Front end Alignment for Drag racing?

[BSL409]

I need to have the front end aligned on my 61 drag car I have installed 7/8” upper ball joint spacers and it looks like the front tires stick out just a little bit at the top what is recommended for racing on the caster camber? And we will align with the front end up in the air about a 1” or so Thoughts?

 

[1961BelAir427]

Very interesting topic. I wish I could remember what I've read on here about this over the years. I've always heard that the more caster the better for a drag car as it helps it to go straight and with less effort. I've also heard that it is hard to get more than a few degrees of caster without changing control arms and/or shafts.

 

[CDNpontiac409guy]

I aligned mine ( do my own ) with caster at high limit spec, Zero deg camber, just the very slightest toe in... all set at static height. The car is absolutely effortless to keep straight, especially at high speed, and goes through the traps 1 1/2 MPH faster than the engine HP is supposed to be capable of.
I don't think these cars have the "bump steer" characteristic in the font end, that many cars have ( I believe Chevelles may have quite a problem with this ). Essentially, the distance between the fulcrum points of the tie rod and the lower control arm, need to be very close.

 

[jim_ss409]

I don't know if it's right or not but I do it exactly the same as Aubrey described.
I can see where raising the car an inch to simulate the actual on track conditions might be even more accurate.
Some cars have bad bump steer, (wheels toe in or out as the suspension travels up and down) but I don't think it's much of an issue on these X frame cars so I wouldn't expect to see a huge difference in the alignment with the car raised an inch or so but it might be just a little more accurate.

 

[1961BelAir427]

Aubrey & Jim : Do either of ya'll add balast to the driver's seat to simulate your weight?

 

[Ishiftem]

I set mine with the front end up 1.5". O camber and as much caster as I can get in it. I plan on doing something with the bump steer on mine. These cars have a lot of bump steer. I have checked it and the toe changes well over a 1/4 inch as you raise the front end up. I don't recall if it toes out or in at the moment.

 

[Fathead Racing]

I copied this off another site.
For a track car or drag car, the pavement should be smooth so run stiffer springs and bigger sway bars both front and rear. Make sure your rear end is set up with traction control options like traction bars. Also for these cars, tire scrubbing is not really a concern so replace the performance alignment with an aggressive alignment (lots and lots of positive caster and lots of negative camber). As with the street profile, free up the suspension with parts like adjustable strut rods and roller spring perches.

 

[CDNpontiac409guy]

I thought about that, Brian, and looked at it this way... The engine torque tends to twist the car to the right a bit... shifting the weight slightly to the right. Also, as has been pinted out here, in reality the front end is probably slightly lifted for most of the run. For these reasons, I didn't add weight.

 

[Fathead Racing]

This is a good thread and it came up at just the right time of the year. Some of what I have been told years ago I can see don't hold any water.

 

[jim_ss409]

I copied this off another site.
For a track car or drag car, the pavement should be smooth so run stiffer springs and bigger sway bars both front and rear. Make sure your rear end is set up with traction control options like traction bars. Also for these cars, tire scrubbing is not really a concern so replace the performance alignment with an aggressive alignment (lots and lots of positive caster and lots of negative camber). As with the street profile, free up the suspension with parts like adjustable strut rods and roller spring perches.

I notice the first sentence says... "for a track car or drag car"
To me, I think a track car and a drag car have different priorities. You often want loose springs and shocks on a drag car where a track car would want a stiffer suspension.
They say negative camber, wheels tipped in at the top like this, / \ is a good thing for going around corners but I don't think it maters all that much on a drag car.
I think lots of caster is good on a drag car to help the steering feel stable and planted at high speeds and of course you want just a tiny bit of toe in. I usually aim for about 1/16" or 1/8" toe, next to nothing.

I didn't think these cars had a lot of bump steer but it looks like Ishiftem has actually measured it and it's quite a bit. It's not such a big deal if the bump steer adds a bit of toe in but if the wheels tend to toe out that can make the steering feel vague.

 

[Fathead Racing]

All good info, you couldn't fill a teacup with what I know about front end alignment on drag cars so this is great info for me. I have to split the difference tho, being a street strip car is always a compromise!

 

[real61ss]

I set mine with the front end up 1.5". O camber and as much caster as I can get in it. I plan on doing something with the bump steer on mine. These cars have a lot of bump steer. I have checked it and the toe changes well over a 1/4 inch as you raise the front end up. I don't recall if it toes out or in at the moment.

