checking caster angle

[firebob]

Is there an easy way to check the caster angle on my first gen firebird using simple garage tools? I've got a dial angle gauge like you would use to check pinion angle, a BFH and a couple of screwdrivers(maybe a punch if I could find it). It tracks straight down the road so I'm sure it's ok but then I'm sure I could run more if I wanted to.

Robert

[MrQuick]

how about a slip plate?

[robertjra]

ok 1/4"= .25 degrees so on most cars .5 degrees will cause a pull now caster will pull to the low side of the car so if the drivers side is 1.5 and the pass side is .5 it will pull to the right if you find the center line of your axle measure the lower ball joint to find how far one is over the other you will never get it exact oing it that way but you can get it close

[firebob]

I don't know what a slip plate is. I don't think I have one in my tool box. Does it look like a BFH?
robertjra, not sure I can do that with the rotor,caliper and backing plate installed.

Robert

[JRouche]

Ya know what, Im all about using average garage tools to make due instead of buying special purpose tools.

If you have a bubble level, a sharpie pen, a couple of slices of linoleum (no, dont go ripping your the kitchen floor up, IF you have a wife, if yer single then its an option, but the hardware store sells individual 12"x12" pieces, the self glued ones work great, the glue side goes on the tire and the floor, the shiny side goes together, with some crisco), some crisco (for the sliding plates), a measuring tape or two and one of the many methods available online showing how to check for caster and camber then its a simple process.

Oh, and a means to mark the slide plates in degrees. If you dont have a protractor you do have a computer. Is there a printer? Do a google search for degree wheel and find a picture that you like. Print it out on you printer, you may have to scale it up to be big enough, I think you can do that in the printing preferences.

It will be a lil slower than the fancy setups available, but its doable with what most folks have available.

The main diff is it might not be as accurate, but really, it can be very accurate. As long as you take your time!! You are substituting money for pricey tools that are faster for time spent dialing it in and really taking notice of the measurements.

The idea is you can determine the caster when you move the wheel from turn to turn, I think most use 20*. Im on a diff computer, my other one has many methods I got online for checking caster. If you cant find any online lemme know, Ill shoot you some decent ones.

The main problem with using simple bubble levels VS levels that are made for the purpose or digital levels is the accuracy. The more sensitive (not accurate) levels have a straighter bubble tube. Its not as curved as some of the general purpose levels. So small movements on the level show more bubble movement. And the tubes are graduated, which you can do with the super fine sharpie pen anyway, not the regular sharpie, but that one with the fine tip, art stores have the really sharp sharpie pens.

I have some very precise machinist levels, some really nice starretts, big ones. But thats a pain in the butt to try and strap that heavy cast iron unit to the wheel, I decided to use a digital level. NOT for the precision, its no more precise than many general levels. But it is sensitive and repeatable. The ability to repeat a measurement is key.

And the ability to read numbers instead of judging a bubbles placement within a tube helps me. And ONLY for speed. The eye can discern a change in bubble to graduation marks very well, more so than some peeps give it credit for.

So YES!!! You can do a homegrown caster check of your car. I actually encourage folks to do their own alignments.

Most alignment shops will be able to setup your 80s, 90s and 2000 model cars. But a 60s car just baffles them. They will punch keys in the computer looking for the setup. If its a better shop they will have hard copies of alignment specs.

Problem? We are not using 60s tires and not driving at 60s speeds, mainly the tires. And more offten than not we dont have the same 60s shocks and bushings in place. And on the extream (my case) we have compleatly different suspensions inplace.

Like my car. Its a 62 nova with a small block and a mustang II front. There is no way in hell I would drive up to a local alignment shop and say align it. To be honest, not even if they were used to working on the vast amounts of hotrods out there with MII suspensions. Because mine goes even further than that. It has a really weird rear suspension and air ride springs all around. Its just a mix mash of suspension that I dont trust them to be able to dial in to what I want. Ill do it myself.

