Wheelbase and its effect on pulling

I agree Tom, I was allways told the bar should reach no less than the back of the cab so that they are tryin to pickup on the front half of the truck. mine go to the center of my drivers door and they work great.
 
Well one way to look at the shorter bars is they are pushing up on the frame and don't have the mechical advantage of longer bars do. I have long bars on mine, I have also heard about the shorter bars from drag racers say they help plant the rear end better!
 
Well one way to look at the shorter bars is they are pushing up on the frame and don't have the mechical advantage of longer bars do. I have long bars on mine, I have also heard about the shorter bars from drag racers say they help plant the rear end better!
 
Thats the point of the shorter bar they will force the axle down more and push the suspesion up , wether it b drag or pulling traction is traction you never see long bars in drag racing but one thing I did see is when usen one bar the force is more foward than up but when usen 2 (ladder bar) it will put more force on the chassis , I have no problem hooking up the dually so I dont care about the longer bar , for me it keeps my truck from flexing but some flex is good to a point
 
Frame flex= Bad. The more the frame flexes the more power you lose and the more angles you encounter for the drivetrain. There is a reason why tube chassis are built as stiff and strong as they are.

-Tom
 
Tcolesanti said:
Frame flex= Bad. The more the frame flexes the more power you lose and the more angles you encounter for the drivetrain. There is a reason why tube chassis are built as stiff and strong as they are.

-Tom

Frame flex is bad, to a point, BUT;
I have talked to the mod gasser pullers about this subject. They said that they completely boxed the frame on one of their pullers.
They said after they did this the truck didn't hook worth a crap.

They ended up cutting triangles of steel out of the frame, inverting the triangle every other cut.

They still maintained strength much higher than stock, but some flex was allowed and the truck hooked a lot better afterwards.
 
Garrett, I don't see how that works at all.

One more thing to think about, a short traction bar that runs to the open (non-boxed) portion of the frame will put tremendous amounts of stress on the frame during pulling. This can cause cracking or failure of the framerails. It happened to a member on here, can't remember his screen name.

-Tom
 
Tcolesanti said:
Garrett, I don't see how that works at all.

One more thing to think about, a short traction bar that runs to the open (non-boxed) portion of the frame will put tremendous amounts of stress on the frame during pulling. This can cause cracking or failure of the framerails. It happened to a member on here, can't remember his screen name.

-Tom

Don't know Tom, but the gasser guys have been at it a lot longer than us..

Run too short of a traction bar to a non-boxed portion of the frame, you are gonna have a bad time..:badidea:
http://www.competitiondiesel.com/forums/showthread.php?t=13189
 
Tcolesanti said:
That's the guy I was talking about, plus I heard about a guy at SDX this year that broke a frame on a reg cab/long bed?? Same issue I guess.

-Tom

I think you mean ORP/Indy, that was Kent Beason.
 
think about it this way, watch a top fuel rail. The first few feet the front wheels are just barely dancing on the ground but once they start to build up speed and downforce the chassis arches up or flexes to keep traction. I dont know how that relates to sled-pulling but I saw one flex ;)
 
I've always kinda chuckled when we all get to talking about suspension length and traction bar theory, because virtually no one agrees!

I initially went with the long-ass bars. Then a friend of mine made his truck into a puller and went with the short bars (both are CC/SB Chevies). Both hook equally well, I'd say. We run very similar setups, including tires. So in what amounts to as much as a direct comparison as I can come up with, I'd say the length doesn't appear to be a significant factor.

A year ago I would have argued hard for the long bar, now, what can I say?

I think one of the reasons it might not matter so much is that when you think about it, the purpose of the trac bar is to resist the twisting of the axle housing - that is, you're resisting the torque that the wheels apply to the ground. The body frame and all that absorb that torque (in engineering terms, a moment load) one way or the other. Elsewise, the truck would pull a wheelie and flip over.

Point is, whether you do it with a lot of force on a short lever arm, or less force on a longer one, it's still the same moment load. That's just physics.

What makes the difference? I think it's particular to your truck and how the suspension works together. What works on a Chevy with X chassis length and Y rear spring rate and Z front spring rate may not mean sheet on a Dodge with SFA and totally different spring rates, heavier engine out front, etc.

My best advice, when you buy a truck for pulling, look at what other people with the same exact configuration as you have, and judge for yourself based on their results.

One other thing I'll toss in for you that's directly pertinent to the question you first asked: many clubs over this way are adopting the 27% hitch length rule. If they do that, I think it matters less. The long trucks get essentially penalized by having to run a longer hitch than the RCLB versions. When I did the math, it actually appeared to me that the 27% rule may slightly favor the RCLB trucks, but it ain't by a whole lot. The 60" from center line of the front axle made the hanging weight a more significant lever, as a percent of the total truck length.

So anyway, just keep that in mind when formulating your plans.
 
the reason I want to find out is because I want to know if there is a limit. I know that is not an easy to answer to get or they may be no real answer. I just know that at some point the physics of the thing has to be overcome. So, why build a 1000hp combo and then have it hop down the track like a mad man when I could build an 800hp combo and have it pull the sled out the door.
 
Learn how to drive plain and simple. I have seen EX-Cab long beds bounce like a hooker on a Friday night. due to the fact the drivers sucked and i have seen EX- cab short beds stick to the ground and make the long beds look bad. Basically it comes down to the driver.
 
HOOKED said:
Learn how to drive plain and simple. I have seen EX-Cab long beds bounce like a hooker on a Friday night. due to the fact the drivers sucked and i have seen EX- cab short beds stick to the ground and make the long beds look bad. Basically it comes down to the driver.

That sounds sorta familiar...
 
GSM-01 said:
That sounds sorta familiar...
That is what I was thinking. I saw a truck puke the rear end at platte city this year.

Knock on wood, I have an extended cab long bed, and GSM has probably seen me leave the line, and I have NEVER had a bouncing issue with the truck. I leave the line with 25+ psi, at around 2500. I personally think the manuals have a lot more work to do launching the truck smoother than an auto does.
 
zstroken said:
That is what I was thinking. I saw a truck puke the rear end at platte city this year.

Knock on wood, I have an extended cab long bed, and GSM has probably seen me leave the line, and I have NEVER had a bouncing issue with the truck. I leave the line with 25+ psi, at around 2500. I personally think the manuals have a lot more work to do launching the truck smoother than an auto does.


i totally agree EVERYONE dosent matter what you run will bounce every now and then. Feeling the truck and knowing when to get out of the clutch is an art plain and simple. And then you have your newbees who floor board and side step the clutch who knows what these guys are thinking.
 
Zstroken if you where refering to my run at Platte City have you know that was my third pull on a very agressive p-pump.
 
I might have been. Probably more given you a hard time than any. My take is that the long wheel base trucks are more forgiving to variables than the short wheelbase trucks. I ahve seen many a short wheel base truck bounce. Many more than the long wheelbase. Maybe that is back to the guys who know what they are doing like to run a long wheelbase for that reason. Probably the worst is the short wheelbase stick trucks, not to say that it won't work.
Once again I have probably around 50 hooks on my truck and have never had a bounce issue. From hard clay tracks, to crap powder, to mud, no issues.
I personally don't think it is my skill that keeps it from bouncing either.
 
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