Leaf blows!!!
Registered User
Joined: Feb 2004
Posts: 1,041
Likes: 0
this is long but good reading. i saved this from a amc forum to help me get my 60 ft times down.
I talked to john calvert and here is what he said. He wants to know how much front/rear suspension travel the car has from tires hanging to the car resting on the ground with no shocks in place. He would like to see at least 5 inches of travel in the front and at least 4 inches in the rear. On the rearend of things, he wanted he wanted the caltrac bars in the upper hole for the most bite and between zero and 1/4 turn at the most pre-load with a person in the drivers seat and the car level. He wanted two leaf spring clamps in the rear of the leaf springs and and one in the front.
On my car in particular he suggested a 28 inch rear tire instead of the 27 inch I have now. I think a 28 might fit but it will be tight and tire growth may be an issue. He also suggested I get a looser converter and launch the car at a higher rpm to shock the suspension and plant the tires. Then he suggested a double adjustable shock in the front and rancho 9000's in the rear unless I could get "afford" a double ajustable shock in the rear. He mentioned getting HAL QA1's or Afco's.
So here is what I found when I was measureing. I had one seized shock on the drivers rear and my front shocks were too short. I measured the rear-end travel with the cal-trac bars in contact with rear springs. I am going to loosen them and do again. Here is what I emailed calvert.
4/21/05
AMX Front Suspension Measurements
All measurements taken from spindle to top of fender
Front shocks are stud/stud mount,
Driver Front:
With existing shocks, tires hanging 16 1/2 inches
With no shocks, tires hanging 19 inches
With no shocks, car on the ground 14 3/4 inches
Difference: 4 1/4 inches
Passenger Front:
With existing shocks, tires hanging 16 1/2 inches
With no shocks, tires hanging 19 inches
With no shocks, car on the ground 14 3/4 inches
Difference: 4 1/4 inches
With car on the ground, jack up the front crossmember until front tires will spin but skid on concrete 19 inches
Rear shocks are lower eye/top stud mount
Two Clamps on rear of spring/ One clamp on front of spring
Driver Rear:
With existing shocks, tires hanging 17 1/2 inches
With no shocks, tires hanging 18 inches
With no shocks, car on the ground 14 inches
Difference: 4 inches
Passenger Rear:
With existing shocks, tires hanging 17 1/2 inches
With no shocks, tires hanging 18 inches
With no shocks, car on the ground 14 inches
Difference: 4 inches
With the car on the ground and no shocks, pushing up and down on the front-end the responds like a basketball moves with no effort,,, the rear end took both hands but it does move.
Get a buddy to video the car on launch, and make sure it is a good side shot so you can see separation at both the front and back. Put some shoe polish marks on the tires so you can see tire spin. Then watch it on a frame by frame advance VCR.
Squating on the back is usually (not always) bad, cause that reduces load on the tires - they are being "pulled up" into the fenderwhel by the suspension. Depending on the car some separation is good. But with too much separation the rear suspension tops out, unloads the tires, and it spins, usually about 10 feet out. If that is happening, like ramblespud says, the instant center is too high or rearward.
Another big cause of this is too high a ride height. This reduces suspension travel so it is easier to top out, exaggerating the problem. The suspension need to be able to work. Another way to help this is stiffer rear shocks, I've used HD regular shacks here with good luck. I also try to have the lowest reasonable ride height, and maximise suspension travel front and rear. A small well thought out shock spacer can really help.
Get a video and really study it to see what is going on. Watch the gap between the tire and the fenderwell to judge suspension movement. You probably don't need to spend major money, just tune what you have. A 4.10 gear with a small tire a 3 speed tranny, and a good converter, is a LOT of rear wheel torque, so your tuning will have to be good.
If it's separating prior to even launching that's a problem. That means there is nothing left for the suspension to "work", and then 10 feet out it unloads, and that lifts the tires, less tire load, then tire spin. And no front end lift is a problem as well.
Where is your ride height? If it's high to begin with it's already used up suspension travel. With a small tire that's bad, usually a small tire 11 second car need some suspension travel.
Thoughts to look at:
- Lower ride height front and back
- Loosen front suspension for easier movement
- Remove front sway bar
- Move front suspension through travel to see what is limiting. Small shock length increase like 1/2" spacer under upper shock bushing and cut rubber bushings to still install nut. Not too much spacer, cause that will make control arm contact and "jar" suspension.
- Weaker front shocks
- Stiffer rear shocks
- Increased rear travel, again move suspension through it's travel and see what the limit is.
