I have a Model A coupe that I drag race, rear suspension is 52" ladder bars with coilovers 100 lb. springs, 9 inch Ford rearend, the front is a superbell 4" dropped straight axle in front of the frame spring over the axle. The car just does not transfer weight to the rear tires worth a shit. With the ladder bars being so long I have a high center of gravity but the front end just does not travel. I know with the front end being lowered this isn't helping things at all.. Anyone that used to drag race a car similar to this have any tricks that they would like to share? I have a blown small block in the car, powerglide, 5000 converter and a transbrake. My goal is to get the car to run high 5's or a 6 i the 1/8 mile and to be a holy terror on the street. With the car not hitting the tires hard it will be impossible to make it hook on the street.. Any help????
"With the car not hitting the tires hard it will be impossible to make it hook on the street.. " To answer your question, yes. Shorten your ladder bars. Better yet, go to a rear four-bar setup. You need to be able to adjust it.
I'm thinking you have weight problems, if the car is supported with 100# springs you need some rear weight, the car is way nose heavy and c/gravity a bit high so that weight won't transfer (made worse with straight axle suspension having limited bump rate and travel). The newer mustangs have this type of weight issues and that is one of the reasons why they can 'light up' the tires so easy, not a question of horsepower just a lack of friction. Smart thing is to 'scale' the car (as opposed to wieght the car). Lay a piece of butchers' paper alongside the car and make a scale drawing of the suspension point heights incl the pinion; transtailshaft; balancerbolt; upper and lower ladderbar bolts on rear (with optional holes); front ladderbar bolts; distance from pinion to trans; to balancerbolt; front and rear wheel wieghts. Usually when you layout the car in this manner the reason why you are having a problem and what to do about it will be obvious. If it is still muddy post it here and somebody will fix you up or you can PM me and i'll do what i can to help. Good luck, oj
Gotta have a straight axle get the frt. end up. Thata' the only way to get weight transfer in a rod like yours.
Your ladder bars are probably pointed upwards. COnsider what they do. They provide leverage to press the tire to the ground. If they're up the leverage points are against them. You may have to drop em and change the pinion angle to something like 4deg down in addition to the change. It's hard to diagnose these thigs without seeing what it does on launch.
BTW 6.00 1/8th is 9.40 1/4 mile et. Pretty quick for a car that runs on the street. Gotta have a certified cage and all of the current certs on all of the safety equipment (a LOT). Is this the car in your avatar?
Sounds like you do not have enough motion going on in the rear end setup. Have you played with the spring setting on your coil overs? Are you running street tires or slicks?
I don't drive any distance maybe 5-10 mile trip would be it. We street race about 4 miles from my house late at night on weekends. All the nostaliga races that I have been to say seat belt and helmet and you can race.. Yes it is the car in my avitar..
That is how I got to the 100 lb spring to let the car squat.. I run slicks, tried a 13 inch wide drag radial and it spins like hell on the track or street.
Ladder bar rear suspensions do not squat. They lift. The ideal scenario is that the car is, in a sense, lifting up at the pivot point on the ladder bar. They're a lever to plant the tire. Simply put, 4 links are unlimited ladder bars due to the extremes of the that very same pivot point that can be achieved. This hard to put into words but I'll try. Imagine the center of the axle and the pivot point of the ladder bar, the ladder bar point being stationary and the center of the radius, or more correctly the arc of axle travel. If the bars are up then it has to try to not only force the axle down but forward as well. It's a light car with no doubt a weight bias that's against it also. If the bars are down the initial suspension reaction will not only plant the tire easier but also push the car forward, ever so slightly like maybe 1/2-3/4" and help the vehicle's reaction time as a bonus. It takes a well balanced and severely over powered car to use ladder bars that are at level or up at the forward point. This will be even more apparent the longer the bars are (yours are 52!) and also take less up and down movement to see a change. I had new slicks that were broken in and ready to use. One of my racing bretheren were insisting I needed to raise my bars and I'd see a tenth or even more improvement in 60' time. Enuff was enuff so we did it on a test n tune night. I went from 1.40-1.42 60' times to an astounding 1.78-1.85 60' times. It didn't work. The car was heavy but it was 55-45 weight bias front to rear. At 3545# it needed all the help it could get at launch. To finish all this blabber, I'm suggesting that you drop the bars to just below level with the axle C/L, correct the pinion angle for that change, and give it a try. Your center of gravity (based on your avatar) isn't as high as it may appear visually, and the instant center might be going over the motor.
Alter your starting line rpm. Once you shock a tire too hard, the recovery period is longer than the time needed to have the torque from a blown engine power up against the converter stall speed and be flying.
If it was me I would lowwer the front ladderbar mount so the bar is at least level, but3-4* down would be better. Put a good set of adjustable shocks on the rear. I would bet that that would make a huge difference.
BTTT, i would like to hear more from the racers about the effects of these adjustments. Whether it be four bar or ladder bar, were still talking about the effects of that push. My model a runs a torque arm and now that I have the car running pretty quick, I would like to start dialing that in.
ran long 4links by chuck finders[when he was in socal backintheday]from 67till they bent 10yrs ago now running ladder bars ...now if not enough traction just run more tire/using 5.86 rear gears help
You say the front end does not rise and the rear tires just sit and spin. I think it sounds like it needs more front end lift to plant the rear tires. Try taking the front shocks off the car for one practice start and see if this helps.
I think you probably have a geometry issue. DW doesn't have any problem and he's still got a buggy spring in the rear with the nose way down.
His car looks as if it is working very well.. The rear tires are planted.. Thanks for all the suggestions, I need to get busy checkin it out, I will keep you guys posted as I go and try to post some pics..
There are many things that could contribute to your problem but I think the ladder bars are way too long. IMO, they should be about 1/3 of the wheelbase to work properly.
There are lots of books written on drag suspensions, so I don't really think we can cover it in one thread. If it were my car, I think I would put a shorter ladder bar on it, get some double adjustable shocks to play with on both ends and probably put a tighter converter in the transmission. I don't think a blower motor needs to get to 5000 rpms to start making power and it's probably shocking the tires hard enough to blow them off when it hits. How tight do you turn the engine. I'd think with a 5000 stall it would need to go at least 8000 to work right. Larry T
jack up the front end just to see if it hooks. what gear? what slick and how much air? how much air in the drag rad?
Lots of advice, most of it good. To me it sounds like your chassis is not transfering weight properly. If it were my car I'd loosen the front end with 90/10 shocks and making sure nothing in the suspendtion is binding, to get the car to rotate around the ladder bar instant center (this is the balance point between front and rear weight), thus transfering the chassis energy into a pendulum motion , planting the rear tires. That's me, but what do I know
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