C8 Z51 on track

[slegros]

Finally got out on track with my Z51. Came back from Spring Mountain, really enjoyed that, got out to TMP for a day.... In both cases completely stock Z51s with the exception of brake fluid. Great track car!! One of the better ones I've owned!!

FWIW, a few notes:

- I like the feel of the stock Z51 pads, decent street/track pad, seemed to wear somewhat quickly on my car. Will try other pads, but the stock Z51 pads felt good and the stock brakes were not a weak link either at SM or TMP running what most I think would call respectably quick lap times (1:20 on SM East on a 42C day, High teens at TMP on a 32C day).
- Brake fluid: Endless RF-650. IMO FAR better than Motul or SRF. By a large margin the best I've ever used.
- Stock PS4Ss seem to wear well and will do OK for what they are.... They tend to be a bit "greasy" and let go very progressively. Great for doing moderate lap times and intermediate level drivers. NG if you want to go faster. The weak link holding the car back from faster lap times IMO. They seem to like hot pressures around 220-230 kPa. Track manual said something about 220-240 kPa hot, but closer to 220 kPa hot seemed best for me.
- Z51 with Magride suspension works well IMO.
- Track mode with PTM set in "Sport" seems a good starting point for a dry, warm day.
-Really liked the feel of the all-weather "Jake" floor mats they were using in the SM school cars. Bought a set. Used to take mats out of the car for lapping, but these mats give a nice firm feel under heel, obviously safe to leave in.

I'm running a compromise alignment with all specs set to GM track specs except for camber which is set at F: -1.3, R -1.1. Tires are wearing well both on street and track so far. Just enough camber it seems to stop chewing up the outside edges heavily on track, and inner edges seem fine on street. Noticeably cleans up the tendency for the car to "snap" from understeer to oversteer, no tram-lining on the street.

Modified the rear brake ducts somewhat for faster install/removal. Drilled a hole in the lower half to allow me to leave the 2 halves assembled, and access the one screw "inside" the duct. Can put a small piece of duct tape over the hole, but doubt it will make much difference... Install/removal, can now be done with a trolley jack in only a few minutes. 3 screws each with a nut driver. Installed better hardware to connect the halves, will leave in place (washers and nylock nuts).

Would love to hear from others about any setup info, track experience, non-OEM brake pads and tires!!

 

[HappyCamper]

Hello Slegros,
I also did the Ron Fellows in Pahrump which was allot of fun. Was there about a year ago in similar temperatures and zero issues with brake fade or car handling even with the oppressive heat.

I have been to Mosport (CTMP) on the big track a couple of times this year.
Stock brakes and brake fluid still in the car. Brakes are excellent with the eBoost (brake by wire) and have not experienced any fade and handle hard full on braking entering turn 8 at around 225kmh with zero issues and full confidence.
Doubt that I will change from stock Z51 pads when it comes time and will most likely stick to the dusty stock pads which work. No aftermarket company that I have seen claims to make a all around street to track brake pad and I am not getting into changing out pads every time I feel like tracking.

PS4 Sport tires have unbelievable wear characteristics, I measured tread depth before and after close to 80 laps and only lost 1/32" on the back tires and not measurable wear on the fronts which I found remarkable for how hard I was driving. I understand that if you wanted those 2 extra seconds that Pilot Sports would be the way to go, but to me unless I have a set of tires/rims to swap out, I am not worried about it.

Mag-ride is incredible, just not on the track but in everyday rough roads and when compared to my old Viper there are places that I can literally drive close to 60kmh faster through rough corners than I felt comfortable doing in the Viper. Took awhile when I first drove the C8 to get used to this fact and to find the edge of the C8 because it handles and drives so nice.

Used PTM Sport at Spring Mountain as that was the only option allowed and for the first session on Mosport, but the rear braking nannies in PTM Sport are making the car lean towards a push/under-steer at least on the fast sweeping corners of Mosport, so I have settled with PTM Race 1 for tracking at Mosport. It noticeably frees up the rear end of the car to reduce the front wheel wear and heat.
Start around 200kPa cold and come off at 230-240kPA after 20 laps.
Still on stock alignment, and no excessive wear characteristics in the two days of tracking at Mosport.

I have had the OEM Jake hard mats in from day one and I too like the solid feel under my racing shoes.

The rear brake ducts are on my car all the time. I don't take them off, and have no issues in the couple of thousand kilometres I have driven with them on. No problem with speed bumps as the air intakes are inline with the centre of the tire so they raise with the wheel as you travel over them. The only thing that I can see being a issue would be a solid object like a brick or something laying on the road to damage them. So far so good.

Like you mentioned, this car is fun on track and a real pleasure to drive on and off the track. No regrets!

 

[drchewchew]

Not sure where you got the idea that C8 has "brake by wire"??? It has a conventional hydraulic system with a master cylinder etc. I believe there is some minor electronic manipulation of brake feel, but it is not a brake by wire system!!

 

[slegros]

Not sure where you got the idea that C8 has "brake by wire"??? It has a conventional hydraulic system with a master cylinder etc. I believe there is some minor electronic manipulation of brake feel, but it is not a brake by wire system!!

The C8 I believe uses the Brembo e-boost system. The brake pedal is mechanically connected to the master cylinder, but the assist provided is electronic, controlling the different braking profiles in tour, sport, track. With the feel being adjusted by an electronic system, I had some doubts as to if or how much swapping brake fluid would have on the feel of the brakes. The effect of changing from the OEM factory fluid (Delco DOT 4 I believe?) to the Endless RF-650 was considerable, and immediately noticeable.

