Traction problems?

[Mike]

... any time a body spends going down is still wasted time...

Actually, any time a body spends moving either up or down is wasted time. Hence the four link, which provides forward bite. No matter the tire being used, I want the car moving in one direction only - forward. If you cannot make a car move forward, then you are correct in saying you need the rear suspension to try lifting the car. But every instant the body is separating, it is NOT moving forward.

The simplest and most effective traction device I've ever used on a street car is an adjustable pinion snubber, with no need for torque arms mounting to the trans.

It just baffles me how much knowledge is on this board!

It's good to hear you say that. I've just been made aware a former member of the site has announced on his own site none of us around here know a darn thing.

When did they switch the headers to well, headers instead of just straight pipes? I always thought they used the down force of the exhaust for traction purposes (yeah I am showing my ignorance)

That car is naturally aspirated, hence the collector-style headers. And yes, the fuel cars will use header down force to help plant the tires. That's why you'll often see a fuel car moving out of the groove if it puts out a couple of cylinders on one side. It loses down force on that side, letting the car move around.

 

[Ted Brown]

Mike, I am glad you mentioned a pinion snubber, that works the very same as a lift bar, (it is a lift snubber) that instantly plants the tire, so forward movement happens quicker and now not depending on rear springs to enter into the traction problem, as they do not hold the chassis up when under full pedal, the lift snubber does... The 4 link works wonders to adjust the weight from one wheel to another, keeping things going in a straight line much easier to work with than the old style lift bars

 

[Keeper]

That car is naturally aspirated, hence the collector-style headers. And yes, the fuel cars will use header down force to help plant the tires. That's why you'll often see a fuel car moving out of the groove if it puts out a couple of cylinders on one side. It loses down force on that side, letting the car move around.

Glad to know I wasn't to far out to lunch.

I never even noticed it was naturally aspirated, cannot say I have ever seen a dragster without a blower! (I don't get to the races up here very often)

 

[Ted Brown]

Well I find that I kinda started a fire storm, when really all I wanted to do was try and make some of these Rockets a bit safer... What do I mean by safer when talking about traction?? I have built more cars than I can remember over the years, but have fixed or tried to fix many more along the way...
Here is just one example;
I always take the cars out for a test run to see how they handle, steer and stop... here is the biggest problem that MOST T Buckets or light weight hot rods have in common, they do not have any traction!!! The owner's tell me they do just fine, they do not do just fine!! They are and accident waiting to happen, they are like a loaded 44 mag with a hair trigger and no safety, in the hands of a child... It is not a matter of IF, but WHEN!! Driving along at say 30 miles an hour, or whatever... and hit the go pedal, the car is now sideways, pretty much... This is what I mean about, do you have traction problems, not just in a drag race... I know all about drag race cars, that is what I did for more years than I even liked, as they got way too fast and quick over the years for me to feel comfortable about leaving that 44 in someone else's hands, but what can you do? I just pray for them and hope my welds and work were correct enough to keep them all together in one piece...

There is no winning in talking about how things are done in the race World, after all this is what it is all about, never give away the real facts to how you put together a real winning car... Always old news, never today's secrets... I have been apart of many stories about race cars in different Mags. Always was last years news about all the real trick stuff... You can't win telling ALL your inside stuff to the competition... If your ride has slippery tires, don't hit that go pedal hard...

 

[Mike]

Ted, I don't think it's a fire storm at all. It's just a situation of technology doesn't wait around for anyone and we all have to fight to keep up.

Every single car in the world has a very specific spot around which the the entire car will balance. This spot is not identical on all cars and changes with things like the driver's weight. But this spot, known as the center of gravity (CG), is always there. We cannot deny its existence, agreed?

Next. No matter the type of car, its rear suspension will pivot around a specific point. But (and this is important), the point around which the suspension pivots is not necessarily the same point where the given rear suspension is going to apply power (or lift, if you prefer to use that term). Are we still in agreement, here?

The point where the given rear suspension applies power is what we call Instant Center (IC). Different suspensions and even different suspension components will change the placement of IC, agreed? In other words, IC is the center of an arc created as the suspension links move. On a car equipped with a ladder bar (or, again, a lift bar, if you prefer), it is dead simple to identify IC. The center of the bolt attaching the front rod end of a ladder bar is the point of IC. It's right there, visible to the human eye, agreed? If the car uses leaf springs without any other traction device, IC is located at the center of the front spring eye. Agreed?

