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Mon Jul 18, 2005 10:18 pm

I have a sand rail that is used only on the street and I drag race it but don't know enough about suspension setup for drag. My car is less than 1500 pounds with me in it and it is very hard to get it to hook up. I have purchased DOT drag tires for it and things got worse because I took thirty pounds out of the rear with lighter rims. Anyway, if all goes right I have 1.25 sixty foot times but that rarely ever happens. Most of the time I go 1.76 or worse for my sixty foot time. I feel since my car is lowered and there is a tremendous amount of downward travel available, maybe that is eating up the force that should be lifting the front. I can purchase nylon strap limiters from places and they are made all different lengths. Do drag racers use down limiters? It would be real easy to mount them across the rear shocks to set up how far the rear arms drop down.

Tue Jul 19, 2005 4:47 am

swing or IRS?

Higher center of gravity = more wieght transfer

Tue Jul 19, 2005 6:12 am

Tue Jul 19, 2005 7:03 am

Ideally, to get traction in less then perfect conditions, you need some weight transfer. This typically comes in the way of rear squat and front extended up.
one thing i observe when one is trying to accomplish weight transfer is the lack of travel that the front has on some cars. an example of a lot of travel in the front woudl be mine.
http://vwtrendsweb.com/events/0407vwt_race02_z.jpg
one simple test would be put a jack under the front of your car and see how much the frotn end drops out. if it drops out, its that much less weight to get up.
I notice a big difference when i strap my front end up and how my car hooks up. (i strap up the front end for different reasons then traction)

In the rear, (only opinions since i have never worked with a really light car) Maybe you have too soft a suspension set up and not planting the tires good enough. Or too soft and too soft a shock to control the compression. Does your car squat and unload? if so, you need more shock.
typically in our heavy sedans that are really into dedicated racing, we start getting into larger torsion bars and adjustable shocks. the torsion bar size dictates how low the car squats at the line, and the shock keeps it from over extending the squat.
since your car is light, you shouldt need nearly as much torsion bar as say a car like mine.
ideally, the car needs to squat to xx height and hold it through first gear. maybe slightly elevating as you go through the full extent of the gear.

ultimately, maybe you just dont have enough tire to control that much power with that little weight.

Hop over to the shop talk forums and get into the speed and drag racing forum. there is a guy named Jim Henslin that races a rail and can probably give you a little more real life experience wiht a light car.

Tue Jul 19, 2005 4:34 pm

In my 1340 lb. street legal fiberglass Dunebuggy, I have a completly stock rear IRS suspension with some cheap oil filled shocks. This buggy will lift the front wheels (completly stock ball joint front-end with cheap oil filled shocks) 6'' off the ground with steel belted radial tires.

My 1225 lb. tube chassis Dunebuggy has swing axle rear with stock size torsion bars and Koni adjustable drag shocks. I have installed type III rear snubbers and have about 1" of rear wheel travel. No problems hooking up and running 12.20's on slicks.

What air pressure are you running in you DOT's?
What clutch & pressure plate are you using?

Tue Jul 19, 2005 10:01 pm

14lbs air pressure, Kennedy pressure plate, stock clutch.

Wed Jul 20, 2005 3:32 pm

When you say your buggy isn't hooking up, do you mean your tires are spinning, or do you mean your engine is bogging down?

Does your buggy wheelie real high?
Do you have wheelie bars?

Is it possible sometimes you are wheeling over the 60' beams and your rear tires are tripping the beams? If your 330' and 660' times are all consistant, the above is happening.

