Time Attack 58 -- OnGrid @ The Ridge -- Vitour Sonics, new Podium Wheels, Improved Chassis.

Another year of events, another winter big platform push! Coming into the 2026 season my focus was mostly on trying to figure out the rear instability of the car. To quote a pretty talented race car builder "We've never made a car faster by making it harder to drive". For me, having the rear traction limit be a CLIFF instead of a roll off I could play with or even utilize, was holding me back. I also like racing and winning, but I like being alive and not having a grenaded car, so I also spent some time focus on reliability and safety!

Suspension / Chassis Work

For the rear of the car I was thinking my problems were three fold. First, I couldn't soften my rear sway bar so I was missing adjustability. Second, my Delrin bushings were likely binding as they are the maximum, and lastly I wanted to validate my alignment values.

The Rear Sway Bar Situation

So the rear chassis of the car has been a headache ever since I started modifying the car. I put coilovers in, and they contacted the toe arms. So I got those offset, and now they hit the sway bar, so I added 3/8" of spacers and... now they still hit unless I adjust the rear sway bar end links to an absurdly long length

Here you can see that I have a fairly lengthened swaybar end link, and you can see where it has rubbed on the toe rod. I simply can't run it in the soft setting anymore either... so I lost adjustability AND with the end link length I was worried the sway bar wasn't in it's idealy parllel to the platform orientation. Infact I was about 40 degrees past that.

This picture doesn't fully cover it, but using the OEM front swaybar end links gained me approximately 1/16" clearance to the bar at a much reduced overall height than I had previously run... and so while I didn't gain adjustability, I did at least get the swaybar end link length and sway bar orientation into a far more reasonable configuration.

Rear Spherical Lower Control Arms

So it's no secret that the rear lower control arms of the C5 Corvette are known to bind when using Delrin or Poly and running the maximum amount of rear camber the paltform allows for. The solution is always "more money" aka, Spherical control arm bushings.  A full set of built spherical control arm bushings will set you back a small fortune (but are worth it, check out what AMT offers here), but just the rear lower control arms from AMT Motorsports is abit more manageable and apparently can be made available upon request. Couple in a spherical shock mount and new ball joint and you've got pretty much the best rear suspension setup you can get... and when you install it and move it through it's range of travel you fully understand why it's the premier choice for track afficianados!

Unfortunately for me, my AMT camber plates got damaged during a previous effort to get maximum camber out of my C5. This was a major bummer, however... I was able to quickly get some replacement plates made of a heavier duty aluminum thanks to Send Cut Send and some open source designs from Millsy Motorsports. While the Millsy stuff is cheaper, it doesn't have the nice markings and loads of alignment details AMT includes, so if you're looking at this and thinking savings... don't. The AMT stuff is best for DIY home mechanics, the camber plates from Millsy are for DIY experts, or in my case "idiots".

Now with the new rear control arms in and slightly different rear camber plates, it was worth aligning the car. Picture above is the tools I use to do my camber and toe adjustments, the primary one being this DIY alingment kit. Process wise, I lower the car so the control arm lower ball joints of the lower control arms are resting on jack stands, essentially emulating the car at rest instead of at full droop.

What was interesting to me is... while my camber measurements were the same, which tells me nothing changed with the camber plates still at the max, I was toed out a 1/4"! That's going to always add rear instability, and I'm not sure when you'd ever want that... maybe for some really tight autocross? I feel this may have been a major contributor to the rear of the car being unstable. I adjusted this back to 3/4" out as spec corvette suggests and called it a day.

One more consideration or though here is that since I secure my car to the rear of the trailer via the rear of the tire, this could in theory be yanking the car in such a way that it strains the rear suspension towards being toed out? Seems like a stretch (literally) but... I am now debating secure the rear of my car via the rear subframe instead of the wheels.

Here's a picture of the front of the car just for comparison at clearance up here. I've got no issues with clearance up front on my C5!

Lastly... I redid the brakes all around. I replaced all of the rotors and pads and am going into this season fresh!

One annoying lesson I learned though is you cannot bed the brakes if you live traction/stability control on. I've twice now wondered why I couldn't bed the brakes and they emit this mind piercingly shrill screech...and both times I pulled the entire brake system apart, cleaned it, scuffed the rotors with sand paper, cleaned everything... and both times they screech came right back. This time though I noticed the dash warning about stability/traction or whatever... and turned it off. Four hard stops later the screech was gone and never came back. YES I know track pads always make noise. Please be an intelligent enough reader to know noise and screech are two very different things...

New Wheels and Tires

So I picked up a set of Vitour Sonic 100tw tires in 305/35R18. This is a rather abnormal tire for the C5 Corvette, but I am limited to 305 average width in the GT class, and once upon a time I had 305/35R18 tires on my car and really liked the look. As you can see above, these tires are HUGE. Despite being 305's they sat wider than my 315 ECF's. This has to be some sort of specific class cheater tire... and who am I to complain that I benefit form that?

Here they ware mounted on my car. They're the better part of slicks on the outside and super meaty. These also went on 4x new 18x11 Podim Wheels FF6. They look amazing on the car and I'm definitely going to try and get another set here soon!

