[Gmark958]

This is a hypothetical, but I thought I'd ask since Goodyear has their Stock Car tires listed for a third of regular 18x10 slicks ($160 for the short track tire D code 2560 vs. $450 for a michelin s8m/hoosier a7/pirelli dh18x10 slick), but how would one go about converting all four tires to the 28/10.5r15 wheel and tire combos currently used by Nascar? I'd imagine that the addition of an extra four inches of tire diameter would present a whole host of challenges in terms of clearance. I'm not too smart when it comes to building cars, I like the engineering challenges that is provides and this seemed like a good one. My first thought is that the additional height would not allow for the tires, so the wheel base would have to be extended from 108" to around 115" or longer. My question is, would the extremely high initial cost of doing the work required to essentially redesign the front and rear ends be worth it in the long run?

I know it's a dumb idea, but I am a creative individual with a lot of free time.

[feuer]

So, redesign the car to fit tires that are currently on sale? You must have free time indeed….
To fit 15” will need custom wheels too in order to clear the brakes. Or custom brakes to fit under 15” wheels. Totally not worth it.

[Gmark958]

Originally Posted by feuer

So, redesign the car to fit tires that are currently on sale? You must have free time indeedÂ….
To fit 15” will need custom wheels too in order to clear the brakes. Or custom brakes to fit under 15” wheels. Totally not worth it.

Wilwood and AP racing both sell brake rotors and calipers that will allow for a 15" wheels along with interchangeable rotor hats that will fit a 5x120 bolt pattern so nothing custom will be required, just a lot of massaging or complete removal of the fender liners (my car doesn't have front fender liners anyway and the rear can be tubed pretty easily).

https://www.***********.com/showthre...el-tire-Set-up

This guy managed to get a 28/10r17 in the back and it looks like it's in there pretty tight, which is why I wanted to possibly move the subframe to increase the wheel base, to allow a couple of inches extra to fit. Granted his is a 17" wheel and I wanted to do the 15" conversion.

The whole reason I even asked is because of cost. 15" wheels are much cheaper to replace ($540 for all four) than 18" wheels in the inevitable incident that I crash or otherwise get the car damaged. The wheels (Goodyear D code 2560) retail for $160 VS. the $450 for most 18x10 slicks. So to replace all four tires and wheels would be $640 plus the $540 for everything as opposed to the 18" set ups that dominate the platform.

Numbers for reference:
15" set up
Wheels -https://www.jegs.com/i/Aero-Wheels/261/50-104710/10002/-1 - $134.99
Tires - Goodyear D code 2560 - $160 - https://www.carrollshelbyent.com/sto...x-100-15-a400/

18" set ups
Wheels - APEX ARC-8 - $379 - https://www.apexraceparts.com/store/...c-8-wheel.html
- TA16 - $499.99 - https://www.bimmerworld.com/Wheels-T...e-Wheel_3.html
Tires - Michelin S8M - $457 - https://www.subesports.com/michelin%...-s8m/mic-21160
- Hoosier A7 - $446 - https://trackdaytire.com/product/hoo...dial-a7-tires/
- Pirreli DH - various - https://sascosports.com/tires_search...cturer=Pirelli

[feuer]

Originally Posted by Gmark958

Wilwood and AP racing both sell brake rotors and calipers that will allow for a 15" wheels along with interchangeable rotor hats that will fit a 5x120 bolt pattern so nothing custom will be required, just a lot of massaging or complete removal of the fender liners (my car doesn't have front fender liners anyway and the rear can be tubed pretty easily).
Don’t know why it did the star thing for the thread, here’s a couple of pictures from it.

Rear has been done. That’s nothing new. People that grab these cars have been doing it for years. There are companies that even sell you complete kit. You can even do it with all bmw parts but will loose parking brake. Front is something else. Track is much wider. You can’t move the brakes more inboard to fit smaller 15” rim. At least not yo my knowledge.

[Gmark958]

Yeah, after I found that thread for the drag set up I was a little more at ease. I'd imagine getting 15" tires in the front wouldn't be anymore difficult, just some brakes. However, the front would be a bit more problematic. Not vertically, but horizontally. The added 4" of height would not only run into (or at least very near to) the fire wall and prevent any sort of turning due to the width. The only solution I can see to that would be to move the front subframe forward a couple inches to gain the clearance needed to effectively turn the wheels in the front, maybe add a couple inches of width via increased offset to push the wheels out some as well. Forgive me if this sounds crazy. I'm currently going on forty eight hours with no sleep so my mind is not where it usually is. I might actually see the absolute absurdity of this proposal as a result. This whole idea started because I wanted to do a true tube chassis for my car because I'm an idiot. Then I started looking at tires and got around to researching different brands, ultimately bringing me around to the Goodyear Eagles and even the actual NASCAR tires are still almost $100 cheaper than most 18x10 slicks per tire. So I did some googling and I wasn't able to find anyone that ran those tires in a road race set up car and all the ones I did see were for drag cars.

[colorado.e9x]

People run 15" drag packs with 325 rear brakes all the time

Edit: have yet to see anyone with less than 16" wheels up front

[Gmark958]

Originally Posted by colorado.e9x

People run 15" drag packs with 325 rear brakes all the time

Edit: have yet to see anyone with less than 16" wheels up front

Then if I go that route it'll be a first. Ultimately, I think I'll go that route anyway. I'm not the type of person to shy away from the challenge. As for the brakes, I have the AP racing part numbers for the brake rotors and calipers that NASCAR uses on their cars.

[Gmark958]

How much would the fenders would one need to remove to gain the clearance required to use a tire that tall in a road course/hill climb application? My thought here is probably quite a bit. The added four inches of diameter would absolutely rub on the fenders (both front and rear) under a hard corner.

[EDT]

I told myself I wouldn't enter into this nonsense, but seriously, with all the changes that would be required to run massive, soft racing slicks on one of our cars, you would have a much better start just buying an old Nascar road course car or symmetrical frame modified. Stretching wheelbases, running mega dollar brake setups, etc is ridiculous when all this is coming from the basis of saving a couple hundred dollars in tires for a car that will never see any actual competition due to not fitting into any rulesets. What is the desire? If, somehow, you do run through the hundreds of tires that would be needed to make this sound feasible and are absolutely dead set on using an e90/e92, why not just run takeoffs from a series that actually uses tires that fit these cars, like the GTLM, GTD, and M2 CS guys? Takeoffs are fine to burn up, and again, it's not like you're competing.

[Gmark958]

Originally Posted by EDT

I told myself I wouldn't enter into this nonsense, but seriously, with all the changes that would be required to run massive, soft racing slicks on one of our cars, you would have a much better start just buying an old Nascar road course car or symmetrical frame modified. Stretching wheelbases, running mega dollar brake setups, etc is ridiculous when all this is coming from the basis of saving a couple hundred dollars in tires for a car that will never see any actual competition due to not fitting into any rulesets. What is the desire? If, somehow, you do run through the hundreds of tires that would be needed to make this sound feasible and are absolutely dead set on using an e90/e92, why not just run takeoffs from a series that actually uses tires that fit these cars, like the GTLM, GTD, and M2 CS guys? Takeoffs are fine to burn up, and again, it's not like you're competing.

I agree that this is complete and utter nonsense and has zero practicality in any sort of application, BUT I am an idiot.