chevelle splined sway bar rates

[The WidowMaker]

im looking for some rates to compliment my setup.

front 550 springs, ats spindles, spc uppers, alston shocks
rear 150 alston coilovers straight up, parallel 4 link, watts set at 12"

any info would be greatly appreciated. i need to pull the trigger on a rear bar this week.



thanks, Tim

[68protouring454]

it all depends where you will mount the bar and how long your arms end up being.

[The WidowMaker]

thanks for the reply. im not actually looking for the size of bar or length of arms. i just need the approximate rate and then i can tailor the arms to meet that rate with my bar widths. the arms will have multiple adjustment holes to dial it in, but i need somewhere to start.

right now im thinking about 500 for the front and about 300 for the rear. mark thought that the RRCH was a little low and would require too much rate with my 150 springs. therefore ill probably move it up an inch or two.

thanks again,
Tim

[68protouring454]

yes, i would go for 450-600 front and 250-350 for the rear

[The WidowMaker]

sounds good, ill start there.

anyone know what the stock ones were? 1.25" front and 1" rear.

they are a solid bar with "x" length arms, but those figures come out pretty high. different steel?

thanks, Tim

[Blown353]

Stock bar diameter depended on suspension package... most stock sway bars for 68-72 Chevelles were 3/4" to 1" in front and 7/8" was the only rear bar offered.

Keep in mind the way the rear bar is mounted by the factory really reduces the effectiveness.

[The WidowMaker]

yeah, the stock configuration for the rear is pretty bad. this will be a true frame mounted bar though, so it should be a huge improvement.

right now ive got a 1.25" front and 1" rear bar. could i just take the width of these along with the arm lengths and figure out the rate, or is the steel a major factor with the splined bars? i really dont need to do this, but im just interested to see what i had before.


i havent had any issues finding a rear bar around 300, but the front is a little more tough. since it needs to be 39" long and has 14" arms, even the solid bars are around 400, not 500. looks like ill need a bigger bar thats turned down to 1.25 at the ends. most of those are only 37.5 though, so it looks like i may have to pay some more for a custom length.

Tim

[Blown353]

You can get a pretty good approximation of the effective rate of the factory bars using the diameter and arm length.

A 1.25" front bar is overkill if you're running springs of a more "modern" spring rate and will probably lead to poor turn-in and understeer.

With 550# front springs I'd probably start with around a 1.125" bar and go from there, my guess is that turn in will be best with a 1" to 1.125" front bar with those 550# front springs, but it depends on tire & driving preference too.

I'm running a 15/16" front bar with my 750# springs. Started with my old 1.25" front bar and the turn in was slow and had lots of understeer, 1.125" was better, and 15/16" was the best.

I do want one of Mark's adjustable A-body frame-link rear bars when they come out so I can fine-tune things...

[Tom.A]

Troy, Is your 15/16 front bar OEM or ?

Thanks,

[MarkM66]

yeah, the stock configuration for the rear is pretty bad. this will be a true frame mounted bar though, so it should be a huge improvement.

right now ive got a 1.25" front and 1" rear bar. could i just take the width of these along with the arm lengths and figure out the rate, or is the steel a major factor with the splined bars? i really dont need to do this, but im just interested to see what i had before.


i havent had any issues finding a rear bar around 300, but the front is a little more tough. since it needs to be 39" long and has 14" arms, even the solid bars are around 400, not 500. looks like ill need a bigger bar thats turned down to 1.25 at the ends. most of those are only 37.5 though, so it looks like i may have to pay some more for a custom length.

Tim

How wide is your frame in the front? Mine's 35.5", so a 2" longer bar @ 37.5" will work. I want the arms as close as possible to the frame, as they do get in the way of the tire at full lock.

The locating collars don't need to be on the outside of the frame, unless your pillow blocks are all the way to the outside. Mine are in the stock location, so my collars go inside the frame.

[Blown353]

Troy, Is your 15/16 front bar OEM or ?

Thanks,

Yep. I raided a friend's giant pile of old factory bars and grabbed a 1", 15/16", and 7/8". My old 1.25" bar was off the front of a 2nd gen T/A and my 1-1/8" bar came with my Global West arms years ago.

[The WidowMaker]

mark, any pics of your setup? my frame is right around 36" and speedway says to add 3" so i came up with 39". now if it was just 3" from the end of the pillow block, things would be slightly different.

I want the arms as close as possible to the frame, as they do get in the way of the tire at full lock.

im with you on this, but i wasnt sure how far below the frame the pillow blocks put the bar. if there is a gap i would assume that the bar ends could move freely. but i really dont want the arms hitting the frame at any point, even on jackstands. if it is necessary for tire clearance, i guess i could make a spacer....... anyone have any first hand knowledge????

