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-   -   The Importance of Toe-in or Toe-out (http://www.focusfanatics.com/forum/showthread.php?t=143550)

Geezer 12-15-2007 03:58 PM

The Importance of Toe-in or Toe-out
 
There has been quite a few questions about alignment lately. Alignment is most affected when a car is lowered. The more it is lowered, the more impact occurs. In general, camber and toe are the main settings that are impacted. Since camber is discussed so frequently, we all pretty much know what it is and the problems it can cause. The impacts of toe (whether toe in or out) are not nearly discussed as much. You've heard me indicate many times that excessive camber combined with too much toe can be the death to tires. This remains true. But we rarely discuss the impacts of toe in or toe out so I'm going to give this issue a shot. I will do it as simple as possible and hope not to offend any engineers.

Toe-in is when both tires on the same axle (front or rear) point toward a line drawn through the axis (center) of the car. Toe-out is when the tires point away from the centerline of the car. The amount of toe measured is tenths of a degree or hundredths of an inch. It's minute measurements that have major impacts!! Zero toe means the tires are perfectly parallel to the centerline of the car. In a perfect world, with perfectly flat roads, and the ability to have rigid suspensions, zero toe on the front and rear would be the ideal. But because we have crowned roads and enjoy nice compliant rides (meaning movement in the suspension) zero toe would lead to a car that tends to wander (wants to roll off the road in the direction of slope). To correct this, toe adjustment was built into cars. Caster is also an integral component of directional stability but we'll save that for a later discussion.

A Focus and almost all front wheel drive cars have TOE-OUT in the front. This is reflected by "negative" numbers on the alignment specs (TOE-IN are the "positive" numerals). Why toe out on the front? Its simple physics. As the tires pull themselves forward (aka torque) they pull themselves into the desired toe-in position. In essence it's a self compensating. Once at a consistent speed the resulting front toe ends up being a tiny bit inward. Just enough to allow that directional stability that is needed. If the toe is set to far out it never gets to the proper amount of toe-in when the car is moving. What are the downsides besides bad handling....tire wear. Too much "toe-out" causes inside edge tire wear (toe-in causes the outside edges of the tire to wear). Combine it with camber and it only amplifies the problem. Another thing to consider, the alignment specs were determined using factory bushings. When you install harder bushings, the wheels may not be able to pull themselves fully back into the desired toe-in position. Watch yours tires carefully for wear after installing bushings and be prepared to reduce the amount of initial toe-out if wear is occurring.

The rear of the Focus is just the opposite. Since the rear wheels have no power to them and they are not able to pull themselves into the correct or needed toe-in angles, it must be set with some initial toe-in. The ever going debate is how much toe-in. While Ford provides some specs we have learned that the rear tires are very temperamental to too much toe especially when combined with a lot of rear camber (even if its within the allowable spec range). In simple terms, you want to reduce toe-in if you want to increase camber. My philosophy is to run the minimum allowable rear toe-in to avoid wear problems.

What about toe out in the rear? First, Ford specs don't allow it. This should only be used for autocross and the track and not the street. It will make the car react very quickly to any steering input. Stability is drastically affected and 100% driver concentration is required if rear toe-out is used. A sneeze can literally cause you to change lanes. If you intend to use it for motorsports events, use VERY small initial toe-out adjustments until you understand the full impacts of the adjustment. And please don't use the freeway for testing as these changes are amplified by speed.

starfuryt550 12-15-2007 04:09 PM

this is a good writeup, good job!!

toolnut7 12-15-2007 04:10 PM

I know ALOT about alignment and its effects, good and bad(years of trial error) Use to road race sportscars. This posting is great info and should be a "sticky" Thanks for the re-fresher course!

Rick

SVTF4243 12-16-2007 02:58 AM

Nice explantion of Toe in /out

Thanks

Pistonbroke 12-16-2007 12:06 PM

So the tow is always changing? with speed and different amounts of torque to the front wheels? If you're going down the road at 60 mph and you let off the gas then the front tow will go negative so the car will wander slightly?

illinipo 12-16-2007 12:54 PM

could we discuss the implications of running toe in at slightly less than the recommended spec?

I think it would be fine, a little more touchy handling-wise, but imo it can only help things with respect to tire wear. especially when you put a lot of weight in the car.

Geezer 12-16-2007 01:09 PM

Quote:

Originally Posted by Pistonbroke (Post 1883944)
So the tow is always changing? with speed and different amounts of torque to the front wheels? If you're going down the road at 60 mph and you let off the gas then the front tow will go negative so the car will wander slightly?


Theoretically yes. But remember, these are very very small changes and the condition of then suspension will be the determining factor. A car with sloppy bushings, tie rods, ball joints, etc would be far more noticeable than a new car. If you were to drive an identical model 2000 focus with 100+K miles vs a 2005 focus with 25K miles stock suspensions you'd notice different handling characteristics based on plain ol wear and tear.

Pistonbroke 12-16-2007 01:09 PM

Anybody know the toe specs? Also, is there any way to check toe yourself?

Geezer 12-16-2007 01:16 PM

Quote:

Originally Posted by Pistonbroke (Post 1883994)
Anybody know the toe specs?

For 2000 to 2005 front is -.07" to 0.00" the rear is 0.04 to 0.11

A recently posted alignment printout for a 2007 was -0.1 to 0.1 front and 0.08 to 0.28 rear as the specified range.

I'm not sure what the specs are for a 2006 falls or 2008.

Pistonbroke 12-16-2007 02:04 PM

Geezer, after I install the SVT spring and damper kit, how much will my toe change?


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