But if the car uses rear coils and upper and lower control arms, then IC has to be calculated, as there is no way for you to see the theoretical intersection point between the upper and lower links. Agreed?

We can take a scale drawing of the car and plot that intersection point, by extending the lines created by the upper and lower links. This drawing will then give us the IC point, agreed?

But here is where you're going to have to start sketching and thinking as we go. If we draw a horizontal line through the CG and then draw a vertical line through the front spindle, we will create another intersection point. Still with me on this one? Now, we're going to draw yet another line, from the centerline of the rear tire contact patch through the intersection of the CG and spindle lines. This last line is called our neutral line and is sometimes called a 100% anti-squat line.

With those ladder (or lift) bars, the relationship between IC and the 100% anti-squat line will always be the same. Agreed? It cannot change, because the front mounting point of those bars is fixed.

Now, you can start to see what happens with an adjustable 4 link suspension. By moving the mounting location of the upper and lower 4 link bars, I can put IC anywhere I want. I can put IC directly on the 100% anti-squat line. Or I can put IC above it or below it. Still with me, here?

If I position IC at any point below that 100% anti-squat line, when I hit the gas, the car is going to squat and hit the tires in a softer manner. On the other hand, if I move IC above the 100% anti-squat line, the rear of the car will rise on acceleration, hitting the tires harder. Which brings us to the possibility of placing IC directly on the 100% anti-squat line. With that adjustment, the rear of the car will remain neutral on acceleration.

OK, think about how the upper and lower control arms are positioned on a car rolling off the assembly line. If we extended the lines from those links forward to an intersecting point, that point is going to generally fall well forward of the front bumper. That means our IC is way down below the 100% anti-squat line. Stand on the gas and what happens? The rear of the car will squat. Remember when all the Chevelle guys had to have those old Lakewood upper control arms for their cars? They worked a treat, because they raised the rear locating point of the upper control arms by a couple inches, moving the IC point back in the car and getting it above the 100% anti-squat line. Now, the rear of the car would rise on acceleration, sticking the tire harder.

So, if we want to plant the tire, we want that IC to be as high as we can get it above the 100% anti-squat line, don't we? Absolutely not!

And you thought you had a real good handle on all this, didn't you? Well, you've forgotten the fact that we are going to reach a point where the cars has moved far enough that all our "lifting leverage" is gone. Then what happens?

As the car starts returning to a neutral height, our instant center starts dropping. Quickly. And those tires we planted so hard are now going to unload and spin. So we can't try to take too much off the table, because we're going to be required to put it all back and that's what catches us up.

But wait, what is all this talk about upward and downward body movement? If I'm sitting at a light and stab the throttle, do I want the rear of my body to move up or move down?

NEITHER!! I want the car moving forward. I'm not trying to move up. I'm not trying to move down. I'm trying to move forward. I want to apply the least amount of downforce to the rear tires that I can get away with. Every thousandth of a second the body is going up and the sidewall of the tire is wrinkling from the additional weight placed on it is just another thousandth of a second that the car is sitting static and not moving forward. And the more body separation I achieve at the exact moment of acceleration is going to come back to haunt me by unloading the tires that much more within the first 30 feet of motion.

A car sitting at rest has 100% rear tire traction. The guy that is going to move his car the most efficiently is the guy that can keep that percentage as close to 100% as possible, whilst moving the car in a forward direction. So I want a car set up with Instant Center falling at a point just ahead of the Center of Gravity and just above the 100% anti-squat line, which will raise the nose of the car. Then I can limit front suspension travel so the front end cannot raise much more than an inch or two. Now I am working the rear tire of the car as hard as I can work it, but I am also using the torque reaction of the rear end to push the car forward. The finish line is in front of you, not above you or below you. It can take a lot to sort what length the upper and lower links should be and where the mounts for each end should be, in order to achieve the sweet spot.

In a dragster with no rear suspension, you can change rear weight percentages with adjustments to front tire pressure and by raising or lowering the front motor plate. Ever notice where the crank centerline ended up on some of the old Fuel Altereds? Look at some old photos of the Pure Hell car for a drastic example.

Maybe this will clear up all the misunderstanding on how a triangulated, 4 link suspension works.

(OK, Ron, so I lied! :rofl

 

[EX JUNK]

Thanks Mike, for that EXCELLENT technical explanation of how a 4 link works.

