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18x12's 335/30-18

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Hello! Before you call me crazy, its been done. Now I just need to reverse "engineer" (for lack of a better word) how it was done. I think this is an epic win. I know some purist may not like it but you can't make everyone happy.

I autocross my '16 in CAM-C. While 305 Bridgestone RE71's on 19x11's has done well it is time to join the others and hopefully get more grip by going to the BFG 335/30-18 on a 18x12 wheel.

Here is what I know. The stock front brakes won't allow a 18" wheel. You can mount an 18 but you need to bring the caliper in toward the hub. The best part about our brake setup is that the caliper is mounted on the spindle from the outside vs a GT which bolts from the back. If you machine the mounting surface of the spindle, you can bring the caliper in. I was told they were machined about 5/8 of an inch off the spindle.

That is all the details I can glean from the individual. I know they used a different rotor from the pictures. It appears to be a 15" PP rotor. I am unsure if those are a direct replacement or not. From there I am not sure if anything else is needed.

Anyone have any thoughts? I am looking for technical feedback to make this work. I have confirmed the GT350 on 18's is fully operational and running.

I also can obtain the correct wheel offset but from pictures the wheel fits fine and is flush/not poking. Based upon comparison of my 19x11 et52 Apex wheels. I can go to a 18x12 et65 and they will fit. The fronts will need to be spaced approx 1.5" to run square. I will be able to run 18x12 up front due to the offset JRZ shocks which give more clearance.

What am I missing? Any help is greatly appreciated.
 
492
387
DFW, TX
I figured out what you are asking. You are going to run a smaller diameter rotor, down to 14.25" diameter or 15.5" - (2x.625"). For all that bother I would just put a GTPP brake package/spindle on and save your GT350 stuff.
 
You might just want to buy some aftermarket calipers, AP Racing or Brembo for example, that will work with 18" wheels. Once you modify the spindle there is no going back. You can buy new calipers and sell them when you're finished. Good luck.
 

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