The effect of Rake on Wheel Alignment?

[jross20]

Been trying to solve the alignment issues I've been struggling with...when I had the idea that I might be shooting myself in the foot with my front lift.
:dizzy:
I presume that the rake, the different from front lift to the back, would effect the geometry of the front suspension and as such I presume alignment would be effected.
:ranger:

So with that said, do we know what the maximum rake is for proper alignment geometry? 1", 1.5" 2", etc.

 

[icyhotahs]

It's times like these I try and remember that unlike the cars of old, manufacturers tend to design the vehicles with geometry that doesn't wear short or cause problems down the road.

All that to say (don't shoot the msgr) that the factory rake has been mentioned to be about 2" (+-.5). Again, all vehicles are different, and as mods go on that goes out the window.

 

[Bad Luck]

Been trying to solve the alignment issues I've been struggling with...when I had the idea that I might be shooting myself in the foot with my front lift.
:dizzy:
I presume that the rake, the different from front lift to the back, would effect the geometry of the front suspension and as such I presume alignment would be effected.
:ranger:

So with that said, do we know what the maximum rake is for proper alignment geometry? 1", 1.5" 2", etc.

Rake has very minimal effect on alignment. The higher you lift from OEM height in the rear the more the rear axle will shift to the right in relation to the frame rails. The higher you lift the front from OEM height the further your caster/camber will be off WITHOUT getting another alignment.

EDIT: What are your alignment issues that you’re having?

 

[phattyduck]

One inch of lift in the rear is approximately equivalent to 0.5* change in frame angle. So, 2" of rake = about 1* of lost caster. The effect on camber will be basically non-existent. Front and rear center of hub to fender lip measurements were near equal from the factory.

Geometry is your friend...

-Charlie

 

[19963.4lsr5]

When I had first got the 97 Puppy hauler it wanted to follow road groves bad and toe seemed fine.

It ended up being the caster was off the upper balljoint was too far forward.


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[jross20]

Rake has very minimal effect on alignment. The higher you lift from OEM height in the rear the more the rear axle will shift to the right in relation to the frame rails. The higher you lift the front from OEM height the further your caster/camber will be off WITHOUT getting another alignment.

EDIT: What are your alignment issues that you’re having?

Well in a nut shell, I've been to around 8 alignment shops in the past 365+ days and not one can get it right. Totally ruined my tires and she is all over the road. It sucks.

And that's with the spc arms. Main issue is that even the "off-road" shops have no idea how to use the SPC arms. It's also hella expensive so I can't just keep getting one after another.

Basically I was thinking if I have a 3" lift in the back and a 1" in the front, would that be too much of a difference and be part of the problem

 

[Bad Luck]

Well in a nut shell, I've been to around 8 alignment shops in the past 365+ days and not one can get it right. Totally ruined my tires and she is all over the road. It sucks.

And that's with the spc arms. Main issue is that even the "off-road" shops have no idea how to use the SPC arms. It's also hella expensive so I can't just keep getting one after another.

Basically I was thinking if I have a 3" lift in the back and a 1" in the front, would that be too much of a difference and be part of the problem

Do you have a recent alignment printout? Have you replaced the lower control arms or bushings?

 

[jross20]

Rake has very minimal effect on alignment. The higher you lift from OEM height in the rear the more the rear axle will shift to the right in relation to the frame rails. The higher you lift the front from OEM height the further your caster/camber will be off WITHOUT getting another alignment.

EDIT: What are your alignment issues that you’re having?

Do you have a recent alignment printout? Have you replaced the lower control arms or bushings?

I usually keep them for a while, but I think the last one finally got trashed maybe like a month ago while I was cleaning out my desk.

Yes I have actually replaced the lower arms and bushings, all OEM.

 

[Bad Luck]

I usually keep them for a while, but I think the last one finally got trashed maybe like a month ago while I was cleaning out my desk.

Yes I have actually replaced the lower arms and bushings, all OEM.

Well that's unfortunate. Without looking at the measurements I can't really help much. What kind of tire wear are you experiencing? Here's a reference if you need it: Your Guide to What Tire Wear Patterns Really Mean | Metromile

 

[jross20]

Well that's unfortunate. Without looking at the measurements I can't really help much. What kind of tire wear are you experiencing? Here's a reference if you need it: Your Guide to What Tire Wear Patterns Really Mean | Metromile

Yeah I know, I really need to start keeping those. I can tell you that everything was technically in the green, but being in the green and being straight are two different things... The tow, camber, and the rear thrust were just all over the place

Basically cupping and general uneven wear.