- Sounds like lower hole in Cal-Trac might be a good plan. The lower instant center changes how the suspension reacts to torque, should help reduce separation before you launch.
A couple other thoughts, cleaning the engine by giving it a shot actually does the opposite with the accelerator pump. It's better to bring the rpm up a bit and hold it for a few seconds. But this is all debatable using a 2 step.
With the too small tires for the et I always used to do stupid burnouts, in my car that's what worked. Everbody kept telling me to do less burnout, every time I tried it would bite me. But I've never tried to race on other than a slick, no idea what the Hoosier needs.
I've noticed a difference on burnout requirements with tire size, small tires seem to need more. Watch the stocker guy's on 9" slicks. And never ever ever do a dry hit, that's a sure way to kill traction. I used to do my burnout in high gear and come out of the box hard at full throttle to try to keep the tires from hooking, then stage instantly. If the tires hook the sprag in the converter has to instantly reverse and take a BIG load, and that's a real good way to break the converter. If you do this never let your converter guy see it, and you are taking your chances - you didn't hear this idea from me.
With all this I was able to bracket race a 10" slick into the low 10's with a stock suspension and a slapper bar. It would back to back to back 60's within .001, and would hook better than the guy's with a much bigger tire. My best 60' was 1.42 seconds. I did use a glide to take some low gear out of the car, I was serious bracket racing so I could not afford spin.
Jim: I have been running caltracs for 5 years, 3 years on an AMX and for two years on a Spirit. Here is the combo that has worked for me.
1) Use the softest front springs you can find and use 90/10 shocks on the quickest rise setting. You want the front end bouncy to allow weight transfer to the rear.
2) Use soft springs on the rear but not those that have lost their arch. You want the rear to rise as the front rises. Make sure your shocks have a long stroke so that they don't bottom out as they expand. Mine were too short and they would pull the rear wheels off the ground when they ran out of travel. I made some extensions that have worked for me. My rear shocks are heavy duty stockers.
3) I tried many different preloads on the caltracs and had a lot of traction problems until I realized that I had to put my weight equivalent in the driver's seat before making my preload adjustments. This made a lot of difference! My best settings are no preload on the right bar and a slight preload on the left bar (1/4 to 1/2 turn).
4) I use MT's with 10 PSI but I am hearing great stories about the Quick Time Pros. One of the hardest launching Chevelles uses them with great success.
I have probably forgotten several things and I don't profess to be an expert on caltracs but I have managed to get the cars into the low 11's with 1.55 60 footers. It was a slow trial-and-error process. The biggest error was probably too stiff springs on the rear.
John
Shocks: The more you spend, the better the results. The less you spend, the worse the results. Rear shocks are vital to control.
Cal-Tracs: Higher bar position equals harder hit. Lower position equals smoother hit. Less pre-load is best, excessive pre-load just binds up everything. All adjustments need to be made on level surface with driver in seat, just like the directions say. Rear-end moves counter clockwise as viewed from the rear on launch. Kind of makes sense to give more pre-load to the passenger side then doesn't it? Most Stockers (9" tire) run 1/2 pre-load on passenger side and zero on driver's side. These are settings for up to 9.80 E.T.'s with 9" slicks. I leave at 6800 RPM with a stick and have 3/4 on the passenger side and 1/4 on drivers side.
Check all corners for travel as mentiond in other posts.
Try without the two step until you get things figured out. If your rear is hunching up like you said then you're probably out of travel in the rear before you leave. That's why it spins initially.
I talked to john calvert and here is what he said. He wants to know how much front/rear suspension travel the car has from tires hanging to the car resting on the ground with no shocks in place. He would like to see at least 5 inches of travel in the front and at least 4 inches in the rear. On the rearend of things, he wanted he wanted the caltrac bars in the upper hole for the most bite and between zero and 1/4 turn at the most pre-load with a person in the drivers seat and the car level. He wanted two leaf spring clamps in the rear of the leaf springs and and one in the front.
On my car in particular he suggested a 28 inch rear tire instead of the 27 inch I have now. I think a 28 might fit but it will be tight and tire growth may be an issue. He also suggested I get a looser converter and launch the car at a higher rpm to shock the suspension and plant the tires. Then he suggested a double adjustable shock in the front and rancho 9000's in the rear unless I could get "afford" a double ajustable shock in the rear. He mentioned getting HAL QA1's or Afco's.
So here is what I found when I was measureing. I had one seized shock on the drivers rear and my front shocks were too short. I measured the rear-end travel with the cal-trac bars in contact with rear springs. I am going to loosen them and do again. Here is what I emailed calvert
So now I am going to measure for new shocks. I was told to get these measurements from Shock mount to shock mount. Loosen the caltrac bars to they are not touching anything.