But even a stock 60s car will throw most mainstream alignment shops into a head spin. Not good, if they dont know what to do it just makes more sense to do it yourself. And you can, even with the tools that most folks have in their garage.

If you dont have a simple level yet I think its time to get one, and while yer there pick up four slices of flooring too :) JR

[JRouche]

I don't know what a slip plate is. I don't think I have one in my tool box. Does it look like a BFH?
robertjra, not sure I can do that with the rotor,caliper and backing plate installed.

Robert

The slip plates make it so you can turn the wheels without much friction. Instead of turning the front tires on the grippy concrete surface they allow the tires to turn more freely. So the tire friction wont bind up the suspension when you turn the wheel. Nice ones also allow for sideways and forward movement of the tire so there is even less binding to screw up the measurements. JR

[JRouche]

NOW! If you have a hacksaw (oh, and a drill) in yer tool box you can also make this lil rig. I used some other tools, but to be honest, I (and you) could make the same tool. Might not look as pretty, but pretty doesnt matter. Function DOES.

Its just some simple aluminum bar thats been drilled and fastened to form a tool.

You can drill the holes and bolt the bars together, the bars could be wood. Duct tape a simple bubble level to the horizontal piece, the measurements arent critical, just as long as they are even front to back from centerline, easy.

This is a tool that can be made from wood (not plywood) and a bubble level, that will IMO get you a better alignment than you can get from most of the major mainstream Goodyear, firestone or whoever alignment shops if you have an older car.

Why? Because you get to pick YOUR numbers, and play with them.

And all of it can be made from wood for you wood workers. Some oak would be nice, ash, heck, even pine, there isnt much load placed on it. A hand held drill, some screws, two measuring tapes, a decent level, not accurate, just needs to be sensitive.



https://static1.pt-content.com/images/pt/2010/12/a-1.jpg


Next was a housing for the digital protractors. There are alot of ways to do it. I do have a cnc milling machine. But to be honest, Im still learning to draw parts up in the cad program and Im not all that proficient. So welding up a box was an option. And again, welding aluminum is new to me. So I needed the practice. Glad I did. I need to get used to welding aluminum. Steel is so different and Im comfortable TIG welding steel, time to branch out.

So I cut some plates of aluminum and clamped them up for welding. The beads weren't too bad. I HATE grinding welds down, it shows that the weld wasn't very nice. Well you get the idea, I ground down my welds LOL

https://static1.pt-content.com/images/pt/2010/12/b-1.jpg

https://static1.pt-content.com/images/pt/2010/12/c-1.jpg


Next was the vertical bars for the toe gauge. Simple cutting, drilling and sanding.

https://static1.pt-content.com/images/pt/2010/12/d-2.jpg

The lower cross bars for the toe gauge. My car has 26" diameter tires so the lower bars are 26" long for proper toe setup.

https://static1.pt-content.com/images/pt/2010/12/e-1.jpg

All the bits and pieces done.

https://static1.pt-content.com/images/pt/2010/12/f-1.jpg

This is how the protractors or digital levels set in the boxes. They are captured by small set screws that align with the Vee on the body of them. Keeps them from flopping out. The reference plane that is tight to the vertical plane is the bottom of the box. When I welded the box up I made sure the upper and lower plates of the box were perfectly square with the end plate that mates to the round spacer.

https://static1.pt-content.com/images/pt/2010/12/g-1.jpg


Then when assembled off the car this is what the whole thing looks like.

https://static1.pt-content.com/images/pt/2010/12/h-1.jpg

To mount it to the car the spud goes on first.

https://static1.pt-content.com/images/pt/2010/12/i-1.jpg

Then the 3/4" bolt is put into the box before the protractor and thread the entire assembly to the car.

