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Author Topic:   rubber bushed pull bar
THUNDERSTRUCK
Member
posted March 06, 2000 06:50 PM
I run a afco rubber bushing pull bar.
I am iterested in a spring loaded bar,
my question is how do I determine what
rate of spring is a good starting point?
The car is a IMCA modified, and weighs
close to 2500# any help or suggestions?


modman
Administrator
posted March 06, 2000 07:00 PM
I think the primary starting point for these is 600 lbs. You need an indicator of some type to keep track of how much the spring compresses. Use that indicator to tell you whether or not you need more or less. If it bottoms, you need more. Get as much travel with a lighter spring as you can without it bottoming. Just a reminder, you need less spring on a dryslick track to be more forgiving to the tires, so they don't break loose. Hope this helps.



kb42
Member
posted March 06, 2000 08:25 PM
It seems that I was having a little bit of trouble finding what was best for mine too. The 600 worked decent for my car in the feature but in the heats a 800 worked better. The one I found to work for me overall was the progressive spring from dirtworks. It is rated at 400 to 1000 pounds and costs the same as the other springs. My car weighs around 2200 to 2300. Just my opinion what works for me. I've heard of guys running 900 to 1000 pound springs all the time. So I guess its what works for you.


THUNDERSTRUCK
Member
posted March 07, 2000 03:38 PM
Can you tell me if the spring is preloaded
or does it fit loose?
thanks.


kb42
Member
posted March 07, 2000 07:47 PM
I have been told by many people including Rex Merrit that you just snug it up so it is not loose and so there is no preload. I believe AFCO recommends this too. If not someone can correct me.


jammin
Administrator
posted March 07, 2000 07:50 PM
Any time you change your preload, it changes the actual weight of the spring. I would do as you have said and just snug it up.


3x Racing
Member
posted April 06, 2000 12:45 AM
we had run a spring loaded bar for 3 years and FINALLY tried the rubber biscut bar. 5 laps later the spring bar was in the garbage. The rubber is MUCH smoother and doesn't bind up like the springs. just my $.02.


Charles Ostergaard
Member
posted April 07, 2000 03:36 PM
I ran a 800 spring and left it loose. I mean it rattled a little. It was good all the time. I have a 2000 car and they say pull rod with rubber bisquits.


jammin
Administrator
posted April 17, 2000 12:22 PM
The spring is much better guys, its tunable. If you run a rubber, its not tunable. It is more forgiving maybe than the other, but this means that your spring rate is too heavy on the pull bar. If you lighten the spring rate, you have essentially done the same thing.


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