Advice needed on rear suspension

[Ohio Ken]

Hello, looking for a little more advice.

I have a typical fox body 4 link rear suspension. This has coils in front of the axle mounted to lower control arm,and has shock absorbers behind the axle. The travel and spring tension seems soft as I rub my tires against wheel wells on some bumps and dips. Don't want to ruin my quarter panels or tires.

My question is: In found a set of QA1 adjustable coilovers that can be mounted in place of the shocks. Should I still keep the coil springs in front of the axle, or completely remove them, and just have the coilovers only?
Thanks Ken

[LMH]

If you're trying to switch the rear suspension to coil over/shock set up, that should be the only springs used on the axle. QA1 makes springs in different pound ratings if it's too soft or too hard. My opinion, about #450 is a good starting place.
Larry

[Ohio Ken]

Thank you Larry

[Wbulk]

I think that is way on the high side, more suited for IRS. . I don't know what your rear suspension travel is but 250-300 lbs. would be reasonable for a solid axle.

[LMH]

You have to keep in mind the front rating as you don't want the front really soft and rear stiff. The whole car needs to work together. Also with or without anti sway bars. My Hurricane came with 350 on the rear solid axle. I felt like it was a little soft but I switched it to IRS and went to 450.
Larry

[Wbulk]

Most of these cars weight about the same so I have often wondered why manufacturers vary so much. I believe Hurricane and FF are on the high side for their solid axle cars, which is unsprung weight. IRS usually are heavier to support that rear IRS unit. But since a solid axle is not supported by the springs they are usually lighter. Could be that some manufactures put heavier springs in to keep from rubbing the fenders without bump stops.

[Ohio Ken]

On the QA1 coilover that in am looking at, seems to call for much less spring rate: these rates are directly from their chart based on front and rear axle weight.
1750 ft-1900r= 350# spring rate
1525fr-1659r= 275#
1325ft-1450r= 185#
1150ft-1250r= 125#
I don't know what my front and rear weigh but I think it would be closer to one of the last 2. But then look at the spring rate 185#? Seems light.
I wonder if coil overs use different spring rates than just straight up coil springs?
At $400.00 for a set, I want to get it right the 1st time. Now even more confused?
Ken

[Ohio Ken]

On the QA1 coilover that in am looking at, seems to call for much less spring rate: these rates are directly from their chart based on front and rear axle weight.
1750 ft-1900r= 350# spring rate
1525fr-1659r= 275#
1325ft-1450r= 185#
1150ft-1250r= 125#
I don't know what my front and rear weigh but I think it would be closer to one of the last 2. But then look at the spring rate 185#? Seems light.
I wonder if coil overs use different spring rates than just straight up coil springs?
At $400.00 for a set, I want to get it right the 1st time. Now even more confused?
Ken

[Luce]

You're missing the physics on the reason for IRS having considerably stronger springs.

With a live axle, the springs move the same distance as the tires in. With an IRS, they're usually inclined and have leverage against by being mounted on the lower control arm between the frame joint and upright joint so they only move 60%-70% what the tire moves.

With the greatly reduced unsprung weight of an IRS, you need much less shock and can actually run softer (effective) spring rates than a live axle.

Back to the OP, springs are only $40-$50 each new, so it's not the end of the world if your first guess isn't spot on. I would start at 300 if it was my money.

[G_Edmonds]

Classic Roadsters recommends about 350# front and about 250# rear for a small block car.
-Greg

[Wbulk]

I have looked at QA-1s chart to. With a straight axle you have limited travel, not like a regular car that the chart is for. If you are rubbing now you will rub with the real light ones. Summit has the springs the cheapest.
My car came with 10-185s. I have 1 1/2" of travel and was hitting the bump stops regularly. Weight is an issue. I weigh 250 so I went to 10- 225. The ride was good by still hit the bump stops sometimes on city streets. I then went to 10-275s. The ride is not quit as good but this works pretty good. The cars corners better. If this is just for street use their are other less expensive QA-1 options.

