Drag racers have had a good problem for the past few years – horsepower, and lots of it. That’s what it’s taken to get some of the heaviest door cars into to sub-7-second range. The advancing technologies in fuel injection systems, digital ignitions, and overall engine design have made horsepower not only easier to obtain, but also easier to control. It seems in just a short few years, door slammers have become brutally fast to the point of surpassing the mandated chassis certifications. The problem was, there was not an SFI spec to “allow” some of the quicker/heavier cars run legally, that is, until September of 2009 when the new certification “25.3” was introduced.
Talking with Chassis Builder Bryan Metz and SFI’s Jennifer Faye on the 25.3
We contacted chassis builder and SFI committee member Bryan Metz about what exactly the 25.3 cert will entail. “To put it simply, we’ve combined the 25.2 and 25.5 rules, and then added in specifications to the rear portion of the cars,” he said. “We wanted to ensure the rear of these cars have additional tubing to reinforce the factory frame rails. Before, the main focus was on the driver’s cockpit area, with the 25.3, we now have guidelines to go off of for the whole racecar, front to back.”
Metz also explained that a decade ago there weren’t chassis certifications, just a basic guideline of 9.99 type cage. As the cars got quicker and heavier, SFI mandated 25.5, 25.2, 25.1 and now 25.3. The SFI Foundation’s Jennifer Faye was another insider we contacted on the subject, “The need for such a spec did not present itself until a few years ago. Until then, the existing specs were sufficient. As technology of the equipment advanced, along with the talent of the builders, tuners, and racers, it rapidly became apparent that the heavier door cars would eventually break through the existing specs.” It wasn’t until such sanctions as the NMCA, NMRA, PSCA, and ADRL petitioned for SFI to start developing something that will allow these heavy cars to run at their full potential, while remaining within SFI’s specs.
The 25.3 specs new require a 1-1/8 “X” brace in the roof, whereas the 25.5 specs call for a single bar. This, according to the chassis builders we spoke with, is a relatively easy addition when a car already is certified to 25.5.
Faye explained, “With most SFI specs, sanctioning bodies who are members of SFI will recognize the need for a new spec and formally petition SFI to develop one. Then SFI will form a technical committee comprised of product manufacturers, engineers, and sanctioning body officials who all have valuable input into developing a particular spec. Of course, in the case of roll cage specs, it is chassis builders who participated.” She continued, “In some cases when developing a brand new product specification, the technical committee is literally starting with a blank sheet of paper. However, sometimes existing specs and precedent can be used as the groundwork when developing specs that expand into new performance parameters, as was the case for 25.3. It is generally based on Specs 25.2 and 25.5 with considerations added for the heavier weights involved at those speeds.” Metz added, “We wanted to get enough tubing back there that if the factory rails were starting to rot, you are covered. If the frame is rotting from the inside out, which can happen, now we’ve got a tube in there that, in essence, is replacing that. The factory frame will still be there, but it’s another structure that will be able to take an impact. For the most part, it’s a fairly simple change from a 25.5 or 25.2. Basically 25.3 feature the majority of the tubes, making sure that there is some structure behind the driver,” Metz said.
The new 25.3 chassis certification outlines some newly required bars in the rear portions of OEM cars. Before, with the 25.5 cert, there were no real specifics of how the rear portion needed to be laid out. Still, good chassis builders would enforce the reason their own, but now with the 25.3, it’s a requirement.
Who Made 25.3 Possible?
Some of the country’s top chassis builders teamed up to develop this new certification, Richard Earle of Suncoast Racecars is the chairman of the committee. “While he may not be a primary builder of these cars, he was selected as chair due to his experience with the SFI process,” Faye explained. Other builders included Dan Neumann of Dan Neumann Race Cars, Chris Lundsford of Sheppard Race Cars, Mark Wilkinson of Racecraft Inc., Bryan Metz of Metz Performance, Gary Rohe of Gary Rohe Racecars, and Larry Larson of Larson Race Cars. SFI also appreciated the invaluable input from Trey Capps of ProMedia, Jim Collins of NHRA, and Roger Goode, who is SFI’s Professional Engineer.
Although we spoke with Bryan Metz of Metz Performance for this article, other chassis builders that helped develop 25.3 include the Chairman, Suncoast Racecar’s Richard Earle, Dan Neumann of Dan Neumann Race Cars, Chris Lundsford of Sheppard Race Cars, Mark Wilkinson of Racecraft Inc, Gary Rohe, and Larry Larson of Larson Race Cars. SFI also appreciated the invaluable input from Trey Capps of ProMedia, Jim Collins of NHRA, and Roger Goode who is SFI’s Professional Engineer.
