Fastrax review and alignment questions for the pros.

[adriver]

Last summer I replaced the pitman and a tie rod end on my daily.

I just guessed and eyeballed the toe hoping it was good.

But I noticed the car was hunting on the interstate.


Since I will need to align front ends on two other vehicles I’m building, I bought these from Summit. Best price and free shipping. Summit supports our car club.
I also like "low tech". I trust spirit levels. And no batteries.

Sure enough my daily was a hair toe out.

I’ve set toe now to “factory” of 1/8 inch in .

Now the car and me are happy.

I’m generally impressed with the Fastrax and feel they are worth the money if you like DIY and not relying on other people.

But I’ve never really studied alignments before.. I’m posting so people with more experience than me can give some input.


Here’s what I can tell you about these.

1. They are not robust. Light weight and aluminum.
2. They are easily knocked off the rims. Use caution working around them.
3. I bought one for each side. It seemed to make the whole process easier. But they don’t clamp very hard on the rims (Number 2 above) So unless you have someone to hold the tape on the other side of the car you may have to do what I did and mark the floor and use a plumb level to see where the arms are to check toe.
4. To set castor the instructions say to turn the wheel 15 degrees or make the pointer parallel to the side of the car. I’m thinking how much one turns the wheels will make a difference on what will show up as castor in an alignment. I think this is because the castor reading is a factor of how much “change” the tool sees when the wheels are turned. I’ve seen videos that specify a different amount to turn the wheels to measuring castor with similar tools.. I don’t know what would be right otherwise.
5. All the alignment numbers in the factory manual seems to be in degrees except toe. I don’t understand two things about this. (1) IF toe is given in degrees, I’m thinking it makes NO difference how big a wheel is. Degrees off from center for the tire to the car would stay constant. (2) But by giving toe in inches ACROSS the car lines, it seems there would be some “error” due to different tire sizes between car lines. It would compound the error if bigger tires were used. This is what I did not know for sure about my car. The car has 15 inch tires now. Bigger than any A body came with. If we are given toe in inches it seem it would make a difference how big the tire is or where you measure.
6. Pictured are two alignment sheets from two different shops a few years apart. Why is “specified range” for total toe different? It’s in degrees as well. So, as I’ve noted in 5 above I think this would be a “constant” for any vehicle in that group.

 

[694spd]

Car hunting on interstate. For one thing you want a positive caster. Something like +1 to +2 degs positive, if you can get it. The caster specs that are listed on alignment sheet are a joke. Look at the spec range on the sheet -1 to 0 degs. No way... I have argued with a few alignment shops over the specs in their machines.
As far as toe, it is always given in inches. I too have wonder why it is not in degs which would make more sense. How far out from the ball joints is the 1/8 inch toe read? I would like to know also.

 

[adriver]

I understand the toe in "inches". I can measure that.
But how would it be possible to measure toe in degrees with this type of fixture?
From a quick net search it appears like I have to use toe in inches, tire size and a formula.
So, I have to know the diameter of my tire?
At this point, I'm thinking the alignment shops are guessing numbers to put into some machine to get degrees.

 

[adriver]

That 2008 sheet is what I've supposedly been driving with till this summer.
No issue with handling or tire wear.
I can't say the figures are "true" though.
I did a quick check with the Fastrax and the figures I got were different from the sheet.
That's part of the question of how much do I turn the wheels to get castor.
I turned them different amounts and got different castor readings.

 

[adriver]

Ok, I'm an idiot.
But no one caught it.
Or, at least was too polite to point it out.
So either way, thank you or shame on you.
We are way smarter than this.
(Apparently Rusty didn't view this thread or I would have be severely called out.)

I was putting them on wrong.
Well, maybe there is not a right way.
But this worked way better.

I noticed my tires had begun to wear on the outside instead of the inside as before.
When mounting the Fastrax this other way, I found too much toe in.
It was more than 1/8.
Forget what though.
I'm still figuring this alignment thing out, so bear with me.
After much tweeking and a little twerking I got it down to 2/16 and tried to take another 1/16 inch out of it.
Maybe I did, but I was running out of time.
More will probably follow as I use them more.


