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I just completed my spring project, which started out to replace the rear leaf springs, which were 20 + years old. Then I started researching, and in the end installed a Fays2 Watts Link, TCP Torque Arm, and Flex Form composite leaf springs. I also replaced my wheels and tires, and upgraded the exhaust to 3" from the headers through the mufflers, reduced to 2.5" to clear the watts link (while welding around the exhaust, I figured now was the time). What an amazing difference. The car is unbelievably stable in corners now, and doesn't rub tires anywhere, though they barely clear everywhere, with 275/40/17 on 9.5" wheels in the rear, and 225/50/16 on 8" wheels in the front (Toyo Proxes R888 autocross tires). I redid the front suspension a couple years back, and really didn't notice a huge difference, but this time, it is night and day. With the watts link, the rear axle just doesn't move laterally entering and exiting corners. The torque arm virtually eliminated brake dive and nose lift. The combination just makes the car so stable no matter what you're doing. I already had Global West sub frames on the car, so fabricated a custom removable brace to tie the torque arm to the sub frames. The watts link had absolutely no negatives - other than cost. The low roll center created by the watts link also virtually eliminated body roll. I like the composite leaf springs, but they are somewhat stiffer riding, though smoother, if that makes sense. Cost wasn't much more than the better steel leaf springs, though it took a while to get them. The torque arm contributed a little further to a bouncy ride, but the difference in vertical stability (and extra traction) is well worth it to me. It no longer drives like a 60's muscle car. Below is a picture.
PICT0037.jpg
 

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This looks great, gotta post most pictures of this for sure. Been looking at a bunch of different options to go with replacing my rear suspension.
 

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I really dig the watts link. I ran a panhard when I installed my composite leaves due to having a diff cover on the 8.8.
 

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I debated the panhard versus watts link for quite a while before deciding. My research finally led me to that both would make the exhaust routing difficult, but the watts link was the slightly superior solution (albeit more expensive). I was shocked on the exhaust after installing the watts link - my 2.5" Flowmaster tailpipes that had been on the car for years welded right in place without any modifications at all. I still can't get over the change in the cars handling behavior. I exceeded my goal of getting in the neighborhood of the handling capability of my highly modified suspensions on my 89 Mustang and 04 Cobra - it's at least on par, and it's going to take my driving time to decide which is better for which circumstances.
 

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reldla1996 instead of me taking my own front suspension thread off track I figured I'd kick this one up instead. I'm curious if the front and rear spring rates and ride is reasonably consistent between the front and rear of your car. My stock '68 the ride in back was boingy and bouncy (typical stock leaf spring ride, quickly bounces up and down), while the front was soft and floaty and long duration response to road undulations. . .quite a significant difference in ride behavior between each end. I'm hoping to gain more consistency with my upgrades. I'll be happy with a stiffer ride, I'm expecting that, so long as it's not a harsh ride.

How much did the torque arm help, do you feel it would be a beneficial upgrade for a 300 hp 302 with 5 speed? I'm hoping to avoid that upgrade since it seems every vehicle I've put traction bars or Caltracs on have always had maddening problems. I've never done a torque arm (well my 1938 has one built in, but the ol' straight 8 ain't a powerhouse) but that may be the way to go. I know if I switch from auto to T5 manual it will torque the rear axle more.

I might shoot you a PM. . .
 

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Discussion Starter #6
I was told the composite springs had a rate of about 250 lbs, which is roughly double factory GT springs. The composite springs react much faster than leaf springs, which also removes some of the bounce, and they are completely silent. My front springs are "600" springs, that I'm not sure they are an honest 600 lbs spring. They feel more like 500 or so to me. Of course, with the big block, that will soften the ride in front. The roller perches definitely made the front springs smoother as well. The car seems pretty balanced to me, front and rear spring wise. Shocks are standard KYB's, which I was thinking of swapping out for Bilsteins. The only rubber bushings left in the car are the front lower control arms and the rear spring shackles. All other bushings are poly, except the front upper control arms, which are delalum. The strut rods are global west, and so are a spherical bearing. I'm not a fan of traction bars either. The main reason I went with the torque arm was to greatly reduce nose lift on acceleration, and brake dive. The car still has a little, but nothing like it was before - I like it a lot. Between the watts link and the torque arm, the car is so much more stable than before when braking or accelerating or going through corners. Any benefit in traction was a free gift. What I enjoy most in driving cars is taking them through some fun corners, nad my goal was to improve handling. You also tend to get in less trouble that way, versus speed.... I had a rear sway bar on the car for many years (which helped a lot before), but it came off with the watts link, and honestly it's staying off now - it doesn't need it.
 

