Awesome 3-Link; for Ford!

[Red67Mustang]

I decided to start a thread for my latest modification... which was to install the www.StreetorTrack.com (http://www.StreetorTrack.com) three link rear suspension into my '67 Mustang. I also upgraded to their 11.65" rear disc brakes at the same time.

This is what came in the box(es):
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This is a pic of the Watts Link bracket installed. The instructions say you can bolt this in, but I went ahead and welded it since it never needs to come back out. I must say, it fit the 40-ish year old frame rails perfectly. Despite effort to produce quality instructions, there are a number of minor things that leave room for confusion, I ended up being on the phone with Shaun from StreetorTrack a number of times, but always got the info I needed in short order - even nights/weekends. The guy's a car nut of the first order - great to deal with!
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A couple of pics from one of my many mock-ups just making sure everything is working and where it is supposed to be. It's starting to look like something!
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There are three options for where to mount the lower control arms, I chose (for now at least) the factory front spring pockets, so I ended up moving the control arm to the top hole (so it's horizontal at ride height) instead of the middle hole as I had it during this mock-up.
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I had to add some washers under the Watts Link heim joints where they attached to the axle, in order to space them backwards and eliminate some angularity in the Watts Link that I had encountered. I contacted Shaun (Owner of StreetorTrack) and he promptly sent me more washers than I even needed - the Customer Service is like nothing else!
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I stayed with my original 8" rear end because a) it already has Currie internals, b) it's less unsprung weight than a 9" and c) I'm making less than 400 hp at the rear wheels so I'm within acceptable power levels for the 8" rear. However, I did decide to add a drain plug while I had it all blown apart...
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I did this work in late December / early January and just had the opportunity to really flog it at an Autocross school this past Saturday (3/15/14). I'll post the results of that next.

[srh3trinity]

I have looked at their floater setups. Cool to see another three link option.

[Red67Mustang]

I had the opportunity to attend an SCCA Autocross school last Saturday (3/15/14) and really abuse the car! Overall the car performed great, the only problem was when it lost power steering due to a fauly control valve (time for a steering upgrade).

As far as handling, the 3-Link really planted the rear end. There was no tendancy to oversteer but it was very controllable to steer with the trhottle. A few times I got the car into a very controllable 4 wheel drift and it just felt awesome! Way more balanced than I epxted it to be for a maiden voyage. I can't wait to upgrade the front suspension now to rival the rear. In the meanwhile, time to improve the loose nut behind the wheel!
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I was pitching the car around so much I noticed later that I had been puking fuel out of the vent from the fuel cell... (I have -6 AN vent line run to where the factory gas cap would have mounted, and modified a cap to conceal the vent).
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[6fastback7]

Hard to find any complaints on Shaun or his products...I have his front Coil-over setup and the results are very dramatic over stock setups. I am on thinking about doing the rear this summer...my only concerns are not being able to route the exhaust to the rear ( i already smell exhaust and burn a little oil). But a balanced car on Bilstein shocks might be worth a little exhaust poisoning!

p.s could you drop the rear any lower? or would you be hitting the axle on the trunk floor? Mine sits lower then yours on leafs and I dont want to lose the stance...nor do i want to cut into the trunk floor for clearance.

[Red67Mustang]

I am able to lower the rear, but with my stock geometry front end (shelby drop, 620 lb springs) it would be lower in the rear than the front. I actually have the ride height set about an inch higher than where Shaun designed the system, for the above reason - just to keep it level.

Once I upgrade to the coil over front (and likely get new wheels to better tuck up into the wheelhouse) then I'll drop the ride height down to where its supposed to be. I had no issues with the trunk floor at full compression during mock-up.

[andrewb70]

Nice write up. Can you show picture of how the upper link mounts to the chassis?

Andrew

[wendell]

Are the links really only 20ish" long? What does it do that your leafs didn't? How much more does it weight?

[Street or Track]

Thank you for the great write up Clint! Nice pictures too. I knew you'd love the ride quality, improved grip and lateral stability.

To answer a couple of questions from the thread, here is a pretty descriptive picture from another car of the 3-Link installed:

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You can clearly see the 3rd Link Frame and the 3rd Link. The 'ducks bill' shaped front section gets bolted through the 2 layers of sheet metal that make up the floor and start of the trunk. In the interior another 'ducks bill' shaped strip of material gets stitch welded to this area and is ultimately under the rear seat base. This provides a solid connection and has been subjected to many 600ft-lb cars! Positioning the 3rd Link this way gives us a longer link than the S197 3-Link. The 3rd Link Frame starts out as a CNC machined piece that looks almost too nice to hide in the tunnel:

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You can also see this car uses the longer, lower trailing arm option. This improves the Side View Swing Arm Angle (SVSA) from the 58" when mounted in the leaf spring pockets (like the OP uses) to 84". If you know your suspension geometry basics you'll know that in a clean sheet design anything over 60" is good. The leaf spring mount almost makes this number without having to weld anything to the car.

Also shown is our Full Floating 9" System with parking brake but the system can be installed on conventional 8", 8.8", 9" housings.

[Red67Mustang]

What does it do that your leafs didn't?

In short, a 3 link with Watts link does a lot more than leaf springs, such as...

-Locate the axle laterally without deflection under load.
-Eliminate axle wrap up and associated wheel hop.
-Eliminate suspension bind when the axle articulates, allowing the shocks to do their job.
-Allow the pinion angle to be precisely set
-Fix you rear roll center on the watts bell crank bolt
-With coil overs, allows precise ride height adjustment.

[Street or Track]

In short, a 3 link with Watts link does a lot more than leaf springs, such as...

-Locate the axle laterally without deflection under load.
-Eliminate axle wrap up and associated wheel hop.
-Eliminate suspension bind when the axle articulates, allowing the shocks to do their job.
-Allow the pinion angle to be precisely set
-Fix you rear roll center on the watts bell crank bolt
-With coil overs, allows precise ride height adjustment.

...and with coilovers on the front allows you to corner weight the car...

[wendell]

...and with coilovers on the front allows you to corner weight the car...
That I like.
How low can you get the rRC?

[Street or Track]

That I like.
How low can you get the rRC?

Good question. The rear roll center is determined by ride height and where you place the Watts Link center bolt pivot. Both are adjustable so the roll center # will vary. The Watts Link center pivot bolt has positive adjustment positions and 3" of vertical adjustment in 1/2" increments:

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Just for instance, if you used the lowest hole on the 70 I built for my wife you'd be at 8":

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Stock fenders, 285/35/18 rear tires on a 18x10 rim:

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[Jeff70]

Any updates?

[Mateospeed]

Great to see some quality, well-designed products for Fords being produced! Looks like a good job, folks. :)