Visit The Dirt Forum for More Information

Author Topic:   Radius Bar Angles
vintage39c
Dirt Full Roller

Total posts: 27
posted October 27, 2005 07:36 PM  
While an East Coast Mod and a Sprint use basically the same rear suspension I've noticed that the East Coast cars use a **** load more angle on the radius bars. I was just looking for a little input as to why. Any insight would be greatly appreciated.

cozmo
Dirt Forum Racer

Total posts: 99
posted October 28, 2005 06:14 AM  

Sprints use a closed drive shaft tube that acts as there torque arm were an east mod uses a torque arm on a slider below and behind the trany. Sprints use live axles so the bird cages are not clamped so the front radius rods are at the top of the bird cage and the torsion arms are mounted to the bottom of the cage like a z-link. The mods in the past had the same set up; but the current stock set(ie. teo, bicknell) up is with a closed axle with the bird cage clamped and the radius rods are mounted to the bottom of the bc and the torsion arms ride on rollers under the axle on the bird cage. The higher angle gives the car more forward bite as the rear drives under the bars.

coz

vintage39c
Dirt Full Roller

Total posts: 27
posted October 28, 2005 06:10 PM  

 
Ok, now I need some suggestions. I'm running unclamped birdcages, torsion bar mounts on the bottom and radius bars on the top with an Afco torque link on top of the rear. What kind of radius bar angles would you do. Car is home built vintage Modified that has been fast and won it's share of Features. Have always thought car hasn't had enough forward bite, and competition is biting on my heels. Time to pick up the pace, you all know what I'm saying. Any intelligent input is welcomed.

cozmo
Dirt Forum Racer

Total posts: 99
posted October 29, 2005 06:05 AM  
what radius rod and torsion arm angles are you running now

what length radius rods and torsion arms

what is your pinion angle

is your torque link spring, biscuit or solid

coz

rocket36
Dirt Freak

Total posts: 209
posted October 30, 2005 12:51 AM  
a winged sprintcar will "tip" into the turn.
a modified will "roll-over" to the outside of the turn.
radius rod static angles will need to be different.

vintage39c
Dirt Full Roller

Total posts: 27
posted October 30, 2005 07:03 PM  
Car is set up like sprinter with a 2" split, rt rr arm is 14" and lt rr is 16". Radius rods are 30 3/4" from heim center to center. Lt rr arm has been run flat to around 3 degrees, rt rr arm is 1.5" higher. Don't know what the degree is we just block it and raise the right side. I'm going to guess that the rr radius bars are run from flat to 3 degrees and the left and 5 to 8 degrees on the right. Torque link is an asphalt single spring unit, have run it from 10 to 20 degrees with a 1200 lbs spring and a 600 lbs spring. I use a 90/10 with it mounted at 5 degrees. pinion angle is 5 degrees. When I designed this chassis the only thing I could compare it to was a non-wing sprint, but have learned with the changes I've made they are completely different beasts. It's also not like a DIRT mod but somewhere in between, that's why I'm looking for some input from you guys. Oh, and to put the photo into prospective the car only has a 99" wheelbase. Also to complicate things I run in 5 different states and very seldom run the same track twice in a 12 to 20 race schedule.Once again any intelligent input is welcomed. I'm not looking for gnats a$$ stuff just ball park theory stuff.

dbradley
Dirt Freak

Total posts: 251
posted October 30, 2005 08:52 PM  
Vintage,
I took a bunch of picture as we were building our Bicknellup last winter...PM me with your e-mail if you want so see the close ups of the rear..
Darin

cozmo
Dirt Forum Racer

Total posts: 99
posted October 31, 2005 08:49 AM  
what is the weight of the car

what shock valving are you running front and rear

how much rear offset are you running

coz

vintage39c
Dirt Full Roller

Total posts: 27
posted October 31, 2005 04:08 PM  
Car weighs 2230 lbs. Rear % is run from 53% to 56%. Left is run 50/50 to 52%. Cross anywhere from 48% to 55%. I run the Carrera gas charged chrome shocks. I run several combinations. Sometimes 75's lft & rt, 75 lft & 72/6 rt, 72/6 lft and rt. On rear 95's lft & rt, 96/5 lft & 95 rt, 94's lft and rt. the rear is centered. You have to understand we run in 5 different states from 1/6 mile to banked 1/2 miles and have to run several combinations. The surface can be from heavy black clay to packed sand.

cozmo
Dirt Forum Racer

Total posts: 99
posted November 03, 2005 06:01 AM  
vintage i'm still chewing on it

you could try some ez-ups on the front to get more weight to transfer to the rear.

i would start out with the same compression you have been running and work with lower rebound.ie 75/2

you can also try a tiedown on the rr that has helped us on dry slick lets the car roll over and holds it there longer for more side bite.

how much lr bite do you run?

coz

dbradley
Dirt Freak

Total posts: 251
posted November 03, 2005 06:33 AM  

coz
The tie down/easy up has really worked great for us as well.I would think it would only be more effective on the shorter dry slick....You have good luck with it as well on your big sweeping tracks as wee???

vintage39c
Dirt Full Roller

Total posts: 27
posted November 03, 2005 03:40 PM  
I am already running ez ups. Carrera numbers are backa$$wards. 72/6 would the same as everbody elses 76/2. Never thought about the tie down on the rr for side bite, interesting, I'll have to give it a shot when I run into a slick track in 2006. I ran from 80 - 160 for left rr bite this year. While I appreciate the input and hope there's more to come, I would like to know what kind of bar angles DIRT mods used when they were running a rear suspension set up like I previously posted.

cozmo
Dirt Forum Racer

Total posts: 99
posted November 04, 2005 05:20 AM  
your set up on a dirt mod is a little before I came to the northeast, but the drivers and teams I have talked to either do not remember(donít want to share) or never played a lot of attention. your set up from what I understand is used on the Australia dirt mods(which is vary similar to what you have) but supposedly there is a movement to be more like the northeast and started copping the Bicknellís.

One suggestion is to have your shocks dynoed. I have seen shocks from just about every company to be off from shock to shock. Also as they age they change most of the time they get stiffer in the valving. You find some neat stuff when you have a shock dyno to play with. Canít wait to see the new torsion bar dyno comes in.

For eastern states 200 we ended up with 220# lr bite (got to love bar jackers) at the end of the race. Normally we try to for 60# which is what we started with at the beginning of the weekend.

coz

Back to the Archives