?

[Tyson Schmidt]

A car's sensitivity to caster settings is heavily dependant on the tires being used.

[d.a.autry]

Originally Posted by KTL

Jamie,

Here's how I measured mine with the strings

http://www.smartracingproducts.com/pdfdocs/caster_layout_template.pdf

http://www.smartracingproducts.com/pdfdocs/011410_smartstrings_manual.pdf

I've thought about the smartcamber. I've made my own string setup and have had good luck.

KTL. . . have you ever had your alignments with this cross-checked with a machine??. . .If so what were your thoughts on it?

[Peter Zimmermann]

Back in the mid-eighties I ran an SCCA E/P 914 in Regionals and Nationals. I took the car to a then-prominent alignment shop for a very specific set of settings. The following race weekend was at Riverside Raceway (yeah, the famous one), and I spun exiting turn 6 after getting up to speed. I actually didn't know how it happened it was so quick (and I never made a habit of spinning on the exit of slow corners), so I became cautious and didn't have a good weekend.

Back at the shop I got out the strings, leveling plates, camber gauge, 180 pounds for the driver's seat, etc. Five hours of crawling around on the floor later I found the problem. The alignment shop had given me a car that was a parallelogram. I never trusted that shop again, and finished the season winning 6 of the last 8 races using a set-up that I didn't have time to do, but had to do it anyway.

All of you guys who use string and assorted hand tools to get your wheels going in the right direction, my hat's off to you.

[Flieger]

My car has 6.4 (left) and 7.6(right) degrees caster. I will be getting an alignment soon after installing monoballs and Rebel Racing A-arm bearings. I am thinking of shooting for 6.4 equal. You guys are saying not more than 6. I like the steering weight, in fact it could be heavier. Should I go for more than 6.4 or maybe even more than 7.6? I think it is just personal preference.

[Vincent Hill]

Originally Posted by Flieger

My car has 6.4 (left) and 7.6(right) degrees caster. I will be getting an alignment soon after installing monoballs and Rebel Racing A-arm bearings. I am thinking of shooting for 6.4 equal. You guys are saying not more than 6. I like the steering weight, in fact it could be heavier. Should I go for more than 6.4 or maybe even more than 7.6? I think it is just personal preference.

That is a fairly big deviation First make sure they can set it at 6.4 I sure would not go for 7.6! Like someone said, certain tires make the feel heavier than others. Also some tires will slide and chatter when making tight turns. You must be one very strong person and do not Parallel Park!

Peter, Back in 1981 or 82, I got my First National Road Race points in AMA Motorcycle racing at Riverside! The only thing I did not like about being there was the Bad Air! By the end of the day, that mountain would dissapear and after the racing, I would drive through a mountain Pass where I could not see the air BEFORE I would rent a room at a hotel! I liked the Carousel where they had the stands and then the drop to the Back straight! I hated to see that course go!

[Flieger]

Actually, the steering is quite light at low speeds, much lighter than my 1983 BMW 320i with manual steering. In high speed turns, the steering weights up nicely but it is never "heavy". I am not sure why the variation and it does concern me. I have good reason to suspect a very poor corner-balance and the alignment was done prior to a brake refresh so it may have been trying to counter a pull from a sticking caliper.

I do notice a very strong connection with the front tires, which I like. In a turn, I can feel them starting to work harder as I turn-in or if I get on the throttle too early. It keeps me trying to drive easy on the tires and smooth.

I am doing monoball strut top bearings and Rebel Racing A-arm bearings to go with monoballs in the rear so when the corner-balance/alignment is done the settings should be more precise and stable.

I suppose since I never really complain about the steering feel while driving, I should just stick with what I am used to.

I think I will try for equal 6.4 degrees and see how that feels with the new suspension. I will report in a couple weeks when the work is done.

[Vincent Hill]

Again, this is scaring me because I have a 1982 - 320I and it steers a LOT lighter than the 1982 - 911 SC. The BMW feels like I have Power Steering by comparrison to the 911. I also have Toyo Tires that are great in the Wet but love to catch small stones in the dry! I have Cheap NTB tires on the BMW but this should not make this huge of a Difference?