This is a test. It is only a test, so please do not adjust your race car, yet. The following is a significant test and involves certain discoveries and logic. It's not significant just because I wrote it or because it's in this magazine. Its significance stands on its own. If you read this and don't come away with a new outlook about bump technology, I urge you to re-read it, the message is in there.
Stan Flis, machinist and fabricator for Spirit of Daytona Racing, which runs a Chevrolet C
It's no secret that I haven't been in favor of the soft spring setups using bump rubbers as springs, let alone the ultra-large antisway bars in conjunction with those soft springs. I have already explained exactly why I have been opposed to that, what those setups do to a good race car and how, even now, many well qualified racers are struggling with them.
That being said, there may be a solution to the problematic use of bumpstops and this is the purpose of this test. We intend to show that we can achieve the low and superior attitude for our race cars while not having to give up handling and mechanical grip. Now, if this works the way we think, we can have our aero and handling too.
History and Development of Bump Technology
All of this soft spring and running on bump rubbers stuff started with the Cup teams and involved a "looking down a tunnel" mentality that was only concerned with enhancing aero efficiency for both reduced drag and increased downforce. And all of that is good, to a point.
What happened, as I heard it, was that indeed the cars got faster, stuck to the track better, and handled like crap. The drivers complained, but were told to basically shut up and drive. There were and still are, certain compromises associated with going faster this way. And the older drivers had big problems driving those cars. Dale Sr. credited Dale Jr. with helping him overcome his confusion about these setups and to trust that the car would stay on the racetrack despite all of the bouncing around and weird attitude.
Meanwhile, it all got back to the short track guys and the thinking was, if it's good for the Cup cars, maybe we should be doing it. And so, the big bar and soft spring, or as some prefer to call it, soft spring and big bar, setups took hold and now nearly everyone thinks they need to go this route in order to be successful. And there is little that anyone can do to dissuade them from this direction.
This is the configuration when assembled. This was exactly what I had envisioned when I fi
Installing the coilover assembly the first time told us that we needed clearance between t
Here we see the right coilover assembly and it had much more room for adjustment and lower
Problems Associated With BBSS
Right away, certain teams went faster and won. These were admittedly some of the more well-financed teams who could afford to gamble and who had the resources to test and buy the components needed to make these setups work.
What is still happening is that these setups are very difficult to tune to various racetracks and even at the same track when conditions change slightly. Big-name racers like Freddie Query and Jay Fogleman, two guys that I know personally and whom I have talked to about this, are still searching for ways to accurately predict just how to set up for the soft spring setups.
Both of these gentlemen will tell you unequivocally that these setups are necessary and will provide more success than either soft conventional or conventional setups. And I for one will not argue with this level of experience and talent.
So, the question is, how can we make these setups more manageable and comparatively easy for the average racer to achieve? This question has more or less haunted me and intrigued me for some time now. Then I attended the PRI show in Orlando this past December and a light went off.
The reason why the BBSS setups are so much of a problem lies in the way the bump rubbers perform. The characteristic of the bump rubber is such that it has a spring rate and that rate is variable. It changes as the rubber is compressed and the rate rises in a non-linear way.
That means that in the first 0.100-inch, the rate may increase by 100 ppi (pounds of spring rate per inch of compression). In the second 0.100-inch the rate may increase by 200 ppi, and in the next 0.100-inch of travel it might go up 400 ppi and so on. At some point in the compression, and it's not very far, maybe a half inch or so, the rate increases dramatically and just beyond that it goes basically solid.
Much time and expense is spent right now, by many teams including the aforementioned two, trying to determine just how much spring rate, or loading, is on those bump rubbers at a particular track in each turn. And by using that information it is hoped, and I repeat the word hoped, that a conclusion and method can be established that will help them set up for any track. As far as I know, that hasn't happened, but I will say that each is getting much better at it and they are accumulating more and more information.
A Light Goes Off
I was attending the PRI show in Orlando this past fall and I heard about some new type of spring that my old friend Kelly Falls and his engineer, Mark Campbell, had on display. It's a carbon-fiber disc bellows spring that is designed to replace a steel spring in certain applications.
One could see this being used and highly appreciated in IndyCar and Formula 1 racing and other formula-type of cars because they're lighter and take up less space. The jury is still out on whether it will be useful for short track racers due mainly to the limited travel before spring "coil" bind, but this item is still very new and development is still underway.
I saw and envisioned something different. I had an idea. For some time I have thought that if we could get the car down on a bump apparatus that could maintain a more constant spring rate throughout its useful range of travel, we could then predict and manage the setup.
