00firebird

iTrader: (3)

I came across the following recommendations for 4th gen Fbodys:
Mild Street Alignment:
0 Toe
-.5 Camber
+4.5 Castor

Slightly More Aggressive:
0 Toe
-.7 Camber
+4.5 Castor

Even More Aggressive:
0 Toe
-1.0 Camber
4.5 Castor

The Full Race Setup
1/32" to 3/32" Toe Out
-1.3 to -1.5 Camber (whatever max is after the castor is set at 4.5)
+4.5 Castor



I noticed The castor is never set above 4.5 in any of these setups. Is there any reason why? Will higher castor cause worse tire wear? Or does increasing it any further make no difference on these cars?

1BAD02WS6

iTrader: (-1)

Is the castor to be 4.5 on both sides? I have seen people say "you need as much castor as possible." that really does not make much sense, I would be more concerned about the castor split. I set mine to -.2 and and my car drives straight as an arrow

00firebird

iTrader: (3)

Well the frame shop I go to likes to set castor around 5.5 so I was curious how high you can really go with it. One of the guys tried to say it would be better around 9.5 "because that's what the corvettes have" I'm just trying to figure out what a good spot for it is.

DarkblueTA

I had my car aligned at a frame shop. This what they did...

Part L/R
Toe 1/32in / 1/32 in
Camber 1.0/1.1
Castor 4.5/4.6

Car tracks straight as an arrow and tread wear is good to go. The car does not wander with the ruts in the road and turns really well.

Hope this helps.

RAMPANT

iTrader: (17)

A lot of European cars can go from 10 to near 20 in caster.

My Firebird has:

caster - 6.5
chamber -1.9
toe-1/8

To get the above, I have aftermarket upper and lower control arms and the RR K member with longer slots, plus it is lowered 1.5".

It tracks pretty straight but has very fast steering response, wear is similar to the rears with 700hp, "not long"

Caster will stabilize the car, but also gains chamber the more you steer.

leadfoot4

iTrader: (1)

Caster increases straight line stability, but does increase steering effort when turning. Having said that, I'm running 5.3* left, and 5.6* right on my '96 Z-28. I don't know what Corvettes are running 9* of caster, but a C-5 Corvette calls for 7*.....

00firebird

iTrader: (3)

I ended up going with 4.5 castor, -0.7 camber and 0 toe, man I wish i did more castor. The very little effort to turn the wheel again is nice, but in hard corning there is a big difference in grip. It almost feels like I have smaller front tires on the car now. I will probably go back to 5.5 or 6.5 next time I get it redone.

1 FMF

iTrader: (1)

http://www.ozebiz.com.au/racetech/theory/align.html

i don't think caster will affect your turning grip. from looking up alignment stuff on the web caster affects the wheel's ability to want to track straight- see shopping cart example in link.
negative camber will help most i think with keeping the tire flat in a corner but i'm no expert. toe generally helps with turn in response and understeer/oversteer. rear wheel drive cars generally want more toe in because under power the front wheels tend to toe out. front wheel drive cars prefer slight toe out because under power the front wheels will pull forward and tend towards toe in and give even toe.

i know when i had my 2002 aligned, 3 times, i let the first shop do the more positive caster on the right front to compensate for road crown. was terrible, always pulled to the left. different shop 3rd time was cool and owner admitted that cars with wide tires like these need fairly accurate setups with same caster & camber numbers both sides or you notice it driving.

HoLLo

iTrader: (17)

I just replaced upper and lower LCA bushings, upper and lower ball joints, outer tie rod ends, sway bar mount bushings, sway bar end links, and KONI SA front shocks, and then had an alignment done.

My specs are:
Camber: L= 0.8, R= 0.2
Caster: L = 5.4, R = 5.5
Toe: L = -0.02, R= -0.02

Minus the steering wheel a little off, it drives straight as an arrow and hugs the corners well.. I gotta go back and have the steering wheel centered.

therealcreeper

iTrader: (37)

not to hijack but I had my car aligned recently and they said they could only get 3 degrees of caster. I'm on all stock front springs/control arms/etc, what would throw it off?

Flubyux2

Caster does more than affect straight line stability. What you can feel is that the car is heavier feeling on-center in the steerin wheel. It has a greater desire to return-to-center during a turn. So when you make a turn, the wheel wants to spin back to center quicker when you run more caster.

Running really wide tires or changing the scrub radius by altering wheel width and offset will make a car return-to-center differently. Toyo actually gives you the alignment recommendation of "as much positive caster as possible" when you buy their r888 tires. It makes a lot of sense after running 315's all the way around on my supra: making u-turns, my supra would actually spin and hold the steering wheel at full lock if i let go of it.

Also, caster affects dynamic camber. At least on some vehicles. Static camber is what is set on alignments and what we all think of and can see when the wheels are Tilted inward. Dynamic camber is what the wheel will have as steering input is given. Some cars will LOSE static camber as the steering wheel is turned. I guess technically all cars do... But for a reference, 15* of wheel angle could end up negating all static camber and the dynamic camber will wind up being 0*. More steering input, combined with body roll and suspension compression in mid-corner will result in Positive camber!

So, having more caster will allow you to Maintain as much negative camber during cornering as possible while allowing you to be modest with static camber settings.

C5ronvert

You're definitely on the right track here and I'd like to add a point or two.

With positive caster, as the car steers deeper and deeper, the inside wheel's camber goes more positive and the outside wheel goes more negative. Example, if your static camber was -1.5 on both sides, the inside camber may increase to -0.5, while the outside camber drops to -2.5! So it's a direct trade off...but wait...

During hard cornering, the outside tire needs lots of negative camber because the tire wants to roll under from the forces pushing inwards. And the inside tire needs more positive camber because those cornering forces try to roll it outward. So this trade-off is actually perfect for cornering!

If you were running a circle track - always turning to the left, you'd want to run positive camber on the left and negative on the right. So we favor negative camber on a car that turns both ways since traction is more at a premium on the outside tire.

I do a lot of alignments for auto-x'ers and most of them want to run at least 2 degrees of negative camber and as much positive caster as I can add without sacrificing camber (most cars are configured so that you can't get max camber and max camber with the same alignment - camber being the more important of the two)

I've been doing alignments since the 80's and I've noticed that caster angles have climbed steadily over the years - mostly because of power steering and better all-around steering geometry. In fact, if you pull alignment specs from 70's cars that could be equipped with or without PS, you'll see that manual steering equipped cars ran about half the caster as their power assisted siblings (1.5 vs 2.5 was typical). This was because of the increased steering effort with more caster, as mentioned earlier.

About 10 degrees is the most caster I've seen on any factory alignment.

One more interesting point: Here in the South, our roads are crowned more because we don't have to worry much about wintery road conditions. Therefore, if caster is dead even on the front, a car will drift to the right significantly. So, I often will add at least a half-degree caster to the right side. This builds in a little "push" the left to help balance out the steering. (A car will pull to the side with less caster) In fact, on some trucks, I add as much as 1.5 more caster on the right side - especially if the customer drives mostly on two-lane rural roads. Of course it will pull to the left when driven in the left lane of a divided highway.

Sorry to ramble on...

LilJayV10

iTrader: (39)

I'm surprised it doesn't pull with that much cross camber.