Checking toe-out

[trmiv]

I need a little help with checking toe-out.  Before getting this legends car we had IMCA type modifieds for about 6 years, so I'm familiar with the concept of checking/setting toe-out (we used either toe plates or a toe stick with a line scribed in the tire), but I've never done it with a rack and pinion setup.  We're just getting around to running a couple of races, so we're trying to get the car ready.  Our car came with some setup books that have descriptions of checking toe, but it's not a method I've ever used, so I'm not sure we're doing it right.  Basically the instructions say to set the steering wheel at 12 and clamp the steering in place.  Then run a string along the left side connected to both bumpers.  Then to adjust the toe until the string touches both sides of the front tire.  It says when it touches both sides, your toe-out is set correctly.  Well what is set correctly by this?  1/8"?  1/16"?  What is the toe actually at?  The car also came with a toe stick like device that uses the outside of the tires (dobbins quick check?  Can't find much info on it online).  After we set the toe with this string, we checked it with this device and it shows the toe being somewhere over an inch! 

So basically I'm asking, how should we be checking the toe on these cars?  Since it's a rack, does it need to be checked/adjusted on both sides?

[John_Schwemler]

I think you might be over thinking this a little bit.

It's nice to have the rack centered and have the wheels "straight" before adjusting your toe, but not 100% necessary.

Otherwise, I would tend to say that adjusting the toe and measuring it will be the same as the IMCA car.  Use your toeplates/toe bar/whatever to find out what the toe is and adjust it using the outer tie rod ends.  If I remember correctly, your toe out should be between 1/32nd and 1/4", obviously depending on track, frontend geometry, ackerman, etc. 

How we do it during our setup nights is... 
At the start of the season we "center" the rack and adjust the tierod ends so that they are equal.
We always square the RF to the RR using the string method.
We adjust the LF for the toe amount we're looking for.

Once in awhile (a wreck, significant change in toe) we will recenter the rack and double check that the RF is still square w/ the RR

[legends13]

center the steering wheel on the rack. to do this, turn the wheel from lock to lock, and make sure it travels the same amount in each direction. Basically, the wheel should turn 270 degres in either direction from center. Once you have this done and set, run a string from LR to LF bumper. Adjust like you said above, until the string just touches the front and rear of the LF tire. Now, your LF and LR are aligned with the steering wheel at dead center. Using a second string, run it down the right side in the same manner. adjust the RF for your desired toe out. Usually between 1/16 and 3/16 is good for me.

toe plates or stick will work, but I prefer good old string. for me it is easier, and quicker.

[thunder938]

Most check it with the wheelbase go / no go bar.  Takes 2 minutes and done.

[legends13]

I don't even use the wheelbase gauge for wheelbase....

I use strings for that too. I find the gauge to be only good for tech. But if it works for you, and you do it the same every time (which is the most important thing), it is probably ok.

[Bigmil]

I too am learning these fancy ways to measure  toe and I am hearing to different concepts here.

1.  Square the right sides (RF/RR) and then adjust your toe out on the LF.

or

2.  Square the left sides (LF/LR) and then adjust your toe out(or in?) on the RF.

It seems to me that you would want to do method 1 becuase if we are turning left your left wheel has a smaller radius to turn than your right wheel.

Whats the consensus?

Also, I am glad someone finally explained the string method as I do not have toe plates, a gauge bar, or anything fancier than string in my current budget.  Plus I have been running all season without knowing my toe (or cater/camber for that matter).  I know, pretty pathetic for a guy with an automotive engineering degree, but it was either wait 2 months to start racing with the proper gauges or get racing sooner and try to buy them in the off season.

Gerad

[trmiv]

Method 1 seems like the right one to me as well.   We did string the right as well, and lined that side up, and then we lined up the left like the setup sheet said. So likely our toe is straight up right now.  I'll have to set it later this week.  It seems you need a decent ruler without a clip on the end like tape measures have to be able to see the measurement between the string and tire with any sort of accuracy. 

[justfreaky]

Center the steering.
Take a piece of string and have someone hold it at the rear of the car to cross the center of the rear wheel. Pull it across the front wheel on the right side and make sure the front wheel touches the string both front and rear. This sets your baseline straight ahead. Now place the string on the left side. When the string touches the front tire, which should be front side first, the distance between the string and the rear side will be your toe out, if it touches the rear first, you are toed in.

[IraceLegends77]

Yea what Steve said but get yourself a hook on your string and come off the rear bumper and you can do it all yourself. I have no help so you have to get creative.

Scott

[John_Schwemler]

Steve's way of measuring the toe off the LF after the right side is square works too...  measuring the toe off the rear of the tire for toe out...  rulers do work better than measuring tape for that style of measurement.  

You can also make yourself a toe bar, which from the sounds of things you may already have.

With the toe bar we measure across the front of the tires first, adjusting a bolt (about 1/4" or 3/8") until the bolt hits the tire.  We then move the bar so it measures across the rear of the tires and measure the space between the bolt and the tire.  Essentially doing the same as Steve described but I believe more accurately.

Our LF doesn't tend to be as inline w/ our LR as the two right side tires are w/ each other.  Therefore I don't believe measuring the toe using the string method to be AS accurate as w/ toe plates or a toe bar.  It is a quick and easy way to check for a problem while at the track, and we have used it as such many times.

Wish I had a toe bar and a car here to show you guys what I mean through pictures.

[justfreaky]

Here is a link to plans on how to build one.
http://www.thedirtforum.com/tool2.jpg

Steve

[legends13]

Either way will work. I always set toe on the RF, as that is what I was taught by Clay. I do not "line up" either side. It is unnecessary. As long as you have the rear end square, (which is another topic, but I have always, and will always, run it square) then using the string on one side or another to find straight ahead will work. Just do it the same everytime. the outside of the tires don't have to be even, just straight.

As for a ruler, what works the best that I have found, is an old tape measure, that you cut a 2 inch piece out of. Using a razor (utility knife) just score it lightly on the inch mark (what ever "inch" you choose) and then bend and snap it. you will have a perfect straight line, with very readable measurements.

[John_Schwemler]

Cool tech tip, on the measuring tape.

[Bigmil]

So can you check toes with the car sitting up on jack stands or does it need to be sitting on the ground?

I didn't think there would be any "bump-toe" effect but as a newbie I will be the guy to ask the "less than smart" questions.

Gerad

[John_Schwemler]

You should check the toe while the car is on the ground.  Preferably after you have finished your setup on the car, ie. weights, ride heights, etc.

You are correct in that there is "bump toe" and its actually called bump steer. 

Description is "borrowed" from Steve Smith's Paved Track Stock Car Technology.

"Bump steer is the change in steering angle of the front wheels caused by the front suspension moving up or down through its travel.  Bump steer causes the introduction of toe (either in or out) into the front wheels when the suspension goes into bump or rebound."

There is more in the book, but I'll stop there, there's tons of places to look up more information if you want it.  Bump Steer is important, but has a lesser impact on the car than alot of other adjustable tuning aids on the car.  Focus on the basics like squaring the rear end, ride heights, corner weights, proper spring rates, caster, camber, and toe (among others) and develop knowledge on these basics before you put too much investment into changing this.

If you had someone you trusted that could provide chassis consultation and basically walk you through an indepth set up on your car it may help you.  The numbers may not be correct, but if it helps you pick up the adjustments any faster it could save you alot of time and aggravation in the long run.

Otherwise, we'll continue to try and help you here! 
John