Fire Suppression

This is one of those mods that adds no peformance improvement, but does add peace of mind. I added a lifeline setup for fire suppression on my C5 Corvette, and it's honestly not a big enough setup to put out a major fire, but it is enough that if there is a fire I'll gain some time to get out of the car. Add in that I also have an automatic overhead nozzle triggered by temperatures and I should be pretty darn safe in the car going forward!

Here you can see the fire suppression routing work our team fabricator Dave aka Groundscore Fabworks did. He made it look like a legit race car in there!

Here's another minor piece of work that I had to do... my K&N air filters were about 3-4 years old and overdue for cleaning... or in my case it was just easier to replace them. Looking clean!

Another minor bit of work is that I have to swap springs out on the rear coilovers right now when moving between my Aero and non-aero setup. When budget allows I'll buy another set of rear coilovers so I can just swap out the coilovers, but since I am just running this setup for the season... eh I'm fine. Later in the year when I maybe run aero again I'll be changing the rear spring rate from 750 to 700 to try and bring some balance back to the rear of the car, though I figure the alignment toe issue was the bigger problem.

How The Track Day Itself Went

Heading out to the track from Portland was a breeze. We stayed at an awesome Airbnb right on the nearby bay that had a lovel view and was very comfortable. Unfortunately, we weren't able to drop our cars off early, but the OnGrid session schedule is pretty darn relaxed so it was easy enough to get there and unload and get the car ready before our sessions.

The car was looking good, but had a terrible THUD THUD HOP under heavy cornering... I attributed it to my taller profile tires rubbing on the car, which was indeed a factor but... I think my diff is also toast and I am in denial about it.

Getting on track I was a bit rusty, but got back into the swing of things pretty quick. Going out in the first session I noticed the tires taking a bit longer to warm up, and there were some different handling characteristics... plus the slightly taller gearing from the taller tires... but by the end of the first session it all really clicked for me and I was able to put down a 1:47.79, setting a new PB and I felt pretty confident secured the GT class win. I also knew there was more in the tires, so I was looking forward to the rest of the day.

Unfortunately, day time temps crept up a bit and my times dropped a bit. Plus tire temperatures climbed significantly. I'll be writing more about them in an article about the Vitour Sonics, but the pressure jump is intense.

Day two was wet, and I was only able to get out for one clean AM session before I stopped going out due to moisture. Unfortunately on that first session there was a large off and tow trucks came out. Normally with seasoned drivers this wouldn't be a big deal, but unfortunately for me a lot of the other drivers lifted to the tune of maybe running 4/10ths out there, which meant I had a bunch of throw away laps... and by the time I was on a crazy good flyer and really cooking to set a better time... I caught up with traffic... and then the next lap I caught up with the tow trucks on the actual track itself.

My best on the second day was a 1:47.82, which was .03 seconds slower than the previous day. I feel pretty safe saying I can run 1:48's now though reliably and sneak into 1:47's if I get a bit extra sendy.

I didn't get out for any of the other sessions. I just didn't feel the need to risk it all. I had secured a win, I'd had fun, the car had held up... and I didn't want to tempt fate on this basically slick 100tw tires.

A 1:47.79 was enough to secure the GT class win... against nobody else. For whatever reason nobody else signed up for the GT class. While a bit of a bummer to get the token win, my time was competitive to the rest of the folks out on track and historically was competitive to the GT class. Hopefully I can convince more Corvette folks to attend in the future!

Lap Times And General Thoughts on Car & Personal Improvements

Previous best: 1:48.89

New Personal best: 147.79

Saturdays best lap:

Sundays Best Lap:

Data Comparison to Previous PB:

So the simple output of max numbers from my Racebox mini I think tell the full story. I was able to pull .2 or so more G accelerating out of turns, and .1G of additionl braking force. Top speed was pretty much the same, the top of 4th gear, but my min speed increase significantly. Speed through Sector 1 was the same but all other sectors showed gains.

Overall I think the improvements to the chassis and alignment combined with the better tire let me play with the full potential of the car that much more and with more confidence so I was able to run over a dozen lap times better than my previous PB.

Where I fancy I need to Focus on to Improve Further:

So there are two areas to improve pretty much any time, the car, and myself. Some people can say all you need to do is yourself... but they must not take as much joy in their cars as I do!

Car wise: I think with the rear differential fixed there's some additional drive earlier in the turn and on my way out with improved stability. I also think as I get a better feel for the tire pressures there's additional gains to be had as well.

Personally: I gotta change up my "heel toe" technique. I currently side foot, and I know I stay covering both the brake and the gas too long, not giving the brake it's full potential. With improved technique I can both carry speed in further AND apply better brake pressure to take full advatange of the tires and the EBC SR series race pads.

While my theoreticals didn't show more than a .08 lap time improvement... I know there's more in the tank, and I was trending towards a better time on day 2 until situational factors interferred.

Fun With Friends

So for this adventure my wife came out, and another friend joined us with his wife. We also ran into a bunch of other familiar faces which was really fun!

My wife got me this really loud and obnoxious and cheesy corvette jacket... which was really fun!

Here's our group posing, with thir dad on the far left side. My wife also has her hairy weiner out. Classic.

Here's the only other C5 corvette at the event. I figured I'd snap a quick photo. Nice fellow and their first track day with the platform. Maybe they'll read the articles here someday and spot themselves!

Oddly enough, there were only 3 corvettes on track all weekend, which was a 180 degree turn from the previous event in NorCal that had 12x C8 Corvettes and many other Corvettes in general.