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View Full Version : What am I doing wrong with double swingarm?



Homey
05-24-2010, 09:32 PM
Older metric mod recently changed over from 2 link to short swing arm both side. 450# left rear spring 300# right. 200lb lr bite, biscuit pull bar and biscuit jbar. Jbar down on pinion up on frame 7" of rake. Upper links are 17" with the 14" lowers. Coilovers mounted on the swing arm. Car has absolutely no body roll. Forward bite decent as long as track is heavy. Slicks off out goes all side and forward bite. I can honestly say I am lost with what to throw at it next. Any help would be greatly appreciated.

Martin

loneranger22
05-24-2010, 09:46 PM
Change your springs to 350 LR, 225 RR. Set it with 300LR bite, (swing arm cars like lots of left bite). If track slicks off you can go to even more bite.
Set your front links about 10deg up toward front, rear links flat.

For shocks go to 4/4LF, 3/5RF, 6/2LR, 4/4RR
(all these are compression/rebound)

CC28
05-24-2010, 09:48 PM
Put a straight bar on there with a little angle when moist, flat when slick, and hold onto your hat. Your always gonna have to look for the moisture, but if you can get it at all you'll be rippin. With that rr spring you should be pulling a wheelie all the way around. What kind of pullbar? Front springs? Percentages? Motor? Track?

Homey
05-24-2010, 10:33 PM
Front springs 575RF 650LF. QuickCar biscuit pull bar with red biscuits. Bilsteins 3535LF 5030RF 5030LR 4010RR.
4/10th high banked redclay. 385CI.

55.4 leftside
54.5 Rear
52.1 Cross

Should the birdcages be straight-up?

CC28, short straight bar or long? Up on pinion or down?

CC28
05-24-2010, 11:53 PM
Short straight bar, second or third hole from bottom on pinion,more rear for sure, those shocks are questionable, Id get a set of rayburn konis and put em on. Red clay and swingarm you should be flying.

JustAddDirt
05-25-2010, 07:29 AM
Front springs 575RF 650LF. QuickCar biscuit pull bar with red biscuits. Bilsteins 3535LF 5030RF 5030LR 4010RR.
4/10th high banked redclay. 385CI.

55.4 leftside
54.5 Rear
52.1 Cross

Should the birdcages be straight-up?

CC28, short straight bar or long? Up on pinion or down?

Front springs are WAYYYYYYYY too soft. Do you have the NOVA a-frames on car or is it still Metric stuff?
If it is NOVA go with a 900RF and a 700LF. When I had a lightning swing arm car I won probably 50 or so races with it in 2 years. Didn't matter what track I on it was bad fast with the above springs on the front.
Also go to a straight Panhard bar. no more than 3 inches between heights on frame to rear end. Mount it on the top hole on rear end. Swing arms do not like alot of angle, it holds car off LR spring if there is alot of angle in panhard bar.

Also need more rear %.
Also if you did not know, Bilsteins number their shocks backwards of anyone else, so your 50/30 LR is killing you it needs to be a 30/50, and the RR a 40/40

Put pullbar as far left in the car as possible. 220-240 LR bite.

What is the motion ratio of the lower swing arms? Total length, and the distance from the back heim to the spring mounting point. Short front arms useually mean you need a stronger spring, so I think you are close there.

Homey
05-25-2010, 11:29 AM
JAD,

Still on the metric front lowers. What spring rates would you recommend at all four corners?

Martin

CC28
05-25-2010, 11:44 AM
Yikes, you didnt say that. Only reason your not bottoming out the right front real bad is becuase its getting no bite due to the rear percentage. Put the heaviest ones you have on hand in and see how it feels. 800 to 1000 right front on metric lowers, probably 1000 since when you do get it figured out on a big track your gonna be flyin.

JustAddDirt
05-25-2010, 03:52 PM
Yikes, you didnt say that. Only reason your not bottoming out the right front real bad is becuase its getting no bite due to the rear percentage. Put the heaviest ones you have on hand in and see how it feels. 800 to 1000 right front on metric lowers, probably 1000 since when you do get it figured out on a big track your gonna be flyin.

Agree 100% with CC28.
800-1000 is pretty close if still using the metric stuff.
once u get it going it will b fast.

DGI
05-26-2010, 03:40 PM
JAD

Do you think the swing arm stuff will still compete with the four bars? Wondering mainly about slick conditions.

racin6mod
05-26-2010, 10:53 PM
YES the swingarm is a far better design you can put a ton of drive in that a 4 bar design can't get.

JustAddDirt
05-27-2010, 08:55 AM
JAD

Do you think the swing arm stuff will still compete with the four bars? Wondering mainly about slick conditions.

I believe the swing arm car that I had, had more forward traction than any 4 link car I have had since. The ONLY problem with the swing arm is getting the car to turn. I had tons of traction, and tons of sidebite, but it was hard to rotate the car throught the center. But my car was a 112" wheelbase. If I had that same car on a 108" I think it would be a very very good car. The gentleman that has my old swingarm car now, loves it, and it is on the same setup that I had on it.

