Bumpstops are starting to...
Bumpstops are starting to make a comeback. KEVIN THORNE
Every now and then, a new design or advancement in technology produces a new and innovative part for short track competition. At first glance, it might appear that bumpstops fall into this category, but in truth they are nothing new. Bumpstops first broke on the scene in the late '80s and early '90s. NASCAR quickly outlawed them because of the potential complexities and to help smaller teams that might be unable to adapt.
Bumpstops are pieces of rubber or plastic attached to front shocks to limit shock travel. They are applied to the front only, because this is where the chassis will experience the most travel in a corner.
This may all seem simple enough, but I can assure you the simplicity ends once you attach them to a shock. Why limit shock travel in the first place? The simple answer is that the shock and spring setup under a Cup car all work together and the team that could figure out the perfect combination would dominate until other teams caught up.
With the introduction of the Car of Tomorrow, NASCAR has allowed bumpstops back into the sport. As with most decisions that NASCAR makes concerning the cars under its sanction, the ripple effect can be felt all the way to the local short tracks. Bumpstops are now beginning to be allowed in series all around the country, which prompts SCR to give the grassroots racer a primer on bumpstops.
Again, the problem is that they seem so very simple, but this is where most teams go astray. Bumpstops usually fit into a small cup that slides on the shock, and there are a number of different sizes and levels of hardness to choose from.
The first time I used bumpstops was at Iowa Speedway last fall in a Hooters Pro Cup race, as we had trouble with the chassis and exhaust bottoming out and scraping the pavement in the corners. The car was experiencing way too much travel in the front. Without bumpstops, bigger springs in the front end would have been our only solution and this would have changed the chassis dynamic, requiring a new setup underneath the car. Instead, we measured our shock travel and put the bumpstops to where the shocks sat on the stops, limiting the travel in the front end. We qualified Sixth with the stops.
So, we learned, there is speed to be found in bumpstops. But there is no good reason to slap them on and go racing on Friday night. You need to test over and over again to see if you can find speed. The advantage is the ability to run softer springs in the front of the car without the worries of bottoming out the chassis or rubbing the exhaust. Once you place the stops on the front shocks, you then have to work to get them perfect.
The height of the bumpstop is vitally important to how the car handles through the corner. If you don't have the heights correct on the bumpstops, the shock can actually hit the stop and then bounce back up and try to rest on the other bumpstop. This is where it is extremely helpful to have a shock specialist helping your team. Our team uses R.E. Suspension out of Mooresville, North Carolina.
This is basic bumpstop setup,...
This is basic bumpstop setup, with a cup for the bumps to sit in, two sizes of stops, and two sizes of shims for spacing. JOHN GIBSON
R.E. Suspension has built...
R.E. Suspension has built shocks for every type of racing imaginable, from dirt to asphalt. JOHN GIBSON
Here is a 1/4-inch shim for...
Here is a 1/4-inch shim for raising or lowering a bumpstop. These shims are so crucial that they are now being produced as small as .o1-inch. JOHN GIBSON