Rearend camber

[Dr Goggles]

Bye the way a touch is a very precise measurement related very closely to a smidgen!

Pete

a smidgen is ten poofteenths, whereas a bees-dick is three fifths of five eighths of F all. Either way these measurements are below the usual tolerances of the human eye multiplied by the tolerance of the calipers you just stepped on.

[Count]

LOL
Ok, so now all I have to do is figure out just how much that is.

[landsendlynda]

Ask your wife.  If she does any home cooking at all, she can tell you!

Lynda

[willieworld]

i asked sheri she said when she was younger she used to have a lot of toe out but as she gets older gravity has taken its toll         willie buchta

[maguromic]

Saltfever, This is one of my floater hubs.  When we ran in IMSA we made up spacers for the inside to keep the bearings from riding up on the axle snout to cut down on drag.  Also I built a dry sump for my 9” in my gas roadster.  It is very similar to the one that the Corvette team used at Lemans on there 9”.   I also tested that setup on a test rig I built against others and saw the gains.  I posted some pictures on another thread of the dry sump system.  Tony

[saltfever]

The same angle of toe-out and toe-in, the toe-out will have a much more pronounced force applied trying to steer the car from the back end.  It acts on the CG, and has far more "leverage" against it.  And a certain amount of toe in will make it so no steering input is required to go "straight" even when the rear tire traction is very unequal.

Thanks, McRat. I can't argue about your personal experience I'm just having trouble understanding it. Maybe there were other things influencing toe and they affect "out" more than "in". But in my mind if out or in toe angles are equal then the force should be equal but in different directions. To keep it simple think of a motorcycle. If the rear wheel is misaligned and pointing to the right the bike will go that way. If the wheel points left then left you go. To me a car wheel acts the same way. The CG is the location that everything pivots around. Whether the toe is out or in only affects the direction of spin. But as you mention there is uneven traction, and the other tire, so maybe I'm missing something. At any rate this is a thought provoking thread and has gotten me thinking, and focusing, on how critical alignment is. I would have not considered checking the straightness of my rear end until I read this thread. Alignment to the frame yes, but straightness I would have missed. Many thanks to all.

Tony thanks for posting the picture. It alleviates a concern I had.     

[Peter Jack]

The simple way to measure if a rear end is bent when the axle is out of the car is to mount a set of wheels. Block the wheels so they can't roll, then roll the axle through 360 degrees. A tape measure between the two wheels during the rolling process will show if the rear is bent and how much. If the amount is at all significant you will notice a wobble in the wheels.

Pete

[saltfever]

Thanks for the idea, Pete. I was going to mount a bar on each side with a cheap mag base laser projecting forward only to get toe and missed the idea of "swinging" the housing. I'm assuming you are talking about a floater otherwise the wheels would have to be mounted to the axles. If it is a floater is there bearing slop or other built-in clearance that I should be aware off when swinging the housing?  TIA 

[Peter Jack]

It will work with any rear axle. The wheels are mounted on the axle and held in place by the blocks while you swing the axle housing. Its commonly used in oval track racing where there's lots of contact. The laser will work just fine to detect any camber or toe errors. Just note where the housing is in relation to the pointer.

The next trick is using a rosebud torch to straighten a bent housing.

Pete

[Count]

Hell Yeah!  Fire up the oxyacetylene!  I love those old fabrication techniques.

[Rex Schimmer]

 I always used the welder method to straighten a housing. Find out were the most bend is and then lay a bead on the concave side and quench it with a wet rag. It will pull the bow right out of a nine inch housing. I did it to a nine inch that was in a Mazda RX7 during the Daytona 24 hours once.

Saltfever, a car is not even close to a bike from the affects of wheel missalignment. If every thing on a car when moving did not change, no weight transfer, no flexing, no bumps, no outside disturbances at all, then toe in or toe out might not affect the cars handling. But since we don't live in a perfect world, thank God, toe out will be much more destablizing than toe in on a race car. In the venacular of NASCAR, toe out make you "lose" and toe in makes you "tight" and lose is not a stable condition.

Ever driven a fork lift? There is a real case of rear toe steer, and unstability.
Rex

[saltfever]

As a matter of fact in my days as a starving student I drove a forklift for Golden Grain Marconi and became quite proficient at it. With time and practice your subconscious will sense subtle nuances of rear steering that gives you an enhanced capability you could not have if you tried to process all feedback consciously. But I digress . . . 

Sorry for trying to simplify with the motorcycle example because you are right about all the disturbances that affect a 4 wheel vehicle. So here is the deal. There is a vast difference on whether the steering axis is before the CG or after the CG. The former is an inherently stable condition. If the steering input is behind the CG then the CG adds to the lateral acceleration . . . an unstable condition!  As you mentioned there are many disturbances. Because of the disturbances we are assuming that one rear wheel has enough influence to start a deviation from the longitudinal track. I don’t care if it is toed in or out. That wheel will move the car in the direction the wheel is pointed and since it is behind the CG (and with a shorter couple) the force to correct or stop the course deviation is far greater than front-steer. I understand the “feel” of loose or tight and how toe causes either effect. However, I think we are confusing front-steer “feel” with rear-end physics. Intuitively, we assume toe-out is bad in back because that is the effect up front. However, if you are traveling in an absolutely straight line and the car’s rear end darts to the left (because disturbances to the wheel that takes command has toe-in)  the deviation from track is going to be quick and difficult to stop because the lateral acceleration of the CG is in the direction of travel! 

I'm not trying to be argumentative here. I hope you guys consider this a discussion. I'm just trying to understand why there is some preference to toe-in. As I think about this I'm starting to think any rear end toe is a very bad situation. Either case is unstable due to its position behind the CG. And building in any propensity to go left or right of track is precarious.

"Loose" or "tight" are simply the same as understear or overstear. Compared to "neutral" all those are unstable conditions. LSR travels in a straight line. I suspect "neutral" is the best condition. 

[McRat]

Thinking more on it, it's possible that rear toe out might induce rear end oscillation.  I was just looking at it like a flat board, but it's 3D.  The CG is above the thrust point on the tires.  If you try to "pull" the CG to the right, it would apply downforce to the opposite tire, making it the new dominant tire, then swap back and forth.  With toe in, the dominant tire tries to lift the opposite tire, so it maintains it's dominance. 

[saltfever]

Hmmm, interesting and good point. The tire with toe-in will remain dominant but it is still pointed to the left. Me thinks it wants to drive the CG to the left. If that tire remained dominant but was pointed forward (zero toe) the tendenancy would be to track straight.

[stratman59]

I know this isn't my post but thanks for all your helpful insight. I has been very informative.

Later
Robbie