cal trac top hole vs bottom
#2108379
07/12/16 12:33 AM
07/12/16 12:33 AM
|
Joined: Nov 2004
Posts: 3,518 pacific northwest
Stroker Scamp
OP
master
|
OP
master
Joined: Nov 2004
Posts: 3,518
pacific northwest
|
I have always had the bar in the top hole and haven't changed it since I put the bars in, best 60' has been 1.44 foot braking just wondering what it would do in the bottom hole? anyone got any data?
footbrake N/A SB 408 Scamp 10.10 @ 132 street/strip 73 Duster 340 street strip 12.79 @ 105
|
|
|
Re: cal trac top hole vs bottom
[Re: Stroker Scamp]
#2108404
07/12/16 12:44 AM
07/12/16 12:44 AM
|
Joined: Feb 2007
Posts: 6,295 U.S.
moparniac
master
|
master
Joined: Feb 2007
Posts: 6,295
U.S.
|
How does going from top hole to bottom hole on the bar change instant center..
Last edited by moparniac; 07/12/16 12:45 AM.
Mopar Performance
|
|
|
Re: cal trac top hole vs bottom
[Re: moparniac]
#2108444
07/12/16 01:32 AM
07/12/16 01:32 AM
|
Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
I Live Here
|
I Live Here
Joined: Jul 2004
Posts: 19,318
State of confusion
|
How does going from top hole to bottom hole on the bar change instant center.. It doesn't BUT it does change the hit towards the harder side and I`m in the bottom hole w/just a tick of preload but not even a flat......
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
|
|
|
Re: cal trac top hole vs bottom
[Re: Stroker Scamp]
#2108660
07/12/16 12:57 PM
07/12/16 12:57 PM
|
Joined: Jan 2005
Posts: 3,635 Oakland, MI
dizuster
master
|
master
Joined: Jan 2005
Posts: 3,635
Oakland, MI
|
As mentioned the top/bottom hole does NOT change the instant center. On a leaf spring or ladder bar car, The Instant Center (IC) is defined by the single point in which the suspension is attached to the car (so in this case it’s the front spring eyelet).
What the top and bottom hole does in a caltrac is determine how quickly the front spring segment goes stiff. If you think of the front spring segment without a caltrac, the axle tries to rotate pinion up. There are two ways this motion can happen. Either the spring segment is completely and 100% stiff (like a ladder bar) and the pinion angle changes from body rise. Or in the case of a leaf spring, the body can stay still temporarily and the spring can flex.
The sole purpose of the caltrac is to keep the spring from flexing, and essentially create a short stiff ladder bar.
If you look at how the caltrac works, the front hanger rotates around the spring bolt. This is caused from the axle rotating, pushing the bar forward, which rotates the hanger down until it contacts the top of the spring. At this point the system is “solid” (except for some high force flexing that can occur).
When the bar is in the upper hole, it take less forward motion from the bar to make contact with the top of the spring. The lower hole requires a longer “push” of the bar before this can happen. The amount of gap/preload in the setup, and the upper/lower hole, all have to do with the “timing” of how quickly the system gets to full stiff, and how abruptly it happens.
The reason the bar in the upper hole (and more preload), hits the tire harder then a low bar hole/less preload, is because the system goes stiffer/sooner. Anything other then the upper hole and preload, is wasted motion of the suspension which will slow 60ft times down. The exception to that is if you don’t have a good enough tire/shock to hold that immediate tire hit, the lower hole/gapping can sometimes be a “Bandaid” and help with traction by launching the car softer.
If you look at any of the fast leaf spring cars, they almost ALWAYS have the bar in the upper hole. If your car isn’t spinning, it’s unlikely that the lower hole will help anything.
Also, being that it’s a foot brake car, you’re already preloading the pinion up anyway, so you’re likely getting close to full “Stiff” on the front spring segment anyway while you’re on the converter (depending how hard you’re on it).
If anything it looks like you could tighten up the front shocks a LOT if that’s an option for you. Comes up way to easy. Keeping the front down is the best way to improve the 60ft if you’re not spinning.
Hope that helps…
|
|
|
Re: cal trac top hole vs bottom
[Re: dizuster]
#2108882
07/12/16 06:39 PM
07/12/16 06:39 PM
|
Joined: May 2004
Posts: 12,418 Taxes & Virus's R-US, NY
Dragula
I Live Here
|
I Live Here
Joined: May 2004
Posts: 12,418
Taxes & Virus's R-US, NY
|
I have always run the upper hole on my Cuda, and it hits like a ladder bar car with a 1.38 60ft. No wind up like a typical SS sprung car, and then launch, it just hits....Never tried the lower hole, but as stated, all the fast leaf sprung cars are in the upper....I run just a slight amount of preload with my weight in the seat. Street driven and raced, with no changes and I like them.