Again, where does one measure when the tires are bigger than what came on the car?
Who knows?
All I can say is I can not see how doing this with a piece of string or measuring the tire tread would really work very well.
It's really sensitive.
And I would be crawling under string?
This time I confirmed the fixtures were on correctly by measuring.
But they still are knocked off easily by your head.
I managed to do it once on either side while crawling under to adjust the tie rods.
More will probably follow as I use them more.

 

[67Dart273]

You should be measuring "about inline" with the spindle. I simply use a scribe which you can build. Jack up one tire at a time, barely off the ground, under the LCA. "Anchor" your scribe and rotate the tire to provide at least two marks 1/2 turn apart (180*) on each tire. Then tape between, the difference, etc

Because I'm usually working alone, I actually bought a toe gauge, although you can build one. This one turned out to be for large trucks, and I had to saw it down it was too tall

This is the scribe and toe gauge I bought off egag

I scored some beat up Ammco turning plates and caster/ camber gauge here locally

You don't really need this fancy stuff but you DO need an angle gauge to measure camber. Caster is figured mathematically by turning the tires in and out I believe its 22.5 degrees, take the difference in camber readings, and multiply by 1.5 to get caster. Search it you can find destructions on the net

 

[67Dart273]

"Crackedback" I believe on here does it more simply. He jacks up some cans to support 2x4's against the outside of the tires, then just measures across between the boards. Works for him

 

[adriver]

You should be measuring "about inline" with the spindle. I simply use a scribe which you can build. Jack up one tire at a time, barely off the ground, under the LCA. "Anchor" your scribe and rotate the tire to provide at least two marks 1/2 turn apart (180*) on each tire. Then tape between, the difference, etc

Because I'm usually working alone, I actually bought a toe gauge, although you can build one. This one turned out to be for large trucks, and I had to saw it down it was too tall

This is the scribe and toe gauge I bought off egag

View attachment 1715096483

I scored some beat up Ammco turning plates and caster/ camber gauge here locally

View attachment 1715096484

View attachment 1715096485

You don't really need this fancy stuff but you DO need an angle gauge to measure camber. Caster is figured mathematically by turning the tires in and out I believe its 22.5 degrees, take the difference in camber readings, and multiply by 1.5 to get caster. Search it you can find destructions on the net

I hate you.
You always find cool tools second hand.
I'm using greased poly sheets for turn plates.
"I got nothin'".
That's why I bought the Fastrax with spirit levels.
And since I did that I sprung for the toe adaptors.

Did you notice the original conundrum?
Chrysler gives the toe specs at "1/8" in across all car lines.
But since tires vary in size where does one measure since going father out will compound the distance of toe.
It looks like alignment shops convert toe into degrees.
That would be a constant and it wouldn't make any difference what tire size was on a car.

 

[67Dart273]

I hate trying to convert degrees/ linear. All the "old" specs........along with the popular "skosh" chart is in inches.

 

[72bluNblu]

I use the fastrax caster/camber gauge for doing the alignments on my cars. I have a magnetic gauge too but it doesn’t work on my Duster with the aluminum hubs and wheels . I have a set of turn plates I also found second hand, super helpful. Although some greased plates works fine too, you just don’t want anything binding up. I measure the toe using a set of longacre toe plates. There’s no way I would try to set the toe off the fastrax gauge, it doesn’t hold to the rim with enough force to pull an accurate, repeatable measurement. Plus you’d need two, and I only bought one. Toe plates were cheaper than buying a second gauge
Longacre Toe-In Plates 79501

As for the toe, yes, it does change with tire height. Well, assuming you’re not using toe plates like I am, in which case the toe plates are always the same size. But the difference is pretty small. Degrees is more accurate for sure, but so are the digital racks the alignment shops use to get the toe in degrees. And it’s not a huge difference. For example, if you change the tire height from 25 to 26” with 1/8” total toe in, the total change in degrees is for both wheels is only .009. If you change the total toe from .125” to .120” with a 26” tall wheel, the total change is .011. I can’t measure to .005” with a tape measure, so, you know why the factory didn’t worry about changing the toe setting for different tire heights.

