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Squaring front and rear end

8K views 17 replies 7 participants last post by  jaw22w 
#1 ·
I am currently building a frame for my 1926 T coupe. I am just now trying to attach the 4 bar brackets for the front dropped axle. The four bars only have an adjustable end on the front of the bars. The rear of the front bars is fixed (urethane bushed). The adjustable end is a 7 degree urethane bushed end, so can only be adjusted one full turn at a time, meaning you can only adjust length in increments 1/18th of an inch (5/8-18 threads). I want the 4 bars to be the same exact length after installation, so caster and square must be set before attaching the bracket to the frame. I am triangulating the front axle for square from a punch mark on the rear crossmember on the chassis centerline. After tacking the brackets to the frame and remeasuring the triangulation, my two dimensions are different by a little more than 1/32". After getting the front axle in the right place I will then measure back from the king pins to square the rear end to the front axle. So the front axle being square is the key to my whole alignment process.
My question is this. Is my front end close enough as is (1/32" off in the triangulation) or do I need to cut the brackets loose and get the front axle perfect? I know I am probably a little anal in my measuring. This is probably a result of years of working on installing precision equipment (robotics), but being very precise has always worked for me. I guess the question really is what kind of tolerances do you guys work with when squaring front and rear ends? Sorry for the length and hope this makes sense. Thanks for any input.
 
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#3 ·
.032 is plenty close. There will be clearance in the bolt holes in the brackets and you can always slot the bolt holes a little bit to get the axle where you want it.
I fixed some brackets years ago for a friend that the bolt holes had worn elongated. Did just enough welding to fill in the holes and then bored new ones.
One trick I am considering on my Model A build is to put some late model "D" washers on the frame plates to allow adjustment. May be something to think about for yours.
Mark
 
#10 ·
Well this is the last custom frame I built... And not one slot had to be made into the frame for suspension adjustment.. NONE... The bars has all the adjustment they need on them WHEN you set EVERYTHING the way it should be done from the start.. When you add slot's to any suspension mounting points your asking for trouble.. You should have a hole and a bolt.. NO SLOT'S NEEDED.. Sorry but that's the right way to build a frame from the start..

Like I said.. This was the last one I built..;)





 

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#6 ·
Actually Astro they have ZERO alignment on most every car made outside of toe. ZERO, you sometimes can shift a sub frame to rob a few tenths of a degree but not every time. Hardly any car these days has any adjustment at all for camber and caster.

Honestly, they aren't often out a 1/4 but they are out a lot more than the 1/32" we are talking about here. The tolerances on most every late model car is 3mm (about an eighth) and the full framed trucks are 6mm.

Brian
 
#7 ·
What I do is to scribe a centerline on the floor and then two lines perpindicular to the center line at the center of the axles. I then have a good reference point to check for square as I am building things. Sorry bout the spelling..

Sam
 
#9 ·
Thanks guys. I thought that the front axle was probably close enough. I just wanted to hear someone else say it.
The amount of expertise available on this board is simply amazing.
Thanks again. Now it is on to setting up the rear end!
 
#14 ·
Has nothing to do with me being the man !!!! Just telling people the truth about how it should really be done.. Everyone has different ways of doing different things,, But slotting your mounting holes on suspension parts isn't the way you want to go.. If you do so,, Your asking for movement you really won't want down the road..:pain: Sorry if you don't understand why..
 
#13 ·
The frame in question is not my first build. I built this one a year ago. It is also 4 bar front and rear. This one had infinitely adjustable bars. This is the reason for my confusion. The new one does not have infinitely adjustable bars, only adjustable in 1/18" increments. The incremental adjustment is what had me confused.
 

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#15 ·
You just want to make sure when setting it up at ride height, it's as close as you can get it.. With adjustment both ways.. Then you should be ok..Good luck.. And sorry for taking this this far,, But people need to know..

Very nice car by the way...
 
#16 ·
alinment

one thing i learned the hard way.. my first bucket was wish bone front and rear.. what a pain to sq it up.. but most likely one and done.. my second bucket i still did wishbone on front and fully adjustable 4 link on rear.. it took maybe 15 minutes to align it.
if i every do another bucket i WILL have 4 link front and rear..
do yourself a favor and do all the alignment before u put the body on so u can square it alot easier.
 
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