1: measure with the tires hanging
2: with the car on the ground resting and race ready
For an example lets say the front suspension has 5 inches of travel. Would it be right to say I would want a shock with 7 inches of travel. Have 5 inches for shock extension and 2 inches for shock compression. In other when the car is on the ground the shocks would be mostly compressed??
Jim
73AMX: The hoosier quick time pros are more than capable of handling what I am dishing out to it. A real wrinkle wall is a better solution but I enjoy running in the street legal classes at least for the moment. I think I would keep them to a 100 passes and under. Then sell them for half price and buy new tires
Shocks: The more you spend, the better the results. The less you spend, the worse the results. Rear shocks are vital to control.
Cal-Tracs: Higher bar position equals harder hit. Lower position equals smoother hit. Less pre-load is best, excessive pre-load just binds up everything. All adjustments need to be made on level surface with driver in seat, just like the directions say. Rear-end moves counter clockwise as viewed from the rear on launch. Kind of makes sense to give more pre-load to the passenger side then doesn't it? Most Stockers (9" tire) run 1/2 pre-load on passenger side and zero on driver's side. These are settings for up to 9.80 E.T.'s with 9" slicks. I leave at 6800 RPM with a stick and have 3/4 on the passenger side and 1/4 on drivers side.
Check all corners for travel as mentiond in other posts.
Try without the two step until you get things figured out. If your rear is hunching up like you said then you're probably out of travel in the rear before you leave. That's why it spins initially.
Listen up, I ran the cal-tracs & spent a fortune on their shocks.....finally put the same set-up I ran in late 60's...comp enginering rear shocks set at 50/50 & front set at 80/20 ....mid 9's in the "POS"...pre-load on the cal-tracs at i/4 turn....let air pressure down till tires wrinkle under load....make sure you have enough rpm off line to wrinkle, or shock rear tires to make them hook....put bars in lower hole in front....Thanx,
I talked to john calvert and here is what he said. He wants to know how much front/rear suspension travel the car has from tires hanging to the car resting on the ground with no shocks in place. He would like to see at least 5 inches of travel in the front and at least 4 inches in the rear. On the rearend of things, he wanted he wanted the caltrac bars in the upper hole for the most bite and between zero and 1/4 turn at the most pre-load with a person in the drivers seat and the car level. He wanted two leaf spring clamps in the rear of the leaf springs and and one in the front.
On my car in particular he suggested a 28 inch rear tire instead of the 27 inch I have now. I think a 28 might fit but it will be tight and tire growth may be an issue. He also suggested I get a looser converter and launch the car at a higher rpm to shock the suspension and plant the tires. Then he suggested a double adjustable shock in the front and rancho 9000's in the rear unless I could get "afford" a double ajustable shock in the rear. He mentioned getting HAL QA1's or Afco's.
So here is what I found when I was measureing. I had one seized shock on the drivers rear and my front shocks were too short. I measured the rear-end travel with the cal-trac bars in contact with rear springs. I am going to loosen them and do again. Here is what I emailed calvert.
4/21/05
AMX Front Suspension Measurements
All measurements taken from spindle to top of fender
Front shocks are stud/stud mount,
Driver Front:
With existing shocks, tires hanging 16 1/2 inches
With no shocks, tires hanging 19 inches
With no shocks, car on the ground 14 3/4 inches
Difference: 4 1/4 inches
Passenger Front:
With existing shocks, tires hanging 16 1/2 inches
With no shocks, tires hanging 19 inches
With no shocks, car on the ground 14 3/4 inches
Difference: 4 1/4 inches
With car on the ground, jack up the front crossmember until front tires will spin but skid on concrete 19 inches
Rear shocks are lower eye/top stud mount
Two Clamps on rear of spring/ One clamp on front of spring
Driver Rear:
With existing shocks, tires hanging 17 1/2 inches
With no shocks, tires hanging 18 inches
With no shocks, car on the ground 14 inches
Difference: 4 inches
Passenger Rear:
With existing shocks, tires hanging 17 1/2 inches
With no shocks, tires hanging 18 inches
With no shocks, car on the ground 14 inches
Difference: 4 inches
With the car on the ground and no shocks, pushing up and down on the front-end the responds like a basketball moves with no effort,,, the rear end took both hands but it does move.
Get a buddy to video the car on launch, and make sure it is a good side shot so you can see separation at both the front and back. Put some shoe polish marks on the tires so you can see tire spin. Then watch it on a frame by frame advance VCR.
