Setting caster

[mach1dave]

Hi guys,
got around to setting the camber today, so thought I'd check the caster, not done since I rebuilt the front end a little while back. Got one of those bubble gauge things which says to turn 1 wheel 20deg out, set bubble to zero, which I did, then turn wheel in 20deg (40 from turn out to turn in), then take a reading with bubble gauge. It read zero, when it should read about 2.5deg pos. Am I right? I know the strut is the adjustment, but to get 2.5deg pos do I lengthen or shorten the strut? Hope this makes sense!!
Cheers Guys!

 

[Vicus]

Dave,
did you put the front tires on turntables when you took the measurements? If not, the readings could be wrong.
If you don't have two turntables available, use two short pieces of laminate paneling from the last flooring on each side and put a layer of baking paper, usually found in the kitchen, between them. This will reduce friction enough to give you reliable readings.

 

[Stanglover]

I paid the big bucks and got a proper alignment done., but on my 71 Mach, he could only get +3 degrees castor. It still feels like it needs more with radial tires, but to get to +4 or 4.5 degrees, I think the best option would be to replace the UCA's that have castor built in. Shimming may work, but I think it might twist the front end too much as these were never designed for that much castor with bias ply tires (tyres).

 

[Hemikiller]

To increase positive caster, you shorten the strut rod, which pulls the lower ball joint forward. Check your tire to valance clearance when you're done.

 

[midlife]

Kitchen trash bags, folded over, work great as turntables. Be sure that the floor is level when making suspension measurements.

 

[mach1dave]

Thanks guys.
Right, having set the camber to 1/2deg either side, I will be attempting to set the caster next week. I've got one of those small camber/caster magnetic gauges and a straight edge (that sits nicely just inside the lip of the wheel rim) and a set of home made 'turntables' to take the readings. It says to set one wheel at 20deg outwards from straight ahead and set the gauge bubble to zero. Turn the wheel 20deg inwards and the reading is your amount of caster. Sound right? Now am I right in thinking that with the wheel pointing 20deg inwards, I just shorten the strut till I get my preferred reading of 2.5deg (a rough reading I took a while back told me I had zero caster).
Thanks in advance guys!

 

[Stanglover]

I have 3 degrees castor on my car and I feel it needs more. 3 degrees was the max my "guy" could get into it without shimming and I'm not sure I like that idea.

 

[rcadd1ct]

Thanks guys.
Right, having set the camber to 1/2deg either side, I will be attempting to set the caster next week. I've got one of those small camber/caster magnetic gauges and a straight edge (that sits nicely just inside the lip of the wheel rim) and a set of home made 'turntables' to take the readings. It says to set one wheel at 20deg outwards from straight ahead and set the gauge bubble to zero. Turn the wheel 20deg inwards and the reading is your amount of caster. Sound right? Now am I right in thinking that with the wheel pointing 20deg inwards, I just shorten the strut till I get my preferred reading of 2.5deg (a rough reading I took a while back told me I had zero caster).
Thanks in advance guys!

You have to remeasure after and adjustment as it needs the sweep for zero.

I have cheated and moved it a little less than half the difference then remeasured when I was way off.

Ultimately I ended up getting a Longacre caster camber gauge that magnets on the hub with the dust cap removed. You really need the level at the end of the gauge to verify it is level to the floor on both ends of the sweep.

The only thing I wish the Longacre had is the flat spot at the end of the gauge to help mark the start line on the floor.

As someone mentioned, the floor has to be level to do an alignment. I marked where the tires sat in the garage. Rolled the car out and started with 1/2” of shims in the center of the car. Then used a level and measured to the 4 wheel locations. I fought for a while getting my alignment done properly due to the drought dropping one wheel (corner of the garage) 3/4”. The car must be level!

One other tip. When you get to the toe. Drive up on ramps on the front then jack up the rear and put the rears on the same height ramps. This will allow you to get under and adjust the rod ends without touching the strings I use to make sure I set toe based on the rear wheel location. ie. 4 wheel alignment.

good luck.

holler if I can help.

edit:

I included pix of stock and 3 degree upper lca. 3 degrees moves the ball joint 7/8”

 

[mach1dave]

Thanks Chris for the very detailed info, some very good tips/ideas. Will let you know how I get on (or not)!!!

 

[rcadd1ct]

Thanks Chris for the very detailed info, some very good tips/ideas. Will let you know how I get on (or not)!!!

NP.

For the strings I used two pvc pipes cut to length

Then made a partial cut for the strings making sure the small cuts were the same distance center to center.

I have figured out the rear pvc can zip tie to the rear leaf springs.

Two jack stands hold the front pvc pipe.

I bought two of these for the strings

Irwin STRAIT-LINE Chalk Line,... https://www.amazon.com/dp/B0BWL3TW45?ref=ppx_pop_mob_ap_share

Wrap one end of the string on the front pipe. Use the chalk box weight to keep the string tight at the rear. Do this for both sides.

Adjust the strings so the car is centered exactly by measuring from the center of the hubs.

Once the car is centered measure toe on the forward and back of the front wheel. I am looking for 1/16” on each side for 1/8” total toe.

 

[Otto]

One important detail that I don't believe was covered. The order of adjustments. The first thing you set is caster, then camber and last toe. Adjusting your caster can change your camber setting. Also, if you are going to do your own alignment, you should invest in proper turn plates to do the best job possible, in my opinion. I use the Quick Trick turn plates I bought from Summit. They are currently $270. When you use them make sure to center the tires on the plates. I use the tire treads as a reference front the front as I roll onto the turn plates. After that ensure from the sides that the center of the wheel is over the zero on the degree tape. Once centered, I put a piece of masking tape on the top plates and draw a line on it to mark zero. If the tire isn't perfectly centered, the tire may shift as you turn. You will see and hear it shift.

Also, another option for using the string method is using two jack stands for the string. I prefer this method because I can center the height of the string on the front wheel and rear wheel separately, measuring off the sides of the rear wheel to ensure the string is parallel. I hope this helps.