Jim

 

[Ted Brown]

Mike, I hope you did not aim that at me, I understand all of that suspension business, even the 4 links, that look like hell under a T bucket, I want a T bucket to look like a T Bucket, not an altered, and I do know how to keep the right amount of weight on the rear all the way down the track... I may be old but not dumb when it comes to getting out of the gate quick and staying hooked up the rest of the way down the track, but I hope we are not talking that type of car here on this forum, I myself want looks, comfort, safety and legal... agreed on this?

 

[Gerry]

Mike
Ive read your post 3 times and i am still trying to get my head around the physics. If I knew as much as you have forgotten then I would be a happy bear.
gerry

 

[RPM]

Ted, I don't think it's a fire storm at all. It's just a situation of technology doesn't wait around for anyone and we all have to fight to keep up.

Every single car in the world has a very specific spot around which the the entire car will balance. This spot is not identical on all cars and changes with things like the driver's weight. But this spot, known as the center of gravity (CG), is always there. We cannot deny its existence, agreed?

Next. No matter the type of car, its rear suspension will pivot around a specific point. But (and this is important), the point around which the suspension pivots is not necessarily the same point where the given rear suspension is going to apply power (or lift, if you prefer to use that term). Are we still in agreement, here?

The point where the given rear suspension applies power is what we call Instant Center (IC). Different suspensions and even different suspension components will change the placement of IC, agreed? In other words, IC is the center of an arc created as the suspension links move. On a car equipped with a ladder bar (or, again, a lift bar, if you prefer), it is dead simple to identify IC. The center of the bolt attaching the front rod end of a ladder bar is the point of IC. It's right there, visible to the human eye, agreed? If the car uses leaf springs without any other traction device, IC is located at the center of the front spring eye. Agreed?

But if the car uses rear coils and upper and lower control arms, then IC has to be calculated, as there is no way for you to see the theoretical intersection point between the upper and lower links. Agreed?

We can take a scale drawing of the car and plot that intersection point, by extending the lines created by the upper and lower links. This drawing will then give us the IC point, agreed?

But here is where you're going to have to start sketching and thinking as we go. If we draw a horizontal line through the CG and then draw a vertical line through the front spindle, we will create another intersection point. Still with me on this one? Now, we're going to draw yet another line, from the centerline of the rear tire contact patch through the intersection of the CG and spindle lines. This last line is called our neutral line and is sometimes called a 100% anti-squat line.

With those ladder (or lift) bars, the relationship between IC and the 100% anti-squat line will always be the same. Agreed? It cannot change, because the front mounting point of those bars is fixed.

Now, you can start to see what happens with an adjustable 4 link suspension. By moving the mounting location of the upper and lower 4 link bars, I can put IC anywhere I want. I can put IC directly on the 100% anti-squat line. Or I can put IC above it or below it. Still with me, here?

If I position IC at any point below that 100% anti-squat line, when I hit the gas, the car is going to squat and hit the tires in a softer manner. On the other hand, if I move IC above the 100% anti-squat line, the rear of the car will rise on acceleration, hitting the tires harder. Which brings us to the possibility of placing IC directly on the 100% anti-squat line. With that adjustment, the rear of the car will remain neutral on acceleration.

OK, think about how the upper and lower control arms are positioned on a car rolling off the assembly line. If we extended the lines from those links forward to an intersecting point, that point is going to generally fall well forward of the front bumper. That means our IC is way down below the 100% anti-squat line. Stand on the gas and what happens? The rear of the car will squat. Remember when all the Chevelle guys had to have those old Lakewood upper control arms for their cars? They worked a treat, because they raised the rear locating point of the upper control arms by a couple inches, moving the IC point back in the car and getting it above the 100% anti-squat line. Now, the rear of the car would rise on acceleration, sticking the tire harder.

So, if we want to plant the tire, we want that IC to be as high as we can get it above the 100% anti-squat line, don't we? Absolutely not!

And you thought you had a real good handle on all this, didn't you? Well, you've forgotten the fact that we are going to reach a point where the cars has moved far enough that all our "lifting leverage" is gone. Then what happens?

As the car starts returning to a neutral height, our instant center starts dropping. Quickly. And those tires we planted so hard are now going to unload and spin. So we can't try to take too much off the table, because we're going to be required to put it all back and that's what catches us up.

But wait, what is all this talk about upward and downward body movement? If I'm sitting at a light and stab the throttle, do I want the rear of my body to move up or move down?

