What effect on handling does varying the length and forward attachment point of the torque arm have?

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1984 Camaro Z28 Astral Silver w/ 2 1/2" cowl induction hood
Engine: Decked 383 cid 4 bolt w/ oil cooler, 9.6:1 compression, ARP fasteners, 600 cfm Performer carburetor, Torker II intake, Performer RPM Heads, XE268H cam, Magnum roller tip rockers, MSD6AL ignition, Blaster2 coil, recurved HEI distributor
Exhaust: Terminator headers, Custom 3" TIG welded stainless exhaust, Twister muffler
Transmission: 4L60 w/ Corvette servo, .500 boost valve, TransGo 7-CS clutch springs, 700 PKH pump rings, 700-2 reprogramming kit, Borg-Warner High-Energy frictions & bands, 2400 RPM lockup torque converter
Drivetrain: 2.73:1 limited-slip Dana 44 w/ disc brakes
Tires: Front P225/50VR15 Rear P265/50VR15 Eagles

 

Absolutely nothing. The reason for the torque arm is only to keep the rear end from twisting duing acceleration.

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'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...
http://www.spinfrenzy.com/stingerssx...easures.html#4

 

That's not true, if you go too short, you'll get really bad brake hop.

 

How would that happen?

 

812many is kinda right, but "brake hop" (what ever it is ) will not happen. The length is important in the fact that when you punch the gas, the arm will want to rotate in a upward rotational manner. So if this "Arm" is to short, the rear end will not be forced as hard into the ground (or the rear body forced up into the air) as hard. The "Arm" would be able to lift the rear portion of the car very easily and rotate upward and back. If the "Arm" is longer it will more easily keep the rear grounded under accelaration. This happens because the arm would have to lift (or try to) the whole car in order to rotate upward and back. Basically, the longer the arm, the better the traction. Too short of an arm will equal not enough load on the differential for traction.

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George P. Lara
1984 "L69" A4
1994 LT1 M6
Member:
SCCA, SCFB, SC3GFB

[This message has been edited by MRZ28HO (edited January 15, 2001).]

 

That's more what I was asking. "Handling" wasn't the right word, "behavior" would have been better.

 

Actually the length does not matter as much as the angle and wher it places the "instant center, which should be in the center of the car. Arn't aftermarket torque arms shorter?

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1987 .030 over lg4
too much wasted money
best slip: 14.000@98.7
and it's quicker now.

 

Torque arm length is important. If you want a full understanding of it read a book by Herb Adams called "Chassis Engineering"; I thought it was a great book.

The basic idea is that if the arm is about 30 inches long it can create anti-squat which lifts the rear of the car creating seperation between the tires and chassis. Currently with the current design being so long, the car squats when the power is applied. The downside to the shorter arm, as stated above, is brake hop. This is nothing more than wheel hop under hard braking because the imaginary instant center is now to short.

Either of these setups can work well in drag racing but anti-squat is desirable for road racing because it can better equalize the load on all 4 tires. Old Mopars used anti-squat to the extreme in drag racing with pinion snubbers and they were pretty successful at it.

There are a few aftermarker arms that shorten the length but most still attatch to the tranny or the crossmember. There are many other variable to look at when comparing these different torque arms, such as adjustability or bind. I believe the best setup that is readily available is the Spohn torque arm.

 

The shorter the arm, the more antisquat during foward acceleration. More is usually better for drag racing. But there is a comprimise, the shorter arm will "lift" the rear axle during braking, which would lead to brake hop.
Check out: https://www.thirdgen.org/messgboard/...ML/000554.html

It gets kinda long but is very in-depth about the torque arm suspension.

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87 IROC 350, 3:42 Torsen, pocket ported 083 heads, complete Edelbrock exhaust, Most free mods, Most little mods, aluminum d/s. Edelbrock STB, SSM sfc's, boxed rear suspension pieces, urethane bushings everywhere.
Stock cam, chip, runners, base, and trans
13.94@103mph, 2.25 60'
In the works: ported SLP runners, ported base, Xtreme Cam, homemade suspension pieces, and 27x10 Hoosiers.
Goal: 12.999