This particular Toolshed Engineer article is an update to two previously published stories on tire mounting and balancing titled Tire Preparation Basics and Nitrogen Is Your Friend. It turns out we here at Speed News don’t know everything there is to know in the racing world — of course, it could be argued we don’t know much of anything except where commas go.

But we do make it a point to continually try to learn and improve. The racing community in which we exist is ripe with different ideas and information. Every day I walk through a race paddock I learn something new. After we published the story on tire preparation basics, NASA member Tim Maddox posted a comment on Facebook talking about some painted dots on tires that help with balancing a tire. I had never heard of this before, so we decided to do some research. Google to the rescue!

When you purchase a new tire, you will see a yellow painted dot and a red painted dot on the sidewall. I never paid any attention to these marks. It turns out the dots indicate balancing information for the tire.

According to Yokohama, the yellow mark is used to mount the tire based on weight and the red mark is used to mount the tire according to uniformity. I will let Yokohama explain it to you in its terms below:

Uniformity Method (Red Mark)

“When performing uniformity match-mounting, the red mark on the tire, indicating the point of maximum radial force variation, should be aligned with the wheel assembly’s point of minimum radial runout, which is generally indicated by a colored dot or a notch somewhere on the wheel assembly (consult manufacturer for details).

Radial force variation is the fluctuation in the force that appears in the rotating axis of a tire when a specific load is applied and the tire rotated at a specific speed. It is necessary to minimize radial force variation to ensure trouble-free installation and operation. Not all wheel assemblies indicate the point of minimum radial runout, rendering uniformity match-mounting sometimes impossible. If the point of minimum radial runout is not indicated on a wheel assembly, the weight method of match-mounting should be used.

Weight Method (Yellow Mark)

When performing weight match-mounting, the yellow mark on the tire, indicating the point of lightest weight, should be aligned with the valve stem on the wheel assembly, which represents the heaviest weight point of the wheel assembly. After match-mounting by either of the above methods, the tire/wheel assembly can be balanced.”

The red dot on the tire represents the uniformity mounting point based on the tire’s imperfect round shape (largest radial point) along with the wheel’s imperfect round shape (smallest radial point) if that point on the wheel is known.

Thanks to Yokohama, I had a new understanding of what these marks represent. The concepts for each method for using the painted dots to mount tires made sense to me, however I found some flaws in them during mounting.

First, after careful inspection of my wheels, I did not find a red mark or notch indicating the low radial portion of any of my wheels. Therefore, I couldn’t use the uniformity method to mount my tires. Second, the idea that the valve stem location is the heaviest position on the wheel is an assumption. Valve stems are rubber or aluminum inside a hole in the wheel where there is less material. I’m not positive this is where the heaviest portion of the wheel is. Maybe for cars with TPMS sensors this may be the case, but for our lightweight race wheels, I was less than convinced.

We needed to mount some new donuts, Yokohama ADVAN A052s for our TT5 car. It was the perfect time to test these new mounting theories.

Instead of guessing about these ideas, I went to a guy I trust, Terry Large, at Sanger Tire. Terry has been mounting tires for Double Nickel Nine Motorsports for years. As a professional, Terry was familiar with the painted dots on the tires and he ensures that his technicians line up the yellow dot with the valve stem for the weight method.

I asked Terry if he wouldn’t mind putting the wheel, without a tire, on the balancer to see where the actual light spot would be. He said we could balance the wheel first by adding weights, and then mount the tire and then balance the combination with more weights. I explained to him — like a normal psycho race engineer obsessed with weight and especially rotational mass — that I didn’t want to add any more weight than necessary. I wanted to find a natural balance between the wheel and the tire combination. He said, “The only difference would probably be a couple of ounces.” And my reaction was, “Two ounces! We’ve got to balance each wheel and mark it!”

Hey, 16 ounces is a pound, everyone.

With our bare wheel on the balancer, we found that the heaviest portion of the wheel was not at the valve stem as indicated by the internet. Aha!

Terry dismounted a tire from one of our wheels and put it on the balancer. The balancer stopped and shined a laser beam exactly where it wanted us to add weight to the wheel — the lightest section of the wheel. What we found was this position was not 180 degrees from the valve stem, the purported heaviest section of the wheel. We used this information to mark the wheel at its heaviest portion and then line up the yellow dot on the tire — the lightest portion of the tire — to find a natural balance.

Placing the predetermined heaviest portion of the wheel, from checking the balance of the wheel by itself, along with the yellow dot on the tire — the lightest part of the tire balanced at the manufacturer — left us with an extremely balanced wheel/tire combination that required only two small wheel weights for the perfect union.

Once the tire was mounted onto the wheel with the yellow dot aligned with our mark for the heaviest portion of the wheel, we took that combination and placed it onto the balancer. What we found was good news. This natural balance of the two objects aligned was almost perfectly balanced already. It only required two wheel weights to get the wheel/tire combination to balance. Having mounted a lot of tires on these wheels I can say this was the least amount of wheel weights I had ever seen used. Yay, we made the rotational mass of this car lighter!

Europeans do not use water to lubricate their beads and wheels before mounting a tire. They use a mounting paste instead.

Another criticism to the original story, Tire Preparation Basics, was that I said I didn’t want the tire shop to use a lot of water on the bead or the rim when they mounted my tires. This was to limit moisture being introduced inside the tires. You can’t get this water out, and the oxygen in the water increases pressure fluctuations during track sessions. I was informed by some tire professionals that proper lubrication of the bead is required to ensure no tearing or damage to the bead occur during mounting.

However, they did educate me and say, “You don’t have to use water to lubricate. In fact, in Europe, they use paste instead.” I had no idea. I did some research, and with Amazon to the rescue I had some Bead Don shipped to the shop, and now all of our tires are mounted with bead paste instead of water. Problem solved. Those Europeans, they’re always ahead of us just a little bit, except for smoking. They still think that’s a good idea.

When we purge our tires and fill them with pure nitrogen, I was curious if we were damaging the tire when we allow it to get deformed during the purging process. Good news, the tire pros said we doing it correctly, no damage to the tire.

In the other story I would like to update about mounting tires, Nitrogen Is Your Friend, I wanted to seek some professional advice on our methodology. I had the chance to talk with TJ Tennet, The Tyre Guy, about how we purge our tires of air and replace that air with pure nitrogen. I was worried that our method of sucking all the inner pressure out of the tire deformed the tire so much that we could be damaging the sidewall. The response I received from TJ who was the Director of Competition at Bridgestone for a number of years, was that we were doing it correctly and we were not damaging the tire.

The only criticism he provided was that if we truly wanted to get as much oxygen out as possible, he said we needed to complete three cycles of evacuating the tire, filling it, and then evacuating it again. That was good news. Not only were we doing it correctly, but he also wanted us to do it correctly three times. The point of this process is to evacuate any moisture from inside the tire.

With our new tires mounted, balanced, purged, marked and bagged up, it was time to fill up the hatchback and head to the next track day.

The good news is the information we provided in the two previous Toolshed Engineer columns was not completely wrong. However, we were able to update a few things we have learned over the years to improve the information provided to each of you. In racing, if you aren’t improving, you are moving backward. Now it is your turn to go be a pain in the rump at your local tire shop. They love balancing wheels and then balancing them again. Good times!

With some fresh donuts mounted using some new upgraded information (better balance, bead paste, nitrogen purging, etc.) our fleet of Ford Fiesta STs is ready for NASA TT5 this season!

Thanks to readers for your interaction, which helped us here at Speed News update and improve. And massive thanks to Terry Large at Sanger Tire for letting us play with the tire machines!

Image courtesy of Rob Krider

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