NEITHER!! I want the car moving forward. I'm not trying to move up. I'm not trying to move down. I'm trying to move forward. I want to apply the least amount of downforce to the rear tires that I can get away with. Every thousandth of a second the body is going up and the sidewall of the tire is wrinkling from the additional weight placed on it is just another thousandth of a second that the car is sitting static and not moving forward. And the more body separation I achieve at the exact moment of acceleration is going to come back to haunt me by unloading the tires that much more within the first 30 feet of motion.

A car sitting at rest has 100% rear tire traction. The guy that is going to move his car the most efficiently is the guy that can keep that percentage as close to 100% as possible, whilst moving the car in a forward direction. So I want a car set up with Instant Center falling at a point just ahead of the Center of Gravity and just above the 100% anti-squat line, which will raise the nose of the car. Then I can limit front suspension travel so the front end cannot raise much more than an inch or two. Now I am working the rear tire of the car as hard as I can work it, but I am also using the torque reaction of the rear end to push the car forward. The finish line is in front of you, not above you or below you. It can take a lot to sort what length the upper and lower links should be and where the mounts for each end should be, in order to achieve the sweet spot.

In a dragster with no rear suspension, you can change rear weight percentages with adjustments to front tire pressure and by raising or lowering the front motor plate. Ever notice where the crank centerline ended up on some of the old Fuel Altereds? Look at some old photos of the Pure Hell car for a drastic example.

Maybe this will clear up all the misunderstanding on how a triangulated, 4 link suspension works.

(OK, Ron, so I lied! :rofl

Right on the money. A great explanation of how a modern hot rod suspension is engineered and tuned.

 

[Telman2]

I've been a member here for 2 years and this has got to be one of the best and most informative threads I've read here.

 

[ellis8500]

This post has gotten a lot of traction..........

 

[Mike]

Mike, I hope you did not aim that at me, I understand all of that suspension business, even the 4 links, that look like hell under a T bucket, I want a T bucket to look like a T Bucket, not an altered, and I do know how to keep the right amount of weight on the rear all the way down the track... I may be old but not dumb when it comes to getting out of the gate quick and staying hooked up the rest of the way down the track, but I hope we are not talking that type of car here on this forum, I myself want looks, comfort, safety and legal... agreed on this?

1. Ted, to make myself clear, I was not "aiming" anything at anyone. There was some considerable misunderstanding as to the effectiveness of a 4 link rear suspension (even from yourself, referencing post #3 in this thread) and I have tried to clear that up. A properly adjusted 4 link will not be a "hide burner", in any sense of the phrase. An improperly adjusted 4 link is as worthless as a lift or ladder bar that has been manufactured to an incorrect length or mounted improperly. This is 2010, not 1965. We're not trying to hook a car on a 9", hardwall slick, here. We now have the added technology of better tires, better tire compounds, better sidewall engineering, etc. And I'm talking about all types of tires, not just drag slicks. If anyone thinks tire technology is still stuck in the dark ages, come look at the original tires on my 2001 Dakota, that have 78,000+ miles on them.

2. As for a 4 link combination looking "like hell", please take another look at the second photo in post #9 of this thread and explain how that does not look extremely clean to the eye. If that was my car and you suggested it looked like hell, there would be a helluva fight and you would be in it. :winkn:

3. On one hand, I fully understand what you mean when you say you want your car to look like a T-Bucket. On the other hand, define how a T-bucket is meant to look. Is my own T not going to look like a T-bucket, because it uses a laid-back, Performer style windshield? Or because the fiberglass seat insert is going to allow me to sit down in the car and not sit atop the car on a padded bench?

4. With all due respect, how do you keep the right amount of weight on the rear tires of a drag car, all the way down the track? What experience do you have setting up three-position, pneumatic-operated, electronically-controlled shocks on the rear of a drag car? What shock setting do you use on the starting line? What setting do you use for a track with a notorious bump in one lane? Are you going to stiffen or soften the shocks at the 330' mark? Are you going to run string transducers on both front shocks, or just one? Or is the starting line so terrible that you are going to use base and counterweight adjustments on the clutch, to get the car to make its initial move? How much clutch disc wear is acceptable? At what point of disc wear are you going to know how hard you had the tires stuck on the car? What changes are you going to make if you're trying to get the car into 4th gear, just as it hits a bump on the track?