Wed Jul 20, 2005 6:30 pm

I get a much better 330 and 660 when I go 1.25 60foot times and I look beside me and see a tubbed out Blown V8 140+ drag car back about 2 or 3 feet from me when I launch that way (and he passes me like I'm sitting still later down the strip). My motor is very big, here is the specs: Brand new Pre Clearanced BugPack All Aluminum Case, CB Nitrited 84mm forged crank, H-Beam 5.7" Chevy journals, Total seal Gapless Second ring complete set, FK89 Camshaft, 1.4:1 Ratio Rockers, Scat Lifters, 42x37.5 Valves, 41mm Ports, 41mm (machined my self) Vents in dual Weber 48IDA's, .050 squish, 94mm Pistons Notched .100 (machined my self), 1 7/8" Custom A1 exhaust pointed up (Power Peaks at 7200 RPM) 180mains, Scat Serpentine Belt Kit, Scat Forged Flywheel, Scat Forged Straight Cut Cam Gears Degreed to the Cam Card @ .050" lift, Chromoly Pushrods, Hardened Lash Caps, Dual Valve Springs, EMPI Cast Iron Oil Pump, Scat lightened flywheel, Deep Sump with pickup brazed to stock oil pickup.
My clutch is probably too much for the weight of my car and maybe I am popping it too hard and breaking the tires free. With a light car once the tires are broken free it seems to burn out forever. I may wheele a little when I launch right but my total quarter mile time is one half to three quarters of a second faster at 1.25 than when I launch at 1.75+ 60 foot times. I really tell when the tires break free because it seems I am just sitting there in slow motion. I know my motor could easily loft the front end but I have never even noticed a wheele or at least hop if you want to call it. My girl friend says the wheels hop sometimes. My frame is totally custom and made out of 1 3/4" tubing and I did a good job of making sure the weight is forward for the most part but maybe too good of a job. My frame easily clears the IDA's where most non custom frames dont give room for them and are 1 1/2" tubing.
I've been thinking about this and looking at the car for ideas and I believe the strap idea is probably the wrong way to go. I am mulling over going with an 4" extended arm adjustable aluminum king/link front end with torshen bars instead of leafs to raise the front up more. Maybe a softer clutch too and 10psi of air in the rear tires. If I can get to where I can ride the clutch just a bit maybe it will keep gripping but the car shoots forward which makes your foot pop the clutch out a little harder and that is all it takes to break it free. Here is another catch. I have to launch at around 3k to 4k rpms becaust if I launch at 5k to 6k like my hard bodied bug racing friends my car will definately sit and spin ( never any wheel hop by the way). My 1.25 60 foot times were when I launched at 3400 rpms go figure. I have no complaints about my times or even motor power since I race with my belt on where the others take them off. Chuck said on the dyno the belt robbs 20 horsepower on his 205rwhp bug. A good note about launching at 3400 rpms is I never break the CV's. I could use closer gearing since my motor spins so high but I plan to set up a N2O system and will change my gearing after that since I don't know where I will be untill it is installed and I make a pass.

Thu Jul 21, 2005 4:04 am

Higher center of gravity=better wieght transfer.

as little as 1 or 2 inches will make the car more consistant.

A friend has a rail buggy with a almost stock 1600 and it yanks the front wheels 2-2,5 feet everytime. It is also raised up of the ground.

I wouild raise the car a couple of inches and see what happens

Thu Jul 21, 2005 5:02 am

If your spinning your tires you have a traction problem. In a 1500 lb buggy with that engine, you should be wheeling pretty high.Try letting some air out of your DOT's If your set at 14psi, go to 12 psi,and see what happens. Then 10 psi,

Thu Jul 21, 2005 10:49 pm

Will try dropping air. Also I think I will raise the back up to even the tire print on the ground. I am ordering a stock clutch 1200lb to see if it helps also. Hope tire hop doesn't start. I was thinking when the car goes the tires tilt out more and take away a lot of contact patch. The front is as high as a ball joint can go. I will start an extended king/link front end with aluminum beam soon but too busy with Packard resto. :roll:

Mon Jul 25, 2005 3:09 pm

Well I thought I had a 1700lb pressure plate and it turns out it is an old Kennedy 2300lb pressure plate. I ordered a 1700lb pressure plate and hopefully I will have more feel launching now. I am also pulling some weight out of the front end and welding in adjusters. New bushings in rear and hopefully something will fix my problem