CT4V -BW Track "Capable" versus Track "Optimized"

[jodakid69]

Folks,

The CT4V-BW is "Track Capable" from the factory. I am looking to run around 20 track days a year. Therefore, I am looking to Optimize the CT4V-BW. The core of my questions are based on the fact that Cadillac likely optimized the tire and wheel selection for the CT4V-BW based on the typical consumer use for the vehicle and price point of the vehicle. They might also what to push people towards the CT5V. Therefore, making the car "better" as the track versus those other items drove the wheel/tire selection.

I have already addressed brake system optimization by migrating the brake pads to EBC SR-11 track brake pads and changing the brake fluid to Castrol SRF. Now I am looking at wheels and tires for the track. I admit that I am an absolute novice in this area. So my questions might be stupid and obvious to those people with more experience in car setup:

(1) Can I go any wider on the fronts?
The Tire Rack website shows 9" and 9.5" Wheels. Assume the 9s are for the fronts and 9.5 for rear?

(2) If I do go wider in the front, can I go with a square setup, since I am currently eating up front left tires it would be nice to swap the front left tire with the right front and the rears.
9.5 Wheels all around?

(3) Tire Rack website shows availability for 18" and 19" wheels. It is possible to go with 19" tires on the CT4V-BW? Obviously, lighter wheels are better on track.
If 19" wheels are possible why go that route? The wheels are more expensive, the tires are more expensive, and the combo is heavier. However, there are many more tire options at 19". As an example "Extreme Summer Tires" are not shown as being available for the CT4V-BW on the Tire Rack website.

(4) Tire ratio - if you go wider, do you need to increase the height?

(5) My thinking is 9.5 wheels in front and rear with 275/35 OR do you go with 9.5 wheels in the front and 10" in the back.

Final point - In the front wheel well there is a small Carbon Fiber piece and an abs piece. Can we get a vendor to build a full arc in Carbon Fiber or ABS? If we can get such a fender extender in Carbon Fiber, is a wider tire we possible then?

What about in the rear wheel well?

 

[Jim2000]

For wider wheels, it is likely you will need to go with a custom wheel manufacturer who can give you specific offsets and widths that you want. They possibly can be lighter also. These will be expensive, so don't be surprised to spend over $1,000 per wheel.

 

[RDATLTE]

"Rolling the Fenders" might give you a bit more room for more tire. I'd opt for something of this nature vs the baseball bat method with this car.

https://www.ecstuning.com/b-schwaben-parts/schwaben-deluxe-fender-lip-roller-kit/024962sch02akt/?gclid=CjwKCAjwtuOlBhBREiwA7agf1tBam3gyjhkgrrc99QMd0Co2har8eOFDGuNcliC21jw1v3Oat8HrLhoC9aQQAvD_BwE

 

[Head Hunter]

Perhaps @Terrance Sig can weigh in here, but I think an issue you may have deviating from stock size tires will be your ABS system and all of technology integrated into your traciton/handling systems.

To optimize the system, I would think having a second set of wheels/tires purely for the track that are forged aluminum (lighter than stock, cheaper than magnesium) with a road course specific tire (Hoosier R7 for example) will get you the best results.

I like where your head is at and look forward to seeing the discussion

 

[rdollie]

Unless you're planning to move to a dedicated R-compound track-only tire, I'd stay with the stock sized PS4s. They're bespoke for the Blackwing being made mostly (61% as I recall) of the R-compound from the Cup 2 tire. It's going to be hard to find a better street tire for the track and you can get the bespoke Michelins at places like Costco and save a bit over most other options. That tire with a lightweight wheel (too bad the magnesium wheels never materialized) would be pretty good (I track the stock tire on a heavier 5 BW with no issues so far other than expected wear.)

 

[poor-sha]

I'm also of the mind that you're going to have a hard time finding a better tire than the TPC spec PS4S unless you go with a true R Comp. The 4BW that John Heinricy is campaigning this year is running 18x10 and 18x11 wheels wearing Hoosier 285 and 285 tires. He's supposed to be at VIR this weekend so I'll try to get a look at the car, but he did mention needing to modify the wheel well to get them to fit.

Whatever you do, make sure the front to rear diameter ratio is the same as stock, and ideally I'd shoot for the same diameters as stock, otherwise ABS and PTM will not behave as expected.

The only other thing I would consider is replacing the brakes with an AP Racing BBK. You'll have more options in pads (likely cheaper), replaceable rotor rings, and easier pad and rotor replacement. On top of that you'll save some unsprung weight.

 

[PL69]

I wouldn't get too hung up on trying to run larger tires/wheels. At my local track I did PB of 1,55.5 in my 2023 M3 running a square 295 set of Continental Extreme Force on lightweight forged wheels and just did 1,56 with the 4BW on my first outing on OEM PS4S.

Endurance tires like Hankook RS4 stock size will go a long way in terms of durability and cost per lap. You can also have them flipped(remounted inside out) to even the wear and prolonge there life.

Many track veterans I talked to told me they were faster on a staggered setup vs a square setup. Keep in mind GM engineering teams work with budgets in the millions of $. My gut feeling tells me the car can take grippier tires and they chose ps4s for the all-round aspect.

 

[strohw]

The only other thing I would consider is replacing the brakes with an AP Racing BBK. You'll have more options in pads (likely cheaper), replaceable rotor rings, and easier pad and rotor replacement. On top of that you'll save some unsprung weight.

I think you'd struggle to find a reason to use the BBK on this car unless you made it track only. Between the 4 using Camaro pads which already have a huge selection and the cost of the AP rings only being about $200 less for a set than the full OEM rotors, it doesn't seem to make much sense.

 

[PL69]

I think you'd struggle to find a reason to use the BBK on this car unless you made it track only. Between the 4 using Camaro pads which already have a huge selection and the cost of the AP rings only being about $200 less for a set than the full OEM rotors, it doesn't seem to make much sense.

I have to agree, Essex have some really good marketing, I ran a full kit (baught used) on my M2 and my friend naughty a new kit for is M2 used and he took a huge loss when he sold it and we concluded it wasn't really worth it on a car that you could already swap pads from the top.

It makes more sens in a competition environment but for track days only unless your car comes with very poor brakes don't bother.

 

[Head Hunter]

@jodakid69 i was going to bring these with me to VIR to give you, but since I won’t be making it, if you message me your address I’ll ship it to you.

 

[poor-sha]

I was just talking to Heinricy about brake pads and he's running DTC80 front and DTC70 rear with the stock brakes on the 4BW. He also said the Pagid RS29S were good, but couldn't remember what compound they ran in the rear.

 

[PL69]

Seems like the article about is racing venture with the 4BW was giving the impression they developed something for him but your saying he probably just uses of the shelf pads.

Heinricy and Hawk Performance have worked closely to find and make a brake pad that mimics the friction curve of the stock pads, while adding enough shelf life to complete the race.

 

[poor-sha]

Seems like the article about is racing venture with the 4BW was giving the impression they developed something for him but your saying he probably just uses of the shelf pads.

Heinricy and Hawk Performance have worked closely to find and make a brake pad that mimics the friction curve of the stock pads, while adding enough shelf life to complete the race.

I’m not sure what article that’s from, but that’s what he told me.