If, say, we know the spring rate of the bump was 1,500 ppi through an inch or so of travel, then we could design the setups and balance the two ends of the car accurately. When I returned home, I envisioned how to install those bellows springs on a Late Model to test the theory.
The car would have to be a big spring design so we could use the shock for placement of the bellows springs without being impeded by the coilover spring. The idea was to install light big springs for static ride, then allow the shocks, with the bellows springs installed on them, to take the load in the turns. If we used a shock that would hold the front end on those bellows springs, even better.
All I needed was a set of bellows springs with a 1,500 ppi rate, an aluminum sleeve to take up the gap between the bottom of the shock and the bellows and a few other items to make this work. For a car and team, I had an ace in the hole.
Dick Anderson designed the Anderson Elite chassis that Port City Race cars sells to this day and of course Dick runs one of these chassis. It's a big spring design, much like the stock version front ends. He agreed to work with me to test this approach and we selected Orlando Speedworld for two reasons. One, it was close by; and two, it was more of a handling track with lower banking and shorter straights than a track like New Smyrna, another track that was close by.
Our driver would be Dalton Zehr, a very capable shoe who won more than a few races up north driving Gene Coleman's cars this past summer. He has also been our test driver for our G.R.E.E.N. Racing project Camaro as well as other projects including the Late Model stock car we took to North Carolina a few years ago.
The left shock assembly was very close to being too long for this installation. We could h
We first set the crossweight with the car at ride height with the big springs installed. T
When we first installed the coilover bellows assembly, we lowered the car onto the bellows
So, to configure all of this, I had a couple of 2.5-inch inside diameter aluminum tubes made up in an 8.00-inch length and I took them to a local Grand Am race shop where Stan Flis machined the ends perfectly square. This was important in that these tubes would be in contact with, and needed to be square to, the bellows springs.
We mounted the bellows springs onto double adjustable shocks that had been specifically designed and valved for bumpstop use where the rebound at 3.0 inches per second was around 1,050 pounds for both shocks and in the LF shock, the piston had no bleed hole and the bleed adjuster was almost closed off for this test, cracking the bleed about a half sweep. The compression in both shocks was around 100 pounds. at 3.0 ips.
I developed two setups using software. The first one was in harmony with an article I wrote that described how to have a zero roll angle. The idea was to design the front so that it rolled to a positive number, something it would always do anyhow, and to cause the rear to roll to a negative, but equal number related to the front.
In this case, the front roll angle was 0.70 degrees positive and the rear was 0.65 degrees negative. The net roll was near zero. To accomplish that, we installed a Left Rear 165-ppi spring and in the RR we installed a 410-ppi spring. The Panhard bar was at 10.5 inches on the left and 11.0 inches on the right measured from the ground.
The other setup I developed caused equal roll angles, both positive, in the front and rear. The thinking was that if the zero roll design did not work, and I'd really never tested it before, I could go with the second setup. It only involved switching to a 275-ppi RR spring with no change to the Panhard bar height.
The software recommended a crossweight distribution of 53.0 percent for this car, but Dick always ran 56 percent in his cars, so we went with Dick's cross. In setting the cross, we first set it with the car at ride height with it supported by the big springs.
Then we removed the big springs and let the car sit on the bellows springs. We then adjusted the rings on the shocks to attain a 56-percent crossweight while on the bellows springs and left the rear springs like they were at ride height. This meant that the car would experience no load distribution change on the tires going from riding on the big springs to riding on the bellows springs.
Incidentally, when we initially dropped the car down onto the bellows springs, we had approximately 1/16-inch clearance for the front valance. So, we adjusted the bellows heights up so that we had about a half inch of clearance.
While the car was down on the bellows springs, we also changed the front cambers to what we thought would work and knew we might need to make adjustments at the track. We set negative 5.0 on the RF and positive 2.5 on the LF tire. We also installed a medium 13/8-inch antisway bar.
On Track Testing
Backtracking somewhat, Dick had gone to Orlando Speed World the previous Friday and tested the car with Dalton and with his tried and true setup. They had recorded lap times in the mid 14.1s at best and Dalton reported that the car was very good and consistent. In fact, Dick had said to me that he had never seen the car work so well at this track as it did in that test.
Once we got to the track the following Wednesday, February 1, we set tire pressures on the same tires that now had about 50 laps on them. A very good lap time here when other cars are running and the track is clean would be in the 14.10s and 14.20s on previously run tires and 13.6s and 13.7s on stickers. Most cars practice in the 14.30s and 14.40s.
The first run had us with two 14.15s and a 14.08. We came in and checked the front tire temperatures for camber. After making small adjustments to the LF and a bigger one to the RF, we went back out. This time the lap times were in the 14.0s with a 14.05 and a 14.06. This is right out of the trailer in two runs and we are already quick.
