My torque arm queston/theory
09-06-2007, 09:45 PM
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My torque arm queston/theory I have been studying the torque arm issue here lately, one of my classes is Chassis and Handling Engineering, where we set up race cars and what not. In the room, we have a brand new late model dirt car chassis that we mess with the set up and what not trying to learn how to set it up. Well yesterday, I got to noticing that this perticular car went with a torque arm setup instead of a four-link or truck arm system.
I asked my instructor why this was and he said it was because these cars have so much horsepower, around 800, and weigh like 2300-2400 pounds, it is easier to get them to hook up with a torque arm. Well the design of the torque arm is something that I have never seen before. It is just a regular bolt on torque arm on the axle, but in the front, it isnt solid mounted like our cars with the drag race style chassis mounted T/A. It is mounted with a adjustable spring and strut. I was asking my instructor why it was done this way instead of mounted solid.
He said that if it was mounted solid, when all the power was put to the rear wheels on the straight it would "shock" the suspension causing it to break loose, so with the spring and strut, it lessens the shock therefore hooks up better. My question is on our cars, why isnt something like this offered or been tried? Seems logical to me that it would work better. Just my .02 though. Sorry for the long post.
Zach
I asked my instructor why this was and he said it was because these cars have so much horsepower, around 800, and weigh like 2300-2400 pounds, it is easier to get them to hook up with a torque arm. Well the design of the torque arm is something that I have never seen before. It is just a regular bolt on torque arm on the axle, but in the front, it isnt solid mounted like our cars with the drag race style chassis mounted T/A. It is mounted with a adjustable spring and strut. I was asking my instructor why it was done this way instead of mounted solid.
He said that if it was mounted solid, when all the power was put to the rear wheels on the straight it would "shock" the suspension causing it to break loose, so with the spring and strut, it lessens the shock therefore hooks up better. My question is on our cars, why isnt something like this offered or been tried? Seems logical to me that it would work better. Just my .02 though. Sorry for the long post.
Zach
09-07-2007, 12:01 AM
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well... dirt versus pavement is part of it. that shock which leads to breaking loose is probably a big problem on dirt. Whereas on pavement, most folks wouldnt want that setup because it "absorbs" some of the energy on launch. For pavement, it would be better in my opinion to have a solid mount torque arm and tires that can stay stuck. Basically you accomplish the same thing with a sprung torque arm as you would by using wrinkle wall slicks, or slipping the clutch a bit or any other method of getting out of the hole without instantly spinning the tires. In fact though, what you want is for the tires to spin for just an instant, then bite down- and off you go. This can be achieved by most of the short torque arm designs already out there and some really good tires
09-07-2007, 01:54 AM
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Originally Posted by OldeSkool
well... dirt versus pavement is part of it. that shock which leads to breaking loose is probably a big problem on dirt. Whereas on pavement, most folks wouldnt want that setup because it "absorbs" some of the energy on launch. For pavement, it would be better in my opinion to have a solid mount torque arm and tires that can stay stuck. Basically you accomplish the same thing with a sprung torque arm as you would by using wrinkle wall slicks, or slipping the clutch a bit or any other method of getting out of the hole without instantly spinning the tires. In fact though, what you want is for the tires to spin for just an instant, then bite down- and off you go. This can be achieved by most of the short torque arm designs already out there and some really good tires
+1
I personally like the sliding link style torque arms such as my personal favorite the Global West Track Link and the UnBalanced Engineering unit. You get the benefit of the long arm and the short arm at the same time. Car feels much better mid corner and I am able to get on the gas just that much sooner. The other advantage is a good reduction in the amount of nose dive under braking so Im able to keep the chassis settled before turn in as well.
09-07-2007, 04:37 AM
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Originally Posted by SVTHuh
+1
I personally like the sliding link style torque arms such as my personal favorite the Global West Track Link and the UnBalanced Engineering unit. You get the benefit of the long arm and the short arm at the same time. Car feels much better mid corner and I am able to get on the gas just that much sooner. The other advantage is a good reduction in the amount of nose dive under braking so Im able to keep the chassis settled before turn in as well.
I personally like the sliding link style torque arms such as my personal favorite the Global West Track Link and the UnBalanced Engineering unit. You get the benefit of the long arm and the short arm at the same time. Car feels much better mid corner and I am able to get on the gas just that much sooner. The other advantage is a good reduction in the amount of nose dive under braking so Im able to keep the chassis settled before turn in as well.
Here is their site; when I saw it last they had a very good page that showed how it works. It may still be here on their site somewhere.
unbalancedengineering.com
09-07-2007, 06:31 AM
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Originally Posted by OldeSkool
well... dirt versus pavement is part of it. that shock which leads to breaking loose is probably a big problem on dirt. Whereas on pavement, most folks wouldnt want that setup because it "absorbs" some of the energy on launch. For pavement, it would be better in my opinion to have a solid mount torque arm and tires that can stay stuck. Basically you accomplish the same thing with a sprung torque arm as you would by using wrinkle wall slicks, or slipping the clutch a bit or any other method of getting out of the hole without instantly spinning the tires. In fact though, what you want is for the tires to spin for just an instant, then bite down- and off you go. This can be achieved by most of the short torque arm designs already out there and some really good tires
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09-08-2007, 09:15 AM
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The stock torque arm IS a spring. The long stamping flexes, and the end is mounted in a big chunk of rubber.
Global West claims a reduction nose dive under braking, which is not desirable at all. Normally, anti-squat in acceleration) goes hand-in-hand with anti-lift in braking. Anti-lift can cause rear axle hop under braking, depending on how much traction you have at the front and rear and how good your brakes are. If you want less brake dive (which is mostly tail lift), the right way to get there is with springs and shocks.
