How I fit 305 fronts and 325 rear tires

[RSXDC5]

Originally Posted by MagicF8x

This is a great post

Do you think a 315/30/19’ on a 10.5 et37 will work in the rear , I am lowered on macht schnell springs.

Thx! I would stick to a max of 305/30/19 on a 10.5in wide wheel. 315/30/19 max on a 11in wheel. 325/30/19 max on an 11.5in wheel.

[Gaz_gaz]

Hey.

Is there any chance you can reach out to me by email or WhatsApp or something for a bit of a chat about running the wide rims and tyres please?

Originally Posted by RSXDC5

I've been getting a lot of interest in how I fit my 305/30/19 fronts and 325/30/19 rears...Here is what you need in order to achieve this fitment:

Fronts: 305/30/19
19x10.5 +20 (I add in a 5mm spacer for an effective +15 offset on track)
Get a heatgun, via the heating, make minor modifications to the fender liner to push it back/away from from the tire in a few spots for clearance
-3.1 to -3.2 camber
If on coilovers, you need a 5in front spring (helper spring optional) so the spring assembly sits above the front tires (vs adjacent to it)
Don't slam the car
KW coilovers may not work with their reduced inner clearance

Rears: 325/30/19
19x11.5 +44 (+45 will also work)
No fender modifications necessary
-2.1 camber, don't go crazy here, around -2.1 is the sweetspot
Don't slam the car (wont be needed with a 325)

Comments:
A 305 tire on a 10.5in front wheel is fine if you run a tire with a stiff sidewall.
I use 0 toe up front and 0.07 toe in PER SIDE on the rear.
Soooooo much mechanical grip on track.
The 325 rear allows for a higher (usable) power output on track/street
You'll need custom spec'd wheels in my specs above, Signature/BC Forged was my pick.

Enjoy!

[M3SQRD]

Originally Posted by RSXDC5

Thx! I would stick to a max of 305/30/19 on a 10.5in wide wheel. 315/30/19 max on a 11in wheel. 325/30/19 max on an 11.5in wheel.

Typically, to run proper support, a 295 max on a 10.5” wide wheel, 305 max on an 11” wide wheel, 315 max on a 11.5” wide wheel and a 325 max on a 12” wide wheel. The most commonly used track setup on the f8x is 295 square on 10.5” square wheels. The section widths become too wide, especially for a tire that runs wide for its given tire width, for the rim widths which actually reduces grip, not increasing grip. There are plenty of tire widths vs. wheel widths test articles out there and the conclusions are always the same - a narrower tire on a wider wheel outperforms a wider tire on a narrower wheel. One test example:

https://grassrootsmotorsports.com/ar...always-better/

[RSXDC5]

Originally Posted by M3SQRD

Typically, to run proper support, a 295 max on a 10.5” wide wheel, 305 max on an 11” wide wheel, 315 max on a 11.5” wide wheel and a 325 max on a 12” wide wheel. The most commonly used track setup on the f8x is 295 square on 10.5” square wheels. The section widths become too wide, especially for a tire that runs wide for its given tire width, for the rim widths which actually reduces grip, not increasing grip. There are plenty of tire widths vs. wheel widths test articles out there and the conclusions are always the same - a narrower tire on a wider wheel outperforms a wider tire on a narrower wheel. One test example:

https://grassrootsmotorsports.com/ar...always-better/

Oh I’m more than aware that fitment was on the limit. The 305 tire in question (Nankang ar-1) ran narrow like a 295.

I now run a 295/315 stagger on the 10.5/11.5 wheels and am quite happy.

[M3SQRD]

Originally Posted by RSXDC5

Oh I’m more than aware that fitment was on the limit. The 305 tire in question (Nankang ar-1) ran narrow like a 295.

I now run a 295/315 stagger on the 10.5/11.5 wheels and am quite happy.

Sounds good!

What’s the offset on your 11.5” wide wheel? IIRC, it’s 44 mm?