Squating on the back is usually (not always) bad, cause that reduces load on the tires - they are being "pulled up" into the fenderwhel by the suspension. Depending on the car some separation is good. But with too much separation the rear suspension tops out, unloads the tires, and it spins, usually about 10 feet out. If that is happening, like ramblespud says, the instant center is too high or rearward.
Another big cause of this is too high a ride height. This reduces suspension travel so it is easier to top out, exaggerating the problem. The suspension need to be able to work. Another way to help this is stiffer rear shocks, I've used HD regular shacks here with good luck. I also try to have the lowest reasonable ride height, and maximise suspension travel front and rear. A small well thought out shock spacer can really help.
Get a video and really study it to see what is going on. Watch the gap between the tire and the fenderwell to judge suspension movement. You probably don't need to spend major money, just tune what you have. A 4.10 gear with a small tire a 3 speed tranny, and a good converter, is a LOT of rear wheel torque, so your tuning will have to be good.
If it's separating prior to even launching that's a problem. That means there is nothing left for the suspension to "work", and then 10 feet out it unloads, and that lifts the tires, less tire load, then tire spin. And no front end lift is a problem as well.
Where is your ride height? If it's high to begin with it's already used up suspension travel. With a small tire that's bad, usually a small tire 11 second car need some suspension travel.
Thoughts to look at:
- Lower ride height front and back
- Loosen front suspension for easier movement
- Remove front sway bar
- Move front suspension through travel to see what is limiting. Small shock length increase like 1/2" spacer under upper shock bushing and cut rubber bushings to still install nut. Not too much spacer, cause that will make control arm contact and "jar" suspension.
- Weaker front shocks
- Stiffer rear shocks
- Increased rear travel, again move suspension through it's travel and see what the limit is.
- Sounds like lower hole in Cal-Trac might be a good plan. The lower instant center changes how the suspension reacts to torque, should help reduce separation before you launch.
A couple other thoughts, cleaning the engine by giving it a shot actually does the opposite with the accelerator pump. It's better to bring the rpm up a bit and hold it for a few seconds. But this is all debatable using a 2 step.
With the too small tires for the et I always used to do stupid burnouts, in my car that's what worked. Everbody kept telling me to do less burnout, every time I tried it would bite me. But I've never tried to race on other than a slick, no idea what the Hoosier needs.
I've noticed a difference on burnout requirements with tire size, small tires seem to need more. Watch the stocker guy's on 9" slicks. And never ever ever do a dry hit, that's a sure way to kill traction. I used to do my burnout in high gear and come out of the box hard at full throttle to try to keep the tires from hooking, then stage instantly. If the tires hook the sprag in the converter has to instantly reverse and take a BIG load, and that's a real good way to break the converter. If you do this never let your converter guy see it, and you are taking your chances - you didn't hear this idea from me.
With all this I was able to bracket race a 10" slick into the low 10's with a stock suspension and a slapper bar. It would back to back to back 60's within .001, and would hook better than the guy's with a much bigger tire. My best 60' was 1.42 seconds. I did use a glide to take some low gear out of the car, I was serious bracket racing so I could not afford spin.
Jim: I have been running caltracs for 5 years, 3 years on an AMX and for two years on a Spirit. Here is the combo that has worked for me.
1) Use the softest front springs you can find and use 90/10 shocks on the quickest rise setting. You want the front end bouncy to allow weight transfer to the rear.
2) Use soft springs on the rear but not those that have lost their arch. You want the rear to rise as the front rises. Make sure your shocks have a long stroke so that they don't bottom out as they expand. Mine were too short and they would pull the rear wheels off the ground when they ran out of travel. I made some extensions that have worked for me. My rear shocks are heavy duty stockers.
3) I tried many different preloads on the caltracs and had a lot of traction problems until I realized that I had to put my weight equivalent in the driver's seat before making my preload adjustments. This made a lot of difference! My best settings are no preload on the right bar and a slight preload on the left bar (1/4 to 1/2 turn).
4) I use MT's with 10 PSI but I am hearing great stories about the Quick Time Pros. One of the hardest launching Chevelles uses them with great success.
I have probably forgotten several things and I don't profess to be an expert on caltracs but I have managed to get the cars into the low 11's with 1.55 60 footers. It was a slow trial-and-error process. The biggest error was probably too stiff springs on the rear.
John
Shocks: The more you spend, the better the results. The less you spend, the worse the results. Rear shocks are vital to control.