With the car down on the bellows springs, we also measured and adjusted the front cambers.
The car was a little tight at mid-turn and the RR tire was some 30 degrees hotter than the RF tire. This was partially due to the tight middle causing a loose off, but also due to the stiff spring we were running in the RR. I was surprised at how close we were to balance with that spring and the zero roll setup. I quite frankly didn't know what to expect. During the first couple of runs, we felt that the antisway bar was loading a lot when the car was down on the bellows springs, so we changed to a 1.25 medium antisway bar. We also reduced the rebound in the LR shock to help with a loose off condition we noticed and that was creating heat in the RR tire. After several more runs and small camber adjustments, the times stayed in the 14.0s consistently, but the car continued to be slightly tight at mid-turn. It was here that we suspected the tires might be a problem and we had brought with us a brand-new set of Hoosiers. We installed the new tires and made a sticker run turning in the mid 13.70s and low 13.80s.
It was at this point that I remembered the crossweight being three percent higher than the software suggested and we then decided to go with the equal roll setup by replacing the RR 410-ppi spring with the 275-ppi spring and droppping the crossweight to 53 percent.
On the next run the car was very neutral in handling, and was noticeably rotating nicely through the middle. The RR tire was also 25 degrees cooler than previous runs and was now almost equal to the RF tire temperature. The lap times stayed in the 13.80s throughout the next three runs of five laps each. We then decided this test was over in order to save those tires for a test planned for New Smyrna Speedway the next week.
The attitude at Orlando was exactly what we desired and basically what most of the teams s
Dick was very pleased and even amazed at these results. The fact that we came with a totally different and untested setup, were running on the equivalent wheel rate of 1,300 ppi (you have to add the bellows spring wheel rate to the big spring wheel rate since they are in parallel, not in series), a green track and used tires that resulted in being almost two tenths quicker than what he considered the best his car had been in the Friday test. I just wanted to make note here to the readers about the car. This particular car with Dick and other drivers has won numerous races in the past few years at this track and so having him participate in this test with this car was significant and valid. And, Dalton has proven to be a very fast and consistent driver as we have noted.
Next Phase, New Smyrna
On Friday, February 10, there was an open test at New Smyrna Speedway in preparation for the Pete Orr Memorial 100-lap race the next day. We ran the car with Dalton driving and were running the car along with many of the top teams that would run the race.
Right out of the trailer we were turning laps in the 18.0s and no other car there turned in the 17s on used tires. The quickest times were in the 17.6s when a car went out on stickers, so we felt good about both the setup and this arrangement.
The only downside was that at NSS, in the middle of Turns 1 and 2 there is a bump and with the stiff bellows springs we were running, it caused Dalton to wait to get back in the throttle a tad and we felt with softer bellows springs that would ride out that bump better, he might have been able to improve his times by a tenth or so.
What we have tried to demonstrate with these two tests was that not only can we easily setup a car for bump racing using a constant spring rate type of bump, but can also run quicker lap times in doing so.
I feel that with this arrangement and staying on the bumps, the tires maintain a consistent camber angle to the track the entire lap and this provides consistency in grip. It also means that the load distribution stays consistent both due to the car staying on the bumps and elimination of camber change which will redistribute loads somewhat.
We backed up our testing at New Smyrna because it is a different type of racetrack. Orland
Where Does All of This Go
By now you are probably wondering, what does this have to do with me? This configuration obviously doesn't work with most of the coilover cars out there racing today. But, Hyperco engineers are now in the process of designing a device that can be installed on the shock shaft and perform much like the configuration in our test. By the time you read this, they will probably have a prototype built with production soon to follow. Not only can this type of bump device be used on asphalt, but select dirt late model teams are experimenting and winning races running on bumpstops at one or more corners of their cars. There is a high possibility that this would work well on those cars too. As I write this, Donnie O'Neil just won the first night of Speedweeks at East Bay Raceway on a right front bumpstop setup that is the rising rate configuration. The ride would be much smoother and less hard on the suspension with this type of bump device.
The new bump device Hyperco is developing will be tested, maybe by CT and probably by others in the industry, to ascertain its benefits. If it performs anything like it did in our test, I can assure you that developing your setups and realizing consistency in handling will come easier with this type of product if you decide to go this route.
This test solved my curiosity about the benefits of running on a consistent rate of bump spring, while also satisfying the needs and wants of the racer in the desire for a low profile, lower CG and less load transfer, and better tire heat distribution and reduced wear. Only time will tell, but from our observations, we can see where this design might revolutionize the industry. I have finally come to like bump racing.