|11-22-2007 05:24 PM|
This is written by a very competent race mechanic and engineer. Its one of the more simpler explanations I could find. You'll come to the that max front and rear toe out is not good for anything except tire wear and a squirrelly handling car.
Pigeons vs. Ducks (or what's just ducky for the front is for the birds in the back)
The toe of a tire, or how the front sits in relation to the rear is one of those adjustments where a little really goes a long way. Toe can drastically alter whether a car has understeer or oversteer--a lot more effect than any other adjustment. Toe can also drastically effect the wear patterns on your tires, especially the rear ones.
If you like having tires that are sticky and still want them to last more than a few thousand miles, only minor adjustments should be done to the toe. But with all that is at risk, why is toe in or toe out desirable at all? Because it allows the other changes you are going to make have a greater effect on the cars handling. With negative camber, the contact patch's shape has been altered ever so slightly. Tossing in a bit of toe will help correct this.
In the rear, toe out is bad, it won't help the car any, even to understeer. The only thing that will become apparent is that it really causes the tires to scrub.
Toe in on the rears on the other hand is quite nice in moderation. It can help offset a number of things, primarily the tendency of heavy rear swaybars to induce oversteer (see section 4 in tips from the garage). somewhere between 1/16" and 1/8" total toe in for the rears is a good number. I say somewhere because some shops can't measure toe with such a degree of accuracy, or they don't use inches (although if they have a computerized alignment rack, they should be able to measure things in darn near any unit, even leagues)
The front wheels actually like a bit of toe out, about the same measurements. This helps to counteract the effects of all that positive caster.
If you decide that tire life should not be sacrificed for magnificent handling, then setting toe fore and aft to zero is a good safe route to go.
|11-20-2007 11:02 AM|
Well the thing is my front toe is already at .02 degrees both sides... So theyre not compensating for anything...
I plan to go down to .1 deg in the rear. Reason for it being so low is both autocrossing and because I often carry a lot of weight in the car, and when the springs compress the tires toe in thusly giving me REALLY CRAPPY tire wear on long trips with a lot of gear...
Thanks for the comments, if I cant find a rear only job for 30 bucks then I will do all four for 60
|11-20-2007 04:46 AM|
rear toe is slightly...
You each rear wheel independantly to the car. So 1 rear wheel can be perfectly aligned, the other wheel could have either toe-in or toe out.
The slight toe-in/out would cause a slight dog-tracking action... which may or not be noticable. The front end alignment could then be set up to compensate for the rear misalignment.
Now someone comes along at sets the rear alignment so that both wheels are the same (in/out/neutral). Now your rear is good, but the front is wrong because it was compensating for the bad rear alignment.....
|11-19-2007 07:29 PM|
Rear toe doesn't affect the steering mechanically (mechanicals?). Rear toe can make the steering more responsive but that's because the wheels are adjusted to point inwards or outwards. Lots of outward toe can make things happen really quick. Autocrossers tend to favor a little toe out but it all depends on the front toe specs as well. The centering or position of the steering wheel is adjusted by the front tie rods (front toe adjustment). A low tire on one side or another or a collapsed spring (rare but possible) could affect the steering wheel position but I've never heard of rear toe being able to do it by itself. I guess if they screw up the thrust angle alignment (so the rear is not tracking the front aka crabbing) then yes you might have to compensate with the steering wheel but that would be the technicians fault and hard to do on a computerized alignment rack.
Its always best to get a four wheel alignment. It rarely costs any more and its important that those rear wheels follow the fronts as perfectly as possible.
|11-19-2007 07:19 PM|
|SkaAddict||There's probably a grain of truth in what he's saying...I can imagine that any change done to the rear would also require a change up front to compensate for it. Now as far as do you actually need a four-wheel alignment...I couldn't say.|
|11-19-2007 07:01 PM|
okay guys, brain teaser. Sorry to bump and old thread, but WD and Weeasp are both subscribed here...
Joe Somebody at the alignment shop told me something verrry interesting today. Apparently, when you change the REAR toe, the steering wheel goes crooked. Is this true? I only need a rear alignment to get the toe down a bit, which would save me like 30 bucks, but according to this guy thats not possible cuz it will screw up the front and I will need a 4-wheel.
What is possible is that they think I dont know anything about alignments and are fishing in my wallet...
|10-31-2007 01:25 PM|
I can set up the strings, and do 2 complete measure/adjust-measure/adjust settings in well under an hour.
I did have the pleasure of borrowing one of these:
Worked great, but the setup time took longer than it takes me to pull out a 24" level, 1/32" graduated scale, and a calculator.
Thanks for the mega write-up WeeAsp!
There's a few variations on a theme so to speak as far as how I perform my own alignments,
but the majority of what's written will get the job done and then some.
|10-31-2007 12:59 PM|
|Geezer||The method that WeeAsp posted is old school. While there are still people who do that, they are few and far between. The gauges/kits mentioned eliminate the painful calculations (a little math still has to be done for toe settings but that's it). The kits are really good for autocrossers and road racers who what to make quick accurate adjustments at the track. For the guy who does one alignment a year, they don't make much sense economically.|
|10-31-2007 08:42 AM|
|DFv2||And so we realize that the $85 bucks is TOTALLY worth not having to align your own wheels.|
|10-31-2007 08:37 AM|
|pat247||WeeAsp, you made my head hurt.|
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