I know the madman comes highly recommended. Having said that I have one here and it's SHORT. In fact 7" shorter than the Wolfe Arm.

I'm swapping to a TH350 and need to buy a crossmember and can't decide whether to go with the BMR w/torque arm mount and the longer stock style arm or go with the shorter madman arm, or something in between. The BMR crossmember has has adjustment holes for instant center change. The stock adjustable would be about half the cost of the madman.

Setup will be 3000lb raceweight, 427 L92, 550+ rwhp.

It seems people have issues with being on the bumper with the Madman and other short designs. If I can hook to the tune of mid 1.2 or low 1.3 60's with a longer arm that would be my choice.

What are you thoughts, go LONG or go SHORT?

 

I like my short arm.. BMR xtreme duty.

 

Stick with the madman arm. If the suspension is set up correctly, it wont go on the bumper.

 

I put my car on the bumper with a long arm. I've always liked the longer arms because common sence tells me that the longer arm would have more leaverge. Of course i could be totally wrong.

 

Gimp98TNT,

On a stock suspension F-Body there is more to consider than simply the length of the torque arm. What we're essentially talking about is "Instant Center" (AKA "IC"). The IC is the imaginary point at which your car will begin to rotate upwards. The IC is found by drawing imaginary lines along your Torque Arm and Lower Control Arms. The spot at which these two imaginary lines intersect is your "IC" point. It's generally described in distance from the center of your third member forward to the imaginary "IC" spot, and also distance above the ground.

Generally speaking, the farther forward (Meaning 60" from the rear-end instead of 55" from the rear-end) your instant center is, the softer your car is going to "hit the tires". Also, the closer your intersection point is to the ground, the softer your car is going to "hit the tires".

Using a torque-arm is much like using a ladder-bar. In a ladder-bar rear-suspension, the "IC" quite literally is where the front of the ladder-bar is mounted to the chassis. So in theory, a shorter torque arm will provide more leverage for planting the rear tires. It would be possible for a shorter torque arm to cause a softer "hit". You would have to install the arm so that when the car is sitting on the ground at ride height it is angled up, as to move the "IC" farther forward.

"IC" is just one piece of the giant puzzle that is lining out a chassis to be effecient. The best bet is to find somebody who has worked with Torque-Arm style suspensions and have them set it up for you. It will take a lot of the guess work out of it and will make your life a lot easier.

 

Good read Ben, thanks.

 

Dont these two statements contradict? If you move the arm to the higher hole on the mount (like in a madman or wolfe style torque arm) the intersection point will be higher, making the initial hit harder, as you said in quote on top.

 

Moving the bar up in the mount also moves the IC point forward, softening the hit. It's best to just assume there are no absolutes. Take good measurements and do the math to get your interstect point. Over time you'll see a trend develop.

 

Either one is capable of getting the job done if setup correctly. I have a stock length TA on my car and it 60 foots in the high 1.2's on drag radials all day long. Ben R provided lots of good information in his post.

 

While talking about IC can you explain about the effect of relocated LCA's.

I thought that generally you wanted to move the IC farther forward to increase traction but you said moving it forward would soften the hit to the tires. So if I'm not mistaken moving the LCA to a lower hole on the axle will move the IC backwards. And will this make it hit the tires harder?

 

Going by what you are saying Ben if I am running my tq arm one hole from the top in my bmr crossmember for a th400 swap, I shoudl lower the arm in the mount to get the car to hit the tires harder then... I have relocation brackets on the car, and I have stock springs with the front lowered about an inch, and the rear spring rubbers removed to get the car to sit a little more level with the 28 inch radials.


Problem I am having, is that I can footbrake the car to a 1.46 to 1.50 60 foot, but if I try to leave on the transbrake it just fries the tires bad. The car seems to transfer weight, it just doesn't like leaving on the transbrake at all. I know that I can go faster if I can get it to leave off the brake I'm sure. Car weigh's 3465 with me in it and makes 470 rw thru a 5800 converter and th400

suspension setup is stock springs all around, qa1 R series front shocks, 12 way rears, wolfe drag bar no preload at all, front shocks at 2 (one being loosest) rears at 4/5 staggered right rear stiffer, goodyear 275/60/15 drag radial, bmr tq arm and relocation crossmember, relocation brackets one hole down from stock, pinion angle -2

 

You need to put your car on the round and take measurements of EVERYTHING before you start to make changes. You also need to keep records of the changes you make and the way they affect the car at the track. I'll try to draw up something ghetto in paint and post it in a minute.

 

If you move the TA up in the mount you're generally going to cause the car to hit the tires harder, not softer.

 

God I'm terrible at drawing in paint.

If you put the LCA Relocation brackets on your car you're lowering the rear mount for the LCA, which is going to move the IC back, causing the car to hit the tires harder.

 

First, get rid of the QA1's. They're just terrible for drag racing. Get a Strange or Koni or AFCO shock. The valving is much more drag race oriented and will actually respond to any changes you decide to make.

You also need to play around with tire pressure a bit with the radials.

 

Thanks you have answered a few questions. Now I will have to make some changes, while at the track, to see what I can get this car to do. I think I should have been able to pull a faster 60' on the 200 shot then a 1.483. But that still felt good. To me I have a hard time telling how much the tires are spinning but with 28x10.50 slicks It should pull a better 60'.

 

As much as I'd like to go out and buy afco's. it's just not in the budget at this point, and I've seen guys go into the 8's with them, so it makes it a little harder to just point the finger at the shocks.

I think it's something with the geometry that still isn't right. I do want to play with the tire pressure soem, I started with low pressure and that didn't work, went up to 18 and immediately the tires started to hook a TON better. Next time I go Im gonna put them at 19 the first run and try stiffening tboth rear shocks a click and footbrake it up as high as I can and see what it gets me. I'm gonna repeat 2 more times just changing the shiftlight so I can get that settles once and for all where that needs to be, and go from there.

I will try going up on the tq arm mount to the top hole, see what that gets me, then I'll try adding a 1/2 degree of pinion angle.

The car is close, if it will 1.46 off the footbrake I know it's getting there, I don't know what I should be expecting for 60 foot times at the weight the car is and the power it makes.. I'd like to hope that it can run a 1.39, but I think that might be atretching it, car may just be too heavy for that. At least before the nitrous goes on

 

I recall Magnus messing adjusting his torque arm a few years ago, when he was a very light/ heads and cam car. If he had the torque arm too negative it hit the tires too hard for example. I think some of it is trial and error.

 

About 90% of it is trial and error.

 

Try tightening up your rear shocks to 6 or 7. You might want to think about going to the 325 radials before you use the nitrous. I have basically the exact same suspension setup you listed and with my front shocks at 1 and the rears at 7, off the trans brake I nailed a 1.37. But I also have 325 radials so that might be the difference.