Measuring Pickup Points

[SOneThreeCoupe]

Anyone here have a decent method for measuring suspension pickup points without breaking the bank?

I'm thinking about buying four ramps, making them level by adding pieces of wood under them, and measuring from a cramped, uncomfortable position under the car. It'd be cheap, and it'd be miserable... but it'd work.

Alternatively, there are chassis setup stands that are 10" tall specifically made for this function. The cost is relatively high but if there's a group of us in SoCal we could split the cost. I could also just buy them myself and utilize their utility to utilize my suspension's utility, thus justifying the cost through benefit received.

Yes, I'm a little crazy today.

[Wiisass]

What are you trying to do? A full s13 suspension model? Or are you trying to measure a certain thing. Measuring it is easy, it's knowing what to do with all those numbers after. For measureing, you could do it like what you had said, get the car up in the air an equal distance at all 4 corners. Which may actually be the hard part, you can level the car, but will the ground below each of the point be at the same height? You could use one of those Craftsman or whatever laser leveler setups, I don't think they're too expensive and then you would just have to level that relative to the car. And then use that as your ground plane.

And it's going to be hard to get x, y and z measurements for each point when it's on the car. This will be a long process.

What I would do that would make it a lot simpler, but probably more work is measure a lot of the part seperately. Unbolt all the arms and everything outboard of them. Measure the points on the chassis. Get height, longitudinal distance from a given zero and lateral distance from the chassis centerline. Then on a bench measure each of the arms and the spindles and uprights. For the arms, you would just need end to end lenght. For the spindle, you would need x, y and z dimensions. Make sure you determine a good origin otherwise when it comes time to transfer the coordinate system, you aren't screwing it up. And then put everything back together and measure angles of arms. I would then draw each of the parts up in CAD, in whatever reference frame you wanted, except for the chassis points, for those I would use the standard vehicle coordinate system. And then make an assembly out of each seperate CAD drawing. You can constrain the arms at the angle that you measured them and then mate them with the upright/spindle and it should come out pretty close. And then you can define each point in the overall vehicle coordinate system and then put them into a better suspension modeling program.

Simple.

Tim

[SOneThreeCoupe]

Simple sounds like about seven weeks of downtime, $900 in software, and a new alignment. I'd like to have it so that, if need be, I can just jack up the car, pull out whatever stands I have, and drive it within half an hour. My daily has been less reliable than a flood recovery Jaguar, so my "track car" also sees fairly regular street duty.

I'm trying to get my suspension points down so I can actually use my bumpsteer-adjustable bits and not do like I've been doing for the past couple years and just go with "yeah, that looks ok and drives ok."

I'd also like to know if I can reduce the number of spacers on my tie rod ends to take a little stress off them.

[Wiisass]

Get a bumpsteer gauge. There's no point in making a full model and doing all that measuring just to check bumpsteer. It's something that's easily measured directly.

[SOneThreeCoupe]

Sometimes, I wonder why I post mostly incoherent garbage on the internet. I'd have an excuse if that said 5:54AM when I posted it, but instead it was posted in the afternoon by a moron. I apologize for the stupidity.

My main goal isn't to establish bumpsteer but roll center. I have the SPL lower arms and I just eyeballed them to set my height, and I'd like to get them closer than they are currently. The car needs to be sublime.

A bumpsteer gauge is on the list of things that need to be bought.

[Def]

Doesn't seem that hard to put a straightedge from the pivot of the outer balljoint(or equivalent) going to the center of the LCA mounting point, then do a little math and figure out the roll center height, and going from there. Then you should be able to do a little quick math to find out how much you can raise the roll center with a given spacer out at the balljoint(or eqv.).

[ecugrad]

Here is a guy who did what you were originally talking about.

http://farnorthracing.com/modeling.html

[RBbugBITme]

I started doing what that guy did but need to redo it, I couldn't do it all in one sitting and I think my cardboard moved. I was using cardboard and a plumb bob thinger and put pins into each point and wrote the heights next to each pin.
One good thing is that you only have to do one side since its symmetrical.

[SOneThreeCoupe]

I started doing what that guy did but need to redo it, I couldn't do it all in one sitting and I think my cardboard moved. I was using cardboard and a plumb bob thinger and put pins into each point and wrote the heights next to each pin.
One good thing is that you only have to do one side since its symmetrical.

It may be symmetrical. It may not. With adjustable arms, symmetry is relative.

[RBbugBITme]

Not when you're designing a new subframe to change their location.