Over the years, my racing team has accused me of being a real pain in the ass. This comes from my dedication to extreme attention to detail, no matter how small the task. I believe it is this attention to detail that has helped my team, Double Nickel Nine Motorsports, be successful on the race track. My crew doesn’t agree. They think I’m possibly “on the spectrum” and should seek professional counseling. This all began when I criticized how somebody on the team had a tire mounted and balanced. In my opinion it was all wrong and could cost us a championship. In my crew member’s opinion, he did nothing wrong except do me the favor of rolling a wheel to the tire shop at the track and got a new tire mounted on that wheel. How could it be done wrong? Well, according to me, all kinds of ways! Allow me to explain.
When I have tires mounted on wheels, there is a step-by-step system for success, which I will detail below. Everything a racecar does, it does through the tires interfacing with the roadway, which means tires are the absolute most important thing on a racecar, ergo the tire mounting process is extremely important to ensure there is no chance for failure. Like I said, my team thinks I am a pain in the ass, and so do most tire shops. Here’s why. …
First things first: fresh tires. Every DOT legal tire, just like the Toyo Proxes RR spec racing tire, comes with a Department of Transportation code stamped onto the sidewall, on only one side of the tire. The last four numbers of the code is the week and the year the tire was manufactured. For instance the code 1518 is a tire that was created the 15th week of 2018, around April of 2018. A tire with the code 5019 is a tire that was manufactured the 50th week of 2019, December of 2019. The newer tire is fresh, where the other has been sitting in a warehouse for a year and a half in the cold and in the heat, with tires stacked on top of it and who knows what. I prefer the freshest tire for the softest rubber. I go through the stacks myself and pick the best tire in the bunch. I don’t let the tire shop select the easiest tire to grab, which could be the oldest.
Before I take my race wheel to the tire shop I take the time to remove the old wheel weights and then clean the entire wheel with Simple Green. Why? I have seen tire shops leave old wheel weights on the wheel and then add more. I’m not looking for more rotational mass, I’m looking for less. I also have seen tire shops just stick new wheel weights on top of brake dust covered rims, where there is no chance the weights will stick very well under high-speed rotation. I clean the wheels myself, thoroughly, because the poor guy busting tires all day long doesn’t have time to do it the way I would prefer it. This is also a great time to inspect the wheel for any cracks.
When I am at the tire shop, I ask the guys to use as little to no water on the edge of the rim as possible. I don’t want to have any water inside the wheel once it is mounted. I don’t want the tire slipping around the rim and water has oxygen in it and I want the ratio for oxygen to nitrogen to be higher. I’ll explain more on that later. If not asked not to, tire shops will slop water on the rim for ease of mounting. I understand they want to make their jobs on the tire machine easier, but I’m not looking for their ease of a workday. I’m looking for the best mounted tire I can get for my racecar. Also, the ambient temperature needs to be above 68 degrees before mounting a tire. I’m not joking here. Cold tires can be damaged during mounting. The tires need to be in at least 68 degrees for 24 hours if they were in an area where they reached freezing temperatures just prior to mounting.
As the tire shop goes to balance the tire, if I see they are adding an unreasonable amount of wheel weights to balance the wheel, I ask that they unmount the tire and remount it 180 degrees opposite to try to naturally balance the wheel/tire combination with less weights. I want the wheel as light as possible.
Once the wheel weights are added to the clean rim, I cover those wheel weights with adhesive aluminum tape to ensure the wheel weights don’t fly off the car during a race. The adhesive on wheel weights can’t be trusted in my opinion. I’ve seen tire shops use duct tape for this process, however, duct tape doesn’t hold up to the high temperatures from brakes, whereas the aluminum tape is less affected.
Tire shops will drop in whatever valve stem is close to the tire machine. They don’t care if it is used, old, long, short, whatever. As long as it goes into the wheel, they will use it. I actually have opinions about valve stems and which ones should be used for which application. For road racing, I prefer to use a short aluminum valve stem, which is bolted to the rim. This makes for checking pressures easy and is durable. I always ensure the valve stem is short enough that it can’t be struck by another car’s wheel while battling on track. For autocross, where there is a high propensity where a rotating tire will strike a cone, I prefer a short rubber valve stem which can take the abuse of striking a cone without breaking. An aluminum valve stem can break from cone contact causing rapid air loss, which is bad. Plan ahead. Know what valve stem you want and bring them yourself to the tire shop to be installed so you know what you are getting. With metal valve stems, I prefer to install them myself so I can verify the torque of the double nuts that hold the stem to the rim. I don’t want to leave anything to chance.
