torque arm configuration, suspension tuning...

[DavidBoren]

From everything I have read, most people who use a torque arm set it up for 100% anti-squat. This generates brake hop, which may be fine for a drag racer, but not a daily driver.

Is there a middle ground for setting up a torque arm for a more neutral handling vehicle? Does 100% anti-squat guarantee 100% brake hop? Would positioning the torque arm for 50% anti-squat generate only 50% brake hop? Can I bias/proportion the brakes to counteract the negative effects of the torque arm? Can springs and/or shocks be adjusted to keep the vehicle neutral in both acceleration and braking?

My goal is to create a vehicle that is neutral in both steering and handling. From what I can gather, keeping the control arms parallel to the ground and mounted in front of the axle center line will be the most neutral position for those. The torque arm length and position is what influences the anti-squat, and this characteristic is expressed as a percentage based on virtual geometry lines pertaining to the height and weight (distribution) of the vehicle.

I am kind of new to this suspension business, but I am fascinated by it and want to learn what it takes to build a good handling suspension for road racing/autoX/daily driving. I know you can't have the best racing suspension if you want to drive it on the street. Compromises must be made. I want neither oversteer or understeer. I want a responsive, neutral, and above all else predictable handling vehicle.

Anyone with experience adjusting suspensions? This is more a debate on theory right now. But I would appreciate any help or advice you have to offer.

 

[DavidBoren]

*moderator, can you please move this to the general suspension tech section*

 

[RichV]

What do you mean on configuration. How do you configure a torque arm?

What is there to configure? It just bolts to the axle and under the tunnel. I've never installed one myself but have checked them out at the race track many times.

Do you mean for the LCAs and pinion angles?

*Moving now.

 

[RichV]

Maybe a de-coupled torque arm. Not sure if anyone makes one for our chassis.

I'd just go with a MM or Griggs and not worry about configuration. Set it and forget it!

 

[ReplicaR]

I've had a MM Torque Arm in my car for... some amount of years now. I've never had wheel hop in it. Ever. Not under any kind of condition, and I more than daily drove it.

 

[evilcw311]

Sounds like your referencing the adjustments that adjustable upper control arms give you. Torque arm isn't quite adjustable as such. Upper control arms allow you to adjust rear end geometry to control preload on the rear end. Lowers allow you to control placement of the wheel from front to back in the rear wheel wells.


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[RichV]

Ya, not sure since most remove the UCA when you add a T/A and a PHB.

That would be the ideal setup, along with some good COs at all 4 corners. Darn CMC rules!!

 

[rz5.0]

It really sounds like you are referring to lower control arms. . Some come with relocation brackets to do what you are taking about. Like the HP megabites sr

 

[DavidBoren]

I am not talking about the lower control arms, although they would play a part in the anti-squat percentages. For the most part, lower control arms are generally mounted parallel to the ground, level with or below the axle center line.

The torque arm can be mounted below or above (if there is room) the axle. You could easily have a height adjustable mount where the front of the torque arm connects to the chassis. You can have shorter or longer torque arms. All of this affects the angle of the torque arm and your instant center and the amount of anti-squat.

I am sure that MM and Griggs have tried and tested about every combination of lengths and angles that will physically fit under the SN95, and they probably offer an excellent install and forget product, but I am wanting a system designed for adjustment. I want to learn how subtle changes in geometry affect the handling and performance of the suspension. And I was wondering if anyone here has delved into really testing their own mounting points and geometry.

I am just curious. I find suspension design very intriguing and would love to hear from anyone who has went above and beyond bolt-on pre-manufactured kits.

 

[rz5.0]

There is a guy on here I can't remember his whole user name. . Poxehan or something like that. . He makes all kinds of parts.. maybe he can help. .

 

[ReplicaR]

DavidBoren, I'm just curious, what is that you are trying to find, aside from wheelhop? I think prior to trying to reinvent the wheel, maybe you should drive a MM or GR Torque Arm car, and then then make your decisions about what you would like to do. I've never once had an issue with wheel hop, not under acceleration, cornering, braking. I've heard of people complaining about it, but never experienced it on my own, and I've got track pads and tires front and rear. I tend to believe that MM has put enough R&D into this piece to be the most effective that it can be. The only time I've ended up going further than MM, is when I adapted rear helper springs for coilover kit, and MM said that it couldn't be done (also known as, we don't want to bother with it).

 

[Evilgt]

Is there enough room back there to build a effective T/A that is adjustable? Dont want to sound like a jerk here however why try and reinvent the wheel? Follow some of the american iron or A sedan racers. If there is a advantage in building such a thing they would have done it.

kyle

 

[DavidBoren]

I would like to be able to adjust the length/angle of the suspension components so I can learn what geometric changes equate to different handling characteristics. All the R&D has been done with a bolt in kit, but that learning process is what I am after. I want to learn and experience what it takes to build and tune a neutral handling suspension.

 

[Pete@FTR]

Griggs and MM have spent a lot of time perfecting their torque arm to provide the best balance for our cars. I had a conversation with Bruce where he said in their testing they were able to cut the braking distance of a stock mustang (cant remember which chassis) in half just by upgrading the pads and adding a torque arm. The anti-lift properties of the torque arm really balance out the balance and allow much more effective braking.

That being said, every off-the-shelf piece for sn95 chassis mustangs are pretty much the same, they mount under the axle. In contrast, the a-47 harbinger x2 uses a over the axle design that mounts in the cabin. I'm not sure if theirs is adjustable, but I have seen other cars with this style torque arm add a lot of adjustment into their design. My current build is a 99 gt with custom front and rear suspension will be running this style torque arm, but my own take on it.

A de-coupled torque arm aims to provide the best of both worlds. Having never used one personally, I couldn't speak too much to the effectiveness besides the theory. Here's a good technical article. It's specifically for camaros but the same concept applies.

http://www.unbalancedengineering.co...balanced Engineering Decoupled Torque Arm.pdf

I'd recommend getting a book on chassis design and a copy of Performance Trends's suspension analyzer software so you can play with the geometry and see what it will do.

There is a guy on here I can't remember his whole user name. . Poxehan or something like that. . He makes all kinds of parts.. maybe he can help. .

hahaha. Here I am.

 

[ttocs]

so if I am reading this correctly you are just wanting to set up the best quality DD suspension for your car? Is it just to learn about something you are curious about or are you going to take this knowledge/car to the track?