Cal Tracs and Instant Center????

3pedals · 07-22-2011, 01:04 PM

I have a set of slide-a-links on my 67 camaro, that I have modified to have a solid rod at the bottom to be like cal tracs. I have measured and roughly calculated using the main leaf as the upper link, that the IC is at about 78" in front of the rear axle, and about 5.5" off the ground. I beleive the neutral line on my car to be at about 9.5" off the ground at the same 78" in front of the axle.
1/2 the people say the cal-tracs dont effect IC, that the front spring eye IS the IC, and the other half say that YES the cal-tracks do effect how the rear suspension reacts to the "hit" just like altering a car's IC, and pivot point adjustments DO effect change.
What do you guys think????
If the cal-tracs do effect it, then where should I try to get the Instant Center. I know that I should have some anti-squat in the IC setting, but unsure where to attempt to position it, I have to modify the pivot points to acheive this so I am looking for advice.
Please dont tell me to spend $350 bucks and buy the CAL-TRACS, I would like too, but I have already wasted $350 on the slides inks, and I dont have alot of spare cash. I know I can modify the pivot points on the bars I have, to get them to work, I just need the technical advice about IC location.
If anyone has any other leaf spring setup advice, please share it
This on a stick shift 67 camaro, 6.0l LS, stock suspension, 28x 12.5 ET street bias. Car weighs 3425 roughly with me in it and has run a best of 11.39 @ 120 w/ a crappy 1.60 60 ft. I really need to improve traction to get it to 60ft better. Slow speed video of the launch shows the rear tires turning about 8-10 revolutions before the car even moves, and the rear does not separate untill after the tires start to bite.
Barrett

Phillip marvetz · 07-22-2011, 05:23 PM

Whatcha using for a clutch?

3pedals · 07-22-2011, 05:54 PM

11" Ram Single iron. it is at about 550lbs static right now, has no counterweight added to the CW levers.
I have tryed the static down so low to where the car wont even move when you let out the clutch, only when revs come up to about 1800, and it still BLOWS the tires away, even with launch rpms as low as 5000rpm. In fact the 60ft improved when I forgot to turn on the 2step, and left of the 7200 high side limiter lol, that was the 1.60, all others were 1.64 - and up, sometimes way up.
I am convinced the problem is in the rear suspension??????

Phillip marvetz · 07-22-2011, 06:05 PM

Have you tried another set of slicks? I have set that just wont hook for some reason. Switched them out and picked up big time.

3pedals · 07-22-2011, 06:18 PM

this is the second set of M/T et street bias 28x12.5's. 1rst set was an older pair, this set is NEW. EXACT results with both

TOSTO RACING · 07-22-2011, 09:46 PM

Put slicks on it et streets just won't cut it. You need a stiff sidewall slick.

Phillip marvetz · 07-22-2011, 09:55 PM

Ding, Ding, Ding, We have a winner!

Stiff sidewall slicks will be much better.

3pedals · 07-22-2011, 10:30 PM

Quote:

Originally Posted by TOSTO RACING

Put slicks on it et streets just won't cut it. You need a stiff sidewall slick.

OK , I plan to try that type tire next
Do you have any input on the original question - does the cal tracs change the effective Instant Center of a leaf spring suspension?

Phillip marvetz · 07-23-2011, 12:23 AM

I think your putting the cart in front of the horse.
It will be pretty hard to make your car work consistently with what you have. The traction bars will help but are not the answer.

Dinsdale · 07-23-2011, 02:01 AM

I think you're overthinking the suspension. As stated, you need real slicks. Maybe take some clutch out and lower your launch RPM. Myself, and others I know struggled with Cal Tracs and adjusted them all over the place with no improvement until the rest of the setup was right. The lower pivot hole theoretically moves the I/C farther out and softens the hit. The top hole hits the tire harder. Do you have adjustable rear shocks?

