Kamran

True.

I'm not following the gas station analogy!
It seems there are a number of people who run 13" wheels on the forum without any adverse issues. I'm guessing and hoping they are driving a little harder than running to grocery stores, when on the track!

Although the vendor told me I'm the only one in world who had "the" issue with their 13" wheels, I'm pretty sure there are plenty of others....just depend on driving style of drivers! on 13" wheels.

Remember our static test with going thru the Suspension range with car on the lift aligned with my findings testing Spacers at the track. All were fine going to buy milk at the store!

X25

Received the new coilovers!
Penske 8300, 750 lb/in front, 650 lb/in rear



The rears


The fronts


That little bag is all you need for the rebuild (besides tools)


Chose to go with Hyperco 750 lb/in front, 650 lb/in rear.


As expected, every Penske comes with a set of shock dyno sheets to prove consistency, the expected valving, etc.

BaylorCorvette

Very interesting. Curious to hear your impressions.

X25

Well, I had a great setup with LG, but now since I've been wondering about higher end coilovers for a while now, everything is back to drawing board. We'll see if I can make it work. The worst part is that I might not get a chance for another track day for a few months; it snowed for a while, today : )




I needed a special tool for the new type of spring perches. I bought this screw-driver-like tool for $12 from PegasusRacing.


Looks like this is how it is locked into place. Cool.


- Rebound setting is done using a hex tool. I'm thinking about making a simple tool, using the flex drill extension to be able to reach this easier at the track. Oh well. Compression setting is on the canister, and it's much easier to get to.
- On a side note, the build quality of the whole kit looks amazing. Everything is very tight, and the shock bodies' height is set to my specs (which I hope are right). The ugly black thing you see in the picture is the bump stopper, which is normally not exposed, but this was right before I started taking apart the bottom mounts to slide in the springs.


I think Pirellis at 680mm diameter are a bit too tall. When it comes to trying them again, I'll go with 645/660 F/R instead of 660/680 F/R diameters. I patched the damaged parts of the fender with my Gorilla duct tape.


New toolbox and magnetic socket holders! Everything is so much tidier now : )


I had an incident where during my last track day, the hot wheels made the wheel weights' adhesive less strong, and they ended up moving towards inside of the wheel, slightly damaging my right rear brake caliper. From now on, to avoid it, I will get the wheel weights taped to the wheels as shown.


I'll buy the hardware to install the coilovers, and might even finish the install, tomorrow; we'll see.

Kamran

I used to tape my motorcycle wheel weights with duct tape and it would work. Motorcyle wheels don’t get as hot as car wheels, since they are exposed.

I tried using duct tape on the car wheels, but they’d all peel off the sides, where they adhere to wheel. All they did was leave me more mess to clean up. Car wheels get way too hot for duct tape. You might try high heat tapes, like what you tape suspension rubber near calipers.

With the Penske suspension mods, you may be on your way to beat my “five” minute track record!

w00tw00t

So glad you decided to go with higher end suspension!

Not a corvette but I too just upgraded from JRZ RS2 to MCS 2 Way Remote Coilovers on my track BMW M4 (850F, 700R), The difference in how the car handles bumps and berms is remarkable.

X25

I'm glad you've finally made the upgrade! Did you get to try them at the track? Did it make noticeable difference at your lap times? I bet it's a bit more comfortable now, too : )

Looks very pretty!

X25

Update

(1) Coilovers
I installed the Penskes last week, and realized that despite longer shock bodies compared to my previous setup, the car height was not any higher.

This was my goal (and initial plan):

• The stock height is about 699mm / 734mm.
• LG setup height:
  • It is at about 670mm / 704mm.
  • Front: 15" shock, 7mm of spacer/preload.
  • Rear: 16" shock, 12+mm of preload.
• My target height with this new setup: 685mm / 715mm
  • Note: I'm not sure about the exact motion ratio, so these are just estimates.
  • Front: 15.50" shock, 10mm estimated preload
  • Rear: 16.25" shock, 11mm estimated preload

So, this did not work! with 10mm front amd 11mm rear preloads, I hit the following:

• Front: ~666mm - 670mm (same 750 #/in springs)
• Rear: ~695mm - 698mm (650 #/in springs instead of 700 #/in).

Remarks

• After going around and comparing the geometry of setups to understand what's going on, I realized that Penskes mount directly to the car's shock mounting points just like the stock shocks, while LGs use a plate, and this changes the angles. I presume this was done by LG to clear the upper control arm easier. This drastically changes the motion ratio, and as such, my calculations were off a bit. I am not sure if this change in geometry has any affect in handling, but it certainly increases the effective spring rate (vertical component of car's weight on the springs is now less in magnitude).
• I want to do this right the first time as much as possible, so I shipped the coilovers back to Penske, where they will change the shock body length. One good feat with these high-end custom coilovers is that they can set the shock body at whatever we want!
• If we just look at numbers and increase the shock body by the length we need in driving height, keeping that preload, and assuming motion ratio is close to 1 from here on, I'd need 15mm (0.6") at the front, and 20mm (0.8") at the rear. That makes the target shock body lengths at 16.1" for front, and 17.05" at rear. If MR is correct, this would hit the target values. To reduce the target preload to ~5mm, then I'd need 16.3" front, and 17.25" rear.
• Penske states on their website that the coilover bodies need to be about 1" shorter to clear control arms.

