TheDarkKnight

I posted a thread about AFS Black Bullitt wheels a while back and think I'm gonna pull the trigger now...

They have 18x9 fronts and 18x10.5 rears available which is what I'd like to purchase and they have them available with Goodyear F1 Supercar tires as well.

Here's my question. The tires size they come with are as follows:

Front: 255/45/18
Rear: 285/40/18

Can someone please explain to me why the tire sidewall height differs from front to rear?

My goal is to have some meaty looking tires for a more aggressive muscle car approach. Are these the tire dimensions I'm looking for? Or what would you guys recommend?

Also how will this affect my speedometer and mileage readings and how can I adjust that in order for them to remain constant to the current reading?

2k7gtcs

These sizes of tires most closely resemble the stock tire diameter, if the stock tire is a 235/50/18. Check out the link below its a tire size calculator you plug in tire size and it gives info such as diamater and sidewall actual height.

To see the numbers for your existing tires plug in those numbers and compare with what you want

http://www.discounttire.com/dtcs/infoTireMath.dos

255 is width across tire sideall to sidewall in mm
45 is tire side wall height as a ratio to width, height would be 45% of 255 mm=114.75mm
18 of course is wheel size

Hope this helps.

TheDarkKnight

Thanks! That's very helpful and I am so in love with your car, you have no idea.

From what I understand having the smaller sidewall height in the rear is to keep the dimensions as close to possible to stock.

Would I have to re-calibrate my speedometer after the purchase in order not to screw up my mileage?

2k7gtcs

Depends. My goal was to keep the overall diameter and therfore revolutions per mile similar + or - a mph or 2, but since I have an XCal 2 Tuner I had Brent include the corrected tire size in my tune, or from what I understand it can be user set in the Xcal 2 under user parameters? or something like that. A 285/40/18 is very close to a 235/50/18 that came on my car though.

2k7gtcs

Thanks for the compliment, it means alot when someone validates what you've done. Sometimes I just hope I haven't done too much, but I look at it and right now it fits me perfectly. All I want now is more power.

TheDarkKnight

Thanks again for your help, it's really appreciated, I guess I'll need to a tuner to fix the revolution per mile difference.

I look at your car, and it pretty much expresses everything I'd want out of mine as well.

Very nicely done, the compliments are well deserved.

2k7gtcs

Thank you. They are much appreciated.

Stoenr

I went with 18x9 18x10
255/45/18
285/40/18
F1 Supercars
no speedo calibration required.

Looks good I think.

Roush rear springs coming out and pro kit/Dspecs going in shortly

TheDarkKnight

Those are some nice pictures, thanks for sharing!

I just got back home from purchasing my wheels and tires. I too ended up with Supercars in the exact same sizing as yourself.

Here's another question. After a wheel & tire change, is an alignment required? Or can we just go ahead and mount them without any issues?

Thanks!

Stoenr

No issue with alignment change.
Just going to be a pain in the butt getting alignment heads on the wheels without scratching them when I do align it after suspension mods later this month. Darn rim flange protectors on the tires hug the lip of the wheel.

2k7gtcs

Make sure you post pics when you're done. We want to see results.

TheDarkKnight

Definitely! I plan on getting them mounted on sometime this morning!

TheDarkKnight

Please excuse the phone pictures, there will be good quality pictures to come, but here's a little something to give you an idea of what I went with.

Thank you all for your help and advice.

Stoenr

Hey them tires look familiar! Looks good man!

TheDarkKnight

Thanks!

2k7gtcs

Allright. Looks really good. You teaser.

2kanchoo

10.5" rim you should throw some 305 or 315 street slicks on teh back.. big fatties.........











wait that didn't sound right...

TheDarkKnight

Maybe on the next set of tires. I need an intake/tune/exhaust to make up for the added tires to keep them wheels turning!

Stoenr

Id love to toss a 305 or 315 on there some day. Its all about matching tires tho on the fronts to back.
Ill look at the availability on 305's when im sober.

TheDarkKnight

You're my hero. Lol.