alignment

I

ITC Mercury

New member
I have been muddling through alligning the front end on my itc rabbit myself. I have had some input about stringlines and boxes of one sort or another from various people but none of them complete and coherent. I would love some guidence on correct procedure for doing the alignment. Thanks in advance.
 
Here's what I sent Erik:

>I'm not sure how other people have told you to do it, but here's how I do
>it:
>
>1. Take 4 jackstands and make a box around the car, with the jackstands
>approx. 72" apart in the front and back.
>
>2. tie a string tautly between the jackstands on the left side and then
>another on the right side jackstands. Now you have the start of your
>"rectangle".
>
>3. Using a tape, make the front and rear jackstands EXACTLY the same
>distance apart. I use 72" because it's easy to remember.
>
>4. Measure from the string to the RF hub. I usually measure to the end of
>the axle in the center of the hub. (Make sure the wheels are pointed
>exactly straight ahead!). Measure the LF the same way. They need to be the
>same (and won't ever be on first attempt). Move the jackstands so that the
>string is the same distance on the LF and RF. Re-measure the distance
>between jackstands and make sure it's 72". This is really hard to do at
>first, but you'll get the hang of it.
>
>5. Go to the back and repeat the process on the rear, I usually measure to
>the dust cap on the rear wheel hub.
>
>6. Measure the front hub/string distances again, they probably moved when
>you changed the rear. Repeat front and rear until the distances are the
>same on the left and right sides of the car. The distance at the front will
>be different than the distance at the rear, that's OK. Mine are usually
>around 4.25" from the string to the end of the axle on the front, and 3" or
>so at the rear.
>
>Once that is done, you've made a perfect rectangle around the car that is
>also centered. It takes me about 5 minutes to do this, I suspect at first
>it will take you a little longer.
>
>To measure front toe:
>
>1. RF wheel: Measure from the string to the side of the tire at the rear of
>the tire. Measure the distance at the front of the tire. Subtract the
>front number from the rear number. If it's POSITIVE, you have that much Toe
>OUT. (the front of the tire is closer to the string than the rear of the
>tire = toe out).
>
>2. Do the same at the LF. If you add the two numbers, you'll get your total
>toe. Sometimes one will have toe OUT (positive difference) and the other
>will have toe IN (negative difference). If the total toe is negative, you
>have toe IN, if it's positive you have toe OUT.
>
>3. I usually shoot to obtain ZERO toe at the front.
>
>If you need to change the front toe, I found that ONE turn of the tie rod =
>1/4" of toe change. Thus, if you want to change the front toe of one wheel
>by say 1/8", turn the tie rod 1/2 a turn. 1/16" = 1/4 turn of tie rod. If
>you don't have an adjustable tie rod on the left side, get one from BSI.
>It's important to have the tie rods the same length from left to right so
>your bumpsteer is symmetrical. I recommend new tie rods if you don't know
>how old they are because they have been known wear out very quickly in IT
>racing. The plastic bushing material that holds the ball and socket
>assembly (at the inner end of the tie rod) together crumbles and can cause
>fluctuating toe-out. If you can't get your toe-out to repeat after each
>race or session, the tie rods are probably worn.
>
>***Note***
>
>There is an easier way to do this at the track on the front. Get two pieces
>of 1"x1" square aluminum tubing from Home Depot, about 24" long each. Mark
>the ends about 1" in from the end with a scribe or marker. With a helper on
>one side, place each piece of tubing on the side of the tire at about rim
>height (2-3" off the ground). Take a tape measure and measure at the front
>and then rear of the bars. The difference is your total toe. This takes
>about a minute to check. Since the steering is self centering, all you
>really care about at the front is total toe. If your tie rods are set to
>the same length (and it's possible to get them different lengths left to
>right by turning the tie rod ends farther on the tie rod on one of them),
>this method is just as good as the string method.
>
>To measure rear toe:
>
>1. Do the same thing you did at the front, measuring the rear of the tire
>first and then the front.
>
>2. I like 1/16" toe IN at each wheel for a total of 1/8" toe in total. I
>use the BSI adjusting shims, get the toe IN I want and try to add about 1/2
>degree of negative camber at the rear.
>
>The aluminum bar method works on the rear as well, but only tells you total
>toe. It's possible to have one side toe-out and the other toe-in but get
>the correct (1/8" total) toe in. This will result in the car crabbing down
>the track and it won't turn in the same on left hand and right hand corners.
>The string method is the best way to make sure each rear tire is properly
>aligned to the chassis.

