|
Re: Foot braking with Caltracs and preload?
[Re: fig426]
#1249004
06/11/12 10:54 AM
06/11/12 10:54 AM
|
Joined: May 2007
Posts: 1,443
Maryland
Dads426
pro stock
|
pro stock
Joined: May 2007
Posts: 1,443
Maryland
|
I don't think so. The preload on your setup is nothing compared to the load imposed when footbraking. We leave between 1500-2800 rpm and at the higher rpms the car actually lifts in the rear before launch.
2012 422 Allstars NSS Champion
2013 422 Allstars NSS Champion
2014 422 Allstars NSS Champion
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: fig426]
#1249008
06/11/12 12:31 PM
06/11/12 12:31 PM
|
Joined: Oct 2003
Posts: 2,537
PORT ALBERNI , BC., CANADA
superwrench
master
|
master
Joined: Oct 2003
Posts: 2,537
PORT ALBERNI , BC., CANADA
|
My car has the Caltrac's preloaded ONLY on the right side. 2 flats on the right and just touching on the left. I bring up the RPM on the footbrake to 2400 at the beams....any more than that seems to take away 60' as the rear will start to rise a bit. This is with a 4600 convertor and 3700# race weight and car will run 1.46 60's. My assumption is that "torquing up" the suspension is defeating the purpose of Caltracs. 
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: StealthWedge67]
#1249010
06/11/12 01:00 PM
06/11/12 01:00 PM
|
Joined: Jan 2003
Posts: 6,266
Renton Washington
Triple Threat
master
|
master
Joined: Jan 2003
Posts: 6,266
Renton Washington
|
Mine have a bunch of preload in them. Went 1.47 60' on a 255/60 drag radial yesterday.
-Dustin
67 Dart, 9 second, 392" G3 Hemi
68 Barracuda 340 F/SA
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: fig426]
#1249012
06/11/12 01:17 PM
06/11/12 01:17 PM
|
Joined: Jan 2003
Posts: 6,266
Renton Washington
Triple Threat
master
|
master
Joined: Jan 2003
Posts: 6,266
Renton Washington
|
2500rpm off the footbrake. Converter flashes to about 4800
I haven't experimented with opening up the preload at all. Generally the car seems to hook well and goes straight so I haven't felt the need.
-Dustin
67 Dart, 9 second, 392" G3 Hemi
68 Barracuda 340 F/SA
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: Crizila]
#1249014
06/11/12 03:03 PM
06/11/12 03:03 PM
|
Joined: Jan 2004
Posts: 2,103
East Coast, NJ
fig426
OP
top fuel
|
OP
top fuel
Joined: Jan 2004
Posts: 2,103
East Coast, NJ
|
Quote:
Quote:
I'm running Caltracs in a 11.0 foot brake car. When setting up the Caltracs, they are preloaded against the spring about 1/4 turn. When foot braking, bringing the rpm up, "preloading" the chassis, doesn't that negate anything the Caltrac preload is doing? Don't the Caltracs get preloaded when it's footbraked with rpm's? I know what I'm trying to ask, I just hope the question acually makes sense. 
The harder you are up against the convertor the more the preload on the chassis ( diff nose goes up, driving the Caltrac bars forward and the cross pin in to the spring ). I believe they recommend 2 flats of preload to start with - cross bar touching leaf + 2 flats on the bars. Thats what I have been running, but this Saturday I am going to try 0 preload on the bars ( or might even go a little loose ) to see what happens. I'm hoping to get the car to sit down in the back a little more for some improved weight transfer .
I'm going to try that Wednesday night. Back out the preload, and preload it by coming up on the converter a bit. I'm curious if that will help my 60 foot. My 60 is a best of 1.55, launching from an idle, and is a 1.59 when I get up on the converter. My mph is 123, so I think if I get my 60 down to where I think it should be, I should see high 10's consistently. Best yet is a 10.966 at 124mph with a 1.55 60.