The locating collars don't need to be on the outside of the frame, unless your pillow blocks are all the way to the outside. Mine are in the stock location, so my collars go inside the frame.
im really new to the idea of splined bars, so i assume the collars keep the bar from moving laterally. but you also talked about pillow blocks on the outside. is there any way to put the arms inside the blocks. i really need to do this for the rear bar, but i didnt think the pillow blocks would work on the splined portion.

thanks, Tim

[MarkM66]

mark, any pics of your setup? my frame is right around 36" and speedway says to add 3" so i came up with 39". now if it was just 3" from the end of the pillow block, things would be slightly different.



im with you on this, but i wasnt sure how far below the frame the pillow blocks put the bar. if there is a gap i would assume that the bar ends could move freely. but i really dont want the arms hitting the frame at any point, even on jackstands. if it is necessary for tire clearance, i guess i could make a spacer....... anyone have any first hand knowledge????


im really new to the idea of splined bars, so i assume the collars keep the bar from moving laterally. but you also talked about pillow blocks on the outside. is there any way to put the arms inside the blocks. i really need to do this for the rear bar, but i didnt think the pillow blocks would work on the splined portion.

thanks, Tim

I don't have any pics as of now. I got sidetracked on another part of the car. Yeah, this gets hard to explain. I'm new to it too..

I actually ordered the wrong size bar, to short, so I was able to moch up where my pillow blocks and collars will go. 3" longer then the frame is to long IMO. You just need to ad the width of the arms, and whatever you want for clearance between the arm and the frame. Off hand, I believe the arms are about 1/2" thick.

I mounted my pillow blocks near the factory location, to the inside of the frame, which leaves room for the collars to fit under the frame. The pillow blocks mount the bar below the frame enough so the collars dont hit the frame, but they're close, and yes, to prevent lateral movement.

Hope that makes some sense.

[The WidowMaker]

yep, that makes sense, or so i think. if im understanding, you moved the pillow blocks slightly inboard, put a collar to the outside of those but still under the frame, and then put the arms on the outside of the frame, but just barely?

at first i thought you were placing the arms under the frame and i didnt see how that would fit. but if youre leaving about 1/4 - 1/2 on each outboard side for clearance and then putting on the arm, i dont see why i would need 3" for a 39" total either.

im going to give speedway a call and see if they can tell me some more "can" and "cannot" dos.

but until then, anybody know if i can put the pillow blocks on the furthest outboard side of the bar? id run a pillow, collar, arm, arm, collar, pillow and call it good????? the pillows would be on the splined portion, but i dont know if that would matter all that much.

thanks, Tim

[MarkM66]

yep, that makes sense, or so i think. if im understanding, you moved the pillow blocks slightly inboard, put a collar to the outside of those but still under the frame, and then put the arms on the outside of the frame, but just barely?

at first i thought you were placing the arms under the frame and i didnt see how that would fit. but if youre leaving about 1/4 - 1/2 on each outboard side for clearance and then putting on the arm, i dont see why i would need 3" for a 39" total either.

im going to give speedway a call and see if they can tell me some more "can" and "cannot" dos.

but until then, anybody know if i can put the pillow blocks on the furthest outboard side of the bar? id run a pillow, collar, arm, arm, collar, pillow and call it good????? the pillows would be on the splined portion, but i dont know if that would matter all that much.

thanks, Tim


That's right.

My blocks are not on the splined part of the bar.

[The WidowMaker]

playing around with performance trends, it says ill have moderate oversteer with the 500 front and 300 rear. i can either go down on the rear or up on the front with bars, or drop the roll center a bunch more. i really dont want to much bar rate in the front since it will be a driver and there will be pot holes, driveways and the such, but i really dont want to hurt the handling by putting something too small on. the good news is that bars are only $130, so although it sucks, it aint "that" bad to do some testing.

Tim

[The WidowMaker]

just an update..... i installed the rear bar. i got an 1.25" bar thats turned down to 1.00" in the middle. i found out some interesting stuff along the way though.

first is that the 37.5" bar is actually 37.75".

second, the arms can ONLY be mounted in one place. there are two bolts that hold the arms on the bar, and the splines are cut down in only one area to allow the bolts to slide through. i thought that i would be able to position them slightly, but this position leaves about 3/16" to the outside of each arm.

third, with the arm, pillow block and collar all squeezed together as much as possible, the collar is resting on the area that steps down to the 1" portion. i think it will work, but im going to drill a slight hole for the set screw so theres no chance of it moving. im not sure though why there wouldnt be enough room and since the front bar steps up, i dont know how its going to work.

lastly, i dont believe a 37.5" bar will fit on the front. btwn the 3/16" per side, plus the arms, plus clearance to the frame, i think its going to be too tight. maybe a 38, but i think a 38.5 safely.

ill post pics of the rear bar in a few weeks.

Tim