In case anyone's interested, here was the setup I ran for the last 2.5 yrs on my ITC Scirocco:

Front camber: 2.0 negative
Front toe: 0
Front spring rate: 300#/in
Front shocks: DA Koni, bump 3-5 clicks from full soft, rebound 3/4 to 1 turn from full stiff.

Rear camber: 1.5 negative
Rear toe: 1/16" toe-in on each wheel, 1/8" total
Rear Spring rate: 300#/in
Rear bar: 1" OPM bar
Rear shock: SA Koni, rebound 1 turn from full soft.
Ride height: Side body crease equal height to top of rim. This was about 4.75" to center of front inner pivot bolt w/ 225/45-13 Hoosiers.

With this setup, a FF gearbox w/ stock R&P (3.89 and NEVER used 5th) and a home-built motor, it was good enough for 2:29's at VIR, 2:00's at CMP, 1:35's at Summit (admittedly my worst track), 1:28's at Roebling.

I didn't have a lot of $$$ in the car, I just tried to drive the snot out of it!

MC
 
For a faster,more accurate "BOX", take two 2x4s or 1x2" BY 80" LONG. MEASURE THE WIDTH OF YOUR CAR, ADD 8". Now take both pieces off wood, clamp next to each other in a vice. hack saw slots at the distance you figured for the width +8".
Now you have two equal distance string holders. Place these on jack stands on the ends of the car so that the string will go by the hubs.next to the car , equal distance from the hubs,X4.
Now you have a quick and easy to measure from "box"
I take a alluminum rod and bend it so that it has 8" of ends, bent the same way, like a sway bar. tape a spot on the tires so that uou can mark on it. Mark the scrib point from the toe bar, roll the tire over to the other side and measure that side and figure toe.
I run 1/8" out front, 3.5* camber
3/16"out rear 1.5-2* camber
400-300, (A1) 550/450 (A2)
 
PS. If you can get to figuring in MM,it goes faster than inches. And Mark you are right about the rear toe. Total toe counts . but just shimming one side out makes a big difference both ways!! Also at Summit, if the car goes to the right looser than to the left that will be good for the turn three sweeper that likes a tight car and the rest that needs it loose.
If the car is rear steering, a lot of things happen, like the rear tire is out farther from the apex, this trnsfers less # to the left front, Good thing. Goes faster.
You can use less rear spring for the same turn in rotation, more total rear grip, good thing. Zero srub is about 1/8 toe out at 2* camber. Zero scrub is when the camber lean and the toe combine to roll the easiest , goe faster.
You can make the car loose one way and tight the other. Useful at WGI and Sebring.
Need it loose to the left and tighter to the right. (But still loose enoyugh to plant it and not lift)
.03$ MM
 
Originally posted by racer14itc:
There is an easier way to do this at the track on the front. Get two pieces of 1"x1" square aluminum tubing from Home Depot...
Click to expand...


Another option extends the bar idea. Get 2 pieces of straight, square tube long enough to lay against the wheels (front and rear) and extend beyond the bumpers about 2 feet. While at the 'Depot, buy a couple of cheap, bent 3/8" eyebolts (not welded closed) about 4" long and some wing nuts and washers.

When you get home, cut 90* off of the eyebolts to turn them into hooks. Drill your tubes so that the new hooks can snag behind the wheel spokes to hold the bars (eliminating need for any friends at the track - always seemed to be a problem for me).

