Truck Rake

JMO, rake means nothing whatsoever. Guys get all wound tight about it, and I hear all kinds of BS about "leverage" but few or none of those guys have ever put pencil to paper to quantify what's actually going on.

If the rules state that the hitch must be rigid in all directions, then artificially raking the truck is not much more than mental masturbation. You could jack up the frame to run the ass 10 feet in the air - but if the hitch point is at 26", what possible difference will it make?

If the rules allow pivot and trick hitches, all bets are off and geometry does come into play. But I have never seen rules that loose.

The Mod trucks are built without rake, and they seem to do fine. Enough said?

Setup and travel and weight distribution and spring rate are FAR more important than what angle the frame sits at.

Assuming you have a stable truck that doesn't bounce, hell, tire selection and air pressure coupled with the final drive ratio used are light years more important than how the truck sits.
 
just curious if a person wanted to drop a dodge in the rear what is a correct way use a smaller block between perch and spring or a shackle i measured mine its a 94 2500 measured 37'' in the front and 45'' in the rear took measurements at the center of fender well area how much would you guys drop it 4'' ? i have 1000lbs hanging on the front not sure what the box weighs thinking i can hang another 500 to 600lbs on it i agree on the fact of close to level truck i have nothing on hand or on pencil or paper to back up the diffrence of rake or non rake but ill try anything to get the truck to run better thanks guys Tony
 
nwpadmax said:
JMO, rake means nothing whatsoever. Guys get all wound tight about it, and I hear all kinds of BS about "leverage" but few or none of those guys have ever put pencil to paper to quantify what's actually going on.

If the rules state that the hitch must be rigid in all directions, then artificially raking the truck is not much more than mental masturbation. You could jack up the frame to run the ass 10 feet in the air - but if the hitch point is at 26", what possible difference will it make?

If the rules allow pivot and trick hitches, all bets are off and geometry does come into play. But I have never seen rules that loose.

The Mod trucks are built without rake, and they seem to do fine. Enough said?

Setup and travel and weight distribution and spring rate are FAR more important than what angle the frame sits at.

Assuming you have a stable truck that doesn't bounce, hell, tire selection and air pressure coupled with the final drive ratio used are light years more important than how the truck sits.
Click to expand...

but you also got to look at the vertical centerline of your rear suspension too and how it will compress (think of where the center pin points).....a level truck has a centerline at 90 degrees and the suspension will relatively compress straight down when pulled down on and that will cause your traction bars to become a lift point where ever they are connected to the frame, raising the nose and transfering weight to the rear, and a taller suspension or hitch height will increase this exponentially (think 2wd blower truck with the nose 5 feet in the air going down the track)........now rotate that angle forward (rake) and now your actually trying to compress the suspension backwards......and when that happens your traction bars are now pulling down on the frame planting the front end......

but all of this can be affected also by weight, type of suspension, movement of the suspension, length or type of traction bars, driver, hitch type, color of the truck and alot of other stuff.......


or i could be way off.......
 
LOGANSTANFORTH said:
but you also got to look at the vertical centerline of your rear suspension too and how it will compress (think of where the center pin points).....a level truck has a centerline at 90 degrees and the suspension will relatively compress straight down when pulled down on and that will cause your traction bars to become a lift point where ever they are connected to the frame, raising the nose and transfering weight to the rear, and a taller suspension or hitch height will increase this exponentially (think 2wd blower truck with the nose 5 feet in the air going down the track)........now rotate that angle forward (rake) and now your actually trying to compress the suspension backwards......and when that happens your traction bars are now pulling down on the frame planting the front end......

but all of this can be affected also by weight, type of suspension, movement of the suspension, length or type of traction bars, driver, hitch type, color of the truck and alot of other stuff.......


or i could be way off.......
Click to expand...

i dont see that the rake of a truck will cause the suspension to compress rearward and in turn try to pull on the traction bars. i still think that the bars will be pushing on the frame and "lifting" the front.

