X25

Wow, thanks! 165 translates to 942 lbs/in, that's very stiff! Am I reading this wrong?

EDIT: I was told since the way OEM springs are mounted is different than coilovers, the rates are not directly comparable.

X25

Just started a discussion regarding C7 spring rates. Looking forward to seeing what others would have to say:

https://www.corvetteforum.com/forums...post1593003162

X25

I finally got to try my new tire setup (315/30/18, 325/30/19) at the track.

TL;DR: I canceled my Monday track day and ordered a few parts.

I only did 4 or so laps at the track, and it was enough:

• The car felt pretty soft. It felt like it was leaning quite a bit in turns. No wonder, I've also heard rubbing noises in some of the tightest turns.
• Looks like these tires provide great traction! I am very excited about it. The rear was also much better, which stayed planted in some of the turns I've previously had issues.
• Unfortunately, looks like the great traction these tires provide overwhelms the suspension. It was just too soft, and felt a bit like a boat at times.
• All 4 tires rubbed to some extend. The fronts rubbed much more. One surprising fact was that even at the front, as the suspension compressed about 3" (!!!), the tire completely tucked with the dynamic camber, rubbing the inside wall of the fender instead of breaking it apart.
• Looks like if my wheels were a few mm more tucked in, the tires would not rub at all. We know that 18x10.5 ET58 C5Z06 wheels do no rub. My ET52 wheels rub a bit. The originally speced wheel at ET57 would likely not rub. That said, I like the current offset since I don't want to be too close tot he brake ducting, etc. inside.

The front tires were protruding by about an inch, and they are at least 2" away from the fender.


Initial action plan:

• Coilovers (set to lower drop): Called in LG. They will set-up the coilovers for 0.5" drop instead of their usual 1" drop. This should give me better chance of clearing the tires. The coilovers also come with much stiffer springs, especially up front. This should also help immensely.
• Sway bars: Switching to LG sways; ordered them on my way back home along with their stiffer endlinks, etc. Much stiffer sways will both let me tune my f/r balance, and will also substantially reduce the lean.
• Camber / Rear adjustable toe links: Also ordered Granatelli rear adjustable toe links. I plan to make the car -2.5 camber all around. In order to do this, I will need to correct the rear toe, and these links will let me do that.

Backup ideas (if the action plan doesn't work):

• Wider fenders: The front Z06 fenders are very easy to install, and would cost about $1300 + paint.
• Different offset: I could also get front wheels with a tiny bit more offset, around 56mm, which should fix the issue.
• 295/325 tire setup: This could be done with Trofeo Rs, and would probably not rub at all. I really want 315s to work, though. It feels like the right size for this car.
• Do nothing: After the action plan, the rub have to be much less severe. I could let it continue destroying the fenders a bit, until it stops or finally gets rid of the fenders : P

Jakeman11

Thanks for all the info on this thread. It was and is extremely interesting. You really put a lot of time into this.

Chets LS3

I can tell you the LG bars help a lot! I don't have any T1 stuff under my car and just a MRC car. let me see if I can find some pics

Can't find any apples to apples pics. But I will say it's a difference in bars only!

X25

Thank you; it's my hobby after all : )

Well, I will soon get the LG bars, and we'll see! I'm not sure if they would be too stiff for the coilovers, but we'll see. In your case, they would definitely improve the handling for you, since MRC car comes with softer springs.

When you look up the sway bar stiffness across different car lineups (like Viper, Corvette, Camaro, etc.), the sway bar stiffness does not necessarily increase as you move on to the sportier model. In fact, gen 5 Camaro Z28 comes with softer bars than the 1LE model (which has the same weight, and is also a squared setup). When you look up Vipers, the sway bar stiffness slowly increases, but not as much as spring rate increase would suggest, as you move from regular to T/A, ACR, and ACR-E.

In short, I might be leaving a bit on the table with too stiff bars, but I don't know enough to figure out which bar I'd need, so I'll go with LG's recommendation, and use their bars. I will probably use the front at stiffer setting, though, so I can balance f/r better with my almost-square setup.

-----------

Update on rear rotors:
Since I did the switch to the C7 Z06 brakes (which I did at 20 miles), I was always worried that I was crippling the car's performance by replacing C7 Z51 rear rotor at 18.1lbs with Z06 rotor at a whopping 24.8 lbs. This happens due to the fact that rears handle the hand brake, and OEM rotor has a steel hat to accommodate it.

I've decided that I should address this next time when I replace the rear rotors (which might take a while). Girodisc reat 2-piece rotors use an aluminum hat, and it has a steel liner for the hand brake to work. The vendor for these (Xplosive Performance) doesn't know the exact weight of these, but I was able to confirm the aluminum hat, so it should be much lighter. I will order a set, and weigh it; very excited about this!

Other/misc news:

I finally increased the space between lift columns (by 5"), which gives me much more room and makes it easier to raise wide cars.


Added PC PC conrete epoxy around the anchor bolts this time. The usual concrete has 3-4K PSI strength, while epoxy provides 22K+ !!!


A close friend of mine and my brother stopped by today, who are also experienced track drivers. As you can see, I do have tough competition.

BaylorCorvette

Can't wait to hear your feedback on the coilovers!

daleong

I have the AP Racing J-hook rotors on the front of my Z51 and plan to put the rear versions on sometime in the future. Those have aluminum hats and per the vendors, this will work ok with the parking brake, even though they don't have a steel insert. Of course, this is assuming the parking brake is only used for parking.. not doing swedish rally turns on the auto-x course.

