Zink Chassis alignment

[BLS]

As I tear down the car to rebuild it I remembered there was something that always bothered me about the alignment. As I recalled it the wheelbase was shorter on one side. So, I clamped a straight bar across the transaxle face and measured to the suspension points. The measurement from the transaxle face to the trailing arm pickup point is the same on both sides. However, from the transaxle face to the front beam is shorter by 1/4 inch on the left side. I do not see any evidence of any bent tubing on that side of the car, everything appears very straight and checks straight against my straightedge as best I can tell. So, I am making the assumption the front beam is not mounted 90 degrees to the centerline. I have checked the caster and it is the same on both sides. The Zink had some built in caster with a bump at the bottom of the tube and I have additional shims of 1/8 inch as well. Since there does not appear to be any bent tubing to pull straight I assume the car was built this way.

I could shim the left front out 1/4 inch to make both sides equal, I think. If anyone has a better idea or thinks the 1/4 is nothing to get concerned with please let me know. I know there is some manufacturing tolerance, but 1/4 inch seems excessive to me.

Pictures show the straightedge clamped to the transaxle face for reference. I leveled the rear of the car and then leveled the straightedge with my angle gauge to make sure I was making good measurements. Anyone see any problem with shimming the beam out on this side?

Picture showing the straightedge clamped to the transaxle face:
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Picture showing the backside of the beam mount. You can see the bottom shim for caster:
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Picture showing the front side of the beam mount:
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[brian]

Barry, it doesn't take much to be off 1/4". It could be a slight bend in the h beam or maybe one of the uprights that the h beam bolts to has been kicked back a bit from inpact. Just shim up the short side but remember you won't need a 1/4" shim since the h-beam will rock back on the opposite side and reduce the overall side to side difference. Usually I find that a shim that is half of the thickness you're off will put you very near to dead on.

When aligning the car after assy. make sure all 4 tires are pointing in the same direction when you set the toe and your wheel base should be right on. It's very easy to misalign the rear resulting in the rear wheels pointing in a different direction than the fronts and causing a difference in wheel base. Never try to correct the wheelbase variance with the rear toe setting. You'll be crooked.

[BLS]

Brian, thanks. Good point about the shim being less than the difference. I hadn't considered that. I'll shim to get it correct before I finish disassembling, then check again when I put all back together. I always had the wheels properly aligned, it was just off in wheelbase.
The beam is straight but the uprights might be off slightly. Since posting I've been checking further and I think the left side upright is off slightly. Maybe I hit something a little harder than I thought...

Thanks again, you are confirming my thinking anyway.

Regards,
Barry

[Ed Womer]

Barry,

Since you have the car that dissasembled you should check to see if the chassis really is square. What you need to do is find the middle of the chassis at the front and then at the back around the rear roll hoop. Using a straight edge or string line you need to check if the front of the frame is square with the centerline of the chassis by putting a square along the center line of the chassis and compare to the front of the frame. I use a large carpenter square that is 24" on one side and 18" on the other. I think you will find that the chassis was made out of square or is bent. Belive me that is not uncomon and I have found more than a few chassis that have that problem. If that is the case you just need to add shims on one side of the beam to square it up.

Measuring from the face of the tranny does not provide you with this info since the tranny might not be in the chassis square to begin with.

If you use the string line around the wheels to do you alignment then that is why you have a short wheel base on one side. If you know the chassis is square then you can measure the distance from the top link pin to the fron of the axle tube to get the car square as you adjust the rear toe.

I did a front motor mount on a Caracal clone for someone many years ago and found out the engine/tranny mounts were actually made off center of the chassis and the engine/tranny were a 1/2" off to the one side.

If the chassis wasn't made in a jig or on a steel table like I use and carefully welded up, the chassis will come out bent or crooked and you will always have alignment problems.

