Every racecar driver battles weight. I battle with it because I like cheeseburgers. Other drivers already have conquered diet and exercise habits and they battle with weight because their car is too heavy. Regardless of whether it is because of milkshakes or heavy wheels, the goal is to hit the scales at the end of a race within 5 pounds of the minimum weight. But overall weight isn’t the only issue. Weight distribution is enormously important for a racecar. You don’t want one tire having to do all the work. It is more efficient if all four tires can share the workload. That is accomplished by balanced weight distribution.
How you get there is the interesting part. Manipulating where a car carries the majority of its weight is dependent on the rules of a particular class. In Honda Challenge, all added ballast — a maximum of 250 pounds — must be in the area of the front passenger seat/footwell. That doesn’t give Honda Challenge racers much leeway in making their cars more balanced, especially a front-wheel-drive car that comes from the factory with a pretty heavy front weight bias. The trick is to read the rules and find a way to legally change the weight balance of the car.
NASA stewards are no dummies, so the first rule in Honda Challenge, rule 1.1, takes away any shenanigans: “If these rules do not expressly state a modification is allowed, it is prohibited.” This means don’t get too creative with the gray area. If it doesn’t say you can do it, then you can’t. However, keep reading because rule 7.1.5 gives Honda racers some leeway: “Fasteners are unrestricted but must perform the exact OEM function.” OK, now we are getting somewhere. Bolts, as long as they do the exact OEM function, which is to hold stuff together, are unrestricted. Can we save weight with bolts in one part of the car, and add weight with bolts in another part of the car? Absolutely we can.
Hardware shouldn’t be a mystery. Bolts have lengths, they have thread pitch and they have the makeup of their material. The trick is knowing what you have and what you can replace it with. We use a bolt gauge to take the guess work out of determining the exact size and thread pitch of any piece of hardware. Once we have the data from the bolt makeup, we search for an alternative piece of hardware that is lighter. For Honda engine hardware, we found Speed Factory Racing manufactures direct replacement parts made out of titanium, which are nearly as strong as steel and weigh about the same as aluminum. Strong and light is a win-win.
To determine the metallurgy of a piece of hardware we simply use a magnet. If the magnet picks it up, then it’s not aluminum and probably not titanium. To weigh our different pieces of hardware, we picked up a simple small digital scale from Amazon, which only set us back about $10. As we replaced different bolts, we took the time to weigh the stock metal ones and then weighed the replacement pieces (made with aluminum or titanium). For things like fender bolts, we used aluminum. For pieces that held together crucial parts of the drivetrain, we used titanium.
Metallurgy wasn’t the only way to find weight savings. We also looked carefully at the length of bolts. If, say, a fender bolt had a significant amount of bolt length past the actual thread that held it in place, it could be shortened. There is no need for long bolt metal that isn’t doing anything. Additionally, we found some weight savings in bolt head size and design. Probolt has bolts that replace many 10 mm bolt heads with 8 mm bolt heads to save weight. They also drill holes in the bolt heads and bowl out the top of the bolt head for additional weight savings. Sure, it may be just a few ounces, but these ounces add up. Remember just 16 ounces is a pound.
Some of our weight savings through fastener replacement came from simply digging through our own parts bin. For example, Acura placed a long-head extended bolt to make it easier for mechanics to reach a bolt while working on the engine. We aren’t looking for convenience. We are looking for lightness. We found a replacement bolt we had removed from somewhere else on the car that worked perfectly and was considerably lighter, especially since Acura used this long bolt in three different locations.
If you are serious about weight distribution, weight savings, or you are just really bored and want to take stuff apart that isn’t broken, consider your hardware when building your racecar. We went a bit crazy on our Honda Challenge 4 Acura Integra, replacing a lot of hardware on the front of that car with aluminum and titanium. I won’t lie to you here. It wasn’t a cheap experiment. Titanium is pricey, but the car did win the 2018 National Championships at COTA. How much is a championship worth to you?
To read more from Rob Krider, or to contact him, go to www.robkrider.com.