4 link setup ?

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demented · #1 Post by **demented** » Sun Apr 15, 2007 1:19 pm

I have a question that may not be the easiest to answer because of my form of racing. Even though it is drag racing, its in the Mud.(Yes, mud drags).Well even though it's not on pavement, it's still fun as hell.Well anyways, I'm new to this forum but have been following it for a while at it seems to be very informative. My question is this, My car, set up with a four link rear and single adjustable coilovers has a problem with, (and some may get a kick out of this because we are talking MUD) spining the tires for the first 25-30ft then planting them so hard that it picks the frontend. If I didn't have a wheelie bar, it would come straight up

(done this before). How can I get the car to hook better at launch and settle down better

. Car is very consistant and goes straight as an arrow. By the way 2700lbs. '23 altered-tube frame with 632 BBC one stage 350 hp fogger,with enderle injection on alcohol. TH400 trans no brake-5800 stall. Running 2.500-2.700 in 200 ft. yes in mud. These cars act just like an asphalt car because of the tires( they plant hard, Trust me).I want to try to get the car to go forward not upward. Any info would be helpful and thanks in advance.

mmsports33 · #2 Post by **mmsports33** » Sun Apr 15, 2007 2:53 pm

Maybe I can help some with this........I've got a little drag experience and tons of dirt track experience......but really without seeing it or some more info I'm just gonna throw a few ideas at ya......I would say it hooks so suddenly so far out because the spining slows enough that it finnaly hooks a little and you get your weight transfer and away it goes.........so I think if you can fix the launch it would take care of the other. Just a few suggestions..........have you scaled the car? The front to rear percentages could be off......if I had to take a guess.... depending on your wheel base I think you would need about 52% rear on a four bar car........air pressure......have you played around with it any?.......the front mounts for the top bars.....are they set too low?.......and are the lowers pretty much level?........pinion angle?.......I would want about 4-7 degrees depending on the rest of the set up.......maybe you need a trans brake to help shock the tires....have you tried one before?...........this is just some of my ideas on the chassis end of it..........I mean you could play with different cams & converters or different launch techniques......maybe some of these drag guy's can chyme in on some of that..............

mytmouz · #3 Post by **mytmouz** » Sun Apr 15, 2007 3:44 pm

We had a similar prob with our mud truck a few years back. Adding adjustable shocks (coilovers) in the rear and playing with the settings finally cured it.

demented · #4 Post by **demented** » Sun Apr 15, 2007 3:47 pm

I have played around with numerous things. Tire pressures, bar locations,spring pressures,etc.... Currently, my bars are set up with the lower bar level and the upper bar located to give 69 % rise on a 137" wheelbase car. Center of gravity ends up at the converter @ cam height (28" from the ground on this particular setup).My instant center is located behind my center of gravity.Pinion angle is 3 degrees up.I am not an expert on suspensions by any means but I have been around the block. I think I'm real close as far as my setup is concerned but just don't have the fine tuning skills.As far as tranny brake would shocking the tires make that much of a difference in a loose traction situation?

sunsation540 · #5 Post by **sunsation540** » Sun Apr 15, 2007 11:31 pm

it spins the tires so hard that it hooks 30 ft out add 100 lbs to the nose and gear it up 4.10 to 4.30 i have no idea what gear you are using think of this as a high hp stick drag car the higher the gear like 3.73s the more tire speed .. even with steeper gears it will recover from the inital spin quicker. control tire speed. talk to the truck pullers!i think a trany break would make it worse the paddle tires will only get so much bite any way.

demented · #6 Post by **demented** » Mon Apr 16, 2007 10:25 am

The gears I have are 4.88 in a dana 60 with 44 inch tires. I only use 1st and second gear on my th 400 tranny because track length is only 200 ft. Does pinion angle make a big difference?

mmsports33 · #7 Post by **mmsports33** » Mon Apr 16, 2007 3:21 pm

Man.......it sounds like you have a pretty firm grasp of the 4 link set up........I agree that shocks that offer a lot of adjustments can be very helpful.....but at the same time guy's have been getting 4 bar cars down the track for a lot of years without them......I don't know......as far as pinion angle...I think that on a 4 bar car it can hurt more than help....you know? I mean if it's not right it will hurt you more than playing with different angles will help....if that makes sense........

stroker1 · #8 Post by **stroker1** » Mon Apr 16, 2007 4:25 pm

Have you tried limiting the front end travel? The front end upward momentum can be toned down with limiters to the A-arms. You can use metal straps or threaded rods.

