Not sure what all details are needed or what I can get you guys for now. I made 5 test hits last night with my S10.

First pass: 2800rpm launch, 0psi boost, 1.60 60' smooth sailing (Front and rear shocks set to 'loose') 15psi in rear
Second pass: 3000rpm launch, 2psi boost, broke loose after hooking (same shock setting) 15psi in rear
Third pass: 3000rpm launch, 2psi boost, tire shake 20 foot out (front shocks 2 clicks stiffer than 'loose', rear shocks at 7) 12.5psi rear
Fourth pass: 3200rpm launch, 5psi boost, tire shake 20 foot out (front shocks same as third, rear shocks at 9 'stiffist') 12.5psi rear
Fifth pass: 3400rpm launch, 7psi boost, tire shake 20 foot out, 1.46 60' (same shock settings as before just launched harder) 12.5psi rear

I run 275/60/15 M/T radials on 10 inch wheels. Final gear is 3.27 or something close to that, and TH-400 transmission with trans brake.
All launches were made off the trans brake. I do have some video which I will try to upload later, not sure what the quality will be like yet though. I do know that the first two launches were the hook and unload variety caused by the suspension being fully extended. Not sure how to correct the tire shake. More tire pressure? Harder launch? I can get up to 3800 on the trans brake/limiter but wasn't wanting to tear something up with all that bouncing around. Maybe go back to loosening the front shocks?

YES I do have over 5" of front suspension travel (I know that's one of the first things said when the words Caltracs and not hooking are used). I will be contacting them about this, but thought I'd ask the racers around here with turbo setups too.

Also for what it's worth, all passes had to be pedaled down track after shifting into second. Not sure if it was track quality or suspension related.

Total boost for these passes was between 7 and 10psi, hard to look at the gauge sideways on a short 1/8 mile track.

Thanks for any help. I searched around and didn't find anything specific to Caltracs so was hoping this might help other truck guys using them.

 

Here are some videos that might help

First video. Suspension is loose and you see the front lift, rear separate then break loose, characteristic of too loose shocks in rear



Second video. Tightened shocks up, looks like a good launch but I have to pedal it about 20 feet out.



Third video. Tried launching it harder with same shock settings as the second video

 

second video looks like it weight transfers well and holds the weight. It looks to me as though you are unloading the tires. Try to leave higher on the brake with the front shocks set stiff and rears loose. If the shocks are single adjustable ones as you describe, the bounce is a direct relation to rebound-- meaning if you set the rears to compress quickly they will rebound slowly. (70% bounce/30% rebound) or vice/versus. Hitting it harder should help the truck carry the weight transfer better having less power. Hard to believe but boost can be your friend in leaving harder under more boost. Ideally double adjustables would be the ultimate.
You can try posting on Yellow bullet's tire forum as Jason from MT will directly answer any tire questions.

 

Sounds good. I'm gonna try a few things differently next time out. Read up on the bullet a bit and it seems the M/T's like more pressure than I had in 'em. I had 12.5psi when it was shaking or hopping, not sure which. Gonna up that to 18 or so and launch it on up at 3600rpm. Also have some new Caltrac brackets that Travis sent me I need to put on. The truck currently has low profile brackets on the front which only have one hole. The hole on them is located the same as the top hole in the standard brackets that have 2 holes to use. I've talked to my chassis guy and he suggested the bottom hole will make the chassis be forced downward in the rear more on launch before pushing forward/up.

 

Yea , it seems like there isnt enough separation . I'm no expert , far from it , but I have cal-tracs ( homemade version ) on my truck and there is a considerable amount of separation . I'm using double adjustables on the rear .

Not the prettiest launch in the world , Front shocks adjustment was off . , but look at the rear wheel wells .

 

Not sure how you are doing your burnout. Ive seen and heard you gotta heat them up well to get good traction. If your doing a quick haze and pulling out they arent gonna work as good.

 

Try more air pressure in 1/4 to 1/2 psi changes. D/R's don't like low pressure.

 

Do you have rim screws?
How many?

 

Next time out might be a while, not sure. I was doing a first, second, third gear burnout with the limiter set at 4500 (3.23 final gear). Thought that might be enough wheel speed but i dunno. Tire sticking didn't seem to be the issue so much as keeping them planted.

New things I'm gonna try:

Front link set to lower hole; no preload
Tire pressure 18psi
Hold burnout in third gear for 2 secs before rollin out of it
Front shocks a little stiffer and rear set to full loose, see how much separation I can get