Alignment issue?

[Buldawg76]

Have a somewhat academic question re: alignment--

When a car is put on a modern alignment rack, it bases the thrust angle off not only the rear axle, but a line between the center of front and rear axles (i.e. geometric centerline), correct?

If it was just the rear I'd imagine you wouldn't need an alignment after installing the irs centering sleeves, as an alignment machine only knows the position of the wheels, not the body.

No, it uses the orientation of the rolling direction of all four tires to determine the thrust angle based off the fixtures that are attached to the wheels. It does not care about the centerline of the vehicle and has no way other than the wheel positions to determine the centerline.

The wheels will have a natural tendency to want to roll away from the center of the vehicle when moving and it calculates this force as a thrust angle for the positions of the 4 wheels combined to give an indication of how straight the vehicle will want to travel when moving or put another way how much force there will be trying to push the vehicle in one direction or the other when moving.

When you loosen the rear subframe and install the centering bushing or do anything else to the subframe it will never be bolted back up into the exact same position as it was before it was loosened so the rear alignment will be off from before the work was performed. It's up to you if you are willing to take a chance on it being close so as to not wear the tires out in a few hundred miles or not or have a car that want to track one direction or the other constantly that you will always be fighting to keep straight in the road.

When I did mine the 4-wheel alignment only cost 58 bucks and my thrust angle in 0.02 degrees so well worth the cost IMO.

BD

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[Buldawg76]

@mustangpegasus51 But the components that do control the alignment and the control arms themselves attach to that subframe. Thus, if you moved the subframe, those components inevitably have to move, and thus the wheels have to move. How much will depend on how much you had to move the subframe to get it aligned with your dowels.

Now, you'll have to make some risk assessments on how much yours moved. Take my scenario for example. When installed my dowels, I did one hole at a time. I got super lucky and found that my subframe was dead center. I was able to get all four of my dowels in, one at a time, without any fuss, prying, or pressure. Since I never had more than one bolt at a time lose, I made the educated assumption that the subframe did not move in this install process. Thus, I decided a check of the alignment was not necessary.

Someone back me up on this next part (or call me out), but it's my understanding that if rear toe is spot on match side to side, thrust angle should be pretty darn near zero°.

Unless you had your car aligned prior to know for sure the alignment was correct before work was done then you are just assuming your alignment was good prior to said work and even though you only did one bolt at a time does not insure the subframe went back in the exact same position.

Keeping a close watch on tire wear will tell you very quickly if the alignment is good or not. How well the car tracks in terms of wanting to pull or drift one-way or the other will give you an indication of thrust angle but not necessarily relate to tire wear.

I would rather pay for an alignment than new tires and also an alignment to keep the new tires from wearing out again.

You may get lucky, but you may not.

Just my 0.2 cents worth.

BD

 

[galaxy]

@Buldawg76 I completely agree with what you're saying about knowing the alignment is correct. I was simply stating that with a jack in place supporting the subframe, and then doing one bolt at a time, it's pretty unlikely the subframe moved, thus retaining whatever alignment was there at the start of the job (be it right or wrong, LOL). Not something I'm losing sleep over. I need tires and would get an alignment anyways (completely aside from the fact I added the dowels). Car drove exactly the same before and after. Zero odd rear tire wear.

 

[Buldawg76]

@Buldawg76 I completely agree with what you're saying about knowing the alignment is correct. I was simply stating that with a jack in place supporting the subframe, and then doing one bolt at a time, it's pretty unlikely the subframe moved, thus retaining whatever alignment was there at the start of the job (be it right or wrong, LOL). Not something I'm losing sleep over. I need tires and would get an alignment anyways (completely aside from the fact I added the dowels). Car drove exactly the same before and after. Zero odd rear tire wear.

I was not saying or meaning you were wrong in your assumptions or absolutely needed an alignment after installing the bushing since you only did one at a time and supported the subframe while doing so. Just that I have seen alignments be quite far off from the factory so if the vehicle has never had the alignment checked/adjusted then it may be ok or could be out of spec as well.