The car should toe in as the front of the car raises. The factory built in bump steer for safety reasons. When a car goes over a sudden hump or the crest of a hill the front end will rise, at the same time the front wheels toes in to make the car continue in a straight line. Without this bump steer the car would dart one way or the other. We discovered this many years ago running the round track car. Round track cars turn left, the left front tends to raise up as the car turns left, with the factory bump steer the left front wheel toes in as this side raises at the same time the right front is going down so the wheel is toeing out. In other words the driver is trying to turn left but the wheels are trying to turn right. To correct this the height of the inner tie rod end is raised or lowered. If I remember correctly, normally the inner tie rod end should be about the same height as the lower ball joint to create zero bump steer. But that was 30 years ago

 

[jim_ss409]

That's interesting stuff Tommy. It all makes sense.
A lot of guys run into extreme bump steer problems when they retrofit rack and pinion steering in an older car. It's a great upgrade if it's done right, but if the rack is mounted in the wrong place or if the pivot points on the rack aren't in the right place it can be a real problem.

 

[Don Jacks]

It also makes sense that our beloved x frames would "tow in" on lifting the front end due to the fact that they are "front steer" cars.That meaning that the steering linkage is in front of the crossmember.Ray's definately got me beat on this alignment stuff at a teacup full of knowledge ,Id consider myself lucky if mine would fill a thimble!Thanks for the lessons guys.

 

[Fathead Racing]

Back in the old days, (yeah I know) guys were messing with their front end settings all for just a little edge forgetting that the front end would go the other way on the shut down past the big end. I remember some pretty scary moments and we were only making high 14.00 or low 15.00 passes @ maybe 90 mph..

 

[Ishiftem]

I am all for getting rid of bump steer, not only for handling, but also for the car slowing tire scrub that happens when the toe goes out of spec. The rule of thumb floating around that locating the inner pivot at the same point as the lower control arm pivot eliminates bump steer is wrong and is also where a lot of people screw up when installing racks. It gets you close, but not exact. Also it should be noted that the arc of the steering link only needs to equal the arc of the suspension links in a relatively small area of travel for practical purposes. Even if they are not exact, a toe change of only a few thousandths is not really going to bother anything. here it is explained better than I could. http://www.longacreracing.com/technical-articles.aspx?item=8162&article=Bump Steer

 

[Ishiftem]

Back in the old days, (yeah I know) guys were messing with their front end settings all for just a little edge forgetting that the front end would go the other way on the shut down past the big end. I remember some pretty scary moments and we were only making high 14.00 or low 15.00 passes @ maybe 90 mph..

That is the reason I am against pre-loading the rear suspension whether it be with air bags or upper bars. It's ok if you are only moving 30 or 40 pounds, but for every action there is an equal and opposite reaction. What makes the car go straight on acceleration will make it dart the opposite way under braking.

 

[Fathead Racing]

I've been lucky so far. I have air bags and run 20 psi. In the pass. Side and 12 psi. In the driver side. Car launches dead level and no problems hauling it down at 115 mph. I run Wilwoods all the way around 90/10s up front and competition engineering out back.

 

[Fathead Racing]

Wish it would have occurred to me to take pictures, in 1966/67 I ran a 57 Chevy with a hot 283. I had spacers in the front springs and lowered the rear some how. I can't remember if we heated the rear springs or removed a leaf but I remember both options being on the table then. Had no idea what I was doing but I ran that at the strip. It looked like some of the better drag cars. Can't remember handling problems but it was kinda tight. Wasn't going very fast anyway. I do remember running some tires I pilfered off a Caddy, they were 900x14s. Still could chirp the tires in 2nd. Spark O Matic three speed shifter. The spacers in the front were like big aluminum screws that used a 3/8" drive ratchet handle to put in. I remember I was always losing them on the street.

 

[jim_ss409]

I've been lucky so far. I have air bags and run 20 psi. In the pass. Side and 12 psi. In the driver side. Car launches dead level and no problems hauling it down at 115 mph. I run Wilwoods all the way around 90/10s up front and competition engineering out back.

I've always been impressed by the way that car launches. It's a fully equipped street car with DOT legal tires and it's a lot heavier than a race only car, so it's impressive to see it launch so well.