In short

• Front:
  • OEM: 17.752"
  • Penske's standard: 16.41"
  • My current Penske: 15.5"
  • My new target: 16.1" - 16.3" (safe; under Penske's spec height)
• Rear
  • OEM: 17.750"
  • Penske's standard: 16.72"
  • My current Penske: 16.25"
  • My new target: 17.05" - 17.25" (might be too long to clear UCA)

Concerns:

• My rear target is actually very close to OEM rear shock length; I wonder if this clears at all?
• I'm assuming 1:1 motion ratio. I've actually increased rear preload of one of the Penskes by 5mm, and the ride height has increased by 4-5mm on that corner, but this is very much imprecise since change is not big enough to measure exact ratio, and the numbers would also be misleading until other heights are also close to the target (or cross weight transfer happens, screwing up measurements). If I exceed the targets and it becomes too tall, I'd be embarrassed to send it back to Penske again : )

Anyhow, I'll discuss this further with Penske engineers, and I'm hoping they have data to support our next targets.



Rears weigh 8.5 lbs.


Fronts weigh 8.7 lbs.


(2) Wheels

I just received the BC Forged wheels!




I decided to get ready for the 345 rear tire test, and removed whatever I can from the fender.


BC Forged RZ39 18x11 ET79. It weighs 20.7 lbs.


I could not completely bolt it on, since I currently don't have a suspension, and the sagging UCA touches the rear wheel. Brake calipers seem to clear easily, though.


The fronts clear pretty easily. It indeed looks like they could clear CCBs. Fronts weighed 21 lbs.


The front wheel's hub.


KNURLED BEAD!!!



This is it for now. I should receive the Penske shocks back next week, and I'll get the 315/345 Hoosiers mounted in the meantime.

w00tw00t

thanks!! going to thunderhill this friday - on the street they feel incredible. turn in and mid turn is instantaneous.. but can't wait to try it on the track!

X25

Got the tires for my experimental setup mounted, today. To my surprise, 345s were indeed not pinched as much as one would think on my 18x11 wheels!



This is 345/35/18 A6 on 18x11 wheels. They don't look bad at all.


You can see that wheel is narrower in this pic, but it's not pinched at all.


And these are 315/30/18 tires on 18x10.5 wheels.


Side shot for 315s.


In other news, my Penske shocks are shipped back to me already:

• The front height is increased from 15.5" to 16.25" (~20mm), while rears are increased from 16.25" to 17".
• It would be better if I could get to 17.25" at the rear, but we fear that might cause interference between UCA and the springs. Penske engineers put down a note stating shock bodies should be about 1" shorter than OEM (17.75") to avoid interference, and this new height is already longer than the safe zone. To mitigate this issue further, I will also try smaller spacers between the upper shock mount and the chassis at the rear, which should further pull the shocks away from the UCA.
• If my efforts fail for some reason, Penske will send me rebound limiters, which I will install inside the shock bodies to limit full open travel by about 0.25". Hopefully, it will not come to that.
• Once I set the heights right and get the car aligned, I will install these tires above and see if they clear. In other words, we'll have to wait for a few weeks for the big moment! I have not seen anyone else using 345s on a Z51 (but saw people fit narrower and shorter 335s), so this might even be a first if it becomes successful. In any case, I know for a fact that the recipe will call for coilovers, which reduces the eligible cars quite a bit for such a setup. Looking forward to it!

Looking forward to trying it out!

AKKutz

Again, no pictures coming through.

X25

Hopefully, all fixed. Google Photos moves the pictures soon after they are moved to a shareable album. If I use the links before this move, it ends up becoming not visible to anyone but me.

daleong

Yep the photos work now..

X25

Update (PICTURE HEAVY): Penske coilover install is now finished!

Data

• Height settings
  • OEM (w/ ballast): 700mm F, 736mm R w/ NT01 315/30/18, 325/30/19.
  • Target (w/ ballast): 685mm F, 720mm R --> ~0.6" drop F/R.
  • Current (w/ ballast; L/R): 685/687mm F, 721/722mm R.
• Shock settings
  • Springs: 750lbs/in F, 650 lbs/in R.
  • Shock body lengths: 16.25" F, 17" R. (Rear could've been 17.25" to make it perfect, but that could interfere with axle).
  • Preloads (L/R): +9/+3mm F, +15/+15 R.

