Pull bar vs lift bar & upper vs lower slung

[twisterf5]

we are building a new chassis for next year have always built our own.our current chassis is to heavy and has to much left side %. so is the upper slung the way to go to save weight. right now we are under slung but can't get below 2450. and was looking at using a pull bar that would save allot of weight if you could still get good bite with it. right now we give up allot in dry slick do to left side.and what are the pro and cons of going molly this time. thanks for any input.

[DLM06]

Good questions. I have often wondered why pull bars are common on 4 bar modifieds but not LM's. The only answer I get is that "LM's don't need the traction because of the wide tires". We all know that's certainly not the case.

[twisterf5]

i know there are times that i needed more forward bite. to me it is just allot of more weight to carry. my new chassis will be pull bar.need to make up for this 6.4 280 lb frame i carry around.think it will allow the top of the pull bare to be moved side to side. well going to give it a shot.

[zeroracing]

Well I will bite.

My torque arm really adds minimal weight when compaired to pull bar. Pull bars require additional bracing around the pickup point and brackets on the rear end. A modified can bend a normal one so with a four bar car you may need to use a heavy steel tube.

Now, typically a pull bar reacts too quickly for late models. A Rayburn on swing arm does not have the 4 bar bite initially, they can run them, mods have small tires... You can try a long pull bar, which is slower reacting than a short but still faster than a torque arm. You will have issues getting a smooth car with a pull bar, many mods are going to a torque arm for this reason,

If your worried about weight then over slung is way to go. A correct design for either can make weight, most your weight comes from bolt ons.

On the Moly note, guessing you mean chromoly, if you have not welded and worked with it before then skip it, it is deadly if incorrectly welded. Will fail and injury or kill driver. use DOM to be safe and strong,

I don't want to sound like a jerk but if your unfamiliar with building materials, structural design and suspension design then buy a used car, you will waste time and money to end up with junk. A good car is engineered, and every aspect is looked at, for safety reliability, speed... I have seen guys that meant well, and spent time on cars, but they were inconsistent and wasted years running at the back only to give up. Late model chassis are cutting edge, give it a ton of thought before sinking hundreds of hours and thousands of dollars into a car. Spend it towards a newer used car, and the time to learning the car inside and out.

[twisterf5]

not my first build have about 300 wins all in our own chassis. all our owm chassis were molly. but if you never try things you are just settling. a light weight pull bar is half the weight of a lift set up.one would think a lift bar would be more inconsistent with more moving parts. may just be the next big thing if not can always put a lift bar back on. but you will never know if you don't try.

[Egoracing]

not my first build have about 300 wins all in our own chassis. all our owm chassis were molly. but if you never try things you are just settling. a light weight pull bar is half the weight of a lift set up.one would think a lift bar would be more inconsistent with more moving parts. may just be the next big thing if not can always put a lift bar back on. but you will never know if you don't try.

That is it, every few years it is tried and goes away again. With a 4 link and the travel that you get on a typical rear suspension you are going to find that the pull bar will easily bind up the suspension and limit movement once you get the bar and shock(s) in place. This was also a problem on a lift bar on some cars that braced them to the right side frame rail to close to the rearend.
Remember if you try it, the typical .083 tubing for the chassis of a late model will not hold the pressure you are more than likely having to with .095 wall and brace it at the mounting point. To brace it properly to take the pressure that a typical late model is probably going to require a secondary bar in the chassis to the mounting point. The problem is the pressure that the late model engines and tires are going to put in the bar. You are also going to be replacing springs every few weeks. The problem lies in, if it does not work and you go to a lift bar then you area back where you are with a chassis that was built for one suspension and changed to another and it will weigh more than a specific built chassis. As for the over or under slung, If you race at a track where contact is typical, overslung may not be the best way to go. When the 2 chassis are put side by side on a scale the weight difference is minimal as you have to design an overslung differently to take the forces and that adds weight and the smaller tubing being used on the under bars. I would bet depending on MFG you are looking at less than 100 lbs total and you end up with a chassis that is less rigid.

[twisterf5]

That is it, every few years it is tried and goes away again. With a 4 link and the travel that you get on a typical rear suspension you are going to find that the pull bar will easily bind up the suspension and limit movement once you get the bar and shock(s) in place. This was also a problem on a lift bar on some cars that braced them to the right side frame rail to close to the rearend. good point but 4 bar owm move the same and they use them. with the pull bars out now don;t think it will bind. we will see. i will put it in the cad on the computer and see if it binds

[charcoal01]

We don't have any problems with binding on the mod and our travel and articulation isn't much different at all than a dlm. The number one thing you need to do is put a heavier walled bar in that runs next to your shoulder where you will mount the pullbar bracket to. Next run a brace to the front a pillar bar and another one to the hoop down bar, won't break that way. Only other real problem is getting creative with the rear of the driver tub so the pullbar doesn't hit the tin. Good luck.

[fastford]

i have to agree with EGO on this one i will say we had some sucess several years ago with a pull bar and the lft rear shock and spring on a clamp but driver must be very smooth as well as track and it is almost and i say almost impossible to keep from binding i think with todays set ups the pull bar is thing of the past. i would like to add as a fabricator myself , and you may already know this , but the biggest problem with moly is the weld , i use a mig welder and mild steel wire which creats a less brittle weld that will flex enough to keep from breaking

[Kwhardage]

We ran a pull bar this year in an older Shaw car. Stop and go track that is normally very smooth. This setup worked very well on this track, and we had plenty of travel without binding. We did pull the mounts out of the car three times though. After the first time, it was braced, but pulled the tubing all the way out the next time. Last time was put together for last race and taken easy. Much more power and traction than when this car was originally designed. If you've never seen it happen, it tears up a lot of pieces when that breaks and your hooked up. Keep all that in mind when thinking about going this way and building your mounts. Brace it anyway it makes since structurally, gusset your corners, and check ALL of the welds weekly.

[dirty white boy]

not my first build have about 300 wins all in our own chassis. all our owm chassis were molly. but if you never try things you are just settling. a light weight pull bar is half the weight of a lift set up.one would think a lift bar would be more inconsistent with more moving parts. may just be the next big thing if not can always put a lift bar back on. but you will never know if you don't try.


id go with the lift arm an over rail,...if your who i think you are,.. more consistantsy is what you need along with a better dry slick set up!...an keep the left front down! hope to see that f5 towards da front in '13!

[MLR19]

The new Rayburn design fixes the pull bar binding issues, we have raced one of these cars this season, & have been very happy with it.. Won a $2000 to win show at the end of the season against some good 4 bar cars in the black slick. I think This new design has a lot of potential.

MLR19

[F22 RAPTOR]

we are building a new chassis for next year have always built our own.our current chassis is to heavy and has to much left side %. so is the upper slung the way to go to save weight. right now we are under slung but can't get below 2450. and was looking at using a pull bar that would save allot of weight if you could still get good bite with it. right now we give up allot in dry slick do to left side.and what are the pro and cons of going molly this time. thanks for any input.

First, I think Under Slung rails are safer, stronger and if you construct the car right not much difference in weight.
Second, Under Slung shouldn't have any effect on Left side %, but Rear %.
Third, I don't recommend Chromoly, see pics below for demonstration of failure in professionally built chromoly chassis.
Fourth, its been my experience that a pull-bar does produce more forward traction combined with the right setup and suspension system.

Lastly, I'd love to see pics of your frame.
area541@comcast.net