Suspension Upgrade

[emmvette]

My car is at the ZR-1 specialist's for some R&R this winter and when I get it back I'd like to finish tackling the suspension upgrade this spring. I'm hoping some are willing to share some of what you have tried and know improves the handling for autocross / track use. Right now I have upgraded bushings to poly but otherwise have a stock suspension. I have plenty of HP and good brakes, so suspension is the next step of improvement. I'm looking into getting the shocks revalved (I have a thread on questioning spring rates today) and am curious what other items I should be considering for improvements. I run either Nitto NT-01 or slicks depending on where I'm at, in stock sizes.

I don't plan to go to coilovers, so that is off the table. Hope everybody had a great Thanksgiving!

[XfireZ51]

DRM brackets
Larger sway bars

[lbszr]

I ran mine with stock set up. Stock springs with Vbp 32 & 26 solid bars. And what I like the best now is vbp 1147 front and 6xx rear spring with the 32 & 26 bar. It's really hard to tell what that spring rate number compares to, but from what I figure, it's stiffer than anything that came on the c4. It understeer terrible with stock size tires, but great with 315 square, it actually favors oversteer now. If your going to keep stock size, maybe lower front spring or smaller bar.

Custom alignment helped a lot. 2.9 neg camber .03 inch toe out, 2.1 neg on the rear with .06 inch toe in. It was corner balanced also. The spring from vbp is adjustable for the balance. This works for the track, don't know about autocross. Tire wear is pretty even with this alignment on hoosier r7. The stiffer springs allowed it to go lower without bottoming out also. It has very little body roll.

[Vette Guy]

I think you are on the right track with everything suggested. I've had a great experience with all the DRM products.

VB&P posts a good reference for alignment specs:
https://www.vbandp.com/instructions/...pecs/file.html. I believe you can get up to ~1.5 neg camber up front w/o pulling the bushings out (just shims). You'll need to remove your upper A-arms to get the bushings out and get the full ~3 degrees.

A SPC Fastrax Camber/Caster gauge allows me to do my own alignments. Depending on what I'll be doing, I occasionally set the car back up for the street. https://www.summitracing.com/parts/sps-91000. Revalved shocks will make a big difference as well.

I run the stock rim sizes, but have been cautioned about making sure my high-pressure power steering hose is fresh and running redline fluid should I run 315s up front. DRM sells a braided PS hose for this reason, but only for the LT1 cars. I know that the ZR-1 Pirate race car went into the wall at Laguna Seca, coming out of the cork-screw, as a result of the PS hose failing.

Also consider the 13:1 close-ratio steering rack if you are primarily running autocross. It's really quirky on the highway, but not bad for the track. Lastly, I absolutely love the DRM stainless steel caliper pistons, as well as their brake bias spring. I consistantly brake hard, and have yet to experience brake fade (running high-temp fluid and have brake ducts). I run Carbotech XP12/10s, DBA T3 front/StopTech Cyro rear rotors on the '88 Z51 Corvette (32/26 bars) w/ R888s for practice and R7s for race.

Regards,
Mark

[Billy Mild]

Originally Posted by Vette Guy

Also consider the 13:1 close-ratio steering rack if you are primarily running autocross. It's really quirky on the highway, but not bad for the track. Lastly, I absolutely love the DRM stainless steel caliper pistons, as well as their brake bias spring. I consistantly brake hard, and have yet to experience brake fade (running high-temp fluid and have brake ducts). I run Carbotech XP12/10s, DBA T3 front/StopTech Cyro rear rotors on the '88 Z51 Corvette (32/26 bars) w/ R888s for practice and R7s for race.

Regards,
Mark

Does the MC need to come out to the brake bias spring?

[RussMcB]

Originally Posted by Billy Mild

Does the MC need to come out to the brake bias spring?

No. I forget the exact procedure but it comes with instructions and I don't remember it being too difficult when I did it a year ago.

[lbszr]

My car had to have the offset bushings in the lower control arm to get 2.9 neg camber.

[XfireZ51]

Originally Posted by RussMcB

No. I forget the exact procedure but it comes with instructions and I don't remember it being too difficult when I did it a year ago.

There's a large hex on the front of the cylinder. The spring and piston are behind that.

[Billy Mild]

Originally Posted by XfireZ51

There's a large hex on the front of the cylinder. The spring and piston are behind that.

Do you need to bleed the brakes or anything?

[batchman]

My experience on springs/shocks - Our first steps on ours (street and autocross) (after alignment) was to reduce rear bar to get some of the oversteer tamed. That and the quick rack, but we found we had to go to a Turn One "stock replacement" pump to get that settled out.

It was just too soft. Next step was a VB&P sport front with their matching Bilsteins, and (don't listen to them about the rear) a Hypercoil replacement 88 z51 spring with again matching Bilsteins. This worked, was good on the street and about a match for a c5 z06 as far as ride and weight transfer/turn-in etc.

My new setup (autocross only) is a 1250lb front/500lb rear with Penskes, still working on dialing that in. If it works out I'll probably be looking to sell the setup above.

HTH,
- Jeff