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275/40/17 on 9.5" wheels in the rear. With the watts link, the rear axle just doesn't move laterally entering and exiting corners. The torque arm virtually eliminated brake dive and nose lift. The combination just makes the car so stable no matter what you're doing. I already had Global West sub frames on the car, so fabricated a custom removable brace to tie the torque arm to the sub frames. The watts link had absolutely no negatives - other than cost. The low roll center created by the watts link also virtually eliminated body roll.
View attachment 95642
reldla1996, I am in the process of putting the global west subframe connectors on, front suspension will be all new, mostly stock with the exception of the shelby drop, stiffer springs, larger sway bar, etc... I haven't really like any of the mounting options for the rear sway bars out there though and am probably going to go the Watts Link route. I still am running stock leaf springs for the time (with poly and delrin bushings) but will likely change them out as well when installing the Watts Link. What backspacing of wheel are you running in the rear with the 275's?
 

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Discussion Starter #10
Richness - the wheels are ARE 17x9.5 with 5.56" back spacing, but then with 0.5" spacers to make it come out just right. The tires are toyo R888, which are wide for their size. I'd highly recommend the brace bar sold by NPD, part 5026-2c, as it really reinforces the lower control arm mounting points to the frame, and just bolts in place of the factory small tubular arm that ties to the frame under the oil pan.
 

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Richness - the wheels are ARE 17x9.5 with 5.56" back spacing, but then with 0.5" spacers to make it come out just right. The tires are toyo R888, which are wide for their size. I'd highly recommend the brace bar sold by NPD, part 5026-2c, as it really reinforces the lower control arm mounting points to the frame, and just bolts in place of the factory small tubular arm that ties to the frame under the oil pan.
I like the looks of that: https://www.npdlink.com/store/products/mustang_crossmember_front_street_bandit-143988-365.html Price seems a little high for what it is though. I'm a bit confused as to where it mounts, just looking at that picture. Looks to be an improvement over this bracing idea: https://secure.cougarpartscatalog.com/store/p/13273-Reinforcement-Plates-Front-Crossmember-PAIR-New-1967-1970-Mercury-Cougar-/-1967-1970-Ford-Mustang.html?attribs=75

I have already welded these in too: https://secure.cougarpartscatalog.com/towerbrace.html?attribs=75
 

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I was told the composite springs had a rate of about 250 lbs, which is roughly double factory GT springs. The composite springs react much faster than leaf springs, which also removes some of the bounce, and they are completely silent. My front springs are "600" springs, that I'm not sure they are an honest 600 lbs spring. They feel more like 500 or so to me. Of course, with the big block, that will soften the ride in front. The roller perches definitely made the front springs smoother as well. The car seems pretty balanced to me, front and rear spring wise. Shocks are standard KYB's, which I was thinking of swapping out for Bilsteins. The only rubber bushings left in the car are the front lower control arms and the rear spring shackles. All other bushings are poly, except the front upper control arms, which are delalum. The strut rods are global west, and so are a spherical bearing. I'm not a fan of traction bars either. The main reason I went with the torque arm was to greatly reduce nose lift on acceleration, and brake dive. The car still has a little, but nothing like it was before - I like it a lot. Between the watts link and the torque arm, the car is so much more stable than before when braking or accelerating or going through corners. Any benefit in traction was a free gift. What I enjoy most in driving cars is taking them through some fun corners, nad my goal was to improve handling. You also tend to get in less trouble that way, versus speed.... I had a rear sway bar on the car for many years (which helped a lot before), but it came off with the watts link, and honestly it's staying off now - it doesn't need it.
Ron I hadn't thought about the brake dive and keeping the car more level with the torque arm, that makes sense. I'm glad to hear the car feels balanced with your suspension/spring setup. you have given some really terrific feedback!!

I like the looks of that: https://www.npdlink.com/store/products/mustang_crossmember_front_street_bandit-143988-365.html Price seems a little high for what it is though. I'm a bit confused as to where it mounts, just looking at that picture. Looks to be an improvement over this bracing idea: https://secure.cougarpartscatalog.com/store/p/13273-Reinforcement-Plates-Front-Crossmember-PAIR-New-1967-1970-Mercury-Cougar-/-1967-1970-Ford-Mustang.html?attribs=75
Richness, here is the same thing from WCCC already welded for around $100, it's probably nearly as stout as the one from NPD for half the cost and probably sufficient if you're not into serious track use https://secure.cougarpartscatalog.com/xcross.html That's probably the one I'll go with.
 