Mark the other end of the bars with arrows or triangles or lines that are the same distance apart as your tire outside diameters, color-coded if you have more than one size. When you hook your bars on the tires, avoid raised letters and rest the protruding ends on jackstands. When you measure the distance between the left and right front marks, and left and right rear marks on your tubes, the difference is your toe measurement. This assumes that you use the correct OD measurement on your bars and go inside-to-inside (or whatever) for both measurments. Yes, I know that the actual track measured out at the ends of the bars is different but their differences are not.

Paint your trammel bars an obvious color so nobody cuts them up to make window net mounts or something!

Kirk
 
I've been meaning to get some long aluminum bars to speed up my string set-up process.

Also, I'd just like to point out that I'm not an advocate of toe-out on the rear for a novice driver. That makes the car really twitchy and uncomfortable, not the easiest platform for a new driver to learn and develop on. As they get more comfortable with the car, reducing the toe-in might make the car easier to rotate. That being said, I always stuck with the toe-in on the rear.

I also didn't like a ton of camber on the front as it resulted in excessive tire wear on the inside edges. It might be a tick faster but not worth it in my book. Maybe for one race (ARRC or something like that).

Everyone has their setup for the car, and I was reluctant to post mine for fear of everyone else chiming in and confusing the issue. All I can say is that my setup fit my driving style (or is that my driving style fit the setup?
biggrin.gif
).

I found the real key to getting my car to handle well was the shocks. Going from Tokicos to Konis resulted in a 1 second a lap improvement, once dialed in, with no other changes.

On a related topic, the type of limited slip used can affect the alignment slightly. I used a VWMS limited slip on my ITC car. I never ran a Quaife on it so I don't know how that might change the optimum setup.

Talking about gearboxes, I see a lot of people wasting money on expensive R&P's in ITC VW's, especially since the 5th gears are so fragile and not designed to carry the loads. If/when I come back and build another ITC VW, I'll build a stock 4-spd box w/ a limited slip and stock R&P (3.89). It's lighter than a 5 spd (by about 15-17 lbs!) getting the weight off the LF where you don't want it, and less rotational inertia. On the tracks down here in the SEDIV like VIR and Roebling, you need a stock R&P so you don't run out of gear.

Hope all of this helps!

MC

[This message has been edited by racer14itc (edited September 06, 2002).]
 
Mark

In order to get the car to track straight, when you set up your strings shouldn't they be equidistant from the centerline connecting the front and rear axels? If the front or rear axel is not perfectly straight, even though the toe is correct, won't you get a crabing effect similar to a car that has been in an accident?

------------------
Tony
ITC #0
 
Good question, Tony. I don't really know.

Related topic: one time after an initial setup of a rear axle, before installing alignment shims, I noticed that the LR was toed-out exactly the same amount the RR was toed-in. Turns out the axle was "cocked" in the chassis just a teeny bit. Once I got it square to the chassis, the toe in was the same left to right...

MC
#14 GP VW Scirocco
 
A crooked rear end is what the roundy type cars some times use to help turn in while keeping the stagger as low as possible.
On my ice racer turned oval car, I ran over 1In toe out ,right rear.
As posted prior, just shimming the driver's side seem to help turn in both ways. ( road race).
I run locked diff and that does take a major setup change, (tighter) and a major driver style change. You cant let off if(when) you make a mistake, just stab the brake and hope it makes it thru. A lot faster tho than any other type of diff i 've tried.
MM
 
I have a "quick and dirty" alignment trick that I use at the track (just to make it look like I'm hardly working
wink.gif

I'll share:

1) Lean a 3/4" tube (jack handle works well) against the RR tire so it's touching rubber top and bottom.

2) Turn steering wheel until front and rear outer sidewalls of LF tire eyeball in line with outermost surface of LR tire (at or near hub-center).

3) Adjust toe on RF until front and rear outer sidewalls of RF tire eyeball in line with outermost surface of 1" tube (at or near hub-center).

4) Set personal best time (or crash).

Note that the above works well on any A1 chassis, as long as the rear axle is straight (leg not bent and stub not bent much). I occasionally use it on newer chassis (A2 and A3 street cars), and the method itself works fine with little or no adjustment (i.e., feels good and no excessive tire wear).
 
You must log in or register to reply here.
Back
Top