Stroker1

demented · #9 Post by **demented** » Sat Apr 21, 2007 6:49 am

[quote="mmsports33I don't know......as far as pinion angle...I think that on a 4 bar car it can hurt more than help....you know? I mean if it's not right it will hurt you more than playing with different angles will help....if that makes sense........[/quote]

I haven't really focused on pinion angle because of some misinformation about the concept. It was told to me that pinion angle does nothing as far as suspension reaction is concerned, it was more a reliability factor on the driveline and to equalize ujoint angles so they don't vibrate. But I have also heard that it can hurt traction but I'm not sure how. Can someone help?Can changing pinion angle help the way a tire plants the ground.

#10 Post by **John_Heard** » Sat Apr 21, 2007 7:09 am

I'm in the pinion angle by itself doesn't affect bite camp, it's only an issue about getting the driveline at the most efficient angle under power. I'm going to keep on believing that till someone proves different to me haha.

On your mud buggy, I'd like to see some real good slow motion video. I think that would help a lot to try and understand what the car is doing.

mmsports33 · #11 Post by **mmsports33** » Sat Apr 21, 2007 8:24 am

Oh....I'm with you guy's as far as pinion angle all by itself not being much of a factor.....BUT like I said......if it's REALLY off it can prohibit the rear suspension from working correctly and freely to do it's job. This is usually more pronounced in leaf spring cars because the pinion angle can change so dramatically. I've seen instances where it was way off and the binding would hinder the suspension in it's travel......like I said......it can hurt more than help......I still think if he can fix the problem at the launch the other will take car of it's self or be fixed with minor tuning........I think if you add front percentage it will just spin worse

demented · #12 Post by **demented** » Sat Apr 21, 2007 8:41 am

Beyond wrote:I'm in the pinion angle by itself doesn't affect bite camp, it's only an issue about getting the driveline at the most efficient angle under power. I'm going to keep on believing that till someone proves different to me haha.
.

I agree with you on this point. I think the concept of pinion angle has been mislead by the many and misunderstood. As far as the video I have quite a bit of video of the car at launches some not as good as others. What should I be looking for? I have looked at the reaction of the chassis numerous times and it seems like my rear end doesn't squat much(maybe an inch or two). I don't know how to but video for you to see. but here are some stills that are from the same run at a race in bloomsburg,PA.
http://www.photoreflect.com/pr3/OrderPa ... 6&po=66&c=
http://www.photoreflect.com/pr3/OrderPa ... 5&po=65&c=
http://www.photoreflect.com/pr3/OrderPa ... 4&po=64&c=
http://www.photoreflect.com/pr3/OrderPa ... 3&po=63&c=
http://www.photoreflect.com/pr3/OrderPa ... 2&po=62&c=
These don't really show much as far as the way the chassis reacts at launch but it does show some pretty good grip of the tires about 20ft out as the side wall flex shows and youcan see the front end just barely on the ground. It's pretty neat to see a car do this in the mud.Let me know what you think.

demented · #13 Post by **demented** » Sat Apr 12, 2008 8:48 am

Sorry about re-hashing an old post but I thought you guys could give me a little more insight about my setup. Just to fill you guys in on what I have done up to date; I have changed the I/c location so that I have 152% anti squat with the I/C 15.4" of the ground and 49" forward of the rear axle. The shock setting is light on the rebound and compression(single adjustment)

After taking the car out for the first time last weekend, I was pleasantly pleased with the results that I had and the way the car hooked and ran down the track. One concern I had was at launch the car had some rear suspension separation(about 2").I believe that this helped my launch as it did drive the rear into the ground. The car went straight with very little steering effort, which I was also pleased with. The front end rose on launch and settled down quickly.

Should I be concerned with the rear separation and If I should be can I adjust it with the shocks? I feel that my adjustments are going in the right direction but I am still lacking some more traction. The adjustments I did was in an effort to put more power to the ground and to keep the front end down, which I think I have done fine with so far. Any suggestions?

Longo · #14 Post by **Longo** » Mon Apr 14, 2008 9:06 pm

I would try to shorten your ic more. This will give you more traction at the hit for a shorter time!

rustbucket · #15 Post by **rustbucket** » Mon Apr 14, 2008 9:51 pm

i cant offer any technical help, but i sure would like to see that beast with a set of slicks at the drag strip.lol

4 link setup ?

4 link setup ?

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