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Discussion Starter #13
Richness - first I was mistaken on the backspacing, I used a 6.35" backspacing, with 0.5" spacers. On the brace, the one from NPD also ties into the camber mounting bolts, really helping reinforce the lower control arm mounting points. It amkes alignments more difficult, but is a huge improvement over the factory cross member, and the one from West Coast Cougar. It simply bolts in, to where the factory cross member bolts plus where the camber bolts are. I like your shock tower braces, if I had seen them when the car was apart, I would have done those too!
 

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That's where I was guessing that they mounted to, just wish they had a couple of more photos on NPD with different angles. I've added this to my list of items to get after this upcoming driving season, along with the watts link you've posted. I think for now I'll just weld up a couple little patches onto the factory cross member like I posted above. Here's a picture of the shock tower brace that I've installed. Not only will this help with the shock tower stress, it will also keep dirt/road crap/grease out of that little trough-like area below the upper control arm mounting points.

IMG_1140.jpg

Do you have any pictures of your car with that rear-wheel/tire setup? Curious to see how it sits in the wheel-well.
 

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Here are pictures of the rear wheel and tire from two angles. If I tuck the tire anymore inboard, it rubs on the front inner wheel well. Where it's at, I don't notice it rubbing anywhere. Boy, the car sure needs cleaned up....
PICT0195.jpg PICT0196.jpg
 

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Here are pictures of the rear wheel and tire from two angles. If I tuck the tire anymore inboard, it rubs on the front inner wheel well. Where it's at, I don't notice it rubbing anywhere. Boy, the car sure needs cleaned up....
View attachment 99889 View attachment 99897
Looks good to me. I like the way that the 275 fits on the 9.5" wheel. I am planning on cutting/ rolling my fender lips with the Eastwood rolling tool, maybe I can squeeze a 295 back there, with a little less backspacing. What are you running for rear brakes?
 

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Discussion Starter #18
I'm running the original 9" rear axle with factory drum brakes; it's a 390 GT car. As you can see, I lowered the rear an inch or so with the springs.
 

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Before spending megabucks on a suspension replacement, get some real shock absorbers. Koni shocks will fix all the issues that you are mentioning. There are other brands that are well regarded, but I only have experience with Koni. Compared to cheapie shocks like KYB, Monroe, or Gabriel etc the difference is breathtaking.



reldla1996 instead of me taking my own front suspension thread off track I figured I'd kick this one up instead. I'm curious if the front and rear spring rates and ride is reasonably consistent between the front and rear of your car. My stock '68 the ride in back was boingy and bouncy (typical stock leaf spring ride, quickly bounces up and down), while the front was soft and floaty and long duration response to road undulations. . .quite a significant difference in ride behavior between each end. I'm hoping to gain more consistency with my upgrades. I'll be happy with a stiffer ride, I'm expecting that, so long as it's not a harsh ride.

How much did the torque arm help, do you feel it would be a beneficial upgrade for a 300 hp 302 with 5 speed? I'm hoping to avoid that upgrade since it seems every vehicle I've put traction bars or Caltracs on have always had maddening problems. I've never done a torque arm (well my 1938 has one built in, but the ol' straight 8 ain't a powerhouse) but that may be the way to go. I know if I switch from auto to T5 manual it will torque the rear axle more.

I might shoot you a PM. . .
 

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That's good to hear Royce, wouldn't have thought the difference would be that significant. I do plan to do the watts link and mono rear leaf, regardless of the shock choice I feel those upgrades would be worthwhile. I'm on the fence about the torque arm though, I'll see how it does with the mentioned upgrades then decide later whether or not to spring for the torque arm.

By the way since I posted last I just bought a solid '68 project car to get started on soon. 99% rust free and much of the bodywork done, and it's pretty much disassembled. With only 90,900 miles on the 4V 302 car the front shock towers are in great shape with no cracks or holes drilled for grease zerk access. I'm still installing the shock tower reinforcement plates, the stronger crossmember and monte carlo bar. I'm also adding the sheetmetal divider that goes behind the back seat that WCCC sells.
 
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