Where do you measure toe-in

I believe toe-in at tread diameter is "standard."
Attached manufacturer's specs (from Volvo) show equivalent spec at a variety of locations including the angle.


As several others said Creating a reference plane by rotating the tire ( with wheel bearings temporarily adjusted tight) is important. Rolling forward or back 1/2 tire rev so the exact same tread or wheel feature is referenced effectively creates a reference plane and compensates for rim runout and inevitable molded tire variations.
Any measurement made using the tread features or sidewall or even the rim ignores rim etc variations and run the risk of being off by 1/8 inch or more, which is basically the entire targeted toe-in. Much Better than 1/2 inch toe in or toe out, but not "aligned" where I think I am. Kind of like using "that" tape measure. You know, the one with a few inches were snipped off the end and the hook re-attached.

Some alignment machines setup includes creating a plane.
Some machines clamp a fixture to the machined face of the hub just outside the bore where the grease cap fits. I would not trust that surface until I had de-burred and indicated it.

 

Typical question, Hoop what time is it?

Typical Hoop Answer:


I’m trying to understand how time works. And that’s a huge question that has lots of different aspects to it. A lot of them go back to Einstein and spacetime and how we measure time using clocks. But the particular aspect of time that I’m interested in is the arrow of time: the fact that the past is different from the future. We remember the past but we don’t remember the future. There are irreversible processes. There are things that happen, like you turn an egg into an omelet, but you can’t turn an omelet into an egg.

And we sort of understand that halfway. The arrow of time is based on ideas that go back to Ludwig Boltzmann, an Austrian physicist in the 1870s. He figured out this thing called entropy. Entropy is just a measure of how disorderly things are. And it tends to grow. That’s the second law of thermodynamics: Entropy goes up with time, things become more disorderly. So, if you neatly stack papers on your desk, and you walk away, you’re not surprised they turn into a mess. You’d be very surprised if a mess turned into neatly stacked papers. That’s entropy and the arrow of time. Entropy goes up as it becomes messier.

Oops it's 11:24 sorreeeee

 

And since I'm in the Eastern time zone, your post shows a time of 12:24. Just sayin'

 

Hoop, you got it! That is one grand visual there.
It has always struck me that the physics boys (Boltzman, Maxwell, etc.) would build relationships using Entropy. It essentially says, "Your number increased...because you stopped in Vegas, when you should have gone straight home."
When energy is spent, played out, dissipated (no harm meant here!)
tell me the logic, that you have increased, or have received, a net gain?
Syntropy doesn't quite invert the prior term, as it is generally used to describe a sum, that is greater than the individual component efforts or effects.

 

Exactly! I am (was) a pro.

 

It matters less where you measure it, than the place where the spec originates from measures, so that you can duplicate it or compensate for it.



The scribe line works best for me, but then on karts we use lasers.

 

Im still only at 10:48. Its like i can remember the future because from my point of time what hoop said hasnt even been said yet. But it most certainly will become more disorderly by the time it gets here.

 

Just use two pieces of plywood the same dimensions and slightly larger than the tire diameter. With the plywood against the wheels adjust till a tape measure at the front and the back sides of the plywood reads the same. Add toe in from there, don't add more than 1/8" toe in or you'll start s****ing rubber off the tires.

 

We did my 40 coupe last week with these.....

 

If you used the tread centerline at axle (spindle) height I doubt any shop could do it better.

 

The diameter of the tire would affect the toe in geometry if measured from the tire... if I've got 36 inch tires with 1/8 "toe in" measured at the tread and then measure 1/8 "toe in" on 24 inch tires at the center of the tread, the 24 inch tires are more toed in more than the 36" tires... so that begs the question; is toe in about tire or suspension alignment?

doesn't toe in also help the steering to "center" itself?

 

It doesn't matter where it is measured, as long as it is measured fore and aft of the spindle nut in the same plane. The aft measurement should be slightly larger than the fore measurement.

 

One more little detail that I haven't seen mentioned here is radial tires. I was taught that radial tires should have less toe in than regular bias-ply tires. The charts I have showed from 0 to 1/16 in. toe in with radials while bias-ply would be 1/8 in. same vehicle.

That was a long time ago but I think it still applies.

Thanks, Dave.

 

Caster is what causes the steering to re-center. Toe-in takes the slack out of the steering linkage and helps to stop wandering. Also, can use toe-in to correct tire wear problems on a vehicle that has no camber adjustment. Negative camber will cause tires to wear on the inside. Increasing the toe-in a little can lessen that tire wear by pushing the wheels together. Too much toe-out will also cause tires to wear on the inside, you have to read the scuff pattern to distinguish between toe-in and camber. Too much toe-in will cause low speed shimmy as will extremely out of balance tires.

I've found that having the steering wheel centered while driving down the road with just enough toe-in to take the slack out of the linkage is best. Having the correct caster and camber adjustments before hand goes without saying. Toe-out on turns and kingpin angle while not adustable are good indicators of bent suspention parts.

Dave.