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Old 05-24-2019, 07:15 AM
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Caster adjustment

Just halfway through aligning my front end. I understand how it all works with caster, camber etc. But I am not sure if I’m measuring positive or negative caster. I turned the tires 20 degrees, zeroed the camber reader against the wheel, then turned in the other direction 20 degrees. I came up with 1.5 degrees of wheel tilt “outwards” at the top. Am I reading positive or negative? I assume it would be positive because that is a positive camber measurement when the top of the tire tilts outwards. Also, the tenhulzen kit I have for alignments says in the instructions for some reason you multiply the number by 2? Thanks

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Old 05-24-2019, 07:24 AM
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If the wheel/tire tilts outward at the top when you turn the steering wheel in that direction, that's positive caster.

Just like a bicycle.

I don't know the reason for "times 2".
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Old 05-24-2019, 09:08 AM
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Thanks, that was what I figured, just wanted to double check!
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Old 05-24-2019, 10:16 AM
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Yes that would be correct. I'm also not familiar with that method of measuring. I have never done one at home but if I wanted to measure caster I would run a straight edge along the steering axis (probably upper to lower ball joint) and check it with an angle gauge. As long as it's positive and both wheels are about the same itshouldn't matter much if it's in spec. Especially if this is an older vehicle that originally had bias ply tires but now has radials many people like a little more caster.

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Old 05-24-2019, 05:19 PM
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Thanks it’s an aftermarket mustang ll front end with radials. I got about 1.5 positive and both sides, zero camber and 1/8” toe
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Old 05-27-2019, 12:33 AM
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little clean up for you,,,
look at a shopping cart wheel? the tire wanting to track straight is "Caster"
The top of tire tipping away from the car is positive "Camber" Thats sideways,,,negative camber is when the top of the tire is pointing towards engine

Positive Camber requires toe in
negative Camber requires toe out
The left side of the car should have 3/4 more Caster to compensate for road crown, other wise the car will drift to the right. Radial tires require less descrepency and spread as they have lower rolling resistance. If tire width is different or wheel width and spacing is different then factory specs will not be correct. Same applies to cars that are lowered or raised. Big 20" wheels and other harsh mods can make your car impossible to drive safely
Look up SAI, steering axis inclination (about 7 times) then you can custom align your wheels.
If you drag race then you may have to jack up the car slightly while doing an alignment
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Old 05-27-2019, 10:20 AM
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1.5 caster doesn't sound like much, but I don't know if different front ends makes a huge difference there? My 55 Bel Air started responding and handling well when I got it up to +5. They came new with 0 +- and wondered all over the road till they came out with a service bulletin saying to take it up to about +1 for those with power steering which mine has. But that was then. They also showed how to set up to bend the frame if you couldn't get it as high as +1. I believe some newer Vettes have +5.
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Old 05-27-2019, 10:37 AM
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Many tubular upper control arms are set for 6 degrees.

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Old 05-28-2019, 06:19 AM
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I was able to crank about 5.5 into my 38 (84 Corvette suspension) and it goes down the road very nicely. My Vette is running 7 degrees.

My buddy has a 38 Plymouth with a Nova Front end, he can only get about 2.5 degrees in his and it drives well, but takes a little more work to keep it in the lane.

If you have power steering run as much as you can. High caster numbers and wide tires make manual steering very difficult.
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Old 05-28-2019, 07:26 AM
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I believe the tci specs called for 1 degree with a manual rack
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Old 05-28-2019, 07:49 AM
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Quote:
Originally Posted by lt1tyrell View Post
I believe the tci specs called for 1 degree with a manual rack

More caster will handle better but like said it will go down the road straight much easier, but with no power steering it will make it harder to turn for parking and such maneuvers.


I never thought of it before, but maybe that's why my work van (Chevy 3500) is such a ****** to keep in my lane? Too little caster?
Anyone know how to adjust caster in my Chevy 3500 van? Maybe I could figure it out if I looked good and hard at it?
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Old 06-07-2019, 07:12 PM
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Quote:
Originally Posted by 55 Tony View Post
1.5 caster doesn't sound like much, but I don't know if different front ends makes a huge difference there? My 55 Bel Air started responding and handling well when I got it up to +5.
I had the same problem with my 55 sedan. Max caster I could get w/o messing up camber was less than 1 degree. Ended up going with aftermarket control arms and got >4 degrees. Huge improvement in straight line stability! Might have been harder to turn at low speeds with manual steering, but not a problem with pwr steering.
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Old 06-07-2019, 07:35 PM
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Quote:
Originally Posted by 55 Tony View Post
More caster will handle better but like said it will go down the road straight much easier, but with no power steering it will make it harder to turn for parking and such maneuvers.


I never thought of it before, but maybe that's why my work van (Chevy 3500) is such a ****** to keep in my lane? Too little caster?
Anyone know how to adjust caster in my Chevy 3500 van? Maybe I could figure it out if I looked good and hard at it?
If your van is like the trucks the upper a arm has shims add and remove shims to adjuat castor and camper.
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Old 06-07-2019, 08:12 PM
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The newer ones probably starting around when the ls came out have eccentrics on the upper control arm bolts. With shims you add to the front and remove the same thickness from the back. Theoretically you can do the same thing with the eccentrics on newer ones (up to adjust in and down for out) but it's not a linear adjustment so there would be more trial and error.

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Old 06-08-2019, 05:05 AM
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Quote:
Originally Posted by timothale View Post
If your van is like the trucks the upper a arm has shims add and remove shims to adjuat castor and camper.

I've only had it aligned once in 100,000 miles and it was before I ever did my own alignment on the 55 and learned a little. They called and told me if I wanted it right, they would have to order some special shims (or something) and it was going to cost an extra $100, but it would never need THAT adjustment again. I swear if I ever buy a new vehicle again, I will tell them I want it 4 wheel aligned and I want the printout sheet to prove it.


Next up is my 20 year 100,000 mile tune up. (I think it was supposed to be 5 or ten years or 100,000 miles) Still runs like it always did, if it wasn't a van I'd have done it, but Chevy vans aren't fun. (unless you are back in the 70's in the back of your Chevy van!)
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