I cracked my stock torque arm while autocrossing and need a new one, so I might as well upgrade. I've noticed that some move the front mounting point to the crossmember instead of the transmission. Does this provide any real, noticeable improvement over one which uses the stock mount? How exactly does it affect handling?



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Patrick Joyce
96 SS Black
Go, Stop, and Turn mods

 

Obviously, a stiffer/stronger torque arm is better.

The length of the torque arm effects the rate and magnitude of the counteracting force to plant the tires down. As you accelerate, the axle trys to twist. The torque arm counteracts this twist, which is translated into more force being applied to the axle towards the ground. A shorter arm will exert more force more quickly; the force being applied more towards the rear of the car. This tends to lift the rear of the car slightly more under hard acceleration.

The factory torque arm is not bolted (pinned) solidly to the front mount to allow the torque arm to slide back in forth, as the rear suspension moves through its own arc. An ideal replacement T-arm should also allow this, to prevent suspension bind. A "pinned" connection forces the axle to swing in an arc around the front of the torque arm, which will be somewhat in conflict with the different arc of the rear control arms. Therefore, any pinned type torque arms have the potential to bind with the rear suspension.

Also the ideal torque arm should allow some travel on "de-celeration". This is because, just as the tires are planted harder on acceleration, the tires will be lifted on hard braking, due to the counteraction of a rigidly mounted T-arm. The factory and many aftermarket torque arms have this undesirable effect.

I have a HPM "pinned" torque arm of about 60% of the length of the stock torque arm. It plants very hard initially, but then feels like if falls off (ie. when coming on the cam power curve, the tires break-loose more easily after the initial application of power). My suspension does not bind and handles very well. The rear-end does feel a little lighter on hard braking, but very controlable.

However, if I were looking for a new T-arm now, I would probably by 1 of the sleeved type (not pinned) with a spring member for braking. This allows travel on braking to minimize the rear-axle lifting effect. I think that SLP has a good version of this unit. Get 1 that is adjustable too so that you can keep your pinion angle parallel to the engine/transmission on lowered cars (or driveshaft vibration may result).

Good luck,
Rick R

 

Does Spohn make anything like TA you described?

 

Pat,Bummer this could happen to any of us.Maybe me soon.
I just wanted to ask I-corner.How is the arm your describing,60% shorter?Are you speaking of tolerances,or overall length?
Couldnt be length

 

Thanks, I Corner. I had a friend weld my stock one for now since I corded my front tires at the last event. But I will be getting a TA this winter, and I'll check out the SLP one.

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Patrick Joyce
96 SS Black
Go, Stop, and Turn mods

 

Your side view instant center will move slightly if the forward TA mount is relocated in the fore/aft direction from OE, fractionally changing the anti-squat & anti-lift. The main benefit of relocating this attachment to the crossmember is to remove any suspension-related loads from the transmission case/tailshaft.

Norm



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'79 Malibu, way not stock (355, 5 speed, . . .)
'95 Mazda 626 V6 5 speed, not entirely stock either
'01 20th AE Maxima, 5 speed, stock (so far)

 

The factory torque arm (& many aftermarker T-arms bolt to a bracket to the rear of the transmission. The HPM uses a "K" brace which
- replaces the factory stamped cross brace,
- provides a driveshaft safety loop,
- braces to the left rear trailing arm bolt and
- relocates the mount for the shorter T-Arm further back near crossbrace.

Seems to work well with the Kenne Brown double diamond subframe connectors.

As I said the only downside, is the pinned connection to the front.

Rick R

 

I-corner thanks for clarifing this(answering Q That would be alot shorter.
T.

 

I Corner:

Re your TA.

I have a daily driver that will probably see equal time at the drag track as well as auto-x.

I have been leaning toward the spohn. Would the arm you speak off be better for my situation.



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1997 T/A WS6 Con

383, ATI Procharger D1-SC @15#, relocated MAF, FLP's, Borla, Kenny Brown DD SFC's, Hal's, SLP-Springs, STB, sway bar, shifter-Lou Salzano SS, 5-point chrome roll bar, ZR1 rims, KTRE 12 bolt 3.73's. etc etc.

Best 12.30 @ 121.79- "Traction.....we have a problem"
527 RWHP / 570 lbs.

 

I have a G2 Torque Arm. It eliminated all my braking wheel hop and many drag racers are seeing consistant 1.60 60's.

It uses all the stock mounting points, so it requires no drilling, welding or other modification/fabrication to install it.

Using the factory mounting points means there are no clearance issues either. IF you can drive over something with the stock arm, you can do it with the G2 arm. The same can be said about DSLs, Subs, etc.

It has a rod end design on the front mount so that the arm can move freely in any direction, including plunge, while maintaining the factory designed pinion angle, and have zero bind.

It weighs less that the factory unit and is much stronger.

And it's currently on sale at 25% off.
http://www.ls1.com/forums/showthread...hreadid=145272

Now how can you beat that!

 

The Spohn looks like a stout piece and looks longer than my HPM. The effects of long vs short T-Arms are explained in the Emails above. The Spohn has a rod end on the front (pinned connection), so it has a small potential to bind (different pivot arc than the rear lower control arms). However, my HPM is also has a pinned connection and does not bind through full suspension travel. My car does not handle adversely, as far as I can tell. But if I had to do it over again, I would purchase a sliding front connection. Global West (I hate to refer them just now, because of a front adjustable height suspension design problem) makes a strong track arm (torque arm) with a sliding front connection.

As for lifting the rear axle under hard engine braking, the SLP design to allow travel in that direction makes alot of sense. I could not easily find a photo of the SLP design on their current website, but I have received mailers previously. I don't know if they still make it. Look for yourself and decide.

Man, you are making some serious power with your setup! My car might handle very well, but I am looking forward to reaching your level of street-able performance. Good job! How do you like the ATI blower?

Good Luck.
Rick R