Toe in and Toe out

[zildjiank]

Ok, so I'm in need of some understanding...what is toe in and toe out? And what does that do for the car, and when do you do it and how do you do it? Will I need to do it, or is it an aftermarket part that is just adjusted specially for it? Thanks guys...

[sde]

hokee pokee?

[Guest *Jedimaster*]

hokee pokee?

[TSiWRX]

Search for "toe" by using the "Advanced Serch" feature, and cross-reference Xenonk as the post author, you'll get good hits as to what different suspension adjustment/settings does to the car's handling. He's made several very, very recent (as in within the last day) posts about this issue.

 

As for a basic reference:

 

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=4

 

[AWDpower]

Toe refers to how the tires are pointed in relation to each other. Toe in means the front of the tires are pointed towards each other, so they want to push toward the center of the car as you drive. Toe out means they are aimed away from each other, and pull out to the sides as you drive. Generally speaking, toe in increases stability, or the cars tendency to go strait. Toe out makes that end of the car more willing to rotate and change direction. Cars usually come from the factory with minimal toe, and are tuned to err on the side of stability. Increasing toe can drasticly increase tire wear. For most driving, the factory settings are fine. At a tight autocross, more toe out can help the car turn in. But the car would also be less stable at higher speeds. Many cars have a flexible link in the rear suspension to increase toe in at the rear of the car during cornering and braking, to make the car more stable.

 

Jason K.

[bcbaohio]

Toe refers to how the tires are pointed in relation to each other. Toe in means the front of the tires are pointed towards each other, so they want to push toward the center of the car as you drive. Toe out means they are aimed away from each other, and pull out to the sides as you drive. Generally speaking, toe in increases stability, or the cars tendency to go strait. Toe out makes that end of the car more willing to rotate and change direction. Cars usually come from the factory with minimal toe, and are tuned to err on the side of stability. Increasing toe can drasticly increase tire wear. For most driving, the factory settings are fine. At a tight autocross, more toe out can help the car turn in. But the car would also be less stable at higher speeds. Many cars have a flexible link in the rear suspension to increase toe in at the rear of the car during cornering and braking, to make the car more stable.

 

Jason K.

 

Extremely well put - zildjiank the key is that you don't do it - this is something that is thrown out of whack when you hit a massive pothole. It takes an experienced mechanic to fix the "toe" on an alignment machine (if they are really good they can do it with a long, straight breaker bar and some string - when I managed a Goodyear shop, I had a guy that could do it more accurately than the machine). Other alignment/front end chassis characteristics include camber and caster, which also indicate wheel position relative the the road suface. Here is a good crash course with diagrams:

 

http://www.familycar.com/alignment.htm

[zildjiank]

Search for "toe" by using the "Advanced Serch" feature, and cross-reference Xenonk as the post author, you'll get good hits as to what different suspension adjustment/settings does to the car's handling. He's made several very, very recent (as in within the last day) posts about this issue.

 

As for a basic reference:

 

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=4

 

 

Thanks, I know he did, but he also told me to post a thread to talk about it...

[Xenonk]

moved to suspension forums

[Xenonk]

Actually, front and rear tires can do two different things when you talk about toe adjustments.

 

Here's an example:most autocrossers will set up toe-out for the front and toe-in for the rear to really just have the car doing "easy donuts" when the throttle is on.

 

It is said that the rear toe can really make the car perform since it's the trailing axle, the steering axle can change directions unlike the rear. Another note to notice is that toe-out in the rain for the front can promote understeer (since it the tires are trying to go two different directions while toe-in is converging to the centline, turning the front of the car into a pivot point when you hit the brakes and the front end of the car will dig into that imaginary pivot point where the car can loop itself (spin out) at that point. I have yet to finish studying the affects of rear toe adjustments on a Turbo AWD car in the rain personally, but I am reading up on as we speak.

 

Excessive toe in any direction can increase tire wear.

 

Toe alignments can change dynamically while driving (toe-out happens a little bit under acceleration, and toe-in for braking.. all of this is coming from the flexing of the chassis and control arms).

 

To adjust toe, usually there are or combination of:

tie-rods

camber plates (depending on the kingpin axis)

lateral links

eccentric bolts

and many others that I havent seen yet.

 

Toe adjustments should be done by an alignment shop.. if your home-made measurements or even eye-balling the wheel to "make it look straight" based on a bent fender (or frame for the worse case), you will end up screwing yourself over in the process making the adjustments. Being off by 1/16" of an inch can be drastic (since the real math is degrees or radians because of different tire diameters and wheel sizes that you are using to make your adjustments with). Damn Trig and Geometry

 

 

Keefe

[TSiWRX]

Thanks, I know he did, but he also told me to post a thread to talk about it...

 

Doh!

 

Sorry 'bout that - I just read the other thread, and indeed!

[zildjiank]

Thanks keefe and all

[starlabs]

Very informative!

 

+1!

[AWDpower]

 

Here's an example:most autocrossers will set up toe-out for the front and toe-in for the rear to really just have the car doing "easy donuts" when the throttle is on.

 

 

 

Are you sure about the rear toe? I thought toe in increased stability, the rear wants to follow the front. Toe out makes the rear want to track out and swing wide of the front. Under hard cornering, the outside rear wheel has most of the load (all on some cars) and has the most influence. In that case, the angle of the outside wheel acts like rear steering. So toe in keeps the rear in line, toe out would swing it wide. I've got a car that demonstrates this to a fault. My Galant VR4 came with a crappy version of rear wheel steering. Basicly it has a hydralic steering rack connected to the rear trailing arms, and it forces the wheels to turn in phase with the fronts by up to a degree and a half. Under hard cornering, it basicly acts as an active toe control on the outside wheel. The problem is that it only works above 30mph. When going through a sweeping corner at the limit, above 30mph, extra toe in is added in the rear. When the speed drops, the toe out goes way and the rear comes around hard. It does the opposite when accelerating through a sweeper, suddenly increasing understeer. I've removed the rear rack, but it was a good lesson in the effects of rear toe.

