Toe-in changes when front end lifts at track
I've had an issue sometimes where my avatar car (72 Demon) pulls to the left at the dragstrip when I launch it or when going down the track. After reviewing several videos of the car, you can clearly see the car leaving straight then veering left shortly after. You can also see the tire tracks when it does this. It's a manual steering car and when I instinctively correct it, the car can go into an over-gained condition where the back-end and front end start "porpoising" horizontally and you feel like the back end wants to swap places with the front! I'm no hero so I immediately abort the run and the car settles down just fine. Here's an example where you can see the tire tracks after it left the line and went left. The camera was not perfectly behind the car but you can see what I'm describing idea pretty well:
The car's best 60' is a 1.496 and 1/8 mile is a 7.01 (1/4 mile 11.19) The videos showed me something quite interesting. This car has considerable body separation on the launch (car has a CalTrac split mono rear and 73 disc brake setup up front). It pulls the LF tire up to maybe an inch or so and the RF will sometimes see daylight and sometimes not. But the video shows that, on the launch, when the front end lifts and the RF tire swings down from the body, the act of it dropping down makes the tie rod end "act" too long which causes the tire to toe in (since the tie rod is on the rear side of the wheel) and essentially drives the car to the left. The suspension pieces (bushings, ball joints, etc) are essentially all new and there is no looseness to the wheel when I have it in the air on a jack and try to jostle it. It seems like simple geometry that when the tire swings down, the tie rod end would be too long and cause this toe-in affect. FWIW, the LF tire does not seem to do this similar thing in reverse as much hence why the car drives left. I haven't determine why sometimes it drives harder left than others but suspect it may be dependent on how high it pulls the front end and whether the RF tire is down more compared to the LF one. Note that this tendency to drive left can also occur a bit down the track (say 100' out) as the front end is still lifted/body separation is still quite a bit at that point.
So given this, I'm sure someone has already overcome this or uses some front end alignment trick. When I set the car up, I used the Skosh chart for alignment specs for "Max performance street" as I use the car on the street some too. Today I worked on it in the driveway trying different toe settings and camber settings. But if I make the RF wheel point straight ahead with them just touching the ground (like just after it leaves and settles back down), it is toed out when sitting at rest or idling around in the driveway/normal driving.
Is this just a limitation that you live with and set the tie rod for the track with the wheels up (shorten it several turns) and then lengthen it for normal street driving or ??? Looking to the braintrust for some experience and schooling for me. Thx!!
I've had an issue sometimes where my avatar car (72 Demon) pulls to the left at the dragstrip when I launch it or when going down the track. After reviewing several videos of the car, you can clearly see the car leaving straight then veering left shortly after. You can also see the tire tracks when it does this. It's a manual steering car and when I instinctively correct it, the car can go into an over-gained condition where the back-end and front end start "porpoising" horizontally and you feel like the back end wants to swap places with the front! I'm no hero so I immediately abort the run and the car settles down just fine. Here's an example where you can see the tire tracks after it left the line and went left. The camera was not perfectly behind the car but you can see what I'm describing idea pretty well:
The car's best 60' is a 1.496 and 1/8 mile is a 7.01 (1/4 mile 11.19) The videos showed me something quite interesting. This car has considerable body separation on the launch (car has a CalTrac split mono rear and 73 disc brake setup up front). It pulls the LF tire up to maybe an inch or so and the RF will sometimes see daylight and sometimes not. But the video shows that, on the launch, when the front end lifts and the RF tire swings down from the body, the act of it dropping down makes the tie rod end "act" too long which causes the tire to toe in (since the tie rod is on the rear side of the wheel) and essentially drives the car to the left. The suspension pieces (bushings, ball joints, etc) are essentially all new and there is no looseness to the wheel when I have it in the air on a jack and try to jostle it. It seems like simple geometry that when the tire swings down, the tie rod end would be too long and cause this toe-in affect. FWIW, the LF tire does not seem to do this similar thing in reverse as much hence why the car drives left. I haven't determine why sometimes it drives harder left than others but suspect it may be dependent on how high it pulls the front end and whether the RF tire is down more compared to the LF one. Note that this tendency to drive left can also occur a bit down the track (say 100' out) as the front end is still lifted/body separation is still quite a bit at that point.
So given this, I'm sure someone has already overcome this or uses some front end alignment trick. When I set the car up, I used the Skosh chart for alignment specs for "Max performance street" as I use the car on the street some too. Today I worked on it in the driveway trying different toe settings and camber settings. But if I make the RF wheel point straight ahead with them just touching the ground (like just after it leaves and settles back down), it is toed out when sitting at rest or idling around in the driveway/normal driving.
Is this just a limitation that you live with and set the tie rod for the track with the wheels up (shorten it several turns) and then lengthen it for normal street driving or ??? Looking to the braintrust for some experience and schooling for me. Thx!!