Garrett
 
LOGANSTANFORTH said:
but you also got to look at the vertical centerline of your rear suspension too and how it will compress (think of where the center pin points).....a level truck has a centerline at 90 degrees and the suspension will relatively compress straight down when pulled down on and that will cause your traction bars to become a lift point where ever they are connected to the frame, raising the nose and transfering weight to the rear, and a taller suspension or hitch height will increase this exponentially (think 2wd blower truck with the nose 5 feet in the air going down the track)........now rotate that angle forward (rake) and now your actually trying to compress the suspension backwards......and when that happens your traction bars are now pulling down on the frame planting the front end......

but all of this can be affected also by weight, type of suspension, movement of the suspension, length or type of traction bars, driver, hitch type, color of the truck and alot of other stuff.......


or i could be way off.......
Click to expand...

How does suspension compression come into play if the rear is blocked and there is no suspension travel?
 
LOGANSTANFORTH said:
but you also got to look at the vertical centerline of your rear suspension too and how it will compress (think of where the center pin points).....a level truck has a centerline at 90 degrees and the suspension will relatively compress straight down when pulled down on and that will cause your traction bars to become a lift point where ever they are connected to the frame, raising the nose and transfering weight to the rear, and a taller suspension or hitch height will increase this exponentially (think 2wd blower truck with the nose 5 feet in the air going down the track)........now rotate that angle forward (rake) and now your actually trying to compress the suspension backwards......and when that happens your traction bars are now pulling down on the frame planting the front end......

but all of this can be affected also by weight, type of suspension, movement of the suspension, length or type of traction bars, driver, hitch type, color of the truck and alot of other stuff.......


or i could be way off.......
Click to expand...


Well, not to pick on ya, but you're doing what everyone else does....eyeballing everything and not actually figuring out what the actual loads are and where they're located.

Now with most everyone allowing rigid suspension even in the lower classes, a lot of stuff gets much more simplified.

In such a situation, the traction bars are only preventing axle motion and little more. The whole "lift point" thing is way overhyped. You need to be looking more at the drawbar and its relation to the rear axle and work it out from there.

But again if you don't know how to work it out with a FBD and statics, you're kinda farting in a windstorm. You need to know the sums of the the forces involved before you know in which direction they are acting.

And FWIW, changing the rake angle does not create the situation you're describing....the change of a few degrees in rake won't change how the bars act.

There is no 4WD pulling truck in existence that "plants the nose." Think about why that is.
 
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nwpadmax said:
Well, not to pick on ya, but you're doing what everyone else does....eyeballing everything and not actually figuring out what the actual loads are and where they're located.

Now with most everyone allowing rigid suspension even in the lower classes, a lot of stuff gets much more simplified.

In such a situation, the traction bars are only preventing axle motion and little more. The whole "lift point" thing is way overhyped. You need to be looking more at the drawbar and its relation to the rear axle and work it out from there.

But again if you don't know how to work it out with a FBD and statics, you're kinda farting in a windstorm. You need to know the sums of the the forces involved before you know in which direction they are acting.

And FWIW, changing the rake angle does not create the situation you're describing....the change of a few degrees in rake won't change how the bars act.

There is no 4WD pulling truck in existence that "plants the nose." Think about why that is.
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Mat, if you've done one (or several) of these FBD before, what kind and size of loads/forces are you figuring at the hook point?


I'd like to tryout a FBD just to see if I can make it make sense on paper.



C-ya
 
Im not a fan of big rake. Over my years of pulling iv built trucks with rake and with out, the ones with a rake i took it back out, they always hook better when they are close to level!

Iv got a buddy that built one with a big rake and he done it that way to get the hitch pivot point up so the hitch and the chain is on the same angle. (he didn't want to cut the bed floor out)
 
SmokeShow said:
Mat, if you've done one (or several) of these FBD before, what kind and size of loads/forces are you figuring at the hook point?
I'd like to tryout a FBD just to see if I can make it make sense on paper.
C-ya
Click to expand...


Well, just for the sake of learning something, if you didn't know what the forces were, what could you do to get an estimate of them?

That is where you start.

Okay class, who wants to answer this one?
 
brushpuller said:
Im not a fan of big rake. Over my years of pulling iv built trucks with rake and with out, the ones with a rake i took it back out, they always hook better when they are close to level!