You can play around with this calculator to see what I mean. Degrees is more accurate, but you can’t measure that accurately with a tape anyway.

Convert Toe Inches to Degrees

 

[Bodyperson]

The diameter of the rotational plane does not effect the toe angle because you are measuring the difference between the front and the rear. 0 is 0 no matter how far it is projected. It can be measured in degrees or inches, just go into the preferences and pick which one you want. Hell you can measure it in millimeters if you want. The computer is measuring it in degrees and converting it to inches of mm for us.
Degrees are measured from the center-line of the car and can be more accurate as it eliminated part of the inch measuring equation plus now we are measuring individual toe instead of total toe.

 

[adriver]

I use the fastrax caster/camber gauge for doing the alignments on my cars. I have a magnetic gauge too but it doesn’t work on my Duster with the aluminum hubs and wheels . I have a set of turn plates I also found second hand, super helpful. Although some greased plates works fine too, you just don’t want anything binding up. I measure the toe using a set of longacre toe plates. There’s no way I would try to set the toe off the fastrax gauge, it doesn’t hold to the rim with enough force to pull an accurate, repeatable measurement. Plus you’d need two, and I only bought one. Toe plates were cheaper than buying a second gauge
Longacre Toe-In Plates 79501

As for the toe, yes, it does change with tire height. Well, assuming you’re not using toe plates like I am, in which case the toe plates are always the same size. But the difference is pretty small. Degrees is more accurate for sure, but so are the digital racks the alignment shops use to get the toe in degrees. And it’s not a huge difference. For example, if you change the tire height from 25 to 26” with 1/8” total toe in, the total change in degrees is for both wheels is only .009. If you change the total toe from .125” to .120” with a 26” tall wheel, the total change is .011. I can’t measure to .005” with a tape measure, so, you know why the factory didn’t worry about changing the toe setting for different tire heights.

You can play around with this calculator to see what I mean. Degrees is more accurate, but you can’t measure that accurately with a tape anyway.

Convert Toe Inches to Degrees

The Longacre plates look like a good idea.
Yes.
I found out the Fastrax don't grip very hard.
I did buy two.
Mainly because when setting up a front end it seemed like it would be a PIT to swap from side to side and reset the thing for zero on each time.
And I'm doing it by myself so I'm laying the tape on the floor and using a level to find the position.
I hope I can get accurate enough.
The instructions say to turn the wheels 15 degrees, or make the pointer parallel to the car to measure castor.
I found that turning the wheels more will also make a different reading for castor
So, I'm thinking 15 degrees must be designed into the fixture some way because it is looking at the difference between straight and turned.
Any input on why recommendations are different for how much to turn the wheels for a castor measurement with different alignment tools?

 

[69_340_GTS]

...Chrysler gives the toe specs at "1/8" in across all car lines.
But since tires vary in size where does one measure since going father out will compound the distance of toe.
It looks like alignment shops convert toe into degrees.
That would be a constant and it wouldn't make any difference what tire size was on a car.

It's not that fussy. Just measure it directly.

 

[adriver]

It's not that fussy. Just measure it directly.

At this point, I'm thinking most of the problem is my learning how to use these particular tools with their quirks.
I mean they seem accurate enough, yet it's not for the faint of heart.
But DIY is a reward.
I've got vision of repeat trips to the alignment shop which takes time and money as well.
Those Longacre racks look like a fun option.