 

[Bad Luck]

Yeah I know, I really need to start keeping those. I can tell you that everything was technically in the green, but being in the green and being straight are two different things... The tow, camber, and the rear thrust were just all over the place

Basically cupping and general uneven wear.

Rear thrust isn’t adjustable with the stock rear control arms, but bad rear control arm bushings could cause a loose rear end.

Generally speaking cupping is caused by bad toe or bent suspension components affecting your TOOT (toe out on turning). I can’t speak for every alignment machine out there, but the 4 different hunter units I’ve used for work don’t automatically check TOOT. I have to select the TOOT measurement procedure.

In other words, I don’t think any of the alignment places have checked your TOOT. If it’s bad then that means a suspension component/mount or frame by the suspension is bent. Might be something to consider if you get another alignment.

 

[IBallEngineer]

One inch of lift in the rear is approximately equivalent to 0.5* change in frame angle. So, 2" of rake = about 1* of lost caster. The effect on camber will be basically non-existent. Front and rear center of hub to fender lip measurements were near equal from the factory.

Geometry is your friend...

-Charlie

I spent a number of years training techs on alignment and alignment equipment. People love to say that changing the rear height does all this hocus pocus on front caster, you can draw it on paper, or on a computer so it must be true. Truth is it isn't true. I've tested a number of cars, not enough to have a scientific study, but more than one. Specifically my 99 with changes as big as 3.5" and had almost NO CASTER change on the front wheels! Or NO CASTER change at all. Now I could have made a mistake, but I didn't, I did the roll back on my 99 about 20 times with just two rear heights. stock and 2" higher, I only checked it once maxed out at 3.5" on the airlift 1000's. At 2" there was no change, or .1 degrees, at 3.5" it did change, but that was 2-1/2 years ago, or more, so I don't remember the amount. I think it was about .2 -.4 degrees. Now if you look up some specs for older chevy trucks, they gave you caster specs based on rear ride height. That is to say they wanted you to CHANGE caster based on rake, not necessarily that it would be changed. MBZ and some other manufacturers base ALL their specs off of ride height, both front and rear. I tried changing the ride height on an E36 and an E39, not huge amounts but I did get small changes in Caster reading but the change was small, maybe 1/2 to 3/4 of an inch.
I'm a huge fan of science, but like my Frame man used to say, the parts don't lie.
For our purposes(3rd Gen) I think it is a negligible consideration for overall caster readings.
I should have saved all those readings... I should'a ....

 

[phattyduck]

I'm a huge fan of science, but like my Frame man used to say, the parts don't lie.
For our purposes(3rd Gen) I think it is a negligible consideration for overall caster readings.
I should have saved all those readings... I should'a ....

Jross has SPC arms, so even if there was a difference due to height, it could be all 'removed' with correct arm settings. And I definitely agree that the measurements don't lie.

If the alignment is correct, I would suspect bad bushings somewhere.

-Charlie

 

[jross20]

Rear thrust isn’t adjustable with the stock rear control arms, but bad rear control arm bushings could cause a loose rear end.

Generally speaking cupping is caused by bad toe or bent suspension components affecting your TOOT (toe out on turning). I can’t speak for every alignment machine out there, but the 4 different hunter units I’ve used for work don’t automatically check TOOT. I have to select the TOOT measurement procedure.

In other words, I don’t think any of the alignment places have checked your TOOT. If it’s bad then that means a suspension component/mount or frame by the suspension is bent. Might be something to consider if you get another alignment.

You know that's interesting, even when I was back in automotive class years ago I don't think we ever learned about TOOT. That basically confirms what you're saying because I was even certified without them teaching that...

Should I just request a TOOT check?

