Hey guys! This is my first post here, but I've been reading up on this site for quite some time now and was hoping you guys could answer a couple questions for me. I own a 1970 Skylark (which is my daily driver) that I got about 6 months ago. I finally decided to go ahead and upgrade the suspension, however, I have only purchased rear suspension components. Everything on the car is stock currently (suspension-wise) and the rear doesn't have a sway bar. I purchased a UMI rear suspension kit with tubular lower/upper control arms (non-adjustable), a 1 inch sway bar, and bracing from upper to the lower control arm. The kit uses poly bushings and I also purchased poly bushings for the differential housing just before reading how they cause a lot of binding when used there. ou: First off, how much of a difference will these upgrades cause in handling? Will it be a large difference? Also, could I get away with using the poly bushings in the differential housing or should I return the poly and get rubber? Currently I don't have plans to upgrade the front suspension (in terms of replacing control arms) however I do plan on changing all front bushings to poly bushings and adding a larger UMI front sway bar relatively soon. Will the handling be weird at all with only the rear having proper control arms? Down the line I probably will upgrade the front control arms, but I was just wondering if the car could still have handling potential without replacing the front control arms.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle Welcome! Nice looking car, its similar to mine in appearance (so I like your style!). You will read alot of varying opinions on the poly bushings. I have experience with 2 72 skylarks having all poly bushings (energy suspension) and I have experienced no issues. I do personally feel they make for a stiffer ride, and the one thing I would go back and do differently would be to use rubber body mounts instead of poly, but as far as the suspension goes, as long as you don't mind a slightly harsher ride (harsh maybe isn't the best word to use in all fairness. "Stiff/sensitive") I don't think you'll have any noticeable performance issues. As far as upgrading the rear, any upgrades will be noticeable! The rear bar will probably net the biggest improvement. I would also recommend you consider putting on a larger diameter front roll bar. One of the 72's I mentioned had almost exactly what you describe. It had tubular upper/lower rear arms, rear 1" roll bar, all poly bushings, stock front a arms, and it did had a 1.25" diameter front roll bar. It was noticeably stiffer, but man did it handle very nice! My current 72 is going to be nearly identical, only the rear uppers I have (yet to install them) are adjustable to tweak pinion angle. I currently have all stock suspension, poly bushings all around, and a 1.25" front bar, and that alone made a huge difference in body roll. Long story short, personally, I think your plan is fine, with one caveat being I would add a larger than stock front bar.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle I will suggest the other opinion. The engineers that designed the 4 link in the rear suspension system factored in the compliance of rubber bushings. They depended on this compliance to make sure the suspension would not bind during movement of the suspension under cornering loads. When GM put together the famous 1LE road racing package for the Camaro poly bushings were available. They did not use them. They used a higher durometer rubber bushing. If you look at most of the suspension component companies now you will see that they are all starting to offer spherical bushings on their best products. In general it is widely recognized by suspension professionals that poly bushings are not the best way to go with the GM 4 link. That being said there are many satisfied customers like Shawn who have no problem with the poly bushings. They do help get rid of wheel hop at the drag strip and surely feel better than a rear end with old worn out bushings. At the cornering speeds that we use on the street and given the crap geometry of a stock front end it would be hard to reach the point where suspension bind would happen or cause a problem. Personally I still would not use them but get some 1LE rubber bushings and put them in the UMI control arms. Better yet would be to get spherical bushings at the frame. Many of the aftermarket companies are making street spherical bushings now. Shawn, would like to hear a little more about the poly body bushings. I have to do the body bushings next year and am debating what to use. I thought the poly would be a good compromise between rubber and steel.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle To expand on what Doug said, I should add a bit of a disclaimer: much like almost any other modifications/upgrades I think it depends on your intended purpose for the car. If you're autocrossing/road course racing/that kind of thing, I could see the potential binding perhaps being an issue. My car is more street/strip oriented, and therefore the added strength is beneficial without being detrimental to my cars useage. Again, on the 2 cars I have experience, I have no complaints. Also, be careful on internet conjecture. I've had multiple comment on the poly bushings being bad, only to say they never had experience with them, just that they read something on the internet. We all know how that is.... Doug, my comment about the body bushings was a more personal preference thing concerning "bumps in the road" (quite literally). Again, for my purposes, I don't think the poly body mounts make any noticeable difference in performance, however I do think they attribute considerably to the aforementioned "harsher" ride. I think for me, a decent trade off would've been poly suspension bushings but rubber body mounts to dampen the jolts a bit. The thing to consider is my preference for cruising comfort vs. handling performance though, as it very well may vary from yours. It's only a theory on my part though. I'm not complaining about the ride quality my car has, its still soft by comparison to many (obviously this leads to the topic of shocks/springs/tire sizes/etc). But I think it'd be my "happy medium". I know, again, for my intended use and desired " cruising v. Performance" preferences, solid body mounts were never even a consideration. I do think the poly's would be a nice compromise between rubber and solid however. I'll put it this way, the poly body mounts don't bother me enough to consider swapping them out, and swapping body mounts isn't all that difficult!
