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85 Z51 Shocks: Bilstein B8 vs QA1 Single or non Adjustable
Hey all,
My 1985 Z51 4+3 car has around 130k miles on the original Bilsteins. I want to make the most of the the Z51 springs, swaybars, early steering geometry, and my local track.
I am considering 3 shock options. Can anyone offer any input on them, or alternatives?
New Bilstein B8 for $420 for the set
QA1 non adjustable for $650 for the set
QA1 single adjustable for $810 for the set
I like the B8's. They also last pretty well. On yours they have gone 130k miles
I have put B8's on 4 C4's and they have worked well.
I do not know about tracking your car. There may be other shocks that can tune your car to the tracks you run. Possibly better choices, but it is hard to beat the B8's.
(I also had an '85 4+3 Z51 car for over 25 yeas and loved it.)
I'm pretty sure the B8 aren't available for the front of our 85s. You can get B8 for the rear but only B6 for the front.
I went with the Ridetech HQ single adjustable in my 85. (Which has Z51 springs and sway bars.)
If you want to get the most out of it. Get the original oem shocks rebuilt. Biltstein may still do them, possibly someone knows another possible resource. Either way don't throw them away, the are worth money.
If track action is in your future you need to find out the rules depending on sanctioning body ...scca ,nasa.or local sports car clubs. How the different types of aftermarket parts can effect classification. Sometimes the parts you install can move you in a class you arent competitive in. The other is budget adjustable shocks aren't cheap. Viking and ride tech are popular
Max ive got to believe that the aftermarket adjustable shocks can be made mega stiff. errrr mega dampened actually. thats pretty much what i did with the manually rotated fx3 shocks to full stiff. it seriously slows down roll and stabilizes the car in high speed corners. the car is uncomfortable driving to the track. unfortunately thats not an option for early cars.
my thinking is that the b8’s will not offer enough damping rate—wont be stiff enough. — id probably try to get an aftermarket shock that i can make extremely resistant to movement!
I have the Z51 front Bilsteins for 1986, pretty much new, if you need a set. Installed QA1 MOD shocks (4 way adjustable with replacable modules). Frankly the Bilsteins are very good, the front end of the car was excellent (lowered/wedge Z51 springs, hollow FE7 sway bar).
Put the Bilsteins on the Maxwell shock dyno (because they were so good), there's no digressive valving to blow off high speed bumps, but more than makes up for it because there's virtually no hysteresis. That's the problem with the QA1 is once you dial in a little more control the hysteresis creeps in. Only performance benefit using QA1 front with the OEM Z51 springs is I see is adjustability for different springs, provisions for coils, and less weight with the QA1... and these are the high end models.
For the rear, different story. OEM ear really sucks and needs a lot of work, especially if you carry a lot more power than stock, and especially on terrible early C4 camber curves. But the OEM front early C4 was wonderful to start with.
My plan is to stick with the factory 85 Z51 springs and sway bars for the foreseeable future, and I don't see any real crazy power down the line for this car.
So maybe Bilstein Z51 spec fronts and QA1 single adjustable rears?
I don't recommend the QA1s. I think their single adjustment affects both compression and rebound, whereas you really only want it to change rebound. I also don't recommend mixing and matching brands without an especially good reason. If I were you, I'd either get Ridetech HQ or go to After Dark Speed and inquire about a set of their lowest-option Viking shocks. In both cases, you should talk to someone at the company and tell them your setup (84 Z51 setup) to get the best valving for your needs, and obviously you don't want a coilover setup.
Indeed it appears that the single adjustable QA1 shocks a have both rebound and compression being adjusted by the single adjuster.
I emailed After Dark Speed as I don't see any 84-87 shock offerings on their website, but I do see After Dark Viking double adjustable C4 corvette shocks 84-87 listed on the websites of 3rd party vendors.
Thoughts on the Ridetech single adjustable shocks vs the Viking double? Price is similar.
Also all of these are more than twice the price of a B6 front and B8 rear Bilstein set...
I'm not 100% sure whether I'd choose Ridetech or Vikings via After Dark. However, I can tell you that Ryan Mathews, the owner of After Dark, races what he sells (including a C4) and provides lots of good tech assistance. He can give solid guidance for the best valving for your needs, and where to start with the settings. To me, that kind of assistance is really valuable. Also, it's nice to be able to adjust compression independently of rebound like that double-adjustable allows. So I guess I just talked myself into talking you into the Vikings.
Yes, I know the Bilsteins are cheaper. They aren't bad shocks. However, being realistic, I don't think the B6 or B8 was valved to cope with 84 Z51 spring rates, and they aren't my favorite for compliance reasons anyway. The bottom line is that Either the Ridetechs or Vikings will give you better performance at the track and probably a more compliant ride on the street.
I'm not 100% sure whether I'd choose Ridetech or Vikings via After Dark. However, I can tell you that Ryan Mathews, the owner of After Dark, races what he sells (including a C4) and provides lots of good tech assistance. He can give solid guidance for the best valving for your needs, and where to start with the settings. To me, that kind of assistance is really valuable. Also, it's nice to be able to adjust compression independently of rebound like that double-adjustable allows. So I guess I just talked myself into talking you into the Vikings.
Yes, I know the Bilsteins are cheaper. They aren't bad shocks. However, being realistic, I don't think the B6 or B8 was valved to cope with 84 Z51 spring rates, and they aren't my favorite for compliance reasons anyway. The bottom line is that Either the Ridetechs or Vikings will give you better performance at the track and probably a more compliant ride on the street.
Yeah the double adjustment seems nice. I remember having independent rebound and compression was critical back when I raced mountain bikes. Looking forward to hearing back from Ryan.
Also I agree, it is invaluable to support a company like After Dark.
Also for what it is worth, I am using the factory 85 Z51 springs which have rates comparable to the 84 base I guess?
The issue with going Bilstein is that true Z51 spec front valving (B8s) I don't think are available.
The 85 z51 springs are much softer then the 84 z51, they are closer to the 84 base. Chevrolet increased the stabilizer bars when the spring rates were reduced. The oem z51 shocks where designed to allow compression using the spring to absorb the dips while resisting extension dampening the rebound of the spring.
Hi,
I´m in the same process on my 85 with Z51 suspension.
Bilstein can rebuilt your old shocks for around 100 bucks each, but they want you to send pretty clean shocks.
If you want new shocks from Bilstein for 85 with Z51 they suggest following Bilstein part numbers:
Front 24-002288, rear 24-184588. These are B6 shocks for cars with original ride height.
They want you to have B8 shocks on lowered vehicles.
Yes, I can confirm that I got the same recommendation from Bilstein representative and I ordered the same B6 shocks. Mine are still in the box, you are well ahead
Let us know what the experience is, I will have to wait for spring time...
09-08-2023, 09:45 AM
85 Z51 Shocks: Bilstein B8 vs QA1 Single or non Adjustable
