I've read a couple installs on the aftermarket T56 which required shortening the torque arm about 2 inches.

What does that mean for suspension geometry and characteristics?

I'm fabbing a custom crossmember for my T56 and may end up with the torque arm mount on the crossmember. I'm just curious if i have any leeway with torque arm length when i fabricate this.

 

With all other geometry suspension angles remaining factory, the shorter TQarm will move the IC (instantaneous center) rearward and weight transfer leverage will load the rear tires more.

I am assuming you want to know for Drag racing purposes?

Roadracing it can help promote rear wheel bite coming out of a corner and help balance the attitude of a car on exit- it can hurt also if too much.

The shorter the Tq arm the more prone the rear end can become to braking wheelhop unless higher compression shocks and/or stiffer rear springs are used.

 

so shortening the torque arm might even be a worthwhile modification, as opposed to one that is only not going to hurt much.

Why is the torque arm as long as it is for stock purposes?

and how short is "too short"?

I'm thinking max 2-3 inches shorter for my purposes.

 

You won;t have a problem with that. The one we make at work is a few inches shorter than the normal one. The 4th gen one is about half the size of a stock one. Honestly I don't think that I ever read anyone that ever had a problem with a torque arm being to short. Well to a point


Kat

 

thanks for the input guys

 

First, shortening the TA does move the IC of the rear suspension back by an equal proportion as the amount that you shorten the TA, but it also moves the IC down. The combination prevents any really big gain in anti squat. You would have to shorten the TA something on the order of >6” for every ˝”-1” that you lower the rear LCA pivot to get the same change in antisquat (the amount changes as the LCA angle increases from perpendicular to the ground). Unfortunalty, increasing the LCA downward angle also hurts handling (corner entry oversteer and exit understeer).

Second, the length is there exactly for controlling wheel hop. If you stiffen the stock length TA and increase the rear brake bias enough you will come very close to getting brake hop if you had sticky enough rear tires. Most people with shorter TA’s don’t see it because in stock configurations these cars have so little rear brake bias that it can’t happen.

 

is shortening it 1-2" going to matter at all then?

I hopefully don't have to shorten anything, but i am fabbing up a x-member for the T56 and i might as well move the torque arm mount off the tranny while i'm at it...and that might require shortening.

 

It always matters… but will you feel a difference? No, you’ll feel a bigger difference from if whatever you do ends up stronger/weaker then stock then you will from the change in geometry.

 

You guys gotta see my homemade 16" decoupling tq arm with sliding link. Pics coming soonalong with test results. This was entirely designed for road and Auto-x racing.