This 25.3 chassis spec is intended to for OEM frame or OEM-modified frame door cars that are faster than what a 25.5 covers, but heavier than a 25.2. The sanctioning bodies, along with SFI quickly recognized the need for this separate spec. “What’s interesting, though,” Faye said, “Is that at the same time sanctioning bodies were requesting a new spec that would eventually become 25.3, car builders who were already familiar with working in SFI chassis specs were also calling SFI expressing their need to fill the gap between 25.2 and 25.5. They were looking for guidance in how to build these faster, heavy door cars with appropriate safety in mind.” According to Faye, other sanctioning bodies recently joined SFI such as PSCA, who were not members at the start of the 25.3 project, but are indicating that they are interested in using the spec as well.
Here are three examples of funny car cages from the SFI book. For the most part, this area will stay the same for all three chassis specs.
What’s the difference from 25.3 to 25.2/25.5?
So the big question on everyone’s mind is, what are some major things that are different on a 25.3 spec compared to a 25.2 and 25.5 in terms of added bars? Faye elaborated, “Historically, when SFI chassis committees work on developing a roll cage spec for a performance range that grows out of existing specs, they keep in consideration that there may be cars in the field that need to be upgraded to the new spec. With that in mind, the spec is developed to meet the necessary safety parameters, but so that some existing cars can be updated to meet the new requirements. While not all cars can always be updated, some can.” She went on, “There is also standard precedent that must be followed for any chassis spec, whether it’s for a door car, dragster or funny car. For example, any chassis faster than 7.50 must be constructed of all round chrome moly tube.
For years, the 25.2 roll cage was the ultimate chassis for a door car, but its 3,200-pound limit was a bit unrealistic for certain high-powered combinations. With the new 25.3 specs however, you will now will be legal to run as quick as 6.50 at 3,600-pounds.
Like the 25.2 specs, the 25.3 certification will require extensive reinforcement of the floor. This can be the most difficult and pricey aspect of a chassis of this type. Often times chassis builders will cut out the factory floor, build the structure, and reinstall the stock floor.
In taking on the task of developing Spec 25.3, the committee used 25.2 as the basis and included construction requirements from 25.5 that pertain to OEM frame or modified frame cars such as the rear frame rails and rear braces, as examples. In Spec 25.3, you might see a little more detail in specific construction requirements than in other specs because in addition to the safety objectives, the committee took the perspective of providing builders with a more detailed guideline to building the chassis.” According to SFI you will see the major differences between a 25.3 and a 25.5 roll cage will be in the roof, door, and floor bars. Either additional bars or larger bars (or both) will be required. In some cases, there are options available to keep existing bars while adding support tube members to meet the new spec. These are only generalities, so a builder will definitely want to obtain a copy of the actual specification from SFI in order to have the
The gussets for 25.3 spec cage have to be a beefy 1-inch diameter to meet the requirements, similar to the 25.2 specs. For racers with a 25.5 chassis, this is something that is not required.
The two previous chassis specs mostly concentrated on the driver’s compartment, but didn’t specify what needed to be in the rear portion of the car. The new 25.3 guidelines specifically state what needs to be in the back-half of the car. As you can see in the photo of one of our 25.5-spec project cars, there is minimal tubing in the trunk, the new 25.2 and 25.3 certs will address this area more thoroughly.
Like the 25.2 chassis, which is legal to 6.00 at 3,200-pounds in the quartermile, a 25.3 chassis will have to be entirely made from chrome moly tubing. Racers that have real muscle cars with mild steel cages will simply have to step up to CM if they want to go quicker than 7.50, or simply go with a full tube chassis.
Here is an example of the bar structure required for a 25.3 chassis spec. When these 25.X certifications were first introduced, the main focus was around the driver. Now, chassis experts and SFI want to see some support behind the driver, making the whole racecar sturdier in the event of an impact.
A Chassis Builder’s Take on the Change
We asked Metz if he felt this upgrade is good for the sport, or just another thing to deplete a racer’s pockets. “For us at Metz Performance, we expect to see a lot of upgrades to this spec, I’m sure.” I think it’s good because now there’s a safe spec to allow anything quicker than 7.50 to run at 3,600-pounds. It really gives some racers a larger window there are a lot of cars out there that are chrome mol, but weigh too much. This will salvage this situation. We have three or four customers that weight a couple hundred pounds more than their cert will allow, now they have the option of getting those heavier car back on the racetrack and it’s a minimum upgrade.”
One class the new 25.3 cert is supposed to help is the NMCA’s ARP Nostalgia Pro Street. For years, these cars were too quick for 25.5 and too heavy for 25.2, now the 25.3 will accommodate these racers.