Tuesday, October 16, 2012

Wheel Alignment Notes - TBC

My Setup
I have a strange setup where I wanted more rubber on the ground and a wider track. So i ended up with some 0 offset rims @_@
I didn't imagine it would be so hard to fit. But they were.
This lead me on the hunt to finally setup my suspension. I started out with maximum camber on the fronts which was -4degrees
I have now modified my fender to accommodate the big rims, i could dial the camber back a little if i want to. Over fenders DIY see here


Front were easy due to the Blitz camber tops.  Don't know how i survived before. The came the rear camber and toe issues. In went new custom shims see here (I have now corrected my alignment. It took three shots @_@ so not cheap!)


Due to my excessive camber i want to zero my toe both front and rear. If i was running less camber i could go minor toe out on the front. I did my best at trying to zero the rears. I could go back again, but I am lazy haha.

Previous wheel alignment stuff see here
And another attempt here




------------

Alignment
Primary alignment should be conducted with the strings method.

After adjustments and quick checks cnn be done with toe plates.

Explaining toe/camber/castor - http://www.lancerevoclub.org/faq/handling.php
Note that toe in is postive toe?
 Because the toe formula is: b - a where b = distance between rear wheel lip and a = distance between front wheel lip

------------

DiY Alignment -
http://www.negative-camber.org/jam149/technical/alignment.html
http://www.hondatuningmagazine.com/tech/htup_1006_honda_civic_si/viewall.html

------------

Technical Info
https://www.pegasusautoracing.com/advcat.asp?CategoryID=TECH

------------

Toe Plates
Instructions for Longacre #79500 Toe Plates
This is a fast way to check / set front end toe. It is affected by wheel or tire runout. Be certain wheels run true and tires have no bulges.

Turn wheels to straight ahead: Should be done on level ground. Set caster & camber first.
Lean plates up against wheels: Folded lip goes to the outside. Be sure the entire plate is up against the wheel.
Measure front width, then rear: Use the slots for the tape measure. Subtract one from the other for toe. Larger front width means toe-out.

------------

Toe mm to degrees
http://honda-tech.com/showthread.php?t=1546693

The important things to keep in mind about this graphic are:
1. A is the angle per side, which is what the OP asked for.
2. T is the total toe. If you're using toe plates, you're measuring the total toe. If you're using strings, then you're measuring the toe per side, which is half of the total toe, so replace (T/2) with t (the toe per side).
3. Dt is the distance between the measurements. If you measure at the wheel, then it's the diameter of the wheel; if you measure at the tread, then it's the diameter of the tire; if you use toe plates, then it's the width of the toe plates.
4. arcsin means inverse sine.

As an example, I use toe plates that are 24 inches wide. My total toe is 1/8 inch. Plug these measurements into the formula and you get:
A = arcsin((0.125 / 2) / 24) = 0.15 degrees.

OR


Converting toe from mm to degrees:
Measure the rim diameter in mm as the size e.g. 17" is not the actual diameter your measurements are based on.
Multiply the result by PI to get the circumference.
Divide the result by 360 to get mm per degree.
Divide the toe mm by the mm/degree result to get toe in decimal degrees

Or Excel =DEGREES( ASIN( TOE_IN_MM / ( RIM_DIA_INCHES * 25.4 )))


------------

4 Wheel Alignment with Strings Method
http://forums.nasioc.com/forums/showthread.php?t=1093484&highlight=string+alignment

------------

More on Toe
http://www.bakerprecision.com/longacr16a.htm

------------

Going Light Weighthttp://www.motoiq.com/
The obvious way to make up for the disadvantages of increased wheel diameter and width is to use a light wheel. Light wheels are easier to accelerate and brake. They also reduce unsprung weight. Ever wonder why so many MotoIQ project cars run Volk wheels? Most Volks are forged. The forging process improves the grain structure and work hardens the metal (engineering terms for making it stronger!) It provides a superior strength-to-weight ratio. We like Enkei’s competition series wheels as well which have MAT formed rim sections. MAT helps improve the metal's mechanical properties much like forging for a fraction of the cost. Lower cost wheels are usually cast. The casting is a cheapest way to make wheels and nearly all low-priced wheels are cast aluminum.

http://www.willtheyfit.com/ ----------------------->

------------
The Ultimate Guide to Suspension Handling - Drift Setup
Note applicable to our FWD cars but it is a good read.

http://www.motoiq.com/tech/the_ultimate_guide_to_suspension_handling.aspx

Notes from Mike Kojima:
Camber - Front Wheels - 3-4 degrees negative camber helps put the tread flat on the ground when under side load.