Iv got a buddy that built one with a big rake and he done it that way to get the hitch pivot point up so the hitch and the chain is on the same angle. (he didn't want to cut the bed floor out)
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Moving the chassis around to accommodate the hitch is a big reason many guys do it. If you can fab your own custom reciever and the rules allow it, then your life is much easier.

Case in point: Wakeman's truck. It appears from the video that they put some extra rake into it for exactly that reason, to shove the hitch forward. I was not there so that's secondhand info, but it makes sense. It was a smart move by a smart puller that it would appear, caught his competitors sleeping. I don't believe that was the only factor in his success though. In pulling, it takes a complete package to win as convincingly as that. (one thing few mentioned is that he had great track speed at 300'). He had it won at the 100' mark.

IMO when you rake a truck trying to eek out every last bit of front weight effect (which a lot of guys say they do), if you do the geometry, the effects are almost trivial. On a long wheelbase truck, it's almost silly. You change the angle of the triangle by a couple degrees and the effective CG of the front weights changes by a half inch or something. Does anyone really believe moving your weights a half inch makes a chit bit of difference? I don't. Its like the weights sideways vs. weights straight out debate.

Reading the track, choosing an appropriate final drive ratio, tire selection and pressure all beat this rake business by a mile.
 
nwpadmax said:
Moving the chassis around to accommodate the hitch is a big reason many guys do it. If you can fab your own custom reciever and the rules allow it, then your life is much easier.

Case in point: Wakeman's truck. It appears from the video that they put some extra rake into it for exactly that reason, to shove the hitch forward. I was not there so that's secondhand info, but it makes sense. It was a smart move by a smart puller that it would appear, caught his competitors sleeping. I don't believe that was the only factor in his success though. In pulling, it takes a complete package to win as convincingly as that. (one thing few mentioned is that he had great track speed at 300'). He had it won at the 100' mark.

IMO when you rake a truck trying to eek out every last bit of front weight effect (which a lot of guys say they do), if you do the geometry, the effects are almost trivial. On a long wheelbase truck, it's almost silly. You change the angle of the triangle by a couple degrees and the effective CG of the front weights changes by a half inch or something. Does anyone really believe moving your weights a half inch makes a chit bit of difference? I don't. Its like the weights sideways vs. weights straight out debate.

Reading the track, choosing an appropriate final drive ratio, tire selection and pressure all beat this rake business by a mile.
Click to expand...



And that is why you can take an old truck with half the motor and compete with newer trucks that are without a doubt running better.
A 26" hitch height will give you a 33* angle to the sled, to some thats irrelevant info - but if you consider front end weight and height, and RECIEVER placement/height, your rear tires become the pivot point for a cantalever effect giving reson to keep in mind that 33* angle. So while rpm, final drive, tire pressure all play a role in your pull...the final factor is if the truck hooks hard because your hook point is working, then it changes all your other factors. So many factors go into chassis set up, thats why pulling is never a one man sport
 
nwpadmax said:
Moving the chassis around to accommodate the hitch is a big reason many guys do it. If you can fab your own custom reciever and the rules allow it, then your life is much easier.

Case in point: Wakeman's truck. It appears from the video that they put some extra rake into it for exactly that reason, to shove the hitch forward. I was not there so that's secondhand info, but it makes sense. It was a smart move by a smart puller that it would appear, caught his competitors sleeping. I don't believe that was the only factor in his success though. In pulling, it takes a complete package to win as convincingly as that. (one thing few mentioned is that he had great track speed at 300'). He had it won at the 100' mark.

IMO when you rake a truck trying to eek out every last bit of front weight effect (which a lot of guys say they do), if you do the geometry, the effects are almost trivial. On a long wheelbase truck, it's almost silly. You change the angle of the triangle by a couple degrees and the effective CG of the front weights changes by a half inch or something. Does anyone really believe moving your weights a half inch makes a chit bit of difference? I don't. Its like the weights sideways vs. weights straight out debate.