The bottom line to all this can be rendered down quite easily. In the late 60's, you fellows may have needed those straight-axle front ends to get the nose of the car up in nosebleed zones. Today's chassis engineering has improved to the point where weight transfer can be done without those tactics. We can get the front end of the car down on the ground, so air passes over the top of the car, rather than through the aerodynamically filthy undercarriage. Power-robbing hydro transmissions have been replaced with an incredible array of clutch disc material recipes and five-speed clutchless transmissions. Those old 9" and 10" hardwall slicks have been replaced with 17" tires with more engineering in the sidewalls alone than your old tires had, top to bottom. What were you making with those "high horsepower" blown Hemis, back then? A horsepower calculator shows they were good for about 650 HP. Ted, we make that kind of horsepower out of a 265", naturally-aspirated V-6. If I run the current Pro Stock records through the same horsepower calculator, I get a tick over 1610 horsepower. Today's blown alcohol motors are good for about 3200 horsepower.

Think about this. If you could have made 700 HP with one of those old, blown Hemis (and let's be honest, that was a stretch), that would not be enough HP to spin the blower on one of today's Top Fuel cars at the finish line.

I do hope you see I am not getting on anyone's tail, nor am I knocking any of those old Gassers. They were merely one step in the technological chain that has brought us to where we are today. What used to be state-of-the-art chassis technology is no longer. I love the old cars. I like the looks of them and I enjoy watching how people "engineered" those cars to make them run as well as they did. But that doesn't change the fact that none of those old cars can hold a candle to a car built with today's technology.

I completely agree with you on the concept of looks, comfort, safety and legality. But let's be honest enough to say concepts like looks and comfort are in the eyes of the beholder. While the look of a tall, straight windshield has a classic T-Bucket appearance, that's not how I want my car to look. I don't plan to use carriage lamps on my car either, although they really work well on some cars. The look of an upholstered deck cover can really catch someone's eye, but I'm using a hard deck lid, that carries through the styling brought in by the seat insert. The seat insert that lets me sit down into the car and not ride on top of it. And whilst some fellows prefer no seat belt at all and some prefer to bolt belts to the floor of their bodies, I plan to mount belts to an add-on crossmember, welded to the frame rails. A crossmember that I can hopefully incorporate a driveshaft loop into, to prevent having to add a second crossmember. By building with that kind of safety in mind, I have no doubt the car will be legal.

But those issues have nothing to do with the concept of how well a 4 link suspension will work, or how the use of a 4 link can clean up the lines of a car. That's where this thread was heading some 10-12 posts back and that is what I am still try to address now.

And you do realize why GM engineered that terrible torque link into the later Camaro/Firebird platform, don't you? It didn't have spit to do with the effectiveness, they were trying to scoot the rear seat back a few more inches to gain some rear leg room and using conventional-style control arms wouldn't allow the body pan to get so close to the rear end. And I'm going to take the word of the GM engineer who explained that to me. :nod:

 

[Keeper]

This post has gotten a lot of traction..........

HAHAHA nice shot.

 

[Ted Brown]

Got me, I am dead in the water...

 

[deckofficer]

Got me, I am dead in the water...

I avoided the water burn out box at Sacramento Raceway.

 

[Mike]

I think tire technology is getting to a point where the burnout is no longer as necessary as it once was. I remember Jim Head was playing with that a few years back. His guys would lay sheets over the water box and Jim would just do a very short, dry burnout to clean the tires.

But if you did away with the burnouts, the fans would groan. And to be honest, nearly every driver would do the same. I've never met a driver who wasn't all jazzed up about being Sammy Showboat on the burnout. hthedrama:

 

[RPM]

I just wanted to post this. It is my in laws Worlds Fastest Harley Truck. This is a picture of the record pass that Trick Flow is going to use in some advertising. 7.65 at 185 mph. This truck weighs in at 3200lbs.

This was a brand new truck with 17 miles on it when they cut it up. A funny car type chassis with a 4 link, a blown 4.6 Ford, and a Lenco trans.
Notice the rear tires.

 

[Northstar T]

I just wanted to post this. It is my in laws Worlds Fastest Harley Truck. This is a picture of the record pass that Trick Flow is going to use in some advertising. 7.65 at 185 mph. This truck weighs in at 3200lbs.

This was a brand new truck with 17 miles on it when they cut it up. A funny car type chassis with a 4 link, a blown 4.6 Ford, and a Lenco trans.
Notice the rear tires.

which part of that truck is from a Harley?

Russ

 

[RPM]

Craig the driver holds a Pro Mod and a Only thing left is the shell of the cab, which still has the factory vin tags on the door jamb and the part of the dash that has the vin tag. They had to retain this to prove from the vin numbers that it is in fact a Harley truck..

They are hoping to go over 200 mph next season. Craig the driver holds a NHRA Pro Mod and a Pro Stock drivers license.