Putting Z-06 suspension parts on your car and staying with stock tire sizes isn't the best way to go. I would look at going all Z-51 components including the brake calipers and rotor sizes, and using DBA slotted rotors.

That includes springs, shocks, sway bars, and rotors. Then I would go with a good ceramic pad for street and a good track pad. If you can pick a pad manufacturer that uses compatible pad material for street and track rotors, all the better as pad swaps for track days is easier.

Be sure to check your brake hoses too. They don't need to be stainless, OEM is fine, it just needs to be in pristine condition.

The tires on the Z-06 are much larger than on the base model, hence the larger components. The Z-06 stock shocks has some issues when cornering on a bumpy turn.

There are some good books on the subject, but GM has already spent time and engineering and testing to come up with what they have.

Basically the suspension rundown:

Tires - contributes the most to your ability to corner.
Springs - Gets you in the ball park
Shocks - controls the springs and its reaction to bumps
Sway bars - helps control body roll and helps keep the tires square to the surface of the road.

We find tune a suspension setup with shocks and sway bars.

For brake pads, I like Carbotech for the reasons mentioned.

For tires, Michelins seem to do well, Even the GoodYear Supercar tires that came standard on the Z51 equipped cars did pretty well once they warmed to track temps (much higher than street temps or autocross temps). I was at 1g with them when I had my '08 Z51. The GS runs higher, but then the tires are larger too.

Good Luck, and have fun!

 

Thanks for the thoughtful reply. I'm probably going to go with RE-71Rs next but I really don't want to jump up on the size... and yeah, that's just me being cheap. I know, I know lol.

I'm doing exactly that with pads. I have a set for street and a set for the track. Raybestos in front and carbotech in the rear (there's a story as to why the brands dont match. wasn't my choice). I JUST put on new rotors and calipers so any upgrade here is going to be a long way out.

I saw a good thread taking about using the Z51 springs or just replacing the front springs but also saw a manufacturer strongly recommend using Z06 springs and JOC sway bars. so I'm trying to decode the two opinions.

What would you imagine I'll experience with the Z06 shocks, stock bars, and bilstein shocks? under or over steer? scary handling at high speed? can anyone say what specifications in this setup cause these issues? (just trying to learn what it all means.)

 

The biggest improvement you can do to your car is to put the most tire and rim you can under the car. Any other changes besides sway bars are a waste until you do this. The stock springs like a 35 mm front bar and a 1 inch rear bar.

Don't forget a performance alignment.

 

When pfadt commissioned O'Connell to help them fine tune their suspension with shocks and sway bars, the car was a Z-06. Increasing tire sizes to maximum (you can get up to 305's in the rear, not sure about the fronts, but size both the same - ie, 10mm in front, 10mm in rear. Try to keep the traction capabilities the same front to rear unless you are trying to fix a problem). Z-06 springs may harshen the ride, but you should do both front and rear if you want, The Z-51 set up was harsh enough for me for city streets, I wouldn't want to go any stiffer. The Bilsteins are an unknown, with the stiffer springs, you might want to go with GS shocks instead. You are trying to avoid sudden oversteer on track-out, something I experienced in the GS. Search the forum for specs on pfadt's sway bars. Phadt produced a comparison chart which gives you a good starting point and points out the front/rear bias differentials between stock selections, the JOC bars, T-1 bars and pfadt's competition bars (stay away from those, the aluminum arms have a hard time with the loads imposed). You can approximate Hotchkiss and how it would place in the chart, and you'll likely run across other vendors products that use solid instead of hollow bars. Realizing GM biased the base care towards understeer for safety reasons, you will be able to see the bias they used to do it with and you will see how the higher performance bars are set up that MAY produce oversteer - or may not. What I like is an adjustable rear bar which will help tune out oversteer. Before you get to this point though, like SCCAracer says, go with tires first (first on the list too) as that is the biggest bang for you buck as far as cornering goes, then tune accordingly. There are books on this subject, I highly recommend reading them.

Pfadt also has a recommended chart for suspension settings. You will want to find that as a good reference point. It'll get you in the ball park. For street/track, the settings are OEM, but the tolerances are tighter. If you are familiar with alignment shop practices, they will put your car on the machine and connect the wheel sensors, then dial in the OEM settings on their computer. If it comes up all green, your good to go, otherwise they will adjust the reds until green. What this does though is leave wide variances (too wide for track use and tire wear) between wheels. Granted we use rubber bushings in suspension components, but they should be fairly consistent loading and unloading, hence the tighter tolerance recommendation.

You may also want to look at going to camber plates. to lock in the suspension settings a bit better. Camber plates will not slip whereas the eccentric adjusters the OEM uses will, and I have yet to see an alignment tech use a torque wrench to tighten eccentrics when they finish. Also, be aware if going to camber plates, I've had to train 4 out of 5 tech's how to set them up, and they still don't get it right. Rather than paying them for additional training, if they are close to what I want, its good enough. When I get more time I'll set them up myself and take it to the shop and have it fine tuned.

 

Yeah I've been looking at that chart and a chart for spring rates, I'm just not sure what it all means. There's obviously a base knowledge that I dont have yet lol. I'll look into some books but is there one you recommend?

People seem to really like to z51 suspension. so using this chart:


If I tried to just use the z06 front springs I would basically have a z51 setup. right? and with stiffer front springs that should help with over steer? but what do I need to learn to figure out how to avoid over steer on track out? as you said, that's what I want to avoid, but I don't know how lol.

I'll keep my eyes out for some used 12" wide wheels for the rear and 10" front for 305 and 265s. I'm sure I'll bite the bullet eventually. $3k for rims and tires is just too much for me.

 

Get yourself a set of used 10.5 x 18 speedlines. They are often for sale on the forums for around 600. Then run a 315 rival or a 305 re71 square setup.

 

Square, really? wouldn't that make over steer worse?

 

The above link will give you several other books on the subject.

From your chart, I would leave the base rear spring, replace the front with Z-06 or Z-51 and start with the Z-51 sway bars. That is for a street tire set up, stock tire sizes.
Shocks might be the Z-51 shocks as a start, the GS shocks are a bit on the plush side. If you grease the mounting blocks for the sway bar bushings and adjust the tension of the mounts with spacer washers, the bar will work better.

If you go with SCCA's recommendation, all bets are off and you'll be better off retuning the suspension because your tire/traction parameters will have changed significantly.

Of course, all of this means you are close to 10/10's and are exploring the edge of the envelope, and you also understand brakes are not necessarily used for braking...

Always approach limits slowly and carefully, I've kept the nannies on and running in B group and have no problem keeping up. As long as all of the tires are moving at the same speeds and moderate slip angle is in the same directions, they won't interfere and will help save you if you push too hard. Especially helpful when suspension tuning.

 

Im sure your car isn't oversteering on a factory setup. You may be inducing throttle exit oversteer with your driving. A square setup works great under c5 and c6's.

My above recommendations come from knowing what works and seeing you don't want to spend a ton of money. I disagree with using nannies for any type of driving other than entry level hpde.

 

that's probably very true, and a very good point. there are definitely corners where the car is pushing but some where I just barely ease on the gas on exit and the back kicks out. I've been keeping nannies on, in competition mode, and it's definitely saved me from my mistakes.

so if the car under steers by design, and I stiffen the front suspension then under steer is going to get worse isn't it?

 

Yes... Are the shocks adjustable and in new condition?

 

new, yes (year old). adjustable no.