Why a large 3/4" bolt? Nuther screw up. When I was boring the threaded side of the spud I ran the drill bit all the way through. Knowing I would need a hole for the connector bolt. But dummy me, I went a couple sizes too large for what I needed. I was hogging out the OD threaded side and didnt want to have to bore alot. So I used a large drill bit to remove a major portion of material. I should have stopped at the major depth on the OD thread side and kept the other sides hole smaller to tap it for a 1/2" bolt. No loss for me. But just shows planning actually works. I didnt draw it up or plan it. I just went to town cutting metal.. Just showing, it is ALWAYS a good idea to put yer build on paper.

https://static1.pt-content.com/images/pt/2010/12/j-1.jpg

https://static1.pt-content.com/images/pt/2010/12/k-1.jpg

Ok... Now the sweet part of this rig. The toe measuring. Thats why I made two of these fixtures. Hook a tape on the right side of the car and measure the left side. Its really nice. The lines are sharp enough that you can get a toe reading to within a 1/32" if you need to. And the lower arms dont flex during measuring. Its pretty stout.


https://static1.pt-content.com/images/pt/2010/12/m-1.jpg


https://static1.pt-content.com/images/pt/2010/12/l-1.jpg

https://static1.pt-content.com/images/pt/2010/12/n-1.jpg

So Im gonna go ahead and do an alignment. You see the turn plates under there. They are a must IMO. Those are full floaters. Meaning they will slide fore and aft and in and out (sideways) along with rotation all on a BIG bearing. Some Bear plates I picked up on the cheap.


Anyway, this alignment tool can be made by anyone with some simple tools. And even easier if you have a lipped wheel. No need to go with a hub mount. Hope you enjoy the pics (dont forget to click for a full image) as much as I enjoyed making this tool. JR

[neki67]

Thanks, once again you're sharing some wonderful info/ideas with us.

Thank you for all the time you put into it.

[firebob]

Wow!! Pretty cool.
So the idea is to fasten your tool, and turn the wheel right and left and take the readings off the dig level and that somehow relates to the caster angle?

Robert

[MrQuick]

if i remember the thread it was turn the wheel 20* in each direction record the numbers you get, if both number are negative OR positive, subract the lower number from the higher, if one is positive and one is negative then add the numbers together. Then multiply by 1.5 and that will give you the degree.

[firebob]

Ok. I was just perusing a couple of web pages and it looks like you're about right. So I have a pendulum camber gauge but it's the type that you hold on by hand. If I read it right, I need to turn the wheel exactly 20* to the right, record the reading, turn the wheels exactly 20* to the left and subtract the smaller number from the bigger one and that will reveal my caster angle. I guess the "slip plates"(Linoleum with greese in between and degree markings) is just to make sure of the turning angles and to allow you to do it by hand with the full weight of the vehicle on.
Doesn't sound to difficult but it will require me to source a couple of things I don't have readily laying at my fingertips. This may be the year that I scour the swap meets for some alignment tools. I might just make a run at the local tire/alignment shop to see how much they would charge just to check it.
Thanks for the info.

Robert

[MrQuick]

I have used 2 pieces of cardboard before in a pinch. You just want a smooth rotation of the tires.

just some info incase you can not turn the wheel far here are other multiplication numbers

10* multiply by 3
15* multiply by 2

Vince

[aosborn]

The only thing I would add to help sort this out is when you are checking caster, turn the front of the tire your 20 degrees inboard first and take your angle reading (if you were doing the RF, then turn the tire like you are making a left turn), then turn the front of the wheel outboard the 20 degrees and take the second angle measurement.

If when turning the front of the tire inboard (for first measurement), the tire/wheel goes more negative (inboard at the top) and then goes more positive (outboard at the top) when you swing the tire out for the second measurement, you have positive caster.

Like was stated, add the total amount of angle change by 1.5 and you will have your caster reading. Put slightly more caster on the right side (1/4 to 1/2 degree) to help the car track straighter on a crowned road, or make the measurements the same for a track car.

I have done literally hundreds of alignments, both front and rear axles, with alignment tools costing less than $100.00 (bought used turn plates years ago) with excellent results.

Andy