Reading the track, choosing an appropriate final drive ratio, tire selection and pressure all beat this rake business by a mile.
Click to expand...

I agree with all you've said except the part about the weight. Yes it makes a difference if the weight is moved 1/2 inch! A bunch of the 1/2" here and there makes a big difference as a whole....but i also pulled in a class that the top 5 or 6 trucks were within a foot to a foot and a half of each other evrey pull! Thats when the little things mean a lot!
 
If Ya'll recall, my truck was set up to run 1" of travel. It had about a 1"-2" rake without the front weights.

I only added weights on the left front. When it was hooked, the front would even out, the truck bent in the middle, my rear springs compressed 1" to the stops, and it looked about level going down the track, except for the 10" space of air between the cab and bed, lol..

If the truck is bowed in the middle, you are planting all the wheels.
 
brushpuller said:
I agree with all you've said except the part about the weight. Yes it makes a difference if the weight is moved 1/2 inch! A bunch of the 1/2" here and there makes a big difference as a whole....but i also pulled in a class that the top 5 or 6 trucks were within a foot to a foot and a half of each other evrey pull! Thats when the little things mean a lot!
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Well OK we might have to agree to disagree....but +/- 3 psi beats the 1/2" every time in terms of magnitude of change. So does gear selection. So does your line down the track, and how you launch it.

Try pulling 200 lbs. back sometime and see what happens. You might be surprised.

People who fuss over weight placement to that degree are being a bit neurotic/anal. Focus that level of attention on other things and I think you'll get more out of it.

The sport is not "nascar" enough IMO that 1/2" of weight movement means much. Especially with rigid suspension.

But if you have the time to get everything else perfect, and you wanna be nuts about your weights, well by all means have at it, there is nothing wrong with being all you can be. I was kinda throwing that in there so that novices don't get the wrong impression while reading this. You have to prioritize things in the setup.

I mean, think about it guys, how many of you have fretted over the truck for a week and then went to a pull and got a chitty draw and went out on a green track, and then watched every subsequent truck go further than you? Makes fussing with weights seem rather trivial, eh?

Or how many have been to a pull where the first guy gets a great track and then everything goes to chit because of the lack of track prep equipment (or proper use thereof).

My advice FWIW is to work on everything else first.
 
xtreme8504 said:
A 26" hitch height will give you a 33* angle to the sled, to some thats irrelevant info - but if you consider front end weight and height, and RECIEVER placement/height, your rear tires become the pivot point for a cantalever effect giving reson to keep in mind that 33* angle. So while rpm, final drive, tire pressure all play a role in your pull...the final factor is if the truck hooks hard because your hook point is working, then it changes all your other factors. So many factors go into chassis set up, thats why pulling is never a one man sport
Click to expand...

Only thing I disagree with is that the reciever height is meaningless. If it's all rigid, then your hook point is the only relevant thing, with respect to its location to the rear axle and tire as you mentioned.

You could make your hitch look like a pretzel or the Eiffel Tower. If the hook point is at 26", that's all that matters. If your frame flexes and you end up losing some hitch height, well, not much you can do about it without major work. But losing hitch height need not scare people to death....I have heard some stuff from experienced pullers that I respect that really surprised me. A lot of people follow a setup recipe that sometimes needs to be rethought based on what you're trying to accomplish. As in life, as you grow more experienced, things don't always follow hard-and-fast rules and there are shades of gray.

The "cantilever effect" you refer to is correct in spirit, but unless you put numbers and geometry to it, you're guessing at best.


Don't derail this into hitch design, that's a whole 'nuther war!!! LOL
 
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Sledpuller said:
If Ya'll recall, my truck was set up to run 1" of travel. It had about a 1"-2" rake without the front weights.

I only added weights on the left front. When it was hooked, the front would even out, the truck bent in the middle, my rear springs compressed 1" to the stops, and it looked about level going down the track, except for the 10" space of air between the cab and bed, lol..

If the truck is bowed in the middle, you are planting all the wheels.
Click to expand...


And lest we forget, you can set up and design and re-engineer the truck as much as you want....but the DRIVER has mucho to do with it!
 
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