 

[slegros]

Hello Slegros,
I also did the Ron Fellows in Pahrump which was allot of fun. Was there about a year ago in similar temperatures and zero issues with brake fade or car handling even with the oppressive heat.

I have been to Mosport (CTMP) on the big track a couple of times this year.
Stock brakes and brake fluid still in the car. Brakes are excellent even for brake by wire and have not experienced any fade and handle hard full on braking entering turn 8 at around 225kmh with zero issues and full confidence.
Doubt that I will change from stock Z51 pads when it comes time and will most likely stick to the dusty stock pads which work. No aftermarket company that I have seen claims to make a all around street to track brake pad and I am not getting into changing out pads every time I feel like tracking.

PS4 Sport tires have unbelievable wear characteristics, I measured tread depth before and after close to 80 laps and only lost 1/32" on the back tires and not measurable wear on the fronts which I found remarkable for how hard I was driving. I understand that if you wanted those 2 extra seconds that Pilot Sports would be the way to go, but to me unless I have a set of tires/rims to swap out, I am not worried about it.

Mag-ride is incredible, just not on the track but in everyday rough roads and when compared to my old Viper there are places that I can literally drive close to 60kmh faster through rough corners than I felt comfortable doing in the Viper. Took awhile when I first drove the C8 to get used to this fact and to find the edge of the C8 because it handles and drives so nice.

Used PTM Sport at Spring Mountain as that was the only option allowed and for the first session on Mosport, but the rear braking nannies in PTM Sport are making the car lean towards a push/under-steer at least on the fast sweeping corners of Mosport, so I have settled with PTM Race 1 for tracking at Mosport. It noticeably frees up the rear end of the car to reduce the front wheel wear and heat.
Start around 200kPa cold and come off at 230-240kPA after 20 laps.
Still on stock alignment, and no excessive wear characteristics in the two days of tracking at Mosport.

I have had the OEM Jake hard mats in from day one and I too like the solid feel under my racing shoes.

The rear brake ducts are on my car all the time. I don't take them off, and have no issues in the couple of thousand kilometres I have driven with them on. No problem with speed bumps as the air intakes are inline with the centre of the tire so they raise with the wheel as you travel over them. The only thing that I can see being a issue would be a solid object like a brick or something laying on the road to damage them. So far so good.

Like you mentioned, this car is fun on track and a real pleasure to drive on and off the track. No regrets!

Thanks for the info!!

A couple of pads I've used that have similar street/track manners to the stock Z51 pads have been the Ferodo DS2500s, Endless MX72, Project Mu HC+. The first 2 are available for the Z51, but quite pricey. If you want part#s and suppliers, PM me!! Nothing from Project Mu AFIK. I think I'll probably end up running 2 sets of pads...

An interesting side note. AC Delco makes a Police spec rotor that fits the front of the Z51. Uses high grade cast iron like race discs, pillar vent design (as opposed to GM using 2 left side rotors!?) corrosion-resistant coating etc. Seen them with "Made in Italy" stamped on them. Possibly made by Brembo? $114ea. at Humberview parts, part # 18A2652PV. Raybestos also offers the same disk in a different part number elsewhere. Might use these as a cheap track rotor if I do a lot of track days.

Agreed the PS4Ss wear like Iron!! LOL!! Looking at trying something in the 200TW enduro class next, possibly the Eagle Supercar 3 (not 3R), or the Advan AD09. Looked at the Hankook RS-4 and Conti Extreme Contact Force, but unfortunately neither available in std. C8 sizes.

I think PTM Race 1 may be the way to go for most dry days for exactly the reasons you mention!! Instructors at SM swore to me they were fastest with PTM in Sport and said that If I was activating the nannies I was pushing too hard... Wanted to try Race 1 exactly as you say to loosen up the rear end a bit on throttle.

Nice to know about the rear ducts!! I believe the reason they are listed as "track only" is that some people had issues with them sucking in leaves in the fall. Porsche GT3RS has similar rear ducts that are permanent from what I've seen.

 

[HappyCamper]

Not sure where you got the idea that C8 has "brake by wire"???

Sorry, I stand "slightly" corrected.
Search it, all the publications such as Road & Track, Car & Driver are calling it "Brake by wire" as any pedal feel or sensation is not the actual brake pressure you are feeling, but a electronic sensors and a brake feel algorithm to replicate traditional brake pedal feel.

So realistically even in other "brake by wire" systems they all have a physical connection to the master cylinder for safety reasons but the electronics are applying brake pressure to the sensor which in turn boosts the brake pressure which is also dependent on what drive setting or how you have it setup in My Mode or Z mode.
These systems as Tadge Juechter mentioned are adjusting brake pressure independently from what you are feeling in the pedal. Call it eBoost or call it brake by wire, the true connection "feel" to the cars braking system is being simulated. Part of the reason GM recommends replacing pads with stock as the brake fade warnings, level 1 and level 2 do not work correctly with aftermarket brake pads. This would not matter to your everyday driver but would be critical in tracking situations.

BRAKE BY WIRE DEFINITION
Brake-by-wire is an automotive technology that replaces the traditional mechanical or hydraulic connection between the brake pedal and the braking system with an electronic control system. When a driver presses the brake pedal, a sensor detects the pedal's position, and this information is sent to a brake control unit. The control unit then electronically determines and activates the appropriate braking force, often using electric motors or an electric pump to apply pressure to the brakes.