07-22-2011, 01:04 PM	#1
3pedals Junior Member Join Date: Oct 2006 Posts: 10 Likes: 0 Liked 0 Times in 0 Posts	Cal Tracs and Instant Center???? I have a set of slide-a-links on my 67 camaro, that I have modified to have a solid rod at the bottom to be like cal tracs. I have measured and roughly calculated using the main leaf as the upper link, that the IC is at about 78" in front of the rear axle, and about 5.5" off the ground. I beleive the neutral line on my car to be at about 9.5" off the ground at the same 78" in front of the axle. 1/2 the people say the cal-tracs dont effect IC, that the front spring eye IS the IC, and the other half say that YES the cal-tracks do effect how the rear suspension reacts to the "hit" just like altering a car's IC, and pivot point adjustments DO effect change. What do you guys think???? If the cal-tracs do effect it, then where should I try to get the Instant Center. I know that I should have some anti-squat in the IC setting, but unsure where to attempt to position it, I have to modify the pivot points to acheive this so I am looking for advice. Please dont tell me to spend $350 bucks and buy the CAL-TRACS, I would like too, but I have already wasted $350 on the slides inks, and I dont have alot of spare cash. I know I can modify the pivot points on the bars I have, to get them to work, I just need the technical advice about IC location. If anyone has any other leaf spring setup advice, please share it This on a stick shift 67 camaro, 6.0l LS, stock suspension, 28x 12.5 ET street bias. Car weighs 3425 roughly with me in it and has run a best of 11.39 @ 120 w/ a crappy 1.60 60 ft. I really need to improve traction to get it to 60ft better. Slow speed video of the launch shows the rear tires turning about 8-10 revolutions before the car even moves, and the rear does not separate untill after the tires start to bite. Barrett Last edited by 3pedals; 07-22-2011 at 04:27 PM.

07-22-2011, 05:23 PM	#2
Phillip marvetz Senior Member Join Date: Oct 2008 Location: Lynden ,WA Posts: 820 Likes: 0 Liked 3 Times in 3 Posts	Re: Cal Tracs and Instant Center???? Whatcha using for a clutch? __________________ 2009 V/SA Record Holder

07-22-2011, 05:54 PM	#3
3pedals Junior Member Join Date: Oct 2006 Posts: 10 Likes: 0 Liked 0 Times in 0 Posts	Re: Cal Tracs and Instant Center???? 11" Ram Single iron. it is at about 550lbs static right now, has no counterweight added to the CW levers. I have tryed the static down so low to where the car wont even move when you let out the clutch, only when revs come up to about 1800, and it still BLOWS the tires away, even with launch rpms as low as 5000rpm. In fact the 60ft improved when I forgot to turn on the 2step, and left of the 7200 high side limiter lol, that was the 1.60, all others were 1.64 - and up, sometimes way up. I am convinced the problem is in the rear suspension??????

07-22-2011, 06:05 PM	#4
Phillip marvetz Senior Member Join Date: Oct 2008 Location: Lynden ,WA Posts: 820 Likes: 0 Liked 3 Times in 3 Posts	Re: Cal Tracs and Instant Center???? Have you tried another set of slicks? I have set that just wont hook for some reason. Switched them out and picked up big time. __________________ 2009 V/SA Record Holder

07-22-2011, 06:18 PM	#5
3pedals Junior Member Join Date: Oct 2006 Posts: 10 Likes: 0 Liked 0 Times in 0 Posts	Re: Cal Tracs and Instant Center???? this is the second set of M/T et street bias 28x12.5's. 1rst set was an older pair, this set is NEW. EXACT results with both Last edited by 3pedals; 07-22-2011 at 06:21 PM.

07-22-2011, 09:46 PM	#6
TOSTO RACING Senior Member Join Date: May 2007 Location: DRAGSTRIP Posts: 808 Likes: 594 Liked 471 Times in 136 Posts	Re: Cal Tracs and Instant Center???? Put slicks on it et streets just won't cut it. You need a stiff sidewall slick. __________________ 5664 AA/SA 1970 NOVA

07-22-2011, 09:55 PM	#7
Phillip marvetz Senior Member Join Date: Oct 2008 Location: Lynden ,WA Posts: 820 Likes: 0 Liked 3 Times in 3 Posts	Re: Cal Tracs and Instant Center???? Ding, Ding, Ding, We have a winner! Stiff sidewall slicks will be much better. __________________ 2009 V/SA Record Holder

07-23-2011, 12:23 AM	#9
Phillip marvetz Senior Member Join Date: Oct 2008 Location: Lynden ,WA Posts: 820 Likes: 0 Liked 3 Times in 3 Posts	Re: Cal Tracs and Instant Center???? I think your putting the cart in front of the horse. It will be pretty hard to make your car work consistently with what you have. The traction bars will help but are not the answer. __________________ 2009 V/SA Record Holder

07-23-2011, 02:01 AM	#10
Dinsdale Member Join Date: Oct 2004 Location: Canada Posts: 313 Likes: 0 Liked 6 Times in 2 Posts	Re: Cal Tracs and Instant Center???? I think you're overthinking the suspension. As stated, you need real slicks. Maybe take some clutch out and lower your launch RPM. Myself, and others I know struggled with Cal Tracs and adjusted them all over the place with no improvement until the rest of the setup was right. The lower pivot hole theoretically moves the I/C farther out and softens the hit. The top hole hits the tire harder. Do you have adjustable rear shocks? __________________ Dale Posnick