Product Review - Dial Calipers

Contemplating the 'product of the month' to review this month I found myself with a lot of choices. Should I do a review on a Difalco Fanatic controller? Maybe I do a review on a certain type of pinion gear. Some people might like to read about the Pro Slot PS 4002 FK motor. I was having this conversation with another person and they mentioned an intriguing idea. I will not mention this person's name here as I don't want to give them the credit. Plus, I believe he is suffering from dementia and would not remember suggesting it anyway. So, I take full credit...or blame...for the idea of the topic this month.

This month I will be writing about an underused tool and one that some people probably don't even think about. It is cheap in cost and available almost everywhere. I am talking about a dial caliper. That is right, a dial caliper! How many pit boxes can you look in at a slot car track and not find any measuring device at all except for a test plate to measure ground clearance, wheel base width, and maybe a go/no go gauge for tire diameter? For those who have not thought about this, a larger question stands before us...Why should we have a dial caliper in our box? Now, if you are an impatient person and want to get to the main use of this product and forgo my clever writing, my wit, and my insults to my brother, you can drop down to paragraph number 6. Understand, you will be giving up on some of my valuable insights on the caliper, other uses of the caliper, and the baking of a fudge brownie apple pie on top of an over-heated Hawk 7 motor.

A long time ago when I was riding dirt bikes I would always carry a pair of vice grip pliers, some baling wire, a screwdriver with interchangeable tips, some zip ties, and a roll of duct tape. With these few tools you can do an enormous amount of repairs. Maybe it wasn't a great tool kit, but it would get you off the trail most of the time. It took up very little room and it was light. In slot car racing we have limited space in our pit boxes. Let's be honest. We can't carry everything with us. We carry what we think we may need and some other luxuries based upon how much space we have available. Sometimes we need a tool that can do many jobs. One that takes up little space and gives great benefit. That is exactly what a dial caliper does.

Before we start looking at what a dial caliper can do for a slot car, let's look at what its basic functions are. A dial caliper can come with a dial with a hand that sweeps around or a digital version. The digital version allows for easy resetting of the dial to zero and it can swap from inches to metric use with a quick push of a button. Basically, the dial caliper is a pair of jaws on an extended handle. It measures the distance between the jaws as you slide the bottom jaw of the caliper down the handle. This handle can be in many different lengths. They can be 6” calipers, 10” calipers, 12” calipers, and even longer; it is all based on how long the stick is. The stick will usually have measurements marked on it like a ruler, so you have a ruler in your box also. The jaws on the dial caliper can be used to measure outside measurements and it can be used to measure inside measurements.

If you know the maximum width your tires can be, a simple measurement with the dial caliper tells you if you are in compliance. Not only does this tell you if you are in compliance, but it also tells you how much over you are or how much under you are. This means you know how much you need to adjust and not just go with trial and error. This can help you with your body height. Some classes have a rule with a maximum height for the body. You simply put the car on a test block and put the stick on the test block next to your car. You can then read the measurements marked on the stick to see what your body height is. Once again you will know accurately how much you must lower your body or how much you can raise your body.

OK. For those who were too impatient to spend time with the rest of us, this is paragraph 6. You will forever be looked at as the person who can't cook on a Hawk 7 motor. And it was all because you were impatient. So be it. Here we go. In my not so humble opinion, the greatest use for a dial caliper in a slot car pit box is this: you measure the diameter of your tires with it. Oh sure, you can measure the inside diameter of the hub also, but that is not how the hubs are measured anyway. They are measured and noted with the hub size by the outside diameter, not the inside. The outside diameter is the key. The very basic use is to find a set of tires that barely have you legal for your ground clearance and measure the diameter of these tires. Now you know what size tire is legal and what will be illegal. You can now measure all your tires and see which ones are legal and which ones will not be legal. Now....if you have more than one class you race, the tires to achieve the proper ground clearance may not, and probably will not, be the same. Knowing these numbers for all your cars allows you to use tires on one car until you need to move them to the next car for their size. You can get a lot more use out of your tires this way. Just because they are no longer legal on one car doesn't mean they are illegal on another car.

When you are measuring the diameter of your tires you need to be aware of a coning that can occur on tires. On some tracks, the tires will wear more quickly on the right side of the tire or on the left side of the tire giving the tire a cone shape. The caliper will help you find the tires that are not wearing evenly by measuring the left side and the right side of the tire. It is not uncommon to see the two do not match up. If it is not far out of measurement you might want to rotate the tires and run some practice laps to bring them back to match. Either this, or you can true the tires. There are a lot of different means of doing this, but they will not be discussed here. The article on tire truers was done last month, you can just go back and read that. It is located under Articles, then under Product Reviews.

Here is an example of the tire size use you could be looking at. I have one car that needs 0.750” tires. Once these tires wear down to unacceptable size I can move them to another car that needs 0.710” or larger. After these tires are no longer legal on this car I can put them on a car that can take as small as 0.690”. Once the tires get below that size they can only go on a car for me that will run in a class that does not check the clearance other than making sure nothing is dragging. For each step in this tire's life, it is being used to its ultimate potential. That is, as long as I don't destroy the tire with careless driving. To get this kind of life and use out of a tire you need to understand that a tire will last longer if you do not make the car “chatter” in the turns. At the same time, I can get around the turns faster if I am just under the “chatter” point. The “chattering” of the tires wears on the sides of the tires tremendously. It can also cause chunks to be torn out of the tires. So, if you want your tires to last through many uses they must be taken care of along with using the calipers to see where they can be used. The dial caliper will help you make your tires last longer, be used to their best efficiency, and show you when the tires need to be maintained with truing or rotation.

As far as cooking a fudge brownie apple pie on a Hawk 7 motor....you know it can't be done. But you can find out if someone read the entire article or not because those who jumped ahead to paragraph 6 surely are not still reading at this point. Just smile and tell them the pie was delicious.