Checking toe-n and other DIY alignment issues

I have an '89 Cressida and I've been looking into DIY wheel alignment,
rather than tithe $80 to the local tire place and just for the enjoyment of
doing it.

It seems crucial that you have the ability to compare things to the
centerline of the vehicle, but the things I've seen are a bit vague on this.
For doing toe-in, for example, all the things I've seen talk about comparing
the difference between the the front and rear of the wheel/tire. Okay, but
how do you know which wheel is "right" to begin with? Let's say you see a
difference of .5" inches (strictly for illustration) either way between
front and rear. That could mean one wheel is exactly parallel to the
centerline of the car and the other is skewed. Or they could both be toed
in/out a bit. What do you use as your starting reference point, and how do
you get all 4 wheels lined up with this centerline and further allow for the
fact that the wheels are presumed to not be in perfect alignment to begin
with?

-How do you find the exact centerline of the car and mark a line parallel to
it?

-What about doing a car that has adjustable rear alignment such as this
Cressida?

What's a great, clearly explained, idiot-proof website or reference for
someone who wants to try this themselves without spending a fortune on tire
shop equipment?

Thanks for all input

"Doc" > wrote in message
link.net...
>I have an '89 Cressida and I've been looking into DIY wheel alignment,
> rather than tithe $80 to the local tire place and just for the enjoyment
> of
> doing it.
>
> It seems crucial that you have the ability to compare things to the
> centerline of the vehicle, but the things I've seen are a bit vague on
> this.
> For doing toe-in, for example, all the things I've seen talk about
> comparing
> the difference between the the front and rear of the wheel/tire. Okay, but
> how do you know which wheel is "right" to begin with? Let's say you see a
> difference of .5" inches (strictly for illustration) either way between
> front and rear. That could mean one wheel is exactly parallel to the
> centerline of the car and the other is skewed. Or they could both be toed
> in/out a bit. What do you use as your starting reference point, and how do
> you get all 4 wheels lined up with this centerline and further allow for
> the
> fact that the wheels are presumed to not be in perfect alignment to begin
> with?
>
> -How do you find the exact centerline of the car and mark a line parallel
> to
> it?
>
> -What about doing a car that has adjustable rear alignment such as this
> Cressida?
>
> What's a great, clearly explained, idiot-proof website or reference for
> someone who wants to try this themselves without spending a fortune on
> tire
> shop equipment?
>
> Thanks for all input
>

A proper wheel alignment on a modern vehicle involves all 4 wheels, which
pretty much requires a 4 wheel alignment machine. An alignment machine
finds the centerline of the vehicle by having a sensor head attached to each
wheel. You've probably seen the results of a DIY alignment when you see a
vehicle dog-walking down the road, where it looks like it is going down the
road at an angle.

The difficulty in performing an alignment with a toe gauge or a tape measure
is that making an adjustment on one axis can change another axis at the same
time. For example, adjusting camber will affect toe and vice versa, and it
is possible to have proper toe while at the same time having improper
caster. The Cressida has quite a bit of positive caster, and as you turn
the steering, you will notice that the camber on the front wheels changes
noticeably.

The other tricky part is due to wheel offset, where the physical centerline
of the wheel is not the same as the pivot point of the wheel when turned
left-right so you have to calculate the centerline of the wheel and the
centerline of the movement.

Finding the centerline of the car entails measuring diagonally in an "X"
from wheel centerline to wheel centerline and then measuring left-right and
front-rear.

I do most of the work on our vehicles myself, but I take them to a shop with
a 4 wheel alignment machine when it is time for an alignment.
--

Ray O
(correct punctuation to reply)

Ray O <rokigawaATtristarassociatesDOTcom> wrote in article
s.com>...
>
>
>
> A proper wheel alignment on a modern vehicle involves all 4 wheels, which

> pretty much requires a 4 wheel alignment machine.

Oval-track and road racers have been doing four-wheel alignments with
string lines for decades before the introduction of computerized,
four-wheel alignment machines.

Many - including me - still do!

We used to sometimes back IRS cars such as the Corvette onto two-wheel
projector-style alignment machines to do camber and toe. It was unnecessary
with magnetic guages and mechanical toe measurement.



> You've probably seen the results of a DIY alignment when you see a
> vehicle dog-walking down the road, where it looks like it is going down
the
> road at an angle.
>


More likely to be an alignment done by the $7.00-per-hour "Alignment
Expert" at the local discount parts store who used to be an "Expert Latte
Maker" at Starbucks last week - but was given a quickie course in how to
set up and read the machine.