|
|
|
Re: cal trac top hole vs bottom
[Re: Stroker Scamp]
#2108910
07/12/16 07:17 PM
07/12/16 07:17 PM
|
Joined: Jan 2004
Posts: 8,356 fredericksburg,va
cudaman1969
master
|
master
Joined: Jan 2004
Posts: 8,356
fredericksburg,va
|
Don't have my papers that came with bars in front of me now, but I'm almost sure that the design showed the instant center forward of the spring eye, and changeable by moving to different holes, the reason behind the design. A stock suspension four link, not a ladder bar. here is the diagram, changing from top hole to bottom hole moves the instant center, "the system emulates the four link system"
Last edited by cudaman1969; 07/13/16 01:32 AM.
|
|
|
Re: cal trac top hole vs bottom
[Re: justinp61]
#2109167
07/13/16 01:37 AM
07/13/16 01:37 AM
|
Joined: Nov 2004
Posts: 3,518 pacific northwest
Stroker Scamp
OP
master
|
OP
master
Joined: Nov 2004
Posts: 3,518
pacific northwest
|
Thanks for the info guys, gonna keep them in the same spot and maybe work on some better shocks in the future
footbrake N/A SB 408 Scamp 10.10 @ 132 street/strip 73 Duster 340 street strip 12.79 @ 105
|
|
|
Re: cal trac top hole vs bottom
[Re: Stroker Scamp]
#2109333
07/13/16 01:09 PM
07/13/16 01:09 PM
|
Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
I Live Here
|
I Live Here
Joined: Jul 2004
Posts: 19,318
State of confusion
|
I wouldn't, I'd try the lower hole and play w/that a bit since you want more and that COULD help ya instead of hitting it too hard. This is how we learn right............
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
|
|
|
Re: cal trac top hole vs bottom
[Re: Stroker Scamp]
#2109395
07/13/16 03:10 PM
07/13/16 03:10 PM
|
Joined: May 2006
Posts: 1,260 New Mexico
Adobedude
pro stock
|
pro stock
Joined: May 2006
Posts: 1,260
New Mexico
|
My Dakota HATES, HATES the upper hole, I tried it out for the 1st time Saturday, even with new slicks, spin city.
2001 Dodge Dakota 408 All Motor 11.27 @ 117.83 mph 2017 NM Mopar Challenge Series Champion.
|
|
|
Re: cal trac top hole vs bottom
[Re: Adobedude]
#2109397
07/13/16 03:11 PM
07/13/16 03:11 PM
|
Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
I Live Here
|
I Live Here
Joined: Jul 2004
Posts: 19,318
State of confusion
|
Some need/like the harder hit and some don't.............mine doesn`t.........
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
|
|
|
Re: cal trac top hole vs bottom
[Re: Stroker Scamp]
#2109524
07/13/16 06:24 PM
07/13/16 06:24 PM
|
Joined: Jan 2003
Posts: 13,404 Marion, South Carolina [><]
an8sec70cuda
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 13,404
Marion, South Carolina [><]
|
Back when my car ran in the mid 10s, it was doing a lot of bouncing through the 60' when using the top hole. Dropped it down to the bottom and it smoothed right out. Been in the bottom ever since.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
|
|
|
Re: cal trac top hole vs bottom
[Re: an8sec70cuda]
#2109555
07/13/16 07:28 PM
07/13/16 07:28 PM
|
Joined: Oct 2003
Posts: 11,686 W. Kentucky
justinp61
I Live Here
|
I Live Here
Joined: Oct 2003
Posts: 11,686
W. Kentucky
|
Back when my car ran in the mid 10s, it was doing a lot of bouncing through the 60' when using the top hole. Dropped it down to the bottom and it smoothed right out. Been in the bottom ever since. That's the same exact thing that my Dart did when the 340 was in it. Mine have been in the bottom hole ever since.
|
|
|
Re: cal trac top hole vs bottom
[Re: justinp61]
#2109665
07/13/16 11:14 PM
07/13/16 11:14 PM
|
Joined: Jul 2004
Posts: 19,318 State of confusion
Thumperdart
I Live Here
|
I Live Here
Joined: Jul 2004
Posts: 19,318
State of confusion
|
Wonder if it has to do w/the short 20" ft. segment...........I run the 25" myself and love it so far along w/more straight up n down shocks...........
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
|
|
|
Re: cal trac top hole vs bottom
[Re: Stroker Scamp]
#2109761
07/14/16 02:00 AM
07/14/16 02:00 AM
|
Joined: Dec 2007
Posts: 12,592 Great Neck,LI,new york
hemi-itis
I Live Here
|
I Live Here
Joined: Dec 2007
Posts: 12,592
Great Neck,LI,new york
|
I have always been in the bottom hole.Has anyome tried to increase the preload?? What happemed?? I was gunna try it,,,,,,
HEMI-ITIS has no cure. My condition is fully BLOWN!!
|
|
|
|
|