15" track wheel set up help!!!
 

Track Folks!!

Help me figure out 15" track only set up for my 1983 911sc
Tracks I will be doing - Buttonwillow / Chuckwalla

Tires I'm going for - Hoosier r7 or Toyo RR's

I'm learning that there is no et 23.3 15x8 for the fronts

So: Replica Fuchs:
Front 15x7 23.3 Hoosier R7 225 x 45 x 15
Rear 15x9 10.6 Hoosier R7 275 x 35 x 15
The right option?

Also reason for 15" is to increase my torque ... cheap Ring and Pinion update...


Any help would be much appreciated!!

Dennet

if you have raised spindles in the front, there are issues with 15s clearing on a lowered car. plenty of threads on it. FYI

I have a bumpsteer update in front if that helps - car is lowered lower than euro spec on 17x8 - 225 45 -17 front - 17 x 9 - 255 / 40 17 rear currently - fenders pulled no rubbing on all four

the ball joints can rub on the wheel. jackthemack has a thread about this.

There are 40mm front hubs off a non vented brake 912 (stock is 47mm) that can help fit a stock 15x8 et10.6. They don't have the hub centric ring though which is slightly annoying.

Better option is to get some aftermarket Fuch look wheels with the correct offset.

Crew-

Is the right move to get 15x7 23.3 et for the fronts then??

Depends on how serious you are and power level. I drive a 914 AX car with 205 Hoosiers on 15x7” wheels and used to run the same setup on my 911.

It gets you around the track but it’s easy to overheat them and the smaller diameter tires are easier to lockup under braking. The difference of a 205 on a 7 and a 225 on a 8 isn’t that significant I just might rethink the whole 15” wheel thing if lap times matter and you think you might continue down the track path.

If it’s just a bit of fun, 15in tires are cheaper and it does help the car accelerate but unless limited by class rules or budget on other modifications, the 17in options I think will prove to be faster at the end of a session even if they might be a little slower on a 1 and done flying lap.

I rebuilt my whole car around 18in wheels to run 245/275 tires for the biggest contact patch and thermal heat capacity.

In addition to no 8x15ET23.3 there are no 9x15 ET15, the only 9x15 Fuch is the ET3 for the front of a 930 fendered 911

Ideally you would want 8ET27 and 9.5ET19 for 225/40 and 245/45 or 225/40 & 275/35( you could use 9ET15 as well but it somewhat less than ideal and while picking nits a an 11ET would be preferred for the 275/35 but would also likely cause fitment issues as a 275 on a 9.5 allows only a few mm on either side of the wheel/tire assembly)

Those wheels are going to be expensive

so if on more of a budget 9 ET23.3 and 8 ET10.6 w/ 205/45 & 225/45 isn't going to give up that much if anything over 225/45 & 245/40 on the same wheels due to the extreme reduction of side wall stiffness on less than max width wheel

It's for sure that you're going to get a nice big torque bump from the 15s vs 17s, of course that also means more shifting due to the compressed rev vs speed range

The 911 E Class/ 911 Cup cars are for the most part running Buckley 15X8&9 Wheels with the Hoosiers. The wheels are made by Kaiser, so since Jim Buckley has retired you may have to go directly to Kaiser to purchase new wheels. These wheels are very light and not extremely expensive. There was a used set of 4 wheels for sale here on Pelican recently.

I ran these wheels on my 911 race car and really liked them.

John

Bill - Thanks for this break down

So If I do move with a !5" set up...

Front Replica Fuch 15x7 23.3 et - 225 x 45 x 15
Rear Replica Fuch 15 x 9 10.6 et - 275 x 35 x 15

what's your thoughts

Thanks!!!

John Thanks fo this info Buddy, Really appreciate it - I'm going to look into this suggestion for sure

Dennet

front 7 ET23.3 yes w/ 205/50 oe 225/45
back 8x15 ET10.6 yes w/ 225/50 or 225/45 or 245/40
or back 9x15 ET15 yes

or for custom
front 8x15 ET27 yes w/ 225/45
back 9x15 ET15 yes w/ 245/ 40 or 275/35

the widest wheel for which a tire is spec'd the better
be aware of the effect of f/r stagger on under/over
back 9.5x15 ET19 yes w/ 245/40 or 275/35

Bill

Big Thanks Boss!

Cheers

Dennet