The people working at PepBoys-type parts-and-service or discount tire
operations often don't have the understanding of complicated suspension
geometries, and simply move things around until the computer tells them
they are "close enough."

Computerized alignment equipment is sold to the shops NOT on its accuracy,
but on its ease of use, and the ability to train "....virtually anybody..."
to be taking alignment readings within an hour or so.

They won't have a clue as to what they're doing, but they WILL be taking
readings, and the computer WILL be telling them what to change, and they
WILL move things around until the computer says it's okay........

.........sorta' like the cashiers who give you $18.75 in change from a $10
bill for a $9.37 purchase because that's what the computerized register
said to give back for change.


> The difficulty in performing an alignment with a toe gauge or a tape
measure
> is that making an adjustment on one axis can change another axis at the
same
> time. For example, adjusting camber will affect toe and vice versa,

Adjusting camber CAN - most likely WILL - affect toe AND, possibly, caster,
but adjusting toe affects toe ONLY.

That's why it is done last.


> and it
> is possible to have proper toe while at the same time having improper
> caster.

It is possible to have virtually ANY combination of correct and/or
incorrect alignment settings......What's your point?



> The Cressida has quite a bit of positive caster, and as you turn
> the steering, you will notice that the camber on the front wheels changes

> noticeably.
>

The wheels tip when turning about the caster axis, but you are NOT actually
changing camber when you turn the wheels.

You are simply seeing the caster illustrated.


> The other tricky part is due to wheel offset, where the physical
centerline
> of the wheel is not the same as the pivot point of the wheel when turned
> left-right so you have to calculate the centerline of the wheel and the
> centerline of the movement.
>

Why?

Scrub radius is built into the suspension.

Changing the wheel offset changes the scrub radius.

You cannot correct scrub radius that has been altered by different wheel
offset except by going back to the original wheel offset.

You really don't want a "zero scrub" setup, because it would take away a
lot of the "road feel" from the steering.


> Finding the centerline of the car entails measuring diagonally in an "X"
> from wheel centerline to wheel centerline and then measuring left-right
and
> front-rear.

You have described how to find the centerPOINT of the car's suspension -
NOT the centerLINE.

The centerpoint "X" as described above also does NOT give you the thrust
line - off which various left/right angles are measured.

You need both centerline and thrust line data to determine various angles -
and to make sure the car doesn't "dog-walk" (your term) down the road.

Centerline is taken from front and rear tire track centerpoints - NOT an
"X" measurement - and thrust line is taken from the orientation of the rear
wheels.


>
> I do most of the work on our vehicles myself, but I take them to a shop
with
> a 4 wheel alignment machine when it is time for an alignment.
>

Smart man!

"*" > wrote in message
news:01c6f239$ce0f3a80$af98c3d8@race...
>
>
> Ray O <rokigawaATtristarassociatesDOTcom> wrote in article
> s.com>...
>>
>>
>>
>> A proper wheel alignment on a modern vehicle involves all 4 wheels, which
>
>> pretty much requires a 4 wheel alignment machine.
>
> Oval-track and road racers have been doing four-wheel alignments with
> string lines for decades before the introduction of computerized,
> four-wheel alignment machines.
>
> Many - including me - still do!
>
> We used to sometimes back IRS cars such as the Corvette onto two-wheel
> projector-style alignment machines to do camber and toe. It was
> unnecessary
> with magnetic guages and mechanical toe measurement.
>

Very true, but the folks doing alignments with string lines are much more
knowledgeable about alignments than your average DIY-er.


>
>> You've probably seen the results of a DIY alignment when you see a
>> vehicle dog-walking down the road, where it looks like it is going down
> the
>> road at an angle.
>>
>
>
> More likely to be an alignment done by the $7.00-per-hour "Alignment
> Expert" at the local discount parts store who used to be an "Expert Latte
> Maker" at Starbucks last week - but was given a quickie course in how to
> set up and read the machine.
>
> The people working at PepBoys-type parts-and-service or discount tire
> operations often don't have the understanding of complicated suspension
> geometries, and simply move things around until the computer tells them
> they are "close enough."
>
> Computerized alignment equipment is sold to the shops NOT on its accuracy,
> but on its ease of use, and the ability to train "....virtually
> anybody..."
> to be taking alignment readings within an hour or so.
>
> They won't have a clue as to what they're doing, but they WILL be taking
> readings, and the computer WILL be telling them what to change, and they
> WILL move things around until the computer says it's okay........
>
> ........sorta' like the cashiers who give you $18.75 in change from a $10
> bill for a $9.37 purchase because that's what the computerized register
> said to give back for change.
>

No argument from me there!