Interesting that for solid axle cars Shell Valley, Lone Star, and B@B come with lighter springs. While FF and Hurricane come with heavy springs in the rear. I called Hurricane just to see the rational and was told that's what the original company supplied, but they would give you what you wanted. My gut feeling is it's just to keep from rubbing as they don't have bump stops.

[LMH]

I tend to want it stiff as compared to most but you're probably better off starting a little lighter in rate. I think 250 is too soft, so maybe 300 is a good number.
But what does the front have currently? Are you going to change those at the same time?
Larry

[Ohio Ken]

Originally Posted by G_Edmonds

Classic Roadsters recommends about 350# front and about 250# rear for a small block car.
-Greg

Thanks

[Ohio Ken]

Thanks for all the replies, I an going to talk to Speedway about the Qa1 that I scoped out. I only picked the particular coilover because it took the least amount of modification. I would probably want the 275 or 300 lb spring rate. Just strange they call for that on a 4000 lb plus car, as our Cobras are closer to 2400 lbs

[Ohio Ken]

Just thought I would update on what I am doing.,my CR was built in 1992, and only has 8000 miles, but due to it's age, things like spring isolators and 4 link bushings crack or dry out, shocks probably loosing gas etc. I decided to start with brand new aftermarket upper and lower control arms with poly bushings, new spring isolaters, and new KYB Gas Adjust Shocks ( for jeep Cj5), as my car came with Monroe shocks for a Mercury Villager. I am also going to install larger bump stops , just tall enough to prevent tires hitting wheel wells.
My reasoning was this, the for link was designed to have separate springs and shocks, so I was concerned about re-inventing the wheel by going just coil overs.

I will drive the rest of the season with this set-up too see how she feels,handles. If by winter I am still not happy, I will re-consider going to coilovers.

[MaSnaka]

Ken I seem to recall DV or maybe it was Don Scott saying the gas shocks were too stiff for the CR suspension and recommended against them. I thought you should know before purchasing. I have the rear coil overs with some mods to the rear end to increase the strength to the mounts, double sheer vs single sheer. I did not like the direct conversion to the coil overs, eliminating the spring perch and relying on a bolt and spacer for support. You can see what I did in my gallery.

John

[Ohio Ken]

John
Thanks for the tip on the gas shock. I did already order them. So I will see how it handles.

There is definitely a down side to buying a car built 22 years ago, without receipts , or assembly manual, or being able to talk to a previous owner. As well as, the build company being out of business. But then again, very affordable up front cost, vs a new f5 or Super, and others. I would love to have a new Super, they are very sweet, but more than double my investment.

As far as the current suspension, I would classify the front as very firm and the rear as soft. The rear shocks seem to still be in good working order, but soft. Do you recall what shocks your running before the coil over conversion?

If I end up with coilovers at some point, I agree with the double shear confidence.

[MaSnaka]

Ken, They were Monroe shocks. I don't know from what vehicle. One thing I discovered while taking off the original springs is that they had threads at the top, maybe it was the top of the spring perch, which were covered by the carpet on the interior. They could be adjusted for ride height.

John

[Ohio Ken]

Originally Posted by MaSnaka

Ken, They were Monroe shocks. I don't know from what vehicle. One thing I discovered while taking off the original springs is that they had threads at the top, maybe it was the top of the spring perch, which were covered by the carpet on the interior. They could be adjusted for ride height.

John

Thanks John
My current shocks are Monroe too. I traced the part number to fit 02" Mercury Villager mini van, as well as older jeep cj5,and cj 7.
And yes I see ride height can be adjusted behind seat under carpet. That was the first thing I was going to do until closer inspection found the bushings and spring isolators to be dry and cracked.
I will now go for replacement of bushings and isolators, adjust ride height. Try with current shocks and compare with the gas shocks I bought.
I have no intention of racing or even hard launches. Just a nice cruiser that is tight, is what I am looking for.

[MaSnaka]

Originally Posted by Ohio Ken

Just a nice cruiser that is tight, is what I am looking for.

That's where it begins but you keep wanting more. It's best to work up to it slowly. You learn your car's personality better that way. Stay safe.

John