 

[72bluNblu]

The Longacre plates look like a good idea.
Yes.
I found out the Fastrax don't grip very hard.
I did buy two.
Mainly because when setting up a front end it seemed like it would be a PIT to swap from side to side and reset the thing for zero on each time.
And I'm doing it by myself so I'm laying the tape on the floor and using a level to find the position.
I hope I can get accurate enough.
The instructions say to turn the wheels 15 degrees, or make the pointer parallel to the car to measure castor.
I found that turning the wheels more will also make a different reading for castor
So, I'm thinking 15 degrees must be designed into the fixture some way because it is looking at the difference between straight and turned.
Any input on why recommendations are different for how much to turn the wheels for a castor measurement with different alignment tools?

Ive gotten pretty quick at attaching and zeroing the gauge. As long as I don’t kick it when I move around the car to make adjustments it stays on . I like the longacre toe plates, they make it pretty easy to measure the toe even by myself. Once you get your method figured out it’s easy to be repeatable.

As for how many degrees to turn the wheels to measure caster, it doesn’t matter that much. What really matters is that you turn them the same amount in each direction. Most gauges use 20*, the more you turn the wheels the more accurate the measurement will be. Not sure why fastrax uses 15* instead, but it’s not something built into the gauge. You’re actually measuring the change in the camber between the two wheel angles, which is telling you the caster.

Here’s a decent article on alignments and some of the definitions DIY Alignment Guide - How To Adjust Caster - Hot Rod

And here’s one that’s very technical. Like hard to read technical. It actually works through deriving the equations for how the process for measuring castor works.

https://disco3.co.uk/gallery/albums/userpics/24543/steering-geometry-and-caster-measurement[1].pdf

What all that math gobbledegook means though is that the turn angle doesn’t matter as long as it’s symmetric, but a wider turn angle spreads your measuring errors over a wider range, so, more accurate.

 

[67Dart273]

Actually the degrees you turn the wheels when measuring caster DO MATTER

I didn't find the formula.......which I don't use, but I did find these figures for popular steering angles.........

Angular value constants

• 20 degrees = 1.5
• 15 degrees = 2.0
• 10 degrees = 3.0

I was taught 20 degrees. I was thinking it was 22.5, don't know why. "Somewhere" I have the old, tattered original Ammco destructions for my gauge

 

[72bluNblu]

Actually the degrees you turn the wheels when measuring caster DO MATTER

I didn't find the formula.......which I don't use, but I did find these figures for popular steering angles.........

Angular value constants

• 20 degrees = 1.5
• 15 degrees = 2.0
• 10 degrees = 3.0

I was taught 20 degrees. I was thinking it was 22.5, don't know why. "Somewhere" I have the old, tattered original Ammco destructions for my gauge

All of the formulas are in the second link I posted. It’s an excerpt from an SAE paper. It literally explains everything. Maybe too much, I got a little lost in the weeds. For the math, it doesn’t matter.

In my haste speed reading the SAE paper I missed how the calculation is simplified for use with the mechanical gauges. With the bubble gauges, the scale on the gauge for reading caster is predetermined by the turn angle. The calculation can be done for any turn angle, but with the mechanical gauges the calculation has been simplified to the point that a predetermined angle is used to set the scale on the bubble gauges so you don’t have to do the math.

So, you have to use the angle specified for your gauge. Most of the older gauges use 20*, the fastrax gauge uses 15*.

The digital gauges can use any angle they’ve been programmed for. And the math can be done for any angle you want, but then you’d have to suffer through doing the calculation.

 

[famous bob]

All of the formulas are in the second link I posted. It’s an excerpt from an SAE paper. It literally explains everything. Maybe too much, I got a little lost in the weeds. For the math, it doesn’t matter.

In my haste speed reading the SAE paper I missed how the calculation is simplified for use with the mechanical gauges. With the bubble gauges, the scale on the gauge for reading caster is predetermined by the turn angle. The calculation can be done for any turn angle, but with the mechanical gauges the calculation has been simplified to the point that a predetermined angle is used to set the scale on the bubble gauges so you don’t have to do the math.