Issues

• Problem: The front shocks were too long to clear the UCAs.
  • Fix:
    • I had to remove UCA bolts to install the shock.
    • The bottom mounts are a bit adjustable (bolt holes are elliptical). I sled shocks' bottom mount towards the back of the car, which centered the shocks by the UCA opening for more clearance.
    • Finally, removed the spacers that came with Penske shocks to increase clearance. Before I did so, I had tested the shock in all positions from 20-90 degrees to ensure spacers are not needed.
• Problem: Compression settings are relatively easy to reach for both F and R, but rebound settings are pretty hard to reach.
  • Fix: Created a long flexible 4mm allen to reach the adjuster from inside the tire. I was still not able to reach when I tried with wheels on, though. I'll try it at the track, leaving the tires on, but jacking it up a bit.

I asked for half-thick top mount spacers from Penske to try in case I need more clearance from UCAs. This was caused by the fact that rears were longer than Penske engineers' safe length limit for clearance. Little did I know that rears were actually fine, but the problem was fronts. In the end, I did not use any spacer whatsoever for the fronts for proper clearance (more on that later).


The rears are now 17" long. 17.25" would make it perfect, since it would drop the preload needed to 9mm or so, but it could also have clearance issues with UCA or axle boot. I think it's OK : )


Rears have almost 1" of space for the shock top's articulation. I decided to use the thinner spacers, since there is plenty of space already.


Even with no spacers, rears would likely have no issue; it almost clears 90 degrees.


The tool I made for remote adjustment of rebound settings.

You Tube

Here it is in action.

These (fronts) look more like 16.5" to me (instead of 16.25"), but well, it worked perfect for my target height. Note the bottom mounts: they allow you to slide the shock a bit.


Decided to use Nord-lock for top mounts to make sure they don't loosen in time.


The axle clearance at full droop. It is enough, and it will be even further away when the car is not on the lift.


Both canisters are in the bumper. LR is shown here.


Plenty of space for the rear top mount's articulation with the thinner spacer.


RR canister.


With the longer shock bodies, I had to remove UCA top bolts to fit the shocks.


I also had to remove all spacers for top mount to clear the UCA. Before doing so, I tested all articulations from 20-90 degrees to make sure the shock body does not interfere with the chassis.


I also had to slide the bottom mounts (which allow quite a bit of play) towards rear of the car to center the UCA for proper clearance.


How it initially looked with +6mm front and +15mm rear preload.


How it looks now.


The bigger gap at the rear will be crucial when I test the 345/35/18s on 18x11 ET 79 wheels, soon.


It's finally all done! I will try to get it aligned ASAP, and then I will start testing out 345s for clearance! I can't wait : )

X25

Project 345: It worked!



I spliced short 1/2" hoses, and covered the remote reservoir hoses at places it touched anything else on the car.


Got the car aligned again with the new suspension. -3 front and -2 rear cambers are about as much as I can do at this height (0.6" drop from stock).


Once home, decided to try the 345s. Checked the inside clearance, first; check! I have ample clearance on all ends, and the 18"x11" wheels with 79mm offset barely clear the upper control arm at this shock height (full droop).


I have 60+mm of gap, about 2.5". The whole suspension movement can't be more than 4" or so, anyways, so I'd highly doubt that I'd ever destroy my fenders. Regardless, I will wait until track testing for the final word (I had no rubbing whatsoever during my street tests).



Here's how it looks with:
315/30/18 Front
345/35/18 Rear



Edit: Just added a how-to:
Stingray how-to: 315 Front / 345 Rear tires for track use

X25

I got to test 345s at the track, today. Looks like it works! Now that the fitment question is answered, I'll source R7 345/35/18s, and wait for the next opportunity for a full-on R7 setup. Well, before that, I will also need to tune these shocks with my base tires (NT01s 315/325).


Just look how crazy optical image stabilization turns the camera one way when the stabilization spring is compressed, and how the camera turns back onto center when the corner is done. It's interesting to say the least : )

flyguy0812

what camera and app are you using to get all that data in your vids?

clarkkent06

The new camera in the above video is a Sony FDR X3000 (it's nice because it has optical image stabilization). Old camera was a GoPro 4 or something.

Data is obtained with RaceChrono Pro (Android app). He uses RaceRender (on PC) to create the video with the data obtained from RaceChrono Pro. But, you could also output a video straight from RaceChrono Pro without needing RaceRender.

X25

Thanks Clark, not much to add, here. The new camera shows more details, is easier to use, generates higher quality output, but most importantly, has optical image stabilization, so the shaking videos are now thing of the past! I'll raise its mounting location, and then it will be all set.

FYI, I'm also recording at 60 fps, so if I end up making something stupid, I'll get to play it better in slow motion : p

village idiot

I really enjoyed a similar tire setup (315/335). Car felt perfectly balanced.

That track- JFC the wall at 0:30 and trees everywhere. I guess we're spoiled down here in Texas.