Coldmale

Guys

I know this has been discussed to death and I know that caster is adjusted using the 4 washers (2 each side) at the upper arm mounting.

OK

I have 8 deg caster and shed loads of camber so dropping some is no problem

The question is. To reduce caster to say 6 deg do I remove from the front 2 and add to the back, or do I remove from the back 2 and add to the front?

Thanks

Apologies if this appears a ridiculous question

John

dbratten

To reduce caster you want the upper ball joint to move forward in relation to the lower joint. You want to remove from the front and/or add to the back on the upper A-arm.

--Dan

Coldmale

Thanks for that

John

davidfarmer

you can also do the opposite on the bottom concentrics, rotating the lower ball joint rearward

Coldmale

So i started with approx 8 deg Caster both sides. I had no washers left in so I added 2 to each of the rearward top arms

Guess what

Passenger side caster dropped to 7deg 20min and camber reduced by 15min, all as expected - but:-

On drivers side Caster INCREASED to 9deg 30 min, camber and toe remained unchanged
So we measured the car from bacl wheel to frnot and drivers side is 8mm longer. But the car drives perfectly straight.

Explain all that if you can?

John

meldog21

I can explain it easily. When I had my car set up by a local race shop I noticed a similar discrepancy with unequal shims and camber plates to achieve equal side to side set up numbers. The head tech told me that Corvettes are usually like that, they're just not made that perfectly. He advised me that if I wanted a car that is more exact with closer tolerances I should buy a Porsche. He said the Porsches he sets up are the opposite. Normally they use the same adjustments right and left, and few of them need uneven adjustments to achieve equal set up numbers. I decided to save my money and keep the Corvette while I also keep kicking the crap out of Porsche's at the track.

Use whatever adjustments you need to get your desired set up and don't sweat the details too much.

Dog

Coldmale

DDog

Understand the logic, but dosnt explain why adding washers to drivers side rear INCREASED the caster

By your account, adding to the front would decrease?

Pain in the butt cause I have to do all this a night, then go to the alignment shop the next day. Tedious stuff.

dbratten

I recommend that you check out David Farmer's web site and download his Alignment Guide so that you can adjust and check your settings yourself. His methods easily get you close enough on your settings. More than that is a waste of time. PayPal him a few bucks if you like what you read.

--Dan

trackboss

I wouldn't say the cars are not straight as suggested by the alignment guy. What I would bet is that the lower arms have something to do with it. If they are not solidly mounted with really hard bushings or monoballs they can very easily not be the same side to side. Also, if the eccentric bolts are still used that is another area where things may not be the same. In addition, there is some wiggle room in the crossmember so it may very well not be absolutely square. The lower arms and crossmemeber are what would change the wheel base from one side to another.
I haven't even bothered squaring mine yet. It is as it was delievered from gm almost eleven years ago. They don't square them from the factory.
The camber cannot be 9*. Your numbers are incorrect. Another thing I will say is that the car must be on a level plane because all the measurements are relative. I do all my setups manually so if something is off it is me and not my equipment. Bubbles and tape measures don't lie.
I would say it is not impossible for an alignment machine to be out of spec or not perfectly level. In addition, the slip plates must allow the track width to change by a lot. Corvettes have a lot of droop when lifted. The track width narrows quite a bit with the car up in the air. The leaf spring hardware can also bind. The car needs to be completely settled to do a proper setup.

Coldmale

trackboss

Thank you, but much of your response is incorrect because I didnt tell you everything
1. Its the caster that is 9 deg, not the camber
2. The alignment was done in a pro shop on a proper jig with all teh flashing lights and such. I can only assume that the platforms were level
3. In the previous alignment, ie, before I added the washers, everything was perfect and close enough to equal side to side
4. As such, it had to result from adding the washers. That is all that was done

John

JDIllon

Also spend $60.00 at Sears and get a 24" digital level with a laser and you can do everything in Dave's directions and get them dead on. Just my .02. I do all of my own set up with Dave's info and the Sears level. JD

gkmccready

Don't assume this. I let a local Wheel Works align my Tahoe. Same thing, nice fancy alignment rig. They were so sloppy they didn't even get camber in spec even though the machine flagged the error big and red and there was plenty of room left on the adjuster either direction.

C6RAPTOR

JD,
I am also trying to do all my DIY set up. So fare so good.
You have been a DIYer for many years and have a gift of being a great teacher. Why done't you do a photo training post with all you have learned from Dave and your own experience.
C6RAPTOR

gkmccready

What surface are you doing the alignment on? Is it perfectly level? Side to side and front to back?

kmagvette

Ensure that the upper control arm is in the same position after every adjustment. On the C5, my upper will slide fore and aft with the bolts on the upper loose. I always make sure I slam the upper to the rear before tightening.

Hope it turns out being something easy like that...good luck.