Tech Tips

"Choosing Tires Wisely"

"Choosing Tires Wisely"

In this newsletter, we are going to discuss tires and try to touch on several different questions that we get asked on a regular basis.

Let’s start with tire selection. First key to tire selection is stagger, we have to decide what we want to run for stagger. For me, I will always run as little stagger as I can get away with and still have the car turn (less stagger keeps your forward driver longer into a run).  I will almost always pick all 4 of my tires with the same chalk marks which will usually give me between 1 1/4"-1 3/4". This is also affected by the type of track you race at. For example, a track with a lot of grip - you can get away with more rear stagger and not give up any in the center; while a track that is hard on tires and no grip - you will want to do all you can to keep rear drive. Next in our tire selection process we need to be aware of what we are running for a differential, meaning a gleason or G-9 differential will require less stagger than a Detroit locker or spool.           
                                    Front Stagger vs. Rear
Rear.....how do we know where to start? Above, I gave you an idea of the factors we need to consider when choosing what we want for stagger. I also mentioned that I will always run as little rear stagger as I can get away with because it helps keep drive over a long run. I did not always have this thought process when it came to stagger, I was the guy that if the car was a little snug, thought it was wise to open up the rear stagger....how many of us have done that? Then a driver that I was testing with, and for whom I have a great amount of respect, asked me why I run so much stagger. I answered "because that’s what we have always done.” He laughed at me and said "If you had 2.5" of stagger and pulled the rear end around the corner with a string it would end up in the infield before you ever got to the apex." That comment stuck with me and from that point on, I have worked on getting as much stagger out as I can get away with.
Front.....I always run my front stagger around 1/2" less than the rear for no other reason than I can pick my tires with all 4 chalk marks the same and be able to keep all my date codes the same. But really, being that the front end is independent of what we run for stagger is not that important - other than what you set up on and set your sway bar load to, you should keep when you get to the race track so as to maintain consistency in your sway bar load.
                                               Date Code
How many of us have worked all day in practice to get our car balanced? Car turns good and has good forward drive, our lap times are good, so “Let’s fill it full of fuel and put tires on it." We send our driver out and we have our stop watch in hand, adrenaline pumping and then the disappointment. The car was horrible. We went quicker on 100 lap tires than we did on stickers. So frustrating! Not always the case, but 9.9 times out of 10, it is a result of improper tire selection. Every tire has a date code. It is a 4 digit (usually 2 numbers and 2 letters ie: 3K5Y) number that is randomly generated. This number represents the date the tire was built, the batch of rubber that was used to build it and the machine it was built on (inside the tire is a 2 digit number that even represents the employee that built that tire). Why is this important? Well, like everything that is manufactured, there is a tolerance that must be held in the process of building these tires. How does that affect us?  Let’s go back to our example of having a balanced car. We put tires on it and got slower and the balance is horrible. If we had selected our tires so that all the date codes matched (or at least the rights were the same and the lefts were the same), then we would know that at least all the tires were within the same tolerance, so therefore, if we put 4 new tires with the same date codes as the first set then we can feel confident that we will not change the balance of our race car as they all were built within the same tolerance.
On the other hand if we only go in the tire truck and pay attention to the chalk marks, then we don’t really know what we are getting. Maybe we are putting a RF tire on that is on the harder side of the compound tolerance and a RR on that is on the softer side of the compound tolerance....In this scenario it makes it very difficult to maintain a good balance.

In a game of inches we need to pay attention to all of the little details that we do have control over...If you don't, the guy that you are racing against is.