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Yep I understand what you are saying. When I was running 11.0's I had 0 preload on the bars. I took them down to touch the springs and then tightened there. This worked the best for me. When I put preload to them I lost 60'.
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Yep I understand what you are saying. When I was running 11.0's I had 0 preload on the bars. I took them down to touch the springs and then tightened there. This worked the best for me. When I put preload to them I lost 60'.
Ours has a thickness of a nickel airspace between the spring and crossbolt (static w/driver). When footbraking, it closes up, probably when it is just put in 1st gear.
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Mine have a bunch of preload in them. Went 1.47 60' on a 255/60 drag radial yesterday.
Quote: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 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.
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Quote:Quote: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 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.
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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.
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Preload just touching the pin - go about 55 seconds in (1.444 60 ft)
http://www.youtube.com/watch?v=bofRAgenYrc&feature=plcp
This is with a .085 gap - go about 1:00 in (1.397 60 ft)
http://www.youtube.com/watch?v=SUL044AbhvQ&feature=plcp
The 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.
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Preload just touching the pin - go about 55 seconds in (1.444 60 ft)
http://www.youtube.com/watch?v=bofRAgenYrc&feature=plcp
This is with a .085 gap - go about 1:00 in (1.397 60 ft)
http://www.youtube.com/watch?v=SUL044AbhvQ&feature=plcp
The 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.
Did you launch at the same RPM on both runs? I didn't see the body separate at all on the second run
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CAL-TRAC SETTINGS
* Bottom hole – Softer Hit, moves IC forward
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Subscribing..
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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.
. I'm getting ready to tune my CalTracs again...first outing broke my spring perches and bent the rear housing. I almost have it back together again, but this time with a MO875 and a back brace. 
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Headed to Island in a bit. Gonna try with an air gap and just touching without preload. See how it goes. Hopefully I'll be able to get 4 or 5 runs in.
lots of good info shared on this thread though
Quote:Thanks for making it simple enough for ME to understand
As has been sort of implied... every combination is different.
Remember, the key to controlling tire spin, is finding a way to waste energy that would normally be used to overpower the traction to do something else. Sometimes it's body seperation, wheelies, spring deflection, etc...
What a caltrak is doing is managing that tire spin energy through spring deflection. If the spring is very stiff (lots of preload), there is no deflection left in the spring to "waste". If the car doesn't have the traction to use that energy, it will spin.
On the flip side, if the car already has enough traction and you let the spring "wind up" you're wasting energy that could be moving the car forward.
Ultimately on any given combonation, ALL of the energy eventually goes through the spring. It's the only thing that connects the body to the axle right? But what changing the preload does, is changes when that energy is applied. If the car is busy spending horsepower winding the spring up, it can't be spinning right?
That is basically how it works. Changing the bar location in the caltrac effects the above scenario. Putting the bar in the lower hole applys more pressure, at a slower rate to the front spring segment. Putting the bara in the upper hole applies less pressure at a quicker pace.
If the car doesn't spin, more pre-load will usually be quicker. The more pre-load you put in it, the stiffer the front spring segment becomes, and acts more like a ladder bar in the top hole at that point.
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Headed to Island in a bit. Gonna try with an air gap and just touching without preload. See how it goes. Hopefully I'll be able to get 4 or 5 runs in.
Gonna have to wait for another day. Started the car to pull it out of the trailer,.... clackity clackity clackity.... and #6 intake valve is broken and through the piston. No good.