Dialing in negative camber helps combat tread lift and roll related wheel tilt.  Camber thrust is also generated. The trick is to add just enough negative camber so the tread stays flat and 100 percent engaged with the ground under side load and roll while maximizing the camber thrust effect. Adding too much negative camber will hurt more than it helps. Too much negative camber will:

• Reduce braking traction.
• Reduce acceleration traction if it’s applied on the drive wheels.
• Increase the tendency to tramline (following cracks and grooves in the pavement)
• Increase crown sensitivity (wandering caused by road contour).
• Affect tire wear; the insides of the tire tread will wear faster with more negative camber if you don’t corner hard.  Conversely, if you constantly corner hard, your tires will wear more evenly and last longer

http://www.motoiq.com/magazine_articles/articletype/articleview/articleid/1781/the-ultimate-guide-to-suspension-and-handling-part-five-adding-negative-camber.aspx

Toe - For drifting you want to run a slight amount of toe out in most cases, usually around 1/8" to 1/4" toe out.  More than this will make the car twitchy and respond oddly to steering input.  Front Toe out helps the car turn in and initiate better.

Toe - General Tips and FWD
FWD cars like Dez Ballard's Mini can almost always benefit from some amount of toe out.  The only potential drawback is accelerated tire wear.  On a really high powered FWD car too much toe out can cause a lot of torque steer.

Front toe out is a useful tool that can really help a car when used in moderation.  Many cars and situations can be helped with a little toe out.  Generaly front toe out speeds steering response and reduces understeer in the first quarter to third of a turn.

Driving Use the-ultimate-guide-to-suspension-and-handling-part-seven--tuning-your-toe
...........................FWD/ AWD.............RWD....................FWD/AWD............RWD
1) Aggressive Street Driver
..............................Front 0..............Front 0-1/16” in.............Rear 0.............Rear 1/8” in

2) Weekend Hot Lapper
..........................Front 0-1/8” out.....Front 0-1/8” out........Rear 0-1/8” out....Rear 1/8” in

3) Racer Only/Serious Autocross/Serious Drifter
..........................Front 1/8-1/4” out..Front 0 to ¼” out......Rear 0-1/4” out....Rear 0-1/4” in

e.g.
First 1" = 25.4 mm
so 1/8" = 3.2mm.

You want 1/8" toe out total, that's 1/16" per side. (~1.6mm per side)

Rear toe out has limited use.  One of the times it sometimes works is on a FWD car being used for stock class in autocross.  It can help the car rotate in tight low speed turns where it would normally get grinding understeer and you are not allowed to do anything else in the way of mods to fix the issue.  Sometimes it can work surprisingly well.  It can make the car tricky to drive at high speeds so caution must be used.
Rear Toe Out

Rear toe out is not a very useful setting.  It hurts in almost all cases except for helping rotation on a FWD car when you are completely out of tuning options.  We have only used this successfully for Stock Class Autocross and Rally in FWD cars.


Rear toe - Just Right
- Helps the car rotate in mid turn and get away from overloading the front tires with understeer.  Generally this is a FWD only trick usually for stock autocross classes or rally.
- Generally you would not ever want to do this unless you had no other tuning option.

Rear toe - Too Much
- Causes sudden onset of oversteer on throttle in RWD applications.  Causes violent oversteer all the time on anything other than a FWD car. Car feels unstable.
- Makes a car rotate violently when the throttle is lifted or when the car is trail braked into a turn.  Generally not good.

Just like the colt B14 and B15 Nissan Sentras have beam rear axles.  The axle has a lot of rear toe in from the factory which makes the handling twitchy at the limit.  The rear beam axle must be bent to remove the toe in.



Caster - You want to run as much positive caster as you can get without hitting the fenders.  Typically this is around 7 degrees or so on most cars. Caster really helps a drift car by making it self-steer better.  When you start to drift, you can simply let go of the wheel and let if feed through your fingers and the car will counter faster than if you were steering it yourself.  Caster also gives you more negative camber as the wheel turns which helps front grip.  More caster helps the car turn in better and makes the car more stable as well.  You probably don’t want to exceed 9 degrees of positive caster as this can actually cause understeer due to weight jacking as well as contribute to bump steer.


3 comments:

  1. This comment has been removed by a blog administrator.

    ReplyDelete
  2. I like your post.Very impressive way of writing....appreciate the great information about wheel alignments. many thanks for sharing...

    ReplyDelete