I know that every new ford comes with a free alignment check within the first either 6 or 12 months of ownership to original purchaser, just not sure if owners are aware of that free service and have it performed. My dealer informed me of the service so that I could utilize it on my vehicles.

BD

 

[galaxy]

I was not saying or meaning you were wrong in your assumptions or absolutely needed an alignment after installing the bushing since you only did one at a time and supported the subframe while doing so. Just that I have seen alignments be quite far off from the factory so if the vehicle has never had the alignment checked/adjusted then it may be ok or could be out of spec as well.

I know that every new ford comes with a free alignment check within the first either 6 or 12 months of ownership to original purchaser, just not sure if owners are aware of that free service and have it performed. My dealer informed me of the service so that I could utilize it on my vehicles.

BD

Oh for sure! I didn't do it with this car, but I did with a truck I bought new, and for some reason, 12/12K comes to mind.

 

[Buldawg76]

Oh for sure! I didn't do it with this car, but I did with a truck I bought new, and for some reason, 12/12K comes to mind.

Yep, I believe you are correct, just couldn't remember the specifics.

BD

 

[mustangpegasus51]

No, it uses the orientation of the rolling direction of all four tires to determine the thrust angle based off the fixtures that are attached to the wheels. It does not care about the centerline of the vehicle and has no way other than the wheel positions to determine the centerline.

The wheels will have a natural tendency to want to roll away from the center of the vehicle when moving and it calculates this force as a thrust angle for the positions of the 4 wheels combined to give an indication of how straight the vehicle will want to travel when moving or put another way how much force there will be trying to push the vehicle in one direction or the other when moving.

When you loosen the rear subframe and install the centering bushing or do anything else to the subframe it will never be bolted back up into the exact same position as it was before it was loosened so the rear alignment will be off from before the work was performed. It's up to you if you are willing to take a chance on it being close so as to not wear the tires out in a few hundred miles or not or have a car that want to track one direction or the other constantly that you will always be fighting to keep straight in the road.

When I did mine the 4-wheel alignment only cost 58 bucks and my thrust angle in 0.02 degrees so well worth the cost IMO.

BD

Thank you for this info! I think this is all coming together for me.

Since purchase I've had an issue where the stance never quite looked right, even when alignment was spot on. Also for quite a while it's felt a bit different turning left vs right.

Now I think I know what it is--all my wheels are pointed left with respect to the body. See below for an image of what I mean.

 

[Buldawg76]

Thank you for this info! I think this is all coming together for me.

Since purchase I've had an issue where the stance never quite looked right, even when alignment was spot on. Also for quite a while it's felt a bit different turning left vs right.

Now I think I know what it is--all my wheels are pointed left with respect to the body. See below for an image of what I mean.

Thats an extreme example of severe thrust angle offset and is why anytime you work on the vehicle wheels/suspension you need to have an alignment check.

BD

 

[mustangpegasus51]

I see what you're saying. I've actually gotten 10 alignments since purchase, trying to figure out why the wheels always sat weird in relation to the body. However, when you told me that an alignment rack goes off of where the wheels point when moving (regardless of where they are in the body) it clicked.

Car drives straight enough, but considering my left rear wheel is toe out and my right rear is toe in (in relation to the body) when the wheels are straight (according to the alignment machine), likely means the body itself isn't centered on them. I originally thought this was mostly the front cradle, but the front frame rails flank the edges of the front cradle, offering little play.

The real question is: where to go from here? As said the vehicle drives straight, but the steering feel is awful (it's more difficult to steer right vs left.) Part of me thinks it might not be true setback and all, and maybe it's a ride height/shock/spring issue in disguise.

I could uninstall the steeda kit, ask a body shop to center the rear based off of frame measurements instead, but then what's to stop the rear cradle from moving back to the place it was? On that same token, maybe just getting rid of the steeda sleeves and just driving things stock might be the best course of action.

 

[GTP]

Keep the Steeda sleeves. They are part of the solution and not part of the problem. Once you get this figured out, they will be your friend anytime you lower the rear cradle because another alignment is not required.