>
>> The difficulty in performing an alignment with a toe gauge or a tape
> measure
>> is that making an adjustment on one axis can change another axis at the
> same
>> time. For example, adjusting camber will affect toe and vice versa,
>
> Adjusting camber CAN - most likely WILL - affect toe AND, possibly,
> caster,
> but adjusting toe affects toe ONLY.
>
> That's why it is done last.
>
>
>> and it
>> is possible to have proper toe while at the same time having improper
>> caster.
>
> It is possible to have virtually ANY combination of correct and/or
> incorrect alignment settings......What's your point?
>

The point is that one should know the cause and effect of each change in
setting to avoid unsatisfactory results.

>
>> The Cressida has quite a bit of positive caster, and as you turn
>> the steering, you will notice that the camber on the front wheels changes
>
>> noticeably.
>>
>
> The wheels tip when turning about the caster axis, but you are NOT
> actually
> changing camber when you turn the wheels.
>
> You are simply seeing the caster illustrated.

Yup, poor choice of words on my part.

>
>
>> The other tricky part is due to wheel offset, where the physical
> centerline
>> of the wheel is not the same as the pivot point of the wheel when turned
>> left-right so you have to calculate the centerline of the wheel and the
>> centerline of the movement.
>>
>
> Why?
>
> Scrub radius is built into the suspension.
>
> Changing the wheel offset changes the scrub radius.
>
> You cannot correct scrub radius that has been altered by different wheel
> offset except by going back to the original wheel offset.
>
> You really don't want a "zero scrub" setup, because it would take away a
> lot of the "road feel" from the steering.
>
>
>> Finding the centerline of the car entails measuring diagonally in an "X"
>> from wheel centerline to wheel centerline and then measuring left-right
> and
>> front-rear.
>
> You have described how to find the centerPOINT of the car's suspension -
> NOT the centerLINE.
>
> The centerpoint "X" as described above also does NOT give you the thrust
> line - off which various left/right angles are measured.
>
> You need both centerline and thrust line data to determine various
> angles -
> and to make sure the car doesn't "dog-walk" (your term) down the road.
>
> Centerline is taken from front and rear tire track centerpoints - NOT an
> "X" measurement - and thrust line is taken from the orientation of the
> rear
> wheels.
>
>
>>
>> I do most of the work on our vehicles myself, but I take them to a shop
> with
>> a 4 wheel alignment machine when it is time for an alignment.
>>
>
> Smart man!
>

I know what I don't know...
--

Ray O
(correct punctuation to reply)

Ray O <rokigawaATtristarassociatesDOTcom> wrote in article
.com>...
>

>
> I know what I don't know...
>

If only some of the others who post here could be as aware......

Didn't mean to sound argumentive - just correcting what I saw as technical
errors in your original post.

Your response suggests you understood that.

Thank you!

* wrote:
> If only some of the others who post here could be as aware......
>
> Didn't mean to sound argumentive - just correcting what I saw as technical
> errors in your original post.
>
> Your response suggests you understood that.
>
> Thank you!

I think Ray was only suggesting that its not an area you want to get
into in a DIY fashion without deep knowledge of the subject, not that
it wasnt possible to do any other way.

Its the only thing I trust someone else to do on my car, and even then
i watch them like a hawk to learn and check they have more knowledge of
what they are doing than me! If they know no more than me I'd worry!

"*" > wrote in message
news:01c6f2b3$695b59a0$6197c3d8@race...
>
>
> Ray O <rokigawaATtristarassociatesDOTcom> wrote in article
> .com>...
>>
>
>>
>> I know what I don't know...
>>
>
> If only some of the others who post here could be as aware......
>
> Didn't mean to sound argumentive - just correcting what I saw as technical
> errors in your original post.
>
> Your response suggests you understood that.
>
> Thank you!
>
>
As coyoteboy mentioned, my point was that doing an alignment with a
measuring tape and strings is not something that a do-it-yourselfer is
likely to have success with and was not meant to be instructional on how to
do an alignment.

I have no problem when people catch my errors and correct them because that
is one of the ways I learn or am reminded of stuff I've learned in the past
and have forgotten.

OTOH, I do have a problem when people who don't know what they're talking
about argue with the facts!

Thanks,
--

Ray O
(correct punctuation to reply)