Car aims right under max acceleration
10-24-2011, 08:02 AM
#22
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I have checked the passenger side LCA bushing, and it looks good. I also checked to see if the rear end is square to the front wheels. Here's how I did that...
1) Put the car on jack stands (put under the subframe connectors, so the suspension is hanging unloaded)
2) Remove the wheels.
3) Put some tape on the floor under each wheel.
4) Put a level on the top two studs on a hub and level them.
5) Hang a plumb bob from the front of the rotor in the center of the bottom stud (which should be centered since the top two are level).
6) Mark on the tape where the plumb bob is hanging.
7) Repeat steps 4-6 for each wheel.
8) Measure front to back on each side and corner to corner.
My measurements showed that it was about 1/8" out from corner to corner and within 1/32" front to back. I also tried measuring to see how far out the rear end is from side to side (since I have stock PHB). I did the following...
9) Hang the plumb bob off the side of the rear quarter so that it hans directly in front of the center of the bottom stud (which is still centered with the level).
10) Mark the spot on the tap where the plumb bob is hanging.
11) Repeat 9-10 on the other side.
12) Measure between the dot measured off the brake rotor and the one measured off the quarter panel on both sides.
Using this method, it appears that the rear is about 1/8" towards the driver side. This would explain the fact that the corner-to-corner measurement was about 1/8" out while the front-to-back measurements were almost dead on.
If I measure from the brake caliper to the front of the wheel well, it measures about 1/4" different between the driver and passenger sides. I guess the sheet metal is just not an accurate thing to measure from. The car was wrecked once, but it was only cosmetic damage according to the dealership.
I haven't measured the tires yet. I have some string, but I never got around to it. I'll do that tonight.
1) Put the car on jack stands (put under the subframe connectors, so the suspension is hanging unloaded)
2) Remove the wheels.
3) Put some tape on the floor under each wheel.
4) Put a level on the top two studs on a hub and level them.
5) Hang a plumb bob from the front of the rotor in the center of the bottom stud (which should be centered since the top two are level).
6) Mark on the tape where the plumb bob is hanging.
7) Repeat steps 4-6 for each wheel.
8) Measure front to back on each side and corner to corner.
My measurements showed that it was about 1/8" out from corner to corner and within 1/32" front to back. I also tried measuring to see how far out the rear end is from side to side (since I have stock PHB). I did the following...
9) Hang the plumb bob off the side of the rear quarter so that it hans directly in front of the center of the bottom stud (which is still centered with the level).
10) Mark the spot on the tap where the plumb bob is hanging.
11) Repeat 9-10 on the other side.
12) Measure between the dot measured off the brake rotor and the one measured off the quarter panel on both sides.
Using this method, it appears that the rear is about 1/8" towards the driver side. This would explain the fact that the corner-to-corner measurement was about 1/8" out while the front-to-back measurements were almost dead on.
If I measure from the brake caliper to the front of the wheel well, it measures about 1/4" different between the driver and passenger sides. I guess the sheet metal is just not an accurate thing to measure from. The car was wrecked once, but it was only cosmetic damage according to the dealership.
I haven't measured the tires yet. I have some string, but I never got around to it. I'll do that tonight.
10-24-2011, 12:13 PM
#23
I can use a wheel stud at around 90* you can get closer if you use the step on the hub, thats more a fixed location. You got a good idea for anything being way off, but you should have had the weight on the suspension or do it with the tires on. and the car on blocks but you have to have some front floater plates. Loosen the shocks all the way and bounce the car helps too.
You have a PHR so with the rearend droped the PHR arcs and pulls the rear end over.
There is a hole on the bottem of the front rad supprt, thats right in the middle of my car. I use that to sqare things off. and plumb bob down the middle rear end, and chalk line down the middle. you can work off that. One side of the rear LCA body pocket is about 1/8 off then the other side, (one LCA sets longer) and one fender is about 1/8 off too (wider).
You have a PHR so with the rearend droped the PHR arcs and pulls the rear end over.
There is a hole on the bottem of the front rad supprt, thats right in the middle of my car. I use that to sqare things off. and plumb bob down the middle rear end, and chalk line down the middle. you can work off that. One side of the rear LCA body pocket is about 1/8 off then the other side, (one LCA sets longer) and one fender is about 1/8 off too (wider).
10-24-2011, 01:03 PM
#24
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I can use a wheel stud at around 90* you can get closer if you use the step on the hub, thats more a fixed location. You got a good idea for anything being way off, but you should have had the weight on the suspension or do it with the tires on. and the car on blocks but you have to have some front floater plates. Loosen the shocks all the way and bounce the car helps too.
You have a PHR so with the rearend droped the PHR arcs and pulls the rear end over.