So, you have to use the angle specified for your gauge. Most of the older gauges use 20*, the fastrax gauge uses 15*.

The digital gauges can use any angle they’ve been programmed for. And the math can be done for any angle you want, but then you’d have to suffer through doing the calculation.

I didn`t read all these posts, but u can set toe in very accurately W/ A TAPE MEASURE AND A PAIR OF EXTRA HANDS . Its the easiest of all alignment settings .a

 

[67Dart273]

I didn`t read all these posts, but u can set toe in very accurately W/ A TAPE MEASURE AND A PAIR OF EXTRA HANDS . Its the easiest of all alignment settings .a

He/I are not referring to toe, we are talking about calculating caster from a camber gauge. The Ammco caster / camber gauge is essentially a circular slide rule. You don't actually need any of that, only the angular measurement, and then multiply X 1.5 after your 20 degree swing readings, etc. to get the caster reading from the camber measurements

I believe I found this same info in a Longacre pdf

https://www.longacreracing.com/instructions/text/78250PI.pdf

Any of the modern, cheaper caster camber gauges have this formula "figured into" the caster readings. Some gauges are 20 degree swing, some are 15

OF COURSE there's a YouTube video, LOL

 

[adriver]

See, I experimented with the Fasttrax on this car since my castor and camber were not affected with my front end work.
If I swung the tires more than 15 degrees the readings for caster would change.
Looks like I'm going to have to get or make some accurate slip plates with degree settings before I do a complete front end.
I can't just try and get "parallel to the body" and be comfortable with that.

 

[adriver]

There is a lot of good information that people have put in this thread.
I don't see a sticky on front end alignment.
Of course, there is the search.
This thread, with it's links, might be a a nice one for the next person who is thinking about starting to do their own alignments to see.
Then people could see it easily and add to it.
Someone besides me might request that of the mods.

 

[adriver]

And here’s one that’s very technical. Like hard to read technical. It actually works through deriving the equations for how the process for measuring castor works.

https://disco3.co.uk/gallery/albums/userpics/24543/steering-geometry-and-caster-measurement[1].pdf

What all that math gobbledegook means though is that the turn angle doesn’t matter as long as it’s symmetric, but a wider turn angle spreads your measuring errors over a wider range, so, more accurate.

For general knowledge:
I got as far as this and hit a mental wall with theory.
Does this mean that on a complete alignment that castor and camber are set with zero toe and then I have to reset the toe to what the factory calls for. (1/8 inch toe in)?
I hope not.
And while we are on it, does toe even have to be set before the others?

 

[67Dart273]

Let's say this was a major teardown. The way I do it is........

1....ride height and don't forget to "jounce" the car suspension

2...."rough in" camber, even if you just "plumb" the tires with a level, and then rough in toe as well

3....Go back and set caster/ camber which must pretty much be argued together.

4....Set toe "for real"

5....Recheck caster/ camber.

If possible, drive / move the car to settle the suspension and then recheck measurements. Of course the temptation to do a test drive at this point is IMPOSSIBLE to resist!!!

 

[fishy68]

I have the Fastrax setup and also found it would fall off the wheel real easy. After that happening 4 or 5 times I found a light weight bungee cord that was long enough to wrap completely around the tire and Fastrax setup to hold it in place. You don't want the bungee so tight it distorts the gauge. Just enough to hold it in place.

Since I could only afford 1 Fastrax I use the toe measurement method that Del said Crackedback uses except I used equal height 6x6's to support a piece of square aluminum tubing on each side resting against the tires to measure off of

 

[adriver]

I tried the four post string method this weekend just to see if I could compare and confirm the Fastrax toe reading.
Forget about that.
Even if you get the string all set, how are you supposed to get to the tie rods?
The string is in the way.
With I think I've figured out is the tie rods are pretty sensitive when you get down to 1/8 inch.
It took very little movement on the driver's tie rod to move 1/16 inch.
I mean very little.
Not even a 1/4 turn.
Test drive late this week.