Changes to GT350 that help track day performance

[Frank.Herbst]

I'm new to the the 6G site and a relatively new GT350 owner. My son and I bought a 2017 GT350 about 9 months ago and took it out to four track days this year that were put on by the Denver Shelby club. Years ago when we bought a car changing things was a given and I guess I'm still thinking that way with the new Shelby. Big difference now is the new Shelby seems to be engineered to consider all aspects of the car to the point I'm not sure if changing things might actually slow it down on the track.
One area I'm looking at is putting on lighter wheels. It looks like the wheels used on the FP350S might be available and they are considerably lighter than my stock wheels. Has anyone recorded their lap times and then made upgrades to a stock GT350 and seen improved performance. Any information would be appreciated.

Thanks,
Frank

[email protected]
Denver, CO

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[firestarter2]

Biggest bang for the buck is driver and tires.

 

[Stuntman]

Agreed on the driver.

Lighter wheels aren't always better .especially super light aluminum wheels. A good read:

https://motoiq.com/tested-carbon-revolution-carbon-fiber-wheels/

 

[torque124]

While I agree with driver and tires, I have to say that camber plates could be very useful... if the track is clockwise, your left front tire will be all but destroyed on the outside after a couple of track days (depends on how fast you go obviously).

 

[honeybadger]

Hi Frank -

Welcome to the group! Think your assessment of the car is spot on.

I've tinkered a fair amount with my car (there's probably other stuff I've forgotten):

Chassis:

• APR GT250 rear wing
• APR GT350 front splitter
• MGW shifter
• Solid bushings and spherical bearings in the IRS
• FP lowering springs
• FP sway bars
• Full tilt boogie adjustable end links
• MM camber plates
• BMR camber bolts

Wheels/tires:

• Signature wheels SV502s in a squared 19x11 setup (20.4 lbs)
• Michelin Sport Cup 2s
• ARP wheel studs

Brakes:

• Stainless steel brake lines
• Raybestos ST43 pads
• AND Caliperfexion caliper studs

Safety:

• Watson 4-pt roll bar
• Sparco Circuit II halo seat
• OMP 6-pt harness

And I'll tell you only (2) things have directly improved lap times (outside of the most important, driver mod) - tires and and safety stuff.

Tires will improve lap times very quickly because they have no performance downsides (improve grip, but don't cause more problems like adding power can). But they do hide mistakes and can make you driving a bit lazy.

But seriously, safety. If you're in a fully bolted-down, fully-strapped racing seat, you'll spend less energy keeping yourself from flying around. This gives you better concentration, more control, and more confidence. Not to mention it's much, much safer. These cars are fast, don't skimp on safety .

All that said, all the other mods have helped my lap times tremendously, but they have helped it more with feel and chassis communication, than pure added performance. You throw a big wing on a novice/intermediate driver's car, I'd venture to say their lap times won't improve much. Only really makes a difference when you're at the edge IMHO. Plus, it ruins your entire setup. Ask me how I know

 

[Epiphany]

No caliper studs on that car? Hmm...

 

[honeybadger]

Edited!

 

[LAPTIMZ]

I hate speaking in generalities however if your asking these types of question then I'm assuming your experience level is what HB was suggesting. In that case I would stick with an alignment and HANS Hybrid S (which is the only HANS device effective with OEM 3 point). I know this is a very lame and boring answer however there is a reason. This is a FAST and capable car out of the box. People new to the platform and road racing in general need to learn what the platform likes and dislikes, how it turns, where the weight needs to be, what to do when your contact patch expires etc etc. Without these skills, moving up to a damn near R comp street tires is unadvised and will eventually prove to be dangerous. I see too many heros running in advanced group with sticky tires and ZERO cornering ability outside the level of the grip their tires provide (while they are 3 feet off the apex) and parking it in corners just to drag down the straights.....please don't be that guy. Your car in stock form on MPSS tires will track down 90% of the field your driving in at a DE once you learn how to capably drive it. Save your money, learn the chassis, purchase SEAT TIME and get a good alignment so you can extend the longevity out of the most expensive consumable this car uses.....tires. I would suggest starting with some camber plates or bolt to yield the specs suggested by the FP manual as a starting point. Then let your skill level and driving style dictate where to make adjustments from there.

 

[Frank.Herbst]

All.
Thanks for the reply's. Maybe I should add a little more info because several good responses were related to driver experience. I raced stock cars for 10 years and had good results for a low dollar effort including a track championship. That being said I know one of the big areas is learning what you can do to make handling improvements. So my questions was mostly answered by the comments on tires and camber.
For you guys that have not raced stock cars on ovals it's much easier than the road coarse because of the obvious, so many more areas to tune the suspension to that you end up making compromises for the best over all lap time. I remember hearing crew chiefs say the setup for a road coarse was usually driven by looking where you can makeup the most time and then doing your best on the other sections.

honeybadger,
Any chance you have an example of a lap time before and after changing to the lighter wheels?