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle Thank you so much guys! I was getting worried that I made the wrong decision but everything will hopefully be fine. The parts come in this Friday and I'm too excited! I definitely agree with you in terms of the front sway bar Shawn. Either today or tomorrow I will probably end up ordering the UMI 1.25 front bar. My plan before getting this car was to build a car I could take to track days and auto-x, but I decided to go with classic muscle instead. Unfortunately these cars don't handle anywhere near what I would need for track so this will only be a street/strip car, with a lot of spirited driving on the streets seeing as it's my daily. I would however, like to get the handling as close as I can to what a track car would get (without spending the big bucks which is why I will probably end up with stock front control arms). I guess my only option now is to install the rear with everything I purchased, then worst case if the ride quality isn't desirable I could switch out to rubber bushings. Thanks again! I appreciate all the input.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle From my experience of road racing fox body mustangs with the same style 4-link, I would go poly on all but the 2 upper bushings on the differential. There should be enough compliance in those to prevent bind unless you're already sliding or using R-compound track tires. Once you hit the track regularly, you'll either want to do the front right away to keep a bit more balance steering and braking or you'll wear out the front very fast and have to change it all anyways.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle That's exactly what I had read. One of my concerns was the differential housing bushings and I might just go ahead and get rubber bushings for it while everything's already apart. She's not going to see much track time though. Most probably 1-2 strips a year at most and maybe a single trip to Willow springs once everything is done. That way I could find out if my cooling system is up to par, and if i'm truly satisfied with the suspension components. After that most probably no more track though. She is literally more than twice my age and makes all kinds of creaks and noises while turning. While these things are bound to happen on a car this old, it's literally my first "project" car if you could call it that. Hopefully the bushings in the front + rear suspension upgrades will get rid of a lot of the sounds that worry me. Otherwise, I might just have to ask for some advice here again! :TU: Also, I've been trying to find some decent quality rubber bushings for the rear housing. Do any of you know where I can find some high quality bushings? Would OPG repro bushings be good enough? - I ended up purchasing the premium rear rubber bushings.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle Your proposed rear suspension setup has been under my ragtop for 9 years, the only change since then having upgraded from KYB to Bilstein shocks. My springs are Moog 5415, which give it a little more clearance for the 15" wheels and 245-60 tires, but without that old street-freak hijacker look. Front was rebuilt with stock rubber, a thicker sway bar and urethane end links. I'm not a fan of all poly on mixed roads driving - too harsh over less than perfect surfaces. Handles on rails and very well balanced overall (the firm feel steering box helps a bit there too) and not the least bit uncomfortable on my Florida roads.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle If you notice any difference in handling it will be positive. I have Metco upper and lower control arms with harder bushings and the HR Parts n Stuff rear bar. I also have No Hop bars. The car handles great.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle Perfect! That's exactly what I was hoping to hear. Thank you everyone for your input and advice.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle The best bang for the buck on the front is to get the bigger bar, poly bushings in the sway bar. Next is to do tubular upper A-arms with long upper ball joints. This allows you to dial in a lot more positive caster and a touch of negative camber. The lower A-arms are minimal advantage. Just make sure the bushings are good and the ball joints are solid. Those things, along with good shocks and tires, will plant the front end like a new car. The difference in my 70 (with these mods) and my 71 (factory without) was so night and day that it was the first thing on my list to do to the 71.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle I just finished installing the rear suspension components! HOLY CRAP! This thing handles amazing! :3gears:I didn't expect to be able to take turns without needing to hold on to the side of my door to keep me from sliding around on the bench seat, let alone handling like a brand new car. I have one complication however. Now that I have a fairly large sway bar (1 inch) it tied the chassis together, and now I feel every little vibration from the car. As if that wasn't enough, my wheel's are absolutely impossible to balance and I have tried several places. Are new wheels the only things that can fix this issue? Anything over 50 mph causes extremely violent shaking. I don't hear or smell anything so I'm fairly confident it's not the brakes. Other than new wheels, I also purchased the proforged steering rebuild kit. Could steering components cause vibration?
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle It sounds like your new wheels are crap. A sway bar is not going to cause violent shaking, no matter what size it is.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle I'm sorry it seems I didn't explain myself right. The old wheels are on. I have been told several times they are out of balance. The sway bar simply made it apparent, so much so that I decided to buy 4 new wheels (cragar nomad 1's were the cheapest wheels I could find. I plan on changing wheel size just not now so I decided to go with the cheapest wheels I could find temporarily). I'm expecting the new wheels to arrive at my house within a week or two. I just wanted to make sure that the wheels are the only things that can cause shaking. I want the car to handle perfectly and violent shaking doesn't fit in perfect.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle Your upgrades should not be causing any sort of vibration/"shaking" providing everything is installed and fastened correctly. Keep in mind, with a stiffer suspension, its no longer absorbing as many bumps/vibrations/"shakes" so that is going to be transmitted into the cabin and feel quite amplified. I'd say if you already know your wheels to be an issue, address it (as you are with replacing them) and go from there.
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle If the rear suspension components are adjustable, have you checked your pinion angle?
Re: Upgrading rear suspension, but keeping the front suspension stock? Will it handle that would be my question as well. Unless the tires are WAY out the problem could be as simple as insuring that you have the correct pinion angle. If you changed the rear upper arms I think there's a difference if I remember right from the early to late arms....anyone else chime in on this? From my understanding it makes a big difference in initial pinion angle settings(prior to adjusting, if adjustable)
