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  #11  
Old 10-13-2020, 07:06 PM
ScotI ScotI is offline
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Originally Posted by SSLance View Post
Because I decided to go under the tie rods with my swing arms, lowering the bar itself from the frame with the tube stands helped with the geometry of the end links. This along with the additional structural help is why we went this direction.
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Originally Posted by David Pozzi View Post
Stay away from aluminum arms. A circle track magazine tested them and they have too much flex.
Thanks for that info Lance & mentioning that Mr. Pozzi. I've been looking @ the 1.25" x.750" steel arms. Didn't think the aluminum arms would be a 'good idea' street thing. My mock-up pieces using 1.25" tall 'arms' (yardstick sections) fit comfortably under the R&P's TRE's @ ride height.

I did speak w/a rep from Speedway Eng. yesterday & got the requested info on machined dimensions of the bars as well as some insight. For those curious... It seems their e-mail form of contact doesn't work so calling is best.

Is there a 'Blue Collar' calculation that can be done for the rate of the bar to help narrow a starting point on a modular set-up? My research yielded the info that Ridetech's C10 Strong-Arm 'MuscleBar' set-up utilizes a 1.5" OD x .250" wall tubular bar w/a listed rate of 1020#. I'm using that info as a comparison with the other bars I have (utilizing the Speedway bar-size to arm-length spread sheet for the rates):

Fixed Rate
OE GM standard bar 1.125" solid w/14" arms @ 264#
OE GM HD 1.25" solid w/14" arms @ 350#
Addco/PB 1.25" solid w/15" arms @ 330#
Bell Tech 1.375" solid w/14" arms @ 494#
RideTech/Musclebar 1.5" tubular @ 1020#


Adjustable Rate
Speedway Eng. 1.5" hollow w/14" arms @ 549#
Speedway Eng. 1.5" hollow w/8" arms @ 957#
Speedway Eng. 1.375" solid w/8" arms @ 864#
Speedway Eng. 1.25" solid w/8" arms @ 617#


The RideTech bar rate seems suspect based on the fact that all the other bars (which are OE or direct OE configuration replacements) have a measured arm length of approx. 14". Using the Speedway spread sheet for their hollow bar @ 14" arm length indicates the 549# and that's w/a .500" wall vs. RideTechs .250" wall. My 8" arm length is based off of relocating the sway bar closer to the a-arms which provides the additional ground clearance.

I feel comfortable w/my Speedway bar selections but wanted others insight before pulling the trigger.

Last edited by ScotI; 10-13-2020 at 07:20 PM.
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  #12  
Old 10-13-2020, 10:11 PM
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Beechy Beechy is online now
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ScotI.......some more info is required to compare rates.

Ridetech quotes 1020 but their arm length might be 6".....entirely possible.
We need to know that arm length in order to compare.

Using this calculator......

https://swayaway.com/tech-room/torsi...te-calculator/

you can compare a 6" arm length to 12" arm for the same bar. Simple multiplication.....the short bar is double the rate of the long for the same diameter and same pillow block spacing.

Also if you shorten your BAR LENGTH (and locating pillow blocks closer) to get inside your chassis rails , you're gonna raise the rate massive. Warning....if your bar length is short relative to the amount of BEND in the arms to get out to your 39.3" then the amount of deflection in the ARMS reduces the bar rate and eventually fracture an arm at the pillow block area. Shortening the straight section of bar increases prolly by the square of change.....shorten 1" = 100# change.....shorten 2" = 400# change.

A HOLLOW BAR is only slightly lower in rate compared to a solid bar ..... how much? I don't know but maybe 5 or 10%. Gotta be on Internet somewhere.

My suggestion in this whole subject would be to calculate the wheel rate of a STOCK truck compared to your MODIFIED wheel rate then use the same percentage of factory bar to your desired bar. Don't OVERPOWER your spring/shock combo.
(ignoring sway bar....so just use the dimensions from inner lower pickup point to spring /shock mount, and inner point to tire contact dimension multiplied into spring rate)
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Last edited by Beechy; 10-13-2020 at 10:24 PM.
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  #13  
Old 10-13-2020, 11:29 PM
ScotI ScotI is offline
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Quote:
Originally Posted by Beechy View Post
ScotI.......some more info is required to compare rates.

Ridetech quotes 1020 but their arm length might be 6".....entirely possible.
We need to know that arm length in order to compare.

Using this calculator......

https://swayaway.com/tech-room/torsi...te-calculator/

you can compare a 6" arm length to 12" arm for the same bar. Simple multiplication.....the short bar is double the rate of the long for the same diameter and same pillow block spacing.

Also if you shorten your BAR LENGTH (and locating pillow blocks closer) to get inside your chassis rails , you're gonna raise the rate massive. Warning....if your bar length is short relative to the amount of BEND in the arms to get out to your 39.3" then the amount of deflection in the ARMS reduces the bar rate and eventually fracture an arm at the pillow block area. Shortening the straight section of bar increases prolly by the square of change.....shorten 1" = 100# change.....shorten 2" = 400# change.

A HOLLOW BAR is only slightly lower in rate compared to a solid bar ..... how much? I don't know but maybe 5 or 10%. Gotta be on Internet somewhere.

My suggestion in this whole subject would be to calculate the wheel rate of a STOCK truck compared to your MODIFIED wheel rate then use the same percentage of factory bar to your desired bar. Don't OVERPOWER your spring/shock combo.
(ignoring sway bar....so just use the dimensions from inner lower pickup point to spring /shock mount, and inner point to tire contact dimension multiplied into spring rate)
Thanks for the feedback & insight.
I have the pivot point to shock/Lower BJ dimensions in my notebook @ work. I used those numbers when determining a starting spring rate for the C/O's & how I arrived @ the 750# springs. I'll follow up on that tomorrow.

All numbers posted were basing the arm length off of the current 1pc bars on hand. The Addco/PB is the only one that really has multiple bends; the others are pretty much just a 'U' bend ( I_____I ). I had to look @ an earlier version of the RideTech MuscleBar (under my dually) to verify it was similar in shape. The bar the listed 1020# spec was for could in fact be different in it's arm length since it is a more recent version (the bar under my dually is from 2014). These should all share an arm length that's fairly close since the C/L of the bars pivot point to end-link are the same.

As noted in my info, all of these C10 bars were wider than the modular set-up I'm considering which is part of the reason I'm searching for a replacement. The closest being the BellTech bar which is @ least 1" wider @ the base/arm).

With the 'standard' width (length) modular bar @ 37.5" plus the heim 'high-angle inserts', I should/would be @ the C/L of the upper link. I figure their straight arms will be used as-is after cutting to req'd length (they're 18"L) & holes drilled.

Last edited by ScotI; 10-13-2020 at 11:35 PM.
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  #14  
Old 10-28-2020, 04:54 PM
ScotI ScotI is offline
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Just to follow-up.... I purchased a 1.25" x 37.5"L x 48-spline bar w/the 1.25"x 18"x .750" 48-spline arms, 1.25" collars, & end-caps.
Plan is to trim the arms to a 10" length & drill 3 holes to allow for some tuning (@ 7", 8", & 9" from the bars center-line).

I appreciate the feedback that was given.
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