Pinion Angle

[CDMBill]

I thought that was one our videos until I saw the ride height more closely.

[Russell]

I see the movement, is this an example of a good set up or somethimg that needs work?

[milner351]

Thanks Jeff - I will start with 5* down on the falcon, stock leaf springs / caltracs, automatic.

The goal of the power train angle is still ~3# down yes? (I have to build a trans mount)

So there will be a 2* angle at ride height.

[CDMBill]

There is a huge stickied Cal-Trac thread on the YB that is a great 'how to' read on setting up a leaf spring car with Cal-tracs. Up front there is summary list of initial settings and what does what. You don't need to read everything.

This essence is the front is every bit as important as the back, maybe more so, the keys being: lots of front travel with 5" seeming to be the starting point, and no binding in the front suspension. It has taken me a long time to get my front end really working well and required aftermarket upper and lower control arms as well as locating struts. With no spring in place I can cycle the front suspension easily through its travel with one hand. In the back the same rule applies, no binding. With the shocks removed you should be able to move the bdoy of the car up and down easily. On mine this was acheived with aluminum front spring eye bushings (they came with the Cal-trac spilt mono leafs) but you can retro fit stock springs, and Afco rear springs sliders.

With that as a basis you can have some assurance that your pinion angle and bar settings will be doing what you expect them to do at the hit. We used some little Flip cameras to record video of the suspension movements under load much like what you saw in Jeff's initial post.

The goal of all this is not just traction, but efficiency, transfering torque as directly to forward motion as possible. My launches are the most boring they've looked in years, no huge wheelie (like it could have), no big rear separation, no bounce. But, I'm now at a repeatable 1.40 60 ft. at 4150# 'race weight' on an average track and I think I'll get a very high 1.3X this weekend.

The other place to invest with Cal-tracs after time to get the details right is good quality double adjustable shocks. Afco's are the starting point IMHO.

[Barry Donovan]

is it just me or is straight on like asking to go in circles?

like a physics break is needed when laying down low..make the yoke work an angle...at highr speed, the car is on its own planting anyway.(they still lose it sometimes as we know)

I have a wild lesson with an IRS in a tin can. Straight on even made noise and a gyro hard feel. Live axle has it easy in some ways.

[JeffMcKC]

Thanks Jeff - I will start with 5* down on the falcon, stock leaf springs / caltracs, automatic.

The goal of the power train angle is still ~3# down yes? (I have to build a trans mount)

So there will be a 2* angle at ride height.

The ideal thing is to if making a trans mount, point the drive shaft right at the pinion, then and your down angle at the rear end. I see no reason on a leaf spring car to go under 1* under power, inverted is way worse than a degree of angle is.

[DanStokes]

At first I thought this thread said "Pinion Angel". Kinda like St. Christopher, I guess. Who you pray to to keep your rear end intact. Whichever rear end you want to it to refer to...

Dan

[CDMBill]

The ideal thing is to if making a trans mount, point the drive shaft right at the pinion, then and your down angle at the rear end. I see no reason on a leaf spring car to go under 1* under power, inverted is way worse than a degree of angle is.

Low ride height helps with this as does lowering the engine in the chassis. Lower may not help dynamic weight transfer but some times with the engine and trans lower in the car you can set them back substantially. Or so I hear.

When I installed the AFCO rear leaf spring sliders I was able t drop the rear ride height by an inch. It required a small pinion angle adjustment and went along with a slightly lower front ride height which I did to allow for more net available upward travel at the launch. Not exactly laying frame, but not stink bug either.

Dan, St. Expedite (seriously) for racing and successfully ending the trial runs, St Bartholomew for illnesses that might cause the other rear end problems. This is not religious in violation of the Turk rule, merely historical.

[JeffMcKC]

At first I thought this thread said "Pinion Angel". Kinda like St. Christopher, I guess. Who you pray to to keep your rear end intact. Whichever rear end you want to it to refer to...

Dan

I Pray to Samuel Colt, to protect my rear end and keep it exit only......

[ls7gto]

Thanks Jeff. I dont think there is enuff bandwidth to discuss instant centers LOL

[Deaf Bob]

:

I Pray to Samuel Colt, to protect my rear end and keep it exit only......

I make double sure with Smith and Wesson

[milner351]

The ideal thing is to if making a trans mount, point the drive shaft right at the pinion, then and your down angle at the rear end. I see no reason on a leaf spring car to go under 1* under power, inverted is way worse than a degree of angle is.

I suppose if I mess things up, there are always angled shims to fix it.

Is it a safe assumption to use tall jack stands on the hoist to simulate ride height? That way I could have free reign to adjust the height of the back of the trans, tack the mount in place, and tack the mounts to the axle.

I think the 5* down came from a discussion around welding the axle mounts on the bench.

[JeffMcKC]

Yes there are shims, I like using a drive on hoist or ride height on the ground myself and a magnet digital angle finder like this. I tried using jack stands before and its not the same, its not under the tire so you lose some working angle and if the car is not the same from to back it shifts weight so the ride height changes. ( I know I am being picky, but CARS like SEERED is only 1*)


http://www.harborfreight.com/digital...uge-95998.html

and use the 20% off coupon

it has a hold button. The needle ones are hard o read and stick the needle some times.

[JeffMcKC]

Thanks Jeff. I dont think there is enuff bandwidth to discuss instant centers LOL

Man can of worms,,,,, Pinion angles can go on the same way. Two camps, does it help hook or not, I am in the yes it does camp

[milner351]

I may have to put you on speed dial when I get set up to do this...