Measuring Up

[nolastyankee]

All,
In preparation for our upcoming move, the Rescue Cobra has made amazing progress in the last two weeks. I'll post another Chapter in the next few days. Until then, I am looking for some input...

When we mounted the rear suspension, we measured from the hub centers to fixed points on the frame in an 'X' pattern, then diagonally to the kingpin centers on the front suspension. Both measurements indicated that our rear end was 1/4" out of square with the front end. There is a little slop in the mounting bolts, and unfortunately, we are fully using this slop to our advantage, but are still 1/4" out.

The confusing part here is that when I look at the body, the wheels don't sit centered in the wheel wells...But in the opposite direction! Said differently, if we were to center up in the wheel wells, the car would be more out of square than it is. Granted, we are not talking a lot here...The wheel is out no more than 1/2" to 3/4" within the well.

So here's my question...Does anyone have any experience lining these things up? I don't want to start reflaring the wheel wells, but I trust our measurements more than the fiberglass. Are we over engineering this thing? (That is certainly likely)

Input?

Unique 9122 - 289 FIA Cobra - The Legendary "Spence" Car

[Poorboy]

Have you checked to see how the front end is in relationship to the frame?

Poorboy

[Brent]

I would align the rearend with the chassis. If the wheel not being centered in the opening bothers you ,you can make those adjustments when you re-mount the body.
I would not align anything off of the body.

brent

[nolastyankee]

Poorboy,
We have tried to check the front end alignment to the frame and it appears to be square. One problem/question we have is what points can be use on the frame as an accurate fixed reference. Suggestions?

So far we have assumed the main tubes to be square and that the motor mounts and point at which the frame angles to both the front and rear suspension to be adequate references.

Unique 9122 - 289 FIA Cobra - The Legendary "Spence" Car

[Poorboy]

I would go to the center of the rear frame crossmember. Use that point and check everything back to it. With the notch cut out you will have clamp a piece of flat stock over it. Also as Brent says square the rear end with the frame.

Poorboy

[K.Wilson]

Nolastyankee,
The measurement you are asking about is probably the single most important measurement in the suspension set up.
You need to establish a "center point" on the most forward cross member of the frame. This can be done simply by measuring the distance between the frame rails at the front cross member and marking the center with a small paint mark, or more accurately, by running a string from the center of the rear cross member to the front cross member then measure from each frame rail to the string at various places along the frame rails to get a "best fit" center location on the front cross member.
Once this center point is established you need to measure from the rear axle flange to the center point you made on the forward cross member, and adjust the rear axle so that both measurements ,left side and right side, are the same (I had to enlarge two of the four differential mounting holes).
This is critical as the rear axle must fit square with the frame or the car will "dog track" as it goes down the road ie. the rear wheels will not follow in the same track as front wheels when viewed from a car directly in front of you.
Then when you install the front suspension you can use the tolerance in the front suspension crossmember bolt holes to make the front suspension line up with the rear. Measure from the rear axle flange to a fixed point on the front suspension, the lower balljoint bolt (mustang type) or the edge of the king pin (MGB type) and make sure the front suspension sits square with the rear suspension ie. the same measurement rear flange to ball joint bolt on each side. This is not as critical as the rear axle but it should be within a 1/16 inch as it will effect the track of the front wheels. There is usually enough clearance in the front suspension crossmember holes to make this adjustment then just tighten the bolts when you get it right, (if there is not enough clearance in the bolt holes they may have to be opened up to get the adjustment you need).
Once you get everything tight check it all again.......
If you have questions please e-mail me.
As I said, this is the most critical part of the set up, easy to do now, difficult to do when the body is on and one of your friends says "it looks like your Cobra is going down the road at an angle, you need to take it in for an alignment".


Keith