 

I could be wrong, but that is definitly how differences in rear toe felt to me. I also have heard that rear toe changes have a bigger impact on the car then the front. Another car that is interesting when it comes to rear toe is the first MR2 turbos. The early cars I believe had "problems" with too much rear toe, and were described by some as evil, or fun by others. Toyota made changes to the rear suspension to fix the problem since too many people were backing them off the road. I don't know the details on that though.

 

Jason K.

[Xenonk]

Yes, I am sure of my statement.. this allows you to be on the gas way earlier out of the corner. This is definitely true when it comes to RWD based cars as they are pushing their way through.. remember, you can point your car however you see fit with the front wheels.. And remember my other statement about dynamic changes in the toe measurements when the car is under braking and acceleration, the rears will flex a bit as well in this process.

 

4WS is just that.. what you are describing of your "toe-out:loose, toe-in:stable" is describing a steerable axle.. when you have a fixed axle, these things are different as you are speaking of.. and yes, your example is true to the sense of what you are saying because you are basically running 2 steering axles that actually change more dramatically than a typical fixed rear axle alignment.

 

And you are correct, the rear has a greater impact on the car than the front. Reason being is that you are shooting and pivoting the car using the rear.. just imagine if all cars were rear-steering axles.. you know how twitchy the car can get?

 

Bobby Ore's stunt driving school does have a few of these cars at hand to teach people how to control a drift.. the reason being is that the front end of the car becomes a pivoting point.. and when you add load weight in a steering situation, the outside wheel on the rear will be the dominating factor to shoot the car in the cross-corner direction.. and when you add the rear-wheel-steering theory to the mix, you'll see what I mean.

 

Too much rear toe-in can really throw the car in a crazy loop when the car is given at some higher speeds.. you have to think of the dynamics of the car as well in the process when the car transfer forces and weights from one end of the car to the other.

 

 

Keefe

[AWDpower]

I'm sorry, I'm having trouble picturing what you are saying. I keep thinking that if a car is cornering hard, most of the weight will be transfered to the outside wheels. With toe in, the rear outside wheel is turned toward the inside of the turn, and the rear should want to stay toward the inside. With toe out, the outside rear should pull toward the outside of the corner, and should pull the tail with it. What am I missing? I understand that the effects of toe on the front and rear are different. The main benefit of toe out on the front is that it allows the front wheels to track in better arcs with less scrub. The inside wheel travels through a smaller radius, but also steers at a greater angle due to the toe out. Am I focusing on just the outside wheel in the rear too much? I can't see how rear toe in would enhance oversteer. Unless you are saying that the toe in reduces grip in the rear, increasing oversteer? Like running less negative camber in the rear?

 

Help me understand.

 

Thanks,

Jason K.

[Xenonk]

You are missing the relationship of what the car is doing while cornering.. remember, it's not what the car does while in the turn.. it's a matter of if you are accelerating or braking prior or during the turn.. in your case, just imagine if you are in a braking situation while putting the steering in.. the rear end is going to get light anyways from heavy braking.. a tire off the ground or have little downforce isnt going to do anything for the car. You have to not only looking the outside wheels, but to WHICH of the two outside wheels will have the major role of where the car will travel. And remember the front of the car is doing the pointing, the rear will do all the swinging for the pointing.

 

Camber can have its own unique traits as well, you can run too much camber in the rear that will result in oversteering because you are not effiecently putting down the correct contact patch on the ground. Toe affects in the sense of intended travel.. you should think of toe is based upon where the center of gravity of the car is in relationship with the toe alignments. Remember that you can also relocate the intended path of travel of the center of gravity and this is what the car needs to control using the 4 tires.

 

 

Keefe

[AWDpower]

You are missing the relationship of what the car is doing while cornering.. remember, it's not what the car does while in the turn.. it's a matter of if you are accelerating or braking prior or during the turn.. in your case, just imagine if you are in a braking situation while putting the steering in.. the rear end is going to get light anyways from heavy braking.. a tire off the ground or have little downforce isnt going to do anything for the car. You have to not only looking the outside wheels, but to WHICH of the two outside wheels will have the major role of where the car will travel. And remember the front of the car is doing the pointing, the rear will do all the swinging for the pointing. Camber can have its own unique traits as well, you can run too much camber in the rear that will result in oversteering because you are not effiecently putting down the correct contact patch on the ground. Toe affects in the sense of intended travel.. you should think of toe is based upon where the center of gravity of the car is in relationship with the toe alignments. Remember that you can also relocate the intended path of travel of the center of gravity and this is what the car needs to control using the 4 tires.

 

 

Keefe

 

I know what you are saying, and understand the effects of weight transfer and center of gravity. The one piece of the puzzle I'm missing is, why am I backwards on the effects of toe in Vs. toe out? Why/how does toe in make the car loose, and toe out make it stable? That is the opposite of what thought and have expirienced. It sounds counter intuitive to me. I also thought that many OEM rear suspensions were designed to toe-in under braking and cornering to make the cars "safer" (less likely to oversteer.) I'd like to understand how/why toe in would do the opposite, and make the car loose?

 

Jason K.

[sgt]

Rear toe out = oversteer

Rear toe in = stability

 

AWDpower is right