FastBoys Leaf setup( Info )
FASTBOYS leaf tech(get it here)
Let's try this one more time
I am not too good at this typing and spelling thing, but I think you can get what you need to know about this setup
from this thread
I will start with a good base setup for what we will call the Fast Boys leaf setup.
Forget everything you ever knew about leaf springs (also most of what you do on bar cars is backwards from the way this deal works)When a bar car gets up on the bars the l/r tire walks forward, making the car loose. With this setup when the car hikes up on the l/r and the pinion rotates up the l/r tire goes back (making the car tighter).
Let's start with taking a standard stacked leaf car and making it into a fast boy's rear.
There are two ways to do this, the first is the easiest and would be a good way to start (easier to drive until you get
the feel for how tight it will be to drive).Leave the r/r leaf the way it comes(can use a 150 or 175 Ibs stacked leaf), instead of clamping it to the rear-end with u bolts you need to float the r/r spring mount on a bird cage. Leave the r/r shackels alone .Make sure you mount the r/r shock off of the rear end tube (instead of the lower spring plate) or it will wheel hoop.
Rebuilding the L/R leaf
Next you need to redo the l/r leaf spring and mounts on that side. This is the same for both the mono and stacked
setup, and the 2 stacked leafs setup we are talking about now.
1 have mostly used afco leafs in the past but I do like the new landrums that I have been working with now. I take
an afco 31 and rebuild it to make it hook on slick tracks. Take and cut the bands off and move the 2nd leaf down
(the one next to the main ) and redrill the center hole 3"s back ( moving the front of it forward). Now take the 3rd
leaf and turn it around 180 (front to back) and use the same hole. Now take the 4th small leaf and throw it away.
While you have it apart you will see that the main leaf doesn't have enough arche in it. I like to rearch it so that
when it is standing on the floor with the eyes down it is about 7 or 8"s tall at the center pin. Only put the arch in the
front of the spring (from the eye forward).also I like to add some arch from the pin forward in the other 2 leafs also.
When you bolt it back together only band the front of the spring (not the back).
What this has done is made the front of the spring stronger to deal with the increased load that this setup has on it, but the spring rate is now softer (letting it flatten out at ride height) and the extra arch will still want to come back into it when the l/r is hiked up (keeping the l/r tire on the ground and digging).It is important that you DON'T try to run the standard alum lowering block and u bolts on this deal (they will break). I run a 2" block on the r/r and a steel hand made bracket on the l/r that would be like running a 3" block. If you buy the parts from R C for this it is important that you weld the l/r bracket all the way around the rear end (the l/r is the only thing doing the lifting and it will try to tear everything over there off).
Now for the l/r shackle. This is where you will tune for heavy or dry tracks. You need to be able to put the top mount forward so that when at ride height the shackle has about 40 degrees of angle in it .I put my mounts on top of the frame rail and run a long 11" set of shackles. If you hook a tape in the 5/8 ths hole that the front spring eye goes in and measure back to the top of the rear frame rail make a mark at 51 "s and 53.5"s this is where the top shackle bushings need to weld on. Run the front hole for dry tracks and the back hole for heavy tracks when you want to take the wheelie out.
As for shocks on this deal, softer is better. I run 93 on r/r 94 on l/r and a pair of 74 s on the front. You don't run any 90/10 wrap-up shocks or any pull bars or 5th arms on here (been there tried that didn't work as good.) Make sure you mount the l/r shock so that it has about 6"s to come out and only 3 in when at ride height. Also keeping the back of the car lower is faster with this setup.
Mono - coil R/R setup
This is the full blown (Full Tilt) way to do this deal. It takes a bit to get used to driving ,and is not for everyone The
car will be tight when you pick the gas back up, and also have more side bite going in. You can drive the car way
into the turn and when the tail comes out and most cars would have to wait to get back on it till the tail is back
under you, instead you pick the gas up while the tail is out and it will bring the tail back under you. This is because
of two things, first the l/r spring is the only thing that is putting load in the rear end when you pick up the gas, so it
gains a bunch of l/r bite when you are on the gas (probably gains around 200 to 300 Ibs or so) but when your off
the gas and on the brakes going in it gains r/r giving you more side bite.
The other thing that this does is the roll steer. Bar cars move the r/r back and the L/R forward when they get on the
gas. This makes the car loose and so they have to run more wedge to keep the car straight coming off the turn,
that makes the car loose going in and loose through the center.
With this set-up when you're on the gas the L/R tire goes back in the wheel well and tightens up the car. The mono
on the r/r is all that is pushing the car forward on that side and is floated so the wrap-up is out of the picture. This
makes the mono s up some and moves the r/r tire forward in the wheel well. This roll steer along with the way the
r/r coil is mounted makes the car tight when you're on the gas and tight when you're on the brakes.
Here's how to do the r/r.
Put a mono on the r/r (I use the main leaf out of an old stacked leaf).You have to float it on a bird cage just like our
2 stacked deal was. Here is where you have to get this correct at. Mounting the coil on the r/r.You have to mount it
on the back side of the rear end tube and to the tube itself (not the bird cage or the lower plate).try to get it about
7"s from the center line of the axle (much like a coil over mount on a l/m clamp bracket would look).Try to get the
top of the coil in about 15 degrees and also back 15 degrees.
I run a 125 coil spring over there, but most guys like to start with around 150 .Mount the shock off the front of the
tube and go in and forward on the top mounts.