The UE decoupled torque arm does have a rubber snubber at the front, just like a slapper bar. That does act like spring to absorb the shock of a hard launch, but it doesn't store as much energy as the long springy stock arm. The UE arm is also very short, and is set up so that the instant center is high and close to the axle, so it provides a lot of anti-squat under power.
As soon as you hit the brakes, the UE torque arm decouples. With no contact between the snubber and chassis, there effectively is no torque arm. Instead, the sliding link bottoms, effectively changing the rear suspension into a 3-link. The geometry is designed to put the instant center low and forward, which reduces the anti-lift and brake hop tendency.
For an extreme example of anti-lift, hold a yardstick vertically with one hand at the top end. Drag the bottom end across a carpet or pavement while trying to keep it vertical, but press down slightly (enough to get a little drag). Notice how the end grabs, then releases and jumps forward, then grabs again, and so on. That's like brake hop.
And in case you're wondering, yes I do have the UE setup. It's a big improvement both with 275 street tires all around and with 315 race tires all around for autocross.
Global West claims a reduction nose dive under braking, which is not desirable at all. Normally, anti-squat in acceleration) goes hand-in-hand with anti-lift in braking. Anti-lift can cause rear axle hop under braking, depending on how much traction you have at the front and rear and how good your brakes are. If you want less brake dive (which is mostly tail lift), the right way to get there is with springs and shocks.
The UE decoupled torque arm does have a rubber snubber at the front, just like a slapper bar. That does act like spring to absorb the shock of a hard launch, but it doesn't store as much energy as the long springy stock arm. The UE arm is also very short, and is set up so that the instant center is high and close to the axle, so it provides a lot of anti-squat under power.
As soon as you hit the brakes, the UE torque arm decouples. With no contact between the snubber and chassis, there effectively is no torque arm. Instead, the sliding link bottoms, effectively changing the rear suspension into a 3-link. The geometry is designed to put the instant center low and forward, which reduces the anti-lift and brake hop tendency.
For an extreme example of anti-lift, hold a yardstick vertically with one hand at the top end. Drag the bottom end across a carpet or pavement while trying to keep it vertical, but press down slightly (enough to get a little drag). Notice how the end grabs, then releases and jumps forward, then grabs again, and so on. That's like brake hop.
And in case you're wondering, yes I do have the UE setup. It's a big improvement both with 275 street tires all around and with 315 race tires all around for autocross.
Last edited by sgarnett; 09-08-2007 at 09:27 AM.
09-10-2007, 01:10 PM
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Originally Posted by sgarnett
The stock torque arm IS a spring. The long stamping flexes, and the end is mounted in a big chunk of rubber.
Global West claims a reduction nose dive under braking, which is not desirable at all. Normally, anti-squat in acceleration) goes hand-in-hand with anti-lift in braking. Anti-lift can cause rear axle hop under braking, depending on how much traction you have at the front and rear and how good your brakes are. If you want less brake dive (which is mostly tail lift), the right way to get there is with springs and shocks.
The UE decoupled torque arm does have a rubber snubber at the front, just like a slapper bar. That does act like spring to absorb the shock of a hard launch, but it doesn't store as much energy as the long springy stock arm. The UE arm is also very short, and is set up so that the instant center is high and close to the axle, so it provides a lot of anti-squat under power.
As soon as you hit the brakes, the UE torque arm decouples. With no contact between the snubber and chassis, there effectively is no torque arm. Instead, the sliding link bottoms, effectively changing the rear suspension into a 3-link. The geometry is designed to put the instant center low and forward, which reduces the anti-lift and brake hop tendency.
For an extreme example of anti-lift, hold a yardstick vertically with one hand at the top end. Drag the bottom end across a carpet or pavement while trying to keep it vertical, but press down slightly (enough to get a little drag). Notice how the end grabs, then releases and jumps forward, then grabs again, and so on. That's like brake hop.
And in case you're wondering, yes I do have the UE setup. It's a big improvement both with 275 street tires all around and with 315 race tires all around for autocross.
Global West claims a reduction nose dive under braking, which is not desirable at all. Normally, anti-squat in acceleration) goes hand-in-hand with anti-lift in braking. Anti-lift can cause rear axle hop under braking, depending on how much traction you have at the front and rear and how good your brakes are. If you want less brake dive (which is mostly tail lift), the right way to get there is with springs and shocks.
The UE decoupled torque arm does have a rubber snubber at the front, just like a slapper bar. That does act like spring to absorb the shock of a hard launch, but it doesn't store as much energy as the long springy stock arm. The UE arm is also very short, and is set up so that the instant center is high and close to the axle, so it provides a lot of anti-squat under power.
As soon as you hit the brakes, the UE torque arm decouples. With no contact between the snubber and chassis, there effectively is no torque arm. Instead, the sliding link bottoms, effectively changing the rear suspension into a 3-link. The geometry is designed to put the instant center low and forward, which reduces the anti-lift and brake hop tendency.
For an extreme example of anti-lift, hold a yardstick vertically with one hand at the top end. Drag the bottom end across a carpet or pavement while trying to keep it vertical, but press down slightly (enough to get a little drag). Notice how the end grabs, then releases and jumps forward, then grabs again, and so on. That's like brake hop.
And in case you're wondering, yes I do have the UE setup. It's a big improvement both with 275 street tires all around and with 315 race tires all around for autocross.
BTW, I had the GW unit, and it was a GREAT piece. I also have 650# springs up front, which does help with reducing nose dive under braking, but the GW unit help out in spades, and there was absoutly NO brake hop with my setup. I was very impressed, but the UE unit seems to impress me more and more everytime I look at the engineering Jason put into it.