I spent a number of years training techs on alignment and alignment equipment. People love to say that changing the rear height does all this hocus pocus on front caster, you can draw it on paper, or on a computer so it must be true. Truth is it isn't true. I've tested a number of cars, not enough to have a scientific study, but more than one. Specifically my 99 with changes as big as 3.5" and had almost NO CASTER change on the front wheels! Or NO CASTER change at all. Now I could have made a mistake, but I didn't, I did the roll back on my 99 about 20 times with just two rear heights. stock and 2" higher, I only checked it once maxed out at 3.5" on the airlift 1000's. At 2" there was no change, or .1 degrees, at 3.5" it did change, but that was 2-1/2 years ago, or more, so I don't remember the amount. I think it was about .2 -.4 degrees. Now if you look up some specs for older chevy trucks, they gave you caster specs based on rear ride height. That is to say they wanted you to CHANGE caster based on rake, not necessarily that it would be changed. MBZ and some other manufacturers base ALL their specs off of ride height, both front and rear. I tried changing the ride height on an E36 and an E39, not huge amounts but I did get small changes in Caster reading but the change was small, maybe 1/2 to 3/4 of an inch.
I'm a huge fan of science, but like my Frame man used to say, the parts don't lie.
For our purposes(3rd Gen) I think it is a negligible consideration for overall caster readings.
I should have saved all those readings... I should'a ....

Well I can't argue with that, haha.

Jross has SPC arms, so even if there was a difference due to height, it could be all 'removed' with correct arm settings. And I definitely agree that the measurements don't lie.

If the alignment is correct, I would suspect bad bushings somewhere.

-Charlie

Okay so I've got the truck dropped off this morning for an alignment and I gave them very specific instructions that I got from the SPC website.

Basically I told him to set the eccentric bolts to zero, use the SPC arm's adjustments to get the alignment as close as possible, then to use the eccentric bolts to fine tune it the rest of the way.
The shop also claimed to have some experience with these arms... So we shall see..

And I guess based on what someone said above, I'm going to ask about that toe out on turn.

 

[Bad Luck]

You know that's interesting, even when I was back in automotive class years ago I don't think we ever learned about TOOT. That basically confirms what you're saying because I was even certified without them teaching that...

Should I just request a TOOT check?

If I was you I would ask them to check TOOT. Maybe say something along the lines of you think you have a bent suspension component that might be causing tire wear and ask if they would check it. The procedure only takes a few minutes if I remember correctly. I usually only do it if the customer admits to hitting something, I can tell the suspension got hit, or if the vehicle looks like the owner drives by braille.

 

[jross20]

If I was you I would ask them to check TOOT. Maybe say something along the lines of you think you have a bent suspension component that might be causing tire wear and ask if they would check it. The procedure only takes a few minutes if I remember correctly. I usually only do it if the customer admits to hitting something, I can tell the suspension got hit, or if the vehicle looks like the owner drives by braille.

Okay so unfortunately the shop really didn't know what I was talking about, however they were able to achieve what I will say so far is probably the best alignment up to this point.

It's past my bedtime, so I'll snap a photo of the results and post it tomorrow to see what you guys think.

Note that I also increased the front lift with the king's adjustment. Maybe it helped? Maybe it didn't, oh well

 

[jross20]

Alright here she is. The top might not look too bad, but man did she drive awful.

Honestly this shop has probably does the closed alignment I've ever gotten on this truck:

 

[Bad Luck]

Alright here she is. The top might not look too bad, but man did she drive awful.

Honestly this shop has probably does the closed alignment I've ever gotten on this truck:

That’s a pretty good alignment at the end. Judging by your before camber I wonder if the previous alignment they didn’t tighten the nuts on the spec ball joint enough. Any changes to camber from a loose nut will change toe and can cause a pull from uneven camber and tire cupping from too much total toe.

 

[repo]

Dude I was dreading a similar adventure with my spc arms, every shop I called didnt sound too keen about adjusting them or wanted to charge extra. When I took it in I gave the guy a printout of the spc doc with alignment info highlighted and left a second copy on the passenger seat for good luck. Might have even left the FAQ doc too lol. Overkill aint a word in my dictionary. When I got home I made sure the upper nut was at 150 ft/lb or whatever, and it was.

They didn't seem to have any problem. Used the default procedure from the doc, lower at zero/neutral and adjust upper. Lift is 2.5" front 3.5" rear.

Hopefully you have it sorted out finally!

 

[jross20]

That’s a pretty good alignment at the end. Judging by your before camber I wonder if the previous alignment they didn’t tighten the nuts on the spec ball joint enough. Any changes to camber from a loose nut will change toe and can cause a pull from uneven camber and tire cupping from too much total toe.

Well I thought it was too, but after driving for a bit since then...she still pulls to the right pretty badly. That makes me thing something might be bent...but I can't see any issues at all visually and the rack seems tight (as in no play between the steering wheel or the wheels that I can tell)