Ps. Can't see the some of the pictures you posted to the thread e.g. of your brother's car

Chets LS3

Ap doesn't make rotors for the z06, girodisk just released there setup for the iron brakes.

X25

They're still waiting on the front springs. Hopefully they should ship it by EOW, along with the links, sway bars. Another vendor will also ship the rear adjustable toe links.

By the way, I inquired LG about their GT2 coilovers that they've just released yesterday. Long story short, G2 is their more track-oriented offering.

Good luck drifting with a hand brake actuated with a button : ) I'm wondering how Girodisc tackled the issue. I think I'd still prefer to have an iron sleeve insert for hand brake for consistency. Of course, the most important thing is still the weight.

X25

I heard from LG that parts are shipped on Friday (9/16) and other parts for the final batch of parts started trickling in; I was in for a surprise.



Girodisc C7 Z06 rear rotors look beautiful. As you can see, the provision for the hand brake is aluminum. This means no national drift championship for me; oh well.


... and they are incredibly light at 16.7 lbs! FYI, stock Z51 rotors are at 18.1 lbs, and stock Z06 rotors are at 24.8 lbs!!!!!! These might actually even be lighter than the CCM Z07 rear brakes since they probably have a steel hat for handbrake, too; will check on that.


Also received Granatelli's adjustable rear toe link. I am actually impressed with the quality of these parts. They are also pretty light for an adjustable toe link (BMR units for Camaro were a few times heavier). They are about 1.9 lbs per side.


Bearings look great.


Looking forward to receiving the LG coilovers and sway bars + end links!

X25

Fixed; sorry. The webp image format is default for where I host images, and I sometimes forget to force the host to provide them in jpeg format.

daleong

Hi, when you install the rear rotors, can you take pics and document? Lots of threads and videos out there about front rotor replacement, but none on rear rotors. I'd love to see more detail on how its done, especially the parking brake parts.

Thanks!

X25

There's not much to it, but sure, I can do : ) The coilovers should be here mid-week.

CDH76

While you are in there steps on the coilovers would be nice too

AKKutz

I just received my OEM spats from Trunk Monkey. Looks like their not going to fit with the canards on the APR splitter. Will take a bunch of dremel time. I just held them up to the wheel wells, not tried to install. But it looks like it is either spats or canards!

I may be selling these or returning them!

X25

Yeah, they overlap for sure. I am planning to figure out a way to keep them for the rest of the fender. I really need the protection : )

X25

Coilovers are going to be delivered tomorrow! I decided to do a bit of a prep work, and wanted to note the initial height numbers, and see the impact of weight on suspension.

Methods of measuring height:
1. Measuring hub-to-fender
In my opinion, this is the most reliable method. It obviously only measures the suspension, so the height of the tire is also irrelevant. The problem is, it is very hard to make sure you hit the middle of the hub.


2. Measuring ground-to-fender
This is what I will be using for setting the height of the car after installing coilovers. Why? Because it is very easy to measure, which will make it easier to fine-tune heights.

Car setups
First off, LG manual recommends corner-weight balancing the car with empty tank. However, every shop I know here makes it with full tank? Who is right? I think they are both right, for different circumstances. Empty tank would be good for time trial cars, while full tank makes sense for those like me, who do HPDE events with their car.

In my case, I usually start with a full tank, and do not refuel until it hits ~25%. I try to not go much below that to avoid fuel starvation. So, I figured 70% tank would be the best match of actual weight of the car at the track


The tires are 315/30/18 (25.35"), 325/30/19 (26.73").

I also used a ballast:



Results
T1 with no ballast, 37% fuel
Heights from ground to fender, in mm
LF, RF, RR, LR (in mm)
711, 710, 741, 747

T1 with 160 lbs ballast, 72% fuel
LF, RF, RR, LR (in mm)
699, 701, 736, 737

Remarks

• The heights do not indicate corner weight balance, and often diverge a bit, but considering I have non-adjustable, identical-height suspension pieces on both ends, same height could easily suggest very close weight distribution within rears or within fronts.
• Wow, with the ballast and fuel, the rears and fronts seem to be balanced, at least in height!
• Don't be scared by the huge height difference front to rear, since most of it is caused by the tires. I measured the suspension height difference as well (method 1); front was at 380mm, and rear was at 395mm. So, the rake is only 15mm = ~ 0.6".

BaylorCorvette

Great information, cannot wait to hear your impressions of the coil overs.

Also, judging from the cobwebs on the fire extinguisher I hope you didn't just plant a spiders nest in the cabin

BaylorCorvette

Oh, also meant to tell you. When I was at COTA this past weekend for the IMSA race, Mobil 1 had an engineer come out to talk about their oils. He stayed afterwards to talk oil with anyone that was curious. So I walked up to him and started talking track oil, apparently in the next 9-12 months a new factory fill oil is going to be suggested for C7's that is supposed to be perfect for both track and daily driving. I tried getting more specifics and after he looked around to see who was listening he told me to look at what the European spec is for the C7s. I believe that is 0w40? Anyways interesting stuff.

This engineer is also the Mobil 1 engineer that looks at the oil analysis reports from the oil that comes out of the C7.Rs. I asked him what the oil is like after the 24 hour races and he said it has the usual wear you'd expect but is actually still in great shape. I want to say that he said the C7.Rs use 0w50.