Digressive Pull Bar

[Mr.Kennedy777]

I was thinking about this idea, someone on here introduced me to it on Advanced Racings website. It was a spring on a pre loader, and had another spring on it. It was for a fifth coil. The idea was to set the pre load to allow it to act on a stiffer rate then when the pre load was over come, it reduced its rate. My question is, would it almost be better to do that with a pre loaded rubber stack, so that it would act like the spring you wanted it to, but once the pre load was over come it just cushioned that rate a bit, and made it softer at the upper limit. Realistically how much of a jump do you need in rate? It would probably be lighter to use the urethane versus a spring, and it wouldn’t really mess with the rate too bad depending on what the load rate curve for that rubber is and you’d want to check all that before putting it together... I know personally my torque numbers don’t drop off that drastically and sometimes all you really need is that little bit of extra cushion later on. That’s kinda like, fitting the pull bar to match the torque curve and the tires ability to stay hooked up too. I dunno, just a thought. I have not seen it yet but the idea of it seems pretty good to me. What are your guys’ thoughts?

[sidewinder69]

Just curious about what about a pullbar bar makes more traction than a lift arm setup??

[Mr.Kennedy777]

Just curious about what about a pullbar bar makes more traction than a lift arm setup??

It dont think it does. I’m pretty sure pull bars have more wrap up than a lift arm, but the leverage of a lift arm/fifth coil just can’t be beat, as well as how it puts that force down onto the tires. I was just thinking that perhaps pre loaded rubber would lighten the design of the digressive fifth coil spring stack instead of the spring on the pre loader. With a fifth coil, you could just put a bump stop pre loader underneath the spring and pre load a stack of bumps. It could sit between the bottom of the spring cup and bottom of the shock at heim end, and it’s be a way lighter design. Could function very similar using a soft stack of bumps pre loaded correctly. Probably would need a load rater to check the change in rate of the bumps after you set the pre load, ideally have it increase a little more linear than more progressive. You could do basically the same thing as with the spring, the difference would be fairly subtle and like I said, the design would be much lighter.

[DEKconsulting]

Is what u r talkin about close to the neuline deal

[Mr.Kennedy777]

Is what u r talkin about close to the neuline deal

If you were to take the nueline rubber and pre load the stack to 1/2 or 3/4 of the force going into be fed into the fifth coil and put that above the bottom heim end on the shock, yet underneath the spring in it’s cup, it would work just the spring initially until the pre load in the rubber was overcome, and then it would cushion that rate some. You would set initial rate same as always with a spring you want to have as your rate, and then you could change final rate by: adjusting the pre load in the biscuits as well as the durometer reading of the biscuits. Adjusting pre load would not only change the final rate but also when it transfered from stiffer initial to softer secondary. You’d want to check the load curve for the biscuits in the range of that pre load to make sure they were getting Too stiff, I’m assuming you would want a larger stack of soft bump rubbers to keep the change in rate sort of linear. (It would digress in rate as a stack then gain progressively as the bumps stiffen up, although it would be very very slightly if you were in the right load curve for the rubber at your desired pre load)

[CageFaraday]

Just curious about what about a pullbar bar makes more traction than a lift arm setup??

I'll take a pull bar over 5th arm every time. Never seen anything dig as hard as a Swing arm car with a long pull bar. This is why modified's on those skinny tires run pull instead of 5th. Think about it...

[MasterSbilt_Racer]

I'll take a pull bar over 5th arm every time. Never seen anything dig as hard as a Swing arm car with a long pull bar. This is why modified's on those skinny tires run pull instead of 5th. Think about it...

I think those mod guys are behind the times, as normal. If we were drag racing, I would take a pullbar. Its about corner speed. What that pullbar gives, it takes away when you slow down.

[Punisher88]

Who needs forward traction when you don't have to slow down.. right MB?

[JustAddDirt]

A lot depend on length of the pull bar, and what you are using to absorb the energy.
Spring bars release energy at twice the rate as a biscuit style. springs are quite violent on decal, which is why entry can be compromised when on a spring pull bar.