Thank you all.

 

[honeybadger]

HI Frank,

Unfortunately I don't. To be honest, I'm not sure lighter wheels would directly result in faster lap times. In my experience, they feel much better, but not sure the improvement is easily measurable without a super consistent driver in a test scenario. However, a set of good fully forged, lightweight wheels will be stronger and have better caliper clearance. I'd still recommend them even without the measurable proof that they're faster.

Since you're an experienced driver with race experience, I'd considering putting solid bushings in the rear end of your car. I think that'll give you a big upgrade in feel that will result in a better track experience.Stiffer springs and sways will also make a big difference when you setup up to more grippy tires.

 

[nastang87xx]

Seat time seat time seat time as with what everyone else said. Driving the GT350 on the street is deceptive because it truly is a case where the performance is hidden until you hit the track and then it becomes incredibly compelling, if not even scary at how much of a monster this car is in all aspects of dynamics.

The 350 is kinda high strung and going even a touch too far with modifications can often punish you rather than benefit. Honeybadger is a track rat so he's gone the full beans but for good reason. If you indeed have some track experience and if you run say Group 2 on an HPDE get caster camber plates and the BMR cradle lockout kit Level 2 or Steeda subframe braces (both effectively do the same thing). That'll save your front tires and get your rear subframe under control and honestly that's about it for starters. I have a BMR front sway bar and I did that for autocross and put it on full stiff. For that application, it was a great move. But on track, it's TOO stiff. I back it off to full soft considering my driving skill.

A lot of people like to give the GT350 a hard time saying it's "the slowest 500+ horsepower car ever made." Clearly those knobs have never been in the driver's seat where the card truly belongs.

 

[nastang87xx]

HI Frank,

Unfortunately I don't. To be honest, I'm not sure lighter wheels would directly result in faster lap times. In my experience, they feel much better, but not sure the improvement is easily measurable without a super consistent driver in a test scenario. However, a set of good fully forged, lightweight wheels will be stronger and have better caliper clearance. I'd still recommend them even without the measurable proof that they're faster.

Being able to swap from street to track setup is nice too. Worth it just for that reason so you're not killing your street tires. Also as far as saving brakes go, I highly doubt we're getting anything much from lighter wheels. I bet in a perfectly controlled environment and tire for tire, run for run, a set of 6G's or Forgestars would help the car stop better within margins of error. It's still a 3760lb car.

 

[MikeR397]

I was goijg to get camber plates but didn’t see any Black Friday deals and didn’t realize they significantly pita installation required removing struts ect. I have simply rotated front tires left to right (rears too) after 2 or 3 track days and this evened out the outside wear on driver side so both fronts chorded at the same time with a simple fast swap. Is there much other benefit to getting camber plates on the front? I have heard quicker turn in but trying to get feedback what is actually noticeable vs helping the outside wear on driver front tire be more balanced?

 

[honeybadger]

I was goijg to get camber plates but didn’t see any Black Friday deals and didn’t realize they significantly pita installation required removing struts ect. I have simply rotated front tires left to right (rears too) after 2 or 3 track days and this evened out the outside wear on driver side so both fronts chorded at the same time with a simple fast swap. Is there much other benefit to getting camber plates on the front? I have heard quicker turn in but trying to get feedback what is actually noticeable vs helping the outside wear on driver front tire be more balanced?

The biggest ROI on camber plates is going to be better wear. If you're pushing hard, they're an absolutely necessity unless you want to chunk your fronts after 2-3 days.

Turn-in is most definitely improved and it's a tangible benefit IMHO if you're pushing hard enough. These cars LOVE camber.

 

[Hack]

But seriously, safety. If you're in a fully bolted-down, fully-strapped racing seat, you'll spend less energy keeping yourself from flying around. This gives you better concentration, more control, and more confidence. Not to mention it's much, much safer. These cars are fast, don't skimp on safety .

I don't think this item can be understated. A GT350 will generate a lot of grip. It's a lot more difficult to modulate the brakes and throttle (much less steering) when you are working hard to keep from being thrown around in the car. You will get a lot more out of the car with at least a good harness pulled super tightly so that you can relax and focus on being smooth and accurate with your inputs. This is especially true towards the end of a 15-20 minute session or towards the end of the day after you've had a number of sessions on track.

I don't think a racing seat is absolutely necessary (at least it isn't for me with the stock Pilot SS tires), but IMO a harness is. I can really relax in my technology pack seats with the harness pulled tight. I remember at the GT350 Track Attack I had the same issue (being thrown around) in the track pack seats until I cranked on the harness and got it super tight. Shroth makes a harness that you can use with the factory seats.

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