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9/09/2015 12:38 am  #1

Custom Mustang II/Corvair IRS

Hi everyone, I am new here and am trying to learn as much as possible about IRS geometry and set up. I am building a custom rear using a Mustang II 8" rear for the center section and a 65' Corvair outer with the drum brakes removed. I will be using 87'-88' Thunderbird turbo coupe rear brakes in the inboard position. The brakes are a perfect fit for the Mustang II rear end, they have a 4x4.25 lug pattern as do the Ford 8.8 driveshaft yoke flanges I am using. I Will need to enlarge the holes from 7/16" to 1/2" and open the center holeup to fit the axle stub. The Corvair half shafts use a 1310 u-joint the same as the flange yokes.

The Corvair uses a single LCA on each side directly below the half shaft and has a trailing arm that mounts at about the same height as the LCA. I am looking to make a tighter set up by using harder bushings and possibly two LCA's on each side along with radius rod inline with the inner pivot of the LCA. I have seen some use of a watts link at the top of the upright and might incoporate it into my system. My biggest concern is to get the geometry correct with good tire wear and handling. Any help is appreciated. Thanks Jim.


"Thinking outside the box in a traditional sort of way" Jim Ford

7/11/2016 11:41 pm  #2

Re: Custom Mustang II/Corvair IRS

From what you posted...  You are using the Corvair trailing arms sans drums?
Center section - Doesn't the mid 80s-90s Thunderbird/cougar have IRS?
But you want inboard discs correct?


7/12/2016 3:48 am  #3

Re: Custom Mustang II/Corvair IRS

The design has changed a bit. I am making bearing retainers that will accept A10 bearings and seals minus the secondary lock ring. These bearings are a caged tapered roller bearing and should work well with the axle side load always pushing inboard.

The axles will be shortened and have the bearing surface moved outboard to make the center section as narrow as possible. The Turbo-Coupe rotors were too small and I couldn't fit the calipers in without hitting the differential housing, so I am using Volvo 850 rotors turned around backwards. To center all this up I am having the axle brake drum centering ring removed and boring a step into the end. I will have a stepped piece made that fits the axle counter bore, rotor center, and driveshaft yoke inner flange.

I decided to not use the Corvair trailing arms but instead use the Jag style of lower control arms and carriers. I am using the Corvair half shafts, bearing housings, and outer stub axles. I had parts waterjet and I welded them together to create the outer carrier and bolted the Corvair bearing retainers to it.

I am using 4 bar end links and tubes for the lower control arm. I will be welding a plate top and bottom to create a boxed lower control arm. I will have a strut rod from the outer front of this control arm angled forward to be inline with the inner pivot point to control any fore and aft movement without binding.

To answer the above question. 90's T-bird/Cougar had an independent rear but I wanted to make my own  and had this design in my head for the past 25 years. I also had some of the parts for that long as well. The whole thing is going to be open in the rear so you can see all the parts so it has to look good as well.

"Thinking outside the box in a traditional sort of way" Jim Ford
     Thread Starter

7/22/2016 9:28 am  #4

Re: Custom Mustang II/Corvair IRS

Sounds like you've thought it thru (probably more than once).

Are you going to use the lower arm for all the caster/camber/toe adjustments or are you also putting in adjustment in the upper?
Your original ? was regarding geometry for wear and handling.  I've done analysis of suspension loads and geometry before and I can help with that.  An initial run at it only takes a readable sketch with dimensions.
I'm a retired mechanical engineer so any thing new for my brain to do is welcome.

Last edited by MentalKase (7/22/2016 9:29 am)


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