If you are going to a shop with Hunter Hawkeye, then ask the manager to schedule you at a time when his best alignment guy can do your car. Us picky Mustangers are looking for small fractions of a degree - both absolute and error.
Have the car pulled onto the rack very straight. Have him put the lasers on the center of each wheel.

Raise your steering wheel so you can better eyeball the cross spoke is parallel to a reference on the dash.

Have him check your wheel bearings and toe links for excessive slop.

Stuff like that. Time to be obsessive.

 

[Buldawg76]

Definitely keep the sleeves since they keep the subframe centered better than not having them. As to the subframe shifting during use the top of the inner sleeves in the bushings are serrated so that when the bolts are torqued to 129ft/lbs they bite into the chassis metal and there will not be any movement possible between the subframe and body short of a severe impact to the chassis such as in a wreck. When you go to install the sleeves and look up into the holes you will see the serrations on inner sleeves and marks on the chassis from them.

It could be very possible that your fenders or body panels from the front to the rear are not actually straight with the frames/chassis dimensions thereby giving you the differences in wheel placements in the wheel well openings. It could also be that the chassis mounting threaded holes for the subframe were incorrectly stamped into the floor pan which put every other part that locates off of those points askew and the tolerance stackups is what you see with the wheel placements in the wheel well.

Any quality frame shop can measure your chassis and critical location points and be able to tell you if there is something out of spec and possibly correct it to get the car back do a straight wheel/chassis/body relationship.

Keep us informed if you have it checked out.

BD

 

[AvalancheSVT]

that's really bad. an alignment won't fix that, the cradle is not lined up properly. that's a warranty issue. this is one of the main things i'll be checking when i pick up my car. tolerance of +/- 1/16 is fine but more than that and you're gonna see it.

while you can align the car to make it drive straight that doesn't fix the real problem.

i went through this when i installed IRS on my cobra. i had to wallow out a bolt hole to get the subframe to where it would put the wheels in the right spot. that is probably why ford allows adjustment of these things but it seems like some of them aren't getting set up right from the factory.

 

[Coyote 2121]

ALRIGHTY!
Finally got my BMR cradle lock out kit and my Steeda centering dowels installed yesterday morning.
The cradle was definitely out of whack and required manipulation to get 3 of the 4 blue bolts started.
Originally my driver's side wheel was perfectly centered in the wheel well and the passenger side was I'd guess about 1/4 or more forward.
After the install both rear tires are exactly the same distance from the front portion of the wheel well, although both are slightly forward of center. But at least now they match.
I have a 4 wheel alignment scheduled for tomorrow morning, but interestingly, the car still tracks perfectly straight on the hiway?
Same as before.
But I will say, GOTDAMN, all the rear end slop and loose feeling is completely gone!
The tires still spin a little when the trans shifts, but that feeling like the rear end is kicking out is gone!
It feels 100% better and more stable.
So those kits were well worth it.
I ended up going to a coworkers house, he's a mechanic where I work and has a lift.
Took us about 2 hours, not knowing what we were doing and all, plus fighting 3 out of 4 of the bolts.
Now my woman, whose 21 GT has exactly the same rear issue, wants the same kits, so I'm sure we'll get hers knocked out much quicker.
Thanks to all of you for all the tips and suggestions to make the install go easier!

 

[GTP]

I had a feeling this would turn out to be simple. Glad everything worked out.

Heck if your friend has a 4 post lift then you can consider a string alignment kit. I just received my Caliper Garage kit which costs less than an alignment at the tire shop. My friend has a lift where we will align our cars. Toe in is our main concern.

 

[Some Random Guy]

I’m curious to see your alignment. After the BMR kit and dowels I took mine in and the front was out of spec, not the rear. I think it was cross camber, but might have been cross caster. Neither of which were impacted by my work on the rear IRS if I understand correctly.
For anyone else stumbling across this and reading about install I can’t recommend a transmission jack enough for this job if you don’t have a post lift. If you’re doing the dowels you can loosen everything and nudge the subframe around really easily. I’ve done 2 of these now and each time was able to hand tighten the 4 bolts with a little finesse and some occasional pressure from a floor jack in a key area to tilt the subframe the way I needed.

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