Follow along as my boys and...
Follow along as my boys and I align our RCR40 Mk I in the garage and get it ready for some quality track time or grocery getting.
If you've been following the build of this car, then you know that we're almost finished with our street or race RCR40 Mk I. The idea behind this series of articles was to document the build of a streetable yet extremely competitive open track GT40 from Race Car Replicas (RCR). We finished a great race engine that runs on pump gas, and we completed some necessary chassis setup by calculating spring rates and evaluating our bumpsteer.
The next step for our GT40 is to step into the mystical world of wheel alignment. Sure, it would be easy to just take our specs to the alignment shop and let the lasers and computers dial us in, but where is the fun in that? I have seen racers on TV using strings and common garage tools to make alignment adjustments, but I never understood the science behind it. So I decided to pay another visit to Mike and Joe at Cooksey Racing.
After Joe explained how the garage alignment is done, I realized this was going to be a job that I'd need my whole pit crew to successfully complete. So, I got on the intercom and "asked" my boys to turn off the TV and meet me in the "Cobra Lounge." Dylan and Reed might only be 10 and 8 years old, but they are really pretty handy. Spending time with the boys in the garage is what it's really all about, but I digress
To begin the alignment process, we needed to find a flat, clean garage floor. Next, we needed to double-check our ride height front and rear to make sure it's sitting in the correct position because this could throw our numbers off. We had the car professionally aligned and weighed earlier this year, so we'll put the RCR40 back to those specs.
Here are the specs we're setting...
Here are the specs we're setting the chassis to. The RCR40 will be set up for a 200-pound driver and 11 gallons of fuel.
When it comes to "stringing" a car, the key to accuracy is finding two points that form a line on one side of the car, perpendicular to the axles. This is usually along the framerail, one in the front, and one in the back along either side. From these two points we'll derive the entire toe-in or toe-out measurements. We'll measure out from those points an equal distance using some homemade tools and set our first string up along one side of the car. Once the first string is stretched, you will need to set up a second string along the other side of the car. These strings need to run parallel to each other, so just take a few measurements and square it up. When you get this far, you're ready to start your alignment process with caster, then toe-in or -out measurements and, finally, camber. When we're all done, we'll need to go back and check all three one more time.
If you remember back to the last article, we experienced a little toe-out as the front end goes into a bump. We want to make sure that if we have a toe-out bumpsteer, then we need to set the static toe to a slight toe-out position. It is important to never cross from toe-in to toe-out or vice versa. That will create instability at speed and under hard braking. This is an example of why it is so important to check bumpsteer before you have your car aligned. I've always assumed that a little toe-in is best, but that's not the case in all situations. On a car with an independent rear suspension this will also apply.
One of the most useful chassis tools I have is my caster/camber gauge. They can be purchased from most racing supply shops. This one came from www.HRPWorld.com. Simply place it on your rim and you can quickly gauge the amount of camber you already have. Caster can be measured a few different ways. Caster is the amount of angle we allow our spindles to "lean back." On some cars with custom spindles you can get lucky if the spindle has a flat side that is naturally perpendicular to the ground. In that case just lay your angle finder on that side for an accurate measurement. If you don't have a flat, perpendicular side, then you will have to use your caster/camber gauge. Caster is measured by noting the wheel camber at 20 degrees to the left and 20 degrees to the right. Fortunately, the RCR GT40 has billet aftermarket spindles that give us a nice flat edge to measure from in order to set our caster.
Now that we've gone through the process of stringing our car to set the toe, checking the caster and adjusting the camber, we are ready for a test-and-tune day at the track. Remember that this is a preliminary alignment, just like any other alignment done at home or at the fanciest shop. The reason I say "preliminary" is because the only way to test the accuracy of your alignment is to take your tire temperatures after a few hot laps. In the final installment we will take the car to a track and make our final engine and chassis adjustments. If the engine runs smoothly and the tires have a nice even heat range across all tires, and if the car brakes and turns smoothly, then we are set! It's never that easy, but I think we are very close. We can then make all the final adjustments at the track. We'll be able to adjust our sway bars, set our shock damping and rebound, balance our brake bias front to rear, and check our alignment. Watch for this next article in the upcoming issue.
With a collection of garage...
With a collection of garage tools, some string, and a couple feet sawed off of a scrap 2x4, we are ready to begin our alignment process starting with the toe-in or -out.
We need to build a couple...
We need to build a couple "instruments" to help with the stringing. The points on the framerails we'll be using as a reference are about 4 inches off the ground, so we took two carpenter's squares and drilled a hole in each 4 inches from the corner.
We cut a groove in the lumber...
We cut a groove in the lumber and tapped the square into the slot. Take care to cut the slot in the 2x4 so that it's perpendicular to the wood (perfectly vertical).
We cut two pieces of aluminum...
We cut two pieces of aluminum bar stock to precisely the same length. These will bolt to the carpenter's square and the other end will rest against the framerail.
Everything looks better with...
Everything looks better with spray paint! This is what the final assembly looks like.
Just to double check, measure...
Just to double check, measure from the outer end of the aluminum bar to the back of the carpenter's square. The distance should be exactly the same on both tools. If it is a little off, just hit the longer one with a grinder to even them out.
Finally, slide the newly constructed...
Finally, slide the newly constructed tool under the car with the end of the aluminum bar resting on the framerail. Use a level to make sure your carpenter's square is perpendicular to the floor.
Do the same on the front of...
Do the same on the front of the car and level the square. The outer edge of the carpenter's squares are now both exactly the same distance from our two reference points on the chassis.
Grab a couple of jack stands...
Grab a couple of jack stands and stretch a string from one to the other, then move them into position.
As the string is moved into...
As the string is moved into position, we were careful not to allow the string to push against the square but instead just barely brush against it both front and back. This string is now parallel with the chassis.
Next, we went to the other...
Next, we went to the other side and stretched the string just as it was on the passenger side.
We measured the distance between...
We measured the distance between the strings front and rear to make sure they were precisely the same distance apart and perfectly parallel to each other.
Here is our car with the strings...
Here is our car with the strings in place and ready for alignment.
The first thing we wanted...
The first thing we wanted to check was the caster. On this car it's pretty simple with an angle finder on the spindle. The caster hadn't changed from our previous settings.
The toe was next on the list....
The toe was next on the list. We took a three-foot piece of aluminum angle iron and held it against the wheel at roughly the height of the hub. We put two marks on the aluminum 26.5 inches apart (that's the height of our tire). Then, we measured the distance from the string at the front of the wheel and the rear.
We found that we were slightly...
We found that we were slightly toe-in on the front. So we loosened the jamb nuts on the steering rack and made an adjustment.
We measured again and adjusted...
We measured again and adjusted again, and again, and again. Finally, we were set at 1/16-inch toe-out.
Once we had the frontend set...
Once we had the frontend set where we wanted it, we marked the jamb nuts with a paint pen so we could easily recognize if something was ever out of position. This way we know for sure that it's tight. We went through the same process on the rearend.
Here's a look at our caster/...
Here's a look at our caster/ camber gauge. We've found it to be very useful.
The caster/ camber gauge is...
The caster/ camber gauge is very easy to use. Just set it against the rim and read the level.
In this case, we had -2 degrees...
In this case, we had -2 degrees of camber on the left rear. That was too much.
We loosened the upper arm...
We loosened the upper arm assembly and tightened the arm two turns.
We got it right on the first...
We got it right on the first try! We landed at -1 degree. With our garage alignment work done, we tightened it all down and marked the jamb nut and the tie rod with our paint pen. Now we're ready to hit the track or the streets in RCR40 Supercar style.