Category: SCCA Trans-Am
For years now one of the trademarks of a first class SCCA Trans-Am, or IMSA GTO car was the centerlok wheels. Just by a glance at the wheels you could tell who was a serious contender, or a pretender. Generally those wheels were made by BBS, although Jongbloed and a couple of others were occasionally seen.
What was the reason that the centerlok, more properly center knockoffs, rather than the almost universal 5 x 5 pattern wheels were used? Basically there were three reasons.
1. Unsprung weight. The suspension components and hubs were lighter than on an equivalent 5 x 5 assembly.
2. Suspension geometry. Most designers are proponents of the “zero scrub” design. This requires getting the wheel mounting flange as far outboard as possible. In other words a typical three piece centerlok front wheel will have a 1″ or 1.5″ outer rim half. Because of its spindle design a 5 x 5″ wheel has to use a wider outer rim half, perhaps 3.5″ or 4″.
3. Pit stops. With the single nut, the time to change tires was less. Admittedly this was the least important of the three factors.
But nothing is without drawbacks, and this is no exception. The price of a centerlok suspension assembly is far more than that of a 5 x 5. How much, did you say? Well it varies but it is hundreds of dollars per corner. Wheels for the 5 x 5 are far more readily available and at a fraction of the cost. And lastly since most races no longer require pit stops the speed of tire changing is pretty much irrelevant.
I should note that there is a hybrid design, used back in the 90′s by Peerless and a few others that adapted a 5 x 5 hub to use centerlok wheels. This was neither fish nor fowl, didn’t solve the geometry issue, and added about one pound of weight per corner.
So which is the right way to go? Depends on your wallet I guess. If money is the most important thing than by all means go with the 5 x 5. But if performance, and looking the part, are critical than the centerlok is still the way to go.
Get your mind out of the gutter, I’m talking horsepower here.
Whats the first thing people talk about when discussing racecars? How much power the thing has of course. And few things are more misrepresented. Regardless of what it is everybody feels compelled to believe they have the most powerful engine out there. (unless you get beat when the engine was down on power, of course).
But what numbers are we really talking about? There was a time not too long ago, when a really strong 310 CID engine would put out around 700 HP. Some of course did a fair bit more. But these were limited to one or maybe two teams. And while they would sell those engines, they didn’t seem to do as well with the new owners. Some say the heads were changed before the motors were delivered, but I digress.
Then with the introduction of the e Nascar 358 engines, horsepower went up to around 800 +/-. And a whole new world appeared. Transmissionssuddenly became a problem, as did tire management.
A couple of years ago, when the new generation of engines arrived in Nascar the old SB2.2′s, and Ford’s w’Yates heads became obsolete. The teams needed a market so some of them found their way to the road aracing scene. And for prices that were too cheap to pass up. And now the power level was up to 835 approximately.
Last year things progressed even further. People found that even with that power they couldn’t keep up at the power tracks. Why, you ask? Well it seems that there was a generation of cylinder heads produced, by both Ford and GM, that was not approved by Nascar. These heads, or at least some of them have found their way onto the track. And by the way they are completely legal. But one builder told me they were worth 25 horsepower on his engine. His driver said that he can finally run with the top cars after the upgrade. Power? 850 +.
So whats next in the quest for “more power!”
We all love the cars we see at the track in various Trans-Am or club races. But by now I bet you have noticed that there are a pretty good amount of cars that don’t finish. Now why do you think that is?
Now of course there are the occasional failures where an engine blows, or a clutch fails. They are just a part of racing. Probably we can lump into that category, the time that the driver spins out, wrecks, or even goes from 4th to 1st gear and throws the driveshaft out of the car.
But far more common is the simple failure caused by being in a hurry, not having a maintenance program to follow. How can a pro racer have the fuel filters get clogged up with broken down foam from the fuel cell. It’s happened on more than a couple of occasions. How about the car having unpredictable handling because the heim joint on the watts link was letting the rear end around. Have you looked at the heims on your car lately.
In short, racing is expensive, and it doesnt cost much to have a maintenance program that makes sure you dont overlook the simple things.
Sure the other way provides more drama, but of a kind that your blood pressure doesn’t need.
But I was speaking yesterday with one of the competitors who is still successfully using a standard STA200 (aka narrow gear) tranny.
This fellow has been using this transmission for several years, graduating from a 700+ horsepower 310, to todays 850 horsepower 358. During that period he has had only one failure, a broken tooth on a 3rd gear during a race when he was running a 310.
When asked about the durability with todays motors, he first qualified his response by saying that he was pretty easy on transmissions. That the driver was a major contributor to the success or failure of any transmission.
But that aside, the big motor does require much more maintenance on the transmission. That the gears had to be closely inspected after every race. And, at the first signs of pitting they MUST be discarded. Otherwise they will soon fail. Other than that they follow a normal maintenance schedule for the rest of the components.
When asked if he felt that the wide gear was the proper way to go, the response was that yes it was better, but he needed other things first.
So, I guess like most things in a race car, it depends on your priorities, but if you dont have a spare 15k, you can still survive.
Yes, such a thing does exist. The car pictured was built by Rocketsports for a customer in South America. Nascar Craftsman truck engine, Hewland transmission. Supra body in carbon fiber.
Always thought it would have been good in the Trans Am.