Triple Nicklll
06-04-2010, 12:52 PM
We have one of the new Rayburn swing arm modifieds, base setup is

Springs, LF 750 RF 800, LR 325 RR 500, we run Koni Shocks set on Firm, bud bar on the right side of the chassis mounted to the left axle tube, with and Rayburn pullbar and 5th arm. 2" offsets all the way around, we've always been on a four bar car, it's the first time I had ever driven one, alot different on entry and through the middle, but the car is FAST! The thing with these cars, drive it in a little harder and get the car rotated in the middle before you pick up the throttle. Oh Yea....59% rear, 55% cross, 53% left....goodluck....these cars will go

Windy
07-05-2010, 04:52 AM
03 grt was metric clip with 800 lf 1000 rf 425 lr 375 to 400 rr,long pullbar with a 1000 to 1600 from jet racing for tacky to med traction tracks and 900 to 1200 spring in the slicker track conditions..left rear birdcage clamped to housing with no rear bar..straight bar down on pinoin up about 5 or so in the tacky or decent traction and up 1 or 2 holes and down on the frame with very little rake ,maybe 3 or so inches in the slick..30 or 40 lbs of lr to 30 lbs of right rear 56 left side and 54 to 54.5 rear most of the time..this car eat 4 bar cars every where we ran..left rer clamped freed up entry and we adjusted the pullbar on the rear end from right in tacky towards left when it was slick ..the car was always fast..hope this helps..windy..
Front springs 575RF 650LF. QuickCar biscuit pull bar with red biscuits. Bilsteins 3535LF 5030RF 5030LR 4010RR.
4/10th high banked redclay. 385CI.

55.4 leftside
54.5 Rear
52.1 Cross

Should the birdcages be straight-up?

CC28, short straight bar or long? Up on pinion or down?

tumbleweed
07-06-2010, 09:06 AM
Have always been intrigued with the swingarm, but, don't know anything about how the brackets are positioned on frame. I assume it will work on an overrail frame.?. Does anybody have some really good pictures or a web site I can go to? Tried to google, but, didn't find anything very good. If you have pictures, please PM them to me? Thanks

21racing
07-07-2010, 12:30 PM
I have a 99 lightning and having the same problem decent when tacky and very bad when slick springs lf 900 rf 1100 lr 300 rr 325
150 pounds of lr
56.6 rear percent
53.2 cross
does any body have any suggestions

JustAddDirt
07-07-2010, 01:40 PM
you have PM
I have a 99 lightning and having the same problem decent when tacky and very bad when slick springs lf 900 rf 1100 lr 300 rr 325
150 pounds of lr
56.6 rear percent
53.2 cross
does any body have any suggestions

tumbleweed
07-08-2010, 08:30 AM
OK, let me go in a different approach, since I didn't get any pictures or any input. I don't think we have any swingarms running locally. What is the difference between a swingarm and a fourbar? I run a leaf mod and not getting anywhere with it; was thinking about changing rear suspension during off-season. Thanks again.

mod6f
07-08-2010, 08:59 AM
Swingarms need a ton more bite than anything else. Go to the Rayburn site and look at the tech section for some base lines. I run the Rayburn with 400 accross the back and 300lb lr bite. Warrior has some info in their tech and they use softer rears but still list 300lb of bite.

Tumbleweed:
Swingarms are a little more stable and forgiving, especially in the rough. They have have a ton of bite and less rear steer than the 4 bar cars as well. Go to the Rayburn site and look at the pics and you will see the difference of the swing arm and 4 bar rear.

tumbleweed
07-08-2010, 02:44 PM
Thanks, Mod6f. That is what I liked about what I have been reading about swingarms. The 4-bars do not suit my driving style with the erratic reactions they seem to have when coming off the bars real quick, like when a car spins in front of them. I like being in more control than they appear to be in a "panic" situation. May try to convert my car over to swingarm.

Homey
07-08-2010, 03:24 PM
Switched front to LF850 RF950
LR 425 RR 325

Pull bar all the way left, up on chassis. 12degrees angle
Straight bar down on frame and bottom hole on pinion.
220 pounds of bite

Like driving a different car. Very good forward bite and decent side.

57 rear
54 left
54 cross

chasefrehley
07-09-2010, 08:26 AM
I have been reading this thread because it always helps to get other peoples ideas.. I have a Jet viper (on a metric clip) with the long swing arms and short rear bars. Running the Sweet biscuit pull bar, straight bar from rr axle to lr frame. 900rf 800lf, 325lr, 300rr. 51% left, 57% rear, 48% cross, and 100 lbs lr.. I tried more left rear and the car was way to loooooooose could not touch the gas... most left rear in car was 200,

n2speed
07-14-2010, 09:35 AM
Let me tell you the trueth about running a double swing arm car,you can run a 175 RR and 225 on the LR. I ran this set up on the USMTS TOUR back in 2003. Top ten in the national points until the end of summer and started going thru a divorce...Had to stop racing on the tour....HERE WE GO!!!! All you have to do is run the left rear spring infront and shock behind,next you will put the shock on the swingarm for the RR and the spring behind..The car will scale out so easy you wouldnt believe it! I wanted to keep running it,but was talked into going 4 link 4link...Now I love the 4 link but still believe my swingarm car was easier to drive..

n2speed
07-14-2010, 09:48 AM
here is how the set-up went for us..We scale our cars with the driver in the car...


left side-52.8-53.1
rear %- 56-58
cross % - 48.4-48.7 for a tacky track
front wheel weights have a 120-127lb split(left front weighing more)
Im sure you might not believe me but I only run 45lbs left rear with me in the car. Finished 7 in the Topless 100 and started 23 with this set up,if you have any questions im sure that I could help with this topic!!! See thats why people went away from swingarm cars because no-one knew how to run the lighter springs behind,we found this thru many trials and errors but it will work...