Thrust angle in rear - rear toe

[RPS13]

I found an alignment printout in my 4Runner from last year, they got the fronts reasonably aligned, and the rears didn't have any side to side toe difference really, but there was a reasonable amount of thrust angle.

Are there eccentrics on the rear axle to adjust toe? If not, anything aftermarket and not ridiculously expensive to adjust this?


The SUV drives fine on the road, but is a tad bit nervous at highway speed. I'm pretty sure some of that is from my XREAS being pretty dead (feels like very little to no damping), but there is some steering correction. Then again, I might be more tolerant than others as I've driven cars with zero toe on all four corners dailying for years with no real issues.

 

[BlackWorksInc]

The 4Runner uses a Solid Rear Axle, there are no eccentrics, no adjustability, I mean maybe you could use some shims, but hell I can't remember the last time I tried to shim an alignment...

I've wondered about using those MetalTech rear trailing arms to correct it, but they're not exactly high on my mod list at the moment. For reference, I have something like a .03* thrust angle on my truck and it tends to drift right a little, nothing to serious.

 

[RPS13]

The alignment sheet said something like 0.13* total thrust, which seems super high. I would think your steering wheel would be crooked as hell to hold that and any bumps would really throw it off, but the truck doesn't really feel that way. Steering wheel stays straight, and it generally tracks ok.

I'm thinking maybe they flubbed the rear sensor placement, as I've seen some techs not get them 100% seated and it throw off everything.


But that's what I thought when I looked under it, no eccentrics on the rear. It makes me wonder how they account for slight manufacturing variances in the frame and arm lengths. Nothing is perfectly made, so no adjustment just seems a bit odd.

 

[gm350reratliff]

Actually that isn't too bad. Thats 0.13 of a degree or roughly a 10th of one degree. Usually anything over .50° will start to have drivability issues.

 

[RPS13]

I'll have to look at it again, but I seem to recall it's about that. It just seems strange there is zero thrust angle adjustment back there. I guess they're worried that people would crank on adjustment and bind up the linkages, but the rubber bushings should be pretty tolerant of that.

So there's no aftermarket eccentrics?

 

[lehiguy]

I'll have to look at it again, but I seem to recall it's about that. It just seems strange there is zero thrust angle adjustment back there. I guess they're worried that people would crank on adjustment and bind up the linkages, but the rubber bushings should be pretty tolerant of that.

So there's no aftermarket eccentrics?

It seems you don't quite comprehend what solid axle means. There is NO adjustment. There will always be some small degree of variance from dead straight, either in the axle housing assembly or in the instruments used to get those measurements. Mine showed something not quite straight also, but it drives fine.

 

[RPS13]

It seems you don't quite comprehend what solid axle means. There is NO adjustment. There will always be some small degree of variance from dead straight, either in the axle housing assembly or in the instruments used to get those measurements. Mine showed something not quite straight also, but it drives fine.

I understand perfectly what a solid rear axle is, and apparently you don't know what thrust angle is and how it differs from individual toe adjustments.

I've also worked with a few solid rear axles that you could easily adjust the rear thrust angle (and the roll center location, and anti-squat etc.). I was pretty sure the factory adjustment didn't have a provision for rear thrust angle, so that's specifically why I asked about cheap aftermarket solutions.


Anyway, the 4Runner drives great, and the optimistic OBC is reporting 24 mpg (was up to 24.5 mpg, but I changed the diff fluid to 75W-140, and it's been at 24.2 mpg over the past couple of days). So I don't think there's much cause for concern.

Next step, ditching XREAS!

 

[BlackWorksInc]

I understand perfectly what a solid rear axle is, and apparently you don't know what thrust angle is and how it differs from individual toe adjustments.

I've also worked with a few solid rear axles that you could easily adjust the rear thrust angle (and the roll center location, and anti-squat etc.). I was pretty sure the factory adjustment didn't have a provision for rear thrust angle, so that's specifically why I asked about cheap aftermarket solutions.


Anyway, the 4Runner drives great, and the optimistic OBC is reporting 24 mpg (was up to 24.5 mpg, but I changed the diff fluid to 75W-140, and it's been at 24.2 mpg over the past couple of days). So I don't think there's much cause for concern.

Next step, ditching XREAS!

I have never seen a solid rear axle that you could adjust toe on, unless you used shims...

 

[RPS13]

I have never seen a solid rear axle that you could adjust toe on, unless you used shims...

All aftermarket 4 link setups are completely adjustable for the things I've mentioned.

What about a solid rear axle setup makes you think you cannot adjust thrust angle? Now if the factory gives you that adjustment - that's pretty rare as most people (i.e. alignment shop flunky) are just going to bind up the linkages.

 

[BlackWorksInc]

All aftermarket 4 link setups are completely adjustable for the things I've mentioned.

What about a solid rear axle setup makes you think you cannot adjust thrust angle? Now if the factory gives you that adjustment - that's pretty rare as most people (i.e. alignment shop flunky) are just going to bind up the linkages.

Maybe its because its late and I can't picture it right... but how do you adjust individual toe on a solid REAR axle?

As for the specification, Toyota doesn't give you one. I've thought of getting MetalTech Upper and Lower Links to gain a bit more adjustablity though, which is what I assume you're talking about.

 

[RPS13]

THRUST ANGLE. Not individual toe, but adjusting the whole axle in toe (toe out on one side, toe in on the other or vice versa). That is the definition of thrust angle.



But you can heat and bend a solid rear axle slightly to introduce camber and or toe, but obviously that's not what I'd call a real adjustment. Race cars do it all the time though, but you can only do a very small amount for obvious reasons.

 

[BlackWorksInc]

THRUST ANGLE. Not individual toe, but adjusting the whole axle in toe (toe out on one side, toe in on the other or vice versa). That is the definition of thrust angle.



But you can heat and bend a solid rear axle slightly to introduce camber and or toe, but obviously that's not what I'd call a real adjustment. Race cars do it all the time though, but you can only do a very small amount for obvious reasons.

That's what I figured you meant by toe adjustment, but I wanted to make sure. :tea:

 

[gm350reratliff]

One could always just grind out the mounting holes little by little until you get it perfect. Then use some tooth washers so it holds better.

The only solid axle vehicle that I can think of being able to set rear toe is those GM trucks and suburbans that had 4-wheel steering. Bad thing with those is your pretty much stuck with dealers for alignments. You have to use the rear alignment procedure in the Tech2 (rear toe, thrust angle, check camber) before you can even think about doing the front.