Most alignment shop have no clue as to what bump/roll steer
is, the difference is pleasurable driving or unpredictable
I use Dunlap toe and caster, camber and King pin inclination
gauges and Longacre corner weight scales.
In addition use various straight edges, string line and a level.
Current prices on this equipment is probably enough to buy a good used car.
So now lets do this the po-man way, and very precise also.
Wright every thing down as you go.
using rim diameter convert any Degree specifications to inches.
Settings should be listed at rim diameter.
Level the floor where the tires will sit, plywood, magazines
what ever. aim for 1/32-1/16 side to side, closer the better.
I aim for dead on.
O.D. the tires stretch the smaller tires with over pressure
and put in hot sun for awhile, after cooling bleed down to normal and check O.D. again.
Circumference measure will do.
roll while bouncing onto leveled floor.
Will steering lock tight in straight ahead position?
Need to lock in center of rack travel so that inner tie rod
ball are in same place on each side.
If not locking there is best to slide rack boots out of the way and make
rack stops front cut in 1/2 length ways tubing or pipe.
When they both are same length and snug fit between rack housing
and what ever is at the end of rack(backside of ball socket housing.)
Put someone in drivers set and see if car is level, assuming 90% of your driving is
by you self.
If close, good enough as probably no corner weight scale available.
Run sting front a cinder block placed about 10ft in front of bumper, just outside the
out edge of wheels by 2-6inches and high enough to be at height of axle.
pull string to back of car and around body,bumper or something about same height as axle
and then around car back to front to another cinder block like the 1st side, Now space
string at back from body, rear tires//////something with 2x4 or something to parallel string.
when done you should have parallel strings with equal spacing spacing side to side to the front axle wheel nut dust cover or rim to string.
Now measure toe, dial caliper is best tape measure just as good but slower.
Measure to rim at front of rim(front of car end) and then same at the rear.
The difference is the to measure.
Toe is a total measurement so 1/2 of the stated per side is the normal.
Get close for now.
Check camber with a level held vertical level with bottom of level against rim then measure
from level to rim at top of rim. + camber= gap at top.
Do the other side
Get this close for now---all settings affect all others!!!!!
now unlock rack and turn steering wheel left(hold brake tight so car has lees chance of sliding)
until tire is Xdeg from straight.
Will have to look up the degrees if needed, but not tonight! I think its 22deg.
now measure angle same as on camber.
Do same to other side with wheel turned right.
Turn wheel back straight and locked.
sit down and look at your numbers.
More caster adds camber, more camber lessens caster.
more positive(top in) of either setting causes toe out, less of either add toe in.
Decide what will be the best to move to get caster camber correct.
Check toe and adjust as adjustments are made and keep toe corrected.
RACK is locked, right?
When every thing is correctly set we can make it drive good, real good.
using floor jack pick car up 3-4 inches( tires still having weight on floor)
Check the toe.
If any change in toe measurement, and this is a new set of measurements as track narrows as car is lifted,
Adjust out with caster.
If tie rod connects in front of axle center more caster will cause more change towards toe in, this would be if
rim toes out when car is lifted ( or is that backward, I have to re learn about 1/2 the time.)
Do not worry about caster being dead on 4-5deg to speck is close enough. Steering will be slightly heaver with more caster andslightly less with less and does not have to match side to side unless it pull under braking.
Zero bump steer defines the desired caster setting.
Correct camber, toe and chase your settings in ever smaller circle of adjustment until every thing is correct.
We have actually used Droop to check bump. Zero one way = zero the other way.
Flip your string line around and now do the rear setting.
You get all this right and you have a very well behaved car that goes where you point it in turns,
within the limits of the design.
There, I Think I got it right
You should be able to fill in any blanks I left in the above. Might even find a mistake or 2!
What if rear end is adjustable yet out of alignment?What if you need to change out cams? Slot strut holes? Slot struts and install cam kits there? Offset upper bushings for the Ford trucks.You also will need to know what the manufacture recommends for the 3 basic settings.Every car make is different.For the money vrs time and parts take it to local shop and ask them to give you print out of your car after they adjust it so you can see before and after. Even checking for worn parts done wrong wont reveal them, checking upper/lower ball joints need to have A-arms loaded/unloaded(early Mustangs can fool ya)Whatever you do, if you take it to a dealer, "in spec" can still wear out tires as specs can be quite large!Oh, its always good to throw about .3-.5 more caster in right side if you drive on roads with a high crown...