R C race cars sells all of these mounts if you can't build them.
Here are some basic numbers for my type leaf car. Each car is a bit different, but try to keep the rear and left side
percentages close to these.
I scale my car without driver (always have) keep all lead to the left and to the rear. Try to get left side at or above
54, and rear at or around 60 at the end of the feature, I run a long wheelbase car so adding my lead to the very
back of the car doesn't make the car swing the tail like it will on a short wheelbase car,
I can get these numbers with the car weighing about 2300 after the race. On the 2 stacked leaf setup start with
around 50 to 75 Ibs heavier on the R/R tire than the l/r tire .On the r/r mono and coil deal you need to start with 100
to 150 r/r heavy. This will make your r/f tire weigh around 300 Ibs but don't get to nervous.
As far as stagger you can't get too much. I try to run 3.5 to 4"s all the
time (this will tell how good you were at copying this deal if you can't run that stager you probably didn't get it
correct). Run big tires on both fronts if your looking for more forward bite ,and small tires on both fronts if you need
the car to turn in better on fast tracks.
I like to run all 3" offset wheels ,l do mess with that a bit, but it is backwards on this setup than any other car you
have ran, and everyone that tries to help you with tightening up your car with wheel offsets will be telling you
Here's how it works on this deal. To make the car tighter on a dry slick track, move the l/r tire UNDER the car
more, If you want to make the car looser ,and easier to drive on a tacky heavy track move the wheel out on the l/r
and under the car more on the r/r, ,l know that sounds backwards but that's how it works on this setup ,and is
where most racers screw this deal up.
That is a good start and I will post a link to the pics again and go into the mono and coil r/r deal next, just give me some time.
P.S, to 4M please let us know when your going to dump this thread so we can copy it next time please, There were a lot of racers using it to work with this setup and you made my phone keep ringing from deleting it. I am not, nor have I made ANY money from posting on here (Just trying to help out the low budget racers.
Scott (Scooter) May
could you email contact info for the people who built the chassie in photobucket album? thanks chumba Sorry forgot to give email adress [email protected]
Last edited by CHUMBA; 11-29-2010 at 06:12 PM.
Robert Crump at RC Racecars and Parts in Peoria IL. Robert he can be reached at 309-453-8086
The first car was mine, it wasnt an RC it was a hassy, real pretty, but couldnt take a hit for nothin, I have a 10 night old ellis thats nicer than that for sale.
Back to top ,so some guys can find it.
any one doing this on a camaro/street stock??
Come on Dave, they dig harder than that!!lol
Last edited by TALON75; 05-16-2013 at 06:04 AM.
That was after I toned it down; not seeing the competition out the left front took the fun out. I'll post one that you can see the header, if I can dig it out.
Ya, I know Dave, that was one of our earlier pics too! It worked a lot better when toned down!lol
How can you get 3 to 4" of stagger if the rules say G-60 Hooiser tire only ??????
Does anyone know where you can buy a pre-fabricated mount for the slider on the passenger side. I am correct and the Coils spring on the passenger side is actual a pull bar and not a weight jack. One more thing, any suggestions if you cant run a birdcage?
Has anyone ever tried this setup with out the bird cage on the rr and with the coilover slider in the front of the rearend clamped to the axle tube? Seems it would help tame it down a little with the axle twist loading the coil spring insted of unloading it when you on the throttle........any thoughts on this will be appreciated.
Hi, trying to get some info on the fast boys base setup as I am new to this setup.
What front springs are best for the base setup & do you run the front springs with the heavier spring in the LF or RF?
Do you run the wheelbase straight up or do you run the RS longer do to the LR walking rearward under acceleration?
What is the best mounting point for the leafs on the rearend? Do they work best mounted closer to the hubs or does it matter?
Does it help to run the pivot bushings in the front leaf eye or is the rubber bushing better?
Any info would be greatly appreciated, Thx
right rear shock
The right rear shock boddems out when cornering hard , had mono with 150 coil , tryed a staked leaf , still hits bodden , has good bite but not lifting left front much , also the left rear long shakels are bending from side bite , alot of body roll , any ideas ???
what rate is your RR leaf pack? make sure your shock is mounted with enough travel .
HSM and Superstock , this setup works well without the birdcage on the RR stacked both sides and no coil over on RR .
Last edited by TALON75; 06-08-2011 at 12:00 AM.
The stack was a 150 , the mono was a 35 with 150 coil the shock travel is around 7 " the right front moves about 3 " Going to try to get more travel on shock but I don't think it should roll over this far . This is a 2600 lb big metric chassis Cobra mod .
I'd probably stiffen that RR up a bit, we ran a 200 stack and never had that problem . don't worry about liftin th LF, we found it handled better when that was minimal .
Last edited by TALON75; 06-13-2011 at 11:42 PM.
Can this leaf setup run with a top ump mod , or is it a certain setup for a certain class? The pics of the cars and springs look cool. I always liked the cars that are different.
We palyed with this type of setup with a new young inexperienced (age 15) driver when we started Mods. Was the first thing he raced in the class and in the Tack it was bad fast and real good on a rough track. It was not to the letter of the Fastboy but real close. If we had had some patience with it and not jumped to 4 bars I think it is capable. The second night in the car it led many laps until a bone head in a pushing 4-bar overdrove the corner and T-boned it. Still salvaged a 6th place finish full field. I think it is possible. I also think 3 link will still get it done also. They all will work when they are right .JMO
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