There is a hole on the bottem of the front rad supprt, thats right in the middle of my car. I use that to sqare things off. and plumb bob down the middle rear end, and chalk line down the middle. you can work off that. One side of the rear LCA body pocket is about 1/8 off then the other side, (one LCA sets longer) and one fender is about 1/8 off too (wider).
You have a PHR so with the rearend droped the PHR arcs and pulls the rear end over.
There is a hole on the bottem of the front rad supprt, thats right in the middle of my car. I use that to sqare things off. and plumb bob down the middle rear end, and chalk line down the middle. you can work off that. One side of the rear LCA body pocket is about 1/8 off then the other side, (one LCA sets longer) and one fender is about 1/8 off too (wider).
Also, if I get an adjustable PHR, what's the best way to set it up? Center when sitting static? Do you set some sort of preload (for lack of a better term) so that it's centered with the suspension compressed?
10-25-2011, 09:30 AM
#27
I would set the rear end square using the wheel opening instead of trying to measure form the front tires. The front tires can easily be moved forward and back by adjusting the caster. If the rear was out of square when the alignment was done then the caster could be out as well.
I find it interesting that when you measured from the tire that you had 3/4" out of square and from the hub you only got 1/4". It could be that your tires are indeed that much different or just that you measured differently. I usually try to measure from the seam where the two panels meet at the bottom of the wheel arch. It is also important to check the ride height to make sure that you are not on a different part of the curvature of the tire.
As far as the direction of the tires. I would not have them remounted just to test one time. Just put the wheels on opposite sides and try it once to see if it pulls the other direction.
I find it interesting that when you measured from the tire that you had 3/4" out of square and from the hub you only got 1/4". It could be that your tires are indeed that much different or just that you measured differently. I usually try to measure from the seam where the two panels meet at the bottom of the wheel arch. It is also important to check the ride height to make sure that you are not on a different part of the curvature of the tire.
As far as the direction of the tires. I would not have them remounted just to test one time. Just put the wheels on opposite sides and try it once to see if it pulls the other direction.
10-26-2011, 08:09 AM
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I looked at the tires yesterday, and it appears that the passenger side is larger. I tested this in three ways. I realize they're not all exact but the point was to see if they all agreed.
1) I stood the tires up right next to each other and put a level across the top of them. The passenger side was taller.
2) I wrapped a string around each of them and compared the length. I did my best not to stretch the string, but stretching is possible. This showed the passenger side being bigger by about 3/8".
3) I drew a line down the sidewall of each tire using the string as a guide to make sure I had a good radius of the tire. I stood the tire up and held the level next to the line to make sure it was perfectly vertical. I marked that spot on the ground, rolled the tire 1 time, and repeated the process. This showed the passenger side tire being anywhere from 1/2" to 3/4" bigger.
I called M&H, and the guy there said that if you leave air in the tires while storing them, one can leak down faster than the other causing it to shrink relative to the other tire. He recommended that I do the following...
1) Let all the air out of the tires.
2) Leave them for a few days.
3) The next day I go racing, air the tires up to 30psi.
4) Immediately let the air out down to 10psi.
5) Check the rollout on them.
6) If the rollout is not the same, then air the smaller tire up to 30psi for about 1.5 hours.
7) Drop that tire back to 10psi and compare.
8) Repeat steps 5-7 until they're the same.
I'm hoping to take the car out Sunday and try this. Hopefully, that's my problem. I forgot to ask the guy if it would be okay to swap the tires and run them in the wrong direction. I don't think he would have said yes.
1) I stood the tires up right next to each other and put a level across the top of them. The passenger side was taller.
2) I wrapped a string around each of them and compared the length. I did my best not to stretch the string, but stretching is possible. This showed the passenger side being bigger by about 3/8".
3) I drew a line down the sidewall of each tire using the string as a guide to make sure I had a good radius of the tire. I stood the tire up and held the level next to the line to make sure it was perfectly vertical. I marked that spot on the ground, rolled the tire 1 time, and repeated the process. This showed the passenger side tire being anywhere from 1/2" to 3/4" bigger.
I called M&H, and the guy there said that if you leave air in the tires while storing them, one can leak down faster than the other causing it to shrink relative to the other tire. He recommended that I do the following...
1) Let all the air out of the tires.
2) Leave them for a few days.
3) The next day I go racing, air the tires up to 30psi.
4) Immediately let the air out down to 10psi.
5) Check the rollout on them.
6) If the rollout is not the same, then air the smaller tire up to 30psi for about 1.5 hours.
7) Drop that tire back to 10psi and compare.
8) Repeat steps 5-7 until they're the same.
I'm hoping to take the car out Sunday and try this. Hopefully, that's my problem. I forgot to ask the guy if it would be okay to swap the tires and run them in the wrong direction. I don't think he would have said yes.