Chris from New Jersey
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: superwrench]
#1249015
06/11/12 03:24 PM
06/11/12 03:24 PM
|
Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
Too Many Posts
|
Too Many Posts
Joined: Jan 2003
Posts: 27,421
Balt. Md
|
Quote:
My car has the Caltrac's preloaded ONLY on the right side. 2 flats on the right and just touching on the left.
I bring up the RPM on the footbrake to 2400 at the beams....any more than that seems to take away 60' as the rear will start to rise a bit.
This is with a 4600 convertor and 3700# race weight and car will run 1.46 60's.
My assumption is that "torquing up" the suspension is defeating the purpose of Caltracs.
This is good info for me as our cars run about the same and weigh about the same as mine weighs just over 3700 lbs. I just use SS springs and wonder if its worth me going to Caltracs later. My best is 10.76 in the 1/4 and 6.83 in the 1/8 and my best sixty is 1.50. I see your Challenger has gone a 1.46 with the Caltracs ? Ron
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: 383man]
#1249016
06/11/12 09:19 PM
06/11/12 09:19 PM
|
Joined: Mar 2008
Posts: 553
Kentucky
clovis
mopar
|
mopar
Joined: Mar 2008
Posts: 553
Kentucky
|
I have just finished doing some experimenting with preload on the Duster. Our first passes was with .085 (we used an old brake adjuster feeler gauge) of clearance between the spring and pin, with me in the car. With the air gap the car would pick up the front end. When we set the pin on the spring with me in it, it would not pick up up the front end and the rear body separation during staging was very pronounced. I was trying to bring it out at about 3,300 rpms. The 60ft is a tad better with the gap. It left me with the impression that there is a difference in pressure and hit. The pressure on the tire is greater with the preload, but there seems to be a bigger "hit" with the gap.
We then swapped out the old six cylinder springs for the Caltrac monos and went to the top hole and a gap. This gave us the lowest and most consistent 60ft we have had with the car and this was leaving at 1,700 rpm. I wanted to see if letting the converter swing a bit would hurt or help. Next time out we will try coming out about 3,500-4,000 (whatever the brakes will hold) and see what that does to the 60 ft. In the past the higher launch rpm has created a better 60ft. I think it also has a lot to do with getting the motor in its happy place. With the 590 cam I think the 3,500 mark is a more preferable spot than 1,700. I try to get my videos posted so you can see, but for the time being, here is one of last passes with the monos.
Last edited by clovis; 06/11/12 09:20 PM.
'75 Plymouth Duster
Phase I 451 906/590/2-660 10.75/126
Phase II 451 Stage VI/590/1050 9.82/135
Phase III 383 906/Victor-Pump gas 11.30/119
"For by grace you have been saved through faith. And this is not your own doing; it is the gift of God,"
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: 383man]
#1249017
06/11/12 09:34 PM
06/11/12 09:34 PM
|
Joined: May 2009
Posts: 511
Temperance, MI
68 HEMI GTS
mopar
|
mopar
Joined: May 2009
Posts: 511
Temperance, MI
|
i set mine with 2 flats pre-load with some one in the car. lower hole. leave right at idle or a little bit above video link http://youtu.be/tBwyPmOzqBQ
68 Dart GTS "HEMI" 10.30 @ 131 pump gas street car 3780#
69 Roadrunner 511 six pack 10.92 drive to track street car
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: 68 HEMI GTS]
#1249018
06/11/12 11:12 PM
06/11/12 11:12 PM
|
Joined: Jun 2004
Posts: 148
Montgomery, PA
dodge340dart
member
|
member
Joined: Jun 2004
Posts: 148
Montgomery, PA
|
I ran the 002/003 Super Stock springs on my Dart for years with decent success; I changed to the Caltrac mono-springs and Rancho shocks and the 60ft times were only moderately quicker but so much more consistent especially on marginal track surfaces or extreme track temperatures.