Ed

[BLS]

Thanks Ed. I am going to try and get a centerline to measure with. I have a straight extruded aluminum tube that is 12 ft long I can use if I can just figure out where the center is. I knew it was possible the transaxle/motor might be off, but I think since the measurement to the trailing arm pickup points are identical, it *might* indicate the tranny is square. I'm leaving the tranny in for now as it is the only thing with a centerline I can think to work with. Even that seems to be a challenge. I don't think anything is out far enough to warrant major surgery but I would like to get it as straight and square as possible. As far as the centerline goes, any suggestions for finding a true center? I can measure from the frame sides but there is no gaurantee they are perfect. I'm thinking I should work off the transaxle centerline and square everything to it if possible. If the tranny is square anyway.

Regards,
Barry

[Ed Womer]

Barry,

Since it looks like from your pictures that the car is sitting on jack stands if you raise them up to their highest point you can kinda work from under the car. With belly pan still on it will pose a problem getting the center from the frame to the ends of the pan but it is still doable. Measure from one side of the frame at the front to the other side and mark the middle of the frame on the square tube. You need to do this as accurately as possible and down to a 32nd would do. Then do the same thing at the frame under the rear roll hoop. Don't use the rear of the frame under the tranny because it could be bent behind the roll hoop. Now transfer these marks with a square out to the edge of the aluminum belly pand and you now have a place to attach your straigt edge to from under the chassis. I obtained a 1/4"x6" peice of aluminum 9' long many years ago and I keep it for that reason. Whatever you use it needs to go from your mark at the rear and stick out past the front prefereably 2'. Now put you carpenters square against the straight edge and check to see if the front of the chassis is exactly 90 degrees off of center line.

Accuracy here is really import and most people don't realize this since the front beam if straight bolts to the front of the frame and you can use it to measure everything from it. I recoment the carpenters square since it is large and provides a more acurate measurement becuase of its size but make sure it is square. Even brand new ones are sometimes bent in shipping or poor handeling. I have a set of machinist squares and I use them to check the large square and do all of the small stuff with. If you have an old carpenters square that has been used in construction it might not be as square due to being dropped or misshandled over the years.

If the chassis is square then you are in good shape but if not then you need to shim the beam to get it square. When you make the marks for the center of the chassis and you are comfortable you did them accurately you might want to use a sharp cold chisel and permantely put the marks on the frame. When you have the straight edge attached to the chassis you might want to measure off of it at the mid way between the front and back to check and see if the entire chassis has a bend in it. The early vee's were mostly made of light guage 1" square tubing and it didn't really take much to bend and twist them.

Once the beam is square with the chassis and centered if you are using the string method then alignment is easy to do. I measure the front toe by centering the front wheels by measuring from the split on the shock uprights to the inside of the wheel and then adjusting the toe. Then using a tape measure go from the top link pin to the front of the axle tube to check if the rear is square and then adjust the rear toe. Since I pretty much do everything by myself I just add lead peices in the car to simulate my weight so the car is at ride height before aligning the car.

Another thing about knowing if the chassis is square is if you bend the beam at the track you can shim the bent side to square it up and not change the beam or just live with it. At Sebring last year I had a spindle brake and I went into the tire wall at the exit of one and I didn't think it was that bent and left it and raced all year and didn't fix it until I went to the runoffs.

Ed

[BLS]

Ed,

Thank you for taking the time to explain this. I really appreciate it.

I will have the belly pan off later today as I'm taking the car down to every piece. The belly pan and firewall is all thats left now.

Checking last night it appears as thought the tranny is straight and centered. Close anyway.

I will do it the way you describe and make reference marks for the future. My only real concern was finding the actual centerline. Your method makes sense. I do have a good 12 ft long straightedge and a large square. I also have a smaller machinist square to check with so I'm good there.

Thanks again,
Barry

[BLS]

With the belly pan and firewall removed I have found the transaxle/motor mounts and trailing arm pickup points are square to the centerline. The front is off slightly accounting for the 1/4 inch wheelbase discrepancy. After looking much more closely, the front left beam upright mount is bent slightly, probably from an impact at some point. It's not off much and easy enough to shim it straight. I made an additional 3/16 inch shim for the left side that puts it as near perfect as I can measure it.

Thanks for the help. After so many years I find I am often unsure of myself. Every thing I do seems to remind me of the past and the learning curve is not so steep. I sure wish I had this kind of help back in my early days.

Thanks,
Barry