Bottom line, Wheel aligments done right is no waste of money.
Last edited by fh64_lucky; Jan 28, 2013 at 11:01 PM.
Yes, always start with factory specks.
[3-.5 more caster in right side if you drive on roads with a high crown...] Thats backwards. more caster is more self centering. the right wheel trying to center in the toe in will be to the right.
[3-.5 more caster in right side if you drive on roads with a high crown...]
excepting it'll pull left in left lane. I try to split the difference=same side to side.
If offset bushings, ride height change or any thing that changes geometry;
Tire temps at inner, center ,outer tread is best way to fine tune pressure
and camber. 10-15 degrees hotter on inside than outside for camber.
Tire pressure is center of tire, between inner and outer temps.
Good tire pyrometer is best with a needle probe to penetrate 1/8th inch or so into tread.
An infrared temp gun is a far behind 2nd but useful.
Temps should be taken immediately after hard driving as temps stabilize across tires rapidly. Sometimes I will do one tire per stop.
Inner vs out vs center long term wear is the bottom line for finding proper setting
for a given set up. This assuming camber gain curve is correct.
On some cars where the camber curve is defective due to design good cornering comes from using excessive static + camber. Tire wear suffers, lap times drop. This is mainly in designs where the strut replaces upper link.
This would be rare to find on modern unequal length A arm designs.
The Chapman( Lotus) strut design is sort of in between.
The Miata unequal length A arms is good on tires.
The MR2 with only lower A arm and strut upper link needs extra camber
to reach full potential at the expense of tire wear. The car is quicker and better behaved than the Miata, Lotus Elan. the MR2 with all its suspension draw backs
is the best driving, cornering street sports car I have ever driven.
Reversed A arm lower, camber link upper and upper and lower trailing links
( trail the chassis) I basically all around best. More expense. Formula/CanAm
Now that you see how long it will take to do yourself properly(post#48)
Bet you will spend the $80
Then you can fine tune it from there.
toe out works fine and makes the car turn in quicker on Anti Ackerman steering
as long as no darting under the brakes. this due to bushing flex/give.
Ackerman with zero toe lets the car leave the corner with less rolling resistance.
Drivers love it. lap times drop, tire life increases.
IRS-always toe in.
Never run toe out, unless the driver is the right one for it. The car will turn
free or less tire scrub/drag, Over steer can get real sneaky.
If we go deeper into this:
The definition of slip angle is the difference between where the rim is pointed and the direction the tire tread is pointed. They are never the same unless tire is solid rubber!
The rear always has a greater slip angle than front so the car can turn properly.
This is why the side wall on rear is usually taller than front.(aspect ratio)
My post are what it takes to make Formula and other high performance cars work.
Your pick up truck can benefit from same except with equal slip angles even sometimes more slip front than rear.....Well it's a Truck
called a shop that I use near my house and he wanted $89 to align my car , I started asking questions as to how they go about doing the alignment & he slips and tells me they take my car to Firestone I gave Firestone call and they want $65 for a one time alignment and will have it done in under an hour. I hope they dont try and kick me out of the garage while they do it. haha
The two guys you have in your avatar have more brains then the employees at those two places.
I have always worked at places that pushed you to upsell, its a business. One thing is true though, I dont ever go against my upbringing and sell someone something they dont need. I am not a fan of too frequent fluid flushes etc, just follow the manual. Having said that, alignments are critical to tire life. I see HUNDREDS of cars with chewed up tires, and try to sell a customer an alignment, and they dont buy it, then a car rolls in with pristine wearing tires and the customer wants one up front. So, its a question of how good do you want to take care of your vehicle. If you just had it checked, havent hit anything substantial, and know your suspension parts arent worn, dont buy into the upsell, but if you dont know, have it checked. Ask to walk back with the tech, and have him show you the looseness, worn parts, split boots,etc. If the guy is honest, he WONT, have a problem with showing, you. If you are troubled,seek a second opinion.
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