Barbara_S

Autocrossing - I have been looking at the suspension chart comparing
Z51 and ZR1 because I have gotten very comfortable with the way my 88 Z51 drives - I want the ZR1 to be as close in feel to it as possible.
My 1st changes are a quick steering rack and 11 wheels all around. Now the suspension is harder to decide on...

spring rates / wheel rates / sway bars:
Z51 115.5 57.2 30.8 33.5 30 S 24 S
ZR1 96.2 39.9 27.1 25.7 26 T 26 S

I think the ZR1 is 200 pounds heavier in the front so I have to consider that too.
So, what would CF autocrossing experts do to the ZR1 suspension without breaking the bank?

Solo2GS

Depends on the class that you are in. Assuming SCCA A-Stock then you can only swap in the Z51 spring from the same year assuming it is a stiffer spring.

Not sure if the Tubular 26mm bar is as good as the 30mm solid bar, but many make an aftermarket 30 or 32mm front sway bar that is allowed in AS.

Shocks are important too. Not sure how many miles you have on them, but if they are Bilstiens then can usually be rebuilt and revalved better.

Proper alignment as well. Some good negative camber in front and rear.

However with changing to 11" wheels all around that knocks you out of AS. It still depends on what class you plan on being competative in. Lowering helps too...

Slalom4me

Notice how the Z51 cars stepped down from the 115.5 front
spring in later Z07 incarnations but stayed with the 57.2 rear.

ZR-1 96.2 39.9 27.1 25.7 26 T 26 S

Z07 90.1 57.2 29.4 33.5 30 S 24 S

For greater attainablility, lower cost and less physical work,
consider setting your sights on the later Z07 specs.

I use N/mm * 5.710 = lbs/in to convert

39.9 N/mm is equivalent to 227.8 lbs/in
57.2 N/mm is equivalent to 326.6 lbs/in

VB&P does not offer a 327 lbs/in rear spring, but on request, they
may be able to hand-select a low-limit spring that approximates this.
As it would be equivalent to the Z51 for the same year, I believe it
passes muster. The rear is simple and fast to change. (This will
reduce bottoming at the rear while cornering and move the
car from understeer towards a more neutral steady-state feel.)

The stock ZR-1 96.2 N/mm front spring can stay for starters.

New 30mm sway bars are not readily available, you'd need to hunt
down a used one. New 32mm bars ARE readily available, but this
is a lot of bar and leads to understeer, relative to a 30mm. My vote
would be to search for a 30mm and stick with the 26mm until a 30mm
became available. Stiffen front roll rate with a larger bar but do not
exceed what can be balanced.

.

Barbara_S

I'm saving my A stock 88 for SCCA but the local Ford clubs don't pax or class - Anything goes which is why I bought the ZR1, assuming I'd have the same feel as the A stock car but more power. I'll be stuck with Vipers and many Z06's on very fast courses.
I was wondering about lowering the car too ubut didn't know if that was an option and viable.

Solofast

Simple,,,,

Just take 200 lbs out of the front of the car

Seriously, the ZR1 is front heavy and you are going to have a hard time making it handle as well as as a properly set up Z07/Z51 car...

Lowering it would help tho, not sure the best way to do that, I never lowered any of my stock class cars...

Scott Farmer

Could you order the ZR-1 with different springs than the ZR-1 package?

Solo2GS

To lower the front you need to take the monospring out and replace the shim with a different one. These shims are on with epoxy.

Back uses lowering bolts.

Jeffvette

Nope

Barbara_S

Yes, the AC could go, and the battery, and the stereo , or maybe I couldust carry a couple of bags of sand in the hatch to level it out.

I kind of know it's not going to be the same -thanks

YorkL8apex

1. Revalve the Bilstiens to "Morocco" settings,
2. Replace rubber with Poly bushings.
3. Gary at Vette Brakes has made some "special" ZR-1 front and rear springs for AX that really make a difference.

I did 2 and 3 on my '91 and its pretty solid now. A buddy I AX against did 1 and if you want it to rattle your teeth like an early C4 Z51 car go with that too.

Barbara_S

thank you all - I think I've got a plan to get a decent set up to get going this spring. Maybe I'll have to drive the car differently too but if the car is ready, I can take it to an evolution school before the season starts.

I just hated my first autoX year on old tires and a street alignment in my 88. I struggled for 1/2 a season before getting those 2 things fixed and finding I didn't have to be always be in last place.

Anyway, thanks - I'm trying to absorb what you guys have said.
-Barbara

Race Prepared

VBP carries the 30mm sway bar however, with the nose of your Z being 200 lbs heavier than the Z51, the 32 might be best for you. Something you will have to try...

[IMG]

Slalom4me

When did someone last get a 30mm from VB&P?

.

ZR1 MK

The first critical change, if you plan to keep and use the bilstein shocks and system, should be the FX3 shock controller with a custom chip. I use and prefer the A207. QA1 has nice dual adjustable shocks if you dump the FX3 system. A 30 mm front bar would be next. Then early 1991 Z07springs (same as Z51). Then bushings: Global West A arm, urethane for the bars, and rod end for the camber and control bars.
Note: The ZR1 isnt 200 lbs heavier on the front.

cv67

Quick ratio steering rack. Wont make it handle any better but it will respond quicker.

ZR1 MK

32 front bar is only good for wider tires (315 min) and the rear bar needs a little help for a perfect balance. My tire wear on the track is much improved with the 32 bar.

ZR1 MK

I need quick ratio steering, but a smaller steering wheel does the trick too.

Barbara_S

I'm not sure that would be it for me - the quick rack was an easy purchase and my events need it.

Mike -thanks for the other tip on the sway bar with 315s - that's what I'll be getting.

I also have a set of scales so when the weather is good, I am going to
weigh both cars and see what the real distribution is. Or if anyone knows already I'm

ZR1 MK

Is you steer rack new or rebuilt? Cost and source? Core requiremnet?

I would be interested in your weight results. I have seen comparisons over the years, but most didnt tell the whole story. Fuel level, spare tire and any mods will effect the outcome. Do both cars the same. If you want, I can email you my weight specs (excel spreedsheet). My car has mods, so its not the same as stock, but its good for reference.

Barbara_S

Hi Mike, my steering rack is not new or rebuilt. It's original and I bought from a salvage yard off car-part.com - I looked for low mileage 88's with 17 inch wheels. They had 1/2 a dozen 2 weeks ago.

I would love to see your weight specs -please send them. When I get the scales ready and check my 2 cars I'll post - the ZR1 has headers, but that's about all that's ery different.

Oh, and your comment on a smaller steering wheel made me think about adding an 88 steering wheel to my ZR1 because I love the balanced light feel of it compared to newer wheels with air bags. At first I worried about giving up the air bag, but because of it's age, it's probably not good anymore anyway. That's not at the top of the list but it's on the list.