We evacuate all of the oxygen, which expands from heat, from our tires and replace it with pure nitrogen. The full story is here: https://nasaspeed.news/toolshed-engineer/nitrogen-is-your-friend/. We do this for consistency of air pressure during a race. Each of our wheel/tire combinations goes through this process before they are installed on our racecars. This is another reason we don’t want water used when mounting the tires. Water has oxygen inside it and water is difficult if not impossible to remove from the inside of the tire once it is mounted.
Once I have a clean uncracked rim, a fresh tire mounted at above 68 degrees Fahrenheit using no water, balanced with the least amount of wheel weights as possible, and purged of oxygen/filled with nitrogen, wheel weights taped in aluminum, then I overfill the tire with nitrogen and let it sit for a while. I check the pressure to see if there are any leaks at the valve stem, the valve core, an unseen crack in the rim or a bad bead. If the tire hasn’t lost any pressure in an hour it should be good.
As the tire is being pressure-tested I take the time to number and label each tire using a tire marker. This allows me to track the life of a tire and where it has been located on the racecar.
When you have numerous racecars on one team, you quickly realize how important it is to track tires so you can know how many laps and/or heat cycles they have endured. I mark the position the tire will be mounted on the vehicle, as in RF for right front. I will also mark that the tire is filled with nitrogen so nobody inadvertently adds air to the tire without using the nitrogen tank to keep things pure inside the tire. Then I will number the tire. This individualized number can be anything you prefer as long as it means something to you that you can track in the future for statistical data.
Then the final thing to do is to enter the newly mounted tire into the team’s tire database system. I use Excel to track all of the team’s tires and their life and laps on our cars. This helps me to know which tires in our arsenal are the freshest for the big important races, like the NASA National Championships.
So, as you can see, we don’t simply just mount a tire onto a rim on my racing team. It is quite a process, one my team thinks is a bit insane. You be the judge. Add these things to your mounting protocols or call me an insane person. Your choice, but choose wisely.
Rob Krider is a NASA Honda Challenge 4 National Champion and the author of the novel, Cadet Blues.
I didn’t know about the water and 68* mounting. I’ll add to what you do. After every race, I rotated my tires. After a race weekend, I’d wash the rims and tires and check for any damage. If there is no rotational direction, I’d pull the tire from the rim and put them on in the opposite direction to get the most wear. I never had any problem doing this. I’d keep track of the heat cycles by marking the actual tire with a tire pen. The top guys in our group were getting 14-18 heat cycles before the lap time started to fall a bit. Being a mid pack guy and trying to save a buck, I ran mine much longer. I once got 32 cycles out of a set. On the 33rd cycle they started to cord. I always hated doing tires but at $200 a pop, it’s worth treating them better to get more life out of them especially if your on a tight budget!
After mounting and balancing, we put a straight line from the tire to the wheel. After the first session wee check the line to see if it still lines up. If it doesn’t, that means the tire spun on the wheel (due to mounting lube). If so we take it back for a rebalance.
You need some lube to mount the tire, otherwise you risk creating unseen damage to the tire bead. Also, the colored lines and dots on the tire from the manufacturer are important to determining how to match the lighter position of the tire to the heavier side of the wheel (neither are every perfectly balanced) to optimize balance before you ever use weights – too much to explain, just google it. It will save you that 180 spin job to minimize your weights.
What paint pen do you use?
I submit that it’s not the oxygen in air that’s the problem with filling your tires with air, it’s the water vapor (and no, it’s not because it has that oxygen hanging onto it). At the temperatures and pressures in car tires, both oxygen and nitrogen behave as essentially perfect (ideal) gases (and their non-idealities are opposite to each other, so they partially cancel each other out). Water, however, does not. If you have a little surface layer of water condensed on the inside surface of your tire when it’s cold, when the tire warms the water will turn to gas and change the pressure significantly.
That jives with your experience that using as little water as possible when mounting produces the best results, and that pumping out the air helps (because not only do you remove the water vapor in the air but the partial vacuum helps evaporate any of the remaining liquid water inside the tire). I suspect if you follow both of those recommendations and then simply fill the tire with dry air, your results will be indistinguishable from filling with nitrogen.
You don’t balance track wheels/tyres, it’s pointless. You line the Dot (light part of the tyre) on the tyre with the valve steam and leave it, after a hard track session you will see the tyre has moved on the rim.