Here are some notes I have taken with the Caltracs:
CAL-TRAC SETTINGS
* Top hole – Hardest Hit (start here)
* Bottom hole – Softer Hit, moves IC forward
* More Pre-load, Softer Hit
* Less Pre-load, air gap, harder hit
* If car pulls to the right add a quarter turn of pre-load to the right bar and visa versa.
* Set front shocks soft
* Set rear shocks on #5, if car wants to porpoise go to 6 or 7 (harder).
* If car spins, needs harder hit
* The front end travel must be at least 5"
* Too much wheel stand…. Softer hit, restrict front travel
My '69 Dart weights 3033lbs with me in it, I run the bottom hole most of the time with 1 flat of preload on the driver side and 2 flats on the passenger side. I run the shocks on "3" most of the time as well. The Dart has a best of 1.500 60ft, 7.128 1/8th, and an 11.359 1/4. The car 60fts very good for the ET it runs. The rear of the Dart (or any RWD Mopar) will always raise during acceleration regardless of the hole selected due to the relation of the IC to the neutral line and the center of gravity of the car. I launch at 3000-3500RPM depending upon the track temperature and the tires are 26"x9" Hoosiers.
Getting the Caltracs to work is a combination of front suspension, rear suspension, tires, weight placement/tranfer, launch RPM, track preparation/temperature, transmission/drivetrain starting line ratio, engine tune and a bunch of other variables that can all impact the launch and the run.
2011 & 2012 Beaver Springs Dragway Outlaw Street Champion
2012 BSD Friday Street Racer Driver of the Year
3-time Jr. Stock Eliminator
2-time Mean Street Eliminator
'69 340 Dart 1.500 60ft, 11.359et, 117.08mph
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: dodge340dart]
#1249019
06/12/12 07:46 AM
06/12/12 07:46 AM
|
Joined: Mar 2008
Posts: 553
Kentucky
clovis
mopar
|
mopar
Joined: Mar 2008
Posts: 553
Kentucky
|
Preload just touching the pin - go about 55 seconds in (1.444 60 ft) http://www.youtube.com/watch?v=bofRAgenYrc&feature=plcpThis is with a .085 gap - go about 1:00 in (1.397 60 ft) http://www.youtube.com/watch?v=SUL044AbhvQ&feature=plcpThe mono's have helped tremendously with the body separation. The separation is so bad with the 6 cylinder springs the shocks could not control it. If I tried going above a 7 on the Rancho it would unload the rear. With the mono we are now at 8 and will try 9, but the firmer spring seems to help control the separation enough that the shock can do its job.
'75 Plymouth Duster
Phase I 451 906/590/2-660 10.75/126
Phase II 451 Stage VI/590/1050 9.82/135
Phase III 383 906/Victor-Pump gas 11.30/119
"For by grace you have been saved through faith. And this is not your own doing; it is the gift of God,"
|
|
|
Re: Foot braking with Caltracs and preload?
[Re: Crizila]
#1249022
06/12/12 07:50 PM
06/12/12 07:50 PM
|
Joined: Mar 2008
Posts: 553
Kentucky
clovis
mopar
|
mopar
Joined: Mar 2008
Posts: 553
Kentucky
|
No, the first is about 3,000 and the second is about 2,000. The two are not really apples to apples on rpm nor springs/shocks, as the second video is on the monos with the shocks set at 8. The first is 6 cylinder springs/shocks set at 6 and spring just touching the pin. I will try to post a video with the old springs and a gap (no pre-load) to get a truer apples to apples. Even with the same spring/shocking setting and rpm, the difference in separation prior to launch is pretty significant. The preload really seems to make a difference.
'75 Plymouth Duster
Phase I 451 906/590/2-660 10.75/126
Phase II 451 Stage VI/590/1050 9.82/135
Phase III 383 906/Victor-Pump gas 11.30/119
"For by grace you have been saved through faith. And this is not your own doing; it is the gift of God,"
|
|
|
|
|
