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Old 02-04-2005, 11:22 AM
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How to determine front sway bar diameter?

I am considering installing a sway bar on my Must II front suspension. I'm already convinced it will improve the handling and stability of my all steel 37 Plymouth sedan. I need to understand how to determine what diameter bar I should get. Is 3/4" too little, or is 1-1/8" too much? Does the rear suspension have much influence on what goes up front? Like the spring ratr post below, it seems to me there must be some mathmatical evaluation that is more reliable than, "That's what everybody uses."

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Old 02-04-2005, 12:33 PM
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sway bars

Stock sway bar size is a starting point. If you go thicker you will get less sway but a rougher ride. Thinner more sway but smoother ride. It's up to you.
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Old 02-05-2005, 12:21 AM
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what I would need to know is roll centre front and rear..CGheight..the weight of the car..what are the design parameters for acceptable body roll at a given speed..??

wheel weights are needed..front rear weight distribution..Then put all of this in the calculator and come up with an EWAG for the torsional moment of the proposed sway bar..From which we can figure out an approximate diameter to make the bars..

Then it is off to the track with the wheel scales to gather some lap times and drive impressions..do we have a push? is it loose?? then what..??

Got a headaches yet? Seeing your dollars evaporate? this is what we do to get a race car to be competitive..

Now in the case of a street rod..weigh the car and then look at the sizes of bars used on comparable cars...You may find that one from a mustang with a V_8 will work "good enough for you"and help with the body roll and handling..

My thoughts on sway bars..

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Old 02-05-2005, 12:31 AM
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Do you have the optional strut rods on the lower A-frames? Have you considered using adjustable coil over shocks to fine tune your front end. Also look up the MII front end in the knowledge base. There has been a few lengthy and informative discussions on that front end on a variety of cars. Good Luck.
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Old 02-05-2005, 03:28 AM
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adding to "one more time", you also need to know your spring rates and spring (compression) travel per lb of force to determine the bars (resistance) size and link length.

there's no correct size, it's a question of how you want the car to behave/feel with hard cornering at speed. good news is you can tune it by mixing and matching rubber and urathane bushings .

pain in the butt is, a 1/4" does make a big difference depending on the front end weight and spring rates.
ex: 1/2" bar in a SBF old Mustang= does nothing, 3/4"=my choice, 1"= to harsh?, every little bump is a "bang" while driving straight
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Old 02-07-2005, 06:37 AM
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Street Rodder has a how to article in their current issue about this...
http://www.streetrodderweb.com/toc/sr_toc/
The install is a on a solid axle car but it may provide you with some insight...
Mark
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Old 03-01-2005, 10:40 AM
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Thanks fellas. I'm not interested in racing the car. I just want it to handle reasonably on the highway, not sway all over the road on mildly breezy days and reduce body roll when turning on city streets. In other words, I'm just trying to make it handle better for increased safety and comfort. The best advice in my opinion is to find a vehicle with similar physical characteristics and similar rear axel weight to base a selection for my case. I don't have the resources necessary to do an exhaustive analysis and testing process. I will start with a few assumptions and some input from some of the after market suspension manufacturers and compare that info with any info I can gather from the library before I decide. In any case, I know a rear sway bar will improve the handling. Thanks for your input.
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Old 03-01-2005, 10:56 AM
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Go with a stock bar and I'm sure you will be happy with it.
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