Hey, math guys (trig), help out an old carpenter

Zeke · 02-01-2005, 07:29 PM

In an effort to get the thing aligned so I can drive it to the alignment shop and not be too embarrassed, I have set up much of the front and rear using a laser off the face of the rotors.
Now, you ask how can I have the car at ride height and not have any wheels on it? Simple, torsions in front are not hooked up. Rear arms are sitting on 2 jacks (the body is still safely supported).

So, with every thing uptight and out of sight, I have established the centerline of the car and shot a laser to a wall over 30 feet away. I shot the rear rotors past the fronts for reference and onto the wall. Centered those at about 0 toe.

But, to tell the truth, the rear suspension is not all the way up to exact ride height. There's a reason and it has to do with how the rest of the car is still supported. I'll have to wait on that one until the car is actually on the ground to double check the camber and toe. If I thought I could get the rear torsions out and back in exactly the same way, I might have been able to set up the rear "dry" like I'm doing the front. Lot of work; don't have that kind of time at this point.

However, I shoud be able to hit the front pretty good because I know where I want my A-arms to be at rest and they are there now.

At the wall, 32 feet from the hubs, I have 5 inches on toe-in on each side for a total of 10 inches. Using trig, what is my toe? If I had to get out my books and do this, I won't make the AllEuroswap this weekend, I'd still be doing the math, LOL.

Oh, one more question for you alignment gurus, as the rear suspension compresses, what is the effect on rear toe? Gain toe-in or gain toe-out?

Chuck Moreland · 02-01-2005, 07:35 PM

If I understand correctly, you have a right triangle with one leg 5 inches, the other 32 feet. The acute angle is then .746 degrees.

As the rear compresses, it toes in.

masraum · 02-01-2005, 07:36 PM

.746* per side, I believe

masraum · 02-01-2005, 07:36 PM

Damn, too slow

Zeke · 02-01-2005, 07:44 PM

OK, if we are doing degrees, what is the spec I'm shooting for? Inch wise, I would be happy with 1/16th toe-in measured at the tire tread. Can't translate that.

Chuck Moreland · 02-01-2005, 07:52 PM

Assuming a 25 inch tire diameter, a 1/16 inch difference is a .14 degree toe in. If you're just driving to the alignment shop though, why not just make it easy and set 0 toe.

Zeke · 08:13 PM

Quote:

Originally posted by Chuck Moreland
Assuming a 25 inch tire diameter, a 1/16 inch difference is a .14 degree toe in. If you're just driving to the alignment shop though, why not just make it easy and set 0 toe.

Good idea. However, I might drive the car some while I'm waiting for someone to make some offet BJ's

. I don't really want to pay to have the thing aligned twice.

I thought it might be a little more predictable with a bit of toe-in on these damn scored lines on the freeways.

Thanks for the math help. You and Mas make it look as easy as I can make hanging a door look.

Oh, BTW folks, those Elephant polybronze gizmos sure look nice reflecting the moonlight as I slash and burn to get this thing on the road. I think I remember Chuck going thru the same scenario. He heh.

masraum · 02-01-2005, 08:10 PM

Cool, I need to replace my front door!

Zeke · 02-01-2005, 08:14 PM

Quote:

Originally posted by masraum
Cool, I need to replace my front door!

Send me your house and I'll do it.

thabaer · thabaer's Garage

hold on, wait a minute....Chuck and Steve are blowing imprecise data up your ummmm... ( darn voodoo witch doctors! )

You'd better get out a transit and your solar ephemeris, then do a sunshot tomorrow. Might as well shoot polaris tonight while you're at it....

We used to beat junior chainmen with a stadia rod for results like that, it's really .745997 deg.

There's an old-timer curmudgeon on the 200q20vt list who's written up a low-cost but good DIY alignment procedure. PM me if you guys are interested, I think I can find a copy.

thabaer · thabaer's Garage

32 feet!! I have a sudden case of garage envy.

masraum · 02-01-2005, 08:35 PM

Zeke, It's in the mail, hopefully UPS will pick up tomorrow. Shipping was pricey, but I've seen your work, it'll be worth it.

good self alignment thread

Toe Adjust Techniquest

And Windows XP says

0.74605987818253310977060482416115

and my trusty HP 32S RPN agrees

might wanna check your abacus

masraum · 02-01-2005, 08:37 PM

Yeah, 32 feet is nice, but he didn't mention that it's only 4 wide and he's gotta get his car on 2 wheels to get it in the thing.

Zeke · 02-01-2005, 08:44 PM

Quote:

Originally posted by thabaer
32 feet!! I have a sudden case of garage envy.

Not to worry, I work ouside under carport. The wall of the house is 32 feet in front of the car.

I just came back inside after dailing it in to just inside 0 on my markers. I can see that laser beam well at night. I didn't want to be looking for that sucker in the daylight. So, tires go on tomorow.

I wonder if it will run after 7 months.

I'm gonna start a new thread about this work.

masraum · 02-01-2005, 09:02 PM

BTW, 1 inch instead of 5 would give you ~1/16" toe

Zeke · 02-01-2005, 09:23 PM

Quote:

Originally posted by masraum
BTW, 1 inch instead of 5 would give you ~1/16" toe

I just got in from outside, all set up still, so it took 5-6 minutes to swing them out to what probably is a 32nd each side. Wheel is still centered, hope it drives that way.

I'm jamming those adjusters in there first thing tomorrow and gonna mount some wheels and drop it on the ground for the first time in 7 months. It has seemed like 2 years.

Wil Ferch · 06:42 AM

Smart Racing Products web site has a nice graph that shows toe-in ( in minutes or degrees)...correlated to overall tire diameter.

Be careful how you use the table...it shows up twice on their web site...and it implies *total* toe in one case....and *toe-per-side* in another case...you can easily get a 100% error if you don't follow what's going on.

With that one caveat....nice graph, though !!!

Wil

EDIT: see here...

http://www.smartracingproducts.com/pdfdocs/toe_settings.pdf

masraum · 02-02-2005, 07:16 AM

Milt/Zeke,

That's GREAT news. You've put enough blood, sweat, and tears into this one. I hope it drives better than new.

Oh, and we want more pictures. Some where you haven't had to swiss cheese the thing.

thabaer · thabaer's Garage

Yeah, pics!

Quote:

Originally posted by masraum
And Windows XP says

0.74605987818253310977060482416115

and my trusty HP 32S RPN agrees

might wanna check your abacus

You naughty sine-boy, and here I thought the adjacent side was the one perpendicular to the wall

Now about believing anything XP tells you....although my 48SX agrees with your 32S if I go hypotenuse ( I think windoze peeked at your HP's answer! )

Good alignment thread link, should have realized that there would already be one in the tech notes here but my brain was fried from a day of fighting against errors in the MSDN Library documentation. ( Kill Bill pt. 3 !

)

masraum · 02-02-2005, 09:53 AM

Hahah.

I'm no huge fan of M$, but they did pretty good with XP all things considered. I work on routers, switches, network stuff, etc..., try to not have to do anything with M$ as part of my job, and only mildly tinker at home. People that work with Microsoft stuff are probably into S&M, and programmers and just weird