Pinion Angle

[outlawstreet21]

Does pinion angle play a big part in a 90 ford mustang mini stock on dirt?

To change the pinion angle which of the following would be best?

1. Shorten the upper trailing arms?
2. Lengthen the lower trailing arms?
3. Adjust lower trailing arm mounts (new plates with holes closer to front of car allowing axle to rotate)

Any answers would be helpful. Building a new car for my 12 year old.

[29 avenger]

where are you guys racing at

[jatchis]

I've seen more than a few sets of stock upper arms with a second set of holes drilled in them ahead of the original ones, but I've never messed with pinion angle myself.

[Dirtman29]

I did what jatchis said, thats the easiest way by far, drill new holes about 3/4" in front of the stock holes. Get your pinion angle in about 15 mins. tops (with a good drill and bit).

[millerlt3]

i run -5 degrees but i have adjustable uppers. I does help with foward bite

[drtlvr]

We cut the upper arms and overlap them 1 inch and weld them back. Gets the driveshaft away from the floor. I've heard people say it helps with forward bite but I've never been able to tell a difference.

[Headhunter]

Why so much pinion angle? I slotted my uppers about 1/4 inch and had 4 degrees and a little more if I needed it. Any more than 4-6 degrees and you are going to eat U joints and or break them and have the driveshaft try to tear the car up. That was also about the limit before you start fighting binds of the uppers because of mis-allignment.

[PitManArm]

I tried slotting the rear holes in the uppers to get a little different position, but it would move too much. Weld a couple of 1/2" flat washers about half a hole forward, or even three quarters of the hole forward and then drill thru to relocate the mount. The washers also provide a stronger mounting hole than the stock arm. I run the car with the trailing arm bolts double nutted and snug them so they still rotate. That way the arms pivot without binding.
If you make up a couple of pairs of arms with the holes moved to different areas, then you can switch them at the track for testing or even to dial the car into the track.

[drtlvr]

I have never measured the angle on mine, but the front of the pinion is about 1/4 lower in the front. We back the bolts off and double nut them too. If the bolts are tightened up with the axle hanging, when the car is on the ground the bushings will already be loaded (not good). Pitmanarm, can you tell a difference in pinion angle as far as handling?

[PitManArm]

Drtlvr: it definitely felt like it had more bite coming off. I found that using the arms I made that only covered half the original hole worked best. When I went further it seemed to bind the suspension at full travel when the track was rough. Because of the triangulation of the upper arms, I think they fought each other which caused a bind. It was subtle and not a sudden enough bind to cause it to go 'snap loose', but worked against the body roll.
Basically, on a dry slick track you would notice both the diminished body roll would hurt the car turning in, but the increased bite helped get back up to speed once you got it turned. On a track with lots of bite, these arms felt like they hurt the handling enough that I would switch back to stock length.
I seldom use them now, since the only track I run has wide sweeping corners and I am seldom off the gas. The body roll is too important for getting the car turned at speed and because I can keep so much momentum added bite isn't needed.
Like anything, it is a compromise of several factors and only trial and testing will tell what is best for you and your situation.
If you have a slick track with really tight corners, try just putting a shorter one in the right side. Very interesting results.