Looking to pick up a bunch of reaction time on a heavy footbrake truck and have a few ideas I've been thinking about to try and get where I need to be ..........

Quick rundown on what I'm working with

3500lbs
BB on alcohol
1.80 glide
5600 spragless converter
4.56 rear gear
28" front tire
31" rear bias tire
double adjustable shock F&R
5" front end travel
150lbs removable ballast

Have to leave at 2000 rpm to go deep, leaving at 3000 shallow staged produces .080 ish lights

Truck works awesome and has yet to do anything stupid, I'm assuming it will hook with whatever I throw at it.

Here's what I'm thinking .......

#1 26" front tires, no brainer and has to help. How much ??
#2 5.13 rear gears over the 4.56's. Starting line ration has to help reaction time right ?? Question is how much ??
#3 1.98 low gear trans. Same theory as rear gears ?? Worth the effort ??
#4 Limit the front travel. Might effect the way it leaves though ??
#5 Tighten front shocks ?? Again, might effect leave.


Realistically I need .065 / .075 of vehicle reaction time to successfully shallow stage this thing, doable with I'm thinking ??? Ideas ??

All opinions and previous results welcome

I would go with the small tires first. Suspension would be last resort IMO. Like you said it will affect how the chassis works. I have a set of 5.43 gears for sale right now for a Ford 9" with small pinion.

Radials on the rear may help if your crushing the sidewalls now.

Bob, Both of the above suggestions should help.
Here is one that will absolutely help you, try to shed some weight from the truck. How well do your brakes hold, and (not sure how to word this), how loose does the converter act at stage? What I am getting at, is raising launch RPM. When I was struggling with the same issue on a heavy footbrake car, my "5500 RPM" converter would want to push the car badly above 3,000 RPM. (Converter truly did stall at 53-5400 on trans brake, but just felt tight on footbrake). Replaced every component in brake system except the pedal, helped some, but it would then slide the locked front tires through the beams around 3200 RPM. Finally bought a good adjustable proportioning valve to add more bias to rear brakes, that helped more than I thought it would. Threw more gear at it, helped a tiny bit, mostly helped the 60' more than the R/T, but had me twisting higher revs at the 1/4 mile stripe than I was comfortable with. Was fine for 1/8th.

Thanks for the replies !!

5.43's are a bit too much

Radials might kill two birds with one stone. A shorter tire to give it a bit more starting line ratio and no sidewall deflection should definitely help R/T I would think, never really thought of that We run a 11.5W tire on the truck that's actually 31" tall and 13.2" wide. A 29.5x10.5 radial would be alot shorter.

Trucks just a fat kid Jim, we added weight to get it to scale good and it works so well I'd hate to touch it lol. Got a 20 gallon cell and two 45lb 16 volt batteries plus 150 lbs of removable ballast, so I could easily shed 200+lbs but that weights right over the azz where I probably need it.

Trucks got good 4 wheel disc so I'm pretty confident we can footbrake to at least 3500 with little effort.

I was kinda hoping gearing would take a big chunk.

It's almost free to tie the front down and try that.

Front end travel has a lot of affect on RT in some vehicles....A lot in an old F-Body Camaro...

At some point limiting front end travel will cause you to spin.....

Raise the front end and put smaller tires on it....

Buy an ATI Treemaster sprag converter and you can stage at a much higher rpm without pushing thru...

I mean you just got it running right? Test test test...

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It's almost free to tie the front down and try that.

Gonna try that for the weekend I can take 2" out easily, see if that does anything.

quote:

Raise the front end and put smaller tires on it....

Smaller tires on order but I like the ride height lol

quote:

I mean you just got it running right? Test test test...

Got over 60 runs already Time for changes .........

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Originally posted by HS professor:
Trucks got good 4 wheel disc so I'm pretty confident we can footbrake to at least 3500 with little effort.

I would try this also.

From the 1/4 mph you listed and maximum hp being at 6700 rpm on the chassis dyno I think this.

You presently probably cross the 1/4 finish line close to or over 6700 rpm.

If it were me, I’d use a 1.98 trans gear and 25” front tires. Won’t change your present finish line rpm, mph or et. But will improve your rt. This would be close to the same SLR of a 1.80/ 5.13 .

Prior to purchasing any front tire it might be wise to find someone with the desired size / brand and measure actual rimmed height. I went from a Moroso 25” tire that measured 25.2” rimed to a 25” Hoosier that was only 24.3” rimmed. The new 25” GY I just put on measure 25”. I measured these on anothers car prior to purchasing.

Can you shed any weight on the front only?

Maybe try stainless-braided brake lines; on my truck it seems that the brake calipers release a tiny bit faster, as they lines don't need to 'shrink' back as much.

Smaller front tires I think would only reduce your reaction time 'on paper'.