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Pre-70 Performance suspension

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343sharpstick View Drop Down
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    Posted: Dec/21/2016 at 12:40pm
Just thought I would start a thread specifically discussing the Pre-1970 Trunion front suspension in a high performance application.
I've had my 1969 Javelin on the Road from 2009, and I've had a great time with it.
When I built the car, I basically did all the stuff to my front suspension that was done to the 68 TA Race car.
Does it work, sure does! I would recommend what I've done to anyone interested in putting together a trunion front suspension car.

Looking at some improvements for the future, but you would not be disappointed with this, Listing this here to assist anyone interested in setting up you car, and also keep everyone aware of the limitations.

What I have up front now:
- Boxed lower arms,
- Higher rate and shorter springs
- Larger front anti-sway bar
- All Polyurethane bushings
- Strut rod replaced with rod end
- 17 inch wheels with 200 treadwear tires 215/45-17 up front.
- Edelbrock shocks (No longer available)




Edited by 343sharpstick - Dec/21/2016 at 1:13pm
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343sharpstick View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Dec/21/2016 at 12:51pm
I do not have lowering plates, as I didn't want to add the un-sprung weight. I've done a few autocross events, and my first impression is that the front of the car needs more grip, (OK, to be honest, my first impression was that I need to be a better driver!) obviously when running a trunion front suspension you are limited in front tire size.

Be aware that you are not only limited from a backspacing standpoint, you are also limited on the overall diameter and width to the outside, based on the amount of caster you dial in.

In the experiment below I put a larger tire on the front to test fitment. This is a 245/50-17. Notice that the front edge will contact the corner of the front fender. This is installed using a spacer to clear the trunion. On the inside the tire was about 1/8 gap between the tire and the trunion. this is with about 3 degrees of caster.

With a Radial tire, you want as much caster as possible with an older pro-touring type of car. Most cars set up for performance driving will have at least 5 degrees of caster. This is not possible with trunion front suspension, based on the limitation of the trunion itself. It was designed for 1 to 2 degrees of caster used with bias ply tires.
For comparison, a 2005-2010 mustang specifies 7.1 degrees of caster.

And BTW, if you are building a car, a little metal work up here to add some clearance would probably be a good idea. Had I known this before I had everything painted ...




Edited by 343sharpstick - Dec/21/2016 at 1:19pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iapexl8r Quote  Post ReplyReply Direct Link To This Post Posted: Dec/21/2016 at 6:46pm
sweet! thanks for the info. luckily I am in process of doing body work and will be "adjusting the front fenders for 15x8 rims with 245/60/15 tires and I have already massaged the rear quarters to fit a 275/60/15 on a 9" rim with 3 3/4" back space
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Dec/21/2016 at 8:57pm
Cool, off topic completely, but it's my thread anyway :) AMC 20 rear axle, or other?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iapexl8r Quote  Post ReplyReply Direct Link To This Post Posted: Dec/25/2016 at 11:00am
 to answer your question I have an amc 20 rear end with solid axles, the one the car came with.


          I have been thinking about the suspension not being able to get the required caster for performance driving. I am guessing the limiting factor is the lack of articulation of the Trunnion . Has any one ever tried to either make the upper control arm mounts or the control arm itself adjustable? My thinking is if you could either raise the forward mount or "angle" (or twist on a horizontal plane) the upper control  arm forward end up  to effectively put the trunnion at more of an angle to allow the lower control arm outer spindle mount to be  moved forward without putting to much strain on the trunnion.  Just a thought

                                                                 Chris
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Post Options Post Options   Thanks (0) Thanks(0)   Quote iapexl8r Quote  Post ReplyReply Direct Link To This Post Posted: Dec/25/2016 at 11:02am
Also what front brakes are you running?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rogue401 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/26/2016 at 5:20pm
I think I remember reading that the Ron Kaplan cars had factory modified inner fenders that mounted the upper control arms at an angle to increase the caster and have some anti-dive built in. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Dec/26/2016 at 5:41pm
Originally posted by Rogue401 Rogue401 wrote:

I think I remember reading that the Ron Kaplan cars had factory modified inner fenders that mounted the upper control arms at an angle to increase the caster and have some anti-dive built in. 



IIRC, Donohue mentioned that the 69 Javelin that was given to assist with the setup the 70 T/A car... he was surprised by the lack of suspension travel at the front, and how well it put up a good fight. Maybe trunions work best by going against what he sets up 70 on up suspensions in track form. His requirement is 3 inches play from bump stop to full travel. With today's tires and requirements to keep the tracking and rigidity at lateral Gs 2 inches is max with a wee give in the bump stops.
71 Javelin SST body
390 69 crank, 70 block & heads
NASCAR SB2 rods & pistons
78 Jeep TH400 w/ 2.76 Low
50/50 Ford-AMC Suspension
79 F150 rear & 8.8 axles
Ford Racing 3.25 gears & 9" /w Detroit locker
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Dec/27/2016 at 12:22pm
I have the 'Aerospace brakes' kit. When I got that the Wilwood kit was not yet available. I do like the Aerospace kit, just not many upgrade options available last I checked. I did replace the pads with the more aggressive track pads and that made a significant improvement.
 
I've heard lots of rumors on what was done to the 68/69 T/A cars. all I can comment on is what I've tried.
One idea I had was to add a spherical bearing to the horizontal mount point of the trunion.
I went over many options, including replacing the vertical ball bearing with a tapered roller bearing, but all that is not as elegant as the simple upper ball joint solution.
 
In tearing down my front suspension I just found another problem caused by trying to add too much caster Wacko


Edited by 343sharpstick - Dec/27/2016 at 12:25pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 343sharpstick Quote  Post ReplyReply Direct Link To This Post Posted: Dec/27/2016 at 2:25pm
Here is the passenger side lower control arm. Looks like pushing the control arm toward the front of the car exerted extra pressure on the bushing at the connection point to the chassis. Over time it looks like it broke the lip of the bushing as it was pushing forward. Booo!
 
OK,


Edited by 343sharpstick - Dec/27/2016 at 2:29pm
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