Cal-Tracs: Higher bar position equals harder hit. Lower position equals smoother hit. Less pre-load is best, excessive pre-load just binds up everything. All adjustments need to be made on level surface with driver in seat, just like the directions say. Rear-end moves counter clockwise as viewed from the rear on launch. Kind of makes sense to give more pre-load to the passenger side then doesn't it? Most Stockers (9" tire) run 1/2 pre-load on passenger side and zero on driver's side. These are settings for up to 9.80 E.T.'s with 9" slicks. I leave at 6800 RPM with a stick and have 3/4 on the passenger side and 1/4 on drivers side.
Check all corners for travel as mentiond in other posts.
Try without the two step until you get things figured out. If your rear is hunching up like you said then you're probably out of travel in the rear before you leave. That's why it spins initially.
I talked to john calvert and here is what he said. He wants to know how much front/rear suspension travel the car has from tires hanging to the car resting on the ground with no shocks in place. He would like to see at least 5 inches of travel in the front and at least 4 inches in the rear. On the rearend of things, he wanted he wanted the caltrac bars in the upper hole for the most bite and between zero and 1/4 turn at the most pre-load with a person in the drivers seat and the car level. He wanted two leaf spring clamps in the rear of the leaf springs and and one in the front.
On my car in particular he suggested a 28 inch rear tire instead of the 27 inch I have now. I think a 28 might fit but it will be tight and tire growth may be an issue. He also suggested I get a looser converter and launch the car at a higher rpm to shock the suspension and plant the tires. Then he suggested a double adjustable shock in the front and rancho 9000's in the rear unless I could get "afford" a double ajustable shock in the rear. He mentioned getting HAL QA1's or Afco's.
So here is what I found when I was measureing. I had one seized shock on the drivers rear and my front shocks were too short. I measured the rear-end travel with the cal-trac bars in contact with rear springs. I am going to loosen them and do again. Here is what I emailed calvert
So now I am going to measure for new shocks. I was told to get these measurements from Shock mount to shock mount. Loosen the caltrac bars to they are not touching anything.
1: measure with the tires hanging
2: with the car on the ground resting and race ready
For an example lets say the front suspension has 5 inches of travel. Would it be right to say I would want a shock with 7 inches of travel. Have 5 inches for shock extension and 2 inches for shock compression. In other when the car is on the ground the shocks would be mostly compressed??
Jim
73AMX: The hoosier quick time pros are more than capable of handling what I am dishing out to it. A real wrinkle wall is a better solution but I enjoy running in the street legal classes at least for the moment. I think I would keep them to a 100 passes and under. Then sell them for half price and buy new tires
Shocks: The more you spend, the better the results. The less you spend, the worse the results. Rear shocks are vital to control.
Cal-Tracs: Higher bar position equals harder hit. Lower position equals smoother hit. Less pre-load is best, excessive pre-load just binds up everything. All adjustments need to be made on level surface with driver in seat, just like the directions say. Rear-end moves counter clockwise as viewed from the rear on launch. Kind of makes sense to give more pre-load to the passenger side then doesn't it? Most Stockers (9" tire) run 1/2 pre-load on passenger side and zero on driver's side. These are settings for up to 9.80 E.T.'s with 9" slicks. I leave at 6800 RPM with a stick and have 3/4 on the passenger side and 1/4 on drivers side.
Check all corners for travel as mentiond in other posts.
Try without the two step until you get things figured out. If your rear is hunching up like you said then you're probably out of travel in the rear before you leave. That's why it spins initially.
Listen up, I ran the cal-tracs & spent a fortune on their shocks.....finally put the same set-up I ran in late 60's...comp enginering rear shocks set at 50/50 & front set at 80/20 ....mid 9's in the "POS"...pre-load on the cal-tracs at i/4 turn....let air pressure down till tires wrinkle under load....make sure you have enough rpm off line to wrinkle, or shock rear tires to make them hook....put bars in lower hole in front....Thanx,
Jonathon
Joined: Dec 2003
Posts: 2,226
Likes: 0
comp eng. make these new slider bars, the make you leafs act like a 4 link, from what i was told they work really well.
__________________
SOME PEOPLE ARE ALIVE SIMPLY BECAUSE IT IS ILLEGAL TO KILL THEM
SOME PEOPLE ARE ALIVE SIMPLY BECAUSE IT IS ILLEGAL TO KILL THEM
Bottom Bulber
Joined: May 2004
Posts: 126
Likes: 0
Originally Posted by racingtheburg
Well Looking into the cal-tracs system that might work for me right now with the et drag 28.0-10.5 15's 
