dragster doesnt go straight

[RichardThiessen]

I recently bought a dragster and finally got my drivetrain all installed. I took it out for a shake down and all 3 launches I made with it pulled either to one direction or the other. I am new to driving a rail and there could be a possiblity that i wasn't properly lined up, but I assumed a rail would basically go pretty straight compared to a door car.

The front wheels are exactly straight and was wondering if I should set the toe-in about 1/8"-1/4"??? my one launch they said my right front wheel slightly lifted... not sure if this effected that launch. Its a hard tail dragster with a 650 hp 427 SBC with a glide and 4.11 gears

[mystic1582]

I'm assuming this is a rear engine rail w/a rack and pinion gear box. If you have never drove a race car w/a rack and pinion it is much more sensitive than a traditional steering box. There is less play. This may be part of the issue. What were the track conditions? What are the tires like? Since it goes one direction or the other it could be the track, steering, tires etc....Did this all happen in the same lane? Toe I would guess should be about zero....the front is rigid and steering has heims? Did you make sure the front wheels are not bent before checking toe? Did you check for any broken or cracked frame connections? Has it ever been repaired or halved?

[Matt@RFR]

We run a 125" hardtail altered with a rack. Not exactly the same thing, but 1/16" toe made for an unhappy driver. 1/8" is where we set it, and it goes straight as could be at 160 MPH.

And yes, the steering is touchy, especially on our short car, but it's nothing you should be worried about.

[Alan Roehrich]

Toe is not quite as important as caster. It is caster that is most responsible for the car going straight, especially at high speed. Usually if a car is too sensitive to toe, either there is a steering linkage problem, or it does not have enough positive caster. Even if the car is going to zero toe, if there is enough positive caster built in, the car will really want to go straight, that's what positive caster does. If it is going past zero toe, then it will want to wander, and might be twitchy.

If the car is picking up the right front wheel on the launch, there is likely some sort of problem with the chassis. Take it and have it checked by someone who knows what to do with it.

Usually, if the track is good, yet the car tries to drive to one side or the other at the launch, there is either a tire or a chassis problem, and it probably isn't in the front. Unless of course you're either staging crooked or staging with the front wheels turned instead of straight.

[Matt@RFR]

Alan brings up some good points. Another thing we learned about hardtails (atleast our car specifically), is that you can't baby them on the launch. If you don't hit the tires hard enough, it'll just unload and do some funky things. I wonder if that might be part of your problem. You're just like us in that you have relatively little power for a hardtail to work right, plus tall gears. For reference, we are at around 600hp and 1530 lbs with driver and 4.11's. We're going to 4.29's to see if that helps us out. You also need to let the tires spin a little bit. We are still working that part out, but it looks like if the wheelie bar is on the ground for more than 10" or so, and we get about 2 tire revolutions worth of spin, it works well. Our 60's are in the 1.18 range and dropping. I know a dragster isn't the same thing, so I'll just shut my mouth now.

[Alan Roehrich]

We ran a 650-675HP big block with a PowerGlide (ATI transbrake) in a 240" Hal Canode Top Alcohol dragster chassis. We also had a 900HP big block. The car hooked and went straight with no problems. I think it had a 4.11 gear, but it may have had a 4.30. With the small tires (10" Firestones), it would "bark" them when leaving. With the bigger 14/32 Goodyear tires, it would just dead hook and go.

Take the center section out and check that, too. You never know what someone may have done there.

[mystic1582]

Center section.....I drove a front engined dragster and it would sometimes decide to go dead left or right....Opened up the rear and it had a limited slip diff in it!!!!!!

[af2]

Richard, Have you measured the roll-out/ circumference of the slicks? And do you check the air pressure when both tires are in the shade? I see people adjusting pressure before the burnout and laugh because the tire in the sun always is higher. Then after the burn-out they stabilize and you will find the one you let air out of is low. Just a thought..

[RichardThiessen]

Thanks for all the suggestions, I'll try one thing at a time. I certainly hope I can figure it out. There's lots of things to check, so I'm not too disappointed yet. I'm definately going to check the center section and make sure they left the spool in it and didn't put an old limited slip diff in it LOL... that would piss me off.

[RichardThiessen]

After I started this thread I re-checked the toe-in... and the front wheels were not exactly 0 or straight, they were OUT 3/8". Not sure how I measured wrong that day... regardless I adjusted the toe-in so it was 1/8" IN. Anyway I finally got a chance to make it back to the track on Saturday and the car goes straight as an arrow now.

Not sure how the person before me ever drove the car down the track without hitting the wall

[miniv8]

Bending over the wheel assembly checking for things can put it all backwards in your